Crystallization of probucol from solution and the glassy state.

PubMed

Kawakami, Kohsaku; Ohba, Chie

2017-01-30

Crystallization of probucol (PBL) from both solution and glassy solid state was investigated. In the crystallization study from solution, six solvents and three methods, i.e., evaporation, addition of a poor solvent, and cooling on ice, were used to obtain various crystal forms. In addition to common two crystal forms (forms I and II), two further forms (forms III and cyclohexane-solvate) were found in this study, and their thermodynamic relationships were determined. Forms I and II are likely to be enantiotropically related with thermodynamic transition temperature below 5°C. Isothermal crystallization studies revealed that PBL glass initially crystallized into form III between 25 and 50°C, and then transformed to form I. The isothermal crystallization appears to be a powerful option to find uncommon crystal forms. The crystallization of PBL was identified to be pressure controlled, thus the physical stability of PBL glass is higher than that of typical compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Sorption and desorption studies of a reactive azo dye on effective disposal of redundant material.

PubMed

Çelekli, Abuzer; Bozkurt, Hüseyin

2013-07-01

The effective disposal of redundant elephant dung (ED) is important for environmental protection and utilization of resource. The aim of this study was to remove a toxic-azo dye, Reactive Red (RR) 120, using this relatively cheap material as a new adsorbent. The FTIR-ATR spectra of ED powders before and after the sorption of RR 120 and zero point charge (pHzpc) of ED were determined. The sorption capacity of ED for removing of RR 120 were carried out as functions of particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. Sorption isotherm, kinetic, activation energy, thermodynamic, and desorption parameters of RR 120 on ED were studied. The sorption process was found to be dependent on particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. FTIR-ATR spectroscopy indicated that amine and amide groups have significant role on the sorption of RR 120 on ED. The pHzpc of ED was found to be 7.3. Sorption kinetic of RR 120 on ED was well described by sigmoidal Logistic model. The Langmuir isotherm was well fitted to the equilibrium data. The maximum sorption capacity was 95.71 mg g(-1). The sorption of RR 120 on ED was mainly physical and exothermic according to results of D-R isotherm, Arrhenius equation, thermodynamic, and desorption studies. The thermodynamic parameters showed that this process was feasible and spontaneous. This study showed that ED as a low-cost adsorbent had a great potential for the removal of RR 120 as an alternative eco-friendly process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaczmarski, Krzysztof; Guiochon, Georges A

The adsorption isotherms of selected compounds are our main source of information on the mechanisms of adsorption processes. Thus, the selection of the methods used to determine adsorption isotherm data and to evaluate the errors made is critical. Three chromatographic methods were evaluated, frontal analysis (FA), frontal analysis by characteristic point (FACP), and the pulse or perturbation method (PM), and their accuracies were compared. Using the equilibrium-dispersive (ED) model of chromatography, breakthrough curves of single components were generated corresponding to three different adsorption isotherm models: the Langmuir, the bi-Langmuir, and the Moreau isotherms. For each breakthrough curve, the best conventionalmore » procedures of each method (FA, FACP, PM) were used to calculate the corresponding data point, using typical values of the parameters of each isotherm model, for four different values of the column efficiency (N = 500, 1000, 2000, and 10,000). Then, the data points were fitted to each isotherm model and the corresponding isotherm parameters were compared to those of the initial isotherm model. When isotherm data are derived with a chromatographic method, they may suffer from two types of errors: (1) the errors made in deriving the experimental data points from the chromatographic records; (2) the errors made in selecting an incorrect isotherm model and fitting to it the experimental data. Both errors decrease significantly with increasing column efficiency with FA and FACP, but not with PM.« less

Equilibrium, kinetic and thermodynamic studies for adsorption of BTEX onto Ordered Mesoporous Carbon (OMC).

PubMed

Konggidinata, Mas Iwan; Chao, Bing; Lian, Qiyu; Subramaniam, Ramalingam; Zappi, Mark; Gang, Daniel Dianchen

2017-08-15

Chemical and petrochemical industries produce substantial amounts of wastewater everyday. This wastewater contains organic pollutants such as benzene, toluene, ethylbenzene and xylenes (BTEX) that are toxic to human and aquatic life. Ordered Mesoporous Carbon (OMC), the adsorbent that possesses the characteristics of an ideal adsorbent was investigated to understand its properties and suitability for BTEX removal. Adsorption isotherms, adsorption kinetics, the effects of initial BTEX concentrations and temperatures on the adsorption process were studied. The OMCs were characterized using surface area and pore size analyzer, transmission electron microscopy (TEM), elemental analysis, thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). The results suggested that the Langmuir Isotherm and Pseudo-Second-Order Models described the experimental data well. The thermodynamic parameters, Gibbs free energy (ΔG°), the enthalpy change (ΔH°) and the entropy change (ΔS°) of adsorption indicated that the adsorption processes were physical, endothermic, and spontaneous. In addition, OMC had 27% higher overall adsorption capacities compared to granular activated carbon (GAC). Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of acid blue 062 on aqueous solution using calcinated colemanite ore waste.

PubMed

Atar, Necip; Olgun, Asim

2007-07-19

Colemanite ore waste (CW) has been employed as adsorbent for the removal of acid blue 062 anionic dye (AB 062) from aqueous solution. The adsorption of AB 062 onto CW was examined with respect to contact time, calcination temperature, particle size, pH, adsorbent dosage and temperature. The physical and chemical properties of the CW, such as particle sizes and calcinations temperature, play important roles in dye adsorption. The dye adsorption largely depends on the initial pH of the solution with maximum uptake occurring at pH 1. Three simplified kinetics models, namely, pseudo-first order, pseudo-second order, and intraparticle diffusion models were tested to investigate the adsorption mechanisms. The kinetic adsorption of AB 062 on CW follows a pseudo-second order equation. The adsorption data have been analyzed using Langmuir and Freundlich isotherms. The results indicate that the Langmuir model provides the best correlation of the experimental data. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of the adsorption of dye onto CW.

Theoretical study of the accuracy of the pulse method, frontal analysis, and frontal analysis by characteristic points for the determination of single component adsorption isotherms.

PubMed

Andrzejewska, Anna; Kaczmarski, Krzysztof; Guiochon, Georges

2009-02-13

The adsorption isotherms of selected compounds are our main source of information on the mechanisms of adsorption processes. Thus, the selection of the methods used to determine adsorption isotherm data and to evaluate the errors made is critical. Three chromatographic methods were evaluated, frontal analysis (FA), frontal analysis by characteristic point (FACP), and the pulse or perturbation method (PM), and their accuracies were compared. Using the equilibrium-dispersive (ED) model of chromatography, breakthrough curves of single components were generated corresponding to three different adsorption isotherm models: the Langmuir, the bi-Langmuir, and the Moreau isotherms. For each breakthrough curve, the best conventional procedures of each method (FA, FACP, PM) were used to calculate the corresponding data point, using typical values of the parameters of each isotherm model, for four different values of the column efficiency (N=500, 1000, 2000, and 10,000). Then, the data points were fitted to each isotherm model and the corresponding isotherm parameters were compared to those of the initial isotherm model. When isotherm data are derived with a chromatographic method, they may suffer from two types of errors: (1) the errors made in deriving the experimental data points from the chromatographic records; (2) the errors made in selecting an incorrect isotherm model and fitting to it the experimental data. Both errors decrease significantly with increasing column efficiency with FA and FACP, but not with PM.

Novel biosynthesized silver nanoparticles from cobweb as adsorbent for Rhodamine B: equilibrium isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.; Oyedeji, Abdulrasaq O.

2018-03-01

This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity ( q max) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-second-order kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (Δ H°, Δ S° and Δ G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy ( E) and activation energy ( E a) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

Adsorption of malachite green from aqueous solution by using novel chitosan ionic liquid beads.

PubMed

Naseeruteen, Faizah; Hamid, Nur Shahirah Abdul; Suah, Faiz Bukhari Mohd; Ngah, Wan Saime Wan; Mehamod, Faizatul Shimal

2018-02-01

Chitosan ionic liquid beads were prepared from chitosan and 1-butyl-3-methylimidazolium based ionic liquids to remove Malachite Green (MG) from aqueous solutions. Batch adsorption experiments were carried out as a function of initial pH, adsorbent dosage, agitation time and initial MG concentration. The optimum conditions were obtained at pH 4.0, 0.008g of adsorbent dosage and 20min of agitation time were utilized in the kinetic and isotherm studies. Three kinetic models were applied to analyze the kinetic data and pseudo-second order was found to be the best fitted model with R 2 >0.999. In order to determine the adsorption capacity, the sorption data were analyzed using the linear form of Langmuir, Freundlich and Temkin equations. The isotherm was best fitted by Langmuir isotherm model. The maximum adsorption capacity (q max ) obtained from Langmuir isotherm for two chitosan beads 1-butyl-3-methylimidazolium acetate A and 1-butyl-3-methylimidazolium B are 8.07mgg -1 and 0.24mgg -1 respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter

ERIC Educational Resources Information Center

Wadso, Lars; Li, Xi.

2008-01-01

Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction calorimeter built for use in teaching; we also provide an example of its use in simultaneously…

Influence of system size on the properties of a fluid adsorbed in a nanopore: Physical manifestations and methodological consequences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puibasset, Joël, E-mail: puibasset@cnrs-orleans.fr; Kierlik, Edouard, E-mail: edouard.kierlik@upmc.fr; Tarjus, Gilles, E-mail: tarjus@lptl.jussieu.fr

Hysteresis and discontinuities in the isotherms of a fluid adsorbed in a nanopore in general hamper the determination of equilibrium thermodynamic properties, even in computer simulations. A way around this has been to consider both a reservoir of small size and a pore of small extent in order to restrict the fluctuations of density and approach a classical van der Waals loop. We assess this suggestion by thoroughly studying through Monte Carlo simulations and density functional theory the influence of system size on the equilibrium configurations of the adsorbed fluid and on the resulting isotherms. We stress the importance ofmore » pore-symmetry-breaking states that even for modest pore sizes lead to discontinuous isotherms and we discuss the physical relevance of these states and the methodological consequences for computing thermodynamic quantities.« less

Kinetic, isotherm and thermodynamic studies of amaranth dye biosorption from aqueous solution onto water hyacinth leaves.

PubMed

Guerrero-Coronilla, Imelda; Morales-Barrera, Liliana; Cristiani-Urbina, Eliseo

2015-04-01

The present study explored the kinetics, equilibrium and thermodynamics of amaranth (acid red 27) anionic dye (AD) biosorption to water hyacinth leaves (LEC). The effect of LEC particle size, contact time, solution pH, initial AD concentration and temperature on AD biosorption was studied in batch experiments. AD biosorption increased with rising contact time and initial AD concentration, and with decreasing LEC particle size and solution pH. Pseudo-second-order chemical reaction kinetics provided the best correlation for the experimental data. Isotherm studies showed that the biosorption of AD onto LEC closely follows the Langmuir isotherm, with a maximum biosorption capacity of about 70 mg g(-1). The thermodynamic parameters confirm that AD biosorption by LEC is non-spontaneous and endothermic in nature. Results indicate that LEC is a strong biosorbent capable of effective detoxification of AD-laden wastewaters. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of fiber-matrix adhesion on the creep behavior of CF/PPS composites: temperature and physical aging characterization

NASA Astrophysics Data System (ADS)

Motta Dias, M. H.; Jansen, K. M. B.; Luinge, J. W.; Bersee, H. E. N.; Benedictus, R.

2016-06-01

The influence of fiber-matrix adhesion on the linear viscoelastic creep behavior of `as received' and `surface modified' carbon fibers (AR-CF and SM-CF, respectively) reinforced polyphenylene sulfide (PPS) composite materials was investigated. Short-term tensile creep tests were performed on ±45° specimens under six different isothermal conditions, 40, 50, 60, 65, 70 and 75 °C. Physical aging effects were evaluated on both systems using the short-term test method established by Struik. The results showed that the shapes of the curves were affected neither by physical aging nor by the test temperature, allowing then superposition to be made. A unified model was proposed with a single physical aging and temperature-dependent shift factor, a_{T,te}. It was suggested that the surface treatment carried out in SM-CF/PPS had two major effects on the creep response of CF/PPS composites at a reference temperature of 40 °C: a lowering of the initial compliance of about 25 % and a slowing down of the creep response of about 1.1 decade.

The Langmuir isotherm: a commonly applied but misleading approach for the analysis of protein adsorption behavior.

PubMed

Latour, Robert A

2015-03-01

The Langmuir adsorption isotherm provides one of the simplest and most direct methods to quantify an adsorption process. Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application. The physical events that cause protein adsorption isotherms to often provide a Langmuir-shaped isotherm can be explained as being due to changes in adsorption-induced spreading, reorientation, clustering, and aggregation of the protein on a surface as a function of solution concentration in contrast to being due to a dynamic equilibrium adsorption process, which is required for Langmuir adsorption. Unless the requirements of the Langmuir adsorption process can be confirmed, fitting of the Langmuir model to protein adsorption isotherm data to obtain thermodynamic properties, such as the equilibrium constant for adsorption and adsorption free energy, may provide erroneous values that have little to do with the actual protein adsorption process, and should be avoided. In this article, a detailed analysis of the Langmuir isotherm model is presented along with a quantitative analysis of the level of error that can arise in derived parameters when the Langmuir isotherm is inappropriately applied to characterize a protein adsorption process. © 2014 Wiley Periodicals, Inc.

Numerical simulation of transport processes in injection mold-filling during production of a cylindrical object under isothermal and non-isothermal conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, A.; Ghoshdastidar, P.S.

1999-07-01

In this paper, numerical simulation of injection mold-filling during the production of a cylindrical object under isothermal and non-isothermal conditions is presented. The material of the object is low density polyethylene (LDPE) following power-law viscosity model for non-zero shear rate zone. However, where shear rate becomes zero, zero-shear viscosity value has been used. Three cases have been considered, namely (1) Isothermal filling at constant injection pressure, (2) Isothermal filling at constant flow rate, and (3) Non-isothermal filling at constant flow rate. For the case-(3), the viscosity of LDPE is also a function of temperature. The material of the mold ismore » steel. For the non-isothermal filling, the concept of melt-mold thermal contact resistance coefficient has been incorporated in the model. The length and diameter of the body in all three cases have been taken as 0.254 m and 0.00508 m respectively. The finite-difference method has been used to solve the governing differential equations for the processes. The results show excellent agreement with the corresponding equations for the processes. The results show excellent agreement with the corresponding analytical solutions for the first two cases showing the correctness of the numerical method. The simulation results for non-isothermal filling show physically realistic trends and lend insight into various important aspects of mold-filling including frozen skin layer.« less

Proceedings of the 7th Semiannual Meeting of the Nozzle Initiative Industry Advisory Committee on Standardization of Carbon-Phenolic Test Methods and Specifications

NASA Technical Reports Server (NTRS)

Hall, William B. (Compiler); Pinoli, Pat C. (Compiler); Upton, Cindy G. (Compiler)

1991-01-01

The application of carbon fibers and fabrics (CF) for producing rocket nozzles is discussed. These materials which are essential for fabricating the carbon composites used in aerospace systems gasify when exposed to high temperatures and the mechanical properties of the composites degrade. The oxidation kinetics under isothermal (IC) and non-isothermal (NIC) conditions are examined and a comparison is made between the characteristics of IC and NIC oxidation. Several CF, chars, and carbon blacks were examined, including a microporous char, a graphitized rayon fabric, and several carbonized rayon fabrics. A summary is given of the advantages and drawbacks of isothermal and non-isothermal oxidation of carbons. The proceedings are assembled in the form of a roundtable discussion.

Physics of heat pipe rewetting

NASA Technical Reports Server (NTRS)

Chan, S. H.

1992-01-01

Although several studies have been made to determine the rewetting characteristics of liquid films on heated rods, tubes, and flat plates, no solutions are yet available to describe the rewetting process of a hot plate subjected to a uniform heating. A model is presented to analyze the rewetting process of such plates with and without grooves. Approximate analytical solutions are presented for the prediction of the rewetting velocity and the transient temperature profiles of the plates. It is shown that the present rewetting velocity solution reduces correctly to the existing solution for the rewetting of an initially hot isothermal plate without heating from beneath the plate. Numerical solutions have also been obtained to validate the analytical solutions.

Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density.

PubMed

Carter, Ellison M; Katz, Lynn E; Speitel, Gerald E; Ramirez, David

2011-08-01

Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.

Statistical physics studies of multilayer adsorption isotherm in food materials and pore size distribution

NASA Astrophysics Data System (ADS)

Aouaini, F.; Knani, S.; Ben Yahia, M.; Ben Lamine, A.

2015-08-01

Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.

Adsorption Studies of Chromium(VI) on Activated Carbon Derived from Mangifera indica (Mango) Seed Shell

NASA Astrophysics Data System (ADS)

Mise, Shashikant; Patil, Trupti Nagendra

2015-09-01

The removal of chromium(VI) from synthetic sample by adsorption on activated carbon prepared from Mangifera indica (mango) seed shell have been carried out at room temperature 32 ± 1 °C. The removal of chromium(VI) from synthetic sample by adsorption on two types of activated carbon, physical activation and chemical activation (Calcium chloride and Sodium chloride), Impregnation Ratio's (IR) 0.25, 0.50, 0.75 for optimum time, optimum dosages and variation of pH were studied. It is observed that contact time differs for different carbons i.e. for physically and chemically activated carbons. The contact time decreases for chemically activated carbon compared to the physically activated carbon. It was observed that as dosage increases the adsorption increased along with the increase in impregnation ratio. It was also noted that as I.R. increases the surface area of Mangifera indica shell carbon increased. These dosage data were considered in the construction of isotherms and it was found that adsorption obeys Freundlich Isotherm and does not obey Langmuir Isotherm. The maximum removal of chromium (VI) was obtained in highly acidic medium at a pH of 1.50.

Carbon composite lignin-based adsorbents for the adsorption of dyes.

PubMed

Wang, Xiaohong; Jiang, Chenglong; Hou, Bingxia; Wang, Yingying; Hao, Chen; Wu, Jingbo

2018-05-10

Carbon composite lignin-based adsorbent were prepared through hydrothermal method with glucose as carbon source, calcium lignosulfonate and triethylene tetramine as raw materials, respectively. The optimum synthesis conditions were determined by investigating the addition of carbon and triethylene tetramine. The adsorbent was used for the adsorption of azo dyes Congo red and Eriochrome blue black R, and the five factors affecting the adsorption were discussed, including pH of dyes, initial concentration, adsorption time, adsorption temperature and adsorbent dosage. The corresponding adsorption mechanism such as pseudo first order kinetics, pseudo second order kinetics, intraparticle diffusion, Langmuir adsorption isotherm, Freundlich isotherm, Temkin isotherm, Dubinin-Radushkevich adsorption isotherm, thermodynamics were also studied. When the dye concentration is 40 mg L -1 , Congo red and Eriochrome blue black R dye removal rates reach 99%. Moreover, the adsorption process of two kinds of dyes follow the pseudo second order kinetics and the Langmuir adsorption isotherm. Copyright © 2018 Elsevier Ltd. All rights reserved.

Isothermal approach to predict the removal efficiency of β-carotene adsorption from CPO using activated carbon produced from tea waste

NASA Astrophysics Data System (ADS)

Harahap, S. A. A.; Nazar, A.; Yunita, M.; Pasaribu, RA; Panjaitan, F.; Yanuar, F.; Misran, E.

2018-02-01

Adsorption of β-carotene in crude palm oil (CPO) was studied using activated carbon produced from tea waste (ACTW) an adsorbent. Isothermal studies were carried out at 60 °C with the ratio of activated carbon to CPO were 1:3, 1:4, 1:5, and 1:6, respectively. The ACTW showed excellent performance as the percentage of adsorption of β-carotene from CPO was > 99%. The best percentage removal (R) was achieved at ACTW to CPO ratio equal to 1:3, which was 99.61%. The appropriate isotherm model for this study was Freundlich isotherm model. The combination of Freundlich isotherm equation and mass balance equation showed a good agreement when validated to the experimental data. The equation subsequently executed to predict the removal efficiency under given sets of operating conditions. At a targetted R, CPO volume can be estimated for a certain initial concentration β-carotene in CPO C0 and mass of ACTW adsorbent M used.

Isothermal amplification detection of nucleic acids by a double-nicked beacon.

PubMed

Shi, Chao; Zhou, Meiling; Pan, Mei; Zhong, Guilin; Ma, Cuiping

2016-03-01

Isothermal and rapid amplification detection of nucleic acids is an important technology in environmental monitoring, foodborne pathogen detection, and point-of-care clinical diagnostics. Here we have developed a novel method of isothermal signal amplification for single-stranded DNA (ssDNA) detection. The ssDNA target could be used as an initiator, coupled with a double-nicked molecular beacon, to originate amplification cycles, achieving cascade signal amplification. In addition, the method showed good specificity and strong anti-jamming capability. Overall, it is a one-pot and isothermal strand displacement amplification method without the requirement of a stepwise procedure, which greatly simplifies the experimental procedure and decreases the probability of contamination of samples. With its advantages, the method would be very useful to detect nucleic acids in point-of-care or field use. Copyright © 2015 Elsevier Inc. All rights reserved.

[Evaluation of the influence of humidity and temperature on the drug stability by initial average rate experiment].

PubMed

He, Ning; Sun, Hechun; Dai, Miaomiao

2014-05-01

To evaluate the influence of temperature and humidity on the drug stability by initial average rate experiment, and to obtained the kinetic parameters. The effect of concentration error, drug degradation extent, humidity and temperature numbers, humidity and temperature range, and average humidity and temperature on the accuracy and precision of kinetic parameters in the initial average rate experiment was explored. The stability of vitamin C, as a solid state model, was investigated by an initial average rate experiment. Under the same experimental conditions, the kinetic parameters obtained from this proposed method were comparable to those from classical isothermal experiment at constant humidity. The estimates were more accurate and precise by controlling the extent of drug degradation, changing humidity and temperature range, or by setting the average temperature closer to room temperature. Compared with isothermal experiments at constant humidity, our proposed method saves time, labor, and materials.

Removal of paraquat solution onto zeolite material

NASA Astrophysics Data System (ADS)

Sirival, Rujikarn; Patdhanagul, Nopbhasinthu; Preecharram, Sutthidech; Photharin, Somkuan

2018-04-01

The purpose of this research was to study the adsorption of paraquat herbicides onto zeolite Y materials by the batch method. Three adsorbents material: Zeolite-3, Zeolite-10, and Zeolite-100 were Si/Al ratio at 3.58, 8.57 and 154.37, respectively. The factors for adsorption of paraquat as follows, adsorption time, initial concentrations of paraquat, pH and adsorption isotherm were investigated. The results showed that zeolite-10 had higher adsorption capacity than zeolite-3 and zeolite-100. The appropriate conditions for adsorption were 24 h., Zeolite 0.1 g., Initial paraquat concentration 100 ppm at pH 6. The adsorption isotherm was found to correspond with Langmuir Isotherm and the maximum paraquat adsorption is 26.38 mg/g for zeolite-10, 21.41 mg/g and 9.60 mg/g for zeolite-3 and zeolite-100, respectively. The characterization of zeolite material with XRD, XRF and BET. Furthermore, the zeolite materials applied to remove other organic and inorganic wastewater.

Hydrostatic Adjustment in Vertically Stratified Atmospheres

NASA Technical Reports Server (NTRS)

Duffy, Dean G.

2000-01-01

Hydrostatic adjustment due to diabatic heat in two nonisothermal atmospheres is examined. In the first case the temperature stratification is continuous; in the second case the atmosphere is composed of a warm, isothermal troposphere and a colder, isothermal semi-infinitely deep stratosphere.In both cases hydrostatic adjustment, to a good approximation, follows the pattern found in the Lamb problem (semi-infinitely deep. isothermal atmosphere): Initially we have acoustic waves with the kinetic energy increasing or decreasing at the expense of available elastic energy. After this initial period the acoustic waves evolve into acoustic-gravity waves with the kinetic, available potential and available elastic energies interacting with each other. Relaxation to hydrostatic balance occurs within a few oscillations. Stratification in an atmosphere with a continuous temperature profile affects primarily the shape and amplitude of the disturbances. In the two-layer atmosphere, a certain amount of energy is trapped in the tropospheric waveguide as disturbances reflect off the tropopause and back into the troposphere. With each internal reflection a portion of this trapped energy escapes and radiates to infinity.

TOUGHREACT: a new code of the TOUGH Family for Non-Isothermal multiphase reactive geochemical transport in variably saturated geologic media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas

Coupled modeling of subsurface multiphase fluid and heat flow, solute transport and chemical reactions can be used for the assessment of acid mine drainage remediation, waste disposal sites, hydrothermal convection, contaminant transport, and groundwater quality. We have developed a comprehensive numerical simulator, TOUGHREACT, which considers non-isothermal multi-component chemical transport in both liquid and gas phases. A wide range of subsurface thermo-physical-chemical processes is considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. The code can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity.

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

NASA Astrophysics Data System (ADS)

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.

Miniaturized isothermal nucleic acid amplification, a review.

PubMed

Asiello, Peter J; Baeumner, Antje J

2011-04-21

Micro-Total Analysis Systems (µTAS) for use in on-site rapid detection of DNA or RNA are increasingly being developed. Here, amplification of the target sequence is key to increasing sensitivity, enabling single-cell and few-copy nucleic acid detection. The several advantages to miniaturizing amplification reactions and coupling them with sample preparation and detection on the same chip are well known and include fewer manual steps, preventing contamination, and significantly reducing the volume of expensive reagents. To-date, the majority of miniaturized systems for nucleic acid analysis have used the polymerase chain reaction (PCR) for amplification and those systems are covered in previous reviews. This review provides a thorough overview of miniaturized analysis systems using alternatives to PCR, specifically isothermal amplification reactions. With no need for thermal cycling, isothermal microsystems can be designed to be simple and low-energy consuming and therefore may outperform PCR in portable, battery-operated detection systems in the future. The main isothermal methods as miniaturized systems reviewed here include nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP), helicase-dependent amplification (HDA), rolling circle amplification (RCA), and strand displacement amplification (SDA). Also, important design criteria for the miniaturized devices are discussed. Finally, the potential of miniaturization of some new isothermal methods such as the exponential amplification reaction (EXPAR), isothermal and chimeric primer-initiated amplification of nucleic acids (ICANs), signal-mediated amplification of RNA technology (SMART) and others is presented.

MHD Flow of Sodium Alginate-Based Casson Type Nanofluid Passing Through A Porous Medium With Newtonian Heating.

PubMed

Khan, Arshad; Khan, Dolat; Khan, Ilyas; Ali, Farhad; Karim, Faizan Ul; Imran, Muhammad

2018-06-05

Casson nanofluid, unsteady flow over an isothermal vertical plate with Newtonian heating (NH) is investigated. Sodium alginate (base fluid)is taken as counter example of Casson fluid. MHD and porosity effects are considered. Effects of thermal radiation along with heat generation are examined. Sodium alginate with Silver, Titanium oxide, Copper and Aluminum oxide are added as nano particles. Initial value problem with physical boundary condition is solved by using Laplace transform method. Exact results are obtained for temperature and velocity fields. Skin-friction and Nusselt number are calculated. The obtained results are analyzed graphically for emerging flow parameters and discussed. It is bring into being that temperature and velocity profile are decreasing with increasing nano particles volume fraction.

All-aromatic biphenylene end-capped polyquinoline and polyimide matrix resins

NASA Technical Reports Server (NTRS)

Droske, J. P.; Stille, J. K.; Alston, W. B.

1985-01-01

Biphenylene end-capped polyquinoline and polyimide resins afford low void content graphite-reinforced composites with good initial properties. However, with both resins, rapid degradation occurs during oxidative isothermal aging at elevated temperatures. The degradation is not observed during isothermal aging under a nitrogen atmosphere which suggests that the biphenylene end-cap (or the resulting crosslink/chain extension structures) is not particularly thermooxidatively stable. The nature of the thermooxidative instability is currently under investigation.

Adsorption equilibrium of organic vapors on single-walled carbon nanotubes

USGS Publications Warehouse

Agnihotri, S.; Rood, M.J.; Rostam-Abadi, M.

2005-01-01

Gravimetric techniques were employed to determine the adsorption capacities of commercially available purified electric arc and HiPco single-walled carbon nanotubes (SWNTs) for organic compounds (toluene, methyl ethyl ketone (MEK), hexane and cyclohexane) at relative pressures, p/p0, ranging from 1 ?? 10-4 to 0.95 and at isothermal conditions of 25, 37 and 50 ??C. The isotherms displayed both type I and type II characteristics. Adsorption isotherm modeling showed that SWNTs are heterogeneous adsorbents, and the Freundlich equation best describes the interaction between organic molecules and SWNTs. The heats of adsorption were 1-4 times the heats of vaporization, which is typical for physical adsorption of organic vapors on porous carbons. ?? 2005 Elsevier Ltd. All rights reserved.

The Effects of Thermal Energetics on Three-dimensional Hydrodynamic Instabilities in Massive Protostellar Disks. II. High-Resolution and Adiabatic Evolutions

NASA Astrophysics Data System (ADS)

Pickett, Brian K.; Cassen, Patrick; Durisen, Richard H.; Link, Robert

2000-02-01

In this paper, the effects of thermal energetics on the evolution of gravitationally unstable protostellar disks are investigated by means of three-dimensional hydrodynamic calculations. The initial states for the simulations correspond to stars with equilibrium, self-gravitating disks that are formed early in the collapse of a uniformly rotating, singular isothermal sphere. In a previous paper (Pickett et al.), it was shown that the nonlinear development of locally isentropic disturbances can be radically different than that of locally isothermal disturbances, even though growth in the linear regime may be similar. When multiple low-order modes grew rapidly in the star and inner disk region and saturated at moderate nonlinear levels in the isentropic evolution, the same modes in the isothermal evolution led to shredding of the disk into dense arclets and ejection of material. In this paper, we (1) examine the fate of the shredded disk with calculations at higher spatial resolution than the previous simulations had and (2) follow the evolution of the same initial state using an internal energy equation rather than the assumption of locally isentropic or locally isothermal conditions. Despite the complex structure of the nonlinear features that developed in the violently unstable isothermal disk referred to above, our previous calculation produced no gravitationally independent, long-lived stellar or planetary companions. The higher resolution calculations presented here confirm this result. When the disk of this model is cooled further, prompting even more violent instabilities, the end result is qualitatively the same--a shredded disk. At least for the disks studied here, it is difficult to produce condensations of material that do not shear away into fragmented spirals. It is argued that the ultimate fate of such fragments depends on how readily local internal energy is lost. On the other hand, if a dynamically unstable disk is to survive for very long times without shredding, then some mechanism must mitigate and control any violent phenomena that do occur. The prior simulations demonstrated a marked difference in final outcome, depending upon the efficiency of disk cooling under two different, idealized thermal conditions. We have here incorporated an internal energy equation that allows for arbitrary heating and cooling. Simulations are presented for adiabatic models with and without artificial viscosity. The artificial viscosity accounts for dissipation and heating due to shocks in the code physics. The expected nonaxisymmetric instabilities occur and grow as before in these energy equation evolutions. When artificial viscosity is not present, the model protostar displays behavior between the locally isentropic and locally isothermal cases of the last paper; a strong two-armed spiral grows to nonlinear amplitudes and saturates at a level higher than in the locally isentropic case. Since the amplitude of the spiral disturbance is large, it is expected that continued transport of material and angular momentum will occur well after the end of the calculation at nearly four outer rotation periods. The spiral is not strong enough, however, to disrupt the disk as in the locally isothermal case. When artificial viscosity is present, the same disturbances reach moderate nonlinear amplitude, then heat the gas, which in turn greatly reduces their strength and effects on the disk. Additional heating in the low-density regions of the disk also leads to a gentle flow of material vertically off the computational grid. The energy equation and high-resolution isothermal calculations are used to discuss the importance and relevance of the different thermal regimes so far examined, with particular attention to applications to star and planet formation.

Adsorption of intrinsically disordered barnacle adhesive proteins on silica surface

NASA Astrophysics Data System (ADS)

Wang, Xiaoqiang; Wang, Chao; Xu, Baomei; Wei, Junting; Xiao, Yang; Huang, Fang

2018-01-01

The adsorption of recombinant barnacle proteins Bacp19k and Mrcp19k on hydrophilic silica surface was characterized by spectroscopic ellipsometry in artificial seawater (pH = 8.2). They are homologous adhesive proteins destined for underwater adhesion but bear opposite net charges in seawater. As assessed with their primary and secondary structures, both proteins are intrinsically disordered and thus distinct from globular proteins that have dominated research in the field. Different from Mrcp19k, higher initial rate and adsorbed amount were obtained via curve fitting for Bacp19k in kinetic studies, due to favorable charge interactions with silica surface. The good fitting with the same dynamic model also indicates the formation of monolayer coverage in both cases. The two adsorption isotherms of Bacp19k and Mrcp19k are different in the initial change and maximum adsorption level, indicating different protein-surface affinities and charge interactions. Each isotherm fits the Langmuir model well, which is commonly used to describe monolayer adsorption, thus consistent with the predication from kinetic fitting. To further examine the effect of electrostatic interaction on the adsorption, the isotherm of the 1:1 mixture of Bacp19k and Mrcp19k was also constructed, which showed a higher correlation fit for Jovanovic than for Langmuir model. The presence of electrostatic attraction between Bacp19k and Mrcp19k deviated from one of the required conditions for Langmuir behavior, which may also result in the highest coadsorption level but slowest initial change among the three isotherms. The surface state of the adhesive proteins and the change with adsorption time were also examined by atomic force microscopy. The results thus obtained are in good agreement with the corresponding ellipsometric measurement.

Flow behind an exponential shock wave in a rotational axisymmetric perfect gas with magnetic field and variable density.

PubMed

Nath, G; Sahu, P K

2016-01-01

A self-similar model for one-dimensional unsteady isothermal and adiabatic flows behind a strong exponential shock wave driven out by a cylindrical piston moving with time according to an exponential law in an ideal gas in the presence of azimuthal magnetic field and variable density is discussed in a rotating atmosphere. The ambient medium is assumed to possess radial, axial and azimuthal component of fluid velocities. The initial density, the fluid velocities and magnetic field of the ambient medium are assumed to be varying with time according to an exponential law. The gas is taken to be non-viscous having infinite electrical conductivity. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector. The effects of the variation of the initial density index, adiabatic exponent of the gas and the Alfven-Mach number on the flow-field behind the shock wave are investigated. It is found that the presence of the magnetic field have decaying effects on the shock wave. Also, it is observed that the effect of an increase in the magnetic field strength is more impressive in the case of adiabatic flow than in the case of isothermal flow. The assumption of zero temperature gradient brings a profound change in the density, non-dimensional azimuthal and axial components of vorticity vector distributions in comparison to those in the case of adiabatic flow. A comparison is made between isothermal and adiabatic flows. It is obtained that an increase in the initial density variation index, adiabatic exponent and strength of the magnetic field decrease the shock strength.

Equation of State of Ammonium Nitrate

NASA Astrophysics Data System (ADS)

Robbins, David L.; Sheffield, Stephen A.; Dattelbaum, Dana M.; Velisavljevic, Nenad; Stahl, David B.

2009-12-01

Ammonium nitrate (AN) is a widely used fertilizer and mining explosive. AN is commonly used in ammonium nitrate-fuel oil (ANFO), which is a mixture of explosive-grade AN prills and fuel oil in a 94:6 ratio by weight. ANFO is a non-ideal explosive with measured detonation velocities around 4 km/s. The equation of state properties and known initiation behavior of neat AN are limited. We present the results of a series of gas gun-driven plate impact experiments on pressed neat ammonium nitrate at 1.72 g/cm3. No evidence of initiation was observed under shock loading to 22 GPa. High pressure x-ray diffraction experiments in diamond anvil cells provided insight into the high pressure phase behavior over the same pressure range (to 25 GPa), as well as a static isotherm at ambient temperature. From the isotherm and thermodynamic properties at ambient conditions, a preliminary unreacted equation of state (EOS) has been developed based on the Murnaghan isotherm and Helmholtz formalism [1], which compares favorably with the available experimental Hugoniot data on several densities of AN.

Malachite Green Adsorption by Spent Coffee Grounds

NASA Astrophysics Data System (ADS)

Syamimie Atirah Mat, Siti; Zati Hanani Syed Zuber, Sharifah; Rahim, Siti Kartini Enche Ab; Sohaimi, Khairunissa Syairah Ahmad; Halim, Noor Amirah Abdul; Fauziah Zainudin, Nor; Aida Yusoff, Nor; Munirah Rohaizad, Nor; Hidayah Ishak, Noor; Anuar, Adilah; Sarip, Mohd Sharizan Md

2018-03-01

In this work, the ability of spent coffee grounds (SCG) as a low-cost adsorbent to remove malachite green (MG) from aqueous solutions was studied. Batch adsorption tests were carried out to observe the effect of various experimental parameters such as contact time, initial concentration of malachite green and adsorbent dosage on the removal of dye. The results obtained show that the percentage of dye removal will decreased with the increased of initial concentration of dye in the range of 50 mg/L to 250 mg/L. Besides, percentage removal of dye was also found to be increased as the contact time increased until it reached equilibrium condition. The results also showed that the adsorbent dosage in range of 0.2 g to 1.0 g is proportional to the percentage removal of malachite green dye. Study on the kinetic adsorption and isotherm adsorption has also been investigated. The adsorption isotherm data were described by Langmuir isotherm with high-correlation coefficients while the experimental data showed the pseudo-second-order kinetics model was the best model for the adsorption of MG by SCG with the coefficients of correlation R2 > 0.9978.

Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization, Equilibrium Isotherms, and Adsorption Kinetics Study

PubMed Central

Khandanlou, Roshanak; Ahmad, Mansor B.; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

2015-01-01

Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles. PMID:25815470

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

NASA Astrophysics Data System (ADS)

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.

Adsorption of Copper Ion using Acrylic Acid-g-Polyaniline in Aqueous Solution

NASA Astrophysics Data System (ADS)

Kamarudin, Sabariah; Mohammad, Masita

2018-04-01

A conductive polymer, polyaniline (PANI) has unique electrical behaviour, stable in the environment, easy synthesis and have wide application in various fields. Modification of PANI in order to improve its adsorption capacity has been done. In this study, the polyaniline-grafted acrylic acid has been prepared and followed by adsorption of copper ion in aqueous solution. Acrylic acid, PANI and acrylic acid-g-polyaniline (Aag-PANI) were characterized by FTIR and SEM to determine its characteristic. The adsorption capacity was investigated to study the removal capacity of Cu ion from aqueous solution. Two parameters were selected which are pH (2, 4 and 6) and initial metal ion concentration (50 mg/L, 100 mg/L and 200 mg/L). The maximum adsorption capacity for PANI and Aag-PANI are 1.7 mg/g and 64.6 mg/g, respectively, at an initial concentration of 100 mg/L. The Langmuir adsorption isotherm model and Freundlich adsorption isotherm model have been used and showed that it is heterolayer adsorption by follows the Freundlich isotherm model.

Simulation of Watts Bar Unit 1 Initial Startup Tests with Continuous Energy Monte Carlo Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Godfrey, Andrew T; Gehin, Jess C; Bekar, Kursat B

2014-01-01

The Consortium for Advanced Simulation of Light Water Reactors* is developing a collection of methods and software products known as VERA, the Virtual Environment for Reactor Applications. One component of the testing and validation plan for VERA is comparison of neutronics results to a set of continuous energy Monte Carlo solutions for a range of pressurized water reactor geometries using the SCALE component KENO-VI developed by Oak Ridge National Laboratory. Recent improvements in data, methods, and parallelism have enabled KENO, previously utilized predominately as a criticality safety code, to demonstrate excellent capability and performance for reactor physics applications. The highlymore » detailed and rigorous KENO solutions provide a reliable nu-meric reference for VERAneutronics and also demonstrate the most accurate predictions achievable by modeling and simulations tools for comparison to operating plant data. This paper demonstrates the performance of KENO-VI for the Watts Bar Unit 1 Cycle 1 zero power physics tests, including reactor criticality, control rod worths, and isothermal temperature coefficients.« less

Experimental binding of lead to a low cost on biosorbent: Nopal (Opuntia streptacantha).

PubMed

Miretzky, Patricia; Muñoz, Carolina; Carrillo-Chávez, Alejandro

2008-03-01

The use of nopal cladodes (Opuntia streptacantha) as raw material for Pb(2+) biosorption was investigated. Batch experiments were carried out to determine Pb(2+) sorption capacity and the efficiency of the sorption process under different pH, initial Pb(2+) and nopal biomass concentrations. The experimental data showed a good fit to Langmuir and Freundlich isotherms models. The maximum adsorption capacity for Pb(2+) was 0.14 mmol g(-1) with an efficiency higher than 94% (pH 5.0 and 2.5 g L(-1) nopal biomass). The Pb(2+) kinetics were best described by the pseudo-second-order rate model. The rate constant, the initial sorption rate and the equilibrium sorption capacity were determined. The practical implication of this study is the development of an effective and economic technology in which the nopal biomass did not undergo any chemical or physical pretreatment, which added to nopal abundance in Mexico and its low cost makes it a good option for Pb(2+) removal from contaminated waters.

Water-Column Stratification Observed along an AUV-Tracked Isotherm

NASA Astrophysics Data System (ADS)

Zhang, Y.; Messié, M.; Ryan, J. P.; Kieft, B.; Stanway, M. J.; Hobson, B.; O'Reilly, T. C.; Raanan, B. Y.; Smith, J. M.; Chavez, F.

2016-02-01

Studies of marine physical, chemical and microbiological processes benefit from observing in a Lagrangian frame of reference, i.e. drifting with ambient water. Because these processes can be organized relative to specific density or temperature ranges, maintaining observing platforms within targeted environmental ranges is an important observing strategy. We have developed a novel method to enable a Tethys-class long-range autonomous underwater vehicle (AUV) (which has a propeller and a buoyancy engine) to track a target isotherm in buoyancy-controlled drift mode. In this mode, the vehicle shuts off its propeller and autonomously detects the isotherm and stays with it by actively controlling the vehicle's buoyancy. In the June 2015 CANON (Controlled, Agile, and Novel Observing Network) Experiment in Monterey Bay, California, AUV Makai tracked a target isotherm for 13 hours to study the coastal upwelling system. The tracked isotherm started from 33 m depth, shoaled to 10 m, and then deepened to 29 m. The thickness of the tracked isotherm layer (within 0.3°C error from the target temperature) increased over this duration, reflecting weakened stratification around the isotherm. During Makai's isotherm tracking, another long-range AUV, Daphne, acoustically tracked Makai on a circular yo-yo trajectory, measuring water-column profiles in Makai's vicinity. A wave glider also acoustically tracked Makai, providing sea surface measurements on the track. The presented method is a new approach for studying water-column stratification, but requires careful analysis of the temporal and spatial variations mingled in the vehicles' measurements. We will present a synthesis of the water column's stratification in relation to the upwelling conditions, based on the in situ measurements by the mobile platforms, as well as remote sensing and mooring data.

Ad-/desorption behavior of Sulfadiazine on soil and soil components

NASA Astrophysics Data System (ADS)

Meng, N.; Lewandowski, H.; Kasteel, R.; Narres, H.-D.; Klumpp, E.; Vereecken, H.

2009-04-01

Sulfadiazine [4-amino-N-(2-pyrimidinyl)benzene sulfonamide, SDZ] belongs to the widely used antibacterial veterinary pharmaceuticals which reach the environment by the application of manure. Therefore the adsorption and desorption behavior of 14C labeled sulfadiazine was investigated with different inorganic soil components including Al2O3, goethite, illite and compared with air-dried topsoil. The batch sorption experiments with Al2O3and soil were performed in natural pH-values (8.2 and 7.5, negatively charged SDZ). Experiments with illite and goethite were done with pH-values of 4.2 and 6.8 (natural pH of illite and goethite, neutral and partly negatively charged SDZ) and also done in buffer solution about pH 8 for comparing the adsorption on all adsorbents in same pH range. The adsorption isotherms on all sorbents are strongly nonlinear and can be fitted well by the Freundlich equation. From the initial slope of the isotherm the partition coefficient Kd could be determined. The adsorption of SDZ on illite at pH 4.2 and on goethite at pH 6.8 has higher Kd-values than at pH 8, which demonstrates that the negative charge of SDZ obstructs the adsorption. The desorption isotherms show hysteresis effects for all adsorbents. The strong hysteresis was found for goethite and soil indicates strongly physical or chemical binding. On the other hand, the low hysteresis effect for Al2O3 and illite indicates the weak binding of the adsorbed SDZ. The properties of the inorganic matrix and especially the charges of the inorganic compounds in relation to the charge of SDZ are important parameters for the sorption process. The data could be described by modeling with different sorption rates and sites.

Experimental characterization and modeling of isothermal and nonisothermal physical aging in glassy polymer films

NASA Astrophysics Data System (ADS)

Guo, Yunlong

This dissertation focuses on nonisothermal physical aging of polymers from both experimental and theoretical aspects. The study concentrates on pure polymers rather than fiber-reinforced composites; this step removes several complicating factors to simplify the study. It is anticipated that the findings of this work can then be applied to composite materials applications. The physical aging tests in this work are performed using a dynamic mechanical analyzer (DMA). The viscoelastic response of glassy polymers under various loading and thermal histories are observed as stress-strain data at a series of time points. The first stage of the experimental work involves the characterization of the isothermal physical aging behavior of two advanced thermoplastics. The second stage conducts tests on the same materials with varying thermal histories and with long-term test duration. This forms the basis to assess and modify a nonisothermal physical aging model (KAHR-ate model). Based on the experimental findings, the KAHR-ate model has been revised by new correlations between aging shift factors and volume response; this revised model performed well in predicting the nonisothermal physical aging behavior of glassy polymers. In the work on isothermal physical aging, short-term creep and stress relaxation tests were performed at several temperatures within 15-35°C below the glass transition temperature (Tg) at various aging times, using the short-term test method established by Struik. Stress and strain levels were such that the materials remained in the linear viscoelastic regime. These curves were then shifted together to determine momentary master curves and shift rates. In order to validate the obtained isothermal physical aging behavior, the results of creep and stress relaxation testing were compared and shown to be consistent with one another using appropriate interconversion of the viscoelastic material functions. Time-temperature superposition of the master curves was also performed. The temperature shift factors and aging shift rates for both PEEK and PPS were consistent for both creep and stress relaxation test results. Nonisothermal physical aging was monitored by sequential short-term creep tests after a series of temperature jumps; the resulting strain histories were analyzed to determine aging shift factors (ate) for each of the creep tests. The nonisothermal aging response was predicted using the KAHR-ate model, which combines the KAHR model of volume recovery with a suitable linear relationship between aging shift factors and specific volume. The KAHR-ate model can be utilized to both predict aging response and to determine necessary model parameters from a set of aging shift factor data. For the PEEK and PPS materials considered in the current study, predictions of mechanical response were demonstrated to be in good agreement with the experimental results for several complicated thermal histories. In addition to short-term nonisothermal aging, long-term creep tests under identical thermal conditions were also analyzed. Effective time theory was unitized to predict long-term response under both isothermal and nonisothermal temperature histories. The long-term compliance after a series of temperature changes was predicted by the KAHR- ate model, and the theoretical predictions and experimental data showed good agreement for various thermal histories. Lastly, physical aging behavior of PPS near the glass transition temperature was investigated, in order to observe the mechanical response in the process of the evolution of the material into equilibrium. At several temperatures near Tg, the time need to reach equilibrium were determined by the creep test results at various aging times. In addition to isothermal physical aging, mechanical shift factors in the period of approaching equilibrium at a common temperature after temperature up-jumps and down-jumps are monitored from creep tests; prior to these temperature jumps, the materials were aged to reach equilibrium states. From these tests, asymmetry of approaching equilibrium phenomenon in ate was observed, which is first-time reported in the literature. This finding shows the similarity between the thermodynamic and mechanical properties during structural relaxation. This work will lead to improved understanding of the viscoelastic behavior of glassy polymers, which is important for better understanding and design of PMCs in elevated temperature applications. With the above findings, this dissertation deals with nonisothermal physical aging of glassy polymers, including both experimental characterization and constructing a framework for predictions of mechanical behavior of polymeric materials under complicated thermal conditions. (Abstract shortened by UMI.)

Isothermal crystallization of poly(3-hydroxybutyrate) studied by terahertz two-dimensional correlation spectroscopy

NASA Astrophysics Data System (ADS)

Hoshina, Hiromichi; Ishii, Shinya; Morisawa, Yusuke; Sato, Harumi; Noda, Isao; Ozaki, Yukihiro; Otani, Chiko

2012-01-01

The isothermal crystallization of poly(3-hydroxybutylate) (PHB) was studied by monitoring the temporal evolution of terahertz absorption spectra in conjunction with spectral analysis using two-dimensional correlation spectroscopy. Correlation between the absorption peaks and the sequential order of the changes in spectral intensity extracted from synchronous and asynchronous plots indicated that crystallization of PHB at 90 °C is a two step process, in which C-H...O=C hydrogen bonds are initially formed before well-defined crystal structures are established.

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite.

PubMed

Zheng, Hong; Liu, Donghong; Zheng, Yan; Liang, Shuping; Liu, Zhe

2009-08-15

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 degrees C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 degrees C. Dubinin-Redushkevich (D-R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

A study of the kinetics and isotherms for Cr(VI) adsorption in a binary mixture of Cr(VI)-Ni(II) using hierarchical porous carbon obtained from pig bone.

PubMed

Li, Chengxian; Huang, Zhe; Huang, Bicheng; Liu, Changfeng; Li, Chengming; Huang, Yaqin

2014-01-01

Cr(VI) adsorption in a binary mixture Cr(VI)-Ni(II) using the hierarchical porous carbon prepared from pig bone (HPC) was investigated. The various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as initial concentration, pH, temperature and contact time were analyzed. The results showed excellent efficiency of Cr(VI) adsorption by HPC. The kinetics and isotherms for Cr(VI) adsorption from a binary mixture Cr(VI)-Ni(II) by HPC were studied. The adsorption equilibrium described by the Langmuir isotherm model is better than that described by the Freundlich isotherm model for the binary mixture in this study. The maximum adsorption capacity was reliably found to be as high as 192.68 mg/g in the binary mixture at pH 2. On fitting the experimental data to both pseudo-first- and second-order equations, the regression analysis of the second-order equation gave a better R² value.

Non-isothermal infiltration and tracer transport experiments on large soil columns

NASA Astrophysics Data System (ADS)

Sobotkova, Martina; Snehota, Michal; Cejkova, Eva; Tesar, Miroslav

2016-04-01

Isothermal and non-isothermal infiltration experiments were carried out in the laboratory on large undisturbed soil columns (19 cm in diameter, 25 cm high) taken at the experimental catchments Roklan (Sumava Mountains, Czech Republic) and Uhlirska (Jizera Mountains, Czech republic). The aim of the study was twofold. The first goal was to obtain water flow and heat transport data for indirect parameter estimation of thermal and hydraulic properties of soils from two sites by inverse modelling. The second aim was to investigate the extent of impact of the temperature on saturated hydraulic conductivity (Ksat) and dispersity of solute transport. The temperature of infiltrating water in isothermal experiment (20 °C) was equal to the initial temperature of the sample. For non-isothermal experiment water temperature was 5°C, while the initial temperature of the sample was 20°C as in previous case. The experiment was started by flooding the sample surface. Then water level was maintained at constant level throughout the infiltration run using the optical sensor and peristaltic pump. Concentration pulse of deuterium was applied at the top of the soil sample, during the steady state flow. Initial pressure head in the sample was close to field capacity. Two tensiometers and two temperature sensors were inserted in the soil sample in two depths (9 and 15 cm below the top of the sample). Two additional temperature sensors monitored the temperature entering and leaving the samples. Water drained freely through the perforated plate at the bottom of sample by gravity. Inflow and outflow water flux densities, water pressure heads and soil temperatures were monitored continuously during experiments. Effluent was sampled in regular time intervals and samples were analysed for deuterium concentrations by laser spectroscopy to develop breakthrough curves. The outcome of experiments are the series of measured water fluxes, pressure heads and temperatures ready for inverse modelling by dual permeability. The saturated hydraulic conductivity of soil columns was higher in the case of higher temperature of flowing water. The change was however not proportional to Ksat change induced by temperature change of viscosity only.

Numerical investigation for formability of aluminum 6016 alloy under non-isothermal warm forming process

NASA Astrophysics Data System (ADS)

Hu, P.; Dai, M. H.; Ying, L.; Shi, D. Y.; Zhao, K. M.; Lu, J. D.

2013-05-01

The warm forming technology of aluminum alloy has attracted attention from worldwide automotive engineering sector in recent years, with which the complex geometry parts can be realized at elevated temperature. A non-isothermal warm forming process for the heat treatable aluminum can quickly carry out its application on traditional production line by adding a furnace to heat up the aluminum alloy sheet. The 6000 aluminum alloy was investigated by numerical simulation and experiment using the Nakajima test model in this paper. A modified Fields-Backofen model was introduced into numerical simulation process to describe the thermo-mechanical flow behavior of a 6000 series aluminum alloy. The experimental data was obtained by conducting thermal-mechanical uniaxial tensile experiment in temperatures range of 25˜400°C to guarantee the numerical simulation more accurate. The numerical simulation was implemented with LS_DYNA software in terms of coupled dynamic explicit method for investigating the effect of initial forming temperature and the Binder Holder Force (BHF), which are critical process parameters in non-isothermal warm forming. The results showed that the optimal initial forming temperature range was 300°C˜350°C. By means of conducting numerical simulation in deep drawing box model, the forming window of BHF and temperature around the optimal initial forming temperature (275°, 300° and 325°) are investigated, which can provide guidance to actual experiment.

Charge Transport in Nonaqueous Liquid Electrolytes: A Paradigm Shift

DTIC Science & Technology

2015-05-18

that provide inadequate descriptions of experimental data, often using empirical equations whose fitting parameters have no physical significance...provide inadequate descriptions of experimental data, often using empirical equations whose fitting parameters have no physical significance...Ea The hydrodynamic model, utilizing the Stokes equation describes isothermal conductivity, self-diffusion coefficient, and the dielectric

Surfactant Adsorption: A Revised Physical Chemistry Lab

ERIC Educational Resources Information Center

Bresler, Marc R.; Hagen, John P.

2008-01-01

Many physical chemistry lab courses include an experiment in which students measure surface tension as a function of surfactant concentration. In the traditional experiment, the data are fit to the Gibbs isotherm to determine the molar area for the surfactant, and the critical micelle concentration is used to calculate the Gibbs energy of micelle…

The Adiabatic Expansion of Gases and the Determination of Heat Capacity Ratios: A Physical Chemistry Experiment.

ERIC Educational Resources Information Center

Moore, William M.

1984-01-01

Describes the procedures and equipment for an experiment on the adiabatic expansion of gases suitable for demonstration and discussion in the physical chemical laboratory. The expansion produced shows how the process can change temperature and still return to a different location on an isotherm. (JN)

Energetic investigation of the adsorption process of CH4, C2H6 and N2 on activated carbon: Numerical and statistical physics treatment

NASA Astrophysics Data System (ADS)

Ben Torkia, Yosra; Ben Yahia, Manel; Khalfaoui, Mohamed; Al-Muhtaseb, Shaheen A.; Ben Lamine, Abdelmottaleb

2014-01-01

The adsorption energy distribution (AED) function of a commercial activated carbon (BDH-activated carbon) was investigated. For this purpose, the integral equation is derived by using a purely analytical statistical physics treatment. The description of the heterogeneity of the adsorbent is significantly clarified by defining the parameter N(E). This parameter represents the energetic density of the spatial density of the effectively occupied sites. To solve the integral equation, a numerical method was used based on an adequate algorithm. The Langmuir model was adopted as a local adsorption isotherm. This model is developed by using the grand canonical ensemble, which allows defining the physico-chemical parameters involved in the adsorption process. The AED function is estimated by a normal Gaussian function. This method is applied to the adsorption isotherms of nitrogen, methane and ethane at different temperatures. The development of the AED using a statistical physics treatment provides an explanation of the gas molecules behaviour during the adsorption process and gives new physical interpretations at microscopic levels.

Effect of plasticizer on moisture sorption isotherm of sugar palm (Arenga Pinnata) starch film

NASA Astrophysics Data System (ADS)

Jatmiko, Tri Hadi; Poeloengasih, Crescentiana D.; Prasetyo, Dwi Joko; Rosyida, Vita Taufika

2016-02-01

The effect of plasticizer type (glycerol, sorbitol) and plasticizer concentrations (30, 35, 40, 45% w/w polymer) on the moisture sorption isotherm characteristics of sugar palm (Arenga pinnata) starch films were investigated. Moisture affinity of sugar palm starch films was influenced by the plasticizer type and plasticizer concentration. The affinity of the glycerol plasticized film is stronger than that of sorbitol plasticized film. Sugar palm starch film with a higher concentration of glycerol absorbs more moisture with higher initial absorption rate than that of with sorbitol. Films with higher plasticizer concentration of glycerol and sorbitol show higher equilibrium moisture contents at the given relative humidity. The moisture sorption isotherm characteristic of sugar palm starch films can be described very well with the semi empirical 4 parameter Peleg's model.

The Origin of Scales and Scaling Laws in Star Formation

NASA Astrophysics Data System (ADS)

Guszejnov, David; Hopkins, Philip; Grudich, Michael

2018-01-01

Star formation is one of the key processes of cosmic evolution as it influences phenomena from the formation of galaxies to the formation of planets, and the development of life. Unfortunately, there is no comprehensive theory of star formation, despite intense effort on both the theoretical and observational sides, due to the large amount of complicated, non-linear physics involved (e.g. MHD, gravity, radiation). A possible approach is to formulate simple, easily testable models that allow us to draw a clear connection between phenomena and physical processes.In the first part of the talk I will focus on the origin of the IMF peak, the characteristic scale of stars. There is debate in the literature about whether the initial conditions of isothermal turbulence could set the IMF peak. Using detailed numerical simulations, I will demonstrate that not to be the case, the initial conditions are "forgotten" through the fragmentation cascade. Additional physics (e.g. feedback) is required to set the IMF peak.In the second part I will use simulated galaxies from the Feedback in Realistic Environments (FIRE) project to show that most star formation theories are unable to reproduce the near universal IMF peak of the Milky Way.Finally, I will present analytic arguments (supported by simulations) that a large number of observables (e.g. IMF slope) are the consequences of scale-free structure formation and are (to first order) unsuitable for differentiating between star formation theories.

Lattice Boltzmann method for weakly ionized isothermal plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Huayu; Ki, Hyungson

2007-12-15

In this paper, a lattice Boltzmann method (LBM) for weakly ionized isothermal plasmas is presented by introducing a rescaling scheme for the Boltzmann transport equation. Without using this rescaling, we found that the nondimensional relaxation time used in the LBM is too large and the LBM does not produce physically realistic results. The developed model was applied to the electrostatic wave problem and the diffusion process of singly ionized helium plasmas with a 1-3% degree of ionization under an electric field. The obtained results agree well with theoretical values.

Isothermal Dendritic Growth Experiment - Science, engineering, and hardware development for USMP space flights

NASA Technical Reports Server (NTRS)

Glicksman, M. E.; Hahn, R. C.; Koss, M. B.; Tirmizi, S. H.; Selleck, M. E.; Velosa, A.; Winsa, E.

1991-01-01

The Isothermal Dendritic Growth Experiment (IDGE) has been designed to provide microgravity data on dendritic growth for a critical test of theory. This paper updates progress on constructing a crystal growth chamber suitable for space flight. The IDGE chamber is constructed from glass and stainless steel and is hermetically sealed by electron beam welds and glass-metal seals. Initial tests of the chambers sample's melting point plateau show that the new chamber design is capable of preserving the 99.9995 percent purity of succinonitrile. Dendrite growth can be initiated in the center of the IDGE chamber by means of thermo-electric coolers and a capillary injector tube (stinger). The new IDGE chamber is ready for fully integrated tests with the prototype IDGE engineering hardware at NASA's Lewis Research Center.

Novel One-Tube-One-Step Real-Time Methodology for Rapid Transcriptomic Biomarker Detection: Signal Amplification by Ternary Initiation Complexes.

PubMed

Fujita, Hiroto; Kataoka, Yuka; Tobita, Seiji; Kuwahara, Masayasu; Sugimoto, Naoki

2016-07-19

We have developed a novel RNA detection method, termed signal amplification by ternary initiation complexes (SATIC), in which an analyte sample is simply mixed with the relevant reagents and allowed to stand for a short time under isothermal conditions (37 °C). The advantage of the technique is that there is no requirement for (i) heat annealing, (ii) thermal cycling during the reaction, (iii) a reverse transcription step, or (iv) enzymatic or mechanical fragmentation of the target RNA. SATIC involves the formation of a ternary initiation complex between the target RNA, a circular DNA template, and a DNA primer, followed by rolling circle amplification (RCA) to generate multiple copies of G-quadruplex (G4) on a long DNA strand like beads on a string. The G4s can be specifically fluorescence-stained with N(3)-hydroxyethyl thioflavin T (ThT-HE), which emits weakly with single- and double-stranded RNA/DNA but strongly with parallel G4s. An improved dual SATIC system, which involves the formation of two different ternary initiation complexes in the RCA process, exhibited a wide quantitative detection range of 1-5000 pM. Furthermore, this enabled visual observation-based RNA detection, which is more rapid and convenient than conventional isothermal methods, such as reverse transcription-loop-mediated isothermal amplification, signal mediated amplification of RNA technology, and RNA-primed rolling circle amplification. Thus, SATIC methodology may serve as an on-site and real-time measurement technique for transcriptomic biomarkers for various diseases.

Biosorption of Cu(II) from aqueous solutions by mimosa tannin gel.

PubMed

Sengil, I Ayhan; Ozacar, Mahmut

2008-09-15

The biosorption of Cu(II) from aqueous solutions by mimosa tannin resin (MTR) 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 Langmiur isotherm. The experimental data were analysed using four sorption kinetic models -- the pseudo-first- and second-order equations, and the Elovich and the intraparticle diffusion equation -- to determine the best fit equation for the biosorption of copper ions onto mimosa 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. Thermodynamic parameters such as the entropy change, enthalpy change and Gibb's free energy change were found out to be 153.0 J mol(-1)K(-1), 42.09 kJ mol(-1) and -2.47 kJ mol(-1), respectively.

Adsorption of methyl orange from aqueous solution using chitosan/diatomite composite.

PubMed

Zhao, Peng; Zhang, Runhu; Wang, Jianglin

2017-04-01

A novel chitosan/diatomite composite was prepared by a simple mixture in the mass ratio to remove methyl orange (MO) from aqueous media in this study. The composite adsorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy analysis. The parameters to influence the adsorption of MO were studied under such conditions as kinetics, adsorption isotherm, pH effect, and thermodynamics. The results revealed that adsorption of MO was initially rapid and the equilibrium time was reached after 40 min. The optimal value of the pH was 5.0 for better adsorption. The equilibrium data were well fitted to the Langmuir isotherm compared to the Freundlich isotherm, and exhibited the highest capacity and a removal rate of 88.37% under an initial dye concentration of 50 mg/L. The kinetic data were well described by the pseudo-second order model. The thermodynamic calculations revealed that the sorption was viable, spontaneous, and exothermic under the conditions studied. In addition, the chitosan/diatomite composite had good adsorption and desorption performance with respect to reusability after six cycles. These results showed that the chitosan/diatomite could be considered as a potential adsorbent for the removal of MO in aqueous solution.

Isolation and identification of Trichoderma harzianum from groundwater: An effective biosorbent for defluoridation of groundwater.

PubMed

Koshle, Shalini; Mahesh, S; Swamy, S Nanjunda

2016-01-01

The ability of non-viable form of Trichoderma harzianum, isolated from fluoride rich groundwater, was investigated as biosorbent for defluoridation of groundwater. Biosorption experiments were carried out at laboratory scale for removal of fluoride from groundwater. Significant effect of operational parameters on fluoride biosorption using Trichoderma harzianum as biosorbent was evaluated by varying operational parameters such as: initial fluoride concentration (2-8 mgl(-1)), biosorbent dose (0.4-1.6g/100ml), groundwater pH (6-10), temperature (30-50 degrees C) and biosorption time (30-120 min). The fluoride adsorption isotherms were modeled by Langmuir and Freundlich isotherms. Our result showed that fluoride biosorption, significantly increased with increase in groundwater pH, biosorbent dose, temperature and biosorption time, whereas increase in initial fluoride concentration reduced fluoride removal. The fluoride biosorption was rapid and maximum fluoride uptake was attained with 1.6g 100ml(-1) biosorbent within 60 min. Optimal pH 10 and temperature 50 degrees C gave maximum defluoridation efficiency. Freundlich isotherm fits well for defluoridation of groundwater using Trichoderma harzianum as biosorbent which indicated that biosorbent surface sites were heterogeneous in nature and fitted into heterogeneous site binding model.

[Application of classical isothermal adsorption models in heavy metal ions/ diatomite system and related problems].

PubMed

Zhu, Jian; Wu, Qing-Ding; Wang, Ping; Li, Ke-Lin; Lei, Ming-Jing; Zhang, Wei-Li

2013-11-01

In order to fully understand adsorption nature of Cu2+, Zn2+, Pb2+, Cd2+, Mn2+, Fe3+ onto natural diatomite, and to find problems of classical isothermal adsorption models' application in liquid/solid system, a series of isothermal adsorption tests were conducted. As results indicate, the most suitable isotherm models for describing adsorption of Pb2+, Cd2+, Cu2+, Zn2+, Mn2+, Fe3+ onto natural diatomite are Tenkin, Tenkin, Langmuir, Tenkin, Freundlich and Freundlich, respectively, the adsorption of each ion onto natural diatomite is mainly a physical process, and the adsorption reaction is favorable. It also can be found that, when using classical isothermal adsorption models to fit the experimental data in liquid/solid system, the equilibrium adsorption amount q(e) is not a single function of ion equilibrium concentration c(e), while is a function of two variables, namely c(e) and the adsorbent concentration W0, q(e) only depends on c(e)/W(0). Results also show that the classical isothermal adsorption models have a significant adsorbent effect, and their parameter values are unstable, the simulation values of parameter differ greatly from the measured values, which is unhelpful for practical use. The tests prove that four-adsorption-components model can be used for describing adsorption behavior of single ion in nature diatomite-liquid system, its parameters k and q(m) have constant values, which is favorable for practical quantitative calculation in a given system.

Analysis of form deviation in non-isothermal glass molding

NASA Astrophysics Data System (ADS)

Kreilkamp, H.; Grunwald, T.; Dambon, O.; Klocke, F.

2018-02-01

Especially in the market of sensors, LED lighting and medical technologies, there is a growing demand for precise yet low-cost glass optics. This demand poses a major challenge for glass manufacturers who are confronted with the challenge arising from the trend towards ever-higher levels of precision combined with immense pressure on market prices. Since current manufacturing technologies especially grinding and polishing as well as Precision Glass Molding (PGM) are not able to achieve the desired production costs, glass manufacturers are looking for alternative technologies. Non-isothermal Glass Molding (NGM) has been shown to have a big potential for low-cost mass manufacturing of complex glass optics. However, the biggest drawback of this technology at the moment is the limited accuracy of the manufactured glass optics. This research is addressing the specific challenges of non-isothermal glass molding with respect to form deviation of molded glass optics. Based on empirical models, the influencing factors on form deviation in particular form accuracy, waviness and surface roughness will be discussed. A comparison with traditional isothermal glass molding processes (PGM) will point out the specific challenges of non-isothermal process conditions. Furthermore, the underlying physical principle leading to the formation of form deviations will be analyzed in detail with the help of numerical simulation. In this way, this research contributes to a better understanding of form deviations in non-isothermal glass molding and is an important step towards new applications demanding precise yet low-cost glass optics.

Digital Isothermal Quantification of Nucleic Acids via Simultaneous Chemical Initiation of Recombinase Polymerase Amplification Reactions on SlipChip

PubMed Central

Shen, Feng; Davydova, Elena K.; Du, Wenbin; Kreutz, Jason E.; Piepenburg, Olaf; Ismagilov, Rustem F.

2011-01-01

In this paper, digital quantitative detection of nucleic acids was achieved at the single-molecule level by chemical initiation of over one thousand sequence-specific, nanoliter, isothermal amplification reactions in parallel. Digital polymerase chain reaction (digital PCR), a method used for quantification of nucleic acids, counts the presence or absence of amplification of individual molecules. However it still requires temperature cycling, which is undesirable under resource-limited conditions. This makes isothermal methods for nucleic acid amplification, such as recombinase polymerase amplification (RPA), more attractive. A microfluidic digital RPA SlipChip is described here for simultaneous initiation of over one thousand nL-scale RPA reactions by adding a chemical initiator to each reaction compartment with a simple slipping step after instrument-free pipette loading. Two designs of the SlipChip, two-step slipping and one-step slipping, were validated using digital RPA. By using the digital RPA SlipChip, false positive results from pre-initiation of the RPA amplification reaction before incubation were eliminated. End-point fluorescence readout was used for “yes or no” digital quantification. The performance of digital RPA in a SlipChip was validated by amplifying and counting single molecules of the target nucleic acid, Methicillin-resistant Staphylococcus aureus (MRSA) genomic DNA. The digital RPA on SlipChip was also tolerant to fluctuations of the incubation temperature (37–42 °C), and its performance was comparable to digital PCR on the same SlipChip design. The digital RPA SlipChip provides a simple method to quantify nucleic acids without requiring thermal cycling or kinetic measurements, with potential applications in diagnostics and environmental monitoring under resource-limited settings. The ability to initiate thousands of chemical reactions in parallel on the nanoliter scale using solvent-resistant glass devices is likely to be useful for a broader range of applications. PMID:21476587

Isotherm Sensor Calibration Program for Mars Science Laboratory Heat Shield Flight Data Analysis

NASA Technical Reports Server (NTRS)

Santos, Jose A.; Oishi, Tomo; Martinez, Ed R.

2011-01-01

Seven instrumented sensor plugs were installed on the Mars Science Laboratory heat shield in December 2008 as part of the Mars Science Laboratory Entry, Descent, and Landing Instrumentation (MEDLI) project. These sensor plugs contain four in-depth thermocouples and one Hollow aErothermal Ablation and Temperature (HEAT) sensor. The HEAT sensor follows the time progression of a 700 C isotherm through the thickness of a thermal protection system (TPS) material. The data can be used to infer char depth and, when analyzed in conjunction with the thermocouple data, the thermal gradient through the TPS material can also be determined. However, the uncertainty on the isotherm value is not well defined. To address this uncertainty, a team at NASA Ames Research Center is carrying out a HEAT sensor calibration test program. The scope of this test program is described, and initial results from experiments conducted in the laboratory to study the isotherm temperature of the HEAT sensor are presented. Data from the laboratory tests indicate an isotherm temperature of 720 C 60 C. An overview of near term arc jet testing is also given, including preliminary data from 30.48cm 30.48cm PICA panels instrumented with two MEDLI sensor plugs and tested in the NASA Ames Panel Test Facility. Forward work includes analysis of the arc jet test data, including an evaluation of the isotherm value based on the instant in time when it reaches a thermocouple depth.

Chemiluminescence as a condition monitoring method for thermal aging and lifetime prediction of an HTPB elastomer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillen, Kenneth Todd; Minier, Leanna M. G.; Celina, Mathias C.

Chemiluminescence (CL) has been applied as a condition monitoring technique to assess aging related changes in a hydroxyl-terminated-polybutadiene based polyurethane elastomer. Initial thermal aging of this polymer was conducted between 110 and 50 C. Two CL methods were applied to examine the degradative changes that had occurred in these aged samples: isothermal 'wear-out' experiments under oxygen yielding initial CL intensity and 'wear-out' time data, and temperature ramp experiments under inert conditions as a measure of previously accumulated hydroperoxides or other reactive species. The sensitivities of these CL features to prior aging exposure of the polymer were evaluated on the basismore » of qualifying this method as a quick screening technique for quantification of degradation levels. Both the techniques yielded data representing the aging trends in this material via correlation with mechanical property changes. Initial CL rates from the isothermal experiments are the most sensitive and suitable approach for documenting material changes during the early part of thermal aging.« less

Adsorption of hexavalent chromium onto sisal pulp/polypyrrole composites

NASA Astrophysics Data System (ADS)

Tan, Y. Y.; Wei, C.; Gong, Y. Y.; Du, L. L.

2017-02-01

Sisal pulp/polypyrrole composites(SP/PPy) utilized for the removal of hexavalent chromium [Cr(VI)] from wastewater, were prepared via in-situ chemical oxidation polymerization approach. The structure and morphology of the SP/PPy were analyzed by polarizing optical microscopy (POM), field-emission scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the results indicated SP could be efficient dispersion of PPy. The hexavalent chromium adsorption results indicate adsorption capacity of the SP/PPy were dependent on the initial pH, with an optimum pH of 2.0. The sorption kinetic data fitted well to the pseudo-second order model and isotherm data fitted well to the Langmuir isotherm model. The maximum adsorption capacity determined from the Langmuir isotherm is 336.70 mg/g at 25° C.

Micromechanisms of thermomechanical fatigue: A comparison with isothermal fatigue

NASA Technical Reports Server (NTRS)

Bill, R. C.

1986-01-01

Thermomechanical Fatigue (TMF) experiments were conducted on Mar-M 200, B-1900, and PWA-1480 (single crystals) over temperature ranges representative of gas turbine airfoil environments. The results were examined from both a phenomenological basis and a micromechanical basis. Depending on constituents present in the superalloy system, certain micromechanisms dominated the crack initiation process and significantly influenced the TMF lives as well as sensitivity of the material to the type TMF cycle imposed. For instance, high temperature cracking around grain boundary carbides in Mar-M 200 resulted in short in-phase TMF lives compared to either out-of-phase or isothermal lives. In single crystal PWA-1480, the type of coating applied was seen to be the controlling factor in determining sensitivity to the type of TMF cycle imposed. Micromechanisms of deformation were observed over the temperature range of interest to the TMF cycles, and provided some insight as to the differences between TMF damage mechanisms and isothermal damage mechanisms. Finally, the applicability of various life prediction models to TMF results was reviewed. Current life prediction models based on isothermal data must be modified before being generally applied to TMF.

Effect of Prior Athermal Martensite on the Isothermal Transformation Kinetics Below M s in a Low-C High-Si Steel

NASA Astrophysics Data System (ADS)

Navarro-López, A.; Sietsma, J.; Santofimia, M. J.

2016-03-01

Thermomechanical processing of Advanced Multiphase High Strength Steels often includes isothermal treatments around the martensite start temperature ( M s). It has been reported that the presence of martensite formed prior to these isothermal treatments accelerates the kinetics of the subsequent transformation. This kinetic effect is commonly attributed to the creation of potential nucleation sites at martensite-austenite interfaces. The aim of this study is to determine qualitatively and quantitatively the effect of a small volume fraction of martensite on the nucleation kinetics of the subsequent transformation. For this purpose, dilatometry experiments were performed at different temperatures above and below the M s temperature for athermal martensite in a low-carbon high-silicon steel. Microstructural analysis led to the identification of the isothermal decomposition product formed above and below M s as bainitic ferrite. The analysis of the transformation processes demonstrated that the initial stage of formation of bainitic ferrite at heat treatments below M s is at least two orders of magnitude faster than above M s due to the presence of martensite.

Adsorption of Methylene Blue, Bromophenol Blue, and Coomassie Brilliant Blue by α-chitin nanoparticles

PubMed Central

Dhananasekaran, Solairaj; Palanivel, Rameshthangam; Pappu, Srinivasan

2015-01-01

Expelling of dyestuff into water resource system causes major thread to the environment. Adsorption is the cost effective and potential method to remove the dyes from the effluents. Therefore, an attempt was made to study the adsorption of dyestuff (Methylene Blue (MB), Bromophenol Blue (BPB) and Coomassie Brilliant Blue (CBB)) by α-chitin nanoparticles (CNP) prepared from Penaeus monodon (Fabricius, 1798) shell waste. On contrary to the most recognizable adsorption studies using chitin, this is the first study using unique nanoparticles of ⩽50 nm used for the dye adsorption process. The results showed that the adsorption process increased with increase in the concentration of CNP, contact time and temperature with the dyestuff, whereas the adsorption process decreased with increase in the initial dye concentration and strong acidic pH. The results from Fourier transform infrared (FTIR) spectroscopy confirmed that the interaction between dyestuff and CNP involved physical adsorption. The adsorption process obeys Langmuir isotherm (R2 values were 0.992, 0.999 and 0.992 for MB, BPB and CBB, and RL value lies between 0 and 1 for all the three dyes) and pseudo second order kinetics (R2 values were 0.996, 0.999 and 0.996 for MB, BPB and CBB) more effectively. The isotherm and kinetic models confirmed that CNP can be used as a suitable adsorbent material for the removal of dyestuff from effluents. PMID:26843977

Investigations of Heavy Metal Ion Sorption Using Nanocomposites of Iron-Modified Biochar

NASA Astrophysics Data System (ADS)

Kołodyńska, D.; Bąk, J.; Kozioł, M.; Pylypchuk, L. V.

2017-06-01

Magnetic biochar nanocomposites were obtained by modification of biochar by zero-valent iron. The article provides information on the impact of contact time, initial Cd(II), Co(II), Zn(II), and Pb(II) ion concentrations, dose of the sorbents, solution pH and temperature on the adsorption capacity. On the basis of experiments, it was found that the optimum parameters for the sorption process are phase contact time 360 min (after this time, the equilibrium of all concentrations is reached), the dose of sorbent equal to 5 g/dm3, pH 5 and the temperature 295 K. The values of parameters calculated from the kinetic models and isotherms present the best match to the pseudo second order and Langmuir isotherm models. The calculated thermodynamic parameters ΔH 0, ΔS 0 and ΔG 0 indicate that the sorption of heavy metal ions is an exothermic and spontaneous process as well as favoured at lower temperatures, suggesting the physical character of sorption. The solution of nitric acid(V) at the concentration 0.1 mol/dm3 was the best acidic desorbing agent used for regeneration of metal-loaded magnetic sorbents. The physicochemical properties of synthesized composites were characterized by FTIR, SEM, XRD, XPS and TG analyses. The point characteristics of the double layer for biochar pHPZC and pHIEP were designated.

Adsorption of anionic surfactants from aqueous solution by high content of primary amino crosslinked chitosan microspheres.

PubMed

Zhang, Caihong; Wen, Haifeng; Huang, Yingying; Shi, Wenjian

2017-04-01

High content of primary amino crosslinked chitosan microspheres (ACCMs) were synthesized and characterized with IR, XRD and SEM technologies. Subsequently, ACCMs were adopted to adsorb three common anionic surfactants from aqueous solution: sodium dodecyl benzene sulfonate (SDBS), sodium lauryl sulfate (SLS), and sodium dodecyl sulfonate (SDS). The adsorption performances were evaluated based on different variables such as the pH, contact time, temperature and initial concentration of the anionic surfactants. Moreover, the adsorption were investigated with kinetic models, equilibrium isotherms and thermodynamic models. The experimental results indicated that the adsorption processes were fitted very well with a pseudo-second-order model. The adsorption isotherms could be better described by Langmuir model rather than Freundlich model. The adsorption of SDBS was a spontaneous, exothermic process. While the adsorption of SLS and SDS were spontaneous, endothermic. The adsorption processes were complex physical-chemistry adsorption models, which are dominated by physisorption. Furthermore, this study found that the material had strong absorption abilities for anionic surfactants, the saturation adsorption capacity of ACCMs were 1220mg/g for SDBS, 888mg/g for SLS, and 825mg/g for SDS at pH 3.0 and 298K, respectively. The adsorption capacity was reduced only 5.7% after 8 cycles of the adsorption-desorption processes. Copyright © 2017 Elsevier B.V. All rights reserved.

Isothermal dendritic growth experiment: Science, engineering, and hardware development for USMP space flights

NASA Astrophysics Data System (ADS)

Glicksman, M. E.; Hahn, R. C.; Koss, M. B.; Tirmizi, S. H.; Selleck, M. E.; Velosa, A.; Winsa, E.

The Isothermal Dendritic Growth Experiment (IDGE) has been designed to provide microgravity data on dendritic growth for a critical test of theory. This paper updates our progress on constructing a crystal growth chamber suitable for space flight. The IDGE chamber is constructed from glass and stainless steel and is hermetically sealed by electron beam welds and glass-metal seals. Initial tests of the chambers sample's melting point plateau show that the new chamber design is capable of preserving the 99.9995 pct purity of succinonitrile (SCN). One can initiate dendrite growth in the center of the IDGE chamber by means of thermo-electric coolers and a capillary injector tube (stinger). The new IDGE chamber is ready for fully integrated tests with the prototype IDGE engineering hardware at NASA's Lewis Research Center.

Kinetic and equilibrium isotherm studies for the adsorptive removal of Brilliant Green dye from aqueous solution by rice husk ash.

PubMed

Mane, Venkat S; Deo Mall, Indra; Chandra Srivastava, Vimal

2007-09-01

The present study deals with the adsorption of Brilliant Green (BG) on rice husk ash (RHA). RHA is a solid waste obtained from the particulate collection equipment attached to the flue gas lines of rice husk fired boilers. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH0), contact time, adsorbent dose and initial concentration (C0) on the removal of BG. Optimum conditions for BG removal were found to be pH0 approximately 3.0, adsorbent dose approximately 6 g L(-1) of solution and equilibrium time approximately 5 h for the C0 range of 50-300 mg L(-1). Adsorption of BG followed pseudo-second-order kinetics. Intra-particle diffusion does not seem to control the BG removal process. Equilibrium isotherms for the adsorption of BG on RHA were analyzed by Freundlich, Langmuir, Redlich-Peterson (R-P), Dubnin-Radushkevich (D-R), and Temkin isotherm models using a non-linear regression technique. Langmuir and R-P isotherms were found to best represent the data for BG adsorption onto RHA. Adsorption of BG on RHA is favourably influenced by an increase in the temperature of the operation. Values of the change in entropy (DeltaS0) and heat of adsorption (DeltaH0) for BG adsorption on RHA were positive. The high negative value of change in Gibbs free energy (DeltaG0) indicates the feasible and spontaneous adsorption of BG on RHA.

Differential heat of adsorption of water vapor on silicified microcrystalline cellulose (SMCC): an investigation using isothermal microcalorimetry.

PubMed

Qian, Ken K; Bogner, Robin H

2011-01-01

A novel dual-shaft configuration in isothermal microcalorimetry was developed to study the interaction of water vapor with pharmaceutical excipients. An instrument performance test is suggested to validate the experimental data. Reliable experimental results can be collected using a single perfusion shaft; however, there was limitation of the dual-shaft configuration, which resulted deviation in the experimental results. A periodic performance test is recommended. Silicified microcrystalline cellulose (SMCC) was used as a model system to study the interaction using the dual-shaft method. Enthalpy of water vapor adsorption on SMCC was determined and compared to literature data. The data collected using the dual-shaft configuration did not reflect the actual physical system. The deviation was most likely due to the lack of flow control caused by viscous resistance. The enthalpy of adsorption was then calculated using isothermal microcalorimetry coupled with a dynamic vapor sorption apparatus. The results, -55 kJ/mol at low relative humidity (RH) to -22 kJ/mol at high RH, were consistent with the physical phenomenon of water vapor adsorption. Enthalpy of adsorption showed surface heterogeneity of SMCC and suggested multilayer condensation of water at approximately 60% RH. However, at high RH, the results showed the moisture-excipient interaction can be more complex than the proposed mechanism.

Chemistry in dynamically evolving clouds

NASA Technical Reports Server (NTRS)

Tarafdar, S. P.; Prasad, S. S.; Huntress, W. T., Jr.; Villere, K. R.; Black, D. C.

1985-01-01

A unified model of chemical and dynamical evolution of isolated, initially diffuse and quiescent interstellar clouds is presented. The model uses a semiempirically derived dependence of the observed cloud temperatures on the visual extinction and density. Even low-mass, low-density, diffuse clouds can collapse in this model, because the inward pressure gradient force assists gravitational contraction. In contrast, previous isothermal collapse models required the low-mass diffuse clouds to be unrealistically cold before gravitational contraction could start. Theoretically predicted dependences of the column densities of various atoms and molecules, such as C and CO, on visual extinction in diffuse clouds are in accord with observations. Similarly, the predicted dependences of the fractional abundances of various chemical species (e.g., CO, H2CO, HCN, HCO(+)) on the total hydrogen density in the core of the dense clouds also agree with observations reported to date in the literature. Compared with previous models of interstellar chemistry, the present model has the potential to explain the wide spectrum of chemical and physical properties of both diffuse and dense clouds with a common formalism employing only a few simple initial conditions.

Magnetic Ghosts: Mineral Magnetic Measurements On Roman and Anglo-saxon Graves

NASA Astrophysics Data System (ADS)

Linford, N.

The location of inhumations, in the absence of ferrous grave goods, often presents a considerable challenge to archaeological geophysics given the small physical size of the features and the slight contrast between the fill of the grave and the surround- ing subsoil. Even during excavation, the identification of graves may be complicated where site conditions do not favour the preservation of human skeletal remains and often only a subtle soil stain is likely to survive. A recent initiative in the United King- dom has seen the formation of the Buried Organic Matter Decomposition Integrated with Elemental Status (BODIES) research group, to examine the decomposition of organic artefacts in ancient graves with respect to localised changes in pH, redox po- tential and nutrient status. This paper presents initial results from a limited mineral magnetic study of two grave sites in an attempt to ascertain whether the decomposi- tion of organic remains may lead to a detectable magnetic signature within the soil. Results from a series of isothermal, hysteresis and magneto-thermal experiments will be presented together with surface magnetometer and topsoil susceptibility surveys.

Thermodynamic and kinetic studies on CO2 capture with Poly[VBTMA][Arg

NASA Astrophysics Data System (ADS)

Raja Shahrom, Maisara Shahrom; Wilfred, Cecilia Devi; Chong, Fai Kait

2018-05-01

This paper discusses the technologies for capturing CO2 from the natural gas using poly[VBTMA][Arg], a type of poly(ionic liquids) with an amino acid as the anion. The results revealed that the CO2 uptake increased from 3.23 mmol/g to 7.91 mmol/g at 1-10 bar, 298 K due to both chemical absorption and physical adsorption increments. Four adsorption isotherm models were applied to study the interaction between adsorbate and adsorbent to study the physical adsorption i.e. Freundlich, Langmuir, Dubinin Raduschkevich and Temkin isotherms at 298 K, 313 K and 333 K. Promising results were obtained that suggested the Freundlich model and the pseudo-first order model are well fitted with the kinetic data at 298 K with a 0.9943 R2 value. This study has provided empirical evidence to the current body of knowledge pertaining to CO2 capture technologies.

On Riemann solvers and kinetic relations for isothermal two-phase flows with surface tension

NASA Astrophysics Data System (ADS)

Rohde, Christian; Zeiler, Christoph

2018-06-01

We consider a sharp interface approach for the inviscid isothermal dynamics of compressible two-phase flow that accounts for phase transition and surface tension effects. Kinetic relations are frequently used to fix the mass exchange and entropy dissipation rate across the interface. The complete unidirectional dynamics can then be understood by solving generalized two-phase Riemann problems. We present new well-posedness theorems for the Riemann problem and corresponding computable Riemann solvers that cover quite general equations of state, metastable input data and curvature effects. The new Riemann solver is used to validate different kinetic relations on physically relevant problems including a comparison with experimental data. Riemann solvers are building blocks for many numerical schemes that are used to track interfaces in two-phase flow. It is shown that the new Riemann solver enables reliable and efficient computations for physical situations that could not be treated before.

Modeling of boldine alkaloid adsorption onto pure and propyl-sulfonic acid-modified mesoporous silicas. A comparative study.

PubMed

Geszke-Moritz, Małgorzata; Moritz, Michał

2016-12-01

The present study deals with the adsorption of boldine onto pure and propyl-sulfonic acid-functionalized SBA-15, SBA-16 and mesocellular foam (MCF) materials. Siliceous adsorbents were characterized by nitrogen sorption analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherms. Moreover, the Dubinin-Radushkevich and Dubinin-Astakhov isotherm models based on the Polanyi adsorption potential were employed. The latter was calculated using two alternative formulas including solubility-normalized (S-model) and empirical C-model. In order to find the best-fit isotherm, both linear regression and nonlinear fitting analysis were carried out. The Dubinin-Astakhov (S-model) isotherm revealed the best fit to the experimental points for adsorption of boldine onto pure mesoporous materials using both linear and nonlinear fitting analysis. Meanwhile, the process of boldine sorption onto modified silicas was described the best by the Langmuir and Temkin isotherms using linear regression and nonlinear fitting analysis, respectively. The values of adsorption energy (below 8kJ/mol) indicate the physical nature of boldine adsorption onto unmodified silicas whereas the ionic interactions seem to be the main force of alkaloid adsorption onto functionalized sorbents (energy of adsorption above 8kJ/mol). Copyright © 2016 Elsevier B.V. All rights reserved.

Transformation Stasis Phenomenon of Bainite Formation in Low-Carbon, Multicomponent Alloyed Steel

NASA Astrophysics Data System (ADS)

Lan, Liangyun; Kong, Xiangwei

2017-11-01

The transformation stasis phenomenon of bainite formation in low-carbon steel was detected using a high-resolution dilatometer. The phenomenon occurred at different stages for different isothermal temperatures. In combination with microstructural observation, the calculated overall activation energy of transformation and interface migration velocity shed new light on the cause of formation of the stasis phenomenon. The temporary stasis formed at the initial stage of phase transformation for high isothermal temperature was attributed to the drag effect of substitutional atoms, which leads to low-interface migration velocity and large overall activation energy.

Equilibrium isotherm and kinetic studies for the simultaneous removal of phenol and cyanide by use of S. odorifera (MTCC 5700) immobilized on coconut shell activated carbon

NASA Astrophysics Data System (ADS)

Singh, Neetu; Balomajumder, Chandrajit

2017-10-01

In this study, simultaneous removal of phenol and cyanide by a microorganism S. odorifera (MTCC 5700) immobilized onto coconut shell activated carbon surface (CSAC) was studied in batch reactor from mono and binary component aqueous solution. Activated carbon was derived from coconut shell by chemical activation method. Ferric chloride (Fecl3), used as surface modification agents was applied to biomass. Optimum biosorption conditions were obtained as a function of biosorbent dosage, pH, temperature, contact time and initial phenol and cyanide concentration. To define the equilibrium isotherms, experimental data were analyzed by five mono component isotherm and six binary component isotherm models. The higher uptake capacity of phenol and cyanide onto CSAC biosorbent surface was 450.02 and 2.58 mg/g, respectively. Nonlinear regression analysis was used for determining the best fit model on the basis of error functions and also for calculating the parameters involved in kinetic and isotherm models. The kinetic study results revealed that Fractal-like mixed first second order model and Brouser-Weron-Sototlongo models for phenol and cyanide were capable to offer accurate explanation of biosorption kinetic. According to the experimental data results, CSAC with immobilization of bacterium S. odorifera (MTCC 5700) seems to be an alternative and effective biosorbent for the elimination of phenol and cyanide from binary component aqueous solution.

Trihalomethane formation potential of aquatic and terrestrial fulvic and humic acids: Sorption on activated carbon.

PubMed

Abouleish, Mohamed Y Z; Wells, Martha J M

2015-07-15

Humic substances (HSs) are precursors for the formation of hazardous disinfection by-products (DBPs) during chlorination of water. Various surrogate parameters have been used to investigate the generation of DBPs by HS precursors and the removal of these precursors by activated carbon treatment. Dissolved organic carbon (DOC)- and ultraviolet absorbance (UVA254)-based isotherms are commonly reported and presumed to be good predictors of the trihalomethane formation potential (THMFP). However, THMFP-based isotherms are rarely published such that the three types of parameters have not been compared directly. Batch equilibrium experiments on activated carbon were used to generate constant-initial-concentration sorption isotherms for well-characterized samples obtained from the International Humic Substances Society (IHSS). HSs representing type (fulvic acid [FA], humic acid [HA]), origin (aquatic, terrestrial), and geographical source (Nordic, Suwannee, Peat, Soil) were examined at pH6 and pH9. THMFP-based isotherms were generated and compared to determine if DOC- and UVA254-based isotherms were good predictors of the THMFP. The sorption process depended on the composition of the HSs and the chemical nature of the activated carbon, both of which were influenced by pH. Activated carbon removal of THM-precursors was pH- and HS-dependent. In some instances, the THMFP existed after UVA254 was depleted. Copyright © 2015 Elsevier B.V. All rights reserved.

Digital isothermal quantification of nucleic acids via simultaneous chemical initiation of recombinase polymerase amplification reactions on SlipChip.

PubMed

Shen, Feng; Davydova, Elena K; Du, Wenbin; Kreutz, Jason E; Piepenburg, Olaf; Ismagilov, Rustem F

2011-05-01

In this paper, digital quantitative detection of nucleic acids was achieved at the single-molecule level by chemical initiation of over one thousand sequence-specific, nanoliter isothermal amplification reactions in parallel. Digital polymerase chain reaction (digital PCR), a method used for quantification of nucleic acids, counts the presence or absence of amplification of individual molecules. However, it still requires temperature cycling, which is undesirable under resource-limited conditions. This makes isothermal methods for nucleic acid amplification, such as recombinase polymerase amplification (RPA), more attractive. A microfluidic digital RPA SlipChip is described here for simultaneous initiation of over one thousand nL-scale RPA reactions by adding a chemical initiator to each reaction compartment with a simple slipping step after instrument-free pipet loading. Two designs of the SlipChip, two-step slipping and one-step slipping, were validated using digital RPA. By using the digital RPA SlipChip, false-positive results from preinitiation of the RPA amplification reaction before incubation were eliminated. End point fluorescence readout was used for "yes or no" digital quantification. The performance of digital RPA in a SlipChip was validated by amplifying and counting single molecules of the target nucleic acid, methicillin-resistant Staphylococcus aureus (MRSA) genomic DNA. The digital RPA on SlipChip was also tolerant to fluctuations of the incubation temperature (37-42 °C), and its performance was comparable to digital PCR on the same SlipChip design. The digital RPA SlipChip provides a simple method to quantify nucleic acids without requiring thermal cycling or kinetic measurements, with potential applications in diagnostics and environmental monitoring under resource-limited settings. The ability to initiate thousands of chemical reactions in parallel on the nanoliter scale using solvent-resistant glass devices is likely to be useful for a broader range of applications.

Electron cyclotron thruster new modeling results preparation for initial experiments

NASA Technical Reports Server (NTRS)

Hooper, E. Bickford

1993-01-01

The following topics are discussed: a whistler-based electron cyclotron resonance heating (ECRH) thruster; cross-field coupling in the helicon approximation; wave propagation; wave structure; plasma density; wave absorption; the electron distribution function; isothermal and adiabatic plasma flow; ECRH thruster modeling; a PIC code model; electron temperature; electron energy; and initial experimental tests. The discussion is presented in vugraph form.

BTEX and MTBE adsorption onto raw and thermally modified diatomite.

PubMed

Aivalioti, Maria; Vamvasakis, Ioannis; Gidarakos, Evangelos

2010-06-15

The removal of BTEX (benzene, toluene, ethyl-benzene and xylenes) and MTBE (methyl tertiary butyl ether) from aqueous solution by raw (D(R)) and thermally modified diatomite at 550, 750 and 950 degrees C (D(550), D(750) and D(950) respectively) was studied. Physical characteristics of both raw and modified diatomite such as specific surface, pore volume distribution, porosity and pH(solution) were determined, indicating important structural changes in the modified diatomite, due to exposure to high temperatures. Both adsorption kinetic and isotherm experiments were carried out. The kinetics data proved a closer fit to the pseudo-second order model. Maximum values for the rate constant, k(2), were obtained for MTBE and benzene (48.9326 and 18.0996 g mg(-1)h(-1), respectively) in sample D(550). The isotherm data proved to fit the Freundlich model more closely, which produced values of the isotherm constant 1/n higher than one, indicating unfavorable adsorption. The highest adsorption capacity, calculated through the values of the isotherm constant k(F), was obtained for MTBE (48.42 mg kg(-1) (mg/L)(n)) in sample D(950). Copyright 2010 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, N.M.; Ghosh, T.K.; Hines, A.L.

Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of themore » isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer`s classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation.« less

Removal of cadmium ions from wastewater using innovative electronic waste-derived material.

PubMed

Xu, Meng; Hadi, Pejman; Chen, Guohua; McKay, Gordon

2014-05-30

Cadmium is a highly toxic heavy metal even at a trace level. In this study, a novel material derived from waste PCBs has been applied as an adsorbent to remove cadmium ions from aqueous solutions. The effects of various factors including contact time, initial cadmium ion concentration, pH and adsorbent dosage have been evaluated. The maximum uptake capacity of the newly derived material for cadmium ions has reached 2.1mmol/g at an initial pH 4. This value shows that this material can effectively remove cadmium ions from effluent. The equilibrium isotherm has been analyzed using several isotherm equations and is best described by the Redlich-Peterson model. Furthermore, different commercial adsorbent resins have been studied for comparison purposes. The results further confirm that this activated material is highly competitive with its commercial counterparts. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of dissolved Reactive red dye from aqueous phase onto activated carbon prepared from agricultural waste.

PubMed

Senthilkumaar, S; Kalaamani, P; Porkodi, K; Varadarajan, P R; Subburaam, C V

2006-09-01

The adsorption of Reactive red dye (RR) onto Coconut tree flower carbon (CFC) and Jute fibre carbon (JFC) from aqueous solution was investigated. Adsorption studies were carried out at different initial dye concentrations, initial solution pH and adsorbent doses. The kinetic studies were also conducted; the adsorption of Reactive red onto CFC and JFC followed pseudosecond-order rate equation. The effective diffusion coefficient was evaluated to establish the film diffusion mechanism. Quantitative removal of Reactive red dye was achieved at strongly acidic conditions for both the carbons studied. The adsorption isotherm data were fitted well to Langmuir isotherm and the adsorption capacity were found to be 181.9 and 200 mg/g for CFC and JFC, respectively. The overall rate of dye adsorption appeared to be controlled by chemisorption, in this case in accordance with poor desorption studies.

Improving lead adsorption through chemical modification of wheat straw by lactic acid

NASA Astrophysics Data System (ADS)

Mu, Ruimin; Wang, Minxiang; Bu, Qingwei; Liu, Dong; Zhao, Yanli

2018-01-01

This work describes the creation of a new cellulosic material derived from wheat straw modified by lactic acid for adsorption of lead in aqueous solution, called 0.3LANS (the concentration of the lactic acid were 0.3mol/L). Batch experiments were conducted to study the effects of initial pH value, contact time, adsorbent dose, initial concentration and temperature. Fourier transform infrared (FTIR), Elemental analysis, BET surface area and Scanning electron micrographs (SEM) analysis were used to investigate the chemical modification. Adsorption isotherm models namely, Langmuir, Freundlich were used to analyse the equilibrium data, and the Langmuir isotherm model provided the best correlation, means that the adsorption was chemical monolayer adsorption and the adsorption capacity qm was increased with increasing temperature, and reached 51.49mg/g for 0.3LANS at 35°C, showing adsorption was exothermic.

Effects of mechanical strain amplitude on the isothermal fatigue behavior of H13

NASA Astrophysics Data System (ADS)

Zeng, Yan; Zuo, Peng-peng; Wu, Xiao-chun; Xia, Shu-wen

2017-09-01

Isothermal fatigue (IF) tests were performed on H13 tool steel subjected to three different mechanical strain amplitudes at a constant temperature to determine the effects of mechanical strain amplitude on the microstructure of the steel samples. The samples' extent of damage after IF tests was compared by observation of their cracks and calculation of their damage parameters. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the microstructure of the samples. Cracks were observed to initiate at the surface because the strains and stresses there were the largest during thermal cycling. Mechanical strain accelerated the damage and softening of the steel. A larger mechanical strain caused greater deformation of the steel, which made the precipitated carbides easier to gather and grow along the deformation direction, possibly resulting in softening of the material or the initiation of cracks.

Coupled heat and silica transport associated with dike intrusion into sedimentary rock: effects on isotherm location and permeability evolution

NASA Astrophysics Data System (ADS)

Dutrow, Barbara L.; Travis, Bryan J.; Gable, Carl W.; Henry, Darrell J.

2001-11-01

An 11-meter-wide alkalic monchiquite dike recovered from the subsurface of Louisiana has produced a metasomatic aureole in the adjacent interbedded carbonate mudstones and siltstones. The asymmetric contact aureole, which extends nearly 6 m above and 4 m below the intrusion, contains the metamorphic minerals, diopside, pectolite, fluor-apophyllite, fluorite, and garnet. A series of coupled heat and mass transport calculations was undertaken to provide thermal constraints for the aureole, in the absence of robust geothermometric assemblages, and insights into accompanying mass transport associated with the sedimentary rock-dike system. Calculations were completed for systems with homogeneous, anisotropic, and layered permeability, κ. Transport, dissolution, and precipitation of silica were also incorporated into calculations. All systems modeled indicate that the thermal pulse waned in ∼3 yr with a return to background temperatures in ∼10 yr. Heat and fluid transport produce maximum temperature isotherms that are distinctly different in spatial extent and lateral variability for each numerical system. The homogeneous κ case produced isotherms that pinch and swell vertically above the dike and have large lateral variations, in contrast to the anisotropic κ case that produced a single large plume above the dike. The layered system κ case produced the most spatially extensive thermal aureole, unlike that recorded in the rocks. Addition of dissolved silica to the flow system significantly impacts the calculated transport of heat and fluid, primarily due to density changes that affect upwelling dynamics. Although precipitation and dissolution of SiO2 can affect flow through the feedback to permeability, κ changes were found to be minor for these system conditions. Where κ decreased, flow was refocused into higher κ zones, thus mitigating the κ differences over time. This negative feedback tends to defocus flow and provides a mechanism for lateral migration of plumes. Coupled heat and silica transport produces a complex isotherm geometry surrounding the intrusion due to formation of upwelling and downwelling plumes and lateral translation of plumes, leading to variability in the isotherm pattern that does not reflect the inherent heterogeneity of the initial material properties. Initial heterogeneities in κ are not a prerequisite for the development of a complicated flow and transport pattern. In addition, if isotherms reflect isograds, these calculations demonstrate that isograds may not form uniform structures with isograd boundaries characterized by their distance from the heat source.

Use of phase change materials during compressed air expansion for isothermal CAES plants

NASA Astrophysics Data System (ADS)

Castellani, B.; Presciutti, A.; Morini, E.; Filipponi, M.; Nicolini, A.; Rossi, F.

2017-11-01

Compressed air energy storage (CAES) plants are designed to store compressed air into a vessel or in an underground cavern and to expand it in an expansion turbine when energy demand is high. An innovative CAES configuration recently proposed is the isothermal process. Several methods to implement isothermal CAES configuration are under investigation. In this framework, the present paper deals with the experimental testing of phase change materials (PCM) during compressed air expansion phase. The experimental investigation was carried out by means of an apparatus constituted by a compression section, a steel pressure vessel, to which an expansion valve is connected. The initial internal absolute pressure was equal to 5 bar to avoid moisture condensation and the experimental tests were carried out with two paraffin-based PCM amounts (0.05 kg and 0.1 kg). Results show that the temperature change during air expansion decreases with increasing the PCM amount inside the vessel. With the use of PCM during expansions an increase of the expansion work occurs. The increase is included in the range from 9.3% to 18.2%. In every test there is an approach to the isothermal values, which represent the maximum theoretical value of the obtainable expansion work.

Adsorption kinetics of malachite green onto activated carbon prepared from Tunçbilek lignite.

PubMed

Onal, Y; Akmil-Başar, C; Eren, Didem; Sarici-Ozdemir, Cigdem; Depci, Tolga

2006-02-06

Adsorbent (T3K618) has been prepared from Tunçbilek lignite by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N2 adsorption isotherm. The N2 adsorption isotherm of malachite green on T3K618 is type I. The BET surface area of the adsorbent which was primarily contributed by micropores was determined 1000 m2/g. T3K618 was used to adsorb malachite green (MG) from an aqueous solution in a batch reactor. The effects of initial dye concentration, agitation time, initial pH and adsorption temperature have been studied. It was also found that the adsorption isotherm followed both Freundlich and Dubinin-Radushkevich models. However, the Freundlich gave a better fit to all adsorption isotherms than the Dubinin-Radushkevich. The kinetics of adsorption of MG has been tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Results show that the adsorption of MG from aqueous solution onto micropores T3K618 proceeds according to the pseudo-second-order model. The intraparticle diffusion of MG molecules within the carbon particles was identified to be the rate-limiting step. The adsorption of the MG was endothermic (DeltaH degrees = 6.55-62.37 kJ/mol) and was accompanied by an increase in entropy (DeltaS degrees = 74-223 J/mol K) and a decrease in mean value of Gibbs energy (DeltaG degrees = -6.48 to -10.32 kJ/mol) in the temperature range of 20-50 degrees C.

Kinetics of austenite-pearlite transformation in eutectoid carbon steel

NASA Astrophysics Data System (ADS)

Hawbolt, E. B.; Chau, B.; Brimacombe, J. K.

1983-09-01

The kinetics of the austenite-to-pearlite transformation have been measured under isothermal and continuous-cooling conditions on a eutectoid carbon (1080) steel using a diametral dilatometric technique. The isothermal transformation kinetics have been analyzed in terms of the Avrami Equation containing the two parameters n and b; the initiation of transformation was characterized by an empirically determined transformation-start time (tAv). The parameter n was found to be nearly constant; and neither n nor b was dependent on the cooling rate between T A1 and the test temperature. Continuous-cooling tests were performed with cooling rates ranging from 7.5 to 108 °C per second, and the initiation of transformation was determined. Comparison of this transformation-start time for different cooling rates with the measured slow cooling of a test coupon immersed in a salt bath indicates that, particularly at lower temperatures, the transformation in the traditional T-T-T test specimen may not be isothermal. The additivity rule was found to predict accurately the time taken, relative to tAv, to reach a given fraction of austenite transformed, even though there is some question that the isokinetic condition was met above 660 °C. However, the additivity rule does not hold for the pretransformation or incubation period, as originally proposed by Scheil, and seriously overestimates the incubation time. Application of the additivity rule to the prediction of transformation-finish time, based on transformation start at TA1, also leads to overestimates, but these are less serious. The isothermal parameters— n ( T), b ( T), and tAv ( T)—have been used to predict continuous-cooling transformation kinetics which are in close agreement with measurements at four cooling rates ranging from 7.5 to 64 °C per second.

Compatibility studies of acyclovir and lactose in physical mixtures and commercial tablets.

PubMed

Monajjemzadeh, Farnaz; Hassanzadeh, Davoud; Valizadeh, Hadi; Siahi-Shadbad, Mohammad R; Mojarrad, Javid Shahbazi; Robertson, Thomas A; Roberts, Michael S

2009-11-01

This study documents drug-excipient incompatibility studies of acyclovir in physical mixtures with lactose and in different tablet brands. Differential scanning calorimetry (DSC) was initially used to assess compatibility of mixtures. The Fourier-transform infrared (FTIR) spectrum was also compared with the spectra of pure drug and excipient. Although DSC results indicated incompatibility with lactose, FTIR spectra were mostly unmodified due to overlapping peaks. Samples of isothermally stressed physical mixture were stored at 95 degrees C for 24 h. The residual drug was monitored using a validated high-performance liquid chromatography (HPLC) assay and data fitting to solid-state kinetic models was performed. The drug loss kinetics followed a diffusion model. The aqueous mixture of drug and excipient was heated in order to prepare an adduct mixture. HPLC analysis revealed one extra peak that was fractionated and subsequently injected into the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) system. The MRM (Multiple Reaction Monitoring) chromatograms characterized the peak with molecular mass corresponding to an acyclovir-lactose Maillard reaction product. The presence of lactose in commercial tablets was checked using a new TLC method. Overall, the incompatibility of acyclovir with lactose was successfully evaluated using a combination of thermal methods and LC-MS/MS.

Isotherm and thermodynamic studies of Zn (II) adsorption on lignite and coconut shell-based activated carbon fiber.

PubMed

Shrestha, Sohan; Son, Guntae; Lee, Seung Hwan; Lee, Tae Gwan

2013-08-01

The Zn (II) adsorption capacity of lignite and coconut shell-based activated carbon fiber (ACF) was evaluated as a function of initial Zn (II) concentration, temperature and contact time in batch adsorption process in this study. Adsorption uptake increased with initial Zn (II) concentration and temperature. Optimal contact time for the adsorption of Zn (II) ions onto lignite and coconut shell-based ACF was found to be 50 min. Removal percentage decreased from 88.0% to 78.54% with the increment in initial Zn (II) concentration from 5 to 50 mg L(-1). Equilibrium data fit well with Langmuir-I isotherm indicating homogeneous monolayer coverage of Zn (II) ions on the adsorbent surface. Maximum monolayer adsorption capacity of Zn (II) ions on ACF was found to be 9.43 mg g(-1). Surface morphology and functionality of ACF prior to and after adsorption were characterized by electron microscopy and infrared spectroscopy. Various thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated. Copyright © 2013 Elsevier Ltd. All rights reserved.

Particle Image Velocimetry in an Isothermal and Exothermic High Speed Cavity (Postprint)

DTIC Science & Technology

2012-02-01

17 Oxides and Hydroxides of Aluminum, Alcoa Technical Paper No. 19, Revised...Karl Wefers and Chanakya Misra, Alcoa Laboratories, 1987. 18 CRC Handbook of Chemistry and Physics, David R. Lide, Ed. 80th Edition, CRC Press, Boca

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt vs Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property-in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

Tidal disruption of inviscid protoplanets

NASA Technical Reports Server (NTRS)

Boss, Alan P.; Cameron, A. G. W.; Benz, W.

1991-01-01

Roche showed that equilibrium is impossible for a small fluid body synchronously orbiting a primary within a critical radius now termed the Roche limit. Tidal disruption of orbitally unbound bodies is a potentially important process for planetary formation through collisional accumulation, because the area of the Roche limit is considerably larger then the physical cross section of a protoplanet. Several previous studies were made of dynamical tidal disruption and different models of disruption were proposed. Because of the limitation of these analytical models, we have used a smoothed particle hydrodynamics (SPH) code to model the tidal disruption process. The code is basically the same as the one used to model giant impacts; we simply choose impact parameters large enough to avoid collisions. The primary and secondary both have iron cores and silicate mantles, and are initially isothermal at a molten temperature. The conclusions based on the analytical and numerical models are summarized.

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt versus Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, Eugene E.; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

Adsorption of octylamine on titanium dioxide

NASA Astrophysics Data System (ADS)

Siwińska, Daria; Kołodziejczak-Radzimska, Agnieszka; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

2009-05-01

Processes of adsorption and desorption of a model active substance (octylamine) on the surface of unmodified titanium dioxide (E 171) have been performed. The effects of concentration of octylamine and time of the process on the character of adsorption have been studied and the efficiency of the adsorption/desorption has been determined. The samples obtained have been studied by X-ray diffraction. The nitrogen adsorption/desorption isotherms, particle size distribution and absorption capacities of water, dibutyl phthalate and paraffin oil have been determined. The efficiency of octylamine adsorption on the surface of the titanium dioxide has been found positively correlated with the concentration of octylamine in the initial solution. The desorption of octylamine has decreased with increasing concentration of this compound adsorbed. For octylamine in low concentrations the physical adsorption has been found to dominate, which is desirable when using TiO 2 in the production of pharmaceuticals.

Interactions at the mild steel acid solution interface in the presence of O-fumaryl-chitosan: Electrochemical and surface studies.

PubMed

Sangeetha, Y; Meenakshi, S; Sundaram, C Sairam

2016-01-20

The performance of synthesised O-fumaryl-chitosan (OFC) as corrosion inhibitor for mild steel in 1M HCl has been evaluated through various studies. The initial screening by weight loss method revealed the good inhibition efficiency by the inhibitor. Thermodynamic and kinetic parameters have been calculated and discussed. The mode of adsorption is physical in nature and it follows Langmuir adsorption isotherm. Electrochemical measurements supported the inhibition of mild steel by the fumaryl derivative of chitosan. Polarisation studies provided the information that the inhibition is of mixed type. The formation of inhibitor film is assured by surface morphological studies with Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The mechanism of inhibition is derived from the Fourier-transform infrared (FTIR) spectroscopy and zero charge potential measurement. The adsorbed film is characterised using FTIR and X-ray diffraction studies (XRD). Copyright © 2015 Elsevier Ltd. All rights reserved.

The formation of fragments at corotation in isothermal protoplanetary disks

NASA Astrophysics Data System (ADS)

Durisen, Richard H.; Hartquist, Thomas W.; Pickett, Megan K.

2008-09-01

Numerical hydrodynamics simulations have established that disks which are evolved under the condition of local isothermality will fragment into small dense clumps due to gravitational instabilities when the Toomre stability parameter Q is sufficiently low. Because fragmentation through disk instability has been suggested as a gas giant planet formation mechanism, it is important to understand the physics underlying this process as thoroughly as possible. In this paper, we offer analytic arguments for why, at low Q, fragments are most likely to form first at the corotation radii of growing spiral modes, and we support these arguments with results from 3D hydrodynamics simulations.

A theory of stationarity and asymptotic approach in dissipative systems

NASA Astrophysics Data System (ADS)

Rubel, Michael Thomas

2007-05-01

The approximate dynamics of many physical phenomena, including turbulence, can be represented by dissipative systems of ordinary differential equations. One often turns to numerical integration to solve them. There is an incompatibility, however, between the answers it can produce (i.e., specific solution trajectories) and the questions one might wish to ask (e.g., what behavior would be typical in the laboratory?) To determine its outcome, numerical integration requires more detailed initial conditions than a laboratory could normally provide. In place of initial conditions, experiments stipulate how tests should be carried out: only under statistically stationary conditions, for example, or only during asymptotic approach to a final state. Stipulations such as these, rather than initial conditions, are what determine outcomes in the laboratory.This theoretical study examines whether the points of view can be reconciled: What is the relationship between one's statistical stipulations for how an experiment should be carried out--stationarity or asymptotic approach--and the expected results? How might those results be determined without invoking initial conditions explicitly?To answer these questions, stationarity and asymptotic approach conditions are analyzed in detail. Each condition is treated as a statistical constraint on the system--a restriction on the probability density of states that might be occupied when measurements take place. For stationarity, this reasoning leads to a singular, invariant probability density which is already familiar from dynamical systems theory. For asymptotic approach, it leads to a new, more regular probability density field. A conjecture regarding what appears to be a limit relationship between the two densities is presented.By making use of the new probability densities, one can derive output statistics directly, avoiding the need to create or manipulate initial data, and thereby avoiding the conceptual incompatibility mentioned above. This approach also provides a clean way to derive reduced-order models, complete with local and global error estimates, as well as a way to compare existing reduced-order models objectively.The new approach is explored in the context of five separate test problems: a trivial one-dimensional linear system, a damped unforced linear oscillator in two dimensions, the isothermal Rayleigh-Plesset equation, Lorenz's equations, and the Stokes limit of Burgers' equation in one space dimension. In each case, various output statistics are deduced without recourse to initial conditions. Further, reduced-order models are constructed for asymptotic approach of the damped unforced linear oscillator, the isothermal Rayleigh-Plesset system, and Lorenz's equations, and for stationarity of Lorenz's equations.

Analysis of the variation of the 0°C isothermal altitude during rainfall events

NASA Astrophysics Data System (ADS)

Zeimetz, Fränz; Garcìa, Javier; Schaefli, Bettina; Schleiss, Anton J.

2016-04-01

In numerous countries of the world (USA, Canada, Sweden, Switzerland,…), the dam safety verifications for extreme floods are realized by referring to the so called Probable Maximum Flood (PMF). According to the World Meteorological Organization (WMO), this PMF is determined based on the PMP (Probable Maximum Precipitation). The PMF estimation is performed with a hydrological simulation model by routing the PMP. The PMP-PMF simulation is normally event based; therefore, if no further information is known, the simulation needs assumptions concerning the initial soil conditions such as saturation or snow cover. In addition, temperature series are also of interest for the PMP-PMF simulations. Temperature values can not only be deduced from temperature measurement but also using the temperature gradient method, the 0°C isothermal altitude can lead to temperature estimations on the ground. For practitioners, the usage of the isothermal altitude for referring to temperature is convenient and simpler because one value can give information over a large region under the assumption of a certain temperature gradient. The analysis of the evolution of the 0°C isothermal altitude during rainfall events is aimed here and based on meteorological soundings from the two sounding stations Payerne (CH) and Milan (I). Furthermore, hourly rainfall and temperature data are available from 110 pluviometers spread over the Swiss territory. The analysis of the evolution of the 0°C isothermal altitude is undertaken for different precipitation durations based on the meteorological measurements mentioned above. The results show that on average, the isothermal altitude tends to decrease during the rainfall events and that a correlation between the duration of the altitude loss and the duration of the rainfall exists. A significant difference in altitude loss is appearing when the soundings from Payerne and Milan are compared.

The density structure and star formation rate of non-isothermal polytropic turbulence

NASA Astrophysics Data System (ADS)

Federrath, Christoph; Banerjee, Supratik

2015-04-01

The interstellar medium of galaxies is governed by supersonic turbulence, which likely controls the star formation rate (SFR) and the initial mass function (IMF). Interstellar turbulence is non-universal, with a wide range of Mach numbers, magnetic fields strengths and driving mechanisms. Although some of these parameters were explored, most previous works assumed that the gas is isothermal. However, we know that cold molecular clouds form out of the warm atomic medium, with the gas passing through chemical and thermodynamic phases that are not isothermal. Here we determine the role of temperature variations by modelling non-isothermal turbulence with a polytropic equation of state (EOS), where pressure and temperature are functions of gas density, P˜ ρ ^Γ, T ˜ ρΓ - 1. We use grid resolutions of 20483 cells and compare polytropic exponents Γ = 0.7 (soft EOS), Γ = 1 (isothermal EOS) and Γ = 5/3 (stiff EOS). We find a complex network of non-isothermal filaments with more small-scale fragmentation occurring for Γ < 1, while Γ > 1 smoothes out density contrasts. The density probability distribution function (PDF) is significantly affected by temperature variations, with a power-law tail developing at low densities for Γ > 1. In contrast, the PDF becomes closer to a lognormal distribution for Γ ≲ 1. We derive and test a new density variance-Mach number relation that takes Γ into account. This new relation is relevant for theoretical models of the SFR and IMF, because it determines the dense gas mass fraction of a cloud, from which stars form. We derive the SFR as a function of Γ and find that it decreases by a factor of ˜5 from Γ = 0.7 to 5/3.

Biosorption Behavior of Ciprofloxacin onto Enteromorpha prolifera: Isotherm and Kinetic Studies.

PubMed

Wu, Shaoling; Li, Yanhui; Zhao, Xindong; Du, Qiuju; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

2015-01-01

The studies aimed at the feasibility of using Enteromorpha prolifera for the removal of ciprofloxacin from aqueous solutions. Batch experiments were carried out for the biosorption of ciprofloxacin onto Enteromorpha prolifera. The factors affecting the biosorption process such as the initial concentration, dosage, pH and the contact time were studied. Enteromorpha prolifera exhibited a maximum biosorption capacity of 21.7 mg/g. The pseudo-second-order kinetic model described the ciprofloxacin biosorption process with a good fitting. The optimum pH of ciprofloxacin adsorbed by Enteromorpha prolifera was 10. Biosorption equilibrium studies demonstrated that the biosorption followed Freundlich isotherm model, which implied a heterogeneous biosorption phenomenon.

Comparison of infinite and wedge fringe settings in Mach Zehnder interferometer for temperature field measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haridas, Divya; P, Vibin Antony; Sajith, V.

2014-10-15

Interferometric method, which utilizes the interference of coherent light beams, is used to determine the temperature distribution in the vicinity of a vertical heater plate. The optical components are arranged so as to obtain wedge fringe and infinite fringe patterns and isotherms obtained in each case were compared. In wedge fringe setting, image processing techniques has been used for obtaining isotherms by digital subtraction of initial parallel fringe pattern from deformed fringe pattern. The experimental results obtained are compared with theoretical correlations. The merits and demerits of the fringe analysis techniques are discussed on the basis of the experimental results.

Hot Cores in Magellanic Clouds

NASA Astrophysics Data System (ADS)

Acharyya, Kinsuk; Herbst, Eric

2018-05-01

We have studied the chemistry of molecules through complex organic molecules (COMs) in complexity in conditions resembling galactic hot molecular cores in the Large and Small Magellanic Clouds using a gas-grain network. To the best of our knowledge, there have been no previous such quantitative studies of hot core chemistry in these low metallicity, dust-poor galaxies. We utilized a physical model that consists of an initial isothermal collapse, followed by a warm-up phase to hot core conditions. Four different temperatures—10, 15, 20, and 25 K—were used for the isothermal collapse phase, considering the fact that these galaxies might have higher dust temperatures in cold regions than observed in the Milky Way. We found that for some abundant species, such as CO and water, hot core abundances are consistent with the reduced elemental abundances of the LMC and SMC. For other less abundant species, such as CH4 and HCN, the calculated abundances are larger when compared with elemental abundances, whereas for species like ammonia they are lower. Our calculations show that some COMs can also be formed in reasonable quantity for hot cores in the Magellanic Clouds when the grain temperature is lower than 25 K. Our results can be compared with recent observations of the hot cores in the high-mass young stellar object (YSO) ST11 and regions A1 and B3 of the star-forming source N113 in the LMC. Model results are in reasonable agreement with the observed abundances and upper limits.

Adsorption of Rh(III) complexes from chloride solutions obtained by leaching chlorinated spent automotive catalysts on ion-exchange resin Diaion WA21J.

PubMed

Shen, Shaobo; Pan, Tonglin; Liu, Xinqiang; Yuan, Lei; Wang, Jinchao; Zhang, Yongjian; Guo, Zhanchen

2010-07-15

It was found that Rh, Pd and Pt contained in the spent ceramic automotive catalysts could be effectively extracted by dry chlorination with chlorine. In order to concentrate Rh(III) ions contained in the chloride solutions obtained, thermodynamic and kinetics studies for adsorption of Rh(III) complexes from the chloride solutions on an anionic exchange resin Diaion WA21J were carried out. Rh, Pd, Pt, Al, Fe, Si, Zn and Pb from the chloride solution could be adsorbed on the resin. The distribution coefficients (K(d)) of Rh(III) decreased with the increase in initial Rh(III) concentration or in adsorption temperature. The isothermal adsorption of Rh(III) was found to fit Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich models under the adsorption conditions. The maximum monolayer adsorption capacities Q(max) based on Langmuir adsorption isotherms were 6.39, 6.61 and 5.81 mg/g for temperatures 18, 28 and 40 degrees C, respectively. The apparent adsorption energy of Rh was about -7.6 kJ/mol and thus Rh(III) adsorption was a physical type. The experimental data obtained could be better simulated by pseudo-first-order kinetic model and the activation energy obtained was 6.54 J/mol. The adsorption rate of Rh(III) was controlled by intraparticle diffusion in most of time of adsorption process. 2010 Elsevier B.V. All rights reserved.

Sorption of metolachlor and atrazine in fly ash amended soils: comparison of optimized isotherm models.

PubMed

Ghosh, Rakesh K; Singh, Neera

2012-01-01

Adsorption of metolachlor and atrazine was studied in the fly ash (Inderprastha and Badarpur)- amended Inceptisol and Alfisol soils using batch method. Results indicated that sorption of both the herbicides in soil+fly ash mixtures was highly nonlinear and sorption decreased with a higher herbicide concentration in the solution. Also, nonlinearity increased with an increase in the level of fly ash amendment from 0-5%. Three two-parameter monolayer isotherms viz. Langmuir, Temkin, Jovanovic and one imperical Freundlich models were used to fit the experimental data. Data analysis and comparison revealed that the Temkin and the Freundlich isotherms were best-suited to explain the sorption results and the observed and the calculated adsorption coefficient values showed less variability. The study suggested that sorption mechanism of metolachlor and atrazine involved the physical association at the sorbate surface and the nonlinearity in the sorption at higher pesticide or fly ash concentration was due to a decrease in the heat of adsorption and higher binding energy.

Sorption of poly(hexamethylenebiguanide) on cellulose: mechanism of binding and molecular recognition.

PubMed

Blackburn, Richard S; Harvey, Anna; Kettle, Lorna L; Payne, John D; Russell, Stephen J

2006-06-20

Antimicrobial agents such as poly(hexamethylene biguanide) (PHMB) find application in medical, apparel, and household textile sectors; although it is understood that certain concentrations need to be applied to achieve suitable performance, there has been very little work published concerning the interactions of the polymer and its adsorption mechanism on cellulose. In this paper, such physical chemistry parameters are examined and related to computational chemistry studies. Adsorption isotherms were constructed: at low concentrations, these were typical Langmuir isotherms; at higher concentrations, they were more indicative of Freundlich isotherms, attributed to a combination of electrostatic and hydrogen-bonding forces, which endorsed computational chemistry proposals. At lower concentrations, electrostatic interactions between PHMB and carboxylic acid groups in the cellulose dominate with a contribution to binding through hydrogen bonding; as the concentration of PHMB increases, hydrogen bonding with cellulose becomes increasingly dominant. At high PHMB concentrations, observations of increasing PHMB adsorption are attributed to monolayer aggregation and multilayer stacking of PHMB through electrostatic interactions with counterions and hydrogen bonding of biguanide groups.

Preparation of char from lotus seed biomass and the exploration of its dye removal capacity through batch and column adsorption studies.

PubMed

Nethaji, S; Sivasamy, A; Kumar, R Vimal; Mandal, A B

2013-06-01

Char was obtained from lotus seed biomass by a simple single-step acid treatment process. It was used as an adsorbent for the removal of malachite green dye (MG) from simulated dye bath effluent. The adsorbent was characterized for its surface morphology, surface functionalities, and zero point charge. Batch studies were carried out by varying the parameters such as initial aqueous pH, adsorbent dosage, adsorbent particle size, and initial adsorbate concentration. Langmuir and Freundlich isotherms were used to test the isotherm data and the Freundlich isotherm best fitted the data. Thermodynamic studies were carried out and the thermodynamic parameters such as ∆G, ∆H, and ∆S were evaluated. Adsorption kinetics was carried out and the data were tested with pseudofirst-order model, pseudosecond-order model, and intraparticle diffusion model. Adsorption of MG was not solely by intraparticle diffusion but film diffusion also played a major role. Continuous column experiments were also conducted using microcolumn and the spent adsorbent was regenerated using ethanol and was repeatedly used for three cycles in the column to determine the reusability of the regenerated adsorbent. The column data were modeled with the modeling equations such as Adam-Bohart model, Bed Depth Service Time (BDST) model, and Yoon-Nelson model for all the three cycles.

A Simple Adsorption Experiment

ERIC Educational Resources Information Center

Guirado, Gonzalo; Ayllon, Jose A.

2011-01-01

The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

PROCESS INTENSIFICATION: MICROWAVE INITIATED REACTIONS USING A CONTINUOUS FLOW REACTOR

EPA Science Inventory

The concept of process intensification has been used to develop a continuous narrow channel reactor at Clarkson capable of carrying out reactions under isothermal conditions whilst being exposed to microwave (MW) irradiation thereby providing information on the true effect of mi...

Radioactive Cobalt(II) Removal from Aqueous Solutions Using a Reusable Nanocomposite: Kinetic, Isotherms, and Mechanistic Study

PubMed Central

Wang, Ximing; Chen, Zhangjing

2017-01-01

A lignocellulose/montmorillonite (LMT) nanocomposite was prepared as a reusable adsorbent for cobalt(II) ions, and characterized by nitrogen (N2) adsorption/desorption isotherm, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). LMT exhibited efficient adsorption of cobalt ions (Co(II)), and the adsorbed Co(II) was readily desorbed by nitric acid (HNO3). All parameters affecting the adsorption and/or desorption of Co(II), including initial Co(II) concentration, pH value, temperature, HNO3 concentration, and time, were optimized. The kinetic data analysis showed that the adsorption followed the pseudo-second-order kinetic model and fit well into the Langmuir isotherm equation. Notably, the nanocomposite can be used four times without significantly losing adsorbent capability. The Energy-Dispersive X-ray (EDX) and FTIR spectra analysis also revealed that the adsorption mechanism may be mainly a chemical adsorption dominated process. PMID:29186794

Characterization of Damage Progression in SCS-6/timetal 21S (0)4 Under Thermomechanical Fatigue Loadings

NASA Technical Reports Server (NTRS)

Castelli, Michael G.

1994-01-01

A detailed experimental investigation was performed at a single maximum cyclic stress (sigma max) level to physically characterize the progression of thermomechanical fatigue (lW) damage in continuously reinforced (0 deg) SCS-6/Timetal 21S, a titanium matrix composite. In-phase (IP) and out of-phase (OP) loadings were investigated at sigma max = 1000 MPa with a temperature cycle from 150 to 6500 C. Damage progression, in terms of macroscopic property degradation, was experimentally quantified through an advanced TMF test methodology which incorporates explicit measurements of the isothermal static moduli at the TMF temperature extremes and the coefficient of thermal expansion (CTE) as functions of the TMF cycles. Detailed characterization of the physical damage progression at the microstructural level was performed by interrupting multiple TMF tests at various stages of mechanical property degradation and analyzing the microstructure through extensive destructive metallography. Further, the extent of damage was also quantified through residual static strength measurements. Results indicated that damage initiation occurred very early in cyclic life (N less than 0.1Nf) for both the IP and OP TMF loadings. IP TMF damage was found to be dominated by fiber breakage with a physical damage progression in the microstructure which was difficult to quantify. OP TMF loadings produced matrix cracking exclusively associated with surface initiations. Here, damage progression was easily distinguished in terms of both the number of cracks and their relative inward progressions toward the outer fiber rows with increased cycling. The point at which the leading cracks reached the outer fiber rows (when localized fiber/matrix de-bonding and matrix crack bridging occurred) appeared to be reflected in the macroscopic property degradation curves.

Batch sorption dynamics and equilibrium for the removal of lead ions from aqueous phase using activated carbon developed from coffee residue activated with zinc chloride.

PubMed

Boudrahem, F; Aissani-Benissad, F; Aït-Amar, H

2009-07-01

Lignocellulosic materials are good precursors for the production of activated carbon. In this work, coffee residue has been used as raw material in the preparation of powder activated carbon by the method of chemical activation with zinc chloride for the sorption of Pb(II) from dilute aqueous solutions. The influence of impregnation ratio (ZnCl2/coffee residue) on the physical and chemical properties of the prepared carbons was studied in order to optimize this parameter. The optimum experimental condition for preparing predominantly microporous activated carbons with high pore surface area (890 m2/g) and micropore volume (0.772 cm3/g) is an impregnation ratio of 100%. The developed activated carbon shows substantial capability to sorb lead(II) ions from aqueous solutions and for relative impregnation ratios of 75 and 100%, the maximum uptake is practically the same. Thus, 75% represents the optimal impregnation ratio. Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), solution pH, ionic strength and temperature. The maximum uptake of lead(II) at 25 degrees C was about 63 mg/g of adsorbent at pH 5.8, initial Pb(II) concentration of 10 mg/L, agitation speed of 200 rpm and ionic strength of 0.005 M. The kinetic data were fitted to the models of pseudo-first order and pseudo-second order, and follow closely the pseudo-second order model. Equilibrium sorption isotherms of Pb(II) were analyzed by the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model gives a better fit than the others. Results from this study suggest that activated carbon produced from coffee residue is an effective adsorbent for the removal of lead from aqueous solutions and that ZnCl2 is a suitable activating agent for the preparation of high-porosity carbons.

Adsorptive removal of Auramine-O: kinetic and equilibrium study.

PubMed

Mall, Indra Deo; Srivastava, Vimal Chandra; Agarwal, Nitin Kumar

2007-05-08

Present study deals with the adsorption of Auramine-O (AO) dye by bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL). BFA is a solid waste obtained from the particulate collection equipment attached to the flue gas line of the bagasse fired boilers of cane sugar mills. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH(0)), contact time, adsorbent dose and initial concentration (C(0)) for the removal of AO. Optimum conditions for AO removal were found to be pH(0) approximately 7.0 and equilibrium time approximately 30 min for BFA and approximately 120 min for activated carbons. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2g/l, respectively. Adsorption of AO followed pseudo-second order kinetics with the initial sorption rate for adsorption on BFA being the highest followed by those on ACL and ACC. The sorption process was found to be controlled by both film and pore diffusion with film diffusion at the earlier stages followed by pore diffusion at the later stages. Equilibrium isotherms for the adsorption of AO on BFA, ACC and ACL were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin isotherm equations using linear correlation coefficient. Langmuir isotherm gave the best correlation of adsorption for all the adsorbents studied. Thermodynamic study showed that adsorption of AO on ACC (with a more negative Gibbs free energy value) is more favoured. BFA which was used without any pretreatment showed high surface area, pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of AO.

EzyAmp signal amplification cascade enables isothermal detection of nucleic acid and protein targets.

PubMed

Linardy, Evelyn M; Erskine, Simon M; Lima, Nicole E; Lonergan, Tina; Mokany, Elisa; Todd, Alison V

2016-01-15

Advancements in molecular biology have improved the ability to characterize disease-related nucleic acids and proteins. Recently, there has been an increasing desire for tests that can be performed outside of centralised laboratories. This study describes a novel isothermal signal amplification cascade called EzyAmp (enzymatic signal amplification) that is being developed for detection of targets at the point of care. EzyAmp exploits the ability of some restriction endonucleases to cleave substrates containing nicks within their recognition sites. EzyAmp uses two oligonucleotide duplexes (partial complexes 1 and 2) which are initially cleavage-resistant as they lack a complete recognition site. The recognition site of partial complex 1 can be completed by hybridization of a triggering oligonucleotide (Driver Fragment 1) that is generated by a target-specific initiation event. Binding of Driver Fragment 1 generates a completed complex 1, which upon cleavage, releases Driver Fragment 2. In turn, binding of Driver Fragment 2 to partial complex 2 creates completed complex 2 which when cleaved releases additional Driver Fragment 1. Each cleavage event separates fluorophore quencher pairs resulting in an increase in fluorescence. At this stage a cascade of signal production becomes independent of further target-specific initiation events. This study demonstrated that the EzyAmp cascade can facilitate detection and quantification of nucleic acid targets with sensitivity down to aM concentration. Further, the same cascade detected VEGF protein with a sensitivity of 20nM showing that this universal method for amplifying signal may be linked to the detection of different types of analytes in an isothermal format. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

A differential CDM model for fatigue of unidirectional metal matrix composites

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Kruch, S.

1992-01-01

A multiaxial, isothermal, continuum damage mechanics (CDM) model for fatigue of a unidirectional metal matrix composite volume element is presented. The model is phenomenological, stress based, and assumes a single scalar internal damage variable, the evolution of which is anisotropic. The development of the fatigue damage model, (i.e., evolutionary law) is based on the definition of an initially transversely isotropic fatigue limit surface, a static fracture surface, and a normalized stress amplitude function. The anisotropy of these surfaces and function, and therefore the model, is defined through physically meaningful invariants reflecting the local stress and material orientation. This transversely isotropic model is shown, when taken to it's isotropic limit, to directly simplify to a previously developed and validated isotropic fatigue continuum damage model. Results of a nondimensional parametric study illustrate (1) the flexibility of the present formulation in attempting to characterize a class of composite materials, and (2) the capability of the formulation in predicting anticipated qualitative trends in the fatigue behavior of unidirectional metal matrix composites. Also, specific material parameters representing an initial characterization of the composite system SiC/Ti 15-3 and the matrix material (Ti 15-3) are reported.

Isothermal thermogravimetric data acquisition analysis system

NASA Technical Reports Server (NTRS)

Cooper, Kenneth, Jr.

1991-01-01

The description of an Isothermal Thermogravimetric Analysis (TGA) Data Acquisition System is presented. The system consists of software and hardware to perform a wide variety of TGA experiments. The software is written in ANSI C using Borland's Turbo C++. The hardware consists of a 486/25 MHz machine with a Capital Equipment Corp. IEEE488 interface card. The interface is to a Hewlett Packard 3497A data acquisition system using two analog input cards and a digital actuator card. The system provides for 16 TGA rigs with weight and temperature measurements from each rig. Data collection is conducted in three phases. Acquisition is done at a rapid rate during initial startup, at a slower rate during extended data collection periods, and finally at a fast rate during shutdown. Parameters controlling the rate and duration of each phase are user programmable. Furnace control (raising and lowering) is also programmable. Provision is made for automatic restart in the event of power failure or other abnormal terminations. Initial trial runs were conducted to show system stability.

Statistical analysis and isotherm study of uranium biosorption by Padina sp. algae biomass.

PubMed

Khani, Mohammad Hassan

2011-06-01

The application of response surface methodology is presented for optimizing the removal of U ions from aqueous solutions using Padina sp., a brown marine algal biomass. Box-Wilson central composite design was employed to assess individual and interactive effects of the four main parameters (pH and initial uranium concentration in solutions, contact time and temperature) on uranium uptake. Response surface analysis showed that the data were adequately fitted to second-order polynomial model. Analysis of variance showed a high coefficient of determination value (R (2)=0.9746) and satisfactory second-order regression model was derived. The optimum pH and initial uranium concentration in solutions, contact time and temperature were found to be 4.07, 778.48 mg/l, 74.31 min, and 37.47°C, respectively. Maximized uranium uptake was predicted and experimentally validated. The equilibrium data for biosorption of U onto the Padina sp. were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 376.73 mg/g.

Dye adsorption into transition metal-doped zinc oxide nanoparticles supported on natural zeolites to solve wastewater issue

NASA Astrophysics Data System (ADS)

Indra Pratiwi, Margaretha; Afifah, Nur; Saleh, Rosari

2017-03-01

In this work, Fe-doped zinc oxide/natural zeolite (Fe:ZnO/NZ) nanocomposites were prepared using the co-precipitation method with various NZ amounts. The nanocomposites were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis and thermogravimetric analysis (TGA). The nanocomposites were used to remove methylene blue (MB) dye from an aqueous solution. The effect of various NZ amounts and initial MB concentration were tested. The Pseudo-first-order and pseudo-second-order kinetic models were used to explain the adsorption mechanism. The Langmuir and the Freundlich isotherm models were used to fit the adsorption isotherms of the nanocomposites.

Adsorption behavior of the (+/-)-Tröger's base enantiomers in the phase system of a silica-based packing coated with amylose tri(3,5-dimethyl carbamate) and 2-propanol and molecular modeling interpretation.

PubMed

Mihlbachler, Kathleen; De Jesús, Marco A; Kaczmarski, Krzysztof; Sepaniak, Michael J; Seidel-Morgenstern, Andreas; Guiochon, Georges

2006-04-28

The binary adsorption isotherms of the enantiomers of Tröger's base in the phase system made of Chiral Technologies ChiralPak AD [a silica-based packing coated with amylose tri(3,5-dimethyl carbamate)] as the chiral stationary phase (CSP) and 2-propanol as the mobile phase were measured by the perturbation method. The more retained enantiomer exhibits a S-shaped adsorption isotherm with a clear inflection point, the concentration of the less retained enantiomer having practically no competitive influence on this isotherm: In the entire range of concentrations studied, dq2/dC1 approximately 0. By contrast, the less retained enantiomer has a Langmuir adsorption isotherm when pure. At constant mobile phase concentrations, however, its equilibrium concentration in the adsorbed phase increases with increasing concentration of the more retained enantiomer and dq1/dC2 > 0. This cooperative adsorption behavior, opposed to the classical competitive behavior, is exceedingly rare but was clearly demonstrated in this case. Two adsorption isotherm equations that account for these physical observations were derived. They are based on the formation of an adsorbed multi-layer, as suggested by the isotherm data. The excellent agreement between the experimental overloaded elution profiles of binary mixtures and the profiles calculated with the equilibrium-dispersive model validates this binary isotherm model. The adsorption energies calculated by molecular mechanics (MM) and by molecular dynamics (MD) indicate that the chiral recognition arising from the different interactions between the functional groups of the CSP and the molecules of the Tröger's base enantiomers are mainly driven by their Van der Waals interactions. The MD data suggest that the interactions of the (-)-Tröger's base with the CSP are more favored by 8+/-(5) kJ/mol than those of (+)-Tröger's base. This difference seems to be a contributing factor to the increased retention of the - enantiomer on this chromatographic system. The modeling of the data also indicates that both enantiomers can form high stoichiometry complexes while binding onto the stationary phase, in agreement with the results of the equilibrium isotherm studies.

Microstructure Evolution and the Resulted Influence on Localized Corrosion in Al-Zn-Mg-Cu Alloy during Non-Isothermal Ageing

PubMed Central

Chen, Jun-Zhou; Li, Guo-Ai; Cai, Xin; Jiang, Jian-Tang; Shao, Wen-Zhu; Yang, Li; Zhen, Liang

2018-01-01

A non-isothermal ageing process was proposed for an Al-Zn-Mg-Cu alloy aiming to accommodate the slow heating/cooling procedure during the ageing of large components. The evolution of microstructure and microchemistry was analyzed by using transmission electron microscopy, high-angle annular dark field imaging, and energy dispersive spectrometry. The age-hardening of the alloy was examined to evaluate the strengthening behavior during the non-isothermal process. The corrosion behavior was investigated via observing the specimens immersed in EXCO solution (solution for Exfoliation Corrosion Susceptibility test in 2xxx and 7xxx series aluminum alloys, referring ASTM G34-01). Secondary precipitation was observed during the cooling stage, leading to increased precipitate number density. The distribution of grain boundary precipitates transits from discontinuous to continuous at the cooling stage, due to the secondary precipitation’s linking-up effect. The solutes’ enrichment on grain boundary precipitates and the depletion in precipitate-free zones develops during the heating procedure, but remains invariable during the cooling procedure. The corrosion in NIA (Non-isothermal Ageing) treated specimens initiates from pitting and then transits to intergranular corrosion and exfoliation corrosion. The transition from pitting to intergranular corrosion is very slow for specimens heated to 190 °C, but accelerates slightly as the cooling procedure proceeds. The transition to exfoliation corrosion is observed to be quite slow in all specimens in non-isothermal aged to over-aged condition, suggesting a corrosion resistance comparable to that of RRA condition. PMID:29751493

Microstructure Evolution and the Resulted Influence on Localized Corrosion in Al-Zn-Mg-Cu Alloy during Non-Isothermal Ageing.

PubMed

Chen, Jun-Zhou; Li, Guo-Ai; Cai, Xin; Jiang, Jian-Tang; Shao, Wen-Zhu; Yang, Li; Zhen, Liang

2018-05-03

A non-isothermal ageing process was proposed for an Al-Zn-Mg-Cu alloy aiming to accommodate the slow heating/cooling procedure during the ageing of large components. The evolution of microstructure and microchemistry was analyzed by using transmission electron microscopy, high-angle annular dark field imaging, and energy dispersive spectrometry. The age-hardening of the alloy was examined to evaluate the strengthening behavior during the non-isothermal process. The corrosion behavior was investigated via observing the specimens immersed in EXCO solution (solution for Exfoliation Corrosion Susceptibility test in 2xxx and 7xxx series aluminum alloys, referring ASTM G34-01). Secondary precipitation was observed during the cooling stage, leading to increased precipitate number density. The distribution of grain boundary precipitates transits from discontinuous to continuous at the cooling stage, due to the secondary precipitation’s linking-up effect. The solutes’ enrichment on grain boundary precipitates and the depletion in precipitate-free zones develops during the heating procedure, but remains invariable during the cooling procedure. The corrosion in NIA (Non-isothermal Ageing) treated specimens initiates from pitting and then transits to intergranular corrosion and exfoliation corrosion. The transition from pitting to intergranular corrosion is very slow for specimens heated to 190 °C, but accelerates slightly as the cooling procedure proceeds. The transition to exfoliation corrosion is observed to be quite slow in all specimens in non-isothermal aged to over-aged condition, suggesting a corrosion resistance comparable to that of RRA condition.

Using the Surface Temperature-Albedo Space to Separate Regional Soil and Vegetation Temperatures from ASTER Data

USDA-ARS?s Scientific Manuscript database

Soil and vegetation component temperatures in non-isothermal pixels encapsulate more physical meaning and are more applicable than composite temperatures. The component temperatures however are difficult to be obtained from thermal infrared (TIR) remote sensing data provided by single view angle obs...

Variations on the Zilch Cycle

ERIC Educational Resources Information Center

Binder, P.-M.; Tanoue, C. K. S.

2013-01-01

Thermo dynamic cycles in introductory physics courses are usually made up from a small number of permutations of isothermal, adiabatic, and constant-pressure and volume quasistatic strokes, with the working fluid usually being an ideal gas. Among them we find the Carnot, Stirling, Otto, Diesel, and Joule-Brayton cycles; in more advanced courses,…

Time dependent behavior of a graphite/thermoplastic composite and the effects of stress and physical aging

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Feldman, Mark

1993-01-01

Two complimentary studies were performed to determine the effects of stress and physical aging on the matrix dominated time dependent properties of IM7/8320 composite. The first of these studies, experimental in nature, used isothermal tensile creep/aging test techniques developed for polymers and adapted them for testing of the composite material. From these tests, the time dependent transverse (S22) and shear (S66) compliance's for an orthotropic plate were found from short term creep compliance measurements at constant, sub-T(sub g) temperatures. These compliance terms were shown to be affected by physical aging. Aging time shift factors and shift rates were found to be a function of temperature and applied stress. The second part of the study relied upon isothermal uniaxial tension tests of IM7/8320 to determine the effects of physical aging on the nonlinear material behavior at elevated temperature. An elastic/viscoplastic constitutive model was used to quantify the effects of aging on the rate-independent plastic and rate-dependent viscoplastic response. Sensitivity of the material constants required by the model to aging time were determined for aging times up to 65 hours. Verification of the analytical model indicated that the effects of prior aging on the nonlinear stress/strain/time data of matrix dominated laminates can be predicted.

Functional models for colloid retention in porous media at the triple line.

PubMed

Dathe, Annette; Zevi, Yuniati; Richards, Brian K; Gao, Bin; Parlange, J-Yves; Steenhuis, Tammo S

2014-01-01

Spectral confocal microscope visualizations of microsphere movement in unsaturated porous media showed that attachment at the Air Water Solid (AWS) interface was an important retention mechanism. These visualizations can aid in resolving the functional form of retention rates of colloids at the AWS interface. In this study, soil adsorption isotherm equations were adapted by replacing the chemical concentration in the water as independent variable by the cumulative colloids passing by. In order of increasing number of fitted parameters, the functions tested were the Langmuir adsorption isotherm, the Logistic distribution, and the Weibull distribution. The functions were fitted against colloid concentrations obtained from time series of images acquired with a spectral confocal microscope for three experiments performed where either plain or carboxylated polystyrene latex microspheres were pulsed in a small flow chamber filled with cleaned quartz sand. Both moving and retained colloids were quantified over time. In fitting the models to the data, the agreement improved with increasing number of model parameters. The Weibull distribution gave overall the best fit. The logistic distribution did not fit the initial retention of microspheres well but otherwise the fit was good. The Langmuir isotherm only fitted the longest time series well. The results can be explained that initially when colloids are first introduced the rate of retention is low. Once colloids are at the AWS interface they act as anchor point for other colloids to attach and thereby increasing the retention rate as clusters form. Once the available attachment sites diminish, the retention rate decreases.

Synthesis and Characterization of Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites Used for Pb(II) Removal

PubMed Central

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wu, Qing; Wei, Xionghui; Li, Lingyun; Shi, Xuedan; Ruan, Wenqian

2016-01-01

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2-sorption and X-ray photoelectron spectroscopy (XPS). Operating parameters for the removal process of Pb(II) ions, such as temperature (20–40 °C), pH (3–5), initial concentration (400–600 mg/L) and contact time (20–60 min), were optimized using a quadratic model. The coefficient of determination (R2 > 0.99) obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II) ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II) removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II) ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II)-containing wastewater. PMID:28773813

Synthesis and Characterization of Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites Used for Pb(II) Removal.

PubMed

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wu, Qing; Wei, Xionghui; Li, Lingyun; Shi, Xuedan; Ruan, Wenqian

2016-08-12

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N₂-sorption and X-ray photoelectron spectroscopy (XPS). Operating parameters for the removal process of Pb(II) ions, such as temperature (20-40 °C), pH (3-5), initial concentration (400-600 mg/L) and contact time (20-60 min), were optimized using a quadratic model. The coefficient of determination ( R ² > 0.99) obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II) ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II) removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II) ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II)-containing wastewater.

Removal of persistent organic pollutants from micro-polluted drinking water by triolein embedded absorbent.

PubMed

Liu, Huijuan; Ru, Jia; Qu, Jiuhui; Dai, Ruihua; Wang, Zijian; Hu, Chun

2009-06-01

A new biomimetic absorbent, cellulose acetate (CA) embedded with triolein (CA-triolein), was prepared and applied for the removal of persistent organic pollutants (POPs) from micro-polluted aqueous solution. The comparison of CA-triolein, CA and granular activated carbon (GAC) for dieldrin removal was investigated. Results showed that CA-triolein absorbent gave a lowest residual concentration after 24 h although GAC had high removal rate in the first 4 h adsorption. Then the removal efficiency of mixed POPs (e.g. aldrin, dieldrin, endrin and heptachlor epoxide), absorption isotherm, absorbent regeneration and initial column experiments of CA-triolein were studied in detail. The linear absorption isotherm and the independent absorption in binary isotherm indicated that the selected POPs are mainly absorbed onto CA-triolein absorbent by a partition mechanism. The absorption constant, K, was closely related to the hydrophobic property of the compound. Thermodynamic calculations showed that the absorption was spontaneous, with a high affinity and the absorption was an endothermic reaction. Rinsing with hexane the CA-triolein absorbent can be regenerated after absorption of POPs. No significant decrease in the dieldrin removal efficiency was observed even when the absorption-regeneration process was repeated for five times. The results of initial column experiments showed that the CA-triolein absorbent did not reach the breakthrough point at a breakthrough empty-bed volume (BV) of 3200 when the influent concentration was 1-1.5 microg/L and the empty-bed contact time (EBCT) was 20 min.

Biosorption of Congo Red from aqueous solution onto burned root of Eichhornia crassipes biomass

NASA Astrophysics Data System (ADS)

Roy, Tapas Kumar; Mondal, Naba Kumar

2017-07-01

Biosorption is becoming a promising alternative to replace or supplement the present dye removal processes from dye containing waste water. In this work, adsorption of Congo Red (CR) from aqueous solution on burned root of Eichhornia crassipes ( BREC) biomass was investigated. A series of batch experiments were performed utilizing BREC biomass to remove CR dye from aqueous systems. Under optimized batch conditions, the BREC could remove up to 94.35 % of CR from waste water. The effects of operating parameters such as initial concentration, pH, adsorbent dose and contact time on the adsorption of CR were analyzed using response surface methodology. The proposed quadratic model for central composite design fitted very well to the experimental data. Response surface plots were used to determine the interaction effects of main factors and optimum conditions of the process. The optimum adsorption conditions were found to be initial CR concentration = 5 mg/L-1, pH = 7, adsorbent dose = 0.125 g and contact time = 45 min. The experimental isotherms data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm equations and the results indicated that the Freundlich isotherm showed a better fit for CR adsorption. Thermodynamic parameters were calculated from Van't Hoff plot, confirming that the adsorption process was spontaneous and exothermic. The high CR adsorptive removal ability and regeneration efficiency of this adsorbent suggest its applicability in industrial/household systems and data generated would help in further upscaling of the adsorption process.

Removal of Direct Red 23 from aqueous solution using corn stalks: Isotherms, kinetics and thermodynamic studies

NASA Astrophysics Data System (ADS)

Fathi, M. R.; Asfaram, A.; Farhangi, A.

2015-01-01

The objective of this study was to assess the suitability and efficiency of corn stalk (CS) for the removal of diazo dye Direct Red 23 (DR23) from aqueous solutions. The effect of different variables in the batch method as a function of solution pH, contact time, initial dye concentration, CS amount, temperature, and so forth by the optimization method has been investigated. The color reduction was monitored by spectrophotometry at 503 nm before and after DR23 adsorption on the CS, and the removal percentage was calculated using the difference in absorbance. The sorption processes followed the pseudo second order in addition to intraparticle diffusion kinetics models with a good correlation coefficient with the overall entire adsorption of DR23 on adsorbent. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D-R). It was found that adsorption of DR23 on CS well with the Freindlich isotherm model, implying monolayer coverage of dye molecules onto the surface of the adsorbent. More than 99% removal efficiency was obtained within 10 min at adsorbent dose of 0.2 g for initial dye concentration of 10-90 mg L-1 at pH 3. Various thermodynamic parameters, such as Gibbs free energy, entropy, and enthalpy, of the ongoing adsorption process have been calculated. Judgment based on the obtained results of thermodynamic values shows the spontaneous and endothermic nature adsorption processes on adsorbent.

Upgrade to Ion Exchange Modeling for Removal of Technetium from Hanford Waste Using SuperLig® 639 Resin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamm, L.; Smith, F.; Aleman, S.

2013-05-16

This report documents the development and application of computer models to describe the sorption of pertechnetate [TcO₄⁻], and its surrogate perrhenate [ReO₄⁻], on SuperLig® 639 resin. Two models have been developed: 1) A thermodynamic isotherm model, based on experimental data, that predicts [TcO₄⁻] and [ReO₄⁻] sorption as a function of solution composition and temperature and 2) A column model that uses the isotherm calculated by the first model to simulate the performance of a full-scale sorption process. The isotherm model provides a synthesis of experimental data collected from many different sources to give a best estimate prediction of the behaviormore » of the pertechnetate-SuperLig® 639 system and an estimate of the uncertainty in this prediction. The column model provides a prediction of the expected performance of the plant process by determining the volume of waste solution that can be processed based on process design parameters such as column size, flow rate and resin physical properties.« less

Determination of the amount of gas adsorption on SiO2/Si(100) surfaces to realize precise mass measurement

NASA Astrophysics Data System (ADS)

Mizushima, S.

2004-06-01

The adsorption isotherms on SiO2/Si(100) surfaces were measured using a vacuum mass comparator. Samples with a surface area difference of 816.6 cm2 were used for the measurement, and a substitution weighing method was adopted to reduce the uncertainty due to the drift and non-linearity of the indication of the mass comparator. We measured adsorption isotherms of water vapour on the SiO2/Si(100) surfaces outgassed at a temperature of 500 °C and found that dissociative adsorption caused an irreversible increase of 0.028 µg cm-2 with an uncertainty of 0.004 µg cm-2 (k = 1). We also found that the physical adsorption of water molecules on hydroxylated surfaces had a monolayer capacity of 0.004 µg cm-2 with an uncertainty of 0.002 µg cm-2 (k = 1). In addition, the adsorption isotherms for ethanol vapour and n-octane vapour, which were different from water vapour in adsorption properties, were measured and analysed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rioux, Robert M.

In this work, we have primarily utilized isothermal titration calorimetry (ITC) and complimentary catalyst characterization techniques to study and assess the impact of solution conditions (i.e., solid-liquid) interface on the synthesis of heterogeneous and electro-catalysts. Isothermal titration calorimetry is well-known technique from biochemistry/physics, but has been applied to a far lesser extent to characterize buried solid-liquid interfaces in materials science. We demonstrate the utility and unique information provided by ITC for two distinct catalytic systems. We explored the thermodynamics associated catalyst synthesis for two systems: (i) ion-exchange or strong electrostatic adsorption for Pt and Pd salts on silica and aluminamore » materials (ii) adsorption to provide covalent attachment of metal and metal-oxo clusters to Dion-Jacobsen perovskite materials.« less

Methods of studying aging and stabilization of spray-congealed solid dispersions with carnauba wax. 1. Microcalorimetric investigation.

PubMed

Emås, M; Nyqvist, H

2000-03-20

Rapidly cooled materials are often unstable as a result of changes in their physical properties due to imperfect crystallization. In the process of spray-congealing, melted material is atomized into droplets which very quickly solidify. This increases the possibility of the material crystallizing in different metastable forms. In this study it is shown that isothermal microcalorimetry can be used to observe the change in the thermodynamic state of spray-congealed carnauba wax during storage. In order to accelerate the thermodynamic change in the spray-congealed wax, three annealing procedures have been developed and compared using isothermal microcalorimetry. By means of annealing, a spray-congealed product closer to a thermodynamically stable state has been achieved.

Adsorption characteristics of selected pharmaceuticals and an endocrine disrupting compound-Naproxen, carbamazepine and nonylphenol-on activated carbon.

PubMed

Yu, Zirui; Peldszus, Sigrid; Huck, Peter M

2008-06-01

The adsorption of two representative pharmaceutically active compounds (PhACs) (naproxen and carbamazepine) and one endocrine disrupting compound (nonylphenol) were evaluated on two types of activated carbon. When determining their isotherms at environmentally relevant concentration levels, it was found that at this low concentration range (10-800 ng/L), removals of the target compounds were contrary to expectations based on their hydrophobicity. Nonylphenol (log K(ow) 5.8) was most poorly adsorbed, whereas carbamazepine (log K(ow) 2.45) was most adsorbable. Nonylphenol Freundlich isotherms at this very low concentration range had a much higher 1/n compared to isotherms at much higher concentrations. This indicates that extrapolation from an isotherm obtained at a high concentration range to predict the adsorption of nonylphenol at a concentration well below the range of the original isotherm, leads to a substantial overestimation of its removals. Comparison of isotherms for the target compounds to those for other conventional micropollutants suggested that naproxen and carbamazepine could be effectively removed by applying the same dosage utilized to remove odorous compounds (geosmin and MIB) at very low concentrations. The impact of competitive adsorption by background natural organic matter (NOM) on the adsorption of the target compounds was quantified by using the ideal adsorbed solution theory (IAST) in combination with the equivalent background compound (EBC) approach. The fulfilment of the requirements for applying the simplified IAST-EBC model, which leads to the conclusion that the percentage removal of the target compounds at a given carbon dosage is independent of the initial contaminant concentration, was confirmed for the situation examined in the paper. On this basis it is suggested that the estimated minimum carbon usage rates (CURs) to achieve 90% removal of these emerging contaminants would be valid at concentrations of less than 500 ng/L in natural water.

[Dynamics of Irreversible Evaporation of a Water-Protein Droplet and a Problem of Structural and Dynamical Experiments with Single Molecules].

PubMed

Shaitan, K V; Armeev, G A; Shaytan, A K

2016-01-01

We discuss the effect of isothermal and adiabatic evaporation of water on the state of a water-protein droplet. The discussed problem is of current importance due to development of techniques to perform single molecule experiments using free electron lasers. In such structure-dynamic experiments the delivery of a sample into the X-ray beam is performed using the microdroplet injector. The time between the injection and delivery is in the order of microseconds. In this paper we developed a specialized variant of all-atom molecular dynamics simulations for the study of irreversible isothermal evaporation of the droplet. Using in silico experiments we determined the parameters of isothermal evaporation of the water-protein droplet with the sodium and chloride ions in the concentration range of 0.3 M at different temperatures. The energy of irreversible evaporation determined from in silico experiments at the initial stages of evaporation virtually coincides with the specific heat of evaporation for water. For the kinetics of irreversible adiabatic evaporation an exact analytical solution was obtained in the limit of high thermal conductivity of the droplet (or up to the droplet size of -100 Å). This analytical solution incorporates parameters that are determined using in silico. experiments on isothermal droplet evaporation. We show that the kinetics of adiabatic evaporation and cooling of the droplet scales with the droplet size. Our estimates of the water-protemi droplet. freezing rate in the adiabatic regime in a vacuum chamber show that additional techniques for stabilizing the temperature inside the droplet should be used in order to study the conformational transitions of the protein in single molecules. Isothermal and quasi-isothermal conditions are most suitable for studying the conformational transitions upon object functioning. However, in this case it is necessary to take into account the effects of dehydration and rapid increase of ionic strength in an aqueous microenvironment surrounding the protein.

Time-Dependent Behavior of a Graphite/Thermoplastic Composite and the Effects of Stress and Physical Aging

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Feldman, Mark

1995-01-01

Experimental studies were performed to determine the effects of stress and physical aging on the matrix dominated time dependent properties of IM7/8320 composite. Isothermal tensile creep/aging test techniques developed for polymers were adapted for testing of the composite material. Time dependent transverse and shear compliance's for an orthotropic plate were found from short term creep compliance measurements at constant, sub-T(8) temperatures. These compliance terms were shown to be affected by physical aging. Aging time shift factors and shift rates were found to be a function of temperature and applied stress.

Characterization of Phase Separation Propensity for Amorphous Spray Dried Dispersions.

PubMed

McNamara, Daniel; Yin, Shawn; Pan, Duohai; Crull, George; Timmins, Peter; Vig, Balvinder

2017-02-06

A generalized screening approach, applying isothermal calorimetry at 37 °C 100% RH, to formulations of spray dried dispersions (SDDs) for two active pharmaceutical ingredients (APIs) (BMS-903452 and BMS-986034) is demonstrated. APIs 452 and 034, with similar chemotypes, were synthesized and promoted during development for oral dosing. Both APIs were formulated as SDDs for animal exposure studies using the polymer hydroxypropylmethlycellulose acetyl succinate M grade (HPMCAS-M). 452 formulated at 30% (wt/wt %) was an extremely robust SDD that was able to withstand 40 °C 75% RH open storage conditions for 6 months with no physical evidence of crystallization or loss of dissolution performance. Though 034 was a chemical analogue with similar physical chemical properties to 452, a physically stable SDD of 034 could not be formulated in HPMCAS-M at any of the drug loads attempted. This study was used to develop experience with specific physical characterization laboratory techniques to evaluate the physical stability of SDDs and to characterize the propensity of SDDs to phase separate and possibly crystallize. The screening strategy adopted was to stress the formulated SDDs with a temperature humidity screen, within the calorimeter, and to apply orthogonal analytical techniques to gain a more informed understanding of why these SDDs formulated with HPMCAS-M demonstrated such different physical stability. Isothermal calorimetry (thermal activity monitor, TAM) was employed as a primary stress screen wherein the SDD formulations were monitored for 3 days at 37 °C 100% RH for signs of phase separation and possible crystallization of API. Powder X-ray diffraction (pXRD), modulated differential scanning calorimetry (mDSC), Fourier transform infrared spectroscopy (FTIR), and solid state nuclear magnetic resonance (ssNMR) were all used to examine formulated SDDs and neat amorphous drug. 452 SDDs formulated at 30% (wt/wt %) or less did not show phase separation behavior upon exposure to 37 °C 100% RH for 3 days. 034 SDD formulations from 10 through 50% (wt/wt %) all demonstrated thermal traces consistent with exothermic phase separation events over 3 days at 37 °C 100% RH in the TAM. However, only the 15, 30, and 50% containing 034 samples showed pXRD patterns consistent with crystalline material in post-TAM samples. Isothermal calorimetry is a useful screening tool to probe robust SDD physical performance and help investigate the level of drug polymer miscibility under a humid stress. Orthogonal analytical techniques such as pXRD, ssNMR, and FTIR were key in this SDD formulation screening to gain physical understanding and confirm or refute whether physical changes occur during the observed thermal events characterized by the calorimetric screening experiments.

Improvement of pesticide adsorption capacity of cellulose fibre by high-energy irradiation-initiated grafting of glycidyl methacrylate

NASA Astrophysics Data System (ADS)

Takács, Erzsébet; Wojnárovits, László; Koczog Horváth, Éva; Fekete, Tamás; Borsa, Judit

2012-09-01

Cellulose as a renewable raw material was used for preparation of adsorbent of organic impurities in wastewater treatment. Hydrophobic surface of cellulose substrate was developed by grafting glycidyl methacrylate in simultaneous grafting using gamma irradiation initiation. Water uptake of cellulose significantly decreased while adsorption of phenol and a pesticide molecule (2,4-dichlorophenoxyacetic acid: 2,4-D) increased upon grafting. Adsorption equilibrium data fitted the Freundlich isotherm for both solutes.

Co-modified MCM-41 as an effective adsorbent for levofloxacin removal from aqueous solution: optimization of process parameters, isotherm, and thermodynamic studies.

PubMed

Jin, Ting; Yuan, Wenhua; Xue, Yujie; Wei, Hong; Zhang, Chaoying; Li, Kebin

2017-02-01

Antibiotics are emerging contaminants due to their potential risks to human health and ecosystems. Poor biodegradability makes it necessary to develop effective physical-chemical methods to eliminate these contaminants from water. The cobalt-modified MCM-41 was prepared by a one-pot hydrothermal method and characterized by SAXRD, N 2 adsorption-desorption, SEM, UV-Vis DR, and FTIR spectroscopy. The results revealed that the prepared 3% Co-MCM-41 possessed mesoporous structure with BET surface areas at around 898.5 m 2 g -1 . The adsorption performance of 3% Co-MCM-41 toward levofloxacin (LVF) was investigated by batch experiments. The adsorption of LVF on 3% Co-MCM-41 was very fast and reached equilibrium within 2 h. The adsorption kinetics followed the pseudo-second-order kinetic model with the second-order rate constants in the range of 0.00198-0.00391 g mg -1  min -1 . The adsorption isotherms could be well represented by the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. Nevertheless, D-R isotherm provided the best fit based on the coefficient of determination and average relative error values. The mean free energy of adsorption (E) calculated from D-R model was about 11 kJ mol -1 , indicating that the adsorption was mainly governed by a chemisorption process. Moreover, the adsorption capacity was investigated as a function of pH, adsorbent dosage, LVF concentration, and temperature with help of respond surface methodology (RSM). A quadratic model was established, and an optimal condition was obtained as follows: pH 8.5, adsorbent dosage of 1 g L -1 , initial LVF concentration of 119.8 mg L -1 , and temperature of 31.6 °C. Under the optimal condition, the adsorption capacity of 3% Co-MCM-41 to LVF could reach about 108.1 mg g -1 . The solution pH, adsorbent dosage, LVF concentration, and a combination of adsorbent dose and LVF concentration were significant factors affecting the adsorption process. The adsorption thermodynamic functions were also determined. The negative ΔH 0 (-33.50 kJ mol -1 ) and ΔS 0 (-43.57 J mol -1  K -1 ) suggested that the adsorption was an exothermic process accompanied by decreasing disorder. This study may indicate that 3% Co-MCM-41 is a promising adsorbent for removing emerging pollutants of LVF from water.

Competitive sorption of organic contaminants in chalk.

PubMed

Graber, E R; Borisover, M

2003-12-01

In the Negev desert, Israel, a chemical industrial complex is located over fractured Eocene chalk formations where transfer of water and solutes between fracture voids and matrix pores affects migration of contaminants in the fractures due to diffusion into the chalk matrix. This study tests sorption and sorption competition between contaminants in the chalk matrix to make it possible to evaluate the potential for contaminant attenuation during transport in fractures. Single solute sorption isotherms on chalk matrix material for five common contaminants (m-xylene, ametryn, 1,2-dichloroethane, phenanthrene, and 2,4,6-tribromophenol) were found to be nonlinear, as confirmed in plots of Kd versus initial solution concentration. Over the studied concentration ranges, m-xylene Kd varied by more than a factor of 100, ametryn Kd by a factor of 4, 1,2-dichloroethane Kd by more than a factor of 3, phenanthrene Kd by about a factor of 2, and 2,4,6-tribromophenol Kd by a factor of 10. It was earlier found that sorption is to the organic matter component of the chalk matrix and not to the mineral phases (Chemosphere 44 (2001) 1121). Nonlinear sorption isotherms indicate that there is at least some finite sorption domain. Bi-solute competition experiments with 2,4,6-tribromophenol as the competitor were designed to explore the nature of the finite sorption domain. All of the isotherms in the bi-solute experiments are more linear than in the single solute experiments, as confirmed by smaller variations in Kd as a function of initial solution concentration. For both m-xylene and ametryn, there is a small nonlinear component or domain that was apparently not susceptible to competition by 2,4,6-tribromophenol. The nonlinear sorption domain(s) is best expressed at low solution concentrations. Inert-solvent-normalized single and bi-solute sorption isotherms demonstrate that ametryn undergoes specific force interactions with the chalk sorbent. The volume percent of phenanthrene sorbed at the liquid solubility limit is calculated to be 13% v:v in both the single and bi-solute experiments. This value exceeds what may be reasonably interpreted as partitioning of phenanthrene into organic matter, despite the relative linearity of the phenanthrene sorption isotherm (compared with other compounds) in both single and bi-solute systems.

Role of physical properties of liquids in cavitation erosion

NASA Technical Reports Server (NTRS)

Thiruvengadam, A.

1974-01-01

The dependence of erosion rates on the ambient temperature of water is discussed. The assumption that the gas inside the bubble is compressed adiabatically during collapse gives better agreement with experiments than the assumption that the gas is isothermally compressed. Acoustic impedance is an important liquid parameter that governs the erosion intensity in vibratory devices. The investigation reveals that the major physical properties of liquids governing the intensity of erosion include density, sound speed, surface tension, vapor pressure, gas content, and nuclei distribution.

Cooperative CO2 Absorption Isotherms from a Bifunctional Guanidine and Bifunctional Alcohol.

PubMed

Steinhardt, Rachel; Hiew, Stanley C; Mohapatra, Hemakesh; Nguyen, Du; Oh, Zachary; Truong, Richard; Esser-Kahn, Aaron

2017-12-27

Designing new liquids for CO 2 absorption is a challenge in CO 2 removal. Here, achieving low regeneration energies while keeping high selectivity and large capacity are current challenges. Recent cooperative metal-organic frameworks have shown the potential to address many of these challenges. However, many absorbent systems and designs rely on liquid capture agents. We present herein a liquid absorption system which exhibits cooperative CO 2 absorption isotherms. Upon introduction, CO 2 uptake is initially suppressed, followed by an abrupt increase in absorption. The liquid consists of a bifunctional guanidine and bifunctional alcohol, which, when dissolved in bis(2-methoxyethyl) ether, forms a secondary viscous phase within seconds in response to increases in CO 2 . The precipitation of this second viscous phase drives CO 2 absorption from the gas phase. The isotherm of the bifunctional system differs starkly from the analogous monofunctional system, which exhibits limited CO 2 uptake across the same pressure range. In our system, CO 2 absorption is strongly solvent dependent. In DMSO, both systems exhibit hyperbolic isotherms and no precipitation occurs. Subsequent 1 H NMR experiments confirmed the formation of distinct alkylcarbonate species having either one or two molecules of CO 2 bound. The solvent and structure relationships derived from these results can be used to tailor new liquid absorption systems to the conditions of a given CO 2 separation process.

An overview of elevated temperature damage mechanisms and fatigue behavior of a unidirectional SCS-6/Ti-15-3 composite

NASA Technical Reports Server (NTRS)

Castelli, Michael G.; Gayda, John

1993-01-01

The fatigue behavior of a unidirectionally reinforced titanium matrix composite (TMC), SiC/Ti-15-3, was thoroughly characterized to support life prediction modeling of advanced TMC disks designed for gas turbine engine applications. The results of this coupon-level experimental investigation are reviewed. On a stress basis, the isothermal fatigue behavior of the (0 deg) TMC revealed significant improvements over the unreinforced matrix. In contrast, the (90 deg) TMC exhibited degraded properties and lives for similar comparisons. This was attributed to the weak fiber/matrix interfacial bond. Encasing the (0 deg) TMC with a Ti-15-3 case did not affect isothermal fatigue lives at higher strain levels. However, at lower strain levels, rapid initiation and propagation of large fatigue cracks in the case degraded the fatigue lives. Thermomechanical fatigue (TMF) lives were significantly reduced for the (0 deg) TMC when compared to isothermal lives. At high strains, in-phase TMF produced extremely short lives. This degradation was attributed to fiber overload failures brought about by stress relaxation in the matrix. At low strains, out-of-phase TMF conditions became life limiting. Environment-assisted surface cracking was found to accelerate fatigue failure. This produced extensive matrix damage with minimal fiber damage. For the (90 deg) TMC, TMF conditions did not promote an additional degradation in cyclic life beyond that observed under isothermal conditions.

Protostellar Disk Instabilities and the Formation of Substellar Companions

NASA Astrophysics Data System (ADS)

Pickett, Brian K.; Durisen, Richard H.; Cassen, Patrick; Mejia, Annie C.

2000-09-01

Recent numerical simulations of self-gravitating protostellar disks have suggested that gravitational instabilities can lead to the production of substellar companions. In these simulations, the disk is typically assumed to be locally isothermal; i.e., the initial, axisymmetric temperature in the disk remains everywhere unchanged. Such an idealized condition implies extremely efficient cooling for outwardly moving parcels of gas. While we have seen disk disruption in our own locally isothermal simulations of a small, massive protostellar disk, no long-lived companions formed as a result of the instabilities. Instead, thermal and tidal effects and the complex interactions of the disk material prevented permanent condensations from forming, despite the vigorous growth of spiral instabilities. In order to compare our results more directly with those of other authors, we here present three-dimensional evolutions of an older, larger, but less massive protostellar disk. We show that potentially long-lived condensations form only for the extreme of local isothermality, and then only when severe restrictions are placed on the natural tendency of the protostellar disk to expand in response to gravitational instabilities. A more realistic adiabatic evolution leads to vertical and radial expansion of the disk but no clump formation. We conclude that isothermal disk calculations cannot demonstrate companion formation by disk fragmentation but only suggest it at best. It will be necessary in future numerical work on this problem to treat the disk thermodynamics more realistically.

Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology for Effective Removal of Cr(VI) Using Fungal Biomass

PubMed Central

Chidambaram, Ramalingam

2015-01-01

Biosorption is a promising alternative method to replace the existing conventional technique for Cr(VI) removal from the industrial effluent. In the present experimental design, the removal of Cr(VI) from the aqueous solution was studied by Aspergillus niger MSR4 under different environmental conditions in the batch systems. The optimum conditions of biosorption were determined by investigating pH (2.0) and temperature (27°C). The effects of parameters such as biomass dosage (g/L), initial Cr(VI) concentration (mg/L) and contact time (min) on Cr(VI) biosorption were analyzed using a three parameter Box–Behnken design (BBD). The experimental data well fitted to the Langmuir isotherm, in comparison to the other isotherm models tested. The results of the D-R isotherm model suggested that a chemical ion-exchange mechanism was involved in the biosorption process. The biosorption process followed the pseudo-second-order kinetic model, which indicates that the rate limiting step is chemisorption process. Fourier transform infrared (FT-IR) spectroscopic studies revealed the possible involvement of functional groups, such as hydroxyl, carboxyl, amino and carbonyl group in the biosorption process. The thermodynamic parameters for Cr(VI) biosorption were also calculated, and the negative ∆Gº values indicated the spontaneous nature of biosorption process. PMID:25786227

Annealing effect on thermodynamic and physical properties of mesoporous silicon: A simulation and nitrogen sorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Pushpendra, E-mail: pkumar-iitd@yahoo.com; Huber, Patrick, E-mail: patrick.huber@tuhh.de

Discovery of porous silicon formation in silicon substrate in 1956 while electro-polishing crystalline Si in hydrofluoric acid (HF), has triggered large scale investigations of porous silicon formation and their changes in physical and chemical properties with thermal and chemical treatment. A nitrogen sorption study is used to investigate the effect of thermal annealing on electrochemically etched mesoporous silicon (PS). The PS was thermally annealed from 200°C to 800°C for 1 hr in the presence of air. It was shown that the pore diameter and porosity of PS vary with annealing temperature. The experimentally obtained adsorption / desorption isotherms show hysteresis typicalmore » for capillary condensation in porous materials. A simulation study based on Saam and Cole model was performed and compared with experimentally observed sorption isotherms to study the physics behind of hysteresis formation. We discuss the shape of the hysteresis loops in the framework of the morphology of the layers. The different behavior of adsorption and desorption of nitrogen in PS with pore diameter was discussed in terms of concave menisci formation inside the pore space, which was shown to related with the induced pressure in varying the pore diameter from 7.2 nm to 3.4 nm.« less

Relation between some two- and three-parameter isotherm models for the sorption of methylene blue onto lemon peel.

PubMed

Kumar, K Vasanth; Porkodi, K

2006-12-01

Equilibrium uptake of methylne blue onto lemon peel was fitted to the 2 two-parameter isotherm models namely Freundlich and Langmuir and 3 six-parameter isotherm models namely Redlich-Peterson, Toth, Radke-Prausnitz, Fritz-Schluender, Vieth-Sladek and Sips isotherms by non-linear method. A comparison between two-parameter and three-parameter isotherms was reported. The best fitting isotherm was the Sips isotherm followed by Langmuir isotherm and Redlich-Peterson isotherm equation. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity. Radke-Prausnitz, Toth, Vieth-Sladek isotherm were the same when the Toth isotherm constant, n(T) and the Radke-Prausnitz isotherm, m(RP) are equal to unity and when the Vieth-Sladek isotherm constant, K(VS) equals zero. The sorption capacity of lemon peel for methylene blue uptake was found to be 29 mg/g.

Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa.

PubMed

Noroozi, B; Sorial, G A; Bahrami, H; Arami, M

2007-01-02

In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).

Synthesis of zeolite/nickel ferrite/sodium alginate bionanocomposite via a co-precipitation technique for efficient removal of water-soluble methylene blue dye.

PubMed

Bayat, Mahsa; Javanbakht, Vahid; Esmaili, Javad

2018-05-05

In this study, we sought to synthesize magnetic nanocomposite of zeolite/nickel ferrite through co-precipitation method and modify its surface by sodium alginate to enhance its methylene blue adsorption capacity and to prevent its oxidation. Nanocomposite characteristics were investigated by SEM, VSM, XRD and FTIR analyses. The results indicate that nanocomposite synthesis and modification has been completely successful. Adsorption thermodynamics, kinetics, and isotherms were examined and parameters were optimized by Minitab software using experimental design method, response surface methodology and Box-Behnken design. The highest capacity of methylene blue adsorption from the aqueous solution obtained at optimal pH of 5, the initial dye concentration of 10 mg/L and an adsorbent amount of 0.03 g was about 54.05 mg/g. Analyzing kinetic data of adsorption experiments confirmed that adsorption process complies with the pseudo-second-order kinetic model. Assessing equilibrium isotherm data at different temperatures showed that these data are in good agreement with Langmuir isotherm model. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of hydrophobicity of pharmaceuticals and personal care products for adsorption on activated carbon: Adsorption isotherms, kinetics and mechanism.

PubMed

Kaur, Harkirat; Bansiwal, Amit; Hippargi, Girivyankatesh; Pophali, Girish R

2017-09-11

Adsorption of three pharmaceuticals and personal care products (PPCPs), namely caffeine, ibuprofen and triclosan on commercial powdered activated carbon was examined in aqueous medium. The contaminants were chosen based on their diverse log K ow (octanol-water partition coefficient) viz. - 0.07 for caffeine, 3.97 for ibuprofen and 4.76 for triclosan to examine the role of hydrophobicity on adsorption process. The adsorbent characterisation was achieved using BET surface area, SEM, pore size distribution studies and FTIR. Influence of mass of PAC, contact time, solution pH and initial concentration on adsorption capacity of PAC was studied. Adsorption isotherms and kinetics were applied to establish the mechanism of adsorption. The kinetics followed pseudo-second order with physisorption occurring through particle diffusion. The Freundlich model fitted best among the isotherm models. The adsorption capacity increased in the order CFN < IBU < TCS which correlates with increasing hydrophobicity (log K ow ), molecular weight and decreasing water solubility, respectively. We conclude that micro-pollutant hydrophobicity contributes towards adsorption on activated carbon.

Oxidation Kinetics of Cast TiAl3

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Humphrey, D. L.

1992-01-01

The isothermal oxidation kinetics of the TiAl3 compound over a wide temperature range is documented, and these rates are related to exclusive alpha-Al2O3 scale growth. The specific weight change vs time curves are shown. Two abnormalities are immediately apparent. One is that a rapid initial uptake of oxygen occurs at times less than 5 h, followed by a lower oxidation rate at longer times, for tests at 900 C and below. The other is that the final weight changes for the 700, 800, and 900 C tests are not in the sequence expected with respect to temperature. Isothermal oxidation of drop cast TiAl above 1000 C was found to exhibit parabolic oxidation controlled by protective alpha-Al2O3 scale formation. TiAl is the only phase in the binary Ti-Al system that forms exclusive scales of alpha-Al2O3 in isothermal oxidation. High anomalous rates at short times and at temperatures below 1000 C resulted from the internal oxidation of a second phase of aluminum.

Biosorption of landfill leachate by Phanerochaete sp. ISTL01: isotherms, kinetics and toxicological assessment.

PubMed

Ghosh, Pooja; Thakur, Indu Shekhar

2017-07-01

The study investigates the ability of fungus Phanerochaete sp. ISTL01 for biosorption of color from landfill leachate. Batch mode experiments were conducted to study the effects of pH, temperature, adsorbent dose, contact time and initial leachate concentration on biosorption. Maximum biosorption capacity was determined as 17.73 mg g -1 of biomass. Equilibrium isotherms and kinetics were further studied. The biosorption data were found to fit well to the Freundlich isotherm and pseudo-second-order kinetic model. The value of activation energy suggested that chemisorption mechanism was involved. Biosorption efficiency was also evaluated by the Methyltetrazolium (MTT) assay for cytotoxicity and alkaline comet assay in HepG2 human hepato-carcinoma cells. The fungus reduced toxicity as shown by 1.3-fold increase in MTT EC 50 and 1.5- and 1.1-fold reduction in Tail moment and Olive tail moment, respectively, after 12 h biosorption. The fungus showed good biosorption characteristics in terms of contaminant-level reduction per unit mass of adsorbent, process kinetics and toxicity reduction, envisaging its application in leachate treatment.

Unusual isothermal multimerization and amplification by the strand-displacing DNA polymerases with reverse transcription activities.

PubMed

Wang, Guoping; Ding, Xiong; Hu, Jiumei; Wu, Wenshuai; Sun, Jingjing; Mu, Ying

2017-10-24

Existing isothermal nucleic acid amplification (INAA) relying on the strand displacement activity of DNA polymerase usually requires at least two primers. However, in this paper, we report an unusual isothermal multimerization and amplification (UIMA) which only needs one primer and is efficiently initiated by the strand-displacing DNA polymerases with reverse transcription activities. On electrophoresis, the products of UIMA present a cascade-shape band and they are confirmed to be multimeric DNAs with repeated target sequences. In contrast to current methods, UIMA is simple to product multimeric DNA, due to the independent of multiple primers and rolling circle structures. Through assaying the synthesized single-stranded DNA targets, UIMA performs high sensitivity and specificity, as well as the universality. In addition, a plausible mechanism of UIMA is proposed, involving short DNA bending, mismatch extension, and template slippage. UIMA is a good explanation for why nonspecific amplification easily happens in existing INAAs. As the simplest INAA till now, UIMA provides a new insight for deeply understanding INAA and opens a new avenue for thoroughly addressing nonspecific amplification.

Characterization by thermoelectric power of a commercial aluminum-iron-silicon alloy (8011) during isothermal precipitation

NASA Astrophysics Data System (ADS)

Luiggi, Ney José A.

1998-11-01

We have characterized a commercial 8011 (Al-Fe-Si) alloy by studying samples under different initial states of strain hardening and iron and silicon supersaturation using thermoelectric power as a measurement technique. Isothermal kinetics of precipitation are obtained in the temperature range between 225 °C and 600 °C. We determine the atom fraction precipitated for each microstructural condition, identifying the dominant alloying additions and evaluating the typical parameters of the precipitated phases, such as, for example, the apparent activation energy. Finally, we determine the time-temperature-transformation (TTT) diagrams. Our results prove that iron is the alloying addition that controls the precipitation kinetics of the 8011 alloy in the temperature range studied.

Imposition of physical parameters in dissipative particle dynamics

NASA Astrophysics Data System (ADS)

Mai-Duy, N.; Phan-Thien, N.; Tran-Cong, T.

2017-12-01

In the mesoscale simulations by the dissipative particle dynamics (DPD), the motion of a fluid is modelled by a set of particles interacting in a pairwise manner, and it has been shown to be governed by the Navier-Stokes equation, with its physical properties, such as viscosity, Schmidt number, isothermal compressibility, relaxation and inertia time scales, in fact its whole rheology resulted from the choice of the DPD model parameters. In this work, we will explore the response of a DPD fluid with respect to its parameter space, where the model input parameters can be chosen in advance so that (i) the ratio between the relaxation and inertia time scales is fixed; (ii) the isothermal compressibility of water at room temperature is enforced; and (iii) the viscosity and Schmidt number can be specified as inputs. These impositions are possible with some extra degrees of freedom in the weighting functions for the conservative and dissipative forces. Numerical experiments show an improvement in the solution quality over conventional DPD parameters/weighting functions, particularly for the number density distribution and computed stresses.

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

NASA Astrophysics Data System (ADS)

Simmonds, Tegan; Hayes, Peter C.

2017-12-01

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

On Faraday Instability in Magnetic Liquids: Ince-Erdelyi Approach Applied to the Hill Equation Describing Oscillations of a Ferrofluid Free Surface

NASA Astrophysics Data System (ADS)

Hennenberg, M.; Slavtchev, S.; Valchev, G.

2013-12-01

When an isothermal ferrofluid is submitted to an oscillating magnetic field, the initially motionless liquid free surface can start to oscillate. This physical phenomenon is similar to the Faraday instability for usual Newtonian liquids subjected to a mechanical oscillation. In the present paper, we consider the magnetic field as a sum of a constant part and a time periodic part. Two different cases for the constant part of the field, being vertical in the first one or horizontal in the second one are studied. Assuming both ferrofluid magnetization and magnetic field to be collinear, we develop the linear stability analysis of the motionless reference state taking into account the Kelvin magnetic forces. The Laplace law describing the free surface deformation reduces to Hill's equation, which is studied using the classical method of Ince and Erdelyi. Inside this framework, we obtain the transition conditions leading to the free surface oscillations.

Characterization of biochars derived from agriculture wastes and their adsorptive removal of atrazine from aqueous solution: A comparative study.

PubMed

Liu, Na; Charrua, Alberto Bento; Weng, Chih-Huang; Yuan, Xiaoling; Ding, Feng

2015-12-01

The physicochemical properties of biochars produced from soybeans (SBB), corn stalks (CSB), rice stalks (RSB), poultry manure (PMB), cattle manure (CMB), and pig manure (PgMB) and their adsorption characteristics of atrazine were investigated. The adsorption capacity increased with the increase of temperature and initial atrazine concentration. More atrazine was removed from basic solutions than acidic solutions, due to the effects of adsorption and hydrolysis. The Freundlich isotherm adsorption parameters indicated that the adsorption capacity decreased in the order SBB>RSB>CMB>CSB>PMB>PgMB, which is associated to the pore volume of biochars. The total pore volume and biochar pH were concluded to play important roles in determining the adsorption capacity, and they may have contributed to physical adsorption mechanisms dominating the overall adsorption process (the low activation energy for all of the biochars). Modified Freundlich and intraparticle diffusion models were used to describe the kinetics of the adsorption process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory.

PubMed

Heinen, Jurn; Burtch, Nicholas C; Walton, Krista S; Fonseca Guerra, Célia; Dubbeldam, David

2016-12-12

For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction of lactoferrin and lysozyme with casein micelles.

PubMed

Anema, Skelte G; de Kruif, C G Kees

2011-11-14

On addition of lactoferrin (LF) to skim milk, the turbidity decreases. The basic protein binds to the caseins in the casein micelles, which is then followed by a (partial) disintegration of the casein micelles. The amount of LF initially binding to casein micelles follows a Langmuir adsorption isotherm. The kinetics of the binding of LF could be described by first-order kinetics and similarly the disintegration kinetics. The disintegration was, however, about 10 times slower than the initial adsorption, which allowed investigating both phenomena. Kinetic data were also obtained from turbidity measurements, and all data could be described with one equation. The disintegration of the casein micelles was further characterized by an activation energy of 52 kJ/mol. The initial increase in hydrodynamic size of the casein micelles could be accounted for by assuming that it would go as the cube root of the mass using the adsorption and disintegration kinetics as determined from gel electrophoresis. The results show that LF binds to casein micelles and that subsequently the casein micelles partly disintegrate. All micelles behave in a similar manner as average particle size decreases. Lysozyme also bound to the casein micelles, and this binding followed a Langmuir adsorption isotherm. However, lysozyme did not cause the disintegration of the casein micelles.

Development of a quantitative loop-mediated isothermal amplification assay for the field detection of Erysiphe necator

USDA-ARS?s Scientific Manuscript database

Plant pathogen detection systems have been useful tools to monitor inoculum presence and initiate management schedules. More recently, a LAMP assay was successfully designed for field use in the grape powdery mildew pathosystem; however, false negatives or false positives were prevalent in grower-co...

Biosorption of Acid Black 172 and Congo Red from aqueous solution by nonviable Penicillium YW 01: kinetic study, equilibrium isotherm and artificial neural network modeling.

PubMed

Yang, Yuyi; Wang, Guan; Wang, Bing; Li, Zeli; Jia, Xiaoming; Zhou, Qifa; Zhao, Yuhua

2011-01-01

The main objective of this work was to investigate the biosorption performance of nonviable Penicillium YW 01 biomass for removal of Acid Black 172 metal-complex dye (AB) and Congo Red (CR) in solutions. Maximum biosorption capacities of 225.38 and 411.53 mg g(-1) under initial dye concentration of 800 mg L(-1), pH 3.0 and 40 °C conditions were observed for AB and CR, respectively. Biosorption data were successfully described with Langmuir isotherm and the pseudo-second-order kinetic model. The Weber-Morris model analysis indicated that intraparticle diffusion was the limiting step for biosorption of AB and CR onto biosorbent. Analysis based on the artificial neural network and genetic algorithms hybrid model indicated that initial dye concentration and temperature appeared to be the most influential parameters for biosorption process of AB and CR onto biosorbent, respectively. Characterization of the biosorbent and possible dye-biosorbent interaction were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. Copyright © 2010 Elsevier Ltd. All rights reserved.

Biosorption of alpacide blue from aqueous solution by lignocellulosic biomass: Luffa cylindrica fibers.

PubMed

Kesraoui, Aida; Moussa, Asma; Ali, Ghada Ben; Seffen, Mongi

2016-08-01

The aim of the present work is to develop an effective and inexpensive pollutant-removal technology using lignocellulosic fibers: Luffa cylindrica, for the biosorption of an anionic dye: alpacide blue. The influence of some experimental parameters such as pH, temperature, initial concentration of the polluted solution, and mass of the sorbent L. cylindrica on the biosorption of alpacide blue by L. cylindrica fibers has been investigated. Optimal parameters for maximum quantity of biosorption dye were achieved after 2 h of treatment in a batch system using an initial dye concentration of 20 mg/L, a mass of 1 g of L. cylindrica fibers, and pH 2. In these conditions, the quantity of dye retained is 2 mg/g and the retention rate is 78 %. Finally, a mathematical modeling of kinetics and isotherms has been used for mathematical modeling; the model of pseudo-second order is more appropriate to describe this phenomenon of biosorption. Concerning biosorption isotherms, the Freundlich model is the most appropriate for a biosorption of alpacide blue dye by L. cylindrica fibers.

Adsorption of dimethyl trisulfide from aqueous solution on a low-cost adsorbent: thermally activated pinecone

NASA Astrophysics Data System (ADS)

Shang, Jingge; He, Wei; Fan, Chengxin

2015-01-01

Thermally activated pinecone (TAP) was used for the adsorption of dimethyl trisulfide (DMTS) from aqueous solutions, which was proved to be the main odorous in algae-caused black bloom. The effects of adsorbent dosage, adsorbate concentration and contact time on DMTS biosorption were studied. The TAP produced at 600°C exhibited a relatively high surface area (519.69 m2/g) and excellent adsorption capacity. The results show that the adsorption of DMTS was initially fast and that the equilibrium time was 6 h. Higher initial DMTS concentrations led to lower removal percentages but higher adsorption capacity. The removal percentage of DMTS increased and the adsorption capacity of TAP decreased with an increase in adsorbent dosage. The adsorption process conforms well to a pseudo-second-order kinetics model. The adsorption of DMTS is more appropriately described by the Freundlich isotherm ( R 2 =0.996 1) than by the Langmuir isotherm ( R 2 =0.916 9). The results demonstrate that TAP could be an attractive low-cost adsorbent for removing DMTS from water.

Amorphous Sulfadoxine: A Physical Stability and Crystallization Kinetics Study.

PubMed

Aucamp, Marique; Milne, Marnus; Liebenberg, Wilna

2016-10-01

Poor aqueous solubility of drugs and the improvement thereof has always been a challenge for the pharmaceutical industry. With this, one of the focuses of the pharmaceutical research scientist involves investigating possible metastable forms of a given drug to be incorporated into solid dosage forms. The rationale being, the improved solubility offered by the metastable solid-state forms of drugs. Solubility remains a major challenge for formulation scientists, especially with antimicrobial agents where the emergence of resistance is directly dependent on the concentration and duration of the parasite exposed to the drug. Sulfadoxine-pyrimethamine combination therapies are still the recommended treatments for uncomplicated Plasmodium falciparum malaria. The aim of this study was to prepare an amorphous form of sulfadoxine and to investigate the stability and recrystallization behavior thereof. The amorphous form was prepared by the well-known quench cooling of the melt. The physico-chemical properties and stability of amorphous sulfadoxine were studied using hot-stage microscopy (HSM), scanning electron microscopy (SEM), x-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), as well as microcalorimetry. The recrystallization kinetics were studied isothermally by applying the Johnson-Mehl-Avrami model and non-isothermally by applying the Kissinger model. The physical stabilization of the amorphous form was investigated using physical mixtures of amorphous sulfadoxine with polyvinylpyrrolidone-25 (PVP-25). It was proved that sulfadoxine is a good glass former with relative high physical stability; however, water acts as a strong plasticizer for amorphous sulfadoxine, detrimentally affecting the stability during exposure to high moisture conditions.

Off-Gas Adsorption Model Capabilities and Recommendations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyon, Kevin L.; Welty, Amy K.; Law, Jack

2016-03-01

Off-gas treatment is required to reduce emissions from aqueous fuel reprocessing. Evaluating the products of innovative gas adsorption research requires increased computational simulation capability to more effectively transition from fundamental research to operational design. Early modeling efforts produced the Off-Gas SeParation and REcoverY (OSPREY) model that, while efficient in terms of computation time, was of limited value for complex systems. However, the computational and programming lessons learned in development of the initial model were used to develop Discontinuous Galerkin OSPREY (DGOSPREY), a more effective model. Initial comparisons between OSPREY and DGOSPREY show that, while OSPREY does reasonably well to capturemore » the initial breakthrough time, it displays far too much numerical dispersion to accurately capture the real shape of the breakthrough curves. DGOSPREY is a much better tool as it utilizes a more stable set of numerical methods. In addition, DGOSPREY has shown the capability to capture complex, multispecies adsorption behavior, while OSPREY currently only works for a single adsorbing species. This capability makes DGOSPREY ultimately a more practical tool for real world simulations involving many different gas species. While DGOSPREY has initially performed very well, there is still need for improvement. The current state of DGOSPREY does not include any micro-scale adsorption kinetics and therefore assumes instantaneous adsorption. This is a major source of error in predicting water vapor breakthrough because the kinetics of that adsorption mechanism is particularly slow. However, this deficiency can be remedied by building kinetic kernels into DGOSPREY. Another source of error in DGOSPREY stems from data gaps in single species, such as Kr and Xe, isotherms. Since isotherm data for each gas is currently available at a single temperature, the model is unable to predict adsorption at temperatures outside of the set of data currently available. Thus, in order to improve the predictive capabilities of the model, there is a need for more single-species adsorption isotherms at different temperatures, in addition to extending the model to include adsorption kinetics. This report provides background information about the modeling process and a path forward for further model improvement in terms of accuracy and user interface.« less

Toehold-mediated strand displacement reaction triggered isothermal DNA amplification for highly sensitive and selective fluorescent detection of single-base mutation.

PubMed

Zhu, Jing; Ding, Yongshun; Liu, Xingti; Wang, Lei; Jiang, Wei

2014-09-15

Highly sensitive and selective detection strategy for single-base mutations is essential for risk assessment of malignancy and disease prognosis. In this work, a fluorescent detection method for single-base mutation was proposed based on high selectivity of toehold-mediated strand displacement reaction (TSDR) and powerful signal amplification capability of isothermal DNA amplification. A discrimination probe was specially designed with a stem-loop structure and an overhanging toehold domain. Hybridization between the toehold domain and the perfect matched target initiated the TSDR along with the unfolding of the discrimination probe. Subsequently, the target sequence acted as a primer to initiate the polymerization and nicking reactions, which released a great abundant of short sequences. Finally, the released strands were annealed with the reporter probe, launching another polymerization and nicking reaction to produce lots of G-quadruplex DNA, which could bind the N-methyl mesoporphyrin IX to yield an enhanced fluorescence response. However, when there was even a single base mismatch in the target DNA, the TSDR was suppressed and so subsequent isothermal DNA amplification and fluorescence response process could not occur. The proposed approach has been successfully implemented for the identification of the single-base mutant sequences in the human KRAS gene with a detection limit of 1.8 pM. Furthermore, a recovery of 90% was obtained when detecting the target sequence in spiked HeLa cells lysate, demonstrating the feasibility of this detection strategy for single-base mutations in biological samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancing oil removal from water by immobilizing multi-wall carbon nanotubes on the surface of polyurethane foam.

PubMed

Keshavarz, Alireza; Zilouei, Hamid; Abdolmaleki, Amir; Asadinezhad, Ahmad

2015-07-01

A surface modification method was carried out to enhance the light crude oil sorption capacity of polyurethane foam (PUF) through immobilization of multi-walled carbon nanotube (MWCNT) on the foam surface at various concentrations. The developed sorbent was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and tensile elongation test. The results obtained from thermogravimetric and tensile elongation tests showed the improvement of thermal and mechanical resistance of surface-modified foam. The experimental data also revealed that the immobilization of MWCNT on PUF surface enhanced the sorption capacity of light crude oil and reduced water sorption. The highest oil removal capacity was obtained for 1 wt% MWCNT on PUF surface which was 21.44% enhancement in light crude oil sorption compared to the blank PUF. The reusability of surface modified PUF was determined through four cycles of chemical regeneration using petroleum ether. The adsorption of light crude oil with 30 g initial mass showed that 85.45% of the initial oil sorption capacity of this modified sorbent was remained after four regeneration cycles. Equilibrium isotherms for adsorption of oil were analyzed by the Freundlich, Langmuir, Temkin, and Redlich-Peterson models through linear and non-linear regression methods. Results of equilibrium revealed that Langmuir isotherm is the best fitting model and non-linear method is a more accurate way to predict the parameters involved in the isotherms. The overall findings suggested the promising potentials of the developed sorbent in order to be efficiently used in large-scale oil spill cleanup. Copyright © 2015 Elsevier Ltd. All rights reserved.

Radial cracks around α-quartz inclusions in almandine: Constraints on the metamorphic history of the Oman mountains

NASA Astrophysics Data System (ADS)

Wendt, Anke S.; D'Arco, Philippe; Goffé, Bruno; Oberhänsli, Roland

1993-02-01

Radiating tensional cracks around α-quartz inclusions in almandine have been observed in metapelite samples from the southeastern Saih Hatat tectonic window, northeastern Oman Mountains. These almandines show an inclusion-rich (glaucophane + epidote) and strongly deformed core with inclusions of different mineral phases. The rim of the same almandines is inclusion-poor and shows only quartz, apatite, zircon, rutile and Ba sbnd Al phosphates as inclusions. Quartz and apatite inclusions in the rim are single crystals often surrounded by radial cracks. These radial cracks developed during uplift by the dilation of α-quartz (4-5 vol%) without a phase transformation. Subsequently, these cracks were filled with kaolinite, phengite (Si content 3.4 per formula unit, p.f.u.), chlorite and Fe oxides. We calculated the appearance of radial cracks without phase transformation using the mathematical procedure of Van der Molen and Van Roermund [1]. This calculation involves terms for thermal expansion, isothermal compressibility and shear modulus for the example of α-quartz and almandine for the same P and T interval during a retrograde path. Published geothermobarometric estimates give pressures of between 1.0 and 2.0 GPa and temperatures of between 450 and 600°C for the peak conditions for these rocks of the Saih Hatat tectonic window. On the basis of these P-T data we calculated different retrograde P-T paths in the α-quartz domain. Initiation of garnet fracturing is dependent on the P-T starting conditions and the component of isothermal compression of the retrograde path. The calculations yield a set of smooth monotonic curves whose exact position on the P-T plane between 0.1 and 0.6 GPa and 40 and 500°C depends on the initial P-T conditions and the component of isothermal compressibility of the retrograde P-T paths. This model can be used in general terms to estimate pressure and temperature for the following cases: (1) If independent evidence (such as petrological data) allow the determination of the final pressure at which radial cracks appeared, the initial inclusion pressure can be recalculated. (2) If the initial inclusion pressure is known (e.g. from petrological data), the conditions of radial cracking can be calculated, and the pair initial pressure-final pressure leads to an estimate of the shape of the retrograde P-T path as a function of its component of isothermal decompression. In the example from the northeastern Saih Hatat tectonic window the late syntectonic growth of albite + phengite + kaolinite suggests that the final pressure for fracturing ranged between 0.4 GPa and 0.5 GPa at temperatures of 300°C. These values correspond to high initial pressures of at least 2.0 GPa at a temperature of 550°C. The following geodynamic model is suggested: A regionally extended metamorphism led to the growth of inclusion-rich garnets in the rocks from the northeastern Saih Hatat tectonic window at depths of about 30 km ( < 0.1 GPa, about 450°C). Continuing prograde metamorphism at a depth of more than 60 km with P < 2.0 GPa and T ≈ 550°C affected a metapelite unit that is only exposed immediately south of As Sifah village. In this area, clear rims of almandine grew around the older garnets and entrapped mainly quartz and apatite. During uplift along a retrograde P-T path with a large component of isothermal decompression radial cracks around α-quartz inclusions developed in the rims of almandines at a depth of about 12 km (0.4-0.5 GPa, ⩾ 300°C).

Conditions for Optimal Growth of Black Hole Seeds

NASA Astrophysics Data System (ADS)

Pacucci, Fabio; Natarajan, Priyamvada; Volonteri, Marta; Cappelluti, Nico; Urry, C. Megan

2017-12-01

Supermassive black holes weighing up to ˜109 M ⊙ are in place by z ˜ 7, when the age of the universe is ≲1 Gyr. This implies a time crunch for their growth, since such high masses cannot be easily reached in standard accretion scenarios. Here, we explore the physical conditions that would lead to optimal growth wherein stable super-Eddington accretion would be permitted. Our analysis suggests that the preponderance of optimal conditions depends on two key parameters: the black hole mass and the host galaxy central gas density. In the high-efficiency region of this parameter space, a continuous stream of gas can accrete onto the black hole from large to small spatial scales, assuming a global isothermal profile for the host galaxy. Using analytical initial mass functions for black hole seeds, we find an enhanced probability of high-efficiency growth for seeds with initial masses ≳104 M ⊙. Our picture suggests that a large population of high-z lower-mass black holes that formed in the low-efficiency region, with low duty cycles and accretion rates, might remain undetectable as quasars, since we predict their bolometric luminosities to be ≲1041 erg s-1. The presence of these sources might be revealed only via gravitational wave detections of their mergers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gehin, Jess C; Godfrey, Andrew T; Evans, Thomas M

The Consortium for Advanced Simulation of Light Water Reactors (CASL) is developing a collection of methods and software products known as VERA, the Virtual Environment for Reactor Applications, including a core simulation capability called VERA-CS. A key milestone for this endeavor is to validate VERA against measurements from operating nuclear power reactors. The first step in validation against plant data is to determine the ability of VERA to accurately simulate the initial startup physics tests for Watts Bar Nuclear Power Station, Unit 1 (WBN1) cycle 1. VERA-CS calculations were performed with the Insilico code developed at ORNL using cross sectionmore » processing from the SCALE system and the transport capabilities within the Denovo transport code using the SPN method. The calculations were performed with ENDF/B-VII.0 cross sections in 252 groups (collapsed to 23 groups for the 3D transport solution). The key results of the comparison of calculations with measurements include initial criticality, control rod worth critical configurations, control rod worth, differential boron worth, and isothermal temperature reactivity coefficient (ITC). The VERA results for these parameters show good agreement with measurements, with the exception of the ITC, which requires additional investigation. Results are also compared to those obtained with Monte Carlo methods and a current industry core simulator.« less

Removal of mercury from its aqueous solution using charcoal-immobilized papain (CIP).

PubMed

Dutta, Susmita; Bhattacharyya, Aparupa; De, Parameswar; Ray, Parthasarathi; Basu, Srabanti

2009-12-30

In the present work mercury has been eradicated from its aqueous solution using papain, immobilized on activated charcoal by physical adsorption method. Operating parameters for adsorption of papain on activated charcoal like pH, amount of activated charcoal, initial concentration of papain in solution have been varied in a suitable manner for standardization of operating conditions for obtaining the best immobilized papain sample based on their specific enzymatic activity. The immobilized papain sample obtained at initial papain concentration 40.0 g/L, activated charcoal amount 0.5 g and pH 7 shows the best specific enzymatic activity. This sample has been designated as charcoal-immobilized papain (CIP) and used for further studies of mercury removal. Adsorption equilibrium data fit most satisfactorily with the Langmuir isotherm model for adsorption of papain on activated charcoal. Physicochemical characterization of CIP has been done. The removal of mercury from its simulated solution of mercuric chloride using CIP has been studied in a lab-scale batch contactor. The operating parameters viz., the initial concentration of mercury in solution, amount of CIP and pH have been varied in a prescribed manner. Maximum removal achieved in the batch study was about 99.4% at pH 7, when initial metal concentration and weight of CIP were 20.0mg/L and 0.03 g respectively. Finally, the study of desorption of mercury has been performed at different pH values for assessment of recovery process of mercury. The results thus obtained have been found to be satisfactory.

M[superscript 2+]•EDTA Binding Affinities: A Modern Experiment in Thermodynamics for the Physical Chemistry Laboratory

ERIC Educational Resources Information Center

O'Brien, Leah C.; Root, Hannah B.; Wei, Chin-Chuan; Jensen, Drake; Shabestary, Nahid; De Meo, Cristina; Eder, Douglas J.

2015-01-01

Isothermal titration calorimetry was used to experimentally determine thermodynamic values for the ethylenediaminetetraacetic acid (EDTA)(aq) + M[superscript 2+](aq) reactions (M[superscript 2+] = Ca[superscript 2+] and Mg[superscript 2+]). Students showed that for reactions in a N-(2-hydroxyethyl)piperazine-N"-ethanesulfonic acid (HEPES)…

A Graphical Representation for the Fugacity of a Pure Substance

ERIC Educational Resources Information Center

Book, Neil L.; Sitton, Oliver C.

2010-01-01

The thermodynamic equations used to define and compute the fugacity of a pure substance are depicted as processes on a semi-logarithmic plot of pressure vs. molar Gibbs energy (PG diagram) with isotherms for the substance behaving as an ideal gas superimposed. The PG diagram clearly demonstrates the physical basis for the definitions and the…

Equilibrium and kinetic modelling of cadmium (II) biosorption by Dried Biomass Aphanothece sp. from aqueous phase

NASA Astrophysics Data System (ADS)

Awalina; Harimawan, A.; Haryani, G. S.; Setiadi, T.

2017-05-01

The Biosorption of cadmium (II) ions on dried biomass of Aphanothece sp.which previously grown in a photobioreactor system with atmospheric carbon dioxide fed input, was studied in a batch system with respect to initial pH, biomass concentration, contact time, and temperature. The biomass exhibited the highest cadmium (II) uptake capacity at 30ºC, initial pH of 8.0±0.2 in 60 minute and initial cadmium (II) ion concentration of 7.76 mg/L. Maximum biosorption capacities were 16.47 mg/g, 54.95 mg/g and 119.05 mg/g at range of initial cadmium (II) 0.96-3.63 mg/L, 1.99-8.10 mg/L and 6.48-54.38 mg/L, respectively. Uptake kinetics follows the pseudo-second order model while equilibrium is best described by Langmuir isotherm model. Isotherms have been used to determine thermodynamic parameter process (free energy change, enthalpy change and entropy change). FTIR analysis of microalgae biomass revealed the presence of amino acids, carboxyl, hydroxyl, sulfhydryl and carbonyl groups, which are responsible for biosorption of metal ions. During repeated sorption/desorption cycles, the ratio of Cd (II) desorption to biosorption decreased from 81% (at first cycle) to only 27% (at the third cycle). Nevertheless, due to its higher biosorption capability than other adsorbent, Aphanothece sp appears to be a good biosorbent for removing metal Cd (II) ions from aqueous phase.

Production of granular activated carbon from waste Rosa canina sp. seeds and its adsorption characteristics for dye.

PubMed

Gürses, A; Doğar, C; Karaca, S; Açikyildiz, M; Bayrak, R

2006-04-17

An activated carbon was developed from Rosa canina sp. seeds, characterized and used for the removal of methylene blue (basic dye) from aqueous solutions. Adsorption studies were carried out at 20 degrees C and various initial dye concentrations (20, 40, 60, 80, and 100 mg/L) for different times (15, 30, 60, and 120 min). The adsorption isotherm was obtained from data. The results indicate that the adsorption isotherm of methylene blue is typically S-shaped. The shape of isotherm is believed to reflect three distinct modes of adsorption. In region 1, the adsorption of methylene blue is carried out mainly by ion exchange. In region 2 by polarizations of pi-electrons established at cyclic parts of the previously adsorbed methylene blue molecules is occurred. However, it is not observed any change at the sign of the surface charge although zeta potential value is decreased with increase of amount adsorbed. In region 3, the slope of the isotherm is reduced, because adsorption now must overcome electrostatic repulsion between oncoming ions and the similarly charged solid. Adsorption in this fashion is usually complete when the surface is covered with a monolayer of methylene blue. To reveal the adsorptive characteristics of the produced active carbon, porosity and BET surface area measurements were made. Structural analysis was performed using SEM-EDS. The produced active carbon has the specific surface area of 799.2 m2 g-1 and the iodine number of 495 mg/g.

Modeling of the non-isothermal crystallization kinetics of polyamide 6 composites during thermoforming

NASA Astrophysics Data System (ADS)

Kugele, Daniel; Dörr, Dominik; Wittemann, Florian; Hangs, Benjamin; Rausch, Julius; Kärger, Luise; Henning, Frank

2017-10-01

The combination of thermoforming processes of continuous-fiber reinforced thermoplastics and injection molding offers a high potential for cost-effective use in automobile mass production. During manufacturing, the thermoplastic laminates are initially heated up to a temperature above the melting point. This is followed by continuous cooling of the material during the forming process, which leads to crystallization under non-isothermal conditions. To account for phase change effects in thermoforming simulation, an accurate modeling of the crystallization kinetics is required. In this context, it is important to consider the wide range of cooling rates, which are observed during processing. Consequently, this paper deals with the experimental investigation of the crystallization at cooling rates varying from 0.16 K/s to 100 K/s using standard differential scanning calorimetry (DSC) and fast scanning calorimetry (Flash DSC). Two different modeling approaches (Nakamura model, modified Nakamura-Ziabicki model) for predicting crystallization kinetics are parameterized according to DSC measurements. It turns out that only the modified Nakamura-Ziabicki model is capable of predicting crystallization kinetics for all investigated cooling rates. Finally, the modified Nakamura-Ziabicki model is validated by cooling experiments using PA6-CF laminates with embedded temperature sensors. It is shown that the modified Nakamura-Ziabicki model predicts crystallization at non-isothermal conditions and varying cooling rates with a good accuracy. Thus, the study contributes to a deeper understanding of the non-isothermal crystallization and presents an overall method for modeling crystallization under process conditions.

Application of zeolite-activated carbon macrocomposite for the adsorption of Acid Orange 7: isotherm, kinetic and thermodynamic studies.

PubMed

Lim, Chi Kim; Bay, Hui Han; Neoh, Chin Hong; Aris, Azmi; Abdul Majid, Zaiton; Ibrahim, Zaharah

2013-10-01

In this study, the adsorption behavior of azo dye Acid Orange 7 (AO7) from aqueous solution onto macrocomposite (MC) was investigated under various experimental conditions. The adsorbent, MC, which consists of a mixture of zeolite and activated carbon, was found to be effective in removing AO7. The MC were characterized by scanning electron microscopy (SEM), energy dispersive X-ray, point of zero charge, and Brunauer-Emmett-Teller surface area analysis. A series of experiments were performed via batch adsorption technique to examine the effect of the process variables, namely, contact time, initial dye concentration, and solution pH. The dye equilibrium adsorption was investigated, and the equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model. For the kinetic study, pseudo-first-order, pseudo-second-order, and intraparticle diffusion model were used to fit the experimental data. The adsorption kinetic was found to be well described by the pseudo-second-order model. Thermodynamic analysis indicated that the adsorption process is a spontaneous and endothermic process. The SEM, Fourier transform infrared spectroscopy, ultraviolet-visible spectral and high performance liquid chromatography analysis were carried out before and after the adsorption process. For the phytotoxicity test, treated AO7 was found to be less toxic. Thus, the study indicated that MC has good potential use as an adsorbent for the removal of azo dye from aqueous solution.

Applications of isothermal titration calorimetry - the research and technical developments from 2011 to 2015.

PubMed

Falconer, Robert J

2016-10-01

Isothermal titration calorimetry is a widely used biophysical technique for studying the formation or dissociation of molecular complexes. Over the last 5 years, much work has been published on the interpretation of isothermal titration calorimetry (ITC) data for single binding and multiple binding sites. As over 80% of ITC papers are on macromolecules of biological origin, this interpretation is challenging. Some researchers have attempted to link the thermodynamics constants to events at the molecular level. This review highlights work carried out using binding sites characterized using x-ray crystallography techniques that allow speculation about individual bond formation and the displacement of individual water molecules during ligand binding and link these events to the thermodynamic constants for binding. The review also considers research conducted with synthetic binding partners where specific binding events like anion-π and π-π interactions were studied. The revival of assays that enable both thermodynamic and kinetic information to be collected from ITC data is highlighted. Lastly, published criticism of ITC research from a physical chemistry perspective is appraised and practical advice provided for researchers unfamiliar with thermodynamics and its interpretation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Prediction of optimum sorption isotherm: comparison of linear and non-linear method.

PubMed

Kumar, K Vasanth; Sivanesan, S

2005-11-11

Equilibrium parameters for Bismarck brown onto rice husk were estimated by linear least square and a trial and error non-linear method using Freundlich, Langmuir and Redlich-Peterson isotherms. A comparison between linear and non-linear method of estimating the isotherm parameters was reported. The best fitting isotherm was Langmuir isotherm and Redlich-Peterson isotherm equation. The results show that non-linear method could be a better way to obtain the parameters. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity.

Generalized gas-solid adsorption modeling: Single-component equilibria

DOE PAGES

Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; ...

2015-01-07

Over the last several decades, modeling of gas–solid adsorption at equilibrium has generally been accomplished through the use of isotherms such as the Freundlich, Langmuir, Tóth, and other similar models. While these models are relatively easy to adapt for describing experimental data, their simplicity limits their generality to be used with many different sets of data. This limitation forces engineers and scientists to test each different model in order to evaluate which one can best describe their data. Additionally, the parameters of these models all have a different physical interpretation, which may have an effect on how they can bemore » further extended into kinetic, thermodynamic, and/or mass transfer models for engineering applications. Therefore, it is paramount to adopt not only a more general isotherm model, but also a concise methodology to reliably optimize for and obtain the parameters of that model. A model of particular interest is the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm. The GSTA isotherm has enormous flexibility, which could potentially be used to describe a variety of different adsorption systems, but utilizing this model can be fairly difficult due to that flexibility. To circumvent this complication, a comprehensive methodology and computer code has been developed that can perform a full equilibrium analysis of adsorption data for any gas-solid system using the GSTA model. The code has been developed in C/C++ and utilizes a Levenberg–Marquardt’s algorithm to handle the non-linear optimization of the model parameters. Since the GSTA model has an adjustable number of parameters, the code iteratively goes through all number of plausible parameters for each data set and then returns the best solution based on a set of scrutiny criteria. Data sets at different temperatures are analyzed serially and then linear correlations with temperature are made for the parameters of the model. The end result is a full set of optimal GSTA parameters, both dimensional and non-dimensional, as well as the corresponding thermodynamic parameters necessary to predict the behavior of the system at temperatures for which data were not available. It will be shown that this code, utilizing the GSTA model, was able to describe a wide variety of gas-solid adsorption systems at equilibrium.In addition, a physical interpretation of these results will be provided, as well as an alternate derivation of the GSTA model, which intends to reaffirm the physical meaning.« less

Effect of lag time distribution on the lag phase of bacterial growth - a Monte Carlo analysis

USDA-ARS?s Scientific Manuscript database

The objective of this study is to use Monte Carlo simulation to evaluate the effect of lag time distribution of individual bacterial cells incubated under isothermal conditions on the development of lag phase. The growth of bacterial cells of the same initial concentration and mean lag phase durati...

The influence of clay surface modification with berberine on the sorption of anthocyanins

NASA Astrophysics Data System (ADS)

Chulkov, A. N.; Deineka, V. I.; Tikhova, A. A.; Vesentzev, A. I.; Deineka, L. A.

2012-03-01

The influence of preliminary sorption of berberine on the sorption of anthocyanins by bentonite clay was studied. The cation exchange sorption mechanism was found to be replaced by hydrophobic sorption of these compounds after clay modification with berberine. The enthalpy of sorption along the initial isotherm part changed from endothermic to exothermic.

Mechanistic Prediction of the Effect of Microstructural Coarsening on Creep Response of SnAgCu Solder Joints

NASA Astrophysics Data System (ADS)

Mukherjee, S.; Chauhan, P.; Osterman, M.; Dasgupta, A.; Pecht, M.

2016-07-01

Mechanistic microstructural models have been developed to capture the effect of isothermal aging on time dependent viscoplastic response of Sn3.0Ag0.5Cu (SAC305) solders. SnAgCu (SAC) solders undergo continuous microstructural coarsening during both storage and service because of their high homologous temperature. The microstructures of these low melting point alloys continuously evolve during service. This results in evolution of creep properties of the joint over time, thereby influencing the long term reliability of microelectronic packages. It is well documented that isothermal aging degrades the creep resistance of SAC solder. SAC305 alloy is aged for (24-1000) h at (25-100)°C (~0.6-0.8 × T melt). Cross-sectioning and image processing techniques were used to periodically quantify the effect of isothermal aging on phase coarsening and evolution. The parameters monitored during isothermal aging include size, area fraction, and inter-particle spacing of nanoscale Ag3Sn intermetallic compounds (IMCs) and the volume fraction of micronscale Cu6Sn5 IMCs, as well as the area fraction of pure tin dendrites. Effects of microstructural evolution on secondary creep constitutive response of SAC305 solder joints were then modeled using a mechanistic multiscale creep model. The mechanistic phenomena modeled include: (1) dispersion strengthening by coarsened nanoscale Ag3Sn IMCs in the eutectic phase; and (2) load sharing between pro-eutectic Sn dendrites and the surrounding coarsened eutectic Sn-Ag phase and microscale Cu6Sn5 IMCs. The coarse-grained polycrystalline Sn microstructure in SAC305 solder was not captured in the above model because isothermal aging does not cause any significant change in the initial grain size and orientation of SAC305 solder joints. The above mechanistic model can successfully capture the drop in creep resistance due to the influence of isothermal aging on SAC305 single crystals. Contribution of grain boundary sliding to the creep strain of coarse grained joints has not been modeled in this study.

How soil organic matter composition controls hexachlorobenzene-soil-interactions: adsorption isotherms and quantum chemical modeling.

PubMed

Ahmed, Ashour A; Kühn, Oliver; Aziz, Saadullah G; Hilal, Rifaat H; Leinweber, Peter

2014-04-01

Hazardous persistent organic pollutants (POPs) interact in soil with the soil organic matter (SOM) but this interaction is insufficiently understood at the molecular level. We investigated the adsorption of hexachlorobenzene (HCB) on soil samples with systematically modified SOM. These samples included the original soil, the soil modified by adding a hot water extract (HWE) fraction (soil+3 HWE and soil+6 HWE), and the pyrolyzed soil. The SOM contents increased in the order pyrolyzed soil

Laboratory investigations of the physics of steam flow in a porous medium

USGS Publications Warehouse

Herkelrath, W.N.; Moench, A.F.

1982-01-01

Experiments were carried out in the laboratory to test a theory of transient flow of pure steam in a uniform porous medium. This theory is used extensively in modeling pressure-transient behavior in vapor-dominated geothermal systems. Transient, superheated steam-flow experiments were run by bringing a cylinder of porous material to a uniform initial pressure, and then making a step increase in pressure at one end of the sample, while monitoring the pressure-transient breakthrough at the other end. It was found in experiments run at 100?, 125?, and 146?C that the time required for steam-pressure transients to propagate through an unconsolidated material containing sand, silt, and clay was 10 to 25 times longer than predicted by theory. It is hypothesized that the delay in the steam-pressure transient was caused by adsorption of steam in the porous sample. In order to account for steam adsorption, a sink term was included in the conservation of mass equation. In addition, energy transfer in the system has to be considered because latent heat is released when steam adsorption occurs, increasing the sample temperature by as much as 10?C. Finally, it was recognized that the steam pressure was a function of both the temperature and the amount of adsorption in the sample. For simplicity, this function was assumed to be in equilibrium adsorption isotherm, which was determined by experiment. By solving the modified mass and energy equations numerically, subject to the empirical adsorption isotherm relationship, excellent theoretical simulation of the experiments was achieved. The experiments support the hypothesis that adsorption of steam can strongly influence steam pressure-transient behavior in porous media; the results suggest that the modified steam-flow theory, which includes steam adsorption terms, should be used in modeling steam flow in vapor-dominated geothermal systems.

Numerical Simulations of the Thermodynamic Process of Granite Formation on the Geological model of In-situ Melting

NASA Astrophysics Data System (ADS)

Chen, Z.; Wang, Y. J.; Chen, G. N.; Liu, J.; Liu, Y. J.

2017-12-01

The In-situ Melting model of granite reveals that granitic magma generated by anatexis is layer-like and magma convection results in thickening of the layer. On the basis and by integrating the research findings on rheological transitions of rocks in crustal melting, we simulated the thermodynamic process of granite formation by using Underworld1.7. The size of the numerical model is 100km×25km with free-slip boundary. The solidus temperature is postulated being 600° and the fusing-off temperatures is 705° that corresponds to the solid-liquid transition (SLT) of the partial melting system with the melt fraction percentage around 40%. The viscosities of rock and magma are separately calculated according to this melt percentage. The model runs on Tian-He2 supercomputer and the result indicates: 1) when temperature exceeds the solidus of rock, anatexis appears in the area below the 600° isotherm; 2) when temperature surpasses the fusing-off temperature of rock, a magma layer occurs in the area below 705° isotherm; 3) the initiation of magma convection accompanied with stoping is at the temperature around 739.6°, and the upper surface of magma layer, i.e. the MI (magma interface)/SLT (solid-liquid transition) moves upwards with time; 4) the velocity of the upward motion of MI/SLT depends on the bottom temperature and the thickness of magma layer depends on the duration of convection. Summing up, this modeling result demonstrates that the In-situ Melting model of granite meets the basic principle of physics and reveals details on the thermodynamic circumstances interacting with the development of melting and granite formation.Acknowledgement: This research is financially supported by NSFC (No 41372223, No 41230206 and No 41574087).

Fabrication and investigation of MnFe2O4/MWCNTs nanocomposite by hydrothermal technique and adsorption of cationic and anionic dyes

NASA Astrophysics Data System (ADS)

Kafshgari, Leila Asadi; Ghorbani, Mohsen; Azizi, Asghar

2017-10-01

In present study, MnFe2O4/MWCNT nanocomposite synthesized using the hydrothermal technique and has been used for removal of DR16 and Y40 dyes from aqueous solutions. The characteristics results of FTIR, XRD, FESEM and TEM indicated that the nanoadsorbent was successfully fabricated. Magnetic sensitivity results demonstrated that the nanoparticles with saturation magnetization (Ms) value of 8.93 emu g-1 would have a fast magnetic response. The performance of adsorption was investigated in a batch reactor employing parameters expected to affect the maximum adsorption capacity (qm) such as pH, contact time, initial dye concentration and temperature. The highest sorption capacities of DR16 and Y40 after 300 min at 328 K were found to be 607.79 mg/g and 280 mg/g at pH of 2 and 6, respectively. The adsorption behavior over the time was assessed through pseudo-first, pseudo-second and Weber-Morris intra particle diffusion models. It was found that the pseudo-second order model gave the best agreement to the experimental data. Adsorbate-adsorbent interactions as a function of temperature was evaluated by Langmuir, Freundlich, Temkin and Sips isotherm models from which Sips isotherm had the highest consistency with the experimental data. Thermodynamic parameters including ΔG°, ΔS° and ΔH° were determined over the temperature range of 298-328 K. The results revealed that the adsorption reaction of DR16 onto MnFe2O4/MWCNT was spontaneous and exothermic, whilst the sorption process of Y40 was spontaneous and endothermic. In addition, activation energy values implied that the removal process of DR16 and Y40 was physical in nature.

Physical and chemical properties and adsorption type of activated carbon prepared from plum kernels by NaOH activation.

PubMed

Tseng, Ru-Ling

2007-08-25

Activated carbon was prepared from plum kernels by NaOH activation at six different NaOH/char ratios. The physical properties including the BET surface area, the total pore volume, the micropore ratio, the pore diameter, the burn-off, and the scanning electron microscope (SEM) observation as well as the chemical properties, namely elemental analysis and temperature programmed desorption (TPD), were measured. The results revealed a two-stage activation process: stage 1 activated carbons were obtained at NaOH/char ratios of 0-1, surface pyrolysis being the main reaction; stage 2 activated carbons were obtained at NaOH/char ratios of 2-4, etching and swelling being the main reactions. The physical properties of stage 2 activated carbons were similar, and specific area was from 1478 to 1887m(2)g(-1). The results of reaction mechanism of NaOH activation revealed that it was apparently because of the loss ratio of elements C, H, and O in the activated carbon, and the variations in the surface functional groups and the physical properties. The adsorption of the above activated carbons on phenol and three kinds of dyes (MB, BB1, and AB74) were used for an isotherm equilibrium adsorption study. The data fitted the Langmuir isotherm equation. Various kinds of adsorbents showed different adsorption types; separation factor (R(L)) was used to determine the level of favorability of the adsorption type. In this work, activated carbons prepared by NaOH activation were evaluated in terms of their physical properties, chemical properties, and adsorption type; and activated carbon PKN2 was found to have most application potential.

Selective adsorption of Pb(II), Cd(II), and Ni(II) ions from aqueous solution using chitosan-MAA nanoparticles.

PubMed

Heidari, Aghdas; Younesi, Habibollah; Mehraban, Zahra; Heikkinen, Harri

2013-10-01

Chitosan-MAA nanoparticles (CS-MAA) with an average size of 10-70 nm were prepared by polymerizing chitosan with methacrylic acid in aqueous solution. The physicochemical properties of nanoparticles were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). The adsorption of Pb(II), Cd(II) and Ni(II) from aqueous solution on CS-MAA was studied in a batch system. The effects of the solution pH, initial metal concentration, contact time, and dosage of the adsorbent on the adsorption process were examined. The experimental data were analyzed using the pseudo-second-order kinetic equations and the Langmuir, Freundlich and Redlish-Peterson isotherms. The maximum adsorption capacity was 11.30, 1.84, and 0.87 mg/g for Pb(II), Cd(II) and Ni(II) ions, respectively, obtained by the Langmuir isotherm. However, the adsorption isotherm was better explained by the Freundlich rather than by the Langmuir model, as the high correlation coefficients (R(2)>0.99) were obtained at a higher confidence level. Copyright © 2013 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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.

Mathematical model for the growth of phases in binary multiphase systems upon isothermic annealing

NASA Astrophysics Data System (ADS)

Molokhina, L. A.; Rogalin, V. E.; Filin, S. A.; Kaplunov, I. A.

2017-09-01

A phenomenological mathematical model of the formation and growth of phases in a binary multiphase system with allowance for factors influencing the process of diffusion in a binary system is presented. It is shown that phases can grow for a certain time at different ratios between diffusion parameters according to a parabolic law that depends on the duration of isothermic annealing. They then slow their growth after successor phases appear at their interface with one component and can completely disappear from a diffusion layer or begin to grow again, but only at a rate slower than during their initial formation. The dependence of the thickness of each phase layer in a multiphase diffusion zone on the duration of isothermic annealing and the ratio between the diffusion parameters in neighboring phases is obtained. It is established that a certain ratio between the phase growth and rates of dissolution with allowance for the coefficients of diffusion in each phase and the periods of incubation can result in the complete disappearance of one phase as early as the onset of the growth of phase nuclei and be interpreted as a process of reaction diffusion.

Effects of temperature, thermal exposure, and fatigue on an alumina/aluminum composite

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1980-01-01

An experimental investigation of the mechanical properties and microstructure of an aluminum matrix/polycrystalline alumina fiber composite material is discussed. The effects of fabrication, isothermal exposure (up to 10,000 hours at 590 K), thermal cycling (6000 cycles between 200 K and 590 K), fatigue (1,000,000 tension-tension cycles) were determined by mechanical testing and metallurgical analysis. The fabrication process severely degraded the fiber strength by reducing the alumina to a nonstoichiometric form and quenching in the resultant vacancies and stress fields. However, isothermal exposure, thermal cycling, and fatigue cycling all restored the fiber strength by enhancing vacancy annihilation. Comparison of the as-fabricated material with other aerospace materials shows that it is an attractive candidate for select applications. Long duration isothermal exposure weakened the matrix by overaging and through the diffusional loss of lithium to a surface reaction forming lithium carbonate. Thermal cycling initiated cracks in the matrix and fibers. Tension-tension fatigue cycling caused no apparent damage to the as-fabricated material but in fact, strengthened it to the rule-of-mixtures value. Fatigue cycling after thermal exposure did have a cumulative damage effect.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj. Sai V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 +/- 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj. Sai V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

NASA Technical Reports Server (NTRS)

Raj, S. V.

2008-01-01

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

Thermal relaxation behavior of residual stress in laser hardened 17-4PH steel after shot peening treatment

NASA Astrophysics Data System (ADS)

Wang, Zhou; Chen, Yanhua; Jiang, Chuanhai

2011-09-01

In order to investigate the residual stress relaxations of shot peened layer, isothermal annealing treatments were carried out on tempered and laser hardened 17-4PH steel after shot peening with different temperatures from 300 °C to 600 °C. The results showed that the residual stresses were relaxed in the whole deformation layer especially under higher temperature. The maximum rates of stress relaxation took place at the initial stage of annealing process in all conditions. The relaxation process during isothermal annealing could be described by Zener-Wert-Avrami function. The thermal stability of residual stress in tempered 17-4PH was higher than that in laser hardened 17-4PH as well as that in α-iron, which was due to the pinning effects of ɛ-Cu precipitates on the dislocation movement. As massive ɛ-Cu precipitates formed in the temperature about 480 °C, the activation enthalpies for stress relaxation in laser hardened 17-4PH were the same as that in tempered 17-4PH in the conditions of isothermal annealing temperatures of 500 °C and 600 °C.

Poly(acrylic acid) modifying bentonite with in-situ polymerization for removing lead ions.

PubMed

He, Y F; Zhang, L; Yan, D Z; Liu, S L; Wang, H; Li, H R; Wang, R M

2012-01-01

In this paper, a new kind of poly(acrylic acid) modified clay adsorbent, the poly(acrylic acid)/bentonite composite (PAA/HB) was prepared by in-situ polymerization, and utilized to remove lead(II) ions from solutions. The maximum adsorption of adsorbent is at pH 5 for metal ions, whereas the adsorption starts at pH 2. The effects of contact time (5-60 min), initial concentration of metal ions (200-1,000 mg/L) and adsorbent dosage (0.04-0.12 g/100 mL) have been reported in this article. The experimental data were investigated by means of kinetic and equilibrium adsorption isotherms. The kinetic data were analyzed by the pseudo-first-order and pseudo-second-order equation. The experimental data fitted the pseudo-second-order kinetic model very well. Langmuir and Freundlich isotherms were tried for the system to better understand the adsorption isotherm process. The maximal adsorption capacity of the lead(II) ions on the PAA/HB, as calculated from the Langmuir model, was 769.2 mg/g. The results in this study indicated that PAA/HB was an attractive candidate for removing lead(II) (99%).

BET, thermal degradation, and FTIR spectras of triazine polyamine polymers.

PubMed

Can, Mustafa

2017-04-01

Here we show effect of the polyamine polymer chain length to BET isotherms. According to IUPAC classification [1], all three polymers are fitting type 1 physical adsorption isotherm with H3 hysteresis (except for EDA having H2 hysteresis). Moreover, TG and TGA analysis of polymers triazine-ethylenediamine (EDA) and triazine-triethylenetetramine (TETA) are provided. Due to the similarities of the structure, main decomposition temperatures are close to each other (between 593 K and 873 K). In order to understand change of FTIR spectra with adsorption and stripping Au(III), fresh, Au(III) adsorbed and recycled spectras of polymers measured. For further discussions about the effect of chain length to adsorption of Au(III) onto triazine polyamine polymer particles "Au (III) Uptake by Triazine Polyamine Polymers: Mechanism, Kinetic and Equilibrium Studies" Can et al. [2] (article in press).

Characterization of melt-quenched and milled amorphous solids of gatifloxacin.

PubMed

Hattori, Yusuke; Suzuki, Ayumi; Otsuka, Makoto

2016-11-01

The objectives of this study were to characterize and investigate the differences in amorphous states of gatifloxacin. We prepared two types of gatifloxacin amorphous solids coded as M and MQ using milling and melt-quenching methods, respectively. The amorphous solids were characterized via X-ray diffraction (XRD), nonisothermal differential scanning calorimetry (DSC) and time-resolved near-infrared (NIR) spectroscopy. Both the solids displayed halo XRD patterns, the characteristic of amorphous solids; however, in the non-isothermal DSC profiles, these amorphous solids were distinguished by their crystallization and melting temperatures. The Kissinger-Akahira-Sunose plots of non-isothermal crystallization temperatures at various heating rates indicated a lower activation energy of crystallization for the amorphous solid M than that of MQ. These results support the differentiation between two amorphous states with different physical and chemical properties.

Linear Stability of Self-Similar Flow: 1. Isothermal Cylindrical Implosion and Expansion.

DTIC Science & Technology

1978-03-01

Attn: J. Tachon N. Trocheris C. Z4ercier R. B. Paris 3. Centro di Studio sui Gas lonizzati Univereita di Pe4ova 6/a Via Gre.denigo 35100 Padova, Italia...fur Plasma Physics 8046 Garching bet ?~rncben West Germany Attn: D. Biskamp K. Von Hagenow Horst Pacher chodura V. Schneider D. Pfirsch 10. Siberian

Adsorption of basic dyes on granular activated carbon and natural zeolite.

PubMed

Meshko, V; Markovska, L; Mincheva, M; Rodrigues, A E

2001-10-01

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.

Adsorption of Crystal Violet Dye Using Zeolite A Synthesized From Coal Fly Ash

NASA Astrophysics Data System (ADS)

Jumaeri; Kusumastuti, E.; Santosa, S. J.; Sutarno

2017-02-01

Adsorption of Crystal Violet (CV) dye using zeolite A synthesized from coal fly ash (ZA) has been done. Effect of pH, contact time, and the initial concentration of dye adsorption was studied in this adsorption. Model experimental of adsorption isotherms and adsorption kinetics were also studied. The adsorption is done in a batch reactor at room temperature. A total of 0.01 g of zeolite A was added to the Erlenmeyer flask 50 mL containing 20 mL of the dye solution of Crystal Violet in a variety of conditions of pH, contact time and initial concentration. Furthermore, Erlenmeyer flask and its contents were shaken using an orbital shaker at a speed of 200 rpm. After a specified period of adsorption, the solution was centrifuged for 2 minutes so that the solids separated from the solution. The concentration of the dye after adsorption determined using Genesis-20 Spectrophotometer. The results showed that the Zeolite A synthesized from coal fly ash could be used as an effective adsorbent for Crystal Violet dye. The optimum adsorption occurs at pH 6, and contact time 45 minutes. At the initial concentration of 2 to 6 mg/L, adsorption is reduced from 79 to 62.8%. Crystal Violet dye adsorption in zeolite A fulfilled kinetic model of pseudo-order 2 and model of Freundlich adsorption isotherm.

The Importance of Protons in Reactive Transport Modeling

NASA Astrophysics Data System (ADS)

McNeece, C. J.; Hesse, M. A.

2014-12-01

The importance of pH in aqueous chemistry is evident; yet, its role in reactive transport is complex. Consider a column flow experiment through silica glass beads. Take the column to be saturated and flowing with solution of a distinct pH. An instantaneous change in the influent solution pH can yield a breakthrough curve with both a rarefaction and shock component (composite wave). This behavior is unique among aqueous ions in transport and is more complex than intuition would tell. Analysis of the hyperbolic limit of this physical system can explain these first order transport phenomenon. This analysis shows that transport behavior is heavily dependent on the shape of the adsorption isotherm. Hence it is clear that accurate surface chemistry models are important in reactive transport. The proton adsorption isotherm has nonconstant concavity due to the proton's ability to partition into hydroxide. An eigenvalue analysis shows that an inflection point in the adsorption isotherm allows the development of composite waves. We use electrostatic surface complexation models to calculate realistic proton adsorption isotherms. Surface characteristics such as specific surface area, and surface site density were determined experimentally. We validate the model by comparison against silica glass bead flow through experiments. When coupled to surface complexation models, the transport equation captures the timing and behavior of breakthrough curves markedly better than with commonly used Langmuir assumptions. Furthermore, we use the adsorption isotherm to predict, a priori, the transport behavior of protons across pH composition space. Expansion of the model to multicomponent systems shows that proton adsorption can force composite waves to develop in the breakthrough curves of ions that would not otherwise exhibit such behavior. Given the abundance of reactive surfaces in nature and the nonlinearity of chemical systems, we conclude that building a greater understanding of proton adsorption is of utmost importance to reactive transport modeling.

Removal of tetracycline from aqueous solution by a Fe3O4 incorporated PAN electrospun nanofiber mat.

PubMed

Liu, Qing; Zheng, Yuming; Zhong, Lubin; Cheng, Xiaoxia

2015-02-01

Pollution of antibiotics, a type of emerging contaminant, has become an issue of concern, due to their overuse in human and veterinary application, persistence in environment and great potential risk to human and animal health even at trace level. In this work, a novel adsorbent, Fe3O4 incorporated polyacrylonitrile nanofiber mat (Fe-NFM), was successfully fabricated via electrospinning and solvothermal method, targeting to remove tetracycline (TC), a typical class of antibiotics, from aqueous solution. Field emission scanning electron microscopy and X-ray diffraction spectroscopy were used to characterize the surface morphology and crystal structure of the Fe-NFM, and demonstrated that Fe-NFM was composed of continuous, randomly distributed uniform nanofibers with surface coating of Fe3O4 nanoparticles. A series of adsorption experiments were carried out to evaluate the removal efficiency of TC by the Fe-NFM. The pseudo-second-order kinetics model fitted better with the experimental data. The highest adsorption capacity was observed at initial solution pH4 while relative high adsorption performance was obtained from initial solution pH4 to 10. The adsorption of TC on Fe-NFM was a combination effect of both electrostatic interaction and complexation between TC and Fe-NFM. Freundlich isotherm model could better describe the adsorption isotherm. The maximum adsorption capacity calculated from Langmuir isotherm model was 315.31 mg/g. Compared to conventional nanoparticle adsorbents which have difficulties in downstream separation, the novel nanofiber mat can be simply installed as a modular compartment and easily separated from the aqueous medium, promising its huge potential in drinking and wastewater treatment for micro-pollutant removal. Copyright © 2014. Published by Elsevier B.V.

Optimizing the Removal of Rhodamine B in Aqueous Solutions by Reduced Graphene Oxide-Supported Nanoscale Zerovalent Iron (nZVI/rGO) Using an Artificial Neural Network-Genetic Algorithm (ANN-GA)

PubMed Central

Shi, Xuedan; Ruan, Wenqian; Hu, Jiwei; Fan, Mingyi; Cao, Rensheng; Wei, Xionghui

2017-01-01

Rhodamine B (Rh B) is a toxic dye that is harmful to the environment, humans, and animals, and thus the discharge of Rh B wastewater has become a critical concern. In the present study, reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) was used to treat Rh B aqueous solutions. The nZVI/rGO composites were synthesized with the chemical deposition method and were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2-sorption, and X-ray photoelectron spectroscopy (XPS) analysis. The effects of several important parameters (initial pH, initial concentration, temperature, and contact time) on the removal of Rh B by nZVI/rGO were optimized by response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA). The results suggest that the ANN-GA model was more accurate than the RSM model. The predicted optimum value of Rh B removal efficiency (90.0%) was determined using the ANN-GA model, which was compatible with the experimental value (86.4%). Moreover, the Langmuir, Freundlich, and Temkin isotherm equations were applied to fit the adsorption equilibrium data, and the Freundlich isotherm was the most suitable model for describing the process for sorption of Rh B onto the nZVI/rGO composites. The maximum adsorption capacity based on the Langmuir isotherm was 87.72 mg/g. The removal process of Rh B could be completed within 20 min, which was well described by the pseudo-second order kinetic model. PMID:28587196

Optimizing the Removal of Rhodamine B in Aqueous Solutions by Reduced Graphene Oxide-Supported Nanoscale Zerovalent Iron (nZVI/rGO) Using an Artificial Neural Network-Genetic Algorithm (ANN-GA).

PubMed

Shi, Xuedan; Ruan, Wenqian; Hu, Jiwei; Fan, Mingyi; Cao, Rensheng; Wei, Xionghui

2017-06-03

Rhodamine B (Rh B) is a toxic dye that is harmful to the environment, humans, and animals, and thus the discharge of Rh B wastewater has become a critical concern. In the present study, reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) was used to treat Rh B aqueous solutions. The nZVI/rGO composites were synthesized with the chemical deposition method and were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N₂-sorption, and X-ray photoelectron spectroscopy (XPS) analysis. The effects of several important parameters (initial pH, initial concentration, temperature, and contact time) on the removal of Rh B by nZVI/rGO were optimized by response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA). The results suggest that the ANN-GA model was more accurate than the RSM model. The predicted optimum value of Rh B removal efficiency (90.0%) was determined using the ANN-GA model, which was compatible with the experimental value (86.4%). Moreover, the Langmuir, Freundlich, and Temkin isotherm equations were applied to fit the adsorption equilibrium data, and the Freundlich isotherm was the most suitable model for describing the process for sorption of Rh B onto the nZVI/rGO composites. The maximum adsorption capacity based on the Langmuir isotherm was 87.72 mg/g. The removal process of Rh B could be completed within 20 min, which was well described by the pseudo-second order kinetic model.

Humidity sorption on natural building stone

NASA Astrophysics Data System (ADS)

Franzen, C.; Mirwald, P.

2003-04-01

processes, physical, chemical or biological, depend on the presence of water. Like most porous materials building stone respond on humidity by water uptake. The sorption isotherm represents the equilibrium moisture, specific for each material. The determination of the isotherm for stone of low and small porosity like marble is difficult. With the help of a newly developed water sorption analysis chamber [2], which allows the simultaneous measurement of 11 samples, good results on stone/rock samples have been obtained. Even at marble species with pore volumes lower than 0.4 % isotherms are measured. This analytical method offers new insights in the pore behaviour of low porosity materials. The advantages of this technique which supplements other techniques (e.g. BET, Hg-porosimetry) are: i) the testing agent is identical to the weathering agent, water; ii) the atmospheric parameters at the measurement reflect the natural conditions - thus no changes to the material properties have to be considered; iii) due to the small diameter of the water molecule (~0.28 nm), smaller pores are reached than e.g. with N2 (~0.31 nm). Sorption isotherms of sandstone (Baumberg, Obernkirchen, Groeden), granite (Brixen), and marble (Sterzing, Laas) are presented. Particular as to marbles the resolution is considerably higher. A previously observed negative hysteresis [3] seems an effect due to limited data resolution. [1] Snethlage, R. (1984) Steinkonservierung, Bayer. LA Denkmalpflege, Ah. 22, 203 S. [2] Griesser, U.J., Dillenz, J. (2002) Neuartiges, vollautomatisches Feuchtesorptionsprüfgerät mit hohem Probendurchsatz, Feuchtetag 2002, Weimar, 85-93. [3] Fimmel, R. (1996) Verwitterungsverhalten der alpinen Marmore von Laas und Sterzing, Diss. Univ. Ibk, 116 S.

Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

PubMed Central

Tan, Yih Horng; Davis, Jason A.; Fujikawa, Kohki; Ganesh, N. Vijaya; Demchenko, Alexei V.

2012-01-01

Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N2 gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C18-SH (coverage of 2.94 × 1014 molecules cm−2 based from the decomposition of the C18-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the ‘C’ parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology. PMID:22822294

Removal of copper(II) ions from aqueous solutions by Azolla rongpong: batch and continuous study.

PubMed

Nedumaran, B; Velan, M

2008-01-01

Batch and packed bed continuous biosorption studies were conducted to investigate the kinetics and isotherms of Cu(II) ions on the biomass of blue green alga Azolla rongpong. It is observed that the biosorption capacity of algae depends on initial pH and dosage. The biosorption capacity increases with increasing concentration and follows Freundlich isotherm model well with k and n values 0.06223 and 0.949 respectively. The optimum pH of 3.5 with an algae dosage of 1 g/L was observed. The results indicate that with the advantage of high metal biosorption capacity and recovery of Cu(II) ions, A. rongpong can be used as an efficient and economic biosorbent for the removal and recovery of toxic heavy metals from aqueous wastes even at higher concentration.

Low-gravity fluid physics: A program overview

NASA Technical Reports Server (NTRS)

1990-01-01

An overview is presented of the microgravity fluid physics program at Lewis Research Center. One of the main reasons for conducting low gravity research in fluid physics is to study phenomena such as surface tension, interfacial contact angles, and diffusion independent of such gravitationally induced effects as buoyant convection. Fluid physics is at the heart of many space-based technologies including power systems, thermal control systems, and life support systems. Fundamental understanding of fluid physics is a key ingredient to successful space systems design. In addition to describing ground-based and space-based low-gravity facilities, selected experiments are presented which highlight Lewis work in fluid physics. These experiments can be categorized into five theme areas which summarize the work being conducted at Lewis for OSSA: (1) isothermal/iso-solutal capillary phenomena; (2) capillary phenomena with thermal/solutal gradients; (3) thermal-solutal convection; (4) first- and second-order phase transitions in a static fluid; and (5) multiphase flow.

Critical contribution of nonlinear chromatography to the understanding of retention mechanism in reversed-phase liquid chromatography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A

2005-11-01

The retention of most compounds in RPLC proceeds through a combination of several independent mechanisms. We review a series of recent studies made on the behavior of several commercial C{sub 18}-bonded stationary phases and of the complex, mixed retention mechanisms that were observed in RPLC. These studies are essentially based on the acquisition of adsorption isotherm data, on the modeling, and on the interpretation of these data. Because linear chromatography deals only with the initial slope of the global, overall, or apparent isotherm, it is unable fully to describe the complete adsorption mechanism. It cannot even afford clues as tomore » the existence of several overlaid retention mechanisms. More specifically, it cannot account for the consequences of the surface heterogeneity of the packing material. The acquisition of equilibrium data in a wide concentration range is required for this purpose. Frontal analysis (FA) of selected probes gives data that can be modeled into equilibrium isotherms of these probes and that can also be used to calculate their adsorption or affinity energy distribution (AED). The combination of these data, the detailed study of the best constants of the isotherm model, the determination of the influence of experimental parameters (e.g., buffer pH and pI, temperature) on the isotherm constants provide important clues regarding the heterogeneity of the adsorbent surface and the main properties of the adsorption mechanisms. The comparison of similar data obtained for the adsorption of neutral and ionizable compounds, treated with the same approach, and the investigation of the influence on the thermodynamics of phase equilibrium of the experimental conditions (temperature, average pressure, mobile phase composition, nature of the organic modifier, and, for ionizable compounds, of the ionic strength, the nature, the concentration of the buffer, and its pH) brings further information. This review provides original conclusions regarding retention mechanisms in RPLC.« less

Removal of hexavalent chromium by using red mud activated with cetyltrimethylammonium bromide.

PubMed

Li, Deliang; Ding, Ying; Li, Lingling; Chang, Zhixian; Rao, Zhengyong; Lu, Ling

2015-01-01

The removal of hexavalent chromium [Cr(VI)] from aqueous solution by using red mud activated with cetyltrimethylammonium bromide (CTAB) was studied. The optimum operation parameters, such as CTAB concentration, pH values, contact time, and initial Cr(VI) concentration, were investigated. The best concentration of CTAB for modifying red mud was found to be 0.50% (mCTAB/VHCl,0.6 mol/L). The lower pH (<2) was found to be much more favourable for the removal of Cr(VI). Red mud activated with CTAB can greatly improve the removal ratio of Cr(VI) as high as four times than that of original red mud. Adsorption equilibrium was reached within 30 min under the initial Cr(VI) concentration of 100 mg L(-1). The isotherm data were analysed using Langmuir and Freundlich models. The adsorption of Cr(VI) on activated red mud fitted well to the Langmuir isotherm model, and the maximum adsorption capacity was estimated as 22.20 mg g(-1) (Cr/red mud). The adsorption process could be well described using the pseudo-second-order model. The result shows that activated red mud is a promising agent for low-cost water treatment.

Efficient removal of chromate and arsenate from individual and mixed system by malachite nanoparticles.

PubMed

Saikia, Jiban; Saha, Bedabrata; Das, Gopal

2011-02-15

Malachite nanoparticles of 100-150 nm have been efficiently and for the first time used as an adsorbent for the removal of toxic arsenate and chromate. We report a high adsorption capacity for chromate and arsenate on malachite nanoparticle from both individual and mixed solution in pH ∼4-5. However, the adsorption efficiency decreases with the increase of solution pH. Batch studies revealed that initial pH, temperature, malachite nanoparticles dose and initial concentration of chromate and arsenate were important parameters for the adsorption process. Thermodynamic analysis showed that adsorption of chromate and arsenate on malachite nanoparticles is endothermic and spontaneous. The adsorption of these anions has also been investigated quantitatively with the help of adsorption kinetics, isotherm, and selectivity coefficient (K) analysis. The adsorption data for both chromate and arsenate were fitted well in Langmuir isotherm and preferentially followed the second order kinetics. The binding affinity of chromate is found to be slightly higher than arsenate in a competitive adsorption process which leads to the comparatively higher adsorption of chromate on malachite nanoparticles surface. Copyright © 2010 Elsevier B.V. All rights reserved.

Adsorption of Paraquat Dichloride by Graphitic Carbon Nitride Synthesized from Melamine Scraps

NASA Astrophysics Data System (ADS)

Watcharenwong, A.; Kaeokan, A.; Rammaroeng, R.; Upama, P.; Kajitvichyanukul, P.

2017-07-01

In this research, graphitic carbon nitride (g-C3N4) was synthesized from useless melamine scraps. Mixture of melamine powder and urea was directly burned in the muffle furnace at 550 °C. Later as-synthesized g-C3N4 was modified with hydrochloric acid. The g-C3N4 powder was characterized by several techniques including X-ray diffraction, scanning electron microscope, and specific surface area analyser. Adsorption of the herbicide paraquat from an aqueous solution to suspended particles of g-C3N4 was investigated, taking into consideration several parameters such as initial concentration of paraquat, initial pH, and dosage of g-C3N4. The results showed that with the same amount of g-C3N4, the increase in the paraquat concentration caused the reduction in the removal efficiency and the higher the amount of g-C3N4, the less residual paraquat remained in the bulk solution. G-C3N4 showed better adsorption behaviour in the basic condition. Finally, Langmuir and Freundlich adsorption isotherms were also evaluated. Paraquat adsorption by g-C3N4 was in accordance with Langmuir more than Freundlich adsorption isotherm.

Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide.

PubMed

Bedemo, Agaje; Chandravanshi, Bhagwan Singh; Zewge, Feleke

2016-01-01

Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3-10). The optimum conditions for the removal of Cr(III) were found to be at pH 4-6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent.

Comparison of 4-chloro-2-nitrophenol adsorption on single-walled and multi-walled carbon nanotubes

PubMed Central

2012-01-01

The adsorption characteristics of 4-chloro-2-nitrophenol (4C2NP) onto single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) from aqueous solution were investigated with respect to the changes in the contact time, pH of solution, carbon nanotubes dosage and initial 4C2NP concentration. Experimental results showed that the adsorption efficiency of 4C2NP by carbon nanotubes (both of SWCNTs and MWCNTs) increased with increasing the initial 4C2NP concentration. The maximum adsorption took place in the pH range of 2–6. The linear correlation coefficients of different isotherm models were obtained. Results revealed that the Langmuir isotherm fitted the experimental data better than the others and based on the Langmuir model equation, maximum adsorption capacity of 4C2NP onto SWCNTs and MWCNTs were 1.44 and 4.42 mg/g, respectively. The observed changes in the standard Gibbs free energy, standard enthalpy and standard entropy showed that the adsorption of 4C2NP onto SWCNTs and MWCNTs is spontaneous and exothermic in the temperature range of 298–328 K. PMID:23369489

How do binary separations depend on cloud initial conditions?

NASA Astrophysics Data System (ADS)

Sterzik, M. F.; Durisen, R. H.; Zinnecker, H.

2003-11-01

We explore the consequences of a star formation scenario in which the isothermal collapse of a rotating, star-forming core is followed by prompt fragmentation into a cluster containing a small number (N <~ 10) of protostars and/or substellar objects. The subsequent evolution of the cluster is assumed to be dominated by dynamical interactions among cluster members, and this establishes the final properties of the binary and multiple systems. The characteristic scale of the fragmenting core is determined by the cloud initial conditions (such as temperature, angular momentum and mass), and we are able to relate the separation distributions of the final binary population to the properties of the star-forming core. Because the fragmentation scale immediately after the isothermal collapse is typically a factor of 3-10 too large, we conjecture that fragmentation into small clusters followed by dynamical evolution is required to account for the observed binary separation distributions. Differences in the environmental properties of the cores are expected to imprint differences on the characteristic dimensions of the binary systems they form. Recent observations of hierarchical systems, differences in binary characteristics among star forming regions and systematic variations in binary properties with primary mass can be interpreted in the context of this scenario.

Separation of aflatoxin B1 from synthetic physiological fluids using talc and diatomite: Kinetic and isotherm aspects.

PubMed

Sprynskyy, Myroslav; Krzemień-Konieczka, Iwona; Gadzała-Kopciuch, Renata; Buszewski, Bogusław

2018-01-01

The objective of the study was to examine adsorption of the aflatoxin B1 from synthetic gastric fluid and synthetic intestinal fluid by talc, raw and calcined diatomite. The kinetic and equilibrium adsorption processes were studied in the batch adsorption experiments applying high performance liquid chromatography for the aflatoxin B1 determination. The kinetic study showed a very fast adsorption of the aflatoxin B1 onto the selected adsorbents from the both physiological fluids with reaching equilibrium within 1-15min. The aflatoxin B1 was almost completely adsorbed in initial linear step of the kinetic process that can be described well by the zero-order kinetics model. The experimental data of the equilibrium adsorption were characterized using the Langmuir and Freundlich isotherm models. The high adsorption effectiveness was found in a range of 90%-100% and 60%-100% for the diatomite samples and the talc respectively at the initial concentrations of the aflatoxin B1 as 31-300ng/mL. The possible mechanisms of the aflatoxin adsorption onto the used mineral adsorbents are also discussed in the work. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface functionalized composite nanofibers for efficient removal of arsenic from aqueous solutions.

PubMed

Mohamed, Alaa; Osman, T A; Toprak, M S; Muhammed, M; Uheida, A

2017-08-01

A novel composites nanofiber was synthesized based on PAN-CNT/TiO 2 -NH 2 nanofibers using electrospinning technique followed by chemical modification of TiO 2 NPs. PAN-CNT/TiO 2 -NH 2 nanofiber were characterized by XRD, FTIR, SEM, and TEM. The effects of various experimental parameters such as initial concentration, contact time, and solution pH on As removal were investigated. The maximum adsorption capacity at pH 2 for As(III) and As(V) is 251 mg/g and 249 mg/g, respectively, which is much higher than most of the reported adsorbents. The adsorption equilibrium reached within 20 and 60 min as the initial solution concentration increased from 10 to 100 mg/L, and the data fitted well using the linear and nonlinear pseudo first and second order model. Isotherm data fitted well to the linear and nonlinear Langmuir, Freundlich, and Redlich-Peterson isotherm adsorption model. Desorption results showed that the adsorption capacity can remain up to 70% after 5 times usage. This work provides a simple and an efficient method for removing arsenic from aqueous solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nickel(II) biosorption from aqueous solutions by shrimp head biomass.

PubMed

Hernández-Estévez, Alejandro; Cristiani-Urbina, Eliseo

2014-11-01

The present study evaluates the capacity of shrimp (Farfantepenaeus aztecus) head to remove toxic Ni(II) ions from aqueous solutions. Relevant parameters that could affect the biosorption process, such as shrimp head pretreatment, solution pH level, contact time and initial Ni(II) concentration, were studied in batch systems. An increase in Ni(II) biosorption capacity and a reduction in the time required to reach Ni(II) biosorption equilibrium was manifested by shrimp head biomass pretreated by boiling in 0.5 N NaOH for 15 min; this biomass was thereafter denominated APSH. The optimum biosorption level of Ni(II) ions onto APSH was observed at pH 7.0. Biosorption increased significantly with rising initial Ni(II) concentration. In terms of biosorption dynamics, the pseudo-second-order kinetic model described Ni(II) biosorption onto APSH best. The equilibrium data adequately fitted the Langmuir isotherm model within the studied Ni(II) ion concentration range. According to this isotherm model, the maximum Ni(II) biosorption capacity of APSH was 104.22 mg/g. Results indicate that APSH could be used as a low-cost, environmentally friendly, and promising biosorbent with high biosorption capacity to remove Ni(II) from aqueous solutions.

Experimental study of Pb (II) solution sorption behavior onto Coffee Husk Bioactivated Carbon

NASA Astrophysics Data System (ADS)

Fona, Z.; Habibah, U.

2018-04-01

Coffee husk which is abundantly produced in the coffee plantations is potential to be a challenging adsorbent. The fate of Pb (II) solution in the sorption mechanism onto the adsorbent has been investigated. This paper aimed to study the efficiency of Pb (II) aqueous solution removal using activated carbon from coffee husk (CAC). The sorption characteristics were using two isotherm models, Langmuir and Freundlich, were also reported. The coffee husk from local plantations in Middle Aceh was carbonized and sieved to 120/140 mesh. The charcoal was activated using hydrochloric acid before contacted with the different initial concentrations of Pb (II) solution. The remaining concentrations of the metal in the specified contact times were determined using Atomic Adsorption Spectrophotometer at 283.3 wavelength. The result showed that the equilibrium concentrations were obtained in about 30 minutes which depended on the initial concentration. The sorption mechanism followed Freundlich isotherm model where the adsorption constant and capacity were accordingly 1.353 and 1.195 mgg‑1. The iodine sorption was up to 1,053 mgg‑1. Based on the ash and moisture content, as well as iodine sorption, the activated carbon met the national standard.

Rapid adsorption of 2,4-dichlorophenoxyacetic acid by iron oxide nanoparticles-doped carboxylic ordered mesoporous carbon.

PubMed

Tang, Lin; Zhang, Sheng; Zeng, Guang-Ming; Zhang, Yi; Yang, Gui-De; Chen, Jun; Wang, Jing-Jing; Wang, Jia-Jia; Zhou, Yao-Yu; Deng, Yao-Cheng

2015-05-01

The ordered mesoporous carbon composite functionalized with carboxylate groups and iron oxide nanoparticles (Fe/OMC) was successfully prepared and used to adsorb 2,4-dichlorophenoxyacetic acid (2,4-D) from wastewater. The resultant adsorbent possessed high degree of order, large specific surface area and pore volume, and good magnetic properties. The increase in initial pollutant concentration and contact time would make the adsorption capacity increase, but the pH and temperature are inversely proportional to 2,4-D uptake. The equilibrium of adsorption was reached within 120 min, and the equilibrated adsorption capacity increased from 99.38 to 310.78 mg/g with the increase of initial concentration of 2,4-D from 100 to 500 mg/L. Notablely, the adsorption capacity reached 97% of the maximum within the first 5 min. The kinetics and isotherm study showed that the pseudo-second-order kinetic and Langmuir isotherm models could well fit the adsorption data. These results indicate that Fe/OMC has a good potential for the rapid adsorption of 2,4-D and prevention of its further diffusion. Copyright © 2014 Elsevier Inc. All rights reserved.

Optimization of Quenching Parameters for the Reduction of Titaniferous Magnetite Ore by Lean Grade Coal Using the Taguchi Method and Its Isothermal Kinetic Study

NASA Astrophysics Data System (ADS)

Sarkar, Bitan Kumar; Kumar, Nikhil; Dey, Rajib; Das, Gopes Chandra

2018-06-01

In the present study, a unique method is adopted to achieve higher reducibility of titaniferous magnetite lump ore (TMO). In this method, TMO is initially heated followed by water quenching. The quenching process generates cracks due to thermal shock in the dense TMO lumps, which, in turn, increases the extent of reduction (EOR) using the lean grade coal as a reductant. The optimum combination of parameters found by using Taguchi's L27 orthogonal array (OA) (five factors, three levels) is - 8 + 4 mm of particle size (PS1), 1423 K of quenching temperature (Qtemp2), 15 minutes of quenching time (Qtime3), 3 times the number of quenching {(No. of Q)3}, and 120 minutes of reduction time (Rtime3) at fixed reduction temperature of 1473 K. At optimized levels of the parameters, 92.39 pct reduction is achieved. Isothermal reduction kinetics of the quenched TMO lumps at the optimized condition reveals mixed controlled mechanisms [initially contracting geometry (CG3) followed by diffusion (D3)]. Activation energies calculated are 69.895 KJ/mole for CG3 and 39.084 KJ/mole for D3.

Lead sorption by waste biomass of hazelnut and almond shell.

PubMed

Pehlivan, Erol; Altun, Türkan; Cetin, Serpil; Iqbal Bhanger, M

2009-08-15

The potential to remove Pb(2+) ion from aqueous solutions using the shells of hazelnut (HNS) (Corylus avellana) and almond (AS) (Prunus dulcis) through biosorption was investigated in batch experiments. The main parameters influencing Pb(2+) ion sorption on HNS and AS were: initial metal ion concentration, amount of adsorbent, contact time and pH value of solution. The influences of initial Pb(2+) ion concentration (0.1-1.0mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been investigated. Equilibrium isotherms have been measured and modelled. Adsorption of Pb(2+) ions was in all cases pH-dependent showing a maximum at equilibrium pH values between 6.0 and 7.0, depending on the biomaterial, that corresponded to equilibrium pH values of 6.0 for HNS and 7.0 for AS. The equilibrium sorption capacities of HNS and AS were 28.18 and 8.08 mg/g for lead, respectively after equilibrium time of 2h. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that adsorption, chelation and ion exchange are major adsorption mechanisms for binding Pb(2+) ion to the sorbents.

Automated microfluidic platform for studies of carbon dioxide dissolution and solubility in physical solvents.

PubMed

Abolhasani, Milad; Singh, Mayank; Kumacheva, Eugenia; Günther, Axel

2012-05-07

We present an automated microfluidic (MF) approach for the systematic and rapid investigation of carbon dioxide (CO(2)) mass transfer and solubility in physical solvents. Uniformly sized bubbles of CO(2) with lengths exceeding the width of the microchannel (plugs) were isothermally generated in a co-flowing physical solvent within a gas-impermeable, silicon-based MF platform that is compatible with a wide range of solvents, temperatures and pressures. We dynamically determined the volume reduction of the plugs from images that were accommodated within a single field of view, six different downstream locations of the microchannel at any given flow condition. Evaluating plug sizes in real time allowed our automated strategy to suitably select inlet pressures and solvent flow rates such that otherwise dynamically self-selecting parameters (e.g., the plug size, the solvent segment size, and the plug velocity) could be either kept constant or systematically altered. Specifically, if a constant slug length was imposed, the volumetric dissolution rate of CO(2) could be deduced from the measured rate of plug shrinkage. The solubility of CO(2) in the physical solvent was obtained from a comparison between the terminal and the initial plug sizes. Solubility data were acquired every 5 min and were within 2-5% accuracy as compared to literature data. A parameter space consisting of the plug length, solvent slug length and plug velocity at the microchannel inlet was established for different CO(2)-solvent pairs with high and low gas solubilities. In a case study, we selected the gas-liquid pair CO(2)-dimethyl carbonate (DMC) and volumetric mass transfer coefficients 4-30 s(-1) (translating into mass transfer times between 0.25 s and 0.03 s), and Henry's constants, within the range of 6-12 MPa.

3D Finite Element Analysis of Spider Non-isothermal Forging Process

NASA Astrophysics Data System (ADS)

Niu, Ling; Wei, Wei; Wei, Kun Xia; Alexandrov, Igor V.; Hu, Jing

2016-06-01

The differences of effective stress, effective strain, velocity field, and the load-time curves between the spider isothermal and non-isothermal forging processes are investigated by making full use of 3D FEA, and verified by the production experiment of spider forging. Effective stress is mainly concentrated on the pin, and becomes lower closer to the front of the pin. The maximum effective strain in the non-isothermal forging is lower than that in the isothermal. The great majority of strain in the non-isothermal forging process is 1.76, which is larger than the strain of 1.31 in the isothermal forging. The maximum load required in the isothermal forging is higher than that in the non-isothermal. The maximum experimental load and deformation temperature in the spider production are in good agreement with those in the non-isothermal FEA. The results indicate that the non-isothermal 3D FEA results can guide the design of the spider forging process.

The temperature dependence of ponded infiltration under isothermal conditions

USGS Publications Warehouse

Constantz, J.; Murphy, F.

1991-01-01

A simple temperature-sensitive modification to the Green and Ampt infiltration equation is described; this assumes that the temperature dependence of the hydraulic conductivity is reciprocally equal to the temperature dependence of the viscosity of liquid water, and that both the transmission zone saturation and the wetting front matric potential gradient are independent of temperature. This modified Green and Ampt equation is compared with ponded, isothermal infiltration experiments run on repacked columns of Olympic Sand and Aiken Loam at 5, 25, and 60??C. Experimental results showed increases in infiltration rates of at least 300% between 5 and 60??C for both soil materials, with subsequent increases in cumulative infiltration of even greater magnitudes for the loam. There is good agreement between measured and predicted initial infiltration rates at 25??C for both soil materials, yet at 60??C, the predicted results overestimate initial infiltration rates for the sand and underestimate initial rates for the loam. Measurements of the wetting depth vs. cumulative infiltration indicate that the transmission zone saturation increased with increasing temperature for both soil materials. In spite of this increased saturation with temperature, the final infiltration rates at both 25 and 60??C were predicted accurately using the modified Green and Ampt equation. This suggests that increased saturation occurred primarily in dead-end pore spaces, so that transmission zone hydraulic conductivities were unaffected by these temperature-induced changes in saturation. In conclusion, except for initial infiltration rates at 60??C, the measured influence of temperature on infiltration rates was fully accounted for by the temperature dependence of the viscosity of liquid water. ?? 1991.

Lightning Evolution In Two North Central Florida Summer Multicell Storms and Three Winter/Spring Frontal Storms

NASA Astrophysics Data System (ADS)

Caicedo, J. A.; Uman, M. A.; Pilkey, J. T.

2018-01-01

We present the first lightning evolution studies, via the Lightning Mapping Array (LMA) and radar, performed in North Central Florida. Parts of three winter/spring frontal storms (cold season) and two complete summer (warm season) multicell storms are studied. Storm parameters measured are as follows: total number of flashes, flash-type classification, first flashes, flash initiation altitude, flash initiation power, flash rate (flashes per minute), charge structure, altitude and temperature ranges of the inferred charge regions, atmospheric isotherm altitude, radar base reflectivity (dBZ), and radar echo tops (EET). Several differences were found between summer multicell and winter/spring frontal storms in North Central Florida: (1) in winter/spring storms, the range of altitudes that all charge regions occupy is up to 1 km lower in altitude than in summer storms, as are the 0°C, -10°C, and -20°C isotherms; (2) lightning activity in summer storms is highly correlated with changes in radar signatures, in particular, echo tops; and (3) the LMA average initiation power of all flash types in winter/frontal storms is about an order of magnitude larger than that for summer storms. In relation to storms in other geographical locations, North Central Florida seasonal storms were found to have similarities in most parameters studied with a few differences, examples in Florida being (1) colder initiation altitudes for intracloud flashes, (2) charge regions occupying larger ranges of atmospheric temperatures, and (3) winter/spring frontal storms not having much lightning activity in the stratiform region.

Investigation of pore size and energy distributions by statistical physics formalism applied to agriculture products

NASA Astrophysics Data System (ADS)

Aouaini, Fatma; Knani, Salah; Yahia, Manel Ben; Bahloul, Neila; Ben Lamine, Abdelmottaleb; Kechaou, Nabil

2015-12-01

In this paper, we present a new investigation that allows determining the pore size distribution (PSD) in a porous medium. This PSD is achieved by using the desorption isotherms of four varieties of olive leaves. This is by the means of statistical physics formalism and Kelvin's law. The results are compared with those obtained with scanning electron microscopy. The effect of temperature on the distribution function of pores has been studied. The influence of each parameter on the PSD is interpreted. A similar function of adsorption energy distribution, AED, is deduced from the PSD.

Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 3: Operating manual

NASA Technical Reports Server (NTRS)

Maples, A. L.

1980-01-01

The operation of solidification model 1 is described. Model 1 calculates the macrosegregation in a rectangular ingot of a binary alloy as a result of horizontal axisymmetric bidirectional solidification. The calculation is restricted to steady-state solidification; there is no variation in final local average composition in the direction of isotherm movement. The physics of the model are given.

Comparison of linear and non-linear method in estimating the sorption isotherm parameters for safranin onto activated carbon.

PubMed

Kumar, K Vasanth; Sivanesan, S

2005-08-31

Comparison analysis of linear least square method and non-linear method for estimating the isotherm parameters was made using the experimental equilibrium data of safranin onto activated carbon at two different solution temperatures 305 and 313 K. Equilibrium data were fitted to Freundlich, Langmuir and Redlich-Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental equilibrium data. The results showed that non-linear method could be a better way to obtain the isotherm parameters. Redlich-Peterson isotherm is a special case of Langmuir isotherm when the Redlich-Peterson isotherm constant g was unity.

Comparative analysis of linear and non-linear method of estimating the sorption isotherm parameters for malachite green onto activated carbon.

PubMed

Kumar, K Vasanth

2006-08-21

The experimental equilibrium data of malachite green onto activated carbon were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear method. A comparison between linear and non-linear of estimating the isotherm parameters was discussed. The four different linearized form of Langmuir isotherm were also discussed. The results confirmed that the non-linear method as a better way to obtain isotherm parameters. The best fitting isotherm was Langmuir and Redlich-Peterson isotherm. Redlich-Peterson is a special case of Langmuir when the Redlich-Peterson isotherm constant g was unity.

Treatment of soil eluate containing nitro aromatic compounds by adsorption on activated coke (AC).

PubMed

Zhang, Yiping; Jiang, Zhenming; Zhao, Quanlin; Zhang, Zhenzhong; Su, Hongping; Gao, Xuewen; Ye, Zhengfang

2016-01-01

Soil washing is a kind of physical method to remove organic matters from contaminated soil. However, its eluate after washing may result in secondary pollution to the environment. In this study, activated coke (AC) was used to remove organic pollutants from contaminated soil eluate. The effect of temperature, initial chemical oxygen demand (COD) and AC dosage on COD removal efficiency was investigated. The results showed that the organic matter can be removed in the eluate because the COD dropped a lot. When the AC dosage was 20 g·L(-1), 88.92% of COD decreased after 480 min of adsorption at 50 °C. The process of adsorption can be described by the Redlich-Peterson isotherm. The adsorption was spontaneous and endothermic. The pseudo-second-order model can be used to describe the adsorption process. After adsorption, the acute toxicity of the eluate was reduced by 76%, and the water qualities were in agreement with Chinese discharge standard GB 14470.1-2002, which means the eluate could be discharged to the environment.

Functionally-interdependent shape-switching nanoparticles with controllable properties

PubMed Central

Halman, Justin R.; Satterwhite, Emily; Roark, Brandon; Chandler, Morgan; Viard, Mathias; Ivanina, Anna; Bindewald, Eckart; Kasprzak, Wojciech K.; Panigaj, Martin; Bui, My N.; Lu, Jacob S.; Miller, Johann; Khisamutdinov, Emil F.; Shapiro, Bruce A.; Dobrovolskaia, Marina A.

2017-01-01

Abstract We introduce a new concept that utilizes cognate nucleic acid nanoparticles which are fully complementary and functionally-interdependent to each other. In the described approach, the physical interaction between sets of designed nanoparticles initiates a rapid isothermal shape change which triggers the activation of multiple functionalities and biological pathways including transcription, energy transfer, functional aptamers and RNA interference. The individual nanoparticles are not active and have controllable kinetics of re-association and fine-tunable chemical and thermodynamic stabilities. Computational algorithms were developed to accurately predict melting temperatures of nanoparticles of various compositions and trace the process of their re-association in silico. Additionally, tunable immunostimulatory properties of described nanoparticles suggest that the particles that do not induce pro-inflammatory cytokines and high levels of interferons can be used as scaffolds to carry therapeutic oligonucleotides, while particles with strong interferon and mild pro-inflammatory cytokine induction may qualify as vaccine adjuvants. The presented concept provides a simple, cost-effective and straightforward model for the development of combinatorial regulation of biological processes in nucleic acid nanotechnology. PMID:28108656

Thermocapillary motion of deformable drops

NASA Technical Reports Server (NTRS)

Haj-Hariri, Hossein; Shi, Qingping; Borhan, Ali

1994-01-01

The thermocapillary motion of initially spherical drops/bubbles driven by a constant temperature gradient in an unbounded liquid medium is simulated numerically. Effects of convection of momentum and energy, as well as shape deformations, are addressed. The method used is based on interface tracking on a base cartesian grid, and uses a smeared color or indicator function for the determination of the surface topology. Quad-tree adaptive refinement of the cartesian grid is implemented to enhance the fidelity of the surface tracking. It is shown that convection of energy results in a slowing of the drop, as the isotherms get wrapped around the front of the drop. Shape deformation resulting from inertial effects affect the migration velocity. The physical results obtained are in agreement with the existing literature. Furthermore, remarks are made on the sensitivity of the calculated solutions to the smearing of the fluid properties. Analysis and simulations show that the migration velocity depends very strongly on the smearing of the interfacial force whereas it is rather insensitive to the smearing of other properties, hence the adaptive grid.

Residual stresses in high temperature corrosion of pure zirconium using elasto-viscoplastic model: Application to the deflection test in monofacial oxidation

NASA Astrophysics Data System (ADS)

Fettré, D.; Bouvier, S.; Favergeon, J.; Kurpaska, L.

2015-12-01

The paper is devoted to modeling residual stresses and strains in an oxide film formed during high temperature oxidation. It describes the deflection test in isothermal high-temperature monofacial oxidation (DTMO) of pure zirconium. The model incorporates kinetics and mechanism of oxidation and takes into account elastic, viscoplastic, growth and chemical strains. Different growth strains models are considered, namely, isotropic growth strains given by Pilling-Bedworth ratio, anisotropic growth strains defined by Parise and co-authors and physically based model for growth strain proposed by Clarke. Creep mechanisms based on dislocation slip and core diffusion, are used. A mechanism responsible for through thickness normal stress gradient in the oxide film is proposed. The material parameters are identified using deflection tests under 400 °C, 500 °C and 600 °C. The effect of temperature on creep and stress relaxation is analyzed. Numerical sensitivity study of the DTMO experiment is proposed in order to investigate the effects of the initial foil thickness and platinum coating on the deflection curves.

Determination of the magnetocaloric entropy change by field sweep using a heat flux setup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, J. C. B., E-mail: jolmiui@gmail.com; Reis, R. D. dos; Mansanares, A. M.

2014-08-18

We report on a simple setup using a heat flux sensor adapted to a Quantum Design Physical Property Measurement System to determine the magnetocaloric entropy change (ΔS). The major differences for the existing setups are the simplicity of this assembly and the ease to obtain the isothermal entropy change either by a field sweep or a temperature sweep process. We discuss the use of these two processes applied to Gd and Gd{sub 5}Ge{sub 2}Si{sub 2} samples. The results are compared to the temperature sweep measurements and they show the advantages of this setup and of the field sweep procedure. Wemore » found a significant reduction of ΔS and on the refrigerating cooling power (RCP) at low field changes in a field sweep process when the sample is not driven to the same initial state for each temperature. We show that the field sweep process without any measuring protocol is the only correct way to experimentally determine ΔS and RCP for a practical regenerative refrigerator.« less

Wave-driven winds from cool stars. I - Some effects of magnetic field geometry

NASA Technical Reports Server (NTRS)

Hartmann, L.; Macgregor, K. B.

1982-01-01

The wave-driven wind theory of Hartmann and MacGregor (1980) is extended to include effects due to non-radial divergence of the flow. Specifically, isothermal expansion within a flow tube whose cross-sectional area increases outward faster than the square of the radius near the stellar surface is considered. It is found that the qualitative conclusions of Hartmann and MacGregor concerning the physical properties of Alfven wave-driven winds are largely unaffected. In particular, mass fluxes of similar magnitude are obtained, and wave dissipation is still necessary to produce acceptably small terminal velocities. Increasingly divergent flow geometries generally lead to higher initial wind speeds and slightly lower terminal velocities. For some cases of extremely rapid flow tube divergence, steady supersonic wind solutions which extend to infinity with vanishing gas pressure cannot be obtained. In addition, departures from spherical symmetry can cause the relative Alfven wave amplitude delta-B/B to become approximately greater than 1 within several stellar radii of the base of the wind, suggesting that nonlinear processes may contribute to the wave dissipation required by the theory.

Multiple stable isotope fronts during non-isothermal fluid flow

NASA Astrophysics Data System (ADS)

Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

2018-02-01

Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may develop in kinetically limited systems, which propagates with the advection speed of the incoming fluid and is, therefore, traveling fastest. The results show that oxygen isotope signatures at thermal fronts recorded in rocks and veins that experienced isotope exchange with fluids can easily be misinterpreted, namely if bulk analytical techniques are applied. However, stable isotope microanalysis on precipitated minerals may - if later isotope exchange is kinetically limited - provide a valuable archive of the transient thermal and hydrological evolution of a system.

Atrazine Adsorption Potential of Leonardite from Mae Moh Power Plant

NASA Astrophysics Data System (ADS)

Rittirat, A.; Chokejaroenrat, C.; Watcharenwong, A.

2018-01-01

Leonardite is an immature coal from the power plant, which we obtained from Lampang province, Thailand. It is known to contain relatively high humic substance making it suitable as the soil conditioner in agricultural aspect and as an adsorbent. Our objectives were: [1] to determine the leonardite physical and chemical properties (e.g., cation exchange capacity, organic matter content, and electron microscope imaging), and (2) to quantify the adsorption efficiency of atrazine from the soil. We used varied amount of leonardite ranging from 0.05 to 1.60 g to adsorb 8 mg L-1 of atrazine from aqueous solution in a batch experiment. This experiment was achieved within 48 hours so that the equilibrium time and isotherm parameters can be determined. The uncarbonized leonardite characteristic revealed that it could adsorb atrazine as its surface possesses mesopore type, relatively high cation exchange capacity (59.89 cmol Kg-1), and high organic matter of 21.62 %. The isotherm study showed the equilibrium time of 24 hours and adsorption isotherm was Langmuir with qmax of 3.9683 mg g-1. This study provides proof that leonardite used in the agricultural field can also be useful to adsorb atrazine and simultaneously slow the percolating process of atrazine before contaminating groundwater.

Protein adsorption on electrospun zinc doped hydroxyapatite containing nylon 6 membrane: kinetics and isotherm.

PubMed

Esfahani, Hamid; Prabhakaran, Molamma P; Salahi, Esmaeil; Tayebifard, Ali; Keyanpour-Rad, Mansour; Rahimipour, Mohamad Reza; Ramakrishna, Seeram

2015-04-01

Surface modification of electrospun polymeric membrane surfaces is a critical step towards the separation process including protein adsorption. In this study, the electrospun Nylon fibers was incorporated with positively charged zinc doped hydroxyapatite (HAp) nanoparticles to study the adsorption of negatively charged proteins, namely bovine serum albumin (BSA). Effects of zinc amount within the atomic structure of HAp (nZH; n=0, 4, 8 At.%) was evaluated on produced scaffolds and consequently protein adsorption. The results showed that the ability of Nylon membrane to adsorb BSA increased with incorporation of nZH nanoparticles within the nylon structure. This phenomenon is appeared to be relate to different electrostatic charge and not to physical characteristic of scaffolds. The incorporated membrane (N-4ZH) by nanoparticles with highest zeta (ξ) potential adsorbed the maximum amount of protein. The adsorption of BSA was best fitted with pseudo-second order kinetic model. The experimental isotherm data were further analyzed by using Langmuir and Freundlich equations. By comparing the correlation coefficients obtained for each linear transformation of isotherm analysis, it was found that the Langmuir equation was the best fit equilibrium model that described the adsorption of BSA on these membranes. Copyright © 2014 Elsevier Inc. All rights reserved.

Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

PubMed Central

Bender, P.; Bogart, L. K.; Posth, O.; Szczerba, W.; Rogers, S. E.; Castro, A.; Nilsson, L.; Zeng, L. J.; Sugunan, A.; Sommertune, J.; Fornara, A.; González-Alonso, D.; Barquín, L. Fernández; Johansson, C.

2017-01-01

The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions. PMID:28397851

Kinetic and thermodynamic studies of AISI 4130 steel alloy corrosion in ethylene glycol-water mixture in presence of inhibitors

NASA Astrophysics Data System (ADS)

Khomami, M. Niknejad; Danaee, I.; Attar, A. A.; Peykari, M.

2013-05-01

The electrochemical behavior of steel alloy in ethylene glycol-water mixture was investigated by electrochemical methods. The results obtained showed that corrosion rate was decreased with increasing ethylene glycol concentration. The effect of inorganic inhibitors including NO3 -, NO2 -, Cr2O7 2- and CrO4 2- were studied using electrochemical techniques where the highest inhibition efficiency was obtained for CrO4 2-. In the presence of chromate the inhibitor efficiency increased with its concentration. The inhibiting effect of the chromate was explained on the basis of the competitive adsorption between the inorganic anions and the aggressive Cl- ions, and the adsorption isotherm basically obeys the Langmuir adsorption isotherm. Thermodynamic parameters for steel corrosion and inhibitor adsorption were determined and reveal that the adsorption process is spontaneous. Also, a phenomenon of both physical and chemical adsorption is proposed.

Application of Glycyrrhiza glabra Root as a Novel Adsorbent in the Removal of Toluene Vapors: Equilibrium, Kinetic, and Thermodynamic Study

PubMed Central

Mohammadi-Moghadam, Fazel; Amin, Mohammad Mehdi; Khiadani (Hajian), Mehdi; Momenbeik, Fariborz; Nourmoradi, Heshmatollah; Hatamipour, Mohammad Sadegh

2013-01-01

The aim of this paper is to investigate the removal of toluene from gaseous solution through Glycyrrhiza glabra root (GGR) as a waste material. The batch adsorption experiments were conducted at various conditions including contact time, adsorbate concentration, humidity, and temperature. The adsorption capacity was increased by raising the sorbent humidity up to 50 percent. The adsorption of toluene was also increased over contact time by 12 h when the sorbent was saturated. The pseudo-second-order kinetic model and Freundlich model fitted the adsorption data better than other kinetic and isotherm models, respectively. The Dubinin-Radushkevich (D-R) isotherm also showed that the sorption by GGR was physical in nature. The results of the thermodynamic analysis illustrated that the adsorption process is exothermic. GGR as a novel adsorbent has not previously been used for the adsorption of pollutants. PMID:23554821

Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution.

PubMed

Feng, Li; Zhang, Shengtao; Qiang, Yujie; Xu, Yue; Guo, Lei; Madkour, Loutfy H; Chen, Shijin

2018-06-19

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption. The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us better understand the corrosion inhibition process and improve it.

The diffuse extreme-ultraviolet background - Constraints on hot coronal plasma

NASA Technical Reports Server (NTRS)

Paresce, F.; Stern, R.

1981-01-01

The Apollo-Soyuz data and data reported by Cash et al. (1976) have been reanalyzed in terms of both isothermal models and temperature distribution models. In the latter case, a power-law form is assumed for the relation between emission measure and temperature. A new upper limit on diffuse flux in the 20-73 eV band derived from Apollo-Soyuz observations made in the earth's shadow has been incorporated in the calculation. In the considered investigation the results of the new analysis are presented and the implications for the physical properties of the hot component of the interstellar medium are discussed. The analysis of the Berkeley extreme ultraviolet (EUV) diffuse background measurements using either isothermal or power law temperature distribution models for the emitting plasma indicates excellent qualitative agreement with hard X-ray data that suggest the sun to be immersed in a hot plasma that pervades most of space out to approximately 100 pc.

The biosorption of heavy metals from aqueous solution by Spirogyra and Cladophora filamentous macroalgae.

PubMed

Lee, Yi-Chao; Chang, Shui-Ping

2011-05-01

The aim of this research was to develop a low cost adsorbent for wastewater treatment. The prime objective of this study was to search for suitable freshwater filamentous algae that have a high heavy metal ion removal capability. This study evaluated the biosorption capacity from aqueous solutions of the green algae species, Spirogyra and Cladophora, for lead (Pb(II)) and copper (Cu(II)). In comparing the analysis of the Langmuir and Freundlich isotherm models, the adsorption of Pb(II) and Cu(II) by these two types of biosorbents showed a better fit with the Langmuir isotherm model. In the adsorption of heavy metal ions by these two types of biosorbents, chemical and physical adsorption of particle surfaces was perhaps more significant than diffusion and adsorption between particles. Continuous adsorption-desorption experiments discovered that both types of biomass were excellent biosorbents with potential for further development. Copyright © 2011 Elsevier Ltd. All rights reserved.

Bioelectrochemistry of non-covalent immobilized alcohol dehydrogenase on oxidized diamond nanoparticles.

PubMed

Nicolau, Eduardo; Méndez, Jessica; Fonseca, José J; Griebenow, Kai; Cabrera, Carlos R

2012-06-01

Diamond nanoparticles are considered a biocompatible material mainly due to their non-cytotoxicity and remarkable cellular uptake. Model proteins such as cytochrome c and lysozyme have been physically adsorbed onto diamond nanoparticles, proving it to be a suitable surface for high protein loading. Herein, we explore the non-covalent immobilization of the redox enzyme alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae (E.C.1.1.1.1) onto oxidized diamond nanoparticles for bioelectrochemical applications. Diamond nanoparticles were first oxidized and physically characterized by X-ray diffraction (XRD), FT-IR and TEM. Langmuir isotherms were constructed to investigate the ADH adsorption onto the diamond nanoparticles as a function of pH. It was found that a higher packing density is achieved at the isoelectric point of the enzyme. Moreover, the relative activity of the immobilized enzyme on diamond nanoparticles was addressed under optimum pH conditions able to retain up to 70% of its initial activity. Thereafter, an ethanol bioelectrochemical cell was constructed by employing the immobilized alcohol dehydrogenase onto diamond nanoparticles, this being able to provide a current increment of 72% when compared to the blank solution. The results of this investigation suggest that this technology may be useful for the construction of alcohol biosensors or biofuel cells in the near future. Copyright © 2011 Elsevier B.V. All rights reserved.

High temperature polymerization monitoring of an epoxy resin using ultrasound

NASA Astrophysics Data System (ADS)

Maréchal, P.; Ghodhbani, N.; Duflo, H.

2018-05-01

In this study, the real time ultrasonic monitoring is investigated to quantify changes in physical and mechanical properties during the manufacture of composite structures. In this context, an experimental transmission was developed with the aim of characterizing a high temperature polymerization reaction and post-curing properties using an ultrasonic method. First, the monitoring of ultrasonic parameters of a thermosetting resin is carried out in a device reproducing the experimental conditions for manufacturing a composite material with a process known as RTM, that is to say an isothermal polymerization at T = 160°C. During this curing, the resin is changing from its initial viscous liquid state to its final viscous solid state. Between those states, a glassy transition stage is observed, during which the physical properties are strongly changing, i.e. an increase of the ultrasonic velocity up to its steady value and a transient increase of the ultrasonic attenuation. Second, the ultrasonic inspection of the thermosetting resin is performed during a heating and cooling process to study the temperature sensitivity after curing. This type of characterization leads to identifying the ultrasonic properties dependence before, during and after the glassy transition temperature Tg . Eventually, this study is composed of two complementary parts: the first is useful for the curing optimization, while the second one is fruitful for the post-processing characterization in a temperature range including the glassy transition temperature Tg .

Comparison of various error functions in predicting the optimum isotherm by linear and non-linear regression analysis for the sorption of basic red 9 by activated carbon.

PubMed

Kumar, K Vasanth; Porkodi, K; Rocha, F

2008-01-15

A comparison of linear and non-linear regression method in selecting the optimum isotherm was made to the experimental equilibrium data of basic red 9 sorption by activated carbon. The r(2) was used to select the best fit linear theoretical isotherm. In the case of non-linear regression method, six error functions namely coefficient of determination (r(2)), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), the average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS) were used to predict the parameters involved in the two and three parameter isotherms and also to predict the optimum isotherm. Non-linear regression was found to be a better way to obtain the parameters involved in the isotherms and also the optimum isotherm. For two parameter isotherm, MPSD was found to be the best error function in minimizing the error distribution between the experimental equilibrium data and predicted isotherms. In the case of three parameter isotherm, r(2) was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. The present study showed that the size of the error function alone is not a deciding factor to choose the optimum isotherm. In addition to the size of error function, the theory behind the predicted isotherm should be verified with the help of experimental data while selecting the optimum isotherm. A coefficient of non-determination, K(2) was explained and was found to be very useful in identifying the best error function while selecting the optimum isotherm.

Microstructural Evolution and the Precipitation Behavior in X90 Linepipe Steel During Isothermal Processing

NASA Astrophysics Data System (ADS)

Tian, Y.; Wang, H. T.; Wang, Z. D.; Misra, R. D. K.; Wang, G. D.

2018-03-01

Thermomechanical controlled processing of 560-MPa (X90) linepipe steel was simulated in the laboratory using a thermomechanical simulator to study the microstructural evolution and precipitation behavior during isothermal holding. The results indicated that martensite was obtained when the steels were isothermally held for 5 s at 700 °C. Subsequently, granular bainite and acicular ferrite transformation occurred with increased holding time. Different amount of polygonal ferrite formed after isothermally holding for 600-3600 s. Pearlite nucleated after isothermally holding for 3600 s. Precipitation occurred after isothermal holding for 5 s and continuous precipitation occurred at grain boundaries after isothermally holding for 600 s. After isothermally holding for 3600 s, large Nb/Ti carbide precipitated. The presence of MX-type precipitates was confirmed by diffraction pattern. The interphase precipitation (IP) occurred between 5 and 30 s. Maximum hardness was obtained after isothermally holding for 600 s when IP occurred and rapidly decreased to a low value, mainly because polygonal ferrite dominated the microstructure after isothermally holding for 3600 s.

Porous media augmented with biochar for the retention of E. coli

NASA Astrophysics Data System (ADS)

Kolotouros, Christos A.; Manariotis, Ioannis D.; Karapanagioti, Hrissi K.

2016-04-01

A significant number of epidemic outbreaks has been attributed to waterborne fecal-borne pathogenic microorganisms from contaminated ground water. The transport of pathogenic microorganisms in groundwater is controlled by physical and chemical soil properties like soil structure, texture, percent water saturation, soil ionic strength, pore-size distribution, soil and solution pH, soil surface charge, and concentration of organic carbon in solution. Biochar can increase soil productivity by improving both chemical and physical soil properties. The mixing of biochar into soils may stimulate microbial population and activate dormant soil microorganisms. Furthermore, the application of biochar into soil affects the mobility of microorganisms by altering the physical and chemical properties of the soil, and by retaining the microorganisms on the biochar surface. The aim of this study was to investigate the effect of biochar mixing into soil on the transport of Escherichia coli in saturated porous media. Initially, batch experiments were conducted at two different ionic strengths (1 and 150 mM KCl) and at varying E. coli concentrations in order to evaluate the retention of E. coli on biochar in aqueous solutions. Kinetic analysis was conducted, and three isotherm models were employed to analyze the experimental data. Column experiments were also conducted in saturated sand columns augmented with different biochar contents, in order to examine the effect of biochar on the retention of E. coli. The Langmuir model fitted better the retention experimental data, compared to Freundlich and Tempkin models. The retention of E. coli was enhanced at lower ionic strength. Finally, biochar-augmented sand columns were more capable in retaining E. coli than pure sand columns.

A Field Study on Simulation of CO 2 Injection and ECBM Production and Prediction of CO 2 Storage Capacity in Unmineable Coal Seam

DOE PAGES

He, Qin; Mohaghegh, Shahab D.; Gholami, Vida

2013-01-01

CO 2 sequestration into a coal seam project was studied and a numerical model was developed in this paper to simulate the primary and secondary coal bed methane production (CBM/ECBM) and carbon dioxide (CO 2 ) injection. The key geological and reservoir parameters, which are germane to driving enhanced coal bed methane (ECBM) and CO 2 sequestration processes, including cleat permeability, cleat porosity, CH 4 adsorption time, CO 2 adsorption time, CH 4 Langmuir isotherm, CO 2 Langmuir isotherm, and Palmer and Mansoori parameters, have been analyzed within a reasonable range. The model simulation results showed good matches for bothmore » CBM/ECBM production and CO 2 injection compared with the field data. The history-matched model was used to estimate the total CO 2 sequestration capacity in the field. The model forecast showed that the total CO 2 injection capacity in the coal seam could be 22,817 tons, which is in agreement with the initial estimations based on the Langmuir isotherm experiment. Total CO 2 injected in the first three years was 2,600 tons, which according to the model has increased methane recovery (due to ECBM) by 6,700 scf/d.« less

Preparation and characterization of poly(AA co PVP)/PGS composite and its application for methylene blue adsorption.

PubMed

Yang, Cai-xia; Lei, Lei; Zhou, Peng-xin; Zhang, Zhe; Lei, Zi-qiang

2015-04-01

Poly (AA co PVP)/PGS (PAPP) composite adsorbent was prepared by radical polymerization from Acrylic acid (AA), Polyvinylpyrrolidone (PVP) and Palygorskite (PGS), using N,N-methylenebisacrylamide (MBA) as cross-linker and potassium persulfate (KPS) as initiator. The PAPP was characterized with Fourier transform infrared (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM) and transmission electron microscopy (TEM). PAPP was used as adsorbent for the removal of methylene blue from aqueous solutions. The influences of pH, adsorption temperature and adsorption time on the adsorption properties of the composite to the dye were also investigated. Meanwhile, the adsorption rate data and adsorption equilibrium date were analyzed based on the pseudo-first-order and pseudo-second-order kinetic model, Langmuir and Freundlich isotherm models, respectively. The results indicating that the kinetic behavior better fit with the pseudo-second-order kinetic model. The maximum equilibrium adsorption capacity (q(m)) is 1815 mg/g at 289 K. The isotherm behavior can be explained by the Langmuir isotherm models. The activation energy was also evaluated for the removal of methylene blue onto PAPP. These results demonstrate that this composite material could be used as a good adsorbent for the removal of cationic dyes from wastewater. Copyright © 2014 Elsevier Inc. All rights reserved.

Non-isothermal Crystallization Kinetics of Mold Fluxes for Casting High-Aluminum Steels

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Li, Huan; Wang, Wanlin; Wu, Zhaoyang; Yu, Jie; Xie, Senlin

2017-12-01

This paper investigates the crystallization behavior of CaO-SiO2- and CaO-Al2O3-based mold fluxes for casting high-aluminum steels using single hot thermocouple technology, developed kinetic models, and scanning electron microscope. The results showed that the crystallization ability of the typical CaO-SiO2-based Flux A (CaO/SiO2 0.62, Al2O3 2 mass pct) is weaker than that of CaO-Al2O3-based Flux B (CaO/SiO2 4.11, Al2O3 31.9 mass pct) because of its higher initial crystallization temperature. The crystallization kinetics of Flux A was "surface nucleation and growth, interface reaction control" in the overall non-isothermal crystallization process, whereas that of Flux B was "constant nucleation rate, 1-dimensional growth, diffusion control, in the primary crystallization stage, and then transformed into constant nucleation rate, 3-dimensional growth, interface reaction control in the secondary crystallization stage." The energy dispersive spectroscopy results for Flux B suggested that the variations in the crystallization kinetics for Flux B are due to different crystals precipitating in the primary (BaCa2Al8O15) and secondary (CaAl2O4) crystallization periods during the non-isothermal crystallization process.

Studies on adsorption of phenol from wastewater by agricultural waste.

PubMed

Girish, C R; Ramachandramurty, V

2013-07-01

In this paper, preliminary investigation of various agricultural wastes-Rice mill residue (RM), Wheat mill reside (WM), Dall mill residue (DM) and the Banana peels (BM) was carried out to study their ability to be used as adsorbents for phenol-removal from wastewater. This study reports the feasibility of employing dal mill residue waste (DM) as an adsorbent for removing phenol from wastewater. The performance of DM was compared with the commercially available activated carbon (CAC). Batch mode experiments were conducted with activated DM to study the effects of initial concentration of phenol, pH and the temperature of aqueous solution on adsorption. Equilibrium adsorption isotherms and kinetics were investigated. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models and the isotherm data fitted well to the Freundlich isotherm with monolayer adsorption capacity of 6.189 mg/g. The kinetic data obtained at different concentrations were analyzed using a pseudo-first order and pseudo-second- order equation. The experimental data fitted very well with the pseudo-first-order kinetic model. The FTIR analysis revealed that carboxyl and hydroxyl functional groups were mainly responsible for the sorption of phenol. Finally, the DM was found to be a promising adsorbent for phenol adsorption as compared to activated carbon.

Fully kinetic simulations of collisionless, mesothermal plasma emission: Macroscopic plume structure and microscopic electron characteristics

NASA Astrophysics Data System (ADS)

Hu, Yuan; Wang, Joseph

2017-03-01

This paper presents a fully kinetic particle particle-in-cell simulation study on the emission of a collisionless plasma plume consisting of cold beam ions and thermal electrons. Results are presented for both the two-dimensional macroscopic plume structure and the microscopic electron kinetic characteristics. We find that the macroscopic plume structure exhibits several distinctive regions, including an undisturbed core region, an electron cooling expansion region, and an electron isothermal expansion region. The properties of each region are determined by microscopic electron kinetic characteristics. The division between the undisturbed region and the cooling expansion region approximately matches the Mach line generated at the edge of the emission surface, and that between the cooling expansion region and the isothermal expansion region approximately matches the potential well established in the beam. The interactions between electrons and the potential well lead to a new, near-equilibrium state different from the initial distribution for the electrons in the isothermal expansion region. The electron kinetic characteristics in the plume are also very anisotropic. As the electron expansion process is mostly non-equilibrium and anisotropic, the commonly used assumption that the electrons in a collisionless, mesothermal plasma plume may be treated as a single equilibrium fluid in general is not valid.

Simultaneous removal of heavy-metal ions in wastewater samples using nano-alumina modified with 2,4-dinitrophenylhydrazine.

PubMed

Afkhami, Abbas; Saber-Tehrani, Mohammad; Bagheri, Hasan

2010-09-15

2,4-Dinitrophenylhydrazine (DNPH) immobilized on sodium dodecyl sulfate coated nano-alumina was developed for the removal of metal cations Pb(II), Cd(II), Cr(III), Co(II), Ni(II) and Mn(II) from water samples. The research results displayed that adsorbent has the highest adsorption capacity for Pb(II), Cr(III) and Cd(II) in ions mixture system. Optimal experimental conditions including pH, adsorbent dosage and contact time have been established. Langmuir and Freundlich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data was given by the Freundlich adsorption isotherm equation for Mn(II), Pb(II), Cr(III) and Cd(II) ions and by Langmuir isotherm equation for Ni(II) and Co(II) ions. Desorption experiments by elution of the adsorbent with a mixture of nitric acid and methanol show that the modified alumina nanoparticles could be reused without significant losses of its initial properties even after three adsorption-desorption cycles. Thus, modified nano-alumina with DNPH is favorable and useful for the removal of these metal ions, and the high adsorption capacity makes it a good promising candidate material for Pb(II),Cr(III) and Cd(II) removal. Copyright 2010 Elsevier B.V. All rights reserved.

The sorption of lead, cadmium, copper and zinc ions from aqueous solutions on a raw diatomite from Algeria.

PubMed

Safa, Messaouda; Larouci, Mohammed; Meddah, Boumediene; Valemens, Pierre

2012-01-01

The adsorption of Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions from aqueous solution by Algerian raw diatomite was studied. The influences of different sorption parameters such as contact pH solution, contact time and initial metal ions concentration were studied to optimize the reaction conditions. The metals ions adsorption was strictly pH dependent. The maximum adsorption capacities towards Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were 0.319, 0.311, 0.18 and 0.096 mmol g(-1), respectively. The kinetic data were modelled using the pseudo-first-order and pseudo-second-order kinetic equations. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analysed using the Langmuir and the Freundlich isotherms; the results showed that the adsorption equilibrium was well described by both model isotherms. The negative value of free energy change ΔG indicates feasible and spontaneous adsorption of four metal ions on raw diatomite. According to these results, the high exchange capacities of different metal ions at high and low concentration levels, and given the low cost of the investigated adsorbent in this work, Algerian diatomite was considered to be an excellent adsorbent.

Rapid and Sensitive Isothermal Detection of Nucleic-acid Sequence by Multiple Cross Displacement Amplification.

PubMed

Wang, Yi; Wang, Yan; Ma, Ai-Jing; Li, Dong-Xun; Luo, Li-Juan; Liu, Dong-Xin; Jin, Dong; Liu, Kai; Ye, Chang-Yun

2015-07-08

We have devised a novel amplification strategy based on isothermal strand-displacement polymerization reaction, which was termed multiple cross displacement amplification (MCDA). The approach employed a set of ten specially designed primers spanning ten distinct regions of target sequence and was preceded at a constant temperature (61-65 °C). At the assay temperature, the double-stranded DNAs were at dynamic reaction environment of primer-template hybrid, thus the high concentration of primers annealed to the template strands without a denaturing step to initiate the synthesis. For the subsequent isothermal amplification step, a series of primer binding and extension events yielded several single-stranded DNAs and single-stranded single stem-loop DNA structures. Then, these DNA products enabled the strand-displacement reaction to enter into the exponential amplification. Three mainstream methods, including colorimetric indicators, agarose gel electrophoresis and real-time turbidity, were selected for monitoring the MCDA reaction. Moreover, the practical application of the MCDA assay was successfully evaluated by detecting the target pathogen nucleic acid in pork samples, which offered advantages on quick results, modest equipment requirements, easiness in operation, and high specificity and sensitivity. Here we expounded the basic MCDA mechanism and also provided details on an alternative (Single-MCDA assay, S-MCDA) to MCDA technique.

The removal of arsenate from water using iron-modified diatomite (D-Fe): isotherm and column experiments.

PubMed

Pantoja, M L; Jones, H; Garelick, H; Mohamedbakr, H G; Burkitbayev, M

2014-01-01

Iron hydroxide supported onto porous diatomite (D-Fe) is a low-cost material with potential to remove arsenic from contaminated water due to its affinity for the arsenate ion. This affinity was tested under varying conditions of pH, contact time, iron content in D-Fe and the presence of competitive ions, silicate and phosphate. Batch and column experiments were conducted to derive adsorption isotherms and breakthrough behaviours (50 μg L(-1)) for an initial concentration of 1,000 μg L(-1). Maximum capacity at pH 4 and 17% iron was 18.12-40.82 mg of arsenic/g of D-Fe and at pH 4 and 10% iron was 18.48-29.07 mg of arsenic/g of D-Fe. Adsorption decreased in the presence of phosphate and silicate ions. The difference in column adsorption behaviour between 10% and 17% iron was very pronounced, outweighing the impact of all other measured parameters. There was insufficient evidence of a correlation between iron content and arsenic content in isotherm experiments, suggesting that ion exchange is a negligible process occurring in arsenate adsorption using D-Fe nor is there co-precipitation of arsenate by rising iron content of the solute above saturation.

Biosorption of cadmium and lead from aqueous solution by fresh water alga Anabaena sphaerica biomass.

PubMed

Abdel-Aty, Azza M; Ammar, Nabila S; Abdel Ghafar, Hany H; Ali, Rizka K

2013-07-01

The present work represents the biosorption of Cd(II) and Pb(II) from aqueous solution onto the biomass of the blue green alga Anabaena sphaerica as a function of pH, biosorbent dosage, contact time, and initial metal ion concentrations. Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of both metals by A. sphaerica biomass. The biosorption isotherms studies indicated that the biosorption of Cd(II) and Pb(II) follows the Langmuir and Freundlish models. The maximum biosorption capacities (qmax ) were 111.1 and 121.95 mg/g, respectively, at the optimum conditions for each metal. From the D-R isotherm model, the mean free energy was calculated to be 11.7 and 14.3 kJ/mol indicating that the biosorption mechanism of Cd(II) and Pb(II) by A. sphaerica was chemisorption. The FTIR analysis for surface function group of algal biomass revealed the existence of amino, carboxyl, hydroxyl, and carbonyl groups, which are responsible for the biosorption of Cd(II) and Pb(II). The results suggested that the biomass of A. sphaerica is an extremely efficient biosorbent for the removal of Cd(II) and Pb(II) from aqueous solutions.

Mechanisms of Alizarin Red S and Methylene blue biosorption onto olive stone by-product: Isotherm study in single and binary systems.

PubMed

Albadarin, Ahmad B; Mangwandi, Chirangano

2015-12-01

The biosorption process of anionic dye Alizarin Red S (ARS) and cationic dye methylene blue (MB) as a function of contact time, initial concentration and solution pH onto olive stone (OS) biomass has been investigated. Equilibrium biosorption isotherms in single and binary systems and kinetics in batch mode were also examined. The kinetic data of the two dyes were better described by the pseudo second-order model. At low concentration, ARS dye appeared to follow a two-step diffusion process, while MB dye followed a three-step diffusion process. The biosorption experimental data for ARS and MB dyes were well suited to the Redlich-Peterson isotherm. The maximum biosorption of ARS dye, qmax = 16.10 mg/g, was obtained at pH 3.28 and the maximum biosorption of MB dye, qmax = 13.20 mg/g, was observed at basic pH values. In the binary system, it was indicated that the MB dye diffuses firstly inside the biosorbent particle and occupies the biosorption sites forming a monodentate complex and then the ARS dye enters and can only bind to untaken sites; forms a tridentate complex with OS active sites. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biosorption of cadmium and lead from aqueous solution by fresh water alga Anabaena sphaerica biomass

PubMed Central

Abdel -Aty, Azza M.; Ammar, Nabila S.; Abdel Ghafar, Hany H.; Ali, Rizka K.

2012-01-01

The present work represents the biosorption of Cd(II) and Pb(II) from aqueous solution onto the biomass of the blue green alga Anabaena sphaerica as a function of pH, biosorbent dosage, contact time, and initial metal ion concentrations. Freundlich, Langmuir, and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherm of both metals by A. sphaerica biomass. The biosorption isotherms studies indicated that the biosorption of Cd(II) and Pb(II) follows the Langmuir and Freundlish models. The maximum biosorption capacities (qmax) were 111.1 and 121.95 mg/g, respectively, at the optimum conditions for each metal. From the D–R isotherm model, the mean free energy was calculated to be 11.7 and 14.3 kJ/mol indicating that the biosorption mechanism of Cd(II) and Pb(II) by A. sphaerica was chemisorption. The FTIR analysis for surface function group of algal biomass revealed the existence of amino, carboxyl, hydroxyl, and carbonyl groups, which are responsible for the biosorption of Cd(II) and Pb(II). The results suggested that the biomass of A. sphaerica is an extremely efficient biosorbent for the removal of Cd(II) and Pb(II) from aqueous solutions. PMID:25685442

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

PubMed Central

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

Adsorptive Removal of Cadmium (II) from Aqueous Solution by Multi-Carboxylic-Functionalized Silica Gel: Equilibrium, Kinetics and Thermodynamics

NASA Astrophysics Data System (ADS)

Li, Min; Meng, Xiaojing; Yuan, Jinhai; Deng, Wenwen; 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 various experimental parameters such as pH value, contact time and initial concentration 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. Equilibrium isotherms for the adsorption of cadmium (II) ion were analyzed by Freundlich and Langmuir isotherm models, the results indicate that Langmuir isotherm model was found to be credible to express the data for cadmium (II) ion from aqueous solution onto the SG-MCF. Various thermodynamics parameters of the adsorption process, including free energy of adsorption (ΔG0 ), the enthalpy of adsorption (ΔH0 ) and standard entropy changes (ΔS0 ), were calculated to predict the nature of adsorption. The positive value of the enthalpy change and the negative value of free energy change indicate that the process is endothermic and spontaneous process.

Functional thermo-dynamics: a generalization of dynamic density functional theory to non-isothermal situations.

PubMed

Anero, Jesús G; Español, Pep; Tarazona, Pedro

2013-07-21

We present a generalization of Density Functional Theory (DFT) to non-equilibrium non-isothermal situations. By using the original approach set forth by Gibbs in his consideration of Macroscopic Thermodynamics (MT), we consider a Functional Thermo-Dynamics (FTD) description based on the density field and the energy density field. A crucial ingredient of the theory is an entropy functional, which is a concave functional. Therefore, there is a one to one connection between the density and energy fields with the conjugate thermodynamic fields. The connection between the three levels of description (MT, DFT, FTD) is clarified through a bridge theorem that relates the entropy of different levels of description and that constitutes a generalization of Mermin's theorem to arbitrary levels of description whose relevant variables are connected linearly. Although the FTD level of description does not provide any new information about averages and correlations at equilibrium, it is a crucial ingredient for the dynamics in non-equilibrium states. We obtain with the technique of projection operators the set of dynamic equations that describe the evolution of the density and energy density fields from an initial non-equilibrium state towards equilibrium. These equations generalize time dependent density functional theory to non-isothermal situations. We also present an explicit model for the entropy functional for hard spheres.

Equilibrium and kinetic adsorption study of Basic Yellow 28 and Basic Red 46 by a boron industry waste.

PubMed

Olgun, Asim; Atar, Necip

2009-01-15

In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73mgg(-1), respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23kJ/mol for BY 28 and 18.15kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents.

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

PubMed

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.

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose hydrogels reinforced with graphene oxide and bentonite for enhanced adsorption of methylene blue.

PubMed

Dai, Hongjie; Huang, Yue; Huang, Huihua

2018-04-01

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose (isolated from pineapple peel) hydrogels reinforced with graphene oxide and bentonite were prepared as efficient adsorbents for methylene blue (MB). The structure and morphology of the prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). Introducing graphene oxide and bentonite into the hydrogels evidently enhanced the thermal stability, swelling ability and MB adsorption capacity. The effects of initial concentration of MB, pH, contact time and temperature on MB adsorption capacity of the prepared hydrogels were investigated. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Langmuir isotherm model well, respectively. After introducing graphene oxide and bentonite into the hydrogels, the maximum adsorption capacity calculated from the Langmuir isotherm model reached 172.14 mg/g at 30 °C, obviously higher than the hydrogels prepared without these additions (83.33 mg/g). Furthermore, all the prepared hydrogels also displayed good reusability for the efficient removal of MB. Consequently, the prepared hydrogels could be served as eco-friendly, stable, efficient and reusable adsorbents for anionic dyes in wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

MHD thermal instabilities in cool inhomogeneous atmospheres

NASA Technical Reports Server (NTRS)

Bodo, G.; Ferrari, A.; Massaglia, S.; Rosner, R.

1983-01-01

The formation of a coronal state in a stellar atmosphere is investigated. A numerical code is used to study the effects of atmospheric gradients and finite loop dimension on the scale of unstable perturbations, solving for oscillatory perturbations as eigenfunctions of a boundary value problem. The atmosphere is considered as initially isothermal, with density and pressure having scale heights fixed by the hydrostatic equations. Joule mode instability is found to be an efficient mechanism for current filamentation and subsequent heating in initially cool atmospheres. This instability is mainly effective at the top of magnetic loops and is not suppressed by thermal conduction.

In the Footsteps of Irving Langmuir: Physical Chemistry in Service of Society

NASA Astrophysics Data System (ADS)

Carter, Emily

The approach that Irving Langmuir took during his scientific career in industry at General Electric exemplifies the best that we chemical physicists/physical chemists can offer the world. His name is associated with very fundamental concepts and phenomena (e.g., the Langmuir isotherm, Langmuir-Blodgett films) along with practical inventions (e.g., the Langmuir probe, Langmuir trough). He worked at the interface of physics, chemistry, and engineering, with much of his important work devoted to understanding surface and interface phenomena. I have - unintentionally - followed in his footsteps, trained as a physical chemist who now leads the engineering school at Princeton. In this talk, I will give examples from my research as to how fundamental physical chemistry techniques and concepts - based largely on quantum mechanics - can be harnessed to help the world transition to a sustainable energy future. In the footsteps of Irving, surface and interfacial phenomena will figure prominently in the examples chosen.

Mach 1 oxidation of thoriated nickel chromium at 1204 C /2200 F/.

NASA Technical Reports Server (NTRS)

Lowell, C. E.; Sanders, W. A.

1972-01-01

Electropolished and ground samples of TD-NiCr were exposed to a 1-atm, Mach 1 gas stream at 1204 C for times up to 50 hr. The samples were subjected to both cyclic and isothermal exposure. Weight change, metal loss, X-ray diffraction, metallographic, and electron microprobe analyses were performed. Neither surface preparation nor cyclic-against-isothermal-exposure conditions had a strong effect on the oxidation behavior of the alloy. Initially, a Cr2O3 layer was formed whose volatilization resulted in a very rapid loss of metal - more than 40 microns in the first hour. At about 1 hr, the Cr2O3 layer broke down and NiO began to cover the surface. By 5 hr, the NiO had covered the surface and the rate of loss slowed. The rate-controlling step was diffusion of Cr through NiO.

Adsorption of anionic and cationic dyes on activated carbon from aqueous solutions: equilibrium and kinetics.

PubMed

Rodríguez, Araceli; García, Juan; Ovejero, Gabriel; Mestanza, María

2009-12-30

Activated carbon was utilized as adsorbent to remove anionic dye, Orange II (OII), and cationic dye, Methylene blue (MB), from aqueous solutions by adsorption. Batch experiments were conducted to study the effects of temperature (30-65 degrees C), initial concentration of adsorbate (300-500 mg L(-1)) and pH (3.0-9.0) on dyes adsorption. Equilibrium adsorption isotherms and kinetics were investigated. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Toth and Redlich-Peterson models. The kinetic data obtained with different carbon mass were analyzed using a pseudo-first order, pseudo-second order, intraparticle diffusion, Bangham and Chien-Clayton equations. The best results were achieved with the Langmuir isotherm equilibrium model and with the pseudo-second order kinetic model. The activated carbon was found to be very effective as adsorbent for MB and OII from aqueous solutions.

Evaluation of Two Loop-mediated Isothermal Amplification Methods for the Detection of Salmonella Enteritidis and Listeria Monocytogenes in Artificially Contaminated Ready-to-Eat Fresh Produce

PubMed Central

Birmpa, Angeliki; Kalogeropoulos, Konstantinos; Kokkinos, Petros

2015-01-01

In the present study, the effectiveness of two loop-mediated isothermal amplification (LAMP) assays was evaluated. Samples of romaine lettuce, strawberries, cherry tomatoes, green onions and sour berries were inoculated with known dilutions (100-108 CFU/g of produce) of S. Enteritidis and L. monocytogenes. With LAMP, assay pathogens can be detected in less than 60 min. The limits of detection of S. Enteritidis and L. monocytogenes depended on the food sample tested and on the presence of enrichment step. After enrichment steps, all food samples were found positive even at low initial pathogen levels. The developed LAMP, assays, are expected to become a valuable, robust, innovative, powerful, cheap and fast monitoring tool, which can be extensively used for routine analysis, and screening of contaminated foods by the food industry and the Public Food Health Authorities. PMID:27800413

Investigating co-combustion characteristics of bamboo and wood.

PubMed

Liang, Fang; Wang, Ruijuan; Jiang, Changle; Yang, Xiaomeng; Zhang, Tao; Hu, Wanhe; Mi, Bingbing; Liu, Zhijia

2017-11-01

To investigate co-combustion characteristics of bamboo and wood, moso bamboo and masson pine were torrefied and mixed with different blend ratios. The combustion process was examined by thermogravimetric analyzer (TGA). The results showed the combustion process of samples included volatile emission and oxidation combustion as well as char combustion. The main mass loss of biomass blends occurred at volatile emission and oxidation combustion stage, while that of torrefied biomass occurred at char combustion stage. With the increase of bamboo content, characteristic temperatures decreased. Compared with untreated biomass, torrefied biomass had a higher initial and burnout temperature. With the increase of heating rates, combustion process of samples shifted to higher temperatures. Compared with non-isothermal models, activation energy obtained from isothermal model was lower. The result is helpful to promote development of co-combustion of bamboo and masson pine wastes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Apiaceae Family Plants as Low-Cost Adsorbents for the Removal of Lead Ion from Water Environment

NASA Astrophysics Data System (ADS)

Boontham, W.; Babel, S.

2017-06-01

Adsorbents prepared from the three selected plants from Apiaceae famaily commonly known as parsley, coriander and culantro were observed to remove lead from aqueous solutions. Batch experiments were conducted to study the effect of dosage, pH, contact time and agitation speed at 10 mg L-1 initial Pb(II) concentration. Results revealed that three selected plants showed high adsorption capacity for removal of lead from aqueous solutions. The maximum biosorption of Pb2+ was found to be more than 97% with 1.0 g/l dosage for all three adsorbents under optimum pH of 3-5. The adsorption equilibrium was established after about 1 hr. The equilibrium adsorption capacity of parsley and coriander were found to fit well with the Langmuir isotherm whereas the Freundlich isotherm was better fit for culantro. The studies showed that the adsorbents can be used for removing lead ions from contaminated waters.

Low-cycle thermal fatigue

NASA Technical Reports Server (NTRS)

Halford, G. R.

1986-01-01

A state-of-the-art review is presented of the field of thermal fatigue. Following a brief historical review, the concept is developed that thermal fatigue can be viewed as processes of unbalanced deformation and cracking. The unbalances refer to dissimilar mechanisms occurring in opposing halves of thermal fatigue loading and unloading cycles. Extensive data summaries are presented and results are interpreted in terms of the unbalanced processes involved. Both crack initiation and crack propagation results are summarized. Testing techniques are reviewed, and considerable discussion is given to a technique for thermal fatigue simulation, known as the bithermal fatigue test. Attention is given to the use of isothermal life prediction methods for the prediction of thermal fatigue lives. Shortcomings of isothermally-based life prediction methods are pointed out. Several examples of analyses and thermal fatigue life predictions of high technology structural components are presented. Finally, numerous dos and don'ts relative to design against thermal fatigue are presented.

Chlorinated phenol removal from aqueous media by tea (Camellia sinensis) leaf waste tailored activated carbon

NASA Astrophysics Data System (ADS)

Joseph, C. G.; Anisuzzaman, S. M.; Daud, W. M. A. W.; Krishnaiah, D.; Ng, K. A.

2017-06-01

In this study, activated carbons (ACs) wereprepared from tea leaves by using a two-stage self-generated atmosphere method. The process was done by semi-carbonizing the precursor at 300 °C for 1 h, followed by the impregnation of the resulting char at 85 °C for 4 h and finally activation at 500 °C for 2 h. The semi-carbonised samples were impregnated with different ratios of zinc chloride (ZnCl2) and their physicochemical effect was studied. The prepared ACs underwent several aspects of both, chemical and physical characterizations, such as the percentage of yield, moisture content, ash content, pH, porosity, adsorption capacity of 2,4-dichlorophenol (2,4-DCP), surface area, porosity, morphology and surface chemistry studies. It was found that sample AC2, with an impregnation ratio of 2:1 was the best AC produced in this study. The maximum Brunauer, Emmett and Teller surface area of AC2 was found to be 695 m2/g. Langmuir, Freundlich and Temkin isotherm models were used to examine the experimental isotherms while the kinetic data was analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The 2,4-DCP adsorption isotherm results complied well to the Langmuir isotherm for the equilibrium data while the adsorption kinetic data fitted well to the pseudo-second order model, indicating that chemisorption by valency forces via the sharing (covalent bond) or exchanging of electrons between the AC and the 2,4-DCP molecules were mainly responsible for the adsorption process. From these findings, it is concluded that tea leaves can be used as a low cost precursor for the removal of 2,4-DCP in aqueous medium.

Impact of Sequential Ammonia Fiber Expansion (AFEX) Pretreatment and Pelletization on the Moisture Sorption Properties of Corn Stover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonner, Ian J.; Thompson, David N.; Teymouri, Farzaneh

Combining ammonia fiber expansion (AFEX™) pretreatment with a depot processing facility is a promising option for delivering high-value densified biomass to the emerging bioenergy industry. However, because the pretreatment process results in a high moisture material unsuitable for pelleting or storage (40% wet basis), the biomass must be immediately dried. If AFEX pretreatment results in a material that is difficult to dry, the economics of this already costly operation would be at risk. This work tests the nature of moisture sorption isotherms and thin-layer drying behavior of corn (Zea mays L.) stover at 20°C to 60°C before and after sequentialmore » AFEX pretreatment and pelletization to determine whether any negative impacts to material drying or storage may result from the AFEX process. The equilibrium moisture content to equilibrium relative humidity relationship for each of the materials was determined using dynamic vapor sorption isotherms and modeled with modified Chung-Pfost, modified Halsey, and modified Henderson temperature-dependent models as well as the Double Log Polynomial (DLP), Peleg, and Guggenheim Anderson de Boer (GAB) temperature-independent models. Drying kinetics were quantified under thin-layer laboratory testing and modeled using the Modified Page's equation. Water activity isotherms for non-pelleted biomass were best modeled with the Peleg temperature-independent equation while isotherms for the pelleted biomass were best modeled with the Double Log Polynomial equation. Thin-layer drying results were accurately modeled with the Modified Page's equation. The results of this work indicate that AFEX pretreatment results in drying properties more favorable than or equal to that of raw corn stover, and pellets of superior physical stability in storage.« less

On the effect of Lyman α trapping during the initial collapse of massive black hole seeds

NASA Astrophysics Data System (ADS)

Ge, Qi; Wise, John H.

2017-12-01

One viable seeding mechanism for supermassive black holes is the direct gaseous collapse route in pre-galactic dark matter haloes, producing objects on the order of 104-106 M⊙. These events occur when the gas is prevented from cooling below 104 K that requires a metal-free and relatively H2-free medium. The initial collapse cools through atomic hydrogen transitions, but the gas becomes optically thick to the cooling radiation at high densities. We explore the effects of Lyman α trapping in such a collapsing system with a suite of Monte Carlo radiation transport calculations in uniform density and isotropic cases that are based from a cosmological simulation. Our method includes both non-coherent scattering and two-photon line cooling. We find that Lyman α radiation is marginally trapped in the parsec-scale gravitationally unstable central cloud, allowing the temperature to increase to 50 000 K at a number density of 3 × 104 cm-3 and increasing the Jeans mass by a factor of 5. The effective equation of state changes from isothermal at low densities to have an adiabatic index of 4/3 around the temperature maximum and then slowly retreats back to isothermal at higher densities. Our results suggest that Lyman α trapping delays the initial collapse by raising the Jeans mass. Afterward the high-density core cools back to 104 K that is surrounded by a warm envelope whose inward pressure may alter the fragmentation scales at high densities.

Kinetic evaluation of chromium(VI) sorption by water lettuce (Pistia).

PubMed

Chakraborty, Rupa; Karmakar, Sukalpa; Mukherjee, Somnath; Kumar, Sunil

2014-01-01

An investigation was performed to evaluate the uptake capacity of Pistia in living condition for adsorptive removal of chromium(VI) from spiked solution for examining a remedial measure for disposal of chrome-laden wastewater in an urban wetland system. Kinetics results show about 78% removal was achieved for 3 mg/L initial concentration of Cr(VI). Experimental data showed that the root portion absorbed more Cr(VI) (28.54 μg/g) compared to accumulation in leaf (5.73 μg/g). It was also noted that the plant could effectively remove Cr(VI) from the solution with minor damage up to an initial Cr(VI) concentration of 3 mg/L, for which the adsorption isotherm studies were conducted. The maximum uptake capacity of the plant was recorded as 0.05 mg/g of Cr(VI) at the equilibrium level after a contact period of 7 days for an initial concentration of 8 mg /L, although severe physiological damage occurred. The experimental results were plotted in Langmuir and Freundlich isotherm models and both were found to be well fitted (r(2) = 0.979 and r(2) = 0.974 respectively). The high value of n (2.16) reveals a strong bond between the plant root and dissolved Cr(VI), which favours the adsorption process. The order of the reaction was also examined on the basis of uptake capacity and it was found that the second order model fitted best.

Hydrodynamic equations for electrons in graphene obtained from the maximum entropy principle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barletti, Luigi, E-mail: luigi.barletti@unifi.it

2014-08-15

The maximum entropy principle is applied to the formal derivation of isothermal, Euler-like equations for semiclassical fermions (electrons and holes) in graphene. After proving general mathematical properties of the equations so obtained, their asymptotic form corresponding to significant physical regimes is investigated. In particular, the diffusive regime, the Maxwell-Boltzmann regime (high temperature), the collimation regime and the degenerate gas limit (vanishing temperature) are considered.

Pressure resistance of copper benzene-1,3,5-tricarboxylate - carbon aerogel composites

NASA Astrophysics Data System (ADS)

Domán, Andrea; Nagy, Balázs; Nichele, Laura P.; Srankó, Dávid; Madarász, János; László, Krisztina

2018-03-01

The protective effect of a resorcinol - formaldehyde based carbon aerogel (CA) support was compared in two different forms of the hybrid made of copper benzene-1,3,5-tricarboxilate (HKUST-1) and CA. HKUST-1:CA with identical mass ratio (1:1). HKUST-1+CAis a physical mixture while in HKUST-1@CA the metal organic framework (MOF) crystals were grown on CA under solvothermal conditions. The effect of water vapour and the external pressure (25-200 bar) was investigated. TG/DTG data show that the prehistory of the samples has a strong influence on their thermal behaviour and nitrogen data suggest that part of the MOF grows in the wider pores of the HKUST-1@CA sample. Although there are no dramatic differences in the water adsorption isotherms, the physical mixture is slightly more proficient. In dry samples under compression the crystalline structure of the free HKUST-1 is well conserved. The nanoscale structure of the hybrids is sensitive to applied pressure and formation of mesopores of wide size distribution occurs. No significant difference was found between the corresponding CH4 adsorption isotherms of the composite samples, either in the as-prepared samples or after compression at 100 bar. After being exposed to high external pressure the CH4 uptake seems to be governed by the MOF.

Excision Repair-Initiated Enzyme-Assisted Bicyclic Cascade Signal Amplification for Ultrasensitive Detection of Uracil-DNA Glycosylase.

PubMed

Wang, Li-Juan; Ren, Ming; Zhang, Qianyi; Tang, Bo; Zhang, Chun-Yang

2017-04-18

Uracil-DNA glycosylase (UDG) is an important base excision repair (BER) enzyme responsible for the repair of uracil-induced DNA lesion and the maintenance of genomic integrity, while the aberrant expression of UDG is associated with a variety of cancers. Thus, the accurate detection of UDG activity is essential to biomedical research and clinical diagnosis. Here, we develop a fluorescent method for ultrasensitive detection of UDG activity using excision repair-initiated enzyme-assisted bicyclic cascade signal amplification. This assay involves (1) UDG-actuated uracil-excision repair, (2) excision repair-initiated nicking enzyme-mediated isothermal exponential amplification, (3) ribonuclease H (RNase H)-induced hydrolysis of signal probes for generating fluorescence signal. The presence of UDG enables the removal of uracil from U·A pairs and generates an apurinic/apyrimidinic (AP) site. Endonuclease IV (Endo IV) subsequently cleaves the AP site, resulting in the break of DNA substrate. The cleaved DNA substrate functions as both a primer and a template to initiate isothermal exponential amplification, producing a large number of triggers. The resultant trigger may selectively hybridize with the signal probe which is modified with FAM and BHQ1, forming a RNA-DNA heterogeneous duplex. The subsequent hydrolysis of RNA-DNA duplex by RNase H leads to the generation of fluorescence signal. This assay exhibits ultrahigh sensitivity with a detection limit of 0.0001 U/mL, and it can even measure UDG activity at the single-cell level. Moreover, this method can be applied for the measurement of kinetic parameters and the screening of inhibitors, thereby providing a powerful tool for DNA repair enzyme-related biomedical research and clinical diagnosis.

Development and Initial Results of a Low Cost, Disposable, Point-of-Care Testing Device for Pathogen Detection

PubMed Central

Dugan, Lawrence C.; Baker, Brian R.; Hall, Sara B.; Ebert, Katja; Mioulet, Valerie; Madi, Mikidache; King, Donald P.

2011-01-01

Development of small footprint, disposable, fast, and inexpensive devices for pathogen detection in the field and clinic would benefit human and veterinary medicine by allowing evidence-based responses to future out breaks. We designed and tested an integrated nucleic acid extraction and amplification device employing a loop-mediated isothermal amplification (LAMP) or reverse transcriptase-LAMP assay. Our system provides a screening tool with polymerase-chain-reaction-level sensitivity and specificity for outbreak detection, response, and recovery. Time to result is ~90 min. The device utilizes a swab that collects sample and then transfers it to a disc of cellulose-based nucleic acid binding paper. The disc is positioned within a disposable containment tube with a manual loading port. In order to test for the presence of target pathogens, LAMP reagents are loaded through the tube’s port into contact with the sample containing cellulose disc. The reagents then are isothermally heated to 63°C for ~1 h to achieve sequence-specific target nucleic acid amplification. Due to the presence of a colorimetric dye, amplification induces visible color change in the reagents from purple to blue. As initial demonstrations, we detected methicillin resistant Staphylococcus aureus genomic DNA, as well as recombinant and live foot-and-mouth disease virus. PMID:21342806

A novel biochar derived from cauliflower (Brassica oleracea L.) roots could remove norfloxacin and chlortetracycline efficiently.

PubMed

Qin, Tingting; Wang, Zhaowei; Xie, Xiaoyun; Xie, Chaoran; Zhu, Junmin; Li, Yan

2017-12-01

The biochar was prepared by pyrolyzing the roots of cauliflowers, at a temperature of 500 °C under oxygen-limited conditions. The structure and characteristics of the biochar were examined using scanning electron microscopy, an energy dispersive spectrometer, a zeta potential analyzer, and Fourier transform infrared spectroscopy. The effects of the temperature, the initial pH, antibiotic concentration, and contact time on the adsorption of norfloxacin (NOR) and chlortetracycline (CTC) onto the biochar were investigated. The adsorption kinetics of NOR and CTC onto the biochar followed the pseudo-second-order kinetic and intra-particle diffusion models. The adsorption isotherm experimental data were well fitted to the Langmuir and Freundlich isotherm models. The maximum adsorption capacities of NOR and CTC were 31.15 and 81.30 mg/g, respectively. There was little difference between the effects of initial solution pH (4.0-10.0) on the adsorption of NOR or CTC onto the biochar because of the buffering effect. The biochar could remove NOR and CTC efficiently in aqueous solutions because of its large specific surface area, abundant surface functional groups, and particular porous structure. Therefore, it could be used as an excellent adsorbent material because of its low cost and high efficiency and the extensive availability of the raw materials.

Utilization of unconventional lignocellulosic waste biomass for the biosorption of toxic triphenylmethane dye malachite green from aqueous solution.

PubMed

Selvasembian, Rangabhashiyam; P, Balasubramanian

2018-05-12

Biosorption potential of novel lignocellulosic biosorbents Musa sp. peel (MSP) and Aegle marmelos shell (AMS) was investigated for the removal of toxic triphenylmethane dye malachite green (MG), from aqueous solution. Batch experiments were performed to study the biosorption characteristics of malachite green onto lignocellulosic biosorbents as a function of initial solution pH, initial malachite green concentration, biosorbents dosage, and temperature. Biosorption equilibrium data were fitted to two and three parameters isotherm models. Three-parameter isotherm models better described the equilibrium data. The maximum monolayer biosorption capacities obtained using the Langmuir model for MG removal using MSP and AMS was 47.61 and 18.86 mg/g, respectively. The biosorption kinetic data were analyzed using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The pseudo-second-order kinetic model best fitted the experimental data, indicated the MG biosorption using MSP and AMS as chemisorption process. The removal of MG using AMS was found as highly dependent on the process temperature. The removal efficiency of MG showed declined effect at the higher concentrations of NaCl and CaCl 2 . The regeneration test of the biosorbents toward MG removal was successful up to three cycles.

Adsorption of malachite green by magnetic litchi pericarps: A response surface methodology investigation.

PubMed

Zheng, Hao; Qi, Jinqiu; Jiang, Ruixue; Gao, Yan; Li, Xiaochen

2015-10-01

In this work, we synthesized a novel magnetic adsorbent containing litchi pericarps, denoted as MLP, for the removal of malachite green (MG) from solution. The factors influencing MG adsorption, such as contact time, adsorbent dosage, and initial dye concentration, were optimized using the Box-Behnken response surface methodology (RSM). The adsorption isotherms as well as the kinetics and thermodynamics of the adsorption of MG onto MLP are discussed. The results showed that MLP has a maximum adsorption efficiency of 99.5% when the temperature, pH, contact time, adsorbent dosage, and initial MG concentration were optimally set as 25 °C, 6.0, 66.69 min, 5.14 g/L, and 150 mg/L, respectively. The best model to describe this process is the Langmuir isotherm, with the maximum adsorption capacity being 70.42 mg/g. In addition, the kinetics of MG adsorption onto MLP followed a pseudo-second-order model; moreover, thermodynamic analysis suggested that MG adsorption onto MLP is spontaneous and endothermic. Finally, it was found that the new magnetic adsorbent can be separated easily and rapidly from mixed solutions in the presence of an external magnetic field. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isothermal Damage and Fatigue Behavior of SCS-6/Timetal 21S [0/90](Sub S) Composite at 650 Deg C

NASA Technical Reports Server (NTRS)

Castelli, Michael G.

1994-01-01

The isothermal fatigue damage and life behaviors of SCS-6/Timetal 21S (0/90)s were investigated at 650 C. Strain ratcheting and degradation of the composite's static elastic modulus were carefully monitored as functions of cycles to indicate damage progression. Extensive fractographic and metallographic analyses were conducted to determine damage/failure mechanisms. Resulting fatigue lives show considerable reductions in comparison to (0) reinforced titanium matrix composites subjected to comparable conditions. Notable stiffness degradations were found to occur after the first cycle of loading, even at relatively low maximum stress levels, where cyclic lives are greater than 25,000 cycles. This was attributed to the extremely weak fiber/matrix bond which fails under relatively low transverse loads. Stiffness degradations incurred on first cycle loadings and degradations thereafter were found to increase with increasing maximum stress. Environmental effects associated with oxidation of the (90) fiber interfaces clearly played a role in the damage mechanisms as fracture surfaces revealed environment assisted matrix cracking along the (90) fibers. Metallographic analysis indicated that all observable matrix fatigue cracks initiated at the (90) fiber/matrix interfaces. Global de-bonding in the loading direction was found along the (90) fibers. No surface initiated cracks were evident and minimal if any (0) fiber cracking was visible.

Removal of dieldrin from aqueous solution by a novel triolein-embedded composite adsorbent.

PubMed

Ru, Jia; Liu, Huijuan; Qu, Jiuhui; Wang, Aimin; Dai, Ruihua

2007-03-06

In this study, a novel triolein-embedded activated carbon composite adsorbent (CA-T) was prepared and applied for the adsorption and removal of dieldrin from aqueous systems. Experiments were carried out to investigate the adsorption behavior of dieldrin on CA-T, including adsorption isotherms, adsorption kinetics, the influence of initial concentration, temperature, shaking speed, pH and the addition of humic acid (HA) on adsorption. The adsorption isotherms accorded with Freundlich equation. Three kinetics models, including pseudo-first-order, pseudo-second-order and intraparticle diffusion models, were used to fit the experimental data. By comparing the correlation coefficients, it was found that both pseudo-second-order and intraparticle diffusion models were used to well describe the adsorption of dieldrin on CA-T. The addition of HA had little effect on dieldrin adsorption by CA-T. Results indicated that CA-T appeared to be a promising adsorbent for removing lipophilic dieldrin in trace amount, which was advantageous over pure granular activated carbon (GAC). The adsorption rate increased with increasing shaking speed, initial concentration and temperature, and remained almost unchanged in the pH range of 4-8. Thermodynamic calculations indicated that the adsorption reaction was spontaneous with a high affinity and the adsorption was an endothermic reaction.

Simultaneous adsorption of Cu2+ and Acid fuchsin (AF) from aqueous solutions by CMC/bentonite composite.

PubMed

Gong, Ning; Liu, Yanping; Huang, Ruihua

2018-04-21

Carboxymethyl-chitosan (CMC)/bentonite composite was prepared by the method of membrane-forming, and characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The simultaneous adsorption of Cu 2+ and Acid fuchsin (AF) applying CMC/bentonite composite as an adsorbent in single or binary systems was investigated. The adsorption study was conducted systematically by varying the ratio of CMC to bentonite, adsorbent dosage, initial pH value, initial Cu 2+ (or AF) concentration, contact time and the interaction of two components in binary solutions. The results showed that the presence of Cu 2+ hindered the adsorption of AF, while the presence of AF almost had no influence on the adsorption of Cu 2+ in binary systems. The adsorption data of Cu 2+ and AF were both suitable for Langmuir isotherm model, and the maximum adsorption capacities of CMC/bentonite composite, according to the Langmuir isotherm model were 81.4 mg/g for Cu 2+ and 253.2 mg/g for AF at 298 K. The pseudo-second-order model could better describe the adsorption process of Cu 2+ and AF. Thermodynamic constant values illustrated that the adsorption of Cu 2+ was endothermic, while the adsorption process of AF was exothermic. Copyright © 2018. Published by Elsevier B.V.

Potential immobilized Saccharomyces cerevisiae as heavy metal removal

NASA Astrophysics Data System (ADS)

Raffar, Nur Izzati Abdul; Rahman, Nadhratul Nur Ain Abdul; Alrozi, Rasyidah; Senusi, Faraziehan; Chang, Siu Hua

2015-05-01

Biosorption of copper ion using treated and untreated immobilized Saccharomyces cerevisiae from aqueous solution was investigate in this study. S.cerevisiae has been choosing as biosorbent due to low cost, easy and continuously available from various industries. In this study, the ability of treated and untreated immobilized S.cerevisiae in removing copper ion influence by the effect of pH solution, and initial concentration of copper ion with contact time. Besides, adsorption isotherm and kinetic model also studied. The result indicated that the copper ion uptake on treated and untreated immobilized S.cerevisiae was increased with increasing of contact time and initial concentration of copper ion. The optimum pH for copper ion uptake on untreated and treated immobilized S.cerevisiae at 4 and 6. From the data obtained of copper ion uptake, the adsorption isotherm was fitted well by Freundlich model for treated immobilized S.cerevisiae and Langmuir model for untreated immobilized S.cerevisiae according to high correlation coefficient. Meanwhile, the pseudo second order was described as suitable model present according to high correlation coefficient. Since the application of biosorption process has been received more attention from numerous researchers as a potential process to be applied in the industry, future study will be conducted to investigate the potential of immobilized S.cerevisiae in continuous process.

Adsorptive removal of Cu(II) from aqueous solution and industrial effluent using natural/agricultural wastes.

PubMed

Singha, Biswajit; Das, Sudip Kumar

2013-07-01

The potentiality of low cost natural/agricultural waste biomasses for the removal of Cu(II) ion from aqueous solution has been investigated in batch experiments. The effect of various physico-chemical parameters such as initial pH, initial Cu(II) concentration, adsorbent dosage, contact time and temperature has been studied. The optimum pH for adsorption was found to be 6 for all adsorbents used. Kinetics data were best described by the pseudo-2nd-order model. The experimental data were fitted well with Freundlich and Halsey isotherm models. The diffusion coefficient and sorption energy indicated that the adsorption process was chemical in nature. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated, and it was observed that the adsorption process was spontaneous and endothermic. The mean sorption energy was calculated using Dubinin-Radushkevich isotherm model and it confirmed that the sorption process was chemical in nature. Different active functional groups were identified by FTIR studies which were responsible for Cu(II) ion adsorption process. Application study using electroplating industrial waste water and regeneration experiment of the adsorbent were also investigated. Design procedure for the batch process was also reported. Copyright © 2013 Elsevier B.V. All rights reserved.

Adsorption capacity of Curcuma longa for the removal of basic green 1 dye--equilibrium, kinetics and thermodynamic study.

PubMed

Roopavathi, K V; Shanthakumar, S

2016-09-01

In the present study, Curcuma longa (turmeric plant) was used as an adsorbent to remove Basic Green 1 (BG) dye. Batch study was carried out to evaluate the adsorption potential of C. longa and influencing factors such as pH (4-10), adsorbent dose (0.2-5 g l-1), initial dye concentration (50-250 mg l-1) and temperature (30-50°C) on dye removal were analysed. The characterisation of adsorbent was carried out using fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) method. Isotherm models that included Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich, and kinetic models such as pseudo first order, pseudo second-order, Elovich and intraparticle diffusion models were studied. A maximum removal percentage (82.76%) of BG dye from aqueous solution was obtained with optimum conditions of pH 7, 1g l-1 adsorbent dose and 30°C temperature, for 100 mg l-1 initial dye concentration. The equilibrium and kinetic study revealed that the experimental data fitted suitably the Freundlich isotherm and Pseudo second order kinetic model. Thermodynamic analysis proved that adsorption system in this study was spontaneous, feasible and endothermic in nature.

Isotherm investigation for the sorption of fluoride onto Bio-F: comparison of linear and non-linear regression method

NASA Astrophysics Data System (ADS)

Yadav, Manish; Singh, Nitin Kumar

2017-12-01

A comparison of the linear and non-linear regression method in selecting the optimum isotherm among three most commonly used adsorption isotherms (Langmuir, Freundlich, and Redlich-Peterson) was made to the experimental data of fluoride (F) sorption onto Bio-F at a solution temperature of 30 ± 1 °C. The coefficient of correlation (r2) was used to select the best theoretical isotherm among the investigated ones. A total of four Langmuir linear equations were discussed and out of which linear form of most popular Langmuir-1 and Langmuir-2 showed the higher coefficient of determination (0.976 and 0.989) as compared to other Langmuir linear equations. Freundlich and Redlich-Peterson isotherms showed a better fit to the experimental data in linear least-square method, while in non-linear method Redlich-Peterson isotherm equations showed the best fit to the tested data set. The present study showed that the non-linear method could be a better way to obtain the isotherm parameters and represent the most suitable isotherm. Redlich-Peterson isotherm was found to be the best representative (r2 = 0.999) for this sorption system. It is also observed that the values of β are not close to unity, which means the isotherms are approaching the Freundlich but not the Langmuir isotherm.

Development and Exploration of the Core-Corona Model of Imploding Plasma Loads.

DTIC Science & Technology

1980-07-01

cal relaxation processes can maintain an isothermal system . The final constraint in the original core-corona model equations was that of quasi-static...on the energy balance. The detailed physics of these upgrades and their improvement of the quantitative modeling of the system are discussed in the...participate in lengthening the radiaton pulse. 18 If such motion is favored in these systems , the impact on the radiation pulse length could be

Hardness of H13 Tool Steel After Non-isothermal Tempering

NASA Astrophysics Data System (ADS)

Nelson, E.; Kohli, A.; Poirier, D. R.

2018-04-01

A direct method to calculate the tempering response of a tool steel (H13) that exhibits secondary hardening is presented. Based on the traditional method of presenting tempering response in terms of isothermal tempering, we show that the tempering response for a steel undergoing a non-isothermal tempering schedule can be predicted. Experiments comprised (1) isothermal tempering, (2) non-isothermal tempering pertaining to a relatively slow heating to process-temperature and (3) fast-heating cycles that are relevant to tempering by induction heating. After establishing the tempering response of the steel under simple isothermal conditions, the tempering response can be applied to non-isothermal tempering by using a numerical method to calculate the tempering parameter. Calculated results are verified by the experiments.

Causal implications of viscous damping in compressible fluid flows

PubMed

Jordan; Meyer; Puri

2000-12-01

Classically, a compressible, isothermal, viscous fluid is regarded as a mathematical continuum and its motion is governed by the linearized continuity, Navier-Stokes, and state equations. Unfortunately, solutions of this system are of a diffusive nature and hence do not satisfy causality. However, in the case of a half-space of fluid set to motion by a harmonically vibrating plate the classical equation of motion can, under suitable conditions, be approximated by the damped wave equation. Since this equation is hyperbolic, the resulting solutions satisfy causal requirements. In this work the Laplace transform and other analytical and numerical tools are used to investigate this apparent contradiction. To this end the exact solutions, as well as their special and limiting cases, are found and compared for the two models. The effects of the physical parameters on the solutions and associated quantities are also studied. It is shown that propagating wave fronts are only possible under the hyperbolic model and that the concept of phase speed has different meanings in the two formulations. In addition, discontinuities and shock waves are noted and a physical system is modeled under both formulations. Overall, it is shown that the hyperbolic form gives a more realistic description of the physical problem than does the classical theory. Lastly, a simple mechanical analog is given and connections to viscoelastic fluids are noted. In particular, the research presented here supports the notion that linear compressible, isothermal, viscous fluids can, at least in terms of causality, be better characterized as a type of viscoelastic fluid.

Molecular simulation study of cavity-generated instabilities in the superheated Lennard-Jones liquid

NASA Astrophysics Data System (ADS)

Torabi, Korosh; Corti, David S.

2010-10-01

Previous equilibrium-based density-functional theory (DFT) analyses of cavity formation in the pure component superheated Lennard-Jones (LJ) liquid [S. Punnathanam and D. S. Corti, J. Chem. Phys. 119, 10224 (2003); M. J. Uline and D. S. Corti, Phys. Rev. Lett. 99, 076102 (2007)] revealed that a thermodynamic limit of stability appears in which no liquidlike density profile can develop for cavity radii greater than some critical size (being a function of temperature and bulk density). The existence of these stability limits was also verified using isothermal-isobaric Monte Carlo (MC) simulations. To test the possible relevance of these limits of stability to a dynamically evolving system, one that may be important for homogeneous bubble nucleation, we perform isothermal-isobaric molecular dynamics (MD) simulations in which cavities of different sizes are placed within the superheated LJ liquid. When the impermeable boundary utilized to generate a cavity is removed, the MD simulations show that the cavity collapses and the overall density of the system remains liquidlike, i.e., the system is stable, when the initial cavity radius is below some certain value. On the other hand, when the initial radius is large enough, the cavity expands and the overall density of the system rapidly decreases toward vaporlike densities, i.e., the system is unstable. Unlike the DFT predictions, however, the transition between stability and instability is not infinitely sharp. The fraction of initial configurations that generate an instability (or a phase separation) increases from zero to unity as the initial cavity radius increases over a relatively narrow range of values, which spans the predicted stability limit obtained from equilibrium MC simulations. The simulation results presented here provide initial evidence that the equilibrium-based stability limits predicted in the previous DFT and MC simulation studies may play some role, yet to be fully determined, in the homogeneous nucleation and growth of embryos within metastable fluids.

Terahertz spectroscopy for the isothermal detection of bacterial DNA by magnetic bead-based rolling circle amplification.

PubMed

Yang, Xiang; Yang, Ke; Zhao, Xiang; Lin, Zhongquan; Liu, Zhiyong; Luo, Sha; Zhang, Yang; Wang, Yunxia; Fu, Weiling

2017-12-04

The demand for rapid and sensitive bacterial detection is continuously increasing due to the significant requirements of various applications. In this study, a terahertz (THz) biosensor based on rolling circle amplification (RCA) was developed for the isothermal detection of bacterial DNA. The synthetic bacterium-specific sequence of 16S rDNA hybridized with a padlock probe (PLP) that contains a sequence fully complementary to the target sequence at the 5' and 3' ends. The linear PLP was circularized by ligation to form a circular PLP upon recognition of the target sequence; then the capture probe (CP) immobilized on magnetic beads (MBs) acted as a primer to initialize RCA. As DNA molecules are much less absorptive than water molecules in the THz range, the RCA products on the surface of the MBs cause a significant decrease in THz absorption, which can be sensitively probed by THz spectroscopy. Our results showed that 0.12 fmol of synthetic bacterial DNA and 0.05 ng μL -1 of genomic DNA could be effectively detected using this assay. In addition, the specificity of this strategy was demonstrated by its low signal response to interfering bacteria. The proposed strategy not only represents a new method for the isothermal detection of the target bacterial DNA but also provides a general methodology for sensitive and specific DNA biosensing using THz spectroscopy.

Polyhydroxy glucose functionalized silica for the dehydration of bio-ethanol distillate.

PubMed

Tang, Baokun; Bi, Wentao; Row, Kyung Ho

2014-07-01

Although most of the water in a bio-ethanol fermentation broth can be removed by distillation, a small amount of water remains in the bio-ethanol distillate as the water-ethanol azeotrope. To improve the use of ethanol as a fuel, glucose-modified silica, as an adsorbent, was prepared using a facile method and applied to the dehydration of bio-ethanol distillate. The factors affecting the adsorption capacity of the adsorbent, such as the particle size, initial concentration of water in the samples, adsorption temperature and adsorbent dose, were examined by measuring the adsorption kinetics and equilibrium. The Langmuir, Freundlich and Temkin isotherms were used to evaluate the adsorption efficiency. Of these, the Freundlich and Temkin isotherms showed a good correlation with the experimental data. The Langmuir isotherm showed some deviation from the experimental results, and indicated that adsorption in this case was not a simple monolayer adsorption. The property of the adsorbent was attributed to functionalized silica with many hydroxyl groups on its surface. An examination of the separation factors of water/ethanol revealed the modified silica to have preferential selectivity for water. Compared to activated carbon and silica, glucose-modified silica exhibited higher adsorption capacity for water under the same adsorption conditions. In addition, the glucose-modified silica adsorbent exhibited a relatively constant adsorption capacity for five adsorption/desorption cycles.

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

PubMed

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

2017-12-01

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

FRAGMENTATION AND EVOLUTION OF MOLECULAR CLOUDS. II. THE EFFECT OF DUST HEATING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, Andrea; Evans, Neal J.; Martel, Hugo

2010-02-20

We investigate the effect of heating by luminosity sources in a simulation of clustered star formation. Our heating method involves a simplified continuum radiative transfer method that calculates the dust temperature. The gas temperature is set by the dust temperature. We present the results of four simulations; two simulations assume an isothermal equation of state and the two other simulations include dust heating. We investigate two mass regimes, i.e., 84 M{sub sun} and 671 M{sub sun}, using these two different energetics algorithms. The mass functions for the isothermal simulations and simulations that include dust heating are drastically different. In themore » isothermal simulation, we do not form any objects with masses above 1 M{sub sun}. However, the simulation with dust heating, while missing some of the low-mass objects, forms high-mass objects ({approx}20 M{sub sun}) which have a distribution similar to the Salpeter initial mass function. The envelope density profiles around the stars formed in our simulation match observed values around isolated, low-mass star-forming cores. We find the accretion rates to be highly variable and, on average, increasing with final stellar mass. By including radiative feedback from stars in a cluster-scale simulation, we have determined that it is a very important effect which drastically affects the mass function and yields important insights into the formation of massive stars.« less

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism.

PubMed

Alqadami, Ayoub Abdullah; Naushad, Mu; Alothman, Z A; Ahamad, Tansir

2018-06-06

In the present study, Fe 3 O 4 @AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe 3 O 4 @AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe 3 O 4 @AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe 3 O 4 @AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π-π interaction and hydrogen bonding. The desorption of both dyes from Fe 3 O 4 @AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe 3 O 4 @AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Microstructural evolution and magnetic properties of ultrafine solute-atom particles formed in a Cu75-Ni20-Fe5 alloy on isothermal annealing

NASA Astrophysics Data System (ADS)

Kim, Jun-Seop; Takeda, Mahoto; Bae, Dong-Sik

2016-12-01

Microstructural features strongly affect magnetism in nano-granular magnetic materials. In the present work we have investigated the relationship between the magnetic properties and the self-organized microstructure formed in a Cu75-Ni20-Fe5 alloy comprising ferromagnetic elements and copper atoms. High resolution transmission electron microscopy (HRTEM) observations showed that on isothermal annealing at 873 K, nano-scale solute (Fe,Ni)-rich clusters initially formed with a random distribution in the Cu-rich matrix. Superconducting quantum interference device (SQUID) measurements revealed that these ultrafine solute clusters exhibited super-spinglass and superparamagnetic states. On further isothermal annealing the precipitates evolved to cubic or rectangular ferromagnetic particles and aligned along the <100> directions of the copper-rich matrix. Electron energy-band calculations based on the first-principle Korringa-Kohn-Rostocker (KKR) method were also implemented to investigate both the electronic structure and the magnetic properties of the alloy. Inputting compositions obtained experimentally by scanning transmission electron microscopy-electron dispersive X-ray spectroscopy (STEM-EDS) analysis, the KKR calculation confirmed that ferromagnetic precipitates (of moment 1.07μB per atom) formed after annealing for 2 × 104 min. Magneto-thermogravimetric (MTG) analysis determined with high sensitivity the Curie temperatures and magnetic susceptibility above room temperature of samples containing nano-scale ferromagnetic particles.

Removal of anionic dye Congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent: equilibrium, thermodynamic, kinetics, mechanism and process design.

PubMed

Dawood, Sara; Sen, Tushar Kanti

2012-04-15

Pine cone a natural, low-cost agricultural by-product in Australia has been studied for its potential application as an adsorbent in its raw and hydrochloric acid modified form. Surface study of pine cone and treated pine cone was investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The modification process leads to increases in the specific surface area and decreases mean particle sizes of acid-treated pine cone when compared to raw pine cone biomass. Batch adsorption experiments were performed to remove anionic dye Congo red from aqueous solution. It was found that the extent of Congo red adsorption by both raw pine cone biomass and acid-treated biomass increased with initial dye concentration, contact time, temperature but decreased with increasing solution pH and amount of adsorbent of the system. Overall, kinetic studies showed that the dye adsorption process followed pseudo-second-order kinetics based on pseudo-first-order and intra-particle diffusion models. The different kinetic parameters including rate constant, half-adsorption time, and diffusion coefficient were determined at different physico-chemical conditions. Equilibrium data were best represented by Freundlich isotherm model among Langmuir and Freundlich adsorption isotherm models. It was observed that the adsorption was pH dependent and the maximum adsorption of 32.65 mg/g occurred at pH of 3.55 for an initial dye concentration of 20 ppm by raw pine cone, whereas for acid-treated pine cone the maximum adsorption of 40.19 mg/g for the same experimental conditions. Freundlich constant 'n' also indicated favourable adsorption. Thermodynamic parameters such as ∆G(0), ∆H(0), and ∆S(0) were calculated. A single-stage batch absorber design for the Congo red adsorption onto pine cone biomass also presented based on the Freundlich isotherm model equation. Copyright © 2012 Elsevier Ltd. All rights reserved.

ISOFIT - A PROGRAM FOR FITTING SORPTION ISOTHERMS TO EXPERIMENTAL DATA

EPA Science Inventory

Isotherm expressions are important for describing the partitioning of contaminants in environmental systems. ISOFIT (ISOtherm FItting Tool) is a software program that fits isotherm parameters to experimental data via the minimization of a weighted sum of squared error (WSSE) obje...

Effects of friction and heat conduction on sound propagation in ducts. [analyzing complex aerodynamic noise problems

NASA Technical Reports Server (NTRS)

Huerre, P.; Karamcheti, K.

1976-01-01

The theory of sound propagation is examined in a viscous, heat-conducting fluid, initially at rest and in a uniform state, and contained in a rigid, impermeable duct with isothermal walls. Topics covered include: (1) theoretical formulation of the small amplitude fluctuating motions of a viscous, heat-conducting and compressible fluid; (2) sound propagation in a two dimensional duct; and (3) perturbation study of the inplane modes.

Determining Kinetic Parameters for Isothermal Crystallization of Glasses

NASA Technical Reports Server (NTRS)

Ray, C. S.; Zhang, T.; Reis, S. T.; Brow, R. K.

2006-01-01

Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. These techniques are experimentally simple and quick compared to the isothermal techniques. However, the analytical models used for non-isothermal data analysis, originally developed for describing isothermal transformation kinetics, are fundamentally flawed. The present paper describes a technique for determining the kinetic parameters for isothermal crystallization in glasses, which eliminates most of the common problems that generally make the studies of isothermal crystallization laborious and time consuming. In this technique, the volume fraction of glass that is crystallized as a function of time during an isothermal hold was determined using differential thermal analysis (DTA). The crystallization parameters for the lithium-disilicate (Li2O.2SiO2) model glass were first determined and compared to the same parameters determined by other techniques to establish the accuracy and usefulness of the present technique. This technique was then used to describe the crystallization kinetics of a complex Ca-Sr-Zn-silicate glass developed for sealing solid oxide fuel cells.

Pyrogallol-imprinted polymers with methyl methacrylate via precipitation polymerization

NASA Astrophysics Data System (ADS)

Mehamod, Faizatul Shimal; Othman, Nor Amira; Bulat, Ku Halim Ku; Suah, Faiz Bukhari Mohd

2018-06-01

Molecular simulation techniques are important to study the understanding of chemical and physical properties of any material. Computational modeling is considered as time reducer in finding the best recipes for Molecularly-Imprinted Polymers (MIPs). In this study, Pyrogallol-imprinted polymers (PIP) and non-imprinted polymers (NIPs) were synthesized via precipitation polymerization using Pyrogallol (Py), methyl methacrylate (MMA), divinylbenzene (DVB) as template, functional monomer and cross-linker, respectively. The recipe was according to the results from computational techniques. The synthesized PIP and NIPs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and UV-visible spectroscopy (UV-vis). Studies on adsorption isotherm showed that PIP and NIPs follow Scatchard isotherm models. Sorption kinetic study found that PIP and NIPs follow pseudo-second order which indicates the rate-limiting step is the surface adsorption. The imprinting factor of PIP was determined by selectivity study and showed the value of k >1, which proved that PIP was selective toward Pyrogallol compared to NIP.

Utilization of oil palm biodiesel solid residue as renewable sources for preparation of granular activated carbon by microwave induced KOH activation.

PubMed

Foo, K Y; Hameed, B H

2013-02-01

In this work, preparation of granular activated carbon from oil palm biodiesel solid residue, oil palm shell (PSAC) by microwave assisted KOH activation has been attempted. The physical and chemical properties of PSAC were characterized using scanning electron microscopy, volumetric adsorption analyzer and elemental analysis. The adsorption behavior was examined by performing batch adsorption experiments using methylene blue as dye model compound. Equilibrium data were simulated using the Langmuir, Freundlich and Temkin isotherm models. Kinetic modeling was fitted to the pseudo-first-order, pseudo-second-order and Elovich kinetic models, while the adsorption mechanism was determined using the intraparticle diffusion and Boyd equations. The result was satisfactory fitted to the Langmuir isotherm model with a monolayer adsorption capacity of 343.94mg/g at 30°C. The findings support the potential of oil palm shell for preparation of high surface area activated carbon by microwave assisted KOH activation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Calorimetric evidence for two distinct molecular packing arrangements in stable glasses of indomethacin.

PubMed

Kearns, Kenneth L; Swallen, Stephen F; Ediger, M D; Sun, Ye; Yu, Lian

2009-02-12

Indomethacin glasses of varying stabilities were prepared by physical vapor deposition onto substrates at 265 K. Enthalpy relaxation and the mobility onset temperature were assessed with differential scanning calorimetry (DSC). Quasi-isothermal temperature-modulated DSC was used to measure the reversing heat capacity during annealing above the glass transition temperature Tg. At deposition rates near 8 A/s, scanning DSC shows two enthalpy relaxation peaks and quasi-isothermal DSC shows a two-step change in the reversing heat capacity. We attribute these features to two distinct local packing structures in the vapor-deposited glass, and this interpretation is supported by the strong correlation between the two calorimetric signatures of the glass to liquid transformation. At lower deposition rates, a larger fraction of the sample is prepared in the more stable local packing. The transformation of the vapor-deposited glasses into the supercooled liquid above Tg is exceedingly slow, as much as 4500 times slower than the structural relaxation time of the liquid.

Numerical modeling of physical vapor transport under microgravity conditions: Effect of thermal creep and stress

NASA Technical Reports Server (NTRS)

Mackowski, Daniel W.; Knight, Roy W.

1993-01-01

One of the most promising applications of microgravity (micro-g) environments is the manufacture of exotic and high-quality crystals in closed cylindrical ampoules using physical vapor transport (PVT) processes. The quality enhancements are believed to be due to the absence of buoyant convection in the weightless environment - resulting in diffusion-limited transport of the vapor. In a typical experiment, solid-phase sample material is initially contained at one end of the ampoule. The sample is made to sublime into the vapor phase and deposit onto the opposite end by maintaining the source at an elevated temperature with respect to the deposit. Identification of the physical factors governing both the rates and uniformity of crystal growth, and the optimization of the micro-g technology, will require an accurate modeling of the vapor transport within the ampoule. Previous micro-g modeling efforts have approached the problem from a 'classical' convective/diffusion formulation, in which convection is driven by the action of buoyancy on thermal and solutal density differences. The general conclusion of these works have been that in low gravity environments the effect of buoyancy on vapor transport is negligible, and vapor transport occurs in a diffusion-limited mode. However, it has been recently recognized than in the non-isothermal (and often low total pressure) conditions encountered in ampoules, the commonly-assumed no-slip boundary condition to the differential equations governing fluid motion can be grossly unrepresentative of the actual situation. Specifically, the temperature gradients can give rise to thermal creep flows at the ampoule side walls. In addition, temperature gradients in the vapor itself can, through the action of thermal stress, lead to bulk fluid convection.

Discovery of a novel general anesthetic chemotype using high-throughput screening.

PubMed

McKinstry-Wu, Andrew R; Bu, Weiming; Rai, Ganesha; Lea, Wendy A; Weiser, Brian P; Liang, David F; Simeonov, Anton; Jadhav, Ajit; Maloney, David J; Eckenhoff, Roderic G

2015-02-01

The development of novel anesthetics has historically been a process of combined serendipity and empiricism, with most recent new anesthetics developed via modification of existing anesthetic structures. Using a novel high-throughput screen employing the fluorescent anesthetic 1-aminoanthracene and apoferritin as a surrogate for on-pathway anesthetic protein target(s), we screened a 350,000 compound library for competition with 1-aminoanthracene-apoferritin binding. Hit compounds meeting structural criteria had their binding affinities for apoferritin quantified with isothermal titration calorimetry and were tested for γ-aminobutyric acid type A receptor binding using a flunitrazepam binding assay. Chemotypes with a strong presence in the top 700 and exhibiting activity via isothermal titration calorimetry were selected for medicinal chemistry optimization including testing for anesthetic potency and toxicity in an in vivo Xenopus laevis tadpole assay. Compounds with low toxicity and high potency were tested for anesthetic potency in mice. From an initial chemical library of more than 350,000 compounds, we identified 2,600 compounds that potently inhibited 1-aminoanthracene binding to apoferritin. A subset of compounds chosen by structural criteria (700) was successfully reconfirmed using the initial assay. Based on a strong presence in both the initial and secondary screens the 6-phenylpyridazin-3(2H)-one chemotype was assessed for anesthetic activity in tadpoles. Medicinal chemistry efforts identified four compounds with high potency and low toxicity in tadpoles, two were found to be effective novel anesthetics in mice. The authors demonstrate the first use of a high-throughput screen to successfully identify a novel anesthetic chemotype and show mammalian anesthetic activity for members of that chemotype.

Simple fabrication of reduced graphene oxide -few layer MoS2 nanocomposite for enhanced electrochemical performance in supercapacitors and water purification

NASA Astrophysics Data System (ADS)

Raghu, M. S.; Yogesh Kumar, K.; Rao, Srilatha; Aravinda, T.; Sharma, S. C.; Prashanth, M. K.

2018-05-01

Expelling of heavy metal ions into water resource systems is extremely hazardous to the environment. Adsorption is one of the most cost effective and potential methods to remove the heavy metal ions from the effluents. Therefore, an attempt has been made to study the adsorption of metal particles of Cd and Hg from aqueous solution by using reduced graphene oxide-molybdenum disulphide (rGO-MoS2) nanocomposites as adsorbents. The rGO-MoS2 composites were synthesized by following simple physical methods; which involve the mixing of dispersions of MoS2 and graphene oxide (GO) by sonication, followed by subsequent reduction with hydrazine hydrate. Characterization of the nanocomposites was performed by FESEM, TEM, EDAX, raman spectroscopy, XRD and BET surface area analysis. Electron microscopic images validate the presence of homogeneity in the synthesized nanocomposite. Batch adsorption experiments were used to scrutinizethe effect of an array of parameters like effect of pH, initial concentration of the metal ions, adsorbent dose, and contact time on the adsorption capacity of metal ions on rGO-MoS2 nanocomposites. The thorough examination of adsorbed isotherm and energy demonstrates the best fitting of the adsorption data with the 'Langmuir adsorption isotherm model' and follows the pseudo-second-order kinetic in active condition. The synthesized materials havealso been tested against Gram-positive and Gram-negative bacterial strains and have showcased promising antimicrobial activities. At the same time, the nanocomposites were evaluated for electrochemical performance in supercapacitors. The rGO-MoS2 nanocomposite demonstrates better capacitance (440 Fg-1) at 5 mvs-1 scan rate. The inimitable surface property of MoS2 and good electrical conductivity of rGO results show versatile usage and formidable performance as an adsorbent, antibacterial agent and electrode material for supercapacitors.

Efficient removal of Acid Green 25 dye from wastewater using activated Prunus Dulcis as biosorbent: Batch and column studies.

PubMed

Jain, Suyog N; Gogate, Parag R

2018-03-15

Biosorbent synthesized from dead leaves of Prunus Dulcis with chemical activation during the synthesis was applied for the removal of Acid Green 25 dye from wastewater. The obtained biosorbent was characterized using Brunauer-Emmett-Teller analysis, Fourier transform-infrared spectroscopy and scanning electron microscopy measurements. It was demonstrated that alkali treatment during the synthesis significantly increased surface area of biosorbent from 67.205 to 426.346 m 2 /g. The effect of various operating parameters on dye removal was investigated in batch operation and optimum values of parameters were established as pH of 2, 14 g/L as the dose of natural biosorbent and 6 g/L as the dose of alkali treated biosorbent. Relative error values were determined to check fitting of obtained data to the different kinetic and isotherm models. It was established that pseudo-second order kinetic model and Langmuir isotherm fitted suitably to the obtained batch experimental data. Maximum biosorption capacity values were estimated as 22.68 and 50.79 mg/g for natural biosorbent and for alkali activated Prunus Dulcis, respectively. Adsorption was observed as endothermic and activation energy of 6.22 kJ/mol confirmed physical type of adsorption. Column experiments were also conducted to probe the effectiveness of biosorbent for practical applications in continuous operation. Breakthrough parameters were established by studying the effect of biosorbent height, flow rate of dye solution and initial dye concentration on the extent of dye removal. The maximum biosorption capacity under optimized conditions in the column operation was estimated as 28.57 mg/g. Thomas and Yoon-Nelson models were found to be suitably fitted to obtained column data. Reusability study carried out in batch and continuous column operations confirmed that synthesized biosorbent can be used repeatedly for dye removal from wastewater. Copyright © 2018 Elsevier Ltd. All rights reserved.

Isotope variations in a Sierra Nevada snowpack and their relation to meltwater

USGS Publications Warehouse

Unnikrishna, P.V.; McDonnell, Jeffery J.; Kendall, C.

2002-01-01

Isotopic variations in melting snow are poorly understood. We made weekly measurements at the Central Sierra Snow Laboratory, California, of snow temperature, density, water equivalent and liquid water volume to examine how physical changes within the snowpack govern meltwater ??18O. Snowpack samples were extracted at 0.1 m intervals from ground level to the top of the snowpack profile between December 1991 and April 1992. Approximately 800 mm of precipitation fell during the study period with ??18O values between -21.35 and -4.25???. Corresponding snowpack ??18O ranged from -22.25 to -6.25???. The coefficient of variation of ??18O in snowpack levels decreased from -0.37 to -0.07 from winter to spring, indicating isotopic snowpack homogenization. Meltwater ??18O ranged from -15.30 to -8.05???, with variations of up to 2.95??? observed within a single snowmelt episode, highlighting the need for frequent sampling. Early snowmelt originated in the lower snowpack with higher ??18O through ground heat flux and rainfall. After the snowpack became isothermal, infiltrating snowmelt displaced the higher ??18O liquid in the lower snowpack through a piston flow process. Fractionation analysis using a two-component mixing model on the isothermal snowpack indicated that ??18O in the initial and final half of major snowmelt was 1.30??? lower and 1.45??? higher, respectively, than the value from simple mixing. Mean snowpack ??18O on individual profiling days showed a steady increase from -15.15 to -12.05??? due to removal of lower ??18O snowmelt and addition of higher ??18O rainfall. Results suggest that direct sampling of snowmelt and snow cores should be undertaken to quantify tracer input compositions adequately. The snowmelt sequence also suggests that regimes of early lower ??18O and later higher ??18O melt may be modeled and used in catchment tracing studies. ?? 2002 Elsevier Science B.V. All rights reserved.

Estimating non-isothermal bacterial growth in foods from isothermal experimental data.

PubMed

Corradini, M G; Peleg, M

2005-01-01

To develop a mathematical method to estimate non-isothermal microbial growth curves in foods from experiments performed under isothermal conditions and demonstrate the method's applicability with published growth data. Published isothermal growth curves of Pseudomonas spp. in refrigerated fish at 0-8 degrees C and Escherichia coli 1952 in a nutritional broth at 27.6-36 degrees C were fitted with two different three-parameter 'primary models' and the temperature dependence of their parameters was fitted by ad hoc empirical 'secondary models'. These were used to generate non-isothermal growth curves by solving, numerically, a differential equation derived on the premise that the momentary non-isothermal growth rate is the isothermal rate at the momentary temperature, at a time that corresponds to the momentary growth level of the population. The predicted non-isothermal growth curves were in agreement with the reported experimental ones and, as expected, the quality of the predictions did not depend on the 'primary model' chosen for the calculation. A common type of sigmoid growth curve can be adequately described by three-parameter 'primary models'. At least in the two systems examined, these could be used to predict growth patterns under a variety of continuous and discontinuous non-isothermal temperature profiles. The described mathematical method whenever validated experimentally will enable the simulation of the microbial quality of stored and transported foods under a large variety of existing or contemplated commercial temperature histories.

A physics-based algorithm for real-time simulation of electrosurgery procedures in minimally invasive surgery.

PubMed

Lu, Zhonghua; Arikatla, Venkata S; Han, Zhongqing; Allen, Brian F; De, Suvranu

2014-12-01

High-frequency electricity is used in the majority of surgical interventions. However, modern computer-based training and simulation systems rely on physically unrealistic models that fail to capture the interplay of the electrical, mechanical and thermal properties of biological tissue. We present a real-time and physically realistic simulation of electrosurgery by modelling the electrical, thermal and mechanical properties as three iteratively solved finite element models. To provide subfinite-element graphical rendering of vaporized tissue, a dual-mesh dynamic triangulation algorithm based on isotherms is proposed. The block compressed row storage (BCRS) structure is shown to be critical in allowing computationally efficient changes in the tissue topology due to vaporization. We have demonstrated our physics-based electrosurgery cutting algorithm through various examples. Our matrix manipulation algorithms designed for topology changes have shown low computational cost. Our simulator offers substantially greater physical fidelity compared to previous simulators that use simple geometry-based heat characterization. Copyright © 2013 John Wiley & Sons, Ltd.

Differential continuum damage mechanics models for creep and fatigue of unidirectional metal matrix composites

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Kruch, S.

1991-01-01

Three multiaxial isothermal continuum damage mechanics models for creep, fatigue, and creep/fatigue interaction of a unidirectional metal matrix composite volume element are presented, only one of which will be discussed in depth. Each model is phenomenological and stress based, with varying degrees of complexity to accurately predict the initiation and propagation of intergranular and transgranular defects over a wide range of loading conditions. The development of these models is founded on the definition of an initially transversely isotropic fatigue limit surface, static fracture surface, normalized stress amplitude function and isochronous creep damage failure surface, from which both fatigue and creep damage evolutionary laws can be obtained. The anisotropy of each model is defined through physically meaningful invariants reflecting the local stress and material orientation. All three transversely isotropic models have been shown, when taken to their isotropic limit, to directly simplify to previously developed and validated creep and fatigue continuum damage theories. Results of a nondimensional parametric study illustrate (1) the flexibility of the present formulation when attempting to characterize a large class of composite materials, and (2) its ability to predict anticipated qualitative trends in the fatigue behavior of unidirectional metal matrix composites. Additionally, the potential for the inclusion of various micromechanical effects (e.g., fiber/matrix bond strength, fiber volume fraction, etc.), into the phenomenological anisotropic parameters is noted, as well as a detailed discussion regarding the necessary exploratory and characterization experiments needed to utilize the featured damage theories.

Discovery of a Very Bright and Intrinsically Very Luminous, Strongly Lensed Lyα Emitting Galaxy at z = 2.82 in the BOSS Emission-Line Lens Survey

NASA Astrophysics Data System (ADS)

Marques-Chaves, Rui; Pérez-Fournon, Ismael; Shu, Yiping; Martínez-Navajas, Paloma I.; Bolton, Adam S.; Kochanek, Christopher S.; Oguri, Masamune; Zheng, Zheng; Mao, Shude; Montero-Dorta, Antonio D.; Cornachione, Matthew A.; Brownstein, Joel R.

2017-01-01

We report the discovery of a very bright (r = 20.16), highly magnified, and yet intrinsically very luminous Lyα emitter (LAE) at z=2.82. This system comprises four images in the observer plane with a maximum separation of ˜ 6\\prime\\prime and it is lensed by a z=0.55 massive early-type galaxy. It was initially identified in the Baryon Oscillation Spectroscopic Survey Emission-Line Lens Survey for GALaxy-Lyα EmitteR sYstems survey, and follow-up imaging and spectroscopic observations using the Gran Telescopio Canarias and William Herschel Telescope confirmed the lensing nature of this system. A lens model using a singular isothermal ellipsoid in an external shear field reproduces the main features of the system quite well, yielding an Einstein radius of 2.″95 ± 0.″10, and a total magnification factor for the LAE of 8.8 ± 0.4. This LAE is one of the brightest and most luminous galaxy-galaxy strong lenses known. We present initial imaging and spectroscopy showing the basic physical and morphological properties of this lensed system. Based on observations made with the Gran Telescopio Canarias (GTC) and William Herschel Telescope (WHT), in the Spanish Observatorio del Roque de los Muchachos of the IAC, under Directors Discretionary Time (DDT programs IDs: GTC2016-054 and DDT2016-077).

European Scientific Notes. Volume 35, Number 3,

DTIC Science & Technology

1981-03-31

the distribution of par- fodder to feed the animals. ticulate matter in Icelandic coastal Because of their country’s small size waters. He is studying...however, has the possibil- of the Condensed Matter Division of the ity of depositing the energy required for European Physical Society (EPS) which... Matter Division of the heat energy is deposited at the front of EPS. the slab; isothermal (t ’, 10 s), in which Of xital concern to those present the

Theoretical study of hydrogen absorption-desorption on LaNi3.8Al1.2-xMnx using statistical physics treatment

NASA Astrophysics Data System (ADS)

Bouaziz, Nadia; Ben Manaa, Marwa; Ben Lamine, Abdelmottaleb

2017-11-01

The hydrogen absorption-desorption isotherms on LaNi3.8Al1.2-xMnx alloy at temperature T = 433 K is studied through various theoretical models. The analytical expressions of these models were deduced exploiting the grand canonical ensemble in statistical physics by taking some simplifying hypotheses. Among these models an adequate model which presents a good correlation with the experimental curves has been selected. The physicochemical parameters intervening in the absorption-desorption processes and involved in the model expressions could be directly deduced from the experimental isotherms by numerical simulation. Six parameters of the model are adjusted, namely the numbers of hydrogen atoms per site n1 and n2, the receptor site densities N1m and N2m, and the energetic parameters P1 and P2. The behaviors of these parameters are discussed in relation with absorption and desorption processes to better understand and compare these phenomena. Thanks to the energetic parameters, we calculated the sorption energies which are typically ranged between 266 and 269.4 KJ/mol for absorption process and between 267 and 269.5 KJ/mol for desorption process comparable to usual chemical bond energies. Using the adopted model expression, the thermodynamic potential functions which govern the absorption/desorption process such as internal energy Eint, free enthalpy of Gibbs G and entropy Sa are derived.

A survey of X-ray line emission from the supernova remnant Puppis A

NASA Technical Reports Server (NTRS)

Winkler, P. F.; Clark, G. W.; Markert, T. H.; Kalata, K.; Schnopper, H. W.; Canizares, C. R.

1981-01-01

Initial results from the first high-resolution study of the X-ray spectrum of a supernova remnant are reported. The spectrum of Puppis A between 500 and 1100 eV has been surveyed with the Focal Plane Crystal Spectrometer on the Einstein Observatory and the flux in eight lines and three line blends from various transitions of highly ionized nitrogen, oxygen, neon, and iron has been measured. The spectrum resembles that of active regions in the solar corona, but the neon lines seem enhanced relative to the oxygen lines, and both are enhanced relative to iron. The observed line strengths serve as diagnostics of the physical conditions in the emitting material. Without a priori assumptions, the ionization temperatures of O (2.2 million K) and Ne (4 million K) and the dominant ionization stage of Fe (Fe XVII) are deduced. Isothermal equilibrium plasmas or homogeneous nonequilibrium plasmas as descriptions of the source are ruled out. It is concluded that Puppis A must contain plasma over a temperature range 2-million to 5-million K with an intervening absorption column of 4 x 10 to the 21st/sq cm.

On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons

NASA Astrophysics Data System (ADS)

Mitropoulos, A. C.; Stefanopoulos, K. L.; Favvas, E. P.; Vansant, E.; Hankins, N. P.

2015-06-01

Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of ‘ink-bottle’ pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary.

SPECIAL ISSUE DEVOTED TO THE 80TH ANNIVERSARY OF ACADEMICIAN N G BASOV'S BIRTH: Structural rearrangements in the aqueous phase of cell suspensions and protein solutions induced by a light-oxygen effect

NASA Astrophysics Data System (ADS)

Zakharov, S. D.; Ivanov, Andrei V.; Wolf, E. B.; Danilov, V. P.; Murina, T. M.; Nguen, K. T.; Novikov, E. G.; Panasenko, N. A.; Perov, S. N.; Skopinov, S. A.; Timofeev, Yu P.

2003-02-01

Temperature-dependent transient processes initiated by a direct photogeneration of singlet oxygen in suspensions of human erythrocytes and solutions of serum albumin are studied. The processes appear as anomalous jumps in the temperature dependences of the deformability coefficient of erythrocytes and the refractive index of the extracellular medium and protein solution. In the temperature regions of anomalous jumps, cells and proteins transfer to a metastable state of a lower activity, but they can be isothermally photoreactivated. Simultaneously, a reversible rearrangement of the aqueous phase occurs near the cell and protein surfaces, accompanied by the formation of an extended corona (hydrogel). The transient processes are interpreted as phase transitions in the membrane of erythrocytes and conformation transitions in proteins. The interaction between erythrocytes and albumin via hydrogel is discovered (hydro-conformational interaction). A qualitative physical model of the early stages of the light-oxygen effect is proposed, in which collective magnetic interactions between the electron spins of oxygen molecules and the nuclear magnetic moments of protons in H2O molecules play a dominant role.

Thermal Desorption Analysis of Effective Specific Soil Surface Area

NASA Astrophysics Data System (ADS)

Smagin, A. V.; Bashina, A. S.; Klyueva, V. V.; Kubareva, A. V.

2017-12-01

A new method of assessing the effective specific surface area based on the successive thermal desorption of water vapor at different temperature stages of sample drying is analyzed in comparison with the conventional static adsorption method using a representative set of soil samples of different genesis and degree of dispersion. The theory of the method uses the fundamental relationship between the thermodynamic water potential (Ψ) and the absolute temperature of drying ( T): Ψ = Q - aT, where Q is the specific heat of vaporization, and a is the physically based parameter related to the initial temperature and relative humidity of the air in the external thermodynamic reservoir (laboratory). From gravimetric data on the mass fraction of water ( W) and the Ψ value, Polyanyi potential curves ( W(Ψ)) for the studied samples are plotted. Water sorption isotherms are then calculated, from which the capacity of monolayer and the target effective specific surface area are determined using the BET theory. Comparative analysis shows that the new method well agrees with the conventional estimation of the degree of dispersion by the BET and Kutilek methods in a wide range of specific surface area values between 10 and 250 m2/g.

Removal of Emulsified Oil from Water by Fruiting Bodies of Macro-Fungus (Auricularia polytricha)

PubMed Central

Yang, Xunan; Guo, Mengting; Wu, Yinghai; Wu, Qunhe; Zhang, Renduo

2014-01-01

The aim of this study was to investigate the feasibility of utilizing the fruiting bodies of a jelly macro-fungus Auricularia polytricha as adsorbents to remove emulsified oil from water. The effects of several factors, including temperature, initial pH, agitation speed, and adsorbent dosage, were taken into account. Results showed that the optimized conditions for adsorption of A. polytricha were a temperature of 35°C, pH of 7.5, and agitation speed of 100 rpm. The adsorption kinetics were characterized by the pseudo-first order model, which showed the adsorption to be a fast physical process. The Langmuir-Freundlich isotherm described the adsorption very well and predicted the maximum adsorption capacity of 398 mg g−1, under optimized conditions. As illustrated by scanning electron micrographs, the oil particles were adsorbed onto the hairs covering the bottom surface and could be desorbed by normal temperature volatilization. The material could be used as an emulsified oil adsorbent at least three times, retaining more than 95% of the maximum adsorption capacity. The results demonstrated that the fruiting bodies of A. polytricha can be a useful adsorbent to remove emulsified oil from water. PMID:24743498

On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons

PubMed Central

Mitropoulos, A. C.; Stefanopoulos, K. L.; Favvas, E. P.; Vansant, E.; Hankins, N. P.

2015-01-01

Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of ‘ink-bottle’ pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary. PMID:26047466

On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons.

PubMed

Mitropoulos, A C; Stefanopoulos, K L; Favvas, E P; Vansant, E; Hankins, N P

2015-06-05

Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of 'ink-bottle' pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary.

Human hair-derived high surface area porous carbon material for the adsorption isotherm and kinetics of tetracycline antibiotics.

PubMed

Ahmed, M J; Islam, Md Azharul; Asif, M; Hameed, B H

2017-11-01

In this work, a human hair-derived high surface area porous carbon material (HHC) was prepared using potassium hydroxide activation. The morphology and textural properties of the HHC structure, along with its adsorption performance for tetracycline (TC) antibiotics, were evaluated. HHC showed a high surface area of 1505.11m 2 /g and 68.34% microporosity. The effects of most important variables, such as initial concentration (25-355mg/L), solution pH (3-13), and temperatures (30-50°C), on the HHC adsorption performance were investigated. Isotherm data analysis revealed the favorable application of the Langmuir model, with maximum TC uptakes of 128.52, 162.62, and 210.18mg/g at 30, 40, and 50°C, respectively. The experimental data of TC uptakes versus time were analyzed efficiently using a pseudo-first order model. Porous HHC could be an efficient adsorbent for eliminating antibiotic pollutants in wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects and mechanistic aspects of absorbing organic compounds by coking coal.

PubMed

Ning, Kejia; Wang, Junfeng; Xu, Hongxiang; Sun, Xianfeng; Huang, Gen; Liu, Guowei; Zhou, Lingmei

2017-11-01

Coal is a porous medium and natural absorbent. It can be used for its original purpose after adsorbing organic compounds, its value does not reduce and the pollutants are recycled, and then through systemic circulation of coking wastewater zero emissions can be achieved. Thus, a novel method of industrial organic wastewater treatment using adsorption on coal is introduced. Coking coal was used as an adsorbent in batch adsorption experiments. The quinoline, indole, pyridine and phenol removal efficiencies of coal adsorption were investigated. In addition, several operating parameters which impact removal efficiency such as coking coal consumption, oscillation contact time, initial concentration and pH value were also investigated. The coking coal exhibited properties well-suited for organics' adsorption. The experimental data were fitted to Langmuir and Freundlich isotherms as well as Temkin and Redlich-Peterson (R-P) models. The Freundlich isotherm model provided reasonable models of the adsorption process. Furthermore, the purification mechanism of organic compounds' adsorption on coking coal was analysed.

Convective cell development and propagation in a mesoscale convective complex

NASA Technical Reports Server (NTRS)

Ahn, Yoo-Shin; Brundidge, Kenneth C.

1987-01-01

A case study was made of the mesoscale convective complex (MCC) which occurred over southern Oklahoma and northern Texas on 27 May 1981. This storm moved in an eastsoutheasterly direction and during much of its lifetime was observable by radars at Oklahoma City, Ok. and Stephenville, Tx. It was found that the direction of cell (VIP level 3 or more reflectivity) propagation was somewhat erratic but approximately the same as the system (VIP level 1 reflectivity) movement and the ambient wind. New cells developed along and behind the gust front make it appear that once the MCC is initiated, a synergistic relationship exists between the gust front and the MCC. The relationship between rainfall patterns and amounts and the infrared (IR) temperature field in the satellite imagery were examined. The 210 K isotherm of GOES IR imagery was found to encompass the rain area of the storm. The heaviest rainfall was in the vicinity of the VIP level 3 cells and mostly contained within the 205 K isotherm of GOES IR imagery.

Adsorption of bentazon on CAT and CARBOPAL activated carbon: Experimental and computational study

NASA Astrophysics Data System (ADS)

Spaltro, Agustín; Simonetti, Sandra; Torrellas, Silvia Alvarez; Rodriguez, Juan Garcia; Ruiz, Danila; Juan, Alfredo; Allegretti, Patricia

2018-03-01

Removal of the bentazon by adsorption on two different types of activated carbon was investigated under various experimental conditions.Kinetics of adsorption is followed and the adsorption isotherms of the pesticide are determined. The effects of the changes in pH, ionic strength and temperature are analyzed. Computational simulation was employed to analyze the geometry and the energy of pesticide absorption on activated carbon. Concentration of bentazon decreases while increase all the variables, from the same initial concentration. Experimental data for equilibrium was analyzed by three models: Langmuir, Freundlich and Guggenheim-Anderson-de Boer isotherms. Pseudo-first and pseudo-second-order kinetics are tested with the experimental data, and pseudo-second-order kinetics was the best for the adsorption of bentazon by CAT and CARBOPAL with coefficients of correlation R2 = 0.9996 and R2 = 0.9993, respectively. The results indicated that both CAT and CARBOPAL are very effective for the adsorption of bentazon from aqueous solutions, but CAT carbon has the greater capacity.

The Efficient Removal of Heavy Metal Ions from Industry Effluents Using Waste Biomass as Low-Cost Adsorbent: Thermodynamic and Kinetic Models

NASA Astrophysics Data System (ADS)

Indhumathi, Ponnuswamy; Sathiyaraj, Subbaiyan; Koelmel, Jeremy P.; Shoba, Srinivasan U.; Jayabalakrishnan, Chinnasamy; Saravanabhavan, Munusamy

2018-05-01

The ability of green micro algae Chlorella vulgaris for biosorption of Cu(II) ions from an aqueous solution was studied. The biosorption process was affected by the solution pH, contact time, temperature and initial Cu(II) concentration. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order and intra particle diffusion models. Results showed that the sorption process of Cu(II) ions followed pseudo-second order kinetics. The sorption data of Cu(II) ions are fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms, and the Temkin isotherm. The thermodynamic study shows the Cu(II) biosorption was exothermic in nature. The Cu(II) ions were recovered effectively from Chlorella vulgaris biomass using 0.1 M H2SO4 with up to 90.3% recovery, allowing for recycling of the Cu. Green algae from freshwater bodies showed significant potential for Cu(II) removal and recovery from industrial wastewater.

Detection of HbsAg and hATIII genetically modified goats (Caprahircus) by loop-mediated isothermal amplification.

PubMed

Tao, Chenyu; Zhang, Qingde; Zhai, Shanli; Liu, Bang

2013-11-01

In this study, sensitive and rapid detection systems were designed using a loop-mediated isothermal amplification (LAMP) method to detect the genetically modified goats. A set of 4 primers were designed for each exogenous nucleic acids HBsAg and hATIII. The DNA samples were first amplified with the outer and inner primers and released a single-stranded DNA,of which both ends were stem-loop structure. Then one inner primer hybridized with the loop, and initiated displacement synthesis in less than 1 h. The result could be visualized by both agarose gel electrophoresis and unaided eyes directly after adding SYBR GREEN 1. The detection limit of LAMP was ten copies of target molecules, indicating that LAMP was tenfold more sensitive than the classical PCR. Furthermore, all the samples of genetically modified goats were tested positively by LAMP, and the results demonstrated that the LAMP was a rapid and sensitive method for detecting the genetically modified organism.

Microalgal-biochar immobilized complex: A novel efficient biosorbent for cadmium removal from aqueous solution.

PubMed

Shen, Ying; Li, Huan; Zhu, Wenzhe; Ho, Shih-Hsin; Yuan, Wenqiao; Chen, Jianfeng; Xie, Youping

2017-11-01

The feasibility of the bioremediation of cadmium (Cd) using microalgal-biochar immobilized complex (MBIC) was investigated. Major operating parameters (e.g., pH, biosorbent dosage, initial Cd(II) concentration and microalgal-biochar ratio) were varied to compare the treatability of viable algae (Chlorella sp.), biochar and MBIC. The biosorption isotherms obtained by using algae or biochar were found to have satisfactory Langmuir predictions, while the best fitting adsorption isotherm model for MBIC was the Sips model. The maximum Cd(II) adsorption capacity of MBIC with a Chlorella sp.: biochar ratio of 2:3 (217.41mgg -1 ) was higher than that of Chlorella sp. (169.92mgg -1 ) or biochar (95.82mgg -1 ) alone. The pseudo-second-order model fitted the biosorption process of MBIC well (R 2 >0.999). Moreover, zeta potential, SEM and FTIR studies revealed that electrostatic attraction, ion exchange and surface complexation were the main mechanisms responsible for Cd removal when using MBIC. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols

PubMed Central

Shiravand, Fatemeh; Hutchinson, John M.; Calventus, Yolanda; Ferrando, Francesc

2014-01-01

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF3·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF3·MEA into the clay galleries of nanocomposites containing 2 wt% MMT. PMID:28788672

Generalized Lagrangian Jacobi Gauss collocation method for solving unsteady isothermal gas through a micro-nano porous medium

NASA Astrophysics Data System (ADS)

Parand, Kourosh; Latifi, Sobhan; Delkhosh, Mehdi; Moayeri, Mohammad M.

2018-01-01

In the present paper, a new method based on the Generalized Lagrangian Jacobi Gauss (GLJG) collocation method is proposed. The nonlinear Kidder equation, which explains unsteady isothermal gas through a micro-nano porous medium, is a second-order two-point boundary value ordinary differential equation on the unbounded interval [0, ∞). Firstly, using the quasilinearization method, the equation is converted to a sequence of linear ordinary differential equations. Then, by using the GLJG collocation method, the problem is reduced to solving a system of algebraic equations. It must be mentioned that this equation is solved without domain truncation and variable changing. A comparison with some numerical solutions made and the obtained results indicate that the presented solution is highly accurate. The important value of the initial slope, y'(0), is obtained as -1.191790649719421734122828603800159364 for η = 0.5. Comparing to the best result obtained so far, it is accurate up to 36 decimal places.

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution.

PubMed

Panda, Gopal C; Das, Sujoy K; Guha, Arun K

2009-05-15

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.

Improved removal of malachite green from aqueous solution using chemically modified cellulose by anhydride.

PubMed

Zhou, Yanmei; Min, Yinghao; Qiao, Han; Huang, Qi; Wang, Enze; Ma, Tongsen

2015-03-01

Cellulose modified with maleic (M) and phthalic (P) anhydride, to be named CMA and CPA, were tested as feasible adsorbents for the removal of malachite green from aqueous solution. At the same time, the uptake ability of natural cellulose was also studied for comparison. The structure of material was characterized by FT-IR and XRD. The effects of solution pH, initial dye concentration, contact time and temperature were investigated in detail by batch adsorption experiments. The kinetic and isotherm studies suggested that the adsorption followed the pseudo-second-order model and Langmuir isotherm. The maximum adsorption capacity on CMA and CPA were 370 mg g(-1) and 111 mg g(-1), respectively. Furthermore, the thermodynamics studies indicated the spontaneous nature of adsorption of malachite green on adsorbents. All the studied results showed that the modified cellulose could be used as effective adsorption material for the removal of malachite green from aqueous solutions. Copyright © 2014 Elsevier B.V. All rights reserved.

Amputation of congo red dye from waste water using microwave induced grafted Luffa cylindrica cellulosic fiber.

PubMed

Gupta, Vinod Kumar; Pathania, Deepak; Agarwal, Shilpi; Sharma, Shikha

2014-10-13

The present study deals with the surface modification of Luffa cylindrica fiber through graft copolymerization of methyl acrylate/acrylamide (MA/AAm) via microwave radiation without the use of initiator. Various reaction parameters effecting grafting yield were optimized and physico-chemical properties were evaluated. The grafted Luffa cylindrica fiber showed morphological transformations, thermal stability and chemical resistance. The adsorption potential of modified fiber was investigated using adsorption isotherms for hazardous congo red dye removal from aqueous system. The maximum adsorption capacity of dye onto grafted Luffa cylindrica fiber was found to be 17.39 mg/g with best fit for Langmuir adsorption isotherm. The values of thermodynamic parameters such as enthalpy change, ΔH(0) (21.27 kJ/mol), entropy change, ΔS(0) (64.71 J/mol K) and free energy change, ΔG(0) (-139.52 kJ/mol) were also calculated. Adsorption process was found spontaneous and endothermic in nature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Recombinase polymerase amplification as a promising tool in hepatitis C virus diagnosis.

PubMed

Zaghloul, Hosam; El-Shahat, Mahmoud

2014-12-27

Hepatitis C virus (HCV) infection represents a significant health problem and represents a heavy load on some countries like Egypt in which about 20% of the total population are infected. Initial infection is usually asymptomatic and result in chronic hepatitis that give rise to complications including cirrhosis and hepatocellular carcinoma. The management of HCV infection should not only be focus on therapy, but also to screen carrier individuals in order to prevent transmission. In the present, molecular detection and quantification of HCV genome by real time polymerase chain reaction (PCR) represent the gold standard in HCV diagnosis and plays a crucial role in the management of therapeutic regimens. However, real time PCR is a complicated approach and of limited distribution. On the other hand, isothermal DNA amplification techniques have been developed and offer molecular diagnosis of infectious dieses at point-of-care. In this review we discuss recombinase polymerase amplification technique and illustrate its diagnostic value over both PCR and other isothermal amplification techniques.

Prompt isothermal decay properties of the Sr4Al14O25 co-doped with Eu2+ and Dy3+ persistent luminescent phosphor

NASA Astrophysics Data System (ADS)

Asal, Eren Karsu; Polymeris, George S.; Gultekin, Serdar; Kitis, George

2018-06-01

Thermoluminescence (TL) techniques are very useful in the research of the persistent Luminescence (PL) phosphors research. It gives information about the existence of energy levels within the forbidden band, its activation energy, kinetic order, lifetime etc. The TL glow curve of Sr4Al14O25 :Eu2+,Dy3+ persistent phosphor, consists of two well separated glow peaks. The TL techniques used to evaluate activation energy were the initial rise, prompt isothermal decay (PID) of TL of each peak at elevated temperatures and the glow - curve fitting. The behavior of the PID curves of the two peak is very different. According to the results of the PID procedure and the subsequent data analysis it is suggested that the mechanism behind the low temperature peak is a delocalized transition. On the other hand the mechanism behind the high temperature peak is localized transition involving a tunneling recombination between electron trap and luminescence center.

On the membrane approximation in isothermal film casting

NASA Astrophysics Data System (ADS)

Hagen, Thomas

2014-08-01

In this work, a one-dimensional model for isothermal film casting is studied. Film casting is an important engineering process to manufacture thin films and sheets from a highly viscous polymer melt. The model equations account for variations in film width and film thickness, and arise from thinness and kinematic assumptions for the free liquid film. The first aspect of our study is a rigorous discussion of the existence and uniqueness of stationary solutions. This objective is approached via the argument principle, exploiting the homotopy invariance of a family of analytic functions. As our second objective, we analyze the linearization of the governing equations about stationary solutions. It is shown that solutions for the associated boundary-initial value problem are given by a strongly continuous semigroup of bounded linear operators. To reach this result, we cast the relevant Cauchy problem in a more accessible form. These transformed equations allow us insight into the regularity of the semigroup, thus yielding the validity of the spectral mapping theorem for the semigroup and the spectrally determined growth property.

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols.

PubMed

Shiravand, Fatemeh; Hutchinson, John M; Calventus, Yolanda; Ferrando, Francesc

2014-05-30

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para -amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF₃·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF₃·MEA into the clay galleries of nanocomposites containing 2 wt% MMT.

Seasonal abundance and vertical distribution of capelin (Mallotus villosus) in relation to water temperature at a coastal site off eastern Newfoundland

USGS Publications Warehouse

Methven, David A.; Piatt, John F.

1991-01-01

The seasonal abundance and vertical distribution of capelin in relation to water temperature have been investigated by conducting repeated hydroacoustic surveys at a coastal site off eastern Newfoundland. Water temperatures were warmer in 1983 than in 1984 as indicated by the earlier appearance and greater depth of the seasonal thermocline. Correspondingly, schools of capelin appeared earlier, were more abundant, and extended deeper in the water column in 1983 than in 1984. Most capelin were found between the surface and the 5°C isotherm. In both years, initial peaks of capelin abundance occurred when nearshore water temperatures increased from about 0-1°C to above 6°C and, at or near, periods of maximum tidal oscillation. Short-term variations in the depth of the 5°C isotherm were related to nearshore wind-induced upwelling events. Annual variations corresponded to the volume of cold (>0°C) water and sea-ice transported south by the Labrador Current.

Removal of oxytetracycline and determining its biosorption properties on aerobic granular sludge.

PubMed

Mihciokur, Hamdi; Oguz, Merve

2016-09-01

This study investigates biosorption of Oxytetracycline, a broad-spectrum antibiotic, using aerobic granular sludge as an adsorbent in aqueous solutions. A sequencing batch reactor fed by a synthetic wastewater was operated to create aerobic granular sludge. Primarily, the pore structure and surface area of granular sludge, the chemical structure and the molecular sizes of the pharmaceutical, operating conditions, such as pH, stirring rate, initial concentration of Oxytetracycline, during adsorption process was verified. Subsequently, thermodynamic and kinetic aspects of the adsorption were examined and adsorption isotherm studies were carried out. It was shown that the aerobic granular sludge was a good alternative for biosorption of this pharmaceutical. The pharmaceutical was adsorbed better at pH values of 6-8. The adsorption efficiency increased with rising ionic strength. Also, it was seen that the adsorption process was an exothermic process in terms of thermodynamics. The adsorption can be well explained by Langmuir isotherm model. Copyright © 2016 Elsevier B.V. All rights reserved.

Adsorption of Toluene and Paraxylene from Aqueous Solution Using Pure and Iron Oxide Impregnated Carbon Nanotubes: Kinetics and Isotherms Study

PubMed Central

Abbas, Aamir; Ihsanullah; Al-Baghli, Nadhir A. H.

2017-01-01

Multiwall carbon nanotubes (CNTs) and iron oxide impregnated carbon nanotubes (CNTs-iron oxide) were investigated for the adsorption of hazardous toluene and paraxylene (p-xylene) from aqueous solution. Pure CNTs were impregnated with iron oxides nanoparticles using wet impregnation technique. Various characterization techniques including thermogravimetric analysis, scanning electron microscopy, elemental dispersion spectroscopy, X-ray diffraction, and nitrogen adsorption analysis were used to study the thermal degradation, surface morphology, purity, and surface area of the materials. Batch adsorption experiments show that iron oxide impregnated CNTs have higher degree of removal of p-xylene (i.e., 90%) compared with toluene (i.e., 70%), for soaking time 2 h, with pollutant initial concentration 100 ppm, at pH 6 and shaking speed of 200 rpm at 25°C. Pseudo-second-order model provides better fitting for the toluene and p-xylene adsorption. Langmuir and Freundlich isotherm models demonstrate good fitting for the adsorption data of toluene and p-xylene. PMID:28386208

P(4-vinyl pyridine) hydrogel use for the removal of UO(2)(2+) and Th(4+) from aqueous environments.

PubMed

Ozay, Ozgur; Ekici, Sema; Aktas, Nahit; Sahiner, Nurettin

2011-12-01

4-vinyl pyridine (4-VP) based hydrogels with 2-hydroxyethylmetacrylate (HEMA) and magnetic composites were prepared and tested for use in the removal of UO(2)(2+) and Th(4+) ions from aqueous environments. It was found that the absorption of these metal ions from aqueous environments decreased with an increase in the amount of HEMA contained within p(4-VP-co-HEMA) hydrogels between 0.498 mmol for pure p(4-VP) and 0.027 mmol for pure p(HEMA). The characterization of the hydrogels was determined by swelling experiments, FT-IR and thermal analysis. The effects of initial metal ion concentration, hydrogel amount and the temperature of the medium on absorption of the ions were investigated. Langmuir and Freundlich isotherms were constructed for the absorption of UO(2)(2+) and Th(4+). Both isotherms demonstrated that these metal ions complied with monolayer absorption kinetics. Copyright © 2011 Elsevier Ltd. All rights reserved.

Removal of Cd (II) from synthetic wastewater by alginate-Ayous wood sawdust (Triplochiton scleroxylon) composite material.

PubMed

Njimou, Jacques Romain; Măicăneanu, Andrada; Indolean, Cerasella; Nanseu-Njiki, Charles Péguy; Ngameni, Emmanuel

2016-01-01

The biosorption characteristics of Cd (II) ions from synthetic wastewater using raw Ayous wood sawdust (Triplochiton scleroxylon), r-AS, immobilized by sodium alginate were investigated with respect to pH, biomass quantity, contact time, initial concentration of heavy metal, temperature and stirring rate. The experimental data fitted well with the Langmuir isotherm, suggesting that monolayer adsorption of the cadmium ions onto alginate-Ayous sawdust composite (a-ASC). The obtained monolayer adsorption capacity of a-ASC for Cd (II) was 6.21 mg/g. From the Dubinin-Radushkevich isotherm model, a 5.39 kJ/mol value for the mean free energy was calculated, indicating that Cd (II) biosorption could include an important physisorption stage. Thermodynamic calculations showed that the Cd (II) biosorption process was feasible, endothermic and spontaneous in nature under examined conditions. The results indicated that a-ASC could be an alternative material replacing more costly adsorbents used for the removal of heavy metals.

Long-Term Isothermal Aging Effects on Carbon Fabric-Reinforced PMR-15 Composites: Compression Strength

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; Roberts, Gary D.; Kamvouris, John E.

1996-01-01

A study was conducted to determine the effects of long-term isothermal thermo-oxidative aging on the compressive properties of T-650-35 fabric reinforced PMR-15 composites. The temperatures that were studied were 204, 260, 288, 316, and 343 C. Specimens of different geometries were evaluated. Cut edge-to-surface ratios of 0.03 to 0.89 were fabricated and aged. Aging times extended to a period in excess of 15,000 hours for the lower temperature runs. The unaged and aged specimens were tested in compression in accordance with ASTM D-695. Both thin and thick (plasma) specimens were tested. Three specimens were tested at each time/temperature/geometry condition. The failure modes appeared to be initiated by fiber kinking with longitudinal, interlaminar splitting. In general, it appears that the thermo-oxidative degradation of the compression strength of the composite material may occur by both thermal (time-dependent) and oxidative (weight-loss) mechanisms. Both mechanisms appear to be specimen-thickness dependent.

Summary report on the evaluation of a 1977--1985 edited sorption data base for isotherm modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polzer, W.L.; Beckman, R.J.; Fuentes, H.R.

1993-09-01

Sorption data bases collected by Los Alamos National Laboratory (LANL) from 1977 to 1985 for the Yucca Mountain Project.(YMP) have been inventoried and fitted with isotherm expressions. Effects of variables (e.g., particle size) on the isotherm were also evaluated. The sorption data are from laboratory batch measurements which were not designed specifically for isotherm modeling. However a limited number of data sets permitted such modeling. The analysis of those isotherm data can aid in the design of future sorption experiments and can provide expressions to be used in radionuclide transport modeling. Over 1200 experimental observations were inventoried for their adequacymore » to be modeled b isotherms and to evaluate the effects of variables on isotherms. About 15% of the observations provided suitable data sets for modeling. The data sets were obtained under conditions that include ambient temperature and two atmospheres, air and CO{sub 2}.« less

Soil-adjusted sorption isotherms for arsenic(V) and vanadium(V)

NASA Astrophysics Data System (ADS)

Rückamp, Daniel; Utermann, Jens; Florian Stange, Claus

2017-04-01

The sorption characteristic of a soil is usually determined by fitting a sorption isotherm model to laboratory data. However, such sorption isotherms are only valid for the studied soil and cannot be transferred to other soils. For this reason, a soil-adjusted sorption isotherm can be calculated by using the data of several soils. Such soil-adjusted sorption isotherms exist for cationic heavy metals, but are lacking for heavy metal oxyanions. Hence, the aim of this study is to establish soil-adjusted sorption isotherms for the oxyanions arsenate (arsenic(V)) and vanadate (vanadium(V)). For the laboratory experiment, 119 soils (samples from top- and subsoils) typical for Germany were chosen. The batch experiments were conducted with six concentrations of arsenic(V) and vanadium(V), respectively. By using the laboratory data, sorption isotherms for each soil were derived. Then, the soil-adjusted sorption isotherms were calculated by non-linear regression of the sorption isotherms with additional soil parameters. The results indicated a correlation between the sorption strength and oxalate-extractable iron, organic carbon, clay, and electrical conductivity for both, arsenic and vanadium. However, organic carbon had a negative regression coefficient. As total organic carbon was correlated with dissolved organic carbon; we attribute this observation to an effect of higher amounts of dissolved organic substances. We conclude that these soil-adjusted sorption isotherms can be used to assess the potential of soils to adsorb arsenic(V) and vanadium(V) without performing time-consuming sorption experiments.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Steepening of the density profile under the action of a ponderomotive force during isothermal planar plasma expansion

NASA Astrophysics Data System (ADS)

Garanin, Sergey G.; Kir'yanov, Yu F.; Kochemasov, G. G.

1990-06-01

A theoretical investigation is reported of the deformation of the density profile of a plasma by a ponderomotive force under transient conditions. Initially, the structure of the density profile near the critical point coincides exactly with the solution of the steady-state problem. Plasma expansion is accompanied by growth of a spiky instability in the form of stimulated Brillouin scattering.

Impact of a commercial glyphosate formulation on adsorption of Cd(II) and Pb(II) ions on paddy soil.

PubMed

Divisekara, T; Navaratne, A N; Abeysekara, A S K

2018-05-01

Use of glyphosate as a weedicide on rice cultivation has been a controversial issue in Sri Lanka, due to the hypothesis that the metal complexes of commercial glyphosate is one of the causative factors of Chronic Kidney Disease of unknown aetiology (CKDu) prevalent in some parts of Sri Lanka. The effect of commercial glyphosate on the adsorption and desorption of Cd(II) and Pb(II) ions on selective paddy soil studied using batch experiments, over a wide concentration range, indicates that the Langmuir adsorption isotherm model is obeyed at low initial metal ion concentrations while the Freundlich adsorption isotherm model obeys at high metal ion concentrations in the presence and absence of glyphosate. For all cases, adsorption of both Cd(II) and Pb(II) ions obeys pseudo second order kinetics, suggesting that initial adsorption is a chemisorption process. In the presence of glyphosate formulation, the extent of adsorption of Cd(II) and Pb(II) ions on soil is decreased, while their desorption is increased at high concentrations of glyphosate. Low concentrations of glyphosate formulation do not significantly affect the desorption of metal ions from soil. Reduction of adsorption leads to enhance the concentration of Cd(II) and Pb(II) ions in the aqueous phase when in contact with soil. Copyright © 2018 Elsevier Ltd. All rights reserved.

Durability of Polymer Electrolyte Membrane Fuel Cells Operated at Subfreezing Temperatures

DOE PAGES

Macauley, Natalia; Lujan, Roger W.; Spernjak, Dusan; ...

2016-09-15

The structure, composition, and interfaces of membrane electrode assemblies (MEA) and gas-diffusion layers (GDLs) have a significant effect on the performance of single-proton-exchange-membrane (PEM) fuel cells operated isothermally at subfreezing temperatures. During isothermal constant-current operation at subfreezing temperatures, water forming at the cathode initially hydrates the membrane, then forms ice in the catalyst layer and/or GDL. This ice formation results in a gradual decay in voltage. High-frequency resistance initially decreases due to an increase in membrane water content and then increases over time as the contact resistance increases. The water/ice holding capacity of a fuel cell decreases with decreasing subfreezingmore » temperature (-10°C vs. -20°C vs. -30°C) and increasing current density (0.02 A cm -2 vs. 0.04 A cm -2). Ice formation monitored using in-situ high-resolution neutron radiography indicated that the ice was concentrated near the cathode catalyst layer at low operating temperatures (≈-20°C) and high current densities (0.04 A cm -2). Significant ice formation was also observed in the GDLs at higher subfreezing temperatures (≈-10°C) and lower current densities (0.02 A cm -2). These results are in good agreement with the long-term durability observations that show more severe degradation at lower temperatures (-20°C and -30°C).« less

The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire.

PubMed

Belgacem, Ahmed; Rebiai, Rachid; Hadoun, Hocine; Khemaissia, Sihem; Belmedani, Mohamed

2014-01-01

In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m(2)/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.

Ultrasonic enhancement of the simultaneous removal of quaternary toxic organic dyes by CuO nanoparticles loaded on activated carbon: Central composite design, kinetic and isotherm study.

PubMed

Dashamiri, Somayeh; Ghaedi, Mehrorang; Dashtian, Kheibar; Rahimi, Mahmood Reza; Goudarzi, Alireza; Jannesar, Ramin

2016-07-01

Copper oxide nanoparticles loaded on activated carbon (CuO-NPs-AC) were prepared and fully analyzed and characterized with FE-SEM, XRD and FT-IR. Subsequently, this novel material was used for simultaneous ultrasound-assisted adsorption of brilliant green (BG), auramine O (AO), methylene blue (MB) and eosin yellow (EY) dyes. Problems regard to dyes spectra overlap in quaternary solution of this dyes were omitted by derivative spectrophotometric method. The best pH in quaternary system was studied by using one at a time method to achieved maximum dyes removal percentage. Subsequently, sonication time, adsorbent dosage and initial dyes concentrations influence on dyes removal was optimized by central composite design (CCD) combined with desirability function approach (DFA). Desirability score of 0.978 show optimum conditions set at sonication time (4.2 min), adsorbent mass (0.029 g), initial dyes concentration (4.5 mg L(-1)). Under this optimum condition the removal percentage for MB, AO, EY and BG dyes 97.58, 94.66, 96.22 and 94.93, respectively. The adsorption rate well fitted by pseudo second-order while adsorption capacity according to the Langmuir model as best equilibrium isotherm model for BG, MB, AO and EY was 20.48, 21.26, 22.34 and 21.29 mg g(-1), respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

PubMed Central

Kucuker, Mehmet Ali; Wieczorek, Nils; Kuchta, Kerstin; Copty, Nadim K.

2017-01-01

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus. PMID:28388641

Thermodynamic and kinetic studies of biosorption of iron and manganese from aqueous medium using rice husk ash

NASA Astrophysics Data System (ADS)

Adekola, F. A.; Hodonou, D. S. S.; Adegoke, H. I.

2016-11-01

The adsorption behavior of rice husk ash with respect to manganese and iron has been studied by batch methods to consider its application for water and waste water treatment. The optimum conditions of adsorption were determined by investigating the effect of initial metal ion concentration, contact time, adsorbent dose, pH value of aqueous solution and temperature. Adsorption equilibrium time was observed at 120 min. The adsorption efficiencies were found to be pH dependent. The equilibrium adsorption experimental data were found to fit the Langmuir, Freundlich and Temkin isotherms for iron, but fitted only Langmuir isotherm for manganese. The pseudo-second order kinetic model was found to describe the manganese and iron kinetics more effectively. The thermodynamic experiment revealed that the adsorption processes involving both metals were exothermic. The adsorbent was finally applied to typical raw water with initial manganese and iron concentrations of 3.38 mg/l for Fe and 6.28 mg/l, respectively, and the removal efficiency was 100 % for Mn and 70 % for Fe. The metal ions were desorbed from the adsorbent using 0.01 M HCl, it was found to quantitatively remove 67 and 86 % of Mn and Fe, respectively, within 2 h. The results revealed that manganese and iron are considerably adsorbed on the adsorbent and could be an economic method for the removal of these metals from aqueous solutions.

Biosorption of Cd(II) by live and dead cells of Bacillus cereus RC-1 isolated from cadmium-contaminated soil.

PubMed

Huang, Fei; Dang, Zhi; Guo, Chu-Ling; Lu, Gui-Ning; Gu, Roy R; Liu, Hong-Juan; Zhang, Hui

2013-07-01

The present study investigated the biosorption capacity of live and dead cells of Bacillus cereus RC-1 for Cd(II). The biosorption characteristics were investigated as a function of initial pH, contact time, and initial cadmium concentration. Equilibrium biosorption was modeled using Langmuir, Freundlich and Redlich-Peterson isotherm equations. It was found that the maximum biosorption capacities calculated from Langmuir isotherm were 31.95 mg/g and 24.01 mg/g for dead cells and live cells, respectively. The kinetics of the biosorption was better described by pseudo-second order kinetic model. Desorption efficiency of biosorbents was investigated at various pH values. These results indicated that dead cells have higher Cd(II) biosorption capacity than live cells. Furthermore, zeta potential, transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FTIR) studies were carried out to understand the differences in the Cd(II) biosorption behavior for the both biosorbents. The bioaccumulation of Cd(II) by B. cereus RC-1 was found to depend largely on extracellular biosorption rather than intracellular accumulation. Based on the above studies, dead biomass appears to be a more efficient biosorbent for the removal of Cd(II) from aqueous solution. Copyright © 2013 Elsevier B.V. All rights reserved.

Batch and continuous (fixed-bed column) biosorption of crystal violet by Artocarpus heterophyllus (jackfruit) leaf powder.

PubMed

Saha, Papita Das; Chakraborty, Sagnik; Chowdhury, Shamik

2012-04-01

In this study, batch and fixed-bed column experiments were performed to investigate the biosorption potential of Artocarpus heterophyllus (jackfruit) leaf powder (JLP) to remove crystal violet (CV) from aqueous solutions. Batch biosorption studies were carried out as a function of solution pH, contact time, initial dye concentration and temperature. The biosorption equilibrium data showed excellent fit to the Langmuir isotherm model with maximum monolayer biosorption capacity of 43.39 mg g(-1) at pH 7.0, initial dye concentration=50 mg L(-1), temperature=293 K and contact time=120 min. According to Dubinin-Radushkevich (D-R) isotherm model, biosorption of CV by JLP was chemisorption. The biosorption kinetics followed the pseudo-second-order kinetic model. Thermodynamic analysis revealed that biosorption of CV from aqueous solution by JLP was a spontaneous and exothermic process. In order to ascertain the practical applicability of the biosorbent, fixed-bed column studies were also performed. The breakthrough time increased with increasing bed height and decreased with increasing flow rate. The Thomas model as well as the BDST model showed good agreement with the experimental results at all the process parameters studied. It can be concluded that JLP is a promising biosorbent for removal of CV from aqueous solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

Activated carbons from potato peels: The role of activation agent and carbonization temperature of biomass on their use as sorbents for bisphenol A uptake from aqueous solutions

NASA Astrophysics Data System (ADS)

Arampatzidou, An; Deliyanni, Eleni A.

2015-04-01

Activated carbons prepared from potato peels, a solid waste by product, and activated with different activating chemicals, have been studied for the adsorption of an endocrine disruptor (Bisphenol-A) from aqueous solutions. The potato peels biomass was activated with phosphoric acid, KOH and ZnCl2. The different activating chemicals were tested in order the better activation agent to be found. The carbons were carbonized by pyrolysis, in one step procedure, at three different temperatures in order the role of the temperature of carbonization to be pointed out. The porous texture and the surface chemistry of the prepared activated carbons were characterized by Nitrogen adsorption (BET), Scanning Electron Microscope (SEM), thermal analysis (DTA) and Fourier Transform Infrared Spectroscopy (FTIR). Batch experiments were performed to investigate the effect of pH, the adsorbent dose, the initial bisphenol A concentration and temperature. Equilibrium adsorption data were analyzed by Langmuir and Freundlich isotherms. The thermodynamic parameters such as the change of enthalpy (ΔH0), entropy (ΔS0) and Gibb's free energy (ΔG0) of adsorption systems were also evaluated. The adsorption capacity calculated from the Langmuir isotherm was found to be 450 mg g-1 at an initial pH 3 at 25 °C for the phosphoric acid activated carbon, that make the activated carbon a promising adsorbent material.

Pyrolysis kinetics of coking coal mixed with biomass under non-isothermal and isothermal conditions.

PubMed

Jeong, Ha Myung; Seo, Myung Won; Jeong, Sang Mun; Na, Byung Ki; Yoon, Sang Jun; Lee, Jae Goo; Lee, Woon Jae

2014-03-01

To investigate the kinetic characteristics of coking coal mixed with biomass during pyrolysis, thermogravimetric (TG) and thermo-balance reactor (TBR) analyses were conducted under non-isothermal and isothermal condition. Yellow poplar as a biomass (B) was mixed with weak coking coal (WC) and hard coking coal (HC), respectively. The calculated activation energies of WC/B blends were higher than those of HC/B blends under non-isothermal and isothermal conditions. The coal/biomass blends show increased reactivity and decreased activation energy with increasing biomass blend ratio, regardless of the coking properties of the coal. The different char structures of the WC/B and HC/B blends were analyzed by BET and SEM. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Thermodynamic Theory Of Solid Viscoelasticity. Part 1: Linear Viscoelasticity.

NASA Technical Reports Server (NTRS)

Freed, Alan D.; Leonov, Arkady I.

2002-01-01

The present series of three consecutive papers develops a general theory for linear and finite solid viscoelasticity. Because the most important object for nonlinear studies are rubber-like materials, the general approach is specified in a form convenient for solving problems important for many industries that involve rubber-like materials. General linear and nonlinear theories for non-isothermal deformations of viscoelastic solids are developed based on the quasi-linear approach of non-equilibrium thermodynamics. In this, the first paper of the series, we analyze non-isothermal linear viscoelasticity, which is applicable in a range of small strains not only to all synthetic polymers and bio-polymers but also to some non-polymeric materials. Although the linear case seems to be well developed, there still are some reasons to implement a thermodynamic derivation of constitutive equations for solid-like, non-isothermal, linear viscoelasticity. The most important is the thermodynamic modeling of thermo-rheological complexity , i.e. different temperature dependences of relaxation parameters in various parts of relaxation spectrum. A special structure of interaction matrices is established for different physical mechanisms contributed to the normal relaxation modes. This structure seems to be in accord with observations, and creates a simple mathematical framework for both continuum and molecular theories of the thermo-rheological complex relaxation phenomena. Finally, a unified approach is briefly discussed that, in principle, allows combining both the long time (discrete) and short time (continuous) descriptions of relaxation behaviors for polymers in the rubbery and glassy regions.

Examination of fluorination effect on physical properties of saturated long-chain alcohols by DSC and Langmuir monolayer.

PubMed

Nakahara, Hiromichi; Nakamura, Shohei; Okahashi, Yoshinori; Kitaguchi, Daisuke; Kawabata, Noritake; Sakamoto, Seiichi; Shibata, Osamu

2013-02-01

Partially fluorinated long-chain alcohols have been newly synthesized from a radical reaction, which is followed by a reductive reaction. The fluorinated alcohols have been investigated by differential scanning calorimetry (DSC) and compression isotherms in a Langmuir monolayer state. Their melting points increase with an increase in chain length due to elongation of methylene groups. However, the melting points for the alcohols containing shorter fluorinated moieties are lower than those for the typical hydrogenated fatty alcohols. Using the Langmuir monolayer technique, surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of monolayers of the fluorinated alcohols have been measured in the temperature range from 281.2 to 303.2K. In addition, a compressibility modulus (Cs(-1)) is calculated from the π-A isotherms. Four kinds of the alcohol monolayers show a phase transition (π(eq)) from a disordered to an ordered state upon lateral compression. The π(eq) values increase linearly with increasing temperatures. A slope of π(eq) against temperature for the alcohols with shorter fluorocarbons is unexpectedly larger than that for the corresponding fatty alcohols. Generally, fluorinated amphiphiles have a greater thermal stability (or resistance), which is a characteristic of highly fluorinated or perfluorinated compounds. Herein, however, the alcohols containing perfluorobutylated and perfluorohexylated chains show the irregular thermal behavior in both the solid and monolayer states. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorption performance of titanium dioxide (TiO2) coated air filters for volatile organic compounds.

PubMed

Zhong, Lexuan; Lee, Chang-Seo; Haghighat, Fariborz

2012-12-01

The photocatalytic oxidation (PCO) technology as an alternative method for air purification has been studied for decades and a variety of PCO models indicate that the adsorption of reactants on the catalyst surface is one of the major physical and chemical processes occurring at a heterogeneous photocatalytic reaction. However, limited study explored the adsorption effect of a photocatalyst. This study carried out a systematic evaluation of adsorption performance of titanium dioxide (TiO(2)) coated fiberglass fibers (FGFs), TiO(2) coated carbon cloth fibers (CCFs), and original CCFs air filters at various relative humidity conditions for nine volatile organic compounds. TiO(2)/FGFs, TiO(2)/CCFs, and CCFs were characterized by SEM for morphology and N(2) adsorption isotherm for BET surface area and pore structure. A bench-scale adsorption test setup was constructed and adsorption tests were performed at various relative humidity conditions and four different injected concentrations for each compound. The isothermal adsorption curves at low concentration levels were obtained and they were well described by Langmuir isotherm model. It was noticed that there were significant differences between the adsorption behaviors and photocatalytic activities of TiO(2)/FGFs and TiO(2)/CCFs. It was concluded that adsorption performance is closely related to the characteristics of substrates and therefore, the development of a substrate with high adsorption ability is a promising trend for improving the performance of the UV-PCO technology. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorption behavior of optical brightening agent on microfibrillated cellulose studied through inverse liquid chromatography: The need to correct for axial dispersion effect.

PubMed

Serroukh, Sonia; Huber, Patrick; Lallam, Abdelaziz

2018-01-19

Inverse liquid chromatography is a technique for studying solid/liquid interaction and most specifically for the determination of solute adsorption isotherm. For the first time, the adsorption behaviour of microfibrillated cellulose was assessed using inverse liquid chromatography. We showed that microfibrillated cellulose could adsorb 17 mg/g of tetrasulfonated optical brightening agent in typical papermaking conditions. The adsorbed amount of hexasulfonated optical brightening agent was lower (7 mg/g). The packing of the column with microfibrillated cellulose caused important axial dispersion (D a  = 5e-7 m²/s). Simulation of transport phenomena in the column showed that neglecting axial dispersion in the analysis of the chromatogram caused significant error (8%) in the determination of maximum adsorbed amount. We showed that conventional chromatogram analysis technique such as elution by characteristic point could not be used to fit our data. Using a bi-Langmuir isotherm model improved the fitting, but did not take into account axial dispersion, thus provided adsorption parameters which may have no physical significance. Using an inverse method with a single Langmuir isotherm, and fitting the transport equation to the chromatogram was shown to provide a satisfactory fitting to the chromatogram data. In general, the inverse method could be recommended to analyse inverse liquid chromatography data for column packing with significant axial dispersion (D a   > 1e-7 m²/s). Copyright © 2017 Elsevier B.V. All rights reserved.

Composite polymeric beads containing N,N,N',N'-tetraoctyldiglycolamide for actinide ion uptake from nitric acid feeds: Batch uptake, kinetic modelling and column studies.

PubMed

Gujar, R B; Mohapatra, P K; Lakshmi, D Shanthana; Figoli, A

2015-11-27

Polyethersulphone (PES) based composite polymeric beads (CPB) containing TODGA (N,N,N',N'-tetraoctyldiglycolamide) as the extractant were prepared by conventional phase inversion technique and were tested for the uptake of actinide ions such as Am(3+), UO2(2+), Pu(4+), Np(4+) and fission product ions such as Eu(3+) and Sr(2+). The CPBs containing 2.5-10wt.% TODGA were characterized by various physical methods and their porosity, size, surface morphology, surface area and the degradation profile by thermogravimetry were analyzed. The batch uptake studies involved kinetics of metal ion sorption, uptake as a function of nitric acid concentration, kinetic modelling and adsorption isotherms and most of the studies involved the Am(3+) ions. The batch saturation sorption capacities for Eu(3+) loading at 3M HNO3 were determined to be 6.6±0.02, 9.1±0.02 and 22.3±0.04mgg(-1) of CRBs with 2.5wt.%, 5wt.% and 10wt.% TODGA, respectively. The sorption isotherm analysis with Langmuir, D-R and Freundlisch isotherms indicated chemisorption monolayer mechanism. Chromatographic studies indicated breakthrough of Eu(3+) (using a solution containing Eu carrier) after about 0.75 bed volume (3.5-4mL). Elution of the loaded Eu was carried out using 0.01M EDTA as the eluent. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis, characterization and study of sorption parameters of multi-walled carbon nanotubes/chitosan nanocomposite for the removal of picric acid from aqueous solutions.

PubMed

Khakpour, Roghayeh; Tahermansouri, Hasan

2018-04-01

The modification of carboxylated multi-wall carbon nanotubes (MWCNT-COOH) with chitosan (Chi) has been investigated to prepare a nanocomposite material (MWCNT-Chi) for the removal of picric acid from aqueous solutions. Materials were characterized by FT-IR, TGA, DTG, FESEM, EDX, BET and zeta potential. Batch experiments such as solution pH, dosage of adsorbents, contact time, concentration of the picric acid and temperature were achieved to study sorption process. Kinetic studies were well described by pseudo-second-order kinetic model for both adsorbents. The six isotherm models: Langmuir (four linear forms), Freundlich, Tempkin, Halsey, Harkins-Jura and Dubinin-Radushkevich models were applied to determine the characteristic parameters of the adsorption process. Isotherm studies showed that the Langmuir isotherm for MWCNT-Chi and Freundlich and Halsey models for both adsorbents were found to best represent the measured sorption data. In addition, the results of Dubinin-Radushkevich model confirmed the physical adsorption. Negative ΔG° values for MWCNT-Chi and positive ones for MWCNT-COOH indicated the nature of spontaneous and unspontaneous, respectively for adsorption process in the range of the studied concentrations. In addition, picric acid molecules can be desorbed from MWCNT-Chi up to 90% at pH = 9 and that the consumed MWCNT-Chi could be reutilized up to 5th cycle of regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Organosolv delignification of Eucalyptus globulus: Kinetic study of autocatalyzed ethanol pulping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliet, M.; Rodriguez, F.; Santos, A.

2000-01-01

The autocatalyzed delignification of Eucalyptus globulus in 50% ethanol (w/w) was modeled as the irreversible and consecutive dissolution of initial, bulk, and residual lignin. Their respective contributions to total lignin was estimated as 9, 75, and 16%. Isothermal pulping experiments were carried out to evaluate an empirical kinetic model among eight proposals corresponding to different reaction schemes. The calculated activation energy was found to be 96.5, 98.5, and 40.8 kJ/mol for initial, bulk, and residual delignification, respectively. The influence of hydrogen ion concentration was expressed by a power-law function model. The kinetic model developed here was validated using data frommore » nonisothermal pulping runs.« less

Magnetic constraints on early lunar evolution revisited: Limits on accuracy imposed by methods of paleointensity measurements

NASA Technical Reports Server (NTRS)

Banerjee, S. K.

1984-01-01

It is impossible to carry out conventional paleointensity experiments requiring repeated heating and cooling to 770 C without chemical, physical or microstructural changes on lunar samples. Non-thermal methods of paleointensity determination have been sought: the two anhysteretic remanent magnetization (ARM) methods, and the saturation isothermal remanent magnetization (IRMS) method. Experimental errors inherent in these alternative approaches have been investigated to estimate the accuracy limits on the calculated paleointensities. Results are indicated in this report.

Ground-based simulation of telepresence for materials science experiments. [remote viewing and control of processes aboard Space Station

NASA Technical Reports Server (NTRS)

Johnston, James C.; Rosenthal, Bruce N.; Bonner, Mary JO; Hahn, Richard C.; Herbach, Bruce

1989-01-01

A series of ground-based telepresence experiments have been performed to determine the minimum video frame rate and resolution required for the successive performance of materials science experiments in space. The approach used is to simulate transmission between earth and space station with transmission between laboratories on earth. The experiments include isothermal dendrite growth, physical vapor transport, and glass melting. Modifications of existing apparatus, software developed, and the establishment of an inhouse network are reviewed.

Considerations concerning fatigue life of metal matrix composites

NASA Technical Reports Server (NTRS)

Radhakrishnan, V. M.; Bartolotta, Paul A.

1993-01-01

Since metal matrix composites (MMC) are composed from two very distinct materials each having their own physical and mechanical properties, it is feasible that the fatigue resistance depends on the strength of the weaker constituent. Based on this assumption, isothermal fatigue lives of several MMC's were analyzed utilizing a fatigue life diagram approach. For each MMC, the fatigue life diagram was quantified using the mechanical properties of its constituents. The fatigue life regions controlled by fiber fracture and matrix were also quantitatively defined.

Characteristics of American coals in relation to their conversion into clean energy fuels. Quarterly technical progress report, July-September 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spackman, W.; Davis, A.; Walker, P. L.

1979-05-01

Certain important aspects of the chemical and physical composition of American lignite coals are being characterized. Differential scanning calorimetry and thermogravimetric analysis were used to study the interaction between oxygen and seventeen coal chars (40 x 100 mesh) at 100/sup 0/C. The same techniques were used to investigate briefly the interaction between air and a highly caking coal at selected isothermal temperatures in the range 100 to 275/sup 0/C.

A simulation of streaming flows associated with acoustic levitators

NASA Astrophysics Data System (ADS)

Rednikov, A.; Riley, N.

2002-04-01

Steady-state acoustic streaming flow patterns have been observed by Trinh and Robey [Phys. Fluids 6, 3567 (1994)], during the operation of a variety of single axis ultrasonic levitators in a gaseous environment. Microstreaming around levitated samples is superimposed on the streaming flow which is observed in the levitator even in the absence of any particle therein. In this paper, by physical arguments, numerical and analytical simulations we provide entirely satisfactory interpretations of the observed flow patterns in both isothermal and nonisothermal situations.

Detailed sorption characteristics of the anti-diabetic drug metformin and its transformation product guanylurea in agricultural soils.

PubMed

Briones, Rowena M; Sarmah, Ajit K

2018-07-15

Detection of metformin, an antidiabetic drug and its transformation product guanylurea in various environmental matrices such as surface water and groundwater, coupled with their effects on aquatic organisms warrant an understanding of the compounds fate and behaviour in the environment. Batch studies were conducted with the aim of evaluating the sorption of these two emerging contaminants in six New Zealand agricultural soils of contrasting physico-chemical properties. Kinetic studies revealed that metformin and guanylurea sorption in Te Kowhai soil was very rapid initially achieving 90% sorption within the first 4 and 13h, respectively. Fit of several isotherm models to the measured batch sorption data showed that the hybrid models Langmuir-Freundlich and Redlich-Peterson best described the isotherms. Freundlich isotherm showed higher linearity for guanylurea (n F =0.58-0.93) in all soils compared to metformin (n F =0.25-0.71). A linear isotherm was fitted at environmentally relevant low concentrations (< 3mg/L) of target compounds and calculated values of sorption distribution coefficient (K d ) were in the range of 8.97 to 53.49L/kg for metformin and between 10.6 and 37.51L/kg for guanylurea. Sorption of both metformin and guanylurea was dependent on the soil characteristics, however, no generalisation could be made as to which had higher affinity to soils studied. Pearson's correlation and multiple regression analyses indicate that Si/Al (p=0.042) and clay (p=0.015) significantly influenced metformin K d values, whereas the soil's cation exchange capacity (p=0.024) is the single most significant factor determining guanylurea sorption in soils. It is likely that the type of minerals present in soils and its ion-exchange capacity could play an important role in metformin and guanylurea sorption, respectively. Copyright © 2018. Published by Elsevier B.V.

Waste isolation safety assessment program. Task 4. Collection and generation of transport data theoretical and experimental evaluation of waste transport in selected rocks. Annual progress report, October 1, 1978-September 30, 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, R.J.; Benson, L.V.; Yee, A.W.

1979-09-30

The objective of the program is to establish a basis for the prediction of radionuclide sorption in geologic environments. In FY 79, experimental and theoretical efforts were concentrated on a study of the sorption of cesium on the solid substrates Min-u-sil (quartz) and Belle Fourche clay (montmorillonite). Cesium sorption isotherms were obtained for the two substrates at 26/sup 0/C as a function of initial Cs concentration in solution (10/sup -3/M to 10/sup -9/M), pH (5 to 10) and supporting electrolyte concentration (0.002M, 0.01M, 0.1M, and 1M) NaCl and a simulated basalt groundwater in batch-type experiments using crushed material. Characterization ofmore » the solid phases included measurements of chemical compositions, particle sizes, surface areas, and cation-exchange capacities. In addition, potentiometric acid/base titrations of the solid phases were conducted in order to determine the acid dissociation and electrolyte exchange constants of the surfaces. Preliminary analysis of the sorption data indicate that while the clay data could be explained by simple mass-action expressions, the quartz data could not. Theoretical efforts were aimed at developing and testing an electrolyte binding electrical double-layer model to predict sorption isotherms. A computerized version of the model, MINEQL, which simultaneously considers surface and solution chemical equilibria, was brought to operational status. Input parameters required by MINEQL were determined and sorption isotherms for Cs on the Belle Fourche clay were calculated over the same range of parameters as the experimental measurements. Comparisons showed that the model was able to simulate the isotherms quite well except at the lowest pH values for the 0.002M and 0.01M NaCl solutions.« less

Adsorption isotherms of water on mica: redistribution and film growth.

PubMed

Malani, Ateeque; Ayappa, K G

2009-01-29

Adsorption isotherms of water on muscovite mica are obtained using grand canonical Monte Carlo simulations over a wide range of relative vapor pressures, p/p(0) at 298 K. Three distinct stages are observed in the adsorption isotherm. A sharp rise in the water coverage occurs for 0 < p/p(0) < 0.1. This is followed by a relatively slow increase in the coverage for 0.1 < or = p/p(0) < or = 0.7. Above p/p(0) = 0.7, a second increase in the coverage occurs due to the adsorption of water with bulklike features. The derived film thickness and isotherm shape for the simple point charge (SPC) water model is in excellent agreement with recent experiments of Balmer et al. [ Langmuir 2008 , 24 , 1566 ]. A novel observation is the significant redistribution of water between adsorbed layers as the water film develops. This redistribution is most pronounced for 0.1 < or = p/p(0) < or = 0.7, where water is depleted from the inner layers and film growth is initiated on the outer layer. During this stage, potassium hydration is found to play a dominant role in the rearrangement of water near the mica surface. The analysis of structural features reveals a strongly bound first layer of water molecules occupying the ditrigonal cavities between the potassium ions. In-plane structure of oxygen in the second layer, which forms part of the first hydration shell of potassium, reveals a liquidlike structure with the oxygen-oxygen pair correlation function displaying features similar to bulk water. Isosteric heats of adsorption were found to be in good agreement with the differential microcalorimetric data of Rakhmatkariev ( Clays Clay Miner. 2006 , 54 , 402 ), over the entire range of pressures investigated. Both SPC and extended simple point charge (SPC/E) water models were found to yield qualitatively similar adsorption and structural characteristics, with the SPC/E model predicting lower coverages than the SPC model for p/p(0) > 0.7.

Thermo-elastic-plastic analysis for elastic component under high temperature fatigue crack growth rate

NASA Astrophysics Data System (ADS)

Ali, Mohammed Ali Nasser

The research project presents a fundamental understanding of the fatigue crack growth mechanisms of AISI 420 martensitic stainless steel, based on the comparison analysis between the theoretical and numerical modelling, incorporating research findings under isothermal fatigue loading for solid cylindrical specimen and the theoretical modelling with the numerical simulation for tubular specimen when subjected to cyclic mechanical loading superimposed by cyclic thermal shock.The experimental part of this research programme studied the fatigue stress-life data for three types of surface conditions specimen and the isothermal stress-controlled fatigue testing at 300 °C - 600 °C temperature range. It is observed that the highest strength is obtained for the polished specimen, while the machined specimen shows lower strength, and the lowest strength is the notched specimen due to the high effect of the stress concentration. The material behaviour at room and high temperatures shows an initial hardening, followed by slow extension until fully plastic saturation then followed by crack initiation and growth eventually reaching the failure of the specimen, resulting from the dynamic strain ageing occurred from the transformation of austenitic microstructure to martensite and also, the nucleation of precipitation at grain boundaries and the incremental temperature increase the fatigue crack growth rate with stress intensity factor however, the crack growth rate at 600 °C test temperature is less than 500 °C because of the creep-fatigue taking place.The theoretical modelling presents the crack growth analysis and stress and strain intensity factor approaches analysed in two case studies based on the addition of thermo-elastic-plastic stresses to the experimental fatigue applied loading. Case study one estimates the thermal stresses superimposed sinusoidal cyclic mechanical stress results in solid cylinder under isothermal fatigue simulation. Case study two estimates the transient thermal stresses superimposed on cyclic mechanical loading results in hollow cylinder under thermal shock in heating case and down shock cooling case. The combination of stress and strain intensity factor theoretical calculations with the experimental output recorded data shows a similar behaviour with increasing temperature, and there is a fair correlation between the profiles at the beginning and then divergence with increasing the crack length. The transient influence of high temperature in case two, giving a very high thermal shock stress as a heating or cooling effects, shifting up the combined stress, when applied a cyclic mechanical load in fraction of seconds, and the reputations of these shocks, causing a fast failure under high thermal shock stress superimposed with mechanical loading.Finally, the numerical modelling analyses three cases studied were solved due to the types of loading and types of specimen geometry by using finite element models constructed through the ANSYS Workbench version 13.0. The first case is a low cyclic fatigue case for a solid cylinder specimen simulated by applying a cyclic mechanical loading. The second is an isothermal fatigue case for solid cylinder specimen simulated by supplying different constant temperatures on the outer surface with cyclic mechanical loading, where the two cases are similar to the experimental tests and the third case, is a thermo-mechanical fatigue for a hollow cylinder model by simulating a thermal up-shock generated due to transient heating on the outer surface of the model or down shock cooling on the inner surface with the cyclic mechanical loading. The results show a good agreement with the experimental data in terms of alternative stress and life in the first case. In case two results show the strain intensity factor is increases with increasing temperature similar to the theoretical solution due to the influence of the modulus of elasticity and the difference in life estimation with the experimental output record is related to the input data made of theoretical physical properties and the experimental stress-life data.

Column Chromatography To Obtain Organic Cation Sorption Isotherms.

PubMed

Jolin, William C; Sullivan, James; Vasudevan, Dharni; MacKay, Allison A

2016-08-02

Column chromatography was evaluated as a method to obtain organic cation sorption isotherms for environmental solids while using the peak skewness to identify the linear range of the sorption isotherm. Custom packed HPLC columns and standard batch sorption techniques were used to intercompare sorption isotherms and solid-water sorption coefficients (Kd) for four organic cations (benzylamine, 2,4-dichlorobenzylamine, phenyltrimethylammonium, oxytetracycline) with two aluminosilicate clay minerals and one soil. A comparison of Freundlich isotherm parameters revealed isotherm linearity or nonlinearity was not significantly different between column chromatography and traditional batch experiments. Importantly, skewness (a metric of eluting peak symmetry) analysis of eluting peaks can establish isotherm linearity, thereby enabling a less labor intensive means to generate the extensive data sets of linear Kd values required for the development of predictive sorption models. Our findings clearly show that column chromatography can reproduce sorption measures from conventional batch experiments with the benefit of lower labor-intensity, faster analysis times, and allow for consistent sorption measures across laboratories with distinct chromatography instrumentation.

Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

NASA Astrophysics Data System (ADS)

Lazarevic, Natasa; Adnadjevic, Borivoj; Jovanovic, Jelena

2011-07-01

The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.

Hydride compositions

DOEpatents

Lee, Myung W.

1995-01-01

A composition for use in storing hydrogen, and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the hydrogen equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to hydrogen and then heating at a temperature below the softening temperature of any of the. constituents so that their chemical and structural integrity is preserved. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P.sub.H.sbsb.2 and determining H/M from the isothermic function of the composition.

Hydride compositions

DOEpatents

Lee, Myung, W.

1994-01-01

Disclosed are a composition for use in storing hydrogen and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the H equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to H, and then heating below the softening temperature of any of the constituents. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P{sub H}{sub 2} and determining H/M from the isothermic function of the composition.

Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent.

PubMed

Chang, Chia-Chi; Tseng, Jyi-Yeong; Ji, Dar-Ren; Chiu, Chun-Yu; Lu, De-Sheng; Chang, Ching-Yuan; Yuan, Min-Hao; Chang, Chiung-Fen; Chiou, Chyow-San; Chen, Yi-Hung; Shie, Je-Lueng

2015-01-01

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4 (M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g(-1) with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH0) of solution to 5, (2) no adjustment of pH0 with value in 6.04-6.64, and (3) adjusted pH0 = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g(-1), respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol(-1), indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Treatment of radioactive liquid waste (Co-60) by sorption on Zeolite Na-A prepared from Iraqi kaolin.

PubMed

Mustafa, Yasmen A; Zaiter, Maysoon J

2011-11-30

Iraqi synthetic zeolite type Na-A has been suggested as ion exchange material to treat cobalt-60 in radioactive liquid waste which came from neutron activation for corrosion products. Batch experiments were conducted to find out the equilibrium isotherm for source sample. The equilibrium isotherm for radioactive cobalt in the source sample showed unfavorable type, while the equilibrium isotherm for the total cobalt (the radioactive and nonradioactive cobalt) in the source sample showed a favorable type. The ability of Na-A zeolite to remove cobalt from wastewater was checked for high cobalt concentration (822 mg/L) in addition to low cobalt concentration in the source sample (0.093 mg/L). A good fitting for the experimental data with Langmuir equilibrium model was observed. Langmuir constant qm which is related to monolayer adsorption capacity for low and high cobalt concentration was determined to be 0.021 and 140 mg/g(zeolite). The effects of important design variables on the zeolite column performance were studied these include initial concentration, flow rate, and bed depth. The experimental results have shown that high sorption capacity can be obtained at high influent concentration, low flow rate, and high bed depth. Higher column performance was obtained at higher bed depth. Thomas model was employed to predict the breakthrough carves for the above variables. A good fitting was observed with correlation coefficients between 0.915 and 0.985. Copyright © 2011 Elsevier B.V. All rights reserved.

Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

PubMed

Munagapati, Venkata Subbaiah; Kim, Dong-Su

2017-07-01

The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

Gravitational Collapse of Spherical Interstellar Clouds

NASA Astrophysics Data System (ADS)

Ogino, Shinya; Tomisaka, Kohji; Nakamura, Fumitaka

1999-10-01

In this paper, the gravitational collapse of spherical interstellar clouds is discussed based on hydro\\-dynamical simulations. The evolution is divided into two phases: former runaway collapse phase, in which the central density increases greatly on a finite time scale, and later contraction, associated with accretion onto a newborn star. The initial density distribution is expressed using a ratio of the gravitational force to the pressure force alpha . The equation of state for a polytropic gas is used. The central, high-density part of the solution converges on a self-similar solution, which was first derived for the runaway collapse by Larson and Penston (LP). In the later accretion phase, gas behaves like a particle, and the infall speed is accelerated by the gravity of the central object. The solution at this stage is qualitatively similar to the inside-out similarity solutions first found by Shu. However, it is shown that the gas-inflow (accretion) rate is time-dependent, in contrast to the constant rate of the inside-out similarity solutions. For isothermal models in which the pressure is important, 1 <~ alpha <~ 3.35, the accretion rate reaches its maximum when the central part, which obeys the LP solution, contracts and accretes. On the other hand, in isothermal models in which gravity is dominant, alpha >~ 3.35, the accretion becomes most active at the epoch when the outer part of the cloud falls onto the center. The effect of the non-isothermal equation of state is discussed.

Rapid screening method for male DNA by using the loop-mediated isothermal amplification assay.

PubMed

Kitamura, Masashi; Kubo, Seiji; Tanaka, Jin; Adachi, Tatsushi

2017-08-12

Screening for male-derived biological material from collected samples plays an important role in criminal investigations, especially those involving sexual assaults. We have developed a loop-mediated isothermal amplification (LAMP) assay targeting multi-repeat sequences of the Y chromosome for detecting male DNA. Successful amplification occurred with 0.5 ng of male DNA under isothermal conditions of 61 to 67 °C, but no amplification occurred with up to 10 ng of female DNA. Under the optimized conditions, the LAMP reaction initiated amplification within 10 min and amplified for 20 min. The LAMP reaction was sensitive at levels as low as 1-pg male DNA, and a quantitative LAMP assay could be developed because of the strong correlation between the reaction time and the amount of template DNA in the range of 10 pg to 10 ng. Furthermore, to apply the LAMP assay to on-site screening for male-derived samples, we evaluated a protocol using a simple DNA extraction method and a colorimetric intercalating dye that allows detection of the LAMP reaction by evaluating the change in color of the solution. Using this protocol, samples of male-derived blood and saliva stains were processed in approximately 30 min from DNA extraction to detection. Because our protocol does not require much hands-on time or special equipment, this LAMP assay promises to become a rapid and simple screening method for male-derived samples in forensic investigations.

Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution.

PubMed

Kazak, Omer; Eker, Yasin Ramazan; Akin, Ilker; Bingol, Haluk; Tor, Ali

2017-10-01

This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH pzc ) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L) -1/n ] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.

Magnetic basement and crustal structure in the Arabia-Eurasia collision zone from a combined gravity and magnetic model

NASA Astrophysics Data System (ADS)

Mousavi, Naeim; Ebbing, Jörg

2017-04-01

In this study, we investigate the magnetic basement and crustal structure in the region of Iran by inverse and forward modeling of aeromagnetic data and gravity data. The main focus is on the definition of the magnetic top basement. The combination of multiple shallow magnetic sources and an assumed shallow Curie isotherm depth beneath the Iranian Plateau creates a complex magnetic architecture over the area. Qualitative analysis, including pseudo gravity, wavelength filtering and upward continuation allowed a first separation of probable deep and shallow features, like the Sanandaj Sirjan zone, Urumieh Dokhtar Magmatic Assemblage, Kopet Dagh structural unit and Central Iran domain. In the second step, we apply inverse modeling to generate an estimate of the top basement geometry. The initial model was established from top basement to (a) constant depth of 25 km and (b) Moho depth. The inversion result was used as starting model for more detailed modelling in 3D to evaluate the effect of susceptibility heterogeneities in the crust. Subsequently, the model was modified with respect to tectonic and geological characterization of the region. Further modification of model in regards more details of susceptibility distribution was led to separating upper crust to different magnetic domains. In addition, we refined the top basement geometry by using terrestrial gravity observation as well. The best fitting model is consistent with the Curie isotherm depth as the base of magnetization. The Curie isotherm was derived from independent geophysical-petrological model.

An attempt to model the probability of growth and aflatoxin B1 production of Aspergillus flavus under non-isothermal conditions in pistachio nuts.

PubMed

Aldars-García, Laila; Ramos, Antonio J; Sanchis, Vicente; Marín, Sonia

2015-10-01

Human exposure to aflatoxins in foods is of great concern. The aim of this work was to use predictive mycology as a strategy to mitigate the aflatoxin burden in pistachio nuts postharvest. The probability of growth and aflatoxin B1 (AFB1) production of aflatoxigenic Aspergillus flavus, isolated from pistachio nuts, under static and non-isothermal conditions was studied. Four theoretical temperature scenarios, including temperature levels observed in pistachio nuts during shipping and storage, were used. Two types of inoculum were included: a cocktail of 25 A. flavus isolates and a single isolate inoculum. Initial water activity was adjusted to 0.87. Logistic models, with temperature and time as explanatory variables, were fitted to the probability of growth and AFB1 production under a constant temperature. Subsequently, they were used to predict probabilities under non-isothermal scenarios, with levels of concordance from 90 to 100% in most of the cases. Furthermore, the presence of AFB1 in pistachio nuts could be correctly predicted in 70-81 % of the cases from a growth model developed in pistachio nuts, and in 67-81% of the cases from an AFB1 model developed in pistachio agar. The information obtained in the present work could be used by producers and processors to predict the time for AFB1 production by A. flavus on pistachio nuts during transport and storage. Copyright © 2015 Elsevier Ltd. All rights reserved.

Near-equilibrium desorption of helium films

NASA Astrophysics Data System (ADS)

Weimer, M.; Housley, R. M.; Goodstein, D. L.

1987-10-01

The thermal desorption of helium films in the presence of their equilibrium vapor is studied experimentally for small but rapid departures from ambient temperature. The results are analyzed within the framework of a quasithermodynamic phenomenological model based on detailed balance. Under the usual experimental conditions, isothermal desorption at the temperature of the substrate is a general prediction of the model which seems to be substantiated. For realistic adsorption isotherms the time evolution of the net desorption flux nevertheless appears to be governed by a highly nonlinear equation. In such circumstances, a number of characteristic relaxation times may be identified. These time scales are distinct from, and in general unrelated to, the coverage-dependent mean lifetime of an atom on the surface. To characterize the overall nonlinear evolution towards steady state, a global time scale, defined in terms of both initial- and steady-state properties, is introduced to summarize the experimental data. Internal evidence suggests a criterion for judging when collisions among desorbed atoms are unimportant. When this condition is satisfied, data for near-equilibrium desorption agree well with the predictions of the model. Combining our results with earlier data at higher substrate temperatures and different ambient conditions, the overall picture is consistent with scaling properties implied by the theory. We show that the values of the parameters deduced from a Frenkel-Arrhenius parametrization of the global relaxation times, as well as a variety of other aspects of desorption kinetics, are actually consequences of the shape of the equilibrium adsorption isotherm.

Posttest REALP4 analysis of LOFT experiment L1-3A

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, J.R.; Holmstrom, H.L.O.

This report presents selected results of posttest RELAP4 modeling of LOFT loss-of-coolant experiment L1-3A, a double-ended isothermal cold leg break with lower plenum emergency core coolant injection. Comparisons are presented between the pretest prediction, the posttest analysis, and the experimental data. It is concluded that pressurizer modeling is important for accurately predicting system behavior during the initial portion of saturated blowdown. Using measured initial conditions rather than nominal specified initial conditions did not influence the system model results significantly. Using finer nodalization in the reactor vessel improved the prediction of the system pressure history by minimizing steam condensation effects. Unequalmore » steam condensation between the downcomer and core volumes appear to cause the manometer oscillations observed in both the pretest and posttest RELAP4 analysis.« less

ALARIC: An algorithm for constructing arbitrarily complex initial density distributions with low particle noise for SPH/SPMHD applications

NASA Astrophysics Data System (ADS)

Vela Vela, Luis; Sanchez, Raul; Geiger, Joachim

2018-03-01

A method is presented to obtain initial conditions for Smoothed Particle Hydrodynamic (SPH) scenarios where arbitrarily complex density distributions and low particle noise are needed. Our method, named ALARIC, tampers with the evolution of the internal variables to obtain a fast and efficient profile evolution towards the desired goal. The result has very low levels of particle noise and constitutes a perfect candidate to study the equilibrium and stability properties of SPH/SPMHD systems. The method uses the iso-thermal SPH equations to calculate hydrodynamical forces under the presence of an external fictitious potential and evolves them in time with a 2nd-order symplectic integrator. The proposed method generates tailored initial conditions that perform better in many cases than those based on purely crystalline lattices, since it prevents the appearance of anisotropies.

Isothermal transitions of a thermosetting system

NASA Technical Reports Server (NTRS)

Gillham, J. K.; Benci, J. A.; Noshay, A.

1974-01-01

A study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures - namely, the maximum glass transition temperature of the thermoset system and the glass transition temperature of the material at its gel point. Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur. Methods for determining the time to gel and the time to vitrify, and also the two above-mentioned critical isothermal temperatures, have been developed. The time to gel obeyed the Arrhenius relationship, whereas the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of the critical isothermal temperatures.

The analysis of isotherms of radionuclides sorption by inorganic sorbents

NASA Astrophysics Data System (ADS)

Bykova, E. P.; Nedobukh, T. A.

2017-09-01

The isotherm of cesium sorption by an inorganic sorbent based on granulated glauconite obtained in a wide cesium concentrations range was mathematically treated using Langmuir, Freundlich and Redlich-Peterson sorption models. The algorithms of mathematical treatment of experimental data using these models were described; parameters of all isotherms were determined. It was shown that estimating the correctness of various sorption models relies not only on the correlation coefficient values but also on the closeness of the calculated and experimental data. Various types of sorption sites were found as a result of mathematical treatment of the isotherm of cesium sorption. The algorithm was described and calculation of parameters of the isotherm was performed under the assumption that simultaneous sorption on all three types of sorption sites occurs in accordance with Langmuir isotherm.

The effect of natural and anthropogenic factors on sorption of copper in chernozem

NASA Astrophysics Data System (ADS)

Bauer, Tatiana; Minkina, Tatiana; Mandzhieva, Saglara; Pinskii, David; Linnik, Vitaly; Sushkova, Svetlana

2016-04-01

The aim of this work was to study the effect of the attendant anions and particle-size distribution on the adsorption of copper by ordinary chernozem. Solutions of HM nitrates, acetates, chlorides, and sulfates were used to study the effect of the chemical composition of added copper salts on the adsorption of copper by an ordinary chernozem. Samples of the soil sieved through a 1-mm sieve in the natural ionic form and soil fraction with different particle size (clay - the particle with size < 1μm and physical clay < 10 μm) were treated with solutions of the corresponding copper salts at a soil : solution ratio of 1:10. The concentrations of the initial copper solutions were 0.02, 0.05, 0.08, 0.1, 0.3, 0.5, and 1.0 mM/L. The range of Cu2+ concentrations in the studied system covers different geochemical situations corresponding to the actual levels of soil contamination with the metal under study. The suspensions were shaken for 1 h, left to stand for 24 h, and then filtered. The contents of the HM in the filtrates were determined by atomic absorption spectrometry (AAS). The contents of the adsorbed copper cations were calculated from the difference between the metal concentrations in the initial and equilibrium solutions. The isotherms of copper adsorption from the metal nitrate, chloride, and sulfate solutions have near linear shapes and, hence, can be satisfactorily described by a Henry or Freundlich equation: Cads = KH •Ceq.(1) Cads = KF •Ceqn,(2) where Cadsis the content of the adsorbed cations, mM/kg soil;Ceq is the concentration of copper in the equilibrium solution, mM/L; KH and KF denote the Henry and Freundlich adsorption coefficients, respectively, kg/L. The isotherm of Cu2+ adsorption by ordinary chernozem from acetate solutions is described by the Langmuir equation: Cads = C∞ÊLC / (1 + ÊLC), (3) where Cadsis the content of the adsorbed cations, mM/kg soil;C∞ is the maximum adsorption of the HM, mM/kg soil; ÊL is the affinity constant, L/mM; C is the concentration of the HM in the equilibrium solution, mM/L. According to the values of KH, the binding strength of the copper cations adsorbed from different salt solutions decreases in the series: Cu(Ac)2(1880,5± 76,2) > CuCl2(1442,8±113,5) > Cu(NO3)2(911,4 ± 31,1) >> CuSO4(165,3 ± 12,9). Thus, copper is most strongly adsorbed from the acetate solution and least strongly from the sulfate solution. The adsorption of copper by clay and physical clay fractions from the ordinary chernozem was of limited character and followed the (3) equation. In the particle-size fractions separated from the soils, the concentrations of copper decreased with the decreasing particle size. The values of ÊL and C∞characterizing the HM adsorption by the chernozem and its particle-size fractions formed the following sequence: clay (80,20±20,29 and 28,45±0,46 > physical clay (58,20±14,54 and 22,15±1,22) > entire soil (38,80±12,33 and 17,58±3,038). This work was supported by the Russian Ministry of Education and Science, project no. 5.885.2014/K, Russian Foundation for Basic Research, projects no. 14-05-00586 À

A 3D view of magnetic stripes at Pito Deep: implications for the thermal history of fast-spreading lower oceanic crust

NASA Astrophysics Data System (ADS)

Maher, S. M.; Gee, J. S.; Doran, A. K.; Gess, M.; Cheadle, M. J.; Coogan, L. A.; Gillis, K. M.; John, B. E.

2017-12-01

There is no consensus on how the lower oceanic crust cools at fast-spreading centers and, correspondingly, how the isotherms change with depth. Sufficient heat extraction above the axial magma lens might result in shallowly dipping fossil isotherms off axis, while significant removal of heat laterally in the lower crust would be accompanied by steeper isotherms. These end-member models and additional intermediate models may be accompanied by distinctive geochemical, mineralogical, and textural changes, but the record of geomagnetic reversals can provide key complementary information on the thermal history of the lower oceanic crust. In particular, the location of a reversal boundary with depth over exposed sections of gabbroic rock should reveal the fossil pattern of cooling below 600°C. Tectonic exposures at Pito Deep reveal cross sections of two magnetic reversals recorded in gabbroic rock formed at the fast-spreading East Pacific Rise during chron C2A (3.58­-2.581 Ma). High quality magnetic anomaly data, using a new miniature total field sensor, were acquired on 11 Sentry dives centered over 2An.2n (3.22­-3.11 Ma) and another over the young end of 2An.3n (3.58­-3.33 Ma). The local bathymetry is complex, so we have constructed several forward models based on isotherms predicted by different end-member models to determine which best fits the magnetic anomaly data. Initial results are difficult to reconcile with models of deep crustal cooling and steep isotherms within a few km of the axis. Instead they favor a model in which gabbroic rocks cool over long time periods, resulting in a polarity offset between the gabbros and the overlying dikes and lavas extending for several km. This difference in polarity is supported by magnetization inversions, calculated for a series of horizontal laminae using the Occam inversion (Constable et al., 1987). Additional confirmation comes from the magnetic remanence of nearly 400 gabbroic samples (most partially or fully oriented) retrieved by Jason II. Preliminary thermal demagnetization results provide evidence of multiple magnetization components in many samples, generally consistent with the presence of isochron boundaries between normal and reverse polarities inferred from the anomaly data.

Biosorption of Cr(VI) by Ceratocystis paradoxa MSR2 Using Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology

PubMed Central

Ramalingam, Chidambaram

2015-01-01

This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L−1, initial Cr(VI) concentration of 62.5 mg L−1 and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO3. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 μm using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed. PMID:25822726

Thermomechanical Fatigue Damage/Failure Mechanisms in SCS-6/Timetal 21S [0/90](Sub S) Composite

NASA Technical Reports Server (NTRS)

Castelli, Michael G.

1994-01-01

The thermomechanical fatigue (TMF) deformation, damage, and life behaviors of SCS6/Timetal 21S (0/90)s were investigated under zero-tension conditions. In-phase (IP) and out-of-phase (OP) loadings were investigated with a temperature cycle from 150 to 650 deg C. An advanced TMF test technique was used to quantify mechanically damage progression. The technique incorporated explicit measurements of the macroscopic (1) isothermal static moduli at the temperature extremes of the TMF cycle and (2) coefficient of thermal expansion (CTE) as functions of the TMF cycles. The importance of thermal property degradation and its relevance to accurate post-test data analysis and interpretation is briefly addressed. Extensive fractography and metallography were conducted on specimens from failed and interrupted tests to characterize the extent of damage at the microstructure level. Fatigue life results indicated trends analogous to those established for similar unidirectional(0) reinforced titanium matrix composite systems. High stress IP and mid to low stress OP loading conditions were life-limiting in comparison to maximum temperature isothermal conditions. Dominant damage mechanisms changed with cycle type. Damage resulting from IP TMF conditions produced measurable decreases in static moduli but only minimal changes in the CTE. Metallography on interrupted and failed specimens revealed extensive (0) fiber cracking with sparse matrix damage. No surface initiated matrix cracks were present. Comparable OP TMF conditions initiated environment enhanced surface cracking and matrix cracking initiated at (90) fiber/matrix (F/M) interfaces. Notable static moduli and CTE degradations were measured. Fractography and metallography revealed that the transverse cracks originating from the surface and (90) F/M interfaces tended to converge and coalesce at the (0) fibers.

Discovery of a Novel General Anesthetic Chemotype Using High-throughput Screening

PubMed Central

McKinstry-Wu, Andrew R.; Bu, Weiming; Rai, Ganesha; Lea, Wendy A.; Weiser, Brian P.; Liang, David F.; Simeonov, Anton; Jadhav, Ajit; Maloney, David J.; Eckenhoff, Roderic G.

2014-01-01

Background The development of novel anesthetics has historically been a process of combined serendipity and empiricism, with most recent new anesthetics developed via modification of existing anesthetic structures. Methods Using a novel high-throughput screen employing the fluorescent anesthetic 1-aminoanthracene (1-AMA) and apoferritin as a surrogate for on-pathway anesthetic protein target(s), we screened a 350,000 compound library for competition with 1-AMA-apoferritin binding. Hit compounds meeting structural criteria had their binding affinities for apoferritin quantified with isothermal titration calorimetry and were tested for γ-aminobutyric acid type A-receptor binding using a flunitrazepam binding assay. Chemotypes with a strong presence in the top 700 and exhibiting activity via isothermal titration calorimetry were selected for medicinal chemistry optimization including testing for anesthetic potency and toxicity in an in vivo Xenopus laevis tadpole assay. Compounds with low toxicity and high potency were tested for anesthetic potency in mice. Results From an initial chemical library of over 350,000 compounds, we identified 2,600 compounds that potently inhibited 1-AMA binding to apoferritin. A subset of compounds chosen by structural criteria (700) was successfully reconfirmed using the initial assay. Based upon a strong presence in both the initial and secondary screens the 6-phenylpyridazin-3(2H)-one chemotype was assessed for anesthetic activity in tadpoles. Medicinal chemistry efforts identified four compounds with high potency and low toxicity in tadpoles, two were found to be effective novel anesthetics in mice. Conclusions We demonstrate the first use of a high-throughput screen to successfully identify a novel anesthetic chemotype and show mammalian anesthetic activity for members of that chemotype. PMID:25603205

Effectiveness of mineral soil to adsorb the natural occurring radioactive material (norm), uranium and thorium

NASA Astrophysics Data System (ADS)

Amir, Muhammad Nur Iman; Ismail, Nurul Izzatiafifi; Wood, Ab. Khalik; Saat, Ahmad; Hamzah, Zaini

2015-04-01

A study has been performed on U-soil and Th-soil adsorption of three types of soil collected from Selangor State of Malaysia which are Saujana Putra, Bukit Changgang and Jenderam Hilir. In this study, natural radionuclide (U and Th) soil adsorption based on batch experiments with various initial concentrations of the radionuclide elements were carried out. Parameters that were set constant include pH at 5;amount of soil used was 5 g each, contact time was 24 hour and different initial concentration for each solution of U and Th which is 5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, 25 mg/L and 40 mg/L were used. The Kd values for each type of soil were determined in this batch experiments which was based on US-EPA method, in order to estimate adsorption capacity of the soil.The Kd values of Th found higher than Kd values of U for all of the soil samples, and the highest was found on the soil collected from Bukit Changgang. The soil clay content was one of factors to influence the adsorption of both U and Th from dilute initial solution. The U-soil and Th-soil adsorption process for all the soil samples studied are generally obeying unimolecular layer Langmuir isotherm model. From Langmuir isotherm, the maximum adsorption capacity for U was 0.393mg/g and for Th was 1.53 mg/g for the soil that was taken from Bukit Changgang. From the study, it suggested that the soil from Bukit Changgang applicable as potential enhanced barrier for site disposing waste containing U and Th.

Effectiveness of mineral soil to adsorb the natural occurring radioactive material (norm), uranium and thorium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amir, Muhammad Nur Iman; Ismail, Nurul Izzatiafifi; Wood, Ab. Khalik, E-mail: khalik@salam.uitm.edu.my

2015-04-29

A study has been performed on U-soil and Th-soil adsorption of three types of soil collected from Selangor State of Malaysia which are Saujana Putra, Bukit Changgang and Jenderam Hilir. In this study, natural radionuclide (U and Th) soil adsorption based on batch experiments with various initial concentrations of the radionuclide elements were carried out. Parameters that were set constant include pH at 5;amount of soil used was 5 g each, contact time was 24 hour and different initial concentration for each solution of U and Th which is 5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, 25 mg/L and 40 mg/L were used. The K{sub d}more » values for each type of soil were determined in this batch experiments which was based on US-EPA method, in order to estimate adsorption capacity of the soil.The K{sub d} values of Th found higher than Kd values of U for all of the soil samples, and the highest was found on the soil collected from Bukit Changgang. The soil clay content was one of factors to influence the adsorption of both U and Th from dilute initial solution. The U-soil and Th-soil adsorption process for all the soil samples studied are generally obeying unimolecular layer Langmuir isotherm model. From Langmuir isotherm, the maximum adsorption capacity for U was 0.393mg/g and for Th was 1.53 mg/g for the soil that was taken from Bukit Changgang. From the study, it suggested that the soil from Bukit Changgang applicable as potential enhanced barrier for site disposing waste containing U and Th.« less

Three-Dimensional Structure of Thermohaline Staircases in the Tropical North Atlantic and Their Effect on Acoustic Propagation

DTIC Science & Technology

2012-12-01

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943–5000 8. PERFORMING ORGANIZATION REPORT NUMBER 9...experiment initially designed to test pressure at the base of an ocean, by inserting a narrow heat-conducting pipe vertically to draw water to the...tgα ≈ tgαT (6) Wall thus hypothesized that the interface should align with isotherms but not necessarily isohalines. An observational test was

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the gravitational-deceleration initiation of the phase transition of gas to a Bose condensate

NASA Astrophysics Data System (ADS)

Rivlin, L. A.

2008-01-01

A scenario of the experiment on the observation of the isothermal Bose condensation of cooled gas with increasing the concentration of atoms caused by the deceleration of a vertical atomic beam in the gravitational field resulting in a decrease in the phase transition critical temperature below the gas temperature is considered. Coherent phenomena accompanying the evolution of the Bose condensate during further beam deceleration are pointed out.

Initial Parameter Estimation for Inverse Thermal Analysis of Ti-6Al-4V Deep Penetration Welds

DTIC Science & Technology

2014-05-16

theory, for the case of deep-penetration welding, is simulation of the coupling of keyhole formation, melting, fluid flow in the weld melt pool and...isothermal boundaires, e.g., TTB and TM. A specific procedure for interpolation, however, has not been considered. For the present study, the close ...Clarendon Press, Oxford, 2nd ed, 374, 1959. 19. R. Rai, J.W. Elmer, T.A. Palmer, T. DebRoy, Heat Transfer and Fluid Flow During Keyhole Mode Laser Welding

ASCA Temperature Maps for Merging and Relaxed Clusters and Physics of the Cluster Gas

NASA Technical Reports Server (NTRS)

Markevitch, M.; Sarazin, C.; Nevalainen, J.; Vikhlinin, A.; Forman, W.

1999-01-01

ASCA temperature maps for several galaxy clusters undergoing strong mergers will be presented. From these maps, it is possible to estimate velocities of the colliding subclusters. I will discuss several interesting implications of these estimates for the physics of the cluster gas and the shape of the gravitational potential. I will also present temperature maps and profiles for several relaxed clusters selected for X-ray mass determination, and present the mass values derived without the assumption of isothermality. The accurate mass-temperature and luminosity-temperature relations will be discussed. This talk will review how AXAF will revolutionize X-ray astronomy through its radically better imaging and spectroscopic resolution. Examples from many fields of astrophysics will be given.

Physical aging effects on the compressive linear viscoelastic creep of IM7/K3B composite

NASA Technical Reports Server (NTRS)

Veazie, David R.; Gates, Thomas S.

1995-01-01

An experimental study was undertaken to establish the viscoelastic behavior of 1M7/K3B composite in compression at elevated temperature. Creep compliance, strain recovery and the effects of physical aging on the time dependent response was measured for uniaxial loading at several isothermal conditions below the glass transition temperature (T(g)). The IM7/K3B composite is a graphite reinforced thermoplastic polyimide with a T(g) of approximately 240 C. In a composite, the two matrix dominated compliance terms associated with time dependent behavior occur in the transverse and shear directions. Linear viscoelasticity was used to characterize the creep/recovery behavior and superposition techniques were used to establish the physical aging related material constants. Creep strain was converted to compliance and measured as a function of test time and aging time. Results included creep compliance master curves, physical aging shift factors and shift rates. The description of the unique experimental techniques required for compressive testing is also given.

Debranching and temperature-cycled crystallization of waxy rice starch and their digestibility.

PubMed

Zeng, Feng; Ma, Fei; Gao, Qunyu; Yu, Shujuan; Kong, Fansheng; Zhu, Siming

2014-11-26

Slowly digestible starch (SDS) was obtained through debranched waxy rice starch and subsequent crystallization under isothermal and temperature-cycled conditions. Temperature-cycled crystallization of dual 4/-20 °C produced a higher yield of SDS product than isotherm crystallization. Crystal structure of SDS products changed from A-type to a mixture of B and V-type X-ray diffraction patterns. The relative crystallinity was higher in the temperature-cycled samples than that of isotherm. Attenuated total reflectance Fourier transform infrared spectroscopy suggested that the peripheral regions of isothermal storage starch were better organized than temperature-cycles. Temperature cycling induced higher onset temperature for melting of crystals than isothermal storage under a differential scanning calorimeter. The cycled temperature storage induced a greater amount of SDS than the isothermal storage. Copyright © 2014 Elsevier Ltd. All rights reserved.

Disintegration of cruciform and G-quadruplex structures during the course of helicase-dependent amplification (HDA).

PubMed

Li, Dawei; Lv, Bei; Zhang, Hao; Lee, Jasmine Yiqin; Li, Tianhu

2015-04-15

Unlike chemical damages on DNA, physical alterations of B-form of DNA occur commonly in organisms that serve as signals for specified cellular events. Although the modes of action for repairing of chemically damaged DNA have been well studied nowadays, the repairing mechanisms for physically altered DNA structures have not yet been understood. Our current in vitro studies show that both breakdown of stable non-B DNA structures and resumption of canonical B-conformation of DNA can take place during the courses of isothermal helicase-dependent amplification (HDA). The pathway that makes the non-B DNA structures repairable is presumably the relieving of the accumulated torsional stress that was caused by the positive supercoiling. Our new findings suggest that living organisms might have evolved this distinct and economical pathway for repairing their physically altered DNA structures. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isotherm ranking and selection using thirteen literature datasets involving hydrophobic organic compounds.

PubMed

Matott, L Shawn; Jiang, Zhengzheng; Rabideau, Alan J; Allen-King, Richelle M

2015-01-01

Numerous isotherm expressions have been developed for describing sorption of hydrophobic organic compounds (HOCs), including "dual-mode" approaches that combine nonlinear behavior with a linear partitioning component. Choosing among these alternative expressions for describing a given dataset is an important task that can significantly influence subsequent transport modeling and/or mechanistic interpretation. In this study, a series of numerical experiments were undertaken to identify "best-in-class" isotherms by refitting 10 alternative models to a suite of 13 previously published literature datasets. The corrected Akaike Information Criterion (AICc) was used for ranking these alternative fits and distinguishing between plausible and implausible isotherms for each dataset. The occurrence of multiple plausible isotherms was inversely correlated with dataset "richness", such that datasets with fewer observations and/or a narrow range of aqueous concentrations resulted in a greater number of plausible isotherms. Overall, only the Polanyi-partition dual-mode isotherm was classified as "plausible" across all 13 of the considered datasets, indicating substantial statistical support consistent with current advances in sorption theory. However, these findings are predicated on the use of the AICc measure as an unbiased ranking metric and the adoption of a subjective, but defensible, threshold for separating plausible and implausible isotherms. Copyright © 2015 Elsevier B.V. All rights reserved.

Discontinuous precipitation in a Cd-6 at.% Ag alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manna, I.; Bala, P.K.; Pabi, S.K.

1996-11-01

Discontinuous precipitation (DP) in a Cd-6 at.% Ag alloy has been investigated for the first time. The precipitate phase maintains a lamellar morphology and statistically constant interlamellar spacing under a given isothermal condition in the temperature range studied (333--523 K). The interlamellar spacing increases with an increase in isothermal temperature. The reaction front velocity registers a typical C-curve variation with the inverse of temperature. The reaction rate is maximum at 470 K. The predicted upper limit of DP occurrence in this alloy is 23 K lower than the concerned equilibrium solvus temperature. Continuous precipitation accompanies DP at all temperatures, especiallymore » beyond a certain time, and adversely affects the growth kinetics of DP colonies by reducing the local chemical driving force and/or posing physical hindrance to the reaction front migration. An extensive kinetic analysis of DP using the models by Turnbull, Aaronson and Liu, and Petermann and Hornbogen has yielded the grain boundary chemical diffusivity data in Cd-6 At.% Ag for the first time, the activation energy of which lies in the range 55--77 kJ/mol.« less

Preliminary enrichment and separation of genistein and apigenin from extracts of pigeon pea roots by macroporous resins.

PubMed

Liu, Wei; Zhang, Su; Zu, Yuan-Gang; Fu, Yu-Jie; Ma, Wei; Zhang, Dong-Yang; Kong, Yu; Li, Xiao-Juan

2010-06-01

Enrichment and separation of genistein and apigenin from extracts of pigeon pea roots were studied using eleven macroporous resins with different physical and chemical properties. ADS-5 resin showed the maximum effectiveness among the tested resins. The solute affinity towards ADS-5 resin at different temperatures was described in terms of Langmuir and Freundlich isotherms, and the equilibrium experimental data were well-fitted to the two isotherms. In order to optimize the operating parameters for separating genistein and apigenin, dynamic adsorption and desorption tests were carried out. After one run treatment with ADS-5 resin, the contents of genistein and apigenin in the product were 9.36-fold and 11.09-fold increased with recovery yields of 89.78% and 93.41%, respectively. The process achieved easy and effective enrichment and separation of genistein and apigenin by using ADS-5 resin, and it is a promising basis for large-scale preparation of genistein and apigenin from pigeon pea or other plants extracts. (c) 2010 Elsevier Ltd. All rights reserved.

Density distribution function of a self-gravitating isothermal compressible turbulent fluid in the context of molecular clouds ensembles

NASA Astrophysics Data System (ADS)

Donkov, Sava; Stefanov, Ivan Z.

2018-03-01

We have set ourselves the task of obtaining the probability distribution function of the mass density of a self-gravitating isothermal compressible turbulent fluid from its physics. We have done this in the context of a new notion: the molecular clouds ensemble. We have applied a new approach that takes into account the fractal nature of the fluid. Using the medium equations, under the assumption of steady state, we show that the total energy per unit mass is an invariant with respect to the fractal scales. As a next step we obtain a non-linear integral equation for the dimensionless scale Q which is the third root of the integral of the probability distribution function. It is solved approximately up to the leading-order term in the series expansion. We obtain two solutions. They are power-law distributions with different slopes: the first one is -1.5 at low densities, corresponding to an equilibrium between all energies at a given scale, and the second one is -2 at high densities, corresponding to a free fall at small scales.

The Isothermal Dendritic Growth Experiment

NASA Technical Reports Server (NTRS)

Glicksman, M. E.; Koss, M. B.; Malarik, D. C.

1998-01-01

The growth of dendrites is one of the commonly observed forms of solidification encountered when metals and alloys freeze under low thermal gradients, as occurs in most casting and welding processes. In engineering alloys, the details of the dendritic morphology directly relates to important material responses and properties. Of more generic interest, dendritic growth is also an archetypical problem in morphogenesis, where a complex pattern evolves from simple starting conditions. Thus, the physical understanding and mathematical description of how dendritic patterns emerge during the growth process are of interest to both scientists and engineers. The Isothermal Dendritic Growth Experiment (IDGE) is a basic science experiment designed to measure, for a fundamental test of theory, the kinetics and morphology of dendritic growth without complications induced by gravity-driven convection. The IDGE, a collaboration between Rensselaer Polytechnic Institute, in Troy NY, and NASA's Lewis Research Center (LeRC) was developed over a ten year period from a ground-based research program into a space flight experiment. Important to the success of this flight experiment was provision of in situ near-real-time teleoperations during the spaceflight experiment.

Adsorption isotherms and kinetics studies of malachite green on chitin hydrogels.

PubMed

Tang, Hu; Zhou, Weijie; Zhang, Lina

2012-03-30

A chitin hydrogel with concentration 3 wt% (CG3) was successfully prepared from chitin solution dissolved in 8 wt% NaOH/4 wt% urea aqueous system at low temperature by crosslinking with 5 wt% epichlorohydrin. The experimental results revealed that CG3 exhibited high efficiency to remove dye (malachite green) from aqueous solution, as a result of their microporous structure, large surface area and affinity on the dye. The equilibrium process was described well by the Langmuir isotherm model, showing a monolayer adsorption. From kinetic experiments, the adsorption process followed the pseudo-second-order kinetic model, indicating that the overall rate of dye uptake could be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The activation energy calculated from Arrhenius equation and the result of SEM and FTIR indicated that the adsorption of malachite green on the CG3 was physical process. This work provided an attractive adsorbent for removing of the hazardous materials from wastewater. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Parallel numerical modeling of hybrid-dimensional compositional non-isothermal Darcy flows in fractured porous media

NASA Astrophysics Data System (ADS)

Xing, F.; Masson, R.; Lopez, S.

2017-09-01

This paper introduces a new discrete fracture model accounting for non-isothermal compositional multiphase Darcy flows and complex networks of fractures with intersecting, immersed and non-immersed fractures. The so called hybrid-dimensional model using a 2D model in the fractures coupled with a 3D model in the matrix is first derived rigorously starting from the equi-dimensional matrix fracture model. Then, it is discretized using a fully implicit time integration combined with the Vertex Approximate Gradient (VAG) finite volume scheme which is adapted to polyhedral meshes and anisotropic heterogeneous media. The fully coupled systems are assembled and solved in parallel using the Single Program Multiple Data (SPMD) paradigm with one layer of ghost cells. This strategy allows for a local assembly of the discrete systems. An efficient preconditioner is implemented to solve the linear systems at each time step and each Newton type iteration of the simulation. The numerical efficiency of our approach is assessed on different meshes, fracture networks, and physical settings in terms of parallel scalability, nonlinear convergence and linear convergence.

Brazing characteristics of a Zr-Ti-Cu-Fe eutectic alloy filler metal for Zircaloy-4

NASA Astrophysics Data System (ADS)

Lee, Jung G.; Lim, C. H.; Kim, K. H.; Park, S. S.; Lee, M. K.; Rhee, C. K.

2013-10-01

A Zr-Ti-Cu-Fe quaternary eutectic alloy was employed as a new Be-free brazing filler metal for Zircaloy-4 to supersede physically vapor-deposited Be coatings used conventionally with several disadvantages. The quaternary eutectic composition of Zr58Ti16Cu10Fe16 (at.%) showing a low melting temperature range from 832 °C to 853 °C was designed by a partial substitution of Zr with Ti based on a Zr-Cu-Fe ternary eutectic system. By applying an alloy ribbon with the determined composition, a highly reliable joint was obtained with a homogeneous formation of predominantly grown α-Zr phases owing to a complete isothermal solidification, exhibiting strength higher than that of Zircaloy-4. The homogenization of the joint was rate-controlled by the diffusion of the filler elements (Ti, Cu, and Fe) into the Zircaloy-4 base metal, and the detrimental segregation of the Zr2Fe phase in the central zone was completely eliminated by an isothermal holding at a brazing temperature of 920 °C for 10 min.

Modeling of Non-isothermal Austenite Formation in Spring Steel

NASA Astrophysics Data System (ADS)

Huang, He; Wang, Baoyu; Tang, Xuefeng; Li, Junling

2017-12-01

The austenitization kinetics description of spring steel 60Si2CrA plays an important role in providing guidelines for industrial production. The dilatometric curves of 60Si2CrA steel were measured using a dilatometer DIL805A at heating rates of 0.3 K to 50 K/s (0.3 °C/s to 50 °C/s). Based on the dilatometric curves, a unified kinetics model using the internal state variable (ISV) method was derived to describe the non-isothermal austenitization kinetics of 60Si2CrA, and the abovementioned model models the incubation and transition periods. The material constants in the model were determined using a genetic algorithm-based optimization technique. Additionally, good agreement between predicted and experimental volume fractions of transformed austenite was obtained, indicating that the model is effective for describing the austenitization kinetics of 60Si2CrA steel. Compared with other modeling methods of austenitization kinetics, this model, which uses the ISV method, has some advantages, such as a simple formula and explicit physics meaning, and can be probably used in engineering practice.

Stoichiometric network theory for nonequilibrium biochemical systems.

PubMed

Qian, Hong; Beard, Daniel A; Liang, Shou-dan

2003-02-01

We introduce the basic concepts and develop a theory for nonequilibrium steady-state biochemical systems applicable to analyzing large-scale complex isothermal reaction networks. In terms of the stoichiometric matrix, we demonstrate both Kirchhoff's flux law sigma(l)J(l)=0 over a biochemical species, and potential law sigma(l) mu(l)=0 over a reaction loop. They reflect mass and energy conservation, respectively. For each reaction, its steady-state flux J can be decomposed into forward and backward one-way fluxes J = J+ - J-, with chemical potential difference deltamu = RT ln(J-/J+). The product -Jdeltamu gives the isothermal heat dissipation rate, which is necessarily non-negative according to the second law of thermodynamics. The stoichiometric network theory (SNT) embodies all of the relevant fundamental physics. Knowing J and deltamu of a biochemical reaction, a conductance can be computed which directly reflects the level of gene expression for the particular enzyme. For sufficiently small flux a linear relationship between J and deltamu can be established as the linear flux-force relation in irreversible thermodynamics, analogous to Ohm's law in electrical circuits.

Non-enzymatic browning kinetics analysed through water-solids interactions and water mobility in dehydrated potato.

PubMed

Acevedo, Nuria C; Schebor, Carolina; Buera, Pilar

2008-06-01

Non-enzymatic browning (NEB) development was studied in dehydrated potato at 70°C. It was related to the macroscopic and molecular properties and to water-solid interactions over a wide range of water activities. Time resolved (1)H NMR, thermal transitions and water sorption isotherms were evaluated. Although non-enzymatic browning could be detected in the glassy state; colour development was higher in the supercooled state. The reaction rate increased up to a water content of 26g/100g of solids (aw=0.84) and then decreased at higher water contents, concomitantly with the increase of water proton mobility. The joint analyses of NEB kinetics, water sorption isotherm and proton relaxation behaviour made it evident that the point at which the reaction rate decreased, after a maximum value, could be related to the appearance of highly mobile water. The results obtained in this work indicate that the prediction of chemical reaction kinetics can be performed through the integrated analysis of water sorption, water and solids mobility and the physical state of the matrix. Copyright © 2007 Elsevier Ltd. All rights reserved.

Biosorption and desorption of Cd2+ from wastewater by dehydrated shreds of Cladophora fascicularis

NASA Astrophysics Data System (ADS)

Deng, Liping; Zhu, Xiaobin; Su, Yingying; Su, Hua; Wang, Xinting

2008-02-01

The adsorption and desorption of algae Cladophora fascicularis and their relation with initial Cd2+ concentration, initial pH, and co-existing ions were studied. Adsorption equilibrium and biosorption kinetics were established from batch experiments. The adsorption equilibrium was adequately described by the Langmuir isotherm, and biosorption kinetics was in pseudo-second order model. The experiment on co-existing ions showed that the biosorption capacity of biomass decreased with an increasing concentration of competing ions. Desorption experiments indicated that EDTA was efficient desorbent for recovery from Cd2+. With high capacities of metal biosorption and desorption, the biomass of Cladophora fascicularis is promising as a cost-effective biosorbent for the removal of Cd2+ from wastewater.

Development of a loop-mediated isothermal amplification (LAMP) assay for rapid screening of ticks and fleas for spotted fever group rickettsia

PubMed Central

Martin, Jaclyn; Carrillo, Yisel; Talley, Justin L.; Ochoa-Corona, Francisco M.

2018-01-01

Background The importance of tick and flea-borne rickettsia infections is increasingly recognized worldwide. While increased focus has shifted in recent years to the development of point-of-care diagnostics for various vector-borne diseases in humans and animals, little research effort has been devoted to their integration into vector surveillance and control programs, particularly in resource-challenged countries. One technology which may be helpful for large scale vector surveillance initiatives is loop-mediated isothermal amplification (LAMP). The aim of this study was to develop a LAMP assay to detect spotted fever group (SFG) rickettsia DNA from field-collected ticks and fleas and compare with published end-point PCR results. Methodology/Principal findings A Spotted Fever Group rickettsia-specific loop-mediated isothermal amplification (SFGR-LAMP) assay was developed using primers based on a region of the R. rickettsii 17kDa protein gene. The sensitivity, specificity, and reproducibility of the assay were evaluated. The assay was then compared with the results of end-point PCR assays for pooled tick and flea samples obtained from field-based surveillance studies. The sensitivity of the SFGR-LAMP assay was 0.00001 ng/μl (25μl volume) which was 10 times more sensitive than the 17kDa protein gene end-point PCR used as the reference method. The assay only recognized gDNA from SFG and transitional group (TRG) rickettsia species tested but did not detect gDNA from typhus group (TG) rickettsia species or closely or distantly related bacterial species. The SFGR-LAMP assay detected the same positives from a set of pooled tick and flea samples detected by end-point PCR in addition to two pooled flea samples not detected by end-point PCR. Conclusions/significance To our knowledge, this is the first study to develop a functional LAMP assay to initially screen for SFG and TRG rickettsia pathogens in field-collected ticks and fleas. With a high sensitivity and specificity, the results indicate the potential use as a field-based surveillance tool for tick and flea-borne rickettsial pathogens in resource-challenged countries. PMID:29390021

Development of a loop-mediated isothermal amplification (LAMP) assay for rapid screening of ticks and fleas for spotted fever group rickettsia.

PubMed

Noden, Bruce H; Martin, Jaclyn; Carrillo, Yisel; Talley, Justin L; Ochoa-Corona, Francisco M

2018-01-01

The importance of tick and flea-borne rickettsia infections is increasingly recognized worldwide. While increased focus has shifted in recent years to the development of point-of-care diagnostics for various vector-borne diseases in humans and animals, little research effort has been devoted to their integration into vector surveillance and control programs, particularly in resource-challenged countries. One technology which may be helpful for large scale vector surveillance initiatives is loop-mediated isothermal amplification (LAMP). The aim of this study was to develop a LAMP assay to detect spotted fever group (SFG) rickettsia DNA from field-collected ticks and fleas and compare with published end-point PCR results. A Spotted Fever Group rickettsia-specific loop-mediated isothermal amplification (SFGR-LAMP) assay was developed using primers based on a region of the R. rickettsii 17kDa protein gene. The sensitivity, specificity, and reproducibility of the assay were evaluated. The assay was then compared with the results of end-point PCR assays for pooled tick and flea samples obtained from field-based surveillance studies. The sensitivity of the SFGR-LAMP assay was 0.00001 ng/μl (25μl volume) which was 10 times more sensitive than the 17kDa protein gene end-point PCR used as the reference method. The assay only recognized gDNA from SFG and transitional group (TRG) rickettsia species tested but did not detect gDNA from typhus group (TG) rickettsia species or closely or distantly related bacterial species. The SFGR-LAMP assay detected the same positives from a set of pooled tick and flea samples detected by end-point PCR in addition to two pooled flea samples not detected by end-point PCR. To our knowledge, this is the first study to develop a functional LAMP assay to initially screen for SFG and TRG rickettsia pathogens in field-collected ticks and fleas. With a high sensitivity and specificity, the results indicate the potential use as a field-based surveillance tool for tick and flea-borne rickettsial pathogens in resource-challenged countries.

Effective removal of cesium from wastewater solutions using an innovative low-cost adsorbent developed from sewage sludge molten slag.

PubMed

Khandaker, Shahjalal; Toyohara, Yusaku; Kamida, Seiya; Kuba, Takahiro

2018-06-01

This study investigates the effective removal of cesium (Cs) from aqueous solution using sewage sludge molten (SSM) slag that has undergone the surface modification with alkali (NaOH) hydrothermal treatment. The raw and modified slags were characterised systematically using the BET method, the FESEM, the XRF, the XRD spectroscopy and the CEC analysis to understand the physicochemical changes of the materials, and its sensitivity to Cs ions adsorption. Batch adsorption experiments were carried out to investigate the effects of adsorbent dose, contact time, solution pH, different initial Cs concentrations, temperature and the effect of competitive ions on Cs adsorption. The adsorption isotherm, kinetic and thermodynamic studies were also evaluated based on the experimental results. A higher Cs removal efficiency of almost 100% (for 20-100 mg/L of initial concentration) was achieved by the modified SSM slag, and the maximum adsorption capacity was found to be 52.36 mg/g. Several types of synthetic zeolites such as zeolite X, zeolite Y, zeolite A, and sodalite were formed on surface of the modified slag through the modification process which might be enhanced the Cs adsorption capacity. Kinetic parameters were fitted by the pseudo-second order model. The adsorption isotherms data of modified slag were well-fitted to the Langmuir (R 2  = 0.989) and Freundlich isotherms (R 2  = 0.988). The thermodynamic studies indicated that the adsorption process by the modified slag was spontaneous and exothermic. In the competitive ions effect, the modified slag effectively captured the Cs ion in the presence of Na + and K + , especially at their lower concentrations. Moreover, the modified slag was reused for several cycles after the successful elution process with an appropriate eluting agent (0.5 M H 2 SO 4 ), without deterioration of its original performance. Therefore, the SSM modified slag could be effectively used as a low-cost potential adsorbent for high Cs adsorption from wastewater. Copyright © 2018 Elsevier Ltd. All rights reserved.

Highly sensitive fluorescence assay of DNA methyltransferase activity by methylation-sensitive cleavage-based primer generation exponential isothermal amplification-induced G-quadruplex formation.

PubMed

Xue, Qingwang; Lv, Yanqin; Xu, Shuling; Zhang, Yuanfu; Wang, Lei; Li, Rui; Yue, Qiaoli; Li, Haibo; Gu, Xiaohong; Zhang, Shuqiu; Liu, Jifeng

2015-04-15

Site-specific identification of DNA methylation and assay of MTase activity are imperative for determining specific cancer types, provide insights into the mechanism of gene repression, and develop novel drugs to treat methylation-related diseases. Herein, we developed a highly sensitive fluorescence assay of DNA methyltransferase by methylation-sensitive cleavage-based primer generation exponential isothermal amplification (PG-EXPA) coupled with supramolecular fluorescent Zinc(II)-protoporphyrin IX (ZnPPIX)/G-quadruplex. In the presence of DNA adenine methylation (Dam) MTase, the methylation-responsive sequence of hairpin probe is methylated and cleaved by the methylation-sensitive restriction endonuclease Dpn I. The cleaved hairpin probe then functions as a signal primer to initiate the exponential isothermal amplification reaction (EXPAR) by hybridizing with a unimolecular DNA containing three functional domains as the amplification template, producing a large number of G-quadruplex nanostructures by utilizing polymerases and nicking enzymes as mechanical activators. The G-quadruplex nanostructures act as host for ZnPPIX that lead to supramolecular complexes ZnPPIX/G-quadruplex, which provides optical labels for amplified fluorescence detection of Dam MTase. While in the absence of Dam MTase, neither methylation/cleavage nor PG-EXPA reaction can be initiated and no fluorescence signal is observed. The proposed method exhibits a wide dynamic range from 0.0002 to 20U/mL and an extremely low detection limit of 8.6×10(-5)U/mL, which is superior to most conventional approaches for the MTase assay. Owing to the specific site recognition of MTase toward its substrate, the proposed sensing system was able to readily discriminate Dam MTase from other MTase such as M.SssI and even detect the target in a complex biological matrix. Furthermore, the application of the proposed sensing strategy for screening Dam MTase inhibitors was also demonstrated with satisfactory results. This novel method not only provides a promising platform for monitoring activity and inhibition of DNA MTases, but also shows great potentials in biological process researches, drugs discovery and clinical diagnostics. Copyright © 2014 Elsevier B.V. All rights reserved.

Water defluoridation by aluminium oxide-manganese oxide composite material.

PubMed

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, W.; Kan, A.T.; Fu, G.

Neutral organic contaminants commonly reside on the solid portion of soils and sediments. The extent of desorption from these solids determines the fate, reactivity, and toxicity. Numerous researchers have observed that, after an initial exposure of a few days, desorption takes place in two phases, namely, an initial rapid release followed by a long-term resistant phase. Resistant desorption has been highly unpredictable. In this research, the adsorption and desorption of chlorobenzenes, hexachlorobutadiene, and naphthalene have been studied using historically and freshly contaminated bayou sediments from Lake Charles, Louisiana, USA. After an initial release period, both laboratory-spiked and historically contaminated sedimentsmore » from Lake Charles, Louisiana, USA. After an initial release period, both laboratory-spiked and historically contaminated sediments exhibit similar desorption profiles. The simulations compare favorably with previous in situ measurements. All desorption results, both laboratory and field, could reasonably be interpreted using a single irreversible isotherm. Consequences of these results in terms of sediment quality criteria (SQC) are also discussed. Finally, an index of fractional irreversible adsorption is proposed and tested.« less

Statistical Design in Isothermal Aging of Polyimide Resins

NASA Technical Reports Server (NTRS)

Sutter, James K.; Jobe, Marcus; Crane, Elizabeth A.

1995-01-01

Recent developments in research on polyimides for high temperature applications have led to the synthesis of many new polymers. Among the criteria that determines their thermal oxidative stability, isothermal aging is one of the most important. Isothermal aging studies require that many experimental factors are controlled to provide accurate results. In this article we describe a statistical plan that compares the isothermal stability of several polyimide resins, while minimizing the variations inherent in high-temperature aging studies.

Thermal fatigue behaviour for a 316 L type steel

NASA Astrophysics Data System (ADS)

Fissolo, A.; Marini, B.; Nais, G.; Wident, P.

1996-10-01

This paper deals with initiation and growth of cracks produced by thermal fatigue loadings on 316 L steel, which is a reference material for the first wall of the next fusion reactor ITER. Two types of facilities have been built. As for true components, thermal cycles have been repeatedly applied on the surface of the specimen. The first is mainly concerned with initiation, which is detected with a light microscope. The second allows one to determine the propagation of a single crack. Crack initiation is analyzed using the French RCC-MR code procedure, and the strain-controlled isothermal fatigue curves. To predict crack growth, a model previously proposed by Haigh and Skelton is applied. This is based on determination of effective stress intensity factors, which takes into account both plastic strain and crack closure phenomena. It is shown that estimations obtained with such methodologies are in good agreement with experimental data.

Adsorption of NH4+-N on Chinese loess: Non-equilibrium and equilibrium investigations.

PubMed

Xie, Haijian; Wang, Shaoyi; Qiu, Zhanhong; Jiang, Jianqun

2017-11-01

NH 4 + -N is a crucial pollutant in landfill leachate and can be in high concentrations for a long period of time due to anaerobic condition of landfills. The adsorption properties of NH 4 + -N on the Chinese loess were investigated using Batch test. The influences of ammonium concentration, temperature, reaction time, slurry concentration, and pH on the adsorption process are evaluated. Adsorption kinetics and isotherm behaviors were studied by applying different models to the test data to determine the adsorption parameters. The equilibrating duration was shown to be less than 60 min. The data on adsorption kinetics can be well fitted by the pseudo-second-order kinetics model. According to the Langmuir isotherm model, the adsorption capacity of Chinese loess about NH 4 + -N was predicted to be 72.30 mg g -1 . The uptake of NH 4 + -N by Chinese loess was considered to be the type of physical adsorption on the basis of D-R isotherm analysis. The optimal pH and slurry concentration are 4 and 2 g/50 ml, respectively. According to the calculated values of free energy, enthalpy and entropy change, the adsorption process is determined to be exothermic. The disorder of the system appeared lowest at temperature of 308.15 K. The predicted Gibb's free energies also indicate the adsorption process is endothermic and spontaneous. The FTIR spectrum and EDX analysis showed the adsorption process of NH 4 + involves cation exchange and dissolution of calcite. Copyright © 2017 Elsevier Ltd. All rights reserved.

Removal of fluoride from drinking water using aluminum hydroxide coated activated carbon prepared from bark of Morinda tinctoria

NASA Astrophysics Data System (ADS)

Amalraj, Augustine; Pius, Anitha

2017-10-01

The aim of this study is to design and develop a novel cost effective method for fluoride removal, applicable to rural areas of developing countries. Adsorption is widely considered as one of the appropriate technologies for water defluoridation. This study investigates the feasibility of using low-cost biomass based activated carbon from the bark of Morinda tinctoria coated with aluminum hydroxide (AHAC) for water defluoridation, at neutral pH range. Characterization of AHAC was done through IR, SEM with EDAX studies before and after fluoride treatment. The fluoride adsorption capacity of AHAC as a function of contact time, pH and initial fluoride concentration was investigated. The role of co-existing interfering ions also was studied. The isotherm and kinetic models were used to understand the nature of the fluoride adsorption onto AHAC. Freundlich isotherm and intra-particle diffusion were the best-fitting models for the adsorption of fluoride on AHAC. Fluoride adsorption kinetics well fitted with pseudo-second order model. The results showed excellent fluoride adsorption capacity was found to be 26.03 mg g-1 at neutral pH.

Data of furfural adsorption on nano zero valent iron (NZVI) synthesized from Nettle extract.

PubMed

Fazlzadeh, Mehdi; Ansarizadeh, Mohammad; Leili, Mostafa

2018-02-01

Among various water and wastewater treatment methods, adsorption techniques are widely used to remove certain classes of pollutants due to its unique features. Thus, the aim of this data article is to synthesize zero valent iron nanoparticles (NZVI) from Nettle leaf extract by green synthesis method as an environmentally friendly technique, and to evaluate it's efficiency in the removal of furfural from aqueous solutions. The data of possible adsorption mechanism and isotherm of furfural on the synthesized adsorbent are depicted in this data article. The data acquired showed that the adsorption trend follows the pseudo-second order kinetic model and that the Langmuir isotherm was suitable for correlation of equilibrium data with the maximum adsorption capacity of 454.4 mg/g. The information of initial furfural concentration, pH, adsorbent dosage and contact time effects on the removal efficiency are presented. Considering the findings data, the developed nanoparticle from Nettle leaf extract, as a low cost adsorbent, could be considered as promising adsorbent for furfural and probably similar organic pollutants removal from aqueous solutions.

Removal of Hexavalent Chromium by Adsorption on Microwave Assisted Activated Carbon Prepared from Stems of Leucas Aspera

NASA Astrophysics Data System (ADS)

Shanmugalingam, A.; Murugesan, A.

2018-05-01

This study reports adsorption of Cr(VI) ions from aqueous solution using activated carbon that was prepared from stems of Leucas aspera. Eight hundred and fifty watts power of microwave radiation, 12 min of radiation time, 60% of ZnCl2 solution and 24 h of impregnation time are the optimal parameters to prepare efficient carbon effective activated carbon. It was designated as MWLAC (Microwave assisted Zinc chloride activated Leucas aspera carbon). Various adsorption characteristics such as dose of the adsorbent, agitation time, initial Cr(VI) ion concentration, pH of the solution and temperature on adsorption were studied for removal of Cr(VI) ions from aqueous solution by batch mode. Also the equilibrium adsorption was analyzed by the Langmuir, Freundlich, Tempkin and D-R isotherm models. The order of best describing isotherms was given based on R2 value. The pseudo-second-order kinetic model best fitted with the Cr(VI) adsorption data. Thermodynamic parameters were also determined and results suggest that the adsorption process is a spontaneous, endothermic and proceeded with increased randomness.

Polyrhodanine modified anodic aluminum oxide membrane for heavy metal ions removal.

PubMed

Song, Jooyoung; Oh, Hyuntaek; Kong, Hyeyoung; Jang, Jyongsik

2011-03-15

Polyrhodanine was immobilized onto the inner surface of anodic aluminum oxide (AAO) membrane via vapor deposition polymerization method. The polyrhodanine modified membrane was applied to remove heavy metal ions from aqueous solution because polyrhodanine could be coordinated with specific metal ions. Several parameters such as initial metal concentration, contact time and metal species were evaluated systematically for uptake efficiencies of the fabricated membrane under continuous flow condition. Adsorption isotherms of Hg(II) ion on the AAO-polyrhodanine membrane were analyzed with Langmuir and Freundlich isotherm models. The adsorption rate of Hg(II) ion on the membrane was obeyed by a pseudo-second order equation, indicating the chemical adsorption. The maximum removal capacity of Hg(II) ion onto the fabricated membrane was measured to be 4.2 mmol/g polymer. The AAO-polyrhodanine membrane had also remarkable uptake performance toward Ag(I) and Pb(II) ions. Furthermore, the polyrhodanine modified membrane could be recycled after recovery process. These results demonstrated that the polyrhodanine modified AAO membrane provided potential applications for removing the hazardous heavy metal ions from wastewater. Copyright © 2011 Elsevier B.V. All rights reserved.

Biosorption of Pb(II) from aqueous solution by Solanum melongena leaf powder as a low-cost biosorbent prepared from agricultural waste.

PubMed

Yuvaraja, Gutha; Krishnaiah, Nettem; Subbaiah, Munagapati Venkata; Krishnaiah, Abburi

2014-02-01

Solanum melongena leaves are relatively galore and used as inexpensive material. This paper presents the characterization and evaluation of potential of S. melongena leaf powder (SMLP) for removal of Pb(II) from aqueous solution as a function of pH, biomass dosage, initial metal ion concentration, contact time and temperature. Experimental data were analyzed in terms of three kinetic models such as the pseudo-first-order, pseudo-second-order and intraparticle diffusion models and the results showed that the biosorption processes of Pb(II) followed well pseudo-second-order kinetics. Langmuir and Freundlich isotherm models were applied to describe the biosorption process. Langmuir isotherm described the equilibrium data very well, with a maximum monolayer sorption capacity of 71.42 mg/g for Pb(II) ions at 323 K. The biosorption process was spontaneous and endothermic in nature with negative ΔG° (-8.746, -8.509 and -7.983 kJ/mol) and positive value for ΔH° (3.698 kJ/mol). Copyright © 2013 Elsevier B.V. All rights reserved.

Optimizing adsorption of fluoride from water by modified banana peel dust using response surface modelling approach

NASA Astrophysics Data System (ADS)

Bhaumik, Ria; Mondal, Naba Kumar

2016-06-01

The present work highlighted the effective application of banana peel dust (BPD) for removal of fluoride (F-) from aqueous solution. The effects of operating parameters such as pH, initial concentration, adsorbent dose, contact time, agitation speed and temperature were analysed using response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance and t test statistics. Experimental results revealed that BPD has higher F- adsorption capacity (17.43, 26.31 and 39.5 mg/g). Fluoride adsorption kinetics followed pseudo-second-order model with high correlation of coefficient value (0.998). On the other hand, thermodynamic data suggest that adsorption is favoured at lower temperature, exothermic in nature and enthalpy driven. The adsorbents were characterised through scanning electron microscope, Fourier transform infrared spectroscopy and point of zero charges (pHZPC) ranges from pH 6.2-8.2. Finally, error analysis clearly demonstrates that all three adsorbents are well fitted with Langmuir isotherm compared to the other isotherm models. The reusable properties of the material support further development for commercial application purpose.

Synthesis, characterization, and potential application of Mn2+-intercalated bentonite in fluoride removal: adsorption modeling and mechanism evaluation

NASA Astrophysics Data System (ADS)

Mudzielwana, Rabelani; Gitari, Wilson M.; Akinyemi, Segun A.; Msagati, Titus A. M.

2017-12-01

The study synthesizes a low-cost adsorbent made from Mn2+-modified bentonite clay for groundwater defluoridation. The clays were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and Fourier transform infrared techniques. The fluoride adsorption capacity of the modified clay was evaluated using batch experiments. The adsorption kinetics results showed that the optimum fluoride (F-) uptake was achieved within the 30 min' contact time. The data fitted well to pseudo-second-order of reaction kinetics indicating that adsorption of F- occurred via chemisorption. In addition, the adsorption isotherm data fitted well to Langmuir isotherm model indicating that adsorption occurred on a mono-layered surface. Maximum F- removal of 57% was achieved from groundwater with an initial F- concentration of 5.4 mg L-1 and natural pH of 8.6 using adsorbent dosage of 1 g/100 mL. Fluoride adsorption occurred through ligands and ion exchange mechanisms. The synthesized adsorbent was successfully regenerated for up to five times. The study shows that Mn2+-intercalated bentonite clay has potential for application in defluoridation of groundwater.

Recovery of oil from oil-in-water emulsion using biopolymers by adsorptive method.

PubMed

Elanchezhiyan, S Sd; Sivasurian, N; Meenakshi, Sankaran

2014-09-01

In the present study, it is aimed to identify, a low cost sorbent for the recovery of oil from oil-in-water emulsion using biopolymers such as chitin and chitosan. Chitin has the greater adsorption capacity than chitosan due to its hydrophobic nature. The characterizations of chitin and chitosan were done using FTIR, SEM, EDAX, XRD, TGA and DSC techniques. Under batch equilibrium mode, a systematic study was performed to optimize the various equilibrium parameters viz., contact time, pH, dosage, initial concentration of oil, and temperature. The adsorption process reached equilibrium at 40 min of contact time and the percentage removal of oil was found to be higher (90%) in the acidic medium. The Freundlich and Langmuir models were applied to describe the equilibrium isotherms and the isotherm constants were calculated. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated to find out the nature of the sorption mechanism. The kinetic studies were investigated with reaction-based and diffusion-based models. The suitable mechanism for the removal of oil has been established. Copyright © 2014 Elsevier B.V. All rights reserved.

Natural biosorbents (garlic stem and horse chesnut shell) for removal of chromium(VI) from aqueous solutions.

PubMed

Parlayıcı, Şerife; Pehlivan, Erol

2015-12-01

The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions.

Model development of supersonic trough wind with shocks

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.

1972-01-01

The time dependent one dimensional hydrodynamic equations describe the evolution of the thermal plasma flow along closed magnetic field lines outside of the plasmasphere. The convection of the supersonic polar wind onto a closed fieldline results in the assumed formation of collisionless plasma shocks. These shocks move earthward as the field line with its frozen-in plasma remains fixed or contracts with time to smaller L coordinates. The high equatorial plasma temperature (of the order of electron volts) produced by the shock process decreases with time if the flow is isothermal but it will increase if the contraction is under adiabatic conditions. Assuming adiabaticity a peak in the temperature forms at the equator in conjunction with a depression in the ion density. After an initial contraction, if the flux tube drifts to higher L coordinates the direction of the shock motion can be reversed so that the supersonic region will expand along the field line towards the state characterizing the supersonic polar wind. A rapid expansion will lower the equatorial density while the temperature decreases with time under adiabatic but not isothermal conditions.

Removal of Pb (II) ions from aqueous solutions by Cladophora rivularis (Linnaeus) Hoek.

PubMed

Jafari, Naser; Senobari, Zoreh

2012-01-01

Biosorption of Pb(II) using Cladophora rivularis was examined as a function of initial pH heavy metal concentration and temperature. The optimum pH value for the biosorption of lead was 4.0. The adsorption equilibriums were well described by Langmuir and Freundlich isotherm models and it was implied by the results that the C. rivularis biomass is suitable for the development of efficient biosorbent in order to remove Pb(II) from wastewater and to recover it. The high values of correlation coefficient (R(2) = 0.984) demonstrate equilibrium data concerning algal biomass, which is well fitted in Freundlich isotherms model equations. The dimensionless parameter R(L) is found in the range of 0.0639 to 0.1925 (0 < R(L) < 1), which confirms the favorable biosorption process. Fourier transform infra-red (FTIR) spectroscopy of C. rivularis was used to reveal the main function groups of biosorption, which were hydroxyl, amine groups, C-H stretching vibrations of -CH3 and -CH2, and complexation with functional groups. All these results suggest that C. rivularis can be used effectively for removal of Pb(II).

Biosorption of toxic lead (II) ions using tomato waste (Solanum lycopersicum) activated by NaOH

NASA Astrophysics Data System (ADS)

Permatasari, Diah; Heraldy, Eddy; Lestari, Witri Wahyu

2016-02-01

This research present to uptake lead (II) ion from aqueous solutions by activated tomato waste. Biosorbent were characterized by applying Fourier Transform Infrared Spectroscopy (FTIR) and Surface Area Analyzer (SAA). The biosorption investigated with parameters including the concentration of NaOH, effects of solution pH, biosorbent dosage, contact time,and initial metal concentration. Experimental data were analyzed in terms of two kinetic model such us the pseudo-first order and pseudo-second order. Langmuir and Freundlich isotherm models were applied todescribe the biosorption process. According to the experiment, the optimum concentration of NaOH was achieved at 0.1 M. The maximum % lead (II) removal was achieved at pH 4 with 94.5%. Optimum biosorbentdosage were found as 0.1 g/25 mL solution while optimum contact time were found at 75 minutes. The results showed that the biosorption processes of Lead (II) followed pseudo-second order kinetics. Langmuir adsorption isotherm was found fit the adsorption data with amaximum capacity of 24.079 mg/g with anadsorption energy of 28.046 kJ/mol.

Biosorption of six basic and acidic dyes on brown alga Sargassum ilicifolium: optimization, kinetic and isotherm studies.

PubMed

Tabaraki, Reza; Sadeghinejad, Negar

2017-06-01

Biosorption of Methyl Blue (MB), Fuchsin Acid (FA), Rhodamine B (RB), Methylene Blue (MEB), Bromocresol purple (BC) and Methyl Orange (MO) onto Sargassum ilicifolium was studied in a batch system. Effect of dye structure on biosorption by Sargassum ilicifolium was studied to define the correlation between chemical structure and biosorption capacity. Different dye groups such as triarylmethane (MB, FA and BC), monoazo (MO), thiazine (MEB) and xanthene (RB) were studied. At optimum experimental conditions for each dye, biosorption capacity was determined and compared. The results indicate that the chemical structure (triarylmethane, monoazo, thiazine, xanthene), number of sulfonic groups, basicity (element of chromophore group: S, N, O) and molecular weight of dye molecules influence their biosorption capacity. Experimental parameters such as biosorbent dose, pH, contact time, and initial dye concentration were optimized for each dye. The biosorption kinetic data were successfully described by the pseudo second-order model. The biosorption results were also analyzed by the Langmuir and Freundlich isotherms. Finally, biosorption capacities obtained using Sargassum ilicifolium were compared with the ones presented in the literature.

Biosorption of lead (II) ions by NaOH-activated apple (Malus domestica) juice residue

NASA Astrophysics Data System (ADS)

Arimurti, Devita Dwi; Heraldy, Eddy; Lestari, Witri Wahyu

2016-02-01

This research studied the removal of Pb(II) ions from aqueous solutions using NaOH-activated apple (Malus domestica) juice residue. Biosorbent was characterized with Fourier Transform Infrared Spectrophotometer (FTIR), and Surface Area Analyzer (SAA). The effects of biosorbent dosage, pH, contact time and initial metal ion concentration had been investigated in batch-adsorption method. The biosorption kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetics model. Freundlich and Langmuir's isotherm were used to describe the biosorption process. The optimum conditions of Pb(II) adsorption was observed at 60 min of contact time, pH 4, and 0.1 g biosorbent dosage in 25 ml solution. The biosorption kinetics followed the pseudo-second-order kinetic model, resulted biosorption constant rate of 0.184 g.mg-1.min-1. The Langmuir isotherm model exhibited the best fit to experimental data. The maximum biosorption capacity of Pb(II) determined according to the Langmuir model was 90.90 mg.g-1 at 302 K, with the adsorption energy of 26.429 kJ.mol-1.

Chromium (VI) biosorption by Saccharomyces cerevisiae subjected to chemical and thermal treatments.

PubMed

De Rossi, Andrea; Rigon, Magali Rejane; Zaparoli, Munise; Braido, Rafael Dalmas; Colla, Luciane Maria; Dotto, Guilherme Luiz; Piccin, Jeferson Steffanello

2018-05-28

The potential of chemically and thermally treated Saccharomyces cerevisiae as biosorbents for chromium (VI) was investigated in this work. The presence of this toxic metal in industrial effluents is harmful to the environment, so, it is important to develop environmental friendly methods for Cr(VI) removal from these effluents. Biosorption using microorganisms such as S. cerevisiae is a viable treatment option because this biomass is easily available as a residue of fermentation industries. In this study, the affecting variables on Cr(VI) biosorption were studied by constructing biosorption isotherms, using lyophilized yeast subjected to chemical and thermal treatments. S. cerevisiae was able to remove 99.66% of Cr(VI) from effluents by biosorption. The significant variables affecting biosorption were pH, initial Cr(VI) concentration, and contact time. The biosorption isotherms were represented by the Freundlich model for the untreated biomass, BET model for the chemically treated biomass, and Langmuir model for the heat-treated biomass. Thermal treatment increased the biosorption affinity of the biomass for chromium, while the chemical treatment facilitated the formation of a multilayer.

The Formation and Spatiotemporal Progress of the pH Wave Induced by the Temperature Gradient in the Thin-Layer H2O2-Na2S2O3-H2SO4-CuSO4 Dynamical System.

PubMed

Jędrusiak, Mikołaj; Orlik, Marek

2016-03-31

The H2O2-S2O3(2-)-H(+)-Cu(2+) dynamical system exhibits sustained oscillations under flow conditions but reveals only a single initial peak of the indicator electrode potential and pH variation under batch isothermal conditions. Thus, in the latter case, there is no possibility of the coupling of the oscillations and diffusion which could lead to formation of sustained spatiotemporal patterns in this process. However, in the inhomogeneous temperature field, due to dependence of the local reaction kinetics on temperature, spatial inhomogeneities of pH distribution can develop which, in the presence of an appropriate indicator, thymol blue, manifest themselves as the color front traveling along the quasi-one-dimensional reactor. In this work, we describe the experimental conditions under which the above-mentioned phenomena can be observed and present their numerical model based on thermokinetic coupling and spatial coordinate introduced to earlier isothermal homogeneous kinetic mechanism.

Preparation, non-isothermal decomposition kinetics, heat capacity and adiabatic time-to-explosion of NTOxDNAZ.

PubMed

Ma, Haixia; Yan, Biao; Li, Zhaona; Guan, Yulei; Song, Jirong; Xu, Kangzhen; Hu, Rongzu

2009-09-30

NTOxDNAZ was prepared by mixing 3,3-dinitroazetidine (DNAZ) and 3-nitro-1,2,4-triazol-5-one (NTO) in ethanol solution. The thermal behavior of the title compound was studied under a non-isothermal condition by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of NTOxDNAZ is classified as chemical reaction, and the kinetic parameters of the reaction are E(a)=149.68 kJ mol(-1) and A=10(15.81)s(-1). The specific heat capacity of the title compound was determined with continuous C(p) mode of microcalorimeter. The standard mole specific heat capacity of NTOxDNAZ was 352.56 J mol(-1)K(-1) in 298.15K. Using the relationship between C(p) and T and the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion) was obtained.

Single and binary adsorption of heavy metal ions from aqueous solutions using sugarcane cellulose-based adsorbent.

PubMed

Wang, Futao; Pan, Yuanfeng; Cai, Pingxiong; Guo, Tianxiang; Xiao, Huining

2017-10-01

A high efficient and eco-friendly sugarcane cellulose-based adsorbent was prepared in an attempt to remove Pb 2+ , Cu 2+ and Zn 2+ from aqueous solutions. The effects of initial concentration of heavy metal ions and temperature on the adsorption capacity of the bioadsorbent were investigated. The adsorption isotherms showed that the adsorption of Pb 2+ , Cu 2+ and Zn 2+ followed the Langmuir model and the maximum adsorptions were as high as 558.9, 446.2 and 363.3mg·g -1 , respectively, in single component system. The binary component system was better described with the competitive Langmuir isotherm model. The three dimensional sorption surface of binary component system demonstrated that the presence of Pb 2+ decreased the sorption of Cu 2+ , but the adsorption amount of other metal ions was not affected. The result from SEM-EDAX revealed that the adsorption of metal ions on bioadsorbent was mainly driven by coordination, ion exchange and electrostatic association. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kinetic and thermodynamic studies on the adsorption of anionic surfactant on quaternary ammonium cationic cellulose.

PubMed

Zhang, Yuanzhang; Shi, Wenjian; Zhou, Hualan; Fu, Xing; Chen, Xuan

2010-06-01

Removal of anionic surfactants from aqueous solutions by adsorption onto quaternary ammonium cationic cellulose (QACC) was investigated. The effects of solution acidity, initial concentration, adsorption time, and temperature on the adsorption of sodium dodecyl-benzene sulfonate (SDBS), sodium lauryl sulfate (SLS), and sodium dodecyl sulfonate (SDS) were studied. The kinetic experimental data fit well with the pseudo-second-order model; the rate constant of the adsorption increased with temperature. The values of apparent activation energy for the adsorption were calculated as ranging from 10.2 to 17.4 kJ/ mol. The adsorption isotherm can be described by the Langmuir isotherm. The values of thermodynamic parameters (deltaH0, deltaS0, and deltaG0) for the adsorption indicated that this process was spontaneous and endothermic. At 318 K, the saturated adsorption capacities of QACC for SDBS, SLS, and SDS were 1.75, 1.53, and 1.39 mmol/g, respectively. The adsorption process was mainly chemisorption and partially physisorption. The results show that QACC is effective for the removal of anionic surfactants.

Artificial Neural Network Modeling and Genetic Algorithm Optimization for Cadmium Removal from Aqueous Solutions by Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites

PubMed Central

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wei, Xionghui; Shi, Xuedan; Ruan, Wenqian

2017-01-01

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized in the present study by chemical deposition method and were then characterized by various methods, such as Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nZVI/rGO composites prepared were utilized for Cd(II) removal from aqueous solutions in batch mode at different initial Cd(II) concentrations, initial pH values, contact times, and operating temperatures. Response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA) were used for modeling the removal efficiency of Cd(II) and optimizing the four removal process variables. The average values of prediction errors for the RSM and ANN-GA models were 6.47% and 1.08%. Although both models were proven to be reliable in terms of predicting the removal efficiency of Cd(II), the ANN-GA model was found to be more accurate than the RSM model. In addition, experimental data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. It was found that the Cd(II) adsorption was best fitted to the Langmuir isotherm. Examination on thermodynamic parameters revealed that the removal process was spontaneous and exothermic in nature. Furthermore, the pseudo-second-order model can better describe the kinetics of Cd(II) removal with a good R2 value than the pseudo-first-order model. PMID:28772901

Razor clam (Ensis directus) shell as a low-cost adsorbent for the removal of Congo red and Rhodamine B dyes from aqueous solution

NASA Astrophysics Data System (ADS)

Areibat, Lila Elamari Mohamed; Kamari, Azlan

2017-05-01

Wastewater originating from industrial effluents contains many types of pollutants including dyes. Anionic and cationic dyes are very toxic and they can cause several problems to aquatic system. In present study, razor clam shell was used as a potential adsorbent to remove two classes of dyes, namely anionic (Congo red, CR) and cationic (Rhodamine B, RB) dyes from aqueous solution. Batch adsorption experiments were performed to study the effects of three experimental parameters, namely solution pH, adsorbent dosage and initial dye concentration, on adsorption capacity of CR and RB onto razor clam shell. Results indicated that pH 2.0 was optimum pH for adsorbent to adsorb both CR and RB. At an initial concentration of 20 mg/L, the removal percentages of CR and RB were 97% and 38%, respectively. The Freundlich and Langmuir isotherm models were used to describe adsorption behaviour of CR and RB, as well as the relationship between adsorbent and adsorbate. The adsorption equilibrium data were well fitted to Freundlich isotherm model. The separation factor (RL) constants suggest that both CR and RB were favourably adsorbed by razor clam shell. Razor clam shell was characterised by using two techniques, namely Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectrometry (FTIR). Overall, this study suggests that razor clam shell has great potential to be an alternative to expensive adsorbents.

A potential low cost adsorbent for the removal of cationic dyes from aqueous solutions

NASA Astrophysics Data System (ADS)

Uddin, Md. Tamez; Rahman, Md. Arifur; Rukanuzzaman, Md.; Islam, Md. Akhtarul

2017-10-01

This study was aimed at using mango leaf powder (MLP) as a potential adsorbent for the removal of methylene blue (MB) from aqueous solutions. Characterization of the adsorbent was carried out with scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The pH at the point of zero charge of the adsorbent was determined by titration method and was found a value to be 5.6 ± 0.2. Batch studies were performed to evaluate the influence of various experimental parameters like initial solution pH, contact time, initial concentration of dye and adsorbent dosage on the removal of MB. An adsorption-desorption study was carried out resulting the mechanism of adsorption was carried out by electrostatic force of attraction. The adsorption equilibrium time required for the adsorption of MB on MLP was almost 2 h and 85 ± 5% of the total amount of dye uptake was found to occur in the first rapid phase (30 min). The Langmuir and Freundlich isotherm models were used for modeling the adsorption equilibrium. The experimental equilibrium data could be well interpreted by Langmuir isotherm with maximum adsorption capacity of 156 mg/g. To state the sorption kinetics, the fits of pseudo-first-order and pseudo-second-order kinetic models were investigated. It was obtained that the adsorption process followed the pseudo-second-order rate kinetics. The above findings suggest that MLP can be effectively used for decontamination of dye containing wastewater.

Artificial Neural Network Modeling and Genetic Algorithm Optimization for Cadmium Removal from Aqueous Solutions by Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites.

PubMed

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wei, Xionghui; Shi, Xuedan; Ruan, Wenqian

2017-05-17

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized in the present study by chemical deposition method and were then characterized by various methods, such as Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nZVI/rGO composites prepared were utilized for Cd(II) removal from aqueous solutions in batch mode at different initial Cd(II) concentrations, initial pH values, contact times, and operating temperatures. Response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA) were used for modeling the removal efficiency of Cd(II) and optimizing the four removal process variables. The average values of prediction errors for the RSM and ANN-GA models were 6.47% and 1.08%. Although both models were proven to be reliable in terms of predicting the removal efficiency of Cd(II), the ANN-GA model was found to be more accurate than the RSM model. In addition, experimental data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. It was found that the Cd(II) adsorption was best fitted to the Langmuir isotherm. Examination on thermodynamic parameters revealed that the removal process was spontaneous and exothermic in nature. Furthermore, the pseudo-second-order model can better describe the kinetics of Cd(II) removal with a good R² value than the pseudo-first-order model.

Removal of 2,4-D from aqueous solutions by adsorption processes using two biopolymers: chitin and chitosan and their optical properties

NASA Astrophysics Data System (ADS)

El Harmoudi, H.; El Gaini, L.; Daoudi, E.; Rhazi, M.; Boughaleb, Y.; El Mhammedi, M. A.; Migalska-Zalas, A.; Bakasse, M.

2014-07-01

Chitin, extracted primarily from exoskeleton shellfish, is one of the most abundant biopolymer in the world. It is estimated to be produced annually almost as much as cellulose. The development of fishing activities in Morocco (coastline of 3500 km on both the Atlantic and the Mediterranean) induced an important fish industry waste. The aim of this work is to recover chitin, extracted from shellfish waste, and chitosan, produced by deacetylation of chitin, in the adsorption of organic pesticide 2,4-dichlorophenoxyacetate (2,4-D). The chitosan samples were prepared from chitin from crustacean shells. The chitin deacetylation was carried out in aqueous sodium hydroxide. Characterization of chitin and chitosan was performed by infrared spectroscopy, nuclear magnetic resonance and theoretical calculation of UV-Vis spectra and optical parameters. Analysis of theoretical spectra shows a substantial sensitivity to the hydroxyl and amino groups. The presented hydroxyl group in chitin determines the conformation of the molecule and also the stereochemistry of chemical reactions and kinetics. The presence of functional groups causes the substantial changes of both absorption spectra as well as permanent dipole moment. The adsorption of 2,4-D by chitin and chitosan was performed at different pH values, the pesticide-adsorbent contact time and initial pesticide concentration. The adsorption is described by Langmuir-type isotherm and Freundlich-type isotherm. Recovery tests of 2,4-D confirm the initial interest in using chitin and chitosan as a depolluting agent.

Enhanced fluoride adsorption by nano crystalline γ-alumina: adsorption kinetics, isotherm modeling and thermodynamic studies

NASA Astrophysics Data System (ADS)

Chinnakoti, Prathibha; Chunduri, Avinash L. A.; Vankayala, Ranganayakulu K.; Patnaik, Sandeep; Kamisetti, Venkataramaniah

2017-09-01

Nano materials in particular nano oxides with enhanced surface area and an excellent catalytic surface serve as potential adsorbents for defluoridation of water. In the present study nano γ-alumina was synthesized through a simple and low cost, surfactant assisted solution combustion method. As synthesized material was characterized by XRD and FESEM for its phase, size and morphological characteristics. Surface properties have been investigated by BET method. Nano γ-alumina was further used for a detailed adsorption study to remove fluoride from water. Batches of experiments were performed at various experimental conditions such as solution pH, adsorbent dose, initial fluoride concentration and contact time to test the defluoridation ability of γ-alumina. Fluoride Adsorption by nano sized γ-alumina was rapid and reached equilibrium within two hours. The adsorption worked well at pH 4.0, where ˜96 % of fluoride was found to be adsorbed on adsorbent. It was possible to reduce fluoride levels to as low as 0.3 mg/L (within the safe limit of WHO: ≤1.5 mg/L) from an initial fluoride levels of 10 mg/L. This could be achieved using a very small quantity, 1 g/L of γ-alumina at pH 4 within 1 h of contact time. Defluoridation capacity of nano γ-alumina was further investigated by fitting the equilibrium data to various isotherm as well as kinetic models. The present study revealed that γ-alumina could be an efficient adsorbent for treating fluoride contaminated water.

USING ISOTHERMS TO PREDICT GAC'S CAPACITY FOR SYNTHETIC ORGANICS

EPA Science Inventory

This investigation involved operating a pilot granular activated carbon (GAC) plant to obtain capacity data under typical field conditions, determining isotherms for selected synthetic organic chemicals, and comparing the capacity predicted by the isotherm data with the pilot-pla...

A Universal Isotherm Model to Capture Adsorption Uptake and Energy Distribution of Porous Heterogeneous Surface.

PubMed

Ng, Kim Choon; Burhan, Muhammad; Shahzad, Muhammad Wakil; Ismail, Azahar Bin

2017-09-06

The adsorbate-adsorbent thermodynamics are complex as it is influenced by the pore size distributions, surface heterogeneity and site energy distribution, as well as the adsorbate properties. Together, these parameters defined the adsorbate uptake forming the state diagrams, known as the adsorption isotherms, when the sorption site energy on the pore surfaces are favorable. The available adsorption models for describing the vapor uptake or isotherms, hitherto, are individually defined to correlate to a certain type of isotherm patterns. There is yet a universal approach in developing these isotherm models. In this paper, we demonstrate that the characteristics of all sorption isotherm types can be succinctly unified by a revised Langmuir model when merged with the concepts of Homotattic Patch Approximation (HPA) and the availability of multiple sets of site energy accompanied by their respective fractional probability factors. The total uptake (q/q*) at assorted pressure ratios (P/P s ) are inextricably traced to the manner the site energies are spread, either naturally or engineered by scientists, over and across the heterogeneous surfaces. An insight to the porous heterogeneous surface characteristics, in terms of adsorption site availability has been presented, describing the unique behavior of each isotherm type.

AIRS Retrieved Temperature Isotherms over Southern Europe

NASA Image and Video Library

2002-09-08

AIRS Retrieved Temperature Isotherms over Southern Europe viewed from the west, September 8, 2002. The isotherms in this map made from AIRS onboard NASA Aqua satellite data show regions of the same temperature in the atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA00513

A Sixth-Form Teaching Unit on the Langmuir Adsorption Isotherm

ERIC Educational Resources Information Center

Walkley, G. H.

1973-01-01

Presents a teaching unit on the Langmuir absorption isotherm suitable for advanced secondary school chemistry classes. Describes the experimental investigation of the isothermal adsorption of sulfur dioxide on charcoal, and discusses the derivation of the Langmuir equation and some applications. (JR)

Information-to-free-energy conversion: Utilizing thermal fluctuations.

PubMed

Toyabe, Shoichi; Muneyuki, Eiro

2013-01-01

Maxwell's demon is a hypothetical creature that can convert information to free energy. A debate that has lasted for more than 100 years has revealed that the demon's operation does not contradict the laws of thermodynamics; hence, the demon can be realized physically. We briefly review the first experimental demonstration of Maxwell's demon of Szilard's engine type that converts information to free energy. We pump heat from an isothermal environment by using the information about the thermal fluctuations of a Brownian particle and increase the particle's free energy.

Information-to-free-energy conversion: Utilizing thermal fluctuations

PubMed Central

Toyabe, Shoichi; Muneyuki, Eiro

2013-01-01

Maxwell’s demon is a hypothetical creature that can convert information to free energy. A debate that has lasted for more than 100 years has revealed that the demon’s operation does not contradict the laws of thermodynamics; hence, the demon can be realized physically. We briefly review the first experimental demonstration of Maxwell’s demon of Szilard’s engine type that converts information to free energy. We pump heat from an isothermal environment by using the information about the thermal fluctuations of a Brownian particle and increase the particle’s free energy. PMID:27493548

Development of multilayer perceptron networks for isothermal time temperature transformation prediction of U-Mo-X alloys

NASA Astrophysics Data System (ADS)

Johns, Jesse M.; Burkes, Douglas

2017-07-01

In this work, a multilayered perceptron (MLP) network is used to develop predictive isothermal time-temperature-transformation (TTT) models covering a range of U-Mo binary and ternary alloys. The selected ternary alloys for model development are U-Mo-Ru, U-Mo-Nb, U-Mo-Zr, U-Mo-Cr, and U-Mo-Re. These model's ability to predict 'novel' U-Mo alloys is shown quite well despite the discrepancies between literature sources for similar alloys which likely arise from different thermal-mechanical processing conditions. These models are developed with the primary purpose of informing experimental decisions. Additional experimental insight is necessary in order to reduce the number of experiments required to isolate ideal alloys. These models allow test planners to evaluate areas of experimental interest; once initial tests are conducted, the model can be updated and further improve follow-on testing decisions. The model also improves analysis capabilities by reducing the number of data points necessary from any particular test. For example, if one or two isotherms are measured during a test, the model can construct the rest of the TTT curve over a wide range of temperature and time. This modeling capability reduces the cost of experiments while also improving the value of the results from the tests. The reduced costs could result in improved material characterization and therefore improved fundamental understanding of TTT dynamics. As additional understanding of phenomena driving TTTs is acquired, this type of MLP model can be used to populate unknowns (such as material impurity and other thermal mechanical properties) from past literature sources.

Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: characterizing two-step adsorption and partition processes through experimental and modeling approaches.

PubMed

Zhao, Shan; Huang, Gordon; An, Chunjiang; Wei, Jia; Yao, Yao

2015-04-09

The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C12E10) was investigated. The maximum apparent sorption coefficient Kd(*) reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C12E10 surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C12E10 (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C12E10 dose; and a higher initial 12-2-12 gemini dose showed a higher "desorption" rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308K. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorptive removal of microcystin-LR from surface and wastewater using tyre-based powdered activated carbon: Kinetics and isotherms.

PubMed

Mashile, Phodiso P; Mpupa, Anele; Nomngongo, Philiswa N

2018-04-01

Microcystin LR (MC-LR) is a highly toxic compound and it is known for its adverse health effect on both humans and animals. Due to the ineffectiveness of conventional water treatments methods, for the past decades, researchers have been developing cost-effective ways of removing MC-LR from water bodies. This study reports the application of powdered activated carbon (PAC) obtained from the waste tyre for the removal of MC-LR. The choice of the adsorbent was chosen due to its attractive properties. The prepared tyre-based PAC was found to have the large surface area (1111 m 2  g -1 ). The detection of MC-LR was achieved using high performance liquid chromatography (HPLC) coupled with a PDA detector. The experimental parameters (such as optimum pH, dosage and contact time) affecting the removal of MC-LR using tyre based-powdered activated carbon were optimized using response surface methodology (RSM). Maximum removal of MC-LR was achieved under the following optimum conditions; sample pH 4, carbon dosage concentration 10,000 mg L -1 and contact time of 34 min. Under optimum conditions, kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. The optimized method was applied for the removal of MC-LR in wastewater sample. The effluent and influent sample contained initial concentrations ranging from 0.52 to 8.54 μg L -1 and the removal efficiency was 100%. Copyright © 2018 Elsevier Ltd. All rights reserved.

Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms.

PubMed

Wan Ngah, W S; Hanafiah, M A K M

2008-01-01

The efficiency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The effects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27 degrees C. The kinetic study revealed that pseudosecond order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

Biosorption characteristic of Alcaligenes sp. BAPb.1 for removal of lead(II) from aqueous solution.

PubMed

Jin, Yu; Yu, Sumei; Teng, Chunying; Song, Tao; Dong, Liying; Liang, Jinsong; Bai, Xin; Xu, Xiuhong; Qu, Juanjuan

2017-06-01

In this study, strain BAPb.1 was isolated from lead mining area and used as an adsorbent to remove lead(II) ions from aqueous solution. The physicochemical characteristics, heavy metal resistance and antibiotic sensitivity of strain BAPb.1 were investigated. Biosorption capacity was evaluated by batch biosorption experiments, and isothermal characteristics were discussed. Atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectrometry (FTIR) were conducted to explore the mechanism for lead(II) adsorption. Based on morphological and physiological characteristics as well as the phylogenetic analysis of 16S rDNA sequences, strain BAPb.1 was identified as a member of the genus Alcaligenes. It exhibited high resistances to multiple heavy metals such as lead(II), copper(II), zinc(II), nickel(II) and chromium(VI), and to antibiotics such as kanamycin, ampicillin, streptomycin, chloramphenicol, and tetracycline. The optimum conditions for maximum biosorption rate of 85.2% and maximum capacity of 56.8 mg g -1 were found at pH of 5, adsorbent dosage of 1.5 g L -1 (dry weight), initial lead(II) concentration of 100 mg L -1 , and contact time of 30 min at 30 °C. Biosorption isotherms were well fitted with Langmuir isotherm model. Mechanism analysis reveals that the lead(II) ions may exchange with sodium and potassium ions, and the hydroxyl, carbonyl and phosphate groups on the cell surface can chelate the lead(II) ions, therefore, surface adsorption play significant role in the biosorption process.

Comparison of cadmium hydroxide nanowires and silver nanoparticles loaded on activated carbon as new adsorbents for efficient removal of Sunset yellow: Kinetics and equilibrium study.

PubMed

Ghaedi, Mehrorang

2012-08-01

Adsorption of Sunset yellow (SY) onto cadmium hydroxide nanowires loaded on activated carbon (Cd(OH)(2)-NW-AC) and silver nanoparticles loaded on activated carbon (Ag-NP-AC) was investigated. The effects of pH, contact time, amount of adsorbents, initial dye concentration, agitation speed and temperature on Sunset yellow removal on both adsorbents were studied. Following the optimization of variables, the experimental data were fitted to different conventional isotherm models like Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D-R) based on linear regression coefficient R(2) the Langmuir isotherm was found to be the best fitting isotherm model and the maximum monolayer adsorption capacities calculated based on this model for Cd(OH)(2)-NW-AC and Ag-NP-AC were found to be 76.9 and 37.03mg g(-1) at room temperatures, respectively. The experimental fitting of time dependency of adsorption of SY onto both adsorbent shows the applicability of second order kinetic model for interpretation of kinetic data. The pseudo-second order model best fits the adsorption kinetics. Thermodynamic parameters such as enthalpy, entropy, activation energy, sticking probability, and Gibb's free energy changes were also calculated. It was found that the sorption of SY over (Cd(OH)(2)-NW-AC) and (Ag-NP-AC) was spontaneous and endothermic in nature. Efficiency of the adsorbent was also investigated using real effluents and more than 95% SY removal for both adsorbents was observed. Copyright © 2012 Elsevier B.V. All rights reserved.