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Sample records for anaerobic aqueous solutions

  1. Performance of mesophilic anaerobic granules for removal of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    An Chunjiang [Department of Environmental Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); He Yanling [Department of Environmental Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang Guohe, E-mail: gordon.huang@uregina.ca [Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); Sino-Canada Research Academy of Energy and Environmental Studies, North China Electric Power University, Beijing 102206 (China); Liu Yonghong [Department of Environmental and Chemical Engineering, Xi' an Polytechnic University, Xi' an 710048 (China)

    2010-07-15

    The performance of mesophilic anaerobic granules to degrade octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was investigated under various conditions. The results of batch experiments showed that anaerobic granules were capable of removing HMX from aqueous solution with high efficiency. Both biotic and abiotic mechanisms contributed to the removal of HMX by anaerobic granules under mesophilic conditions. Adsorption appeared to play a significant role in the abiotic process. Furthermore, HMX could be biodegraded by anaerobic granules as the sole substrate. After 16 days of incubation, 99.04% and 96.42% of total HMX could be removed by 1 g VSS/L acclimated and unacclimated granules, respectively. Vancomycin, an inhibitor of acetogenic bacteria, caused a significant inhibition of HMX biotransformation, while 2-bromoethanesulfonic acid, an inhibitor of methanogenic bacteria, only resulted in a slight decrease of metabolic activity. The presence of the glucose, as a suitable electron donor and carbon source, was found to enhance the degradation of HMX by anaerobic granules. Our study showed that sulfate had little adverse effects on biotransformation of HMX by anaerobic granules. However, nitrate had significant inhibitory effect on the extent of HMX removal especially in the initial period. This study offered good prospects of using high-rate anaerobic technology in the treatment of munition wastewater.

  2. Carbons prepared from Spartina alterniflora and its anaerobically digested residue by H3PO4 activation: characterization and adsorption of cadmium from aqueous solutions.

    Science.gov (United States)

    Wang, Zhengfang; Nie, Er; Li, Jihua; Zhao, Yongjun; Luo, Xingzhang; Zheng, Zheng

    2011-04-15

    Two series of activated carbons were prepared from Spartina alterniflora and from its anaerobically digested residue by H(3)PO(4) activation at various process conditions, and used as adsorbents for the removal of cadmium (II) in aqueous solutions. The surface areas and pore volumes of carbons were derived from adsorption isotherms (N(2) at 77K). The surface chemistry of carbons was investigated by infrared spectroscopy. Comparison study indicated that physicochemical properties of the activated carbons were strongly dependent not only on activation conditions but also on biopolymer contents of precursors. Several isotherm models were investigated and the adsorption isotherm data were best represented by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 47.85 mg/g at 25 °C. The results showed that the activated carbon produced from S. alterniflora could be employed as a promising adsorbent for removing cadmium (II) from aqueous solutions.

  3. Treatment of Aqueous Solutions

    NARCIS (Netherlands)

    Van Spronsen, J.; Witkamp, G.J.

    2013-01-01

    The invention is directed to a process for the recovery or removal of one or more crystallizable compounds from an aqueous solution containing, apart from the said crystallizable compounds, one or more organic or inorganic scale- forming or scale-inducing materials having a lower solubility in water

  4. Removal of reactive dye Remazol Brilliant Blue R from aqueous solutions by using anaerobically digested sewage sludge based adsorbents

    Directory of Open Access Journals (Sweden)

    Özçimen Didem

    2016-01-01

    Full Text Available In this study, adsorbents were produced from sewage sludge via chemical and thermal activation processes. Experiments were carried out in a tubular furnace at the heating rate of 20˚C min-1 and temperature of 550 ˚C with a nitrogen flow rate of 400 mL min-1 for 1 h. Dye adsorption experiments were performed with Remazol Brilliant Blue R for its several concentrations under batch equilibrium conditions by comparing sewage sludge based adsorbents with raw material and a commercial activated carbon. Maximum adsorption capacities of carbonized sewage sludge (CSWS and activated sewage sludge (ASWS were found as 7.413 mg g-1 and 9.376 mg g-1 for 100 mg L-1 dye solution, whereas commercial activated carbon had a capacity of 11.561 mg g-1. Freundlich and Langmuir isotherms were used to explain the adsorption mechanism together with pseudo-first-order and pseudo-second-order kinetic models. Langmuir isotherm, which had adsorption capacities of 34.60 mg g-1 (CSWS and 72.99 mg g-1 (ASWS, provided better fit to the equilibrium data than that of Freundlich isotherm. Pseudo second-order, model which had adsorption capacities of 7.451 mg g-1 (CSWS and 9.319 mg g-1 (ASWS, was very favorable to explain the adsorption kinetics of the dye with high regression coefficients.

  5. 2010 Water & Aqueous Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Dor Ben-Amotz

    2010-08-13

    Water covers more than two thirds of the surface of the Earth and about the same fraction of water forms the total mass of a human body. Since the early days of our civilization water has also been in the focus of technological developments, starting from converting it to wine to more modern achievements. The meeting will focus on recent advances in experimental, theoretical, and computational understanding of the behavior of the most important and fascinating liquid in a variety of situations and applications. The emphasis will be less on water properties per se than on water as a medium in which fundamental dynamic and reactive processes take place. In the following sessions, speakers will discuss the latest breakthroughs in unraveling these processes at the molecular level: Water in Solutions; Water in Motion I and II; Water in Biology I and II; Water in the Environment I and II; Water in Confined Geometries and Water in Discussion (keynote lecture and poster winners presentations).

  6. Calorimetric studies of macromolecular aqueous solutions

    NARCIS (Netherlands)

    Blandamer, M.J; Cullis, P.M.; Engberts, J.B.F.N.

    1996-01-01

    Both titration and differential scanning microcalorimetric techniques are shown to yield important information concerning the properties of macromolecules in aqueous solution. Application of titration calorimetry is examined in me context of deaggregation of canonic micelles (e.g. hexadecyltrimethyl

  7. Precipitation of neptunium dioxide from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, K E

    1999-12-01

    Tens of thousands of metric tons of highly radioactive, nuclear waste have been generated in the US. Currently, there is no treatment or disposal facility for these wastes. Of the radioactive elements in high-level nuclear waste, neptunium (Np) is of particular concern because it has a long half-life and may potentially be very mobile in groundwaters associated with a proposed underground disposal site at Yucca Mountain, Nevada. Aqueous Np concentrations observed in previous, short-term solubility experiments led to calculated potential doses exceeding proposed long-term regulatory limits. However, thermodynamic data for Np at 25 C showed that these observed aqueous Np concentrations were supersaturated with respect to crystalline NpO{sub 2}. It was hypothesized that NpO{sub 2} is the thermodynamically stable solid phase in aqueous solution, but it is slow to form in an aqueous solution of NpO{sub 2}{sup +} on the time scale of previous experiments. The precipitation of NpO{sub 2} would provide significantly lower aqueous Np concentrations leading to calculated doses below proposed regulatory limits. To test this hypothesis, solubility experiments were performed at elevated temperature to accelerate any slow precipitation kinetics. Ionic NpO{sub 2}{sup +} (aq) was introduced into very dilute aqueous solutions of NaCl with initial pH values ranging from 6 to 10. The reaction vessels were placed in an oven and allowed to react at 200 C until steady-state aqueous Np concentrations were observed. In all cases, aqueous Np concentrations decreased significantly from the initial value of 10{sup {minus}4} M. The solids that formed were analyzed by x-ray powder diffraction, x-ray absorption spectroscopy, and scanning electron microscopy. The solids were determined to be high-purity crystals of NpO{sub 2}. This is the first time that crystalline NpO{sub 2} has been observed to precipitate from NpO{sub 2}{sup +}(aq) in near-neutral aqueous solutions. The results obtained

  8. Hydrophobic Solvation: Aqueous Methane Solutions

    Science.gov (United States)

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  9. Aqueous Solution Chemistry on Mars

    Science.gov (United States)

    Quinn, R.; Hecht, M.; Kounaves, S.; Young, S.; West, S.; Fisher, A.; Grunthaner, P.

    2007-12-01

    Currently en route to Mars, the Phoenix mission carries four wet chemistry cells designed to perform basic solution chemistry on martian soil. The measurement objectives are typical of those that would be performed on an unknown sample on Earth, including detection of common anions and cations, total conductivity, pH, redox potential, cyclic voltammetry (CV), etc. Both the challenge and the novelty arise from the necessity to perform these measurements with severely constrained resources in a harsh and (literally) alien environment. Sensors for all measurements are integrated into a common "beaker," with the ability to perform a two-point calibration of some sensors using a pair of low-concentration solutions. Sulfate measurement is performed with a crude titration. While most measurements use ion selective electrodes, halide interferences are resolved by independent chronopotentiometry (CP) measurements. No preconditioning of the soil-water mixture is possible, nor is any physical characterization of the introduced soil sample beyond coarse visual inspection. Among the idiosyncrasies of the measurement is the low external pressure, which requires that the analysis be performed close to the boiling point of water under an atmosphere consisting almost entirely of water vapor. Despite these liabilities, however, extensive laboratory characterization has validated the basic approach, and protocols for both CV and CP have been developed and tested. Enhancing the value of the measurement is the suite of coordinated observations, such as microscopy and evolved gas analysis, to be performed by other Phoenix instruments.

  10. Water & Aqueous Solutions. Final Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-08-09

    The Gordon Research Conference (GRC) on Water & Aqueous Solutions was held at Holderness School, New Hampshire, 8/4/02 thru 8/9/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  11. Zeolites as alcohol adsorbents from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Cekova Blagica

    2006-01-01

    Full Text Available The potential usage of zeolites as adsorbents for the removal of organic molecules from water was investigated in a series of experiments with aqueous solutions of lower alcohols. This could represent a simple solution to the problem of cleaning up industrial wastewater as well as recovering valuable chemicals at relatively low costs. Adsorption isotherms of the Langmuir type were applied, and calculations showed that the amount of propanol adsorbed on silicalite corresponded to approximately 70% of the pore volume. The adsorption process is simple, and recovery of the more concentrated products is easily done by heat treatment and/or at lowered pressures. Adsorption experiments with aqueous acetone showed that silicalite had approximately the same adsorption capacity for acetone as for n-propanol. Heats of adsorption were determined calorimetrically.

  12. Aqueous solution dispersement of carbon nanotubes

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2011-01-01

    Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

  13. OPTICAL PROPERTIES OF CARBAMIDE AQUEOUS SOLUTIONS

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    E. V. Avramenko

    2016-03-01

    Full Text Available Subject of Research. The paper presents the results of measurements of refractometric properties (refractive index n, its temperature factor dn/dt and the ultraviolet spectral absorption in carbonic acid diamide aqueous solutions (carbamide depending on solid residue mass fraction md = 0-50 % and on temperaturet = 10-70 °C.Method of Research. Laboratory methods ofliquid-phase medium refractometry and ultraviolet spectrophotometry were applied for the research. We carried out computational modeling of electronic states spectrum for the carbonic acid diamide molecule and theoretical calculation of the fundamental electronic absorption of the molecule in the ultraviolet wavelenght region.Main Results. We have established that the solution concentration md has a nonlinear character and may be represented by the quadratic polynomial with the error Δn= ± 0,0005. We have shown the refractive indexdependence on temperature n(t changes in linear fashion att = 10-70 °C.At that, the inclination of lines n(t increases at the increase of md; so, the temperature factor dn/dt may be approximated by the quadratic polynomial. Transmission spectra of solutions in the spectral region λ= 225-760 nm have no special features except for the sharp edge in the short-wavelength region; the fundamental electronic absorptionis responsible for it. We have established that dispersion dependences of the refraction index n(λ;md in aqueous solutions of carbamide at λ= 360-760 nm and at md = 0-50 % may be calculated with the satisfactory error without additional adjustable parameters from the ultraviolet absorption data in terms of the one-dimentional oscillator Lorentz model.PracticalRelevance. Representedmeasurements of carbonic acid diamide aqueous solutions optical properties may be applied for the adjustment and calibration of commercial refractometers at processing lines of the AdBlue reagent manufacture for the selective catalytic reduction (SCR of motor transport

  14. Density of aqueous solutions of CO2

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Julio E.

    2001-10-10

    In this report, we present a numerical representation for the partial molar volume of CO2 in water and the calculation of the corresponding aqueous solution density. The motivation behind this work is related to the importance of having accurate representations for aqueous phase properties in the numerical simulation of carbon dioxide disposal into aquifers as well as in geothermal applications. According to reported experimental data the density of aqueous solutions of CO2 can be as much as 2-3% higher than pure water density. This density variation might produce an influence on the groundwater flow regime. For instance, in geologic sequestration of CO2, convective transport mixing might occur when, several years after injection of carbon dioxide has stopped, the CO2-rich gas phase is concentrated at the top of the formation, just below an overlaying caprock. In this particular case the heavier CO2 saturated water will flow downward and will be replaced by water with a lesser CO2 content.

  15. ADM1-based modeling of anaerobic digestion of swine manure fibers pretreated with aqueous ammonia soaking

    DEFF Research Database (Denmark)

    Jurado, Esperanza; Gavala, Hariklia N.; Skiadas, Ioannis

    2012-01-01

    that the AAS had on the efficiency of the anaerobic digestion of manure. Kinetic parameters were estimated by fitting of the model to data from manure fed digesters. The model was able to satisfactorily simulate the behaviour of digesters fed with manure. However, the model predictions were poorer...... fibers. In the present study, mesophilic anaerobic digestion of AAS pretreated manure fibers was tested in CSTR-type digesters fed with swine manure and/or a mixture of swine manure and AAS pretreated manure fibers. The Anaerobic Digestion Model No.1 (ADM1) was used for the prediction of the effect......Anaerobic digestion of manure fibers present challenges due to their low biodegradability. Aqueous ammonia soaking (AAS) and subsequent ammonia removal has been tested as a simple and cheap method to disrupt the lignocellulose and increase the methane potential and the biogas productivity of manure...

  16. Aqueous Solution Vessel Thermal Model Development II

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    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-28

    The work presented in this report is a continuation of the work described in the May 2015 report, “Aqueous Solution Vessel Thermal Model Development”. This computational fluid dynamics (CFD) model aims to predict the temperature and bubble volume fraction in an aqueous solution of uranium. These values affect the reactivity of the fissile solution, so it is important to be able to calculate them and determine their effects on the reaction. Part A of this report describes some of the parameter comparisons performed on the CFD model using Fluent. Part B describes the coupling of the Fluent model with a Monte-Carlo N-Particle (MCNP) neutron transport model. The fuel tank geometry is the same as it was in the May 2015 report, annular with a thickness-to-height ratio of 0.16. An accelerator-driven neutron source provides the excitation for the reaction, and internal and external water cooling channels remove the heat. The model used in this work incorporates the Eulerian multiphase model with lift, wall lubrication, turbulent dispersion and turbulence interaction. The buoyancy-driven flow is modeled using the Boussinesq approximation, and the flow turbulence is determined using the k-ω Shear-Stress-Transport (SST) model. The dispersed turbulence multiphase model is employed to capture the multiphase turbulence effects.

  17. Speciation in aqueous solutions of nitric acid.

    Science.gov (United States)

    Hlushak, S; Simonin, J P; De Sio, S; Bernard, O; Ruas, A; Pochon, P; Jan, S; Moisy, P

    2013-02-28

    In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments.

  18. Multistep nucleation of nanocrystals in aqueous solution

    Science.gov (United States)

    Loh, N. Duane; Sen, Soumyo; Bosman, Michel; Tan, Shu Fen; Zhong, Jun; Nijhuis, Christian A.; Král, Petr; Matsudaira, Paul; Mirsaidov, Utkur

    2017-01-01

    The nucleation and growth of solids from solutions impacts many natural processes and is fundamental to applications in materials engineering and medicine. For a crystalline solid, the nucleus is a nanoscale cluster of ordered atoms that forms through mechanisms still poorly understood. In particular, it is unclear whether a nucleus forms spontaneously from solution via a single- or multiple-step process. Here, using in situ electron microscopy, we show how gold and silver nanocrystals nucleate from supersaturated aqueous solutions in three distinct steps: spinodal decomposition into solute-rich and solute-poor liquid phases, nucleation of amorphous nanoclusters within the metal-rich liquid phase, followed by crystallization of these amorphous clusters. Our ab initio calculations on gold nucleation suggest that these steps might be associated with strong gold-gold atom coupling and water-mediated metastable gold complexes. The understanding of intermediate steps in nuclei formation has important implications for the formation and growth of both crystalline and amorphous materials.

  19. Aqueous Solutions of Ionic Liquids: Microscopic Assembly.

    Science.gov (United States)

    Vicent-Luna, Jose Manuel; Dubbeldam, David; Gómez-Álvarez, Paula; Calero, Sofia

    2016-02-01

    Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure-property relationships of such systems is hence desirable. One of the crucial molecular-level interactions that influences the macroscopic behavior is hydrogen bonding. In this work, we conduct molecular dynamics simulations to investigate the effects of ionic liquids on the hydrogen-bond network of water in dilute aqueous solutions of ionic liquids with various combinations of cations and anions. Calculations are performed for imidazolium-based cations with alkyl chains of different lengths and for a variety of anions, namely, [Br](-), [NO3](-), [SCN](-) [BF4](-), [PF6](-), and [Tf2N](-). The structure of water and the water-ionic liquid interactions involved in the formation of a heterogeneous network are analyzed by using radial distribution functions and hydrogen-bond statistics. To this end, we employ the geometric criterion of the hydrogen-bond definition and it is shown that the structure of water is sensitive to the amount of ionic liquid and to the anion type. In particular, [SCN](-) and [Tf2N](-) were found to be the most hydrophilic and hydrophobic anions, respectively. Conversely, the cation chain length did not influence the results.

  20. Terahertz absorption of dilute aqueous solutions.

    Science.gov (United States)

    Heyden, Matthias; Tobias, Douglas J; Matyushov, Dmitry V

    2012-12-21

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  1. Heterogeneous nucleation of aspartame from aqueous solutions

    Science.gov (United States)

    Kubota, Noriaki; Kinno, Hiroaki; Shimizu, Kenji

    1990-03-01

    Waiting times, the time from the instant of quenching needed for a first nucleus to appear, were measured at constant supercoolings for primary nucleation of aspartame (α-L-aspartyl-L-phenylalanine methylester) from aqueous solutions, which were sealed into glass ampoules (solution volume = 3.16 cm 3). Since the waiting time became shorter by filtering the solution prior to quenching, the nucleation was concluded to be heterogeneously induced. The measured waiting time consisted of two parts: time needed for the nucleus to grow to a detactable size (growth time) and stochastic time needed for nucleation (true waiting time). The distribution of the true waiting time, is well explained by a stochastic model, in which nucleation is regarded to occur heterogeneously and in a stochastic manner by two kinds of active sites. The active sites are estimated to be located on foreign particles in which such elements as Si, Al and Mg were contained. The amount of each element is very small in the order of magnitude of ppb (mass basis) of the whole solution. The growth time was correlated with the degree of supercooling.

  2. Functionalized polymers for binding to solutes in aqueous solutions

    Science.gov (United States)

    Smith, Barbara F.; Robison, Thomas W.

    2006-11-21

    A functionalized polymer for binding a dissolved molecule in an aqueous solution is presented. The polymer has a backbone polymer to which one or more functional groups are covalently linked. The backbone polymer can be such polymers as polyethylenimine, polyvinylamine, polyallylamine, and polypropylamine. These polymers are generally water-soluble, but can be insoluble when cross-linked. The functional group can be for example diol derivatives, polyol derivatives, thiol and dithiol derivatives, guest-host groups, affinity groups, beta-diphosphonic acids, and beta-diamides

  3. "Switchable water": aqueous solutions of switchable ionic strength.

    Science.gov (United States)

    Mercer, Sean M; Jessop, Philip G

    2010-04-26

    "Salting out" is a standard method for separating water-soluble organic compounds from water. In this method, adding a large amount of salt to the aqueous solution forces the organic compound out of the aqueous phase. However, the method can not be considered sustainable because it creates highly salty water. A greener alternative would be a method that allows reversible salting out. Herein, we describe aqueous solutions of switchable ionic strength. Aqueous solutions of a diamine in water have essentially zero ionic strength but are converted by CO(2) into solutions of high ionic strength. The change is reversible. Application to the reversible salting out of THF from water is described.

  4. Formation of hydroxyapatite in various aqueous solutions

    Science.gov (United States)

    Sturgeon, Jacqueline Lee

    Hydroxyapatite (HAp), Ca10(PO4)6(OH) 2, is important in the field of biomaterials as it is the mineral component of bones and teeth. Biological apatites do not maintain an exact composition and are usually calcium-deficient, represented as Ca(10- x)(HPO 4)x(PO4)(6-x)(OH)(2-x), where x ranges from 0 to 1, with various ion substitutions. Formation of calcium-deficient hydroxyapatites (CDHAp) from solid calcium phosphate precursor materials was performed at physiologic temperature (37°C) in a variety of aqueous solutions. Two cement systems were utilized in these experiments: tetralcium phosphate (TetCP) with dicalcium phosphate anhydrous (DCPA) and beta-tricalcium phosphate (beta-TCP). The kinetics, solution chemistry, phase evolution, and microstructure of the developed apatites were analyzed as appropriate. Reaction of beta-TCP in ammonium fluoride solutions formed HAp substituted with fluoride and calculated to be deficient in calcium. A new ratio of TetCP to DCPA was used with solutions of sodium bicarbonate to form a calcium-deficient carbonate hydroxyapatite. The capacity for sodium dihydrogen phosphate to buffer pH increases and enhance reaction kinetics in this system was also explored. Formation of a highly crystalline CDHAp was achieved by hydrolyzing beta-TCP in water for extended time periods. Lattice parameters were among the features characterized for this apatite. The hydrolysis of beta-TCP in phosphate buffered saline (PBS) and simulated body fluids (SBF) was also investigated; use of SBF was found to completely inhibit formation of HAp in this system while reaction in PBS was slow in comparison to water. The effects of filler materials on the mechanical properties of a calcium phosphate cement were examined using the TetCP/DCPA system. Dense aggregates were not found to decrease compressive strength in comparison to the cement alone. The use of aggregates was found to improve the compressive strength of cement formed using NaHCO3 solution as a

  5. 21 CFR 524.1200b - Kanamycin ophthalmic aqueous solution.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Kanamycin ophthalmic aqueous solution. 524.1200b Section 524.1200b Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 524.1200b Kanamycin ophthalmic aqueous solution. (a) Specifications. The drug, which is in an...

  6. Acetic acid extraction from aqueous solutions using fatty acids

    NARCIS (Netherlands)

    IJmker, H.M.; Gramblicka, M.; Kersten, S.R.A.; Ham, van der A.G.J.; Schuur, B.

    2014-01-01

    A major challenge for production of acetic acid via bio-based routes is cost-effective concentration and purification of the acetic acid from the aqueous solutions, for which liquid–liquid extraction is a possible method. A main challenge in extraction of acetic acid from dilute aqueous solutions is

  7. Structure of aqueous sodium perchlorate solutions.

    Science.gov (United States)

    General, Ignacio J; Asciutto, Eliana K; Madura, Jeffry D

    2008-12-01

    Salt solutions have been the object of study of many scientists through history, but one of the most important findings came along when the Hofmeister series were discovered. Their importance arises from the fact that they influence the relative solubility of proteins, and solubility is directly related to one of today's holy grails: protein folding. In this work we characterize one of the more-destabilizing salts in the series, sodium perchlorate, by studying it as an aqueous solution at various concentrations ranging from 0.08 to 1.60 mol/L. Molecular dynamics simulations at room temperature permitted a detailed study of the organization of solvent and cosolvent, in terms of its radial distribution functions, along with the study of the structure of hydrogen bonds in the ions' solvation shells. We found that the distribution functions have some variations in their shape as concentration changes, but the position of their peaks is mostly unaffected. Regarding water, the most salient fact is the noticeable (although small) change in the second hydration shell and even beyond, especially for g(O(w)***O(w)), showing that the locality of salt effects should not be restricted to considerations of only the first solvation shell. The perturbation of the second shell also appears in the study of the HB network, where the difference between the number of HBs around a water molecule and around the Na(+) cation gets much smaller as one goes from the first to the second solvation shell, yet the difference is not negligible. Nevertheless, the effect of the ions past their first hydration shell is not enough to make a noticeable change in the global HB network. The Kirkwood-Buff theory of liquids was applied to our system, in order to calculate the activity derivative of the cosolvent. This coefficient, along with a previously calculated preferential binding, allowed us to establish that if a folded AP peptide is immersed in the studied solution, becoming the solute, then

  8. Fluoride Adsorption by Pumice from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Amir Hossein Mahvi

    2012-01-01

    Full Text Available Drinking water provides many vital elements for the human body, but the presence of some dissolved elements more than permissible concentration can endanger human health. Among the dissolved elements in drinking water, fluoride is noticeable, because both the very low or very high concentrations have adverse health impacts such as dental caries. Therefore, fluoride concentration should be kept in acceptable levels. In this study Pumice was used for fluoride removal. It was found that Fluoride sorption kinetic was fitted by pseudo-second-order model. The maximum sorption capacity of Pumice was found to be 13.51 mg/g at laboratory temperature (24°C. Maximum sorption study occurred at pH= 3. Results of Isotherm showed the fluoride sorption has been well fitted with Freundlich isotherm model. This study has demonstrated that Pumice can be used as effective adsorbents for fluoride removal from aqueous solutions. The adsorbent prepared in this study was cheap and efficient in removal of fluoride than other adsorbents.

  9. Ozone photolysis of paracetamol in aqueous solution.

    Science.gov (United States)

    Neamţu, Mariana; Bobu, Maria; Kettrup, Antonius; Siminiceanu, Ilie

    2013-01-01

    The degradation of a paracetamol (N-acetil-para-aminofenol) aqueous solution (C (0) P = 5 mmol L(-1)) is studied in a bench-scale setup by means of simple ozonation (O3) and ozonation catalyzed with UV light (O3/UV) in order to quantify the influence of UV light on the degradation process. The results have shown that under the adopted experimental conditions (25°C, applied ozone dose = 9.8 mg L(-1) and gas flow rate of 20 L h(-1)) both oxidative systems are capable of removing the substrate with mineralization degrees up to 51% for ozonation and 53% for O3/UV. HPICE chromatography allowed the detection of nitrate ions and maleic and oxalic acids as ultimate carboxylic acids. The experimental data have been interpreted through 5 indicators: the conversion of paracetamol (XP ), the conversion degree of TOC (XTOC ), the apparent rate constant (kap ), the Hatta number (Ha) and the enhancement factor (E). The main advantage of photo-ozonation compared to simple ozonation was a more advanced conversion (79% vs. 92% after 90 min). The paracetamol decay follows a pseudo-first-order reaction with a superior rate constant (higher by 54%) for the UV catalyzed system in comparison with direct ozonation. Mineralization is slightly accelerated (+4%) in the O3/UV system, due to the additional production of hydroxyl radicals induced by the UV light and a higher Hatta number (+24%). Nevertheless, the process was still in the slow reaction kinetic regime (Ha < 0.3), and the enhancement factor was not significantly increased. The results are useful for the design and scale-up of the gas-liquid processes.

  10. Photolysis of Periodate and Periodic Acid in Aqueous Solution

    DEFF Research Database (Denmark)

    Sehested, Knud; Kläning, U. K.

    1978-01-01

    The photochemistry of periodate and periodic acid in aqueous solution was studied (i) by quantum yield measurements at low light intensity (ii) by flash photolysis, and (iii) by photolysis of glassy samples at 77 K. The photochemical studies were supplemented with pulse radiolysis studies...... of aqueous periodate solutions and with kinetic studies using stopped-flow technique. In strongly alkaline solution the photodecomposition of periodate proceeds via formation of O– and IVI. At pH

  11. Thermophysical Properties of Aqueous Solutions Used as Secondary Working Fluids

    OpenAIRE

    Melinder, Åke

    2007-01-01

    Secondary working fluids (secondary refrigerants, heat transfer fluids, antifreezes, brines) have long been used in various indirect re-frigeration and heat pump systems. Aqueous solutions (water solu-tions) have long been used as single phase (liquid only) secondary working fluids for cooling in supermarkets, ice rinks, heat recovery systems, heat pumps and other applications. However, aqueous solutions are increasingly used also for freezers in supermarkets and other applications in low tem...

  12. Critical properties of aqueous solutions. Part 1: Experimental data

    Science.gov (United States)

    Abdulagatov, A. I.; Stepanov, G. V.; Abdulagatov, I. M.

    2008-08-01

    All data available in the literature on the critical properties of binary aqueous solutions like H2O + common salt, H2O + hydrocarbon, H2O + alcohol, H2O + gas, and others are gathered. Methods for determining them are presented together with errors and concentration measurement intervals for each source of data. The format in which the data are presented will allow the readers to quickly find the necessary information on the critical properties of aqueous solutions from the original sources and use them for solving scientific and engineering tasks. Certain general features of the critical lines and phase diagrams of aqueous solutions with volatile and nonvolatile components are discussed.

  13. Instability of aqueous solutions of polyacrylamide in a hydrodynamic field

    Science.gov (United States)

    Makogon, B. P.; Bykova, E. N.; Bezrukova, M. A.; Klenin, S. I.; Ivanyuta, Yu. F.; Povkh, I. L.; Toryanik, A. I.

    1985-09-01

    This article discusses findings obtained regarding the effect of a hydrodynamic field on the reduced viscosity, effect of turbulent friction reduction, light scattering, double refraction, and optical density of aqueous solutions of hydrolyzed polyacrylamide.

  14. Surface tension and related thermodynamic quantities of aqueous electrolyte solutions

    CERN Document Server

    Matubayasi, Norihiro

    2013-01-01

    Surface tension provides a thermodynamic avenue for analyzing systems in equilibrium and formulating phenomenological explanations for the behavior of constituent molecules in the surface region. While there are extensive experimental observations and established ideas regarding desorption of ions from the surfaces of aqueous salt solutions, a more successful discussion of the theory has recently emerged, which allows the quantitative calculation of the distribution of ions in the surface region. Surface Tension and Related Thermodynamic Quantities of Aqueous Electrolyte Solutions provides a d

  15. Chemical characterization and anaerobic biodegradability of hydrothermal liquefaction aqueous products from mixed-culture wastewater algae.

    Science.gov (United States)

    Tommaso, Giovana; Chen, Wan-Ting; Li, Peng; Schideman, Lance; Zhang, Yuanhui

    2015-02-01

    This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5 h, and reaction temperatures from 260 °C to 320 °C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320 °C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320 °C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300 °C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.

  16. The effect of aqueous solution in Raman spectroscopy

    Science.gov (United States)

    Kang, Jian; Yuan, Xiaojuan; Dong, Xiao; Gu, Huaimin

    2009-08-01

    In Raman detection, the most popular solution for the samples is tri-distilled water. But the effect of aqueous solution is barely studied in Raman spectroscopy. In fact Raman spectroscopy of solid-state and liquid-state are obvious different. In addition, FWHM of Raman spectral peaks also change evidently. In this paper, several samples were selected for the experiment; including sodium nitrate, sodium nitrite, glucose and caffeine. By comparing the Raman spectroscopy of samples at different concentrations, it is found that the concentration of the sample can affect the strength of Raman spectroscopy, but it can hardly impact FWHM of Raman spectral peaks. By comparing the Raman spectroscopy of liquid-state with the Raman spectroscopy of solid-state, it is observed that the FWHM of some Raman spectral peaks varied obviously; that may be because when the sample was dissolved into the water, the crystal lattice structure was broken, and for some samples atom form became ion form in aqueous solution. Those structural variations caused the variation of the FWHM. The Raman spectroscopy of caffeine aqueous solution at very low concentration was also detected and analyzed. Compared with the Raman spectra of solid-state samples, it is found that some Raman spectral peaks disappeared when the sample was dissolved in water. It is possible that the low concentration of the sample result in the weakening of Raman signals and the disappearing of some weak Raman spectral peaks. Then Ag nanoparticles were added into the caffeine aqueous solution, the results suggest that surface enhanced Raman spectroscopy (SERS) not only can enhance the Raman spectral signal, but also can reduce the effect of aqueous solution. It is concluded that the concentration of sample only affects the strength of Raman spectroscopy; the aqueous solution can affect the FWHM of Raman spectral peaks; and SERS can reduce the effect of aqueous solution.

  17. Aqueous solutions at the interface with phospholipid bilayers.

    Science.gov (United States)

    Berkowitz, Max L; Vácha, Robert

    2012-01-17

    In a sense, life is defined by membranes, because they delineate the barrier between the living cell and its surroundings. Membranes are also essential for regulating the machinery of life throughout many interfaces within the cell's interior. A large number of experimental, computational, and theoretical studies have demonstrated how the properties of water and ionic aqueous solutions change due to the vicinity of membranes and, in turn, how the properties of membranes depend on the presence of aqueous solutions. Consequently, understanding the character of aqueous solutions at their interface with biological membranes is critical to research progress on many fronts. The importance of incorporating a molecular-level description of water into the study of biomembrane surfaces was demonstrated by an examination of the interaction between phospholipid bilayers that can serve as model biological membranes. The results showed that, in addition to well-known forces, such as van der Waals and screened Coulomb, one has to consider a repulsion force due to the removal of water between surfaces. It was also known that physicochemical properties of biological membranes are strongly influenced by the specific character of the ions in the surrounding aqueous solutions because of the observation that different anions produce different effects on muscle twitch tension. In this Account, we describe the interaction of pure water, and also of aqueous ionic solutions, with model membranes. We show that a symbiosis of experimental and computational work over the past few years has resulted in substantial progress in the field. We now better understand the origin of the hydration force, the structural properties of water at the interface with phospholipid bilayers, and the influence of phospholipid headgroups on the dynamics of water. We also improved our knowledge of the ion-specific effect, which is observed at the interface of the phospholipid bilayer and aqueous solution, and its

  18. Acidities of Water and Methanol in Aqueous Solution and DMSO

    Science.gov (United States)

    Gao, Daqing

    2009-01-01

    The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent…

  19. Synthesis and Aqueous Solution Viscosity of Hydrophobically Modified Xanthan Gum

    Institute of Scientific and Technical Information of China (English)

    QIAN Xiao-lin; WU Wen-hui; YU Pei-zhi; WANG Jian-quan

    2007-01-01

    Two xanthan gum derivatives hydrophobically modified by 4 or 8 tetradecyl chains per 100 xanthan gum structure units were synthesized. The derivatives were studied by scanning electron microscope and pyrene fluorescence spectrometry. And the aqueous solution apparent viscosity of the derivatives was investigated. The results indicate that the network of the derivatives with more hydrophobic groups is closer and tighter. With increasing of alkyl chain substitution degree, the hydrophobically associating interactions enhance in aqueous solution. Aqueous solution apparent viscosity of the derivatives increases with increasing of polymer concentration and alkyl substitution degree, and decreases with the increase of temperature. In the brine solution, the strong viscosity enhancement phenomenon appears. The interaction between the derivatives and surfactant sodium dodecylbenzene sulfonate is strong.

  20. Structure of water and the thermodynamics of aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nemethy, G.

    1970-10-26

    This report represents the summary of a series of lectures held at the Istituto Superiore di Sanita, Laboratori di Fisica, from 18 September to 26 October 1970. The topics discussed were: Intermolecular forces, the individual water molecule and the hydrogen bond, the structures of the solid phases of water, experimental information on the strucuture of liquid water, theoretical models of water structure, experimental properties and theoretical models of aqueous solutions of nonpolar solutes, polar solutes, and electrolytes, the conformational stability of biological macromolecules.

  1. Conductivity of Oxalic Acid in Aqueous Solution at Low Concentration

    Institute of Scientific and Technical Information of China (English)

    倪良; 韩世钧

    2005-01-01

    Oxalic acid is a weak and unsymmetrical bi-basic acid. There exist dissociation and association equilibria among the species in aqueous solution. The molar conductivity of the solution is the sum of the ionic contributions.Based on this idea, a new prediction equation of ionic conductivity was proposed at low concentration. The molar conductivities of the solution and its relevant ions were calculated respectively. The results obtained were in good agreement with those from experiments and the Quint-Viallard equation.

  2. Electrochemical oxidation of pyrrhotute in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    QIN Wen-qing; LI Quan; QIU Guan-zhou; XU Ben-jun

    2005-01-01

    The anodic surface oxidation of natural pyrrhotite in 0.3 mol/L KCl and HCl solution (pH 4. 0) and 0.1 mol/L Na2 B4O7 solution (pH 9.18) respectively was investigated by using cyclic voltammetry, Tafel plot, and chronoamperometry. In 0.3 mol/L KCl and HCl solution (pH 4.0), at potential less than 0.5 V(vs SHE), the production of anodic oxidation on pyrrhotite surface can not maintain a stable phase to form a passive film. In 0. 1 mol/L Na2B4 O7 solution (pH 9.18), when the electrode potential increases to more than 0.5 V (vs SHE), part of S is oxidized to sulfate, making the passive film somewhat porous, but elemental S and metal oxidates Fe(OH)3 still remain on the electrode surface, and the passive film can not be broken down totally. According to PARCalc Tafel analysis,the corresponding corrosion current density (J0) is 5.34 μA/cm2 , which is also the exchange current density of the oxidation reaction on pyrrhotite electrode surface in 0. 1 mol/L Na2B4O7 solution (pH 9.18). The electrochemical dynamics equation of the oxidation was determined.

  3. Molecular Weight and Aggregation of Erwinia Gum in Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weight-average molecular weights Mw, number-average molecular weights Mn and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.

  4. Oxidation of Hydrazine in Aqueous Solutions

    Science.gov (United States)

    1978-03-01

    mechanism is different in the two different temperature regions [ Levenspiel (Reference 21)]. Lurker (Reference 7) also observed that at 6°C a kinetic...and Bielski, B., Kinetic Systems: Mathematical Descriptions of Chemical Kinetics in Solution, Wiley Interscience, New York (1972). 21. Levenspiel , 0

  5. Predicting accurate absolute binding energies in aqueous solution

    DEFF Research Database (Denmark)

    Jensen, Jan Halborg

    2015-01-01

    Recent predictions of absolute binding free energies of host-guest complexes in aqueous solution using electronic structure theory have been encouraging for some systems, while other systems remain problematic. In this paper I summarize some of the many factors that could easily contribute 1-3 kcal......-represented by continuum models. While I focus on binding free energies in aqueous solution the approach also applies (with minor adjustments) to any free energy difference such as conformational or reaction free energy differences or activation free energies in any solvent....

  6. A lithium ion battery using an aqueous electrolyte solution

    OpenAIRE

    Zheng Chang; Chunyang Li; Yanfang Wang; Bingwei Chen; Lijun Fu; Yusong Zhu; Lixin Zhang; Yuping Wu; Wei Huang

    2016-01-01

    Energy and environmental pollution have become the two major problems in today’s society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge vo...

  7. Ionisation constants of inorganic acids and bases in aqueous solution

    CERN Document Server

    Perrin, D D

    2013-01-01

    Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution, Second Edition provides a compilation of tables that summarize relevant data recorded in the literature up to the end of 1980 for the ionization constants of inorganic acids and bases in aqueous solution. This book includes references to acidity functions for strong acids and bases, as well as details about the formation of polynuclear species. This text then explains the details of each column of the tables, wherein column 1 gives the name of the substance and the negative logarithm of the ionization constant and column 2

  8. Removal of Phosphate from Aqueous Solution with Modified Bentonite

    Institute of Scientific and Technical Information of China (English)

    唐艳葵; 童张法; 魏光涛; 李仲民; 梁达文

    2006-01-01

    Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% of phosphate removal rate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.

  9. [Extraction of alpha-cypermethrin from aqueous methanol solutions].

    Science.gov (United States)

    Shormanov, V K; Chigareva, E N; Belousova, O V

    2010-01-01

    Alpha cypermethrin was extracted from aqueous methanol solutions using hydrophobic organic solvents. The efficiency of extraction was shown to depend on the chemical nature of the solvent, the water to methanol ratio, and saturation of the aqueous methanol layer with an electrolyte. Optimal extraction of alpha-cypermethrin was achieved using toluene as the solvent under desalinization conditions. The extraction factor for the removal of the sought amount of alpha-cypermethrin from the water-methanol solution (4:1) using various solvents was calculated.

  10. Glasslike behavior in aqueous electrolyte solutions.

    Science.gov (United States)

    Turton, David A; Hunger, Johannes; Hefter, Glenn; Buchner, Richard; Wynne, Klaas

    2008-04-28

    When salts are added to water, generally the viscosity increases, suggesting that the ions increase the strength of the water's hydrogen-bond network. However, infrared pump-probe measurements on electrolyte solutions have found that ions have no influence on the rotational dynamics of water molecules, implying no enhancement or breakdown of the hydrogen-bond network. Here, we report optical Kerr effect and dielectric relaxation spectroscopic measurements, which have enabled us to separate the effects of rotational and transitional motions of the water molecules. These data show that electrolyte solutions behave like a supercooled liquid approaching a glass transition in which rotational and translational molecular motions are decoupled. It is now possible to understand previously conflicting viscosity data, nuclear magnetic resonance relaxation, and ultrafast infrared spectroscopy in a single unified picture.

  11. Glasslike Behavior in Aqueous Electrolyte Solutions

    CERN Document Server

    Turton, David A; Hefter, Glenn; Buchner, Richard; Wynne, Klaas; 10.1063/1.2906132

    2009-01-01

    When salts are added to water, the viscosity generally increases suggesting the ions increase the strength of the water's hydrogen-bond network. However, infrared pump-probe measurements on electrolyte solutions have found that ions have no influence on the rotational dynamics of water molecules implying no enhance-ment or breakdown of the hydrogen-bond network. Here we report optical Kerr-effect and dielectric relaxa-tion spectroscopic measurements, which have enabled us to separate the effects of rotational and transitional motions of the water molecules. These data show that electrolyte solutions behave like a supercooled liquid approaching a glass transition in which rotational and translational molecular motions are decoupled. It is now possible to understand previously conflicting viscosity data, nuclear magnetic resonance relaxation, and ultrafast infrared spectroscopy in a single unified picture.

  12. LIGHT SCATTERING OF POLYSACCHARIDE FROM LACQUER IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lina; DU Yumin; KUMANOTANI JU

    1989-01-01

    The polysaccharide having weight-average molecular weight Mw= 1. 09 × 105 , isolated from the sap of lac trees ( Vietnam ), was separated into 12 fractions by aqueous-phase preparative gel permeation chromatography. The molecular weights and molecular weight distributions of the fractions were measured in aqueous 0.08M KCl/0.01 M NaAc and 0.4M KCl/0.05M NaAc at pH = 7.6 by light scattering, viscometry and gel permeation chromatography. The Mark-Houwink equation in aqueous 0.08M KCl/0.01M NaAc at30 ℃ was found to be [ η] = 2.28 ×10-2 M0.52w ( cm3/g ), which indicated the polysaccharide chain in the aqueous solution to be a spherical random coil.

  13. Photocatalytic degradation of molinate in aqueous solutions.

    Science.gov (United States)

    Bizani, E; Lambropoulou, D; Fytianos, K; Poulios, I

    2014-11-01

    In this study, the degradation of molinate through heterogeneous photocatalysis, using two different types of the semiconductor TiO2 as photocatalyst, as well as through homogeneous treatment, applying the photo-Fenton reaction, has been investigated. As far as heterogeneous photocatalysis is concerned, the degradation of the pesticide follows apparent first-order kinetics, while the type of the catalyst and the pH value of the solution affect the degradation rate. The effect of the addition of electron scavengers (H2O2 and K2S2O8) was also studied. In the case of photo-Fenton-assisted system, the degradation also follows pseudo-first-order kinetics. Parameters such as iron's and electron scavenger's concentration and inorganic ions strongly affect the degradation rate. The extent of pesticide mineralization was investigated using dissolved organic carbon (DOC) measurements. The toxicity of the treated solution was evaluated using the Microtox test based on the luminescent bacteria Vibrio fischeri. The detoxification and mineralization efficiency was found to be dependent on the system studied, and although it did not follow the rate of pesticide disappearance, it took place in considerable extent. The study of the photodegradation treatment was completed by the determination of the intermediate by-products formed during the process, which was carried out using LC-MS/MS technique and led to similar compounds with both processes.

  14. Permeability in a state of partial solidification of aqueous solution

    Science.gov (United States)

    Okada, Masashi; Kang, Chaedong; Okiyama, Haruhiko

    A mushy region was formed by solidifying NaCl aqueous solution in a circular tube or a rectangular tube. The measurements of permeability were performed by changing volume fraction of liquid region in the mushy region. The dendritic ice in the solidification process was observed with a CCD microscope. The following results were obtained. The permeability increases with the volume fraction of liquid phase, and decreases with increasing the super-cooling degree of the solution or increasing the initial concentration of the solution, and is constant after the mushy region was formed. The arm space of dendrite becomes narrower as the super-cooling degree of the solution increases.

  15. Radiolysis of paracetamol in dilute aqueous solution

    Science.gov (United States)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Takács, Erzsébet; Wojnárovits, László

    2012-09-01

    Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O2 is c.a. 10%. The efficiency is 2-3 times higher in the presence of O2 due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily.

  16. Reactive Extraction of Alcohols from Apolar Hydrocarbons with Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The aqueous solutions are evaluated as sustainable reactive extraction solvents for the recovery of monohydroxyl alcohols (benzyl alcohol, 1-hexanol, cyclohexanol) present in few-percent concentrations in apolar hydrocarbons (toluene, n-hexane, and cyclohexane) by considering two approaches. An aqueous solution containing a reactive extractant, like borate salts, borate complexes, a monosalt of dicarboxylic acid,hydroxypropyl-cyclodextrins, and silver nitrate, shows limited potential to be used. Another approach, in which the alcohol is chemically modified prior to the extraction into an easy-extractable form, in this case a monoesterlcarboxylic acid, shows much more potential. An environmentally benign aqueous solution of sodium hydrogen carbonate can provide a distribution ratio of benzyl alcohol up to 200, leaving the solubility of the organic solvent in the aqueous solution unchanged relative to pure water and therefore increasing the selectivity with two orders of magnitude. The modification of aromatic, cyclo-aliphatic, and linear aliphatic alcohols can be performed efficiently in the apolar organic solvent without need for a catalyst. The recovery of the modified alcohol can be performed by back-extraction in combination with a spontaneous hydrolysis.

  17. Reactive Extraction of Alcohols from Apolar Hydrocarbons with Aqueous Solutions

    NARCIS (Netherlands)

    Kuzmanovic, Boris; Kuipers, Norbert J.M.; Haan, de André B.; Kwant, Gerard

    2006-01-01

    The aqueous solutions are evaluated as sustainable reactive extraction solvents for the recovery of monohydroxyl alcohols (benzyl alcohol, 1-hexanol, cyclohexanol) present in few-percent concentrations in apolar hydrocarbons (toluene, n-hexane, and cyclohexane) by considering two approaches. An aque

  18. Solubility of carbon dioxide in aqueous piperazine solutions

    NARCIS (Netherlands)

    Derks, P. W. J.; Dijkstra, H. B. S.; Hogendoorn, J. A.; Versteeg, G. F.

    2005-01-01

    In the present work, new experimental data are presented on the solubility of carbon dioxide in aqueous piperazine solutions, for concentrations of 0.2 and 0.6 molar piperazine and temperatures of 25, 40, and 70°C respectively. The present data, and other data available in the literature, were corr

  19. Rheological properties of silica suspensions in aqueous cellulose derivatives solutions

    Science.gov (United States)

    Ryo, Y.; Kawaguchi, M.

    1992-05-01

    The rheological properties of the silica suspensions in aqueous solutions of hydroxypropylmethylcellulose (HPMC) were investigated in terms of the shear stress and storage and loss moduli (G' and G`) as a function of silica content, HPMC concentration, and HPMC molecular weight by using a coaxial cylinder rheometer.

  20. Oscillometric and conductometric analysis of aqueous and organic dosimeter solutions

    DEFF Research Database (Denmark)

    Kovacs, A.; Slezsak, I.; McLaughlin, W.L.;

    1995-01-01

    ''conductometric'' electrodes and the study of the effect of frequency on the sensitivity of the method. On the basis of these investigations an oscillometric reader has been designed and tested. The same evaluation methods have been tested on the irradiated aqueous alanine solutions, aiming also at the study...

  1. Adsorptive removal of antibiotics from aqueous solution using carbon materials.

    Science.gov (United States)

    Yu, Fei; Li, Yong; Han, Sheng; Ma, Jie

    2016-06-01

    Antibiotics, an important type of environmental contamination, have attracted many researchers to the study of their removal from aqueous solutions. Adsorption technology is a fast, efficient, and economical physicochemical method that is extensively used in wastewater treatment. From original activated carbon and carbon nanotubes to the latest graphene-based materials, carbon-based materials have been widely used as highly effective adsorbents for contaminant removal from aqueous solution because of their large specific surface area, high porosity, and high reaction activity. In this article, adsorption removal methods for four major types of antibiotic (tetracyclines, sulfonamides, macrolides, and quinolones) are reviewed. We also provide an overview of the application development of carbon materials as adsorbents for antibiotic removal from aqueous solution. The most promising works are discussed, and the main challenges in preparing high-performance adsorbents and the development tendency of adsorbents are also analyzed. This work provides theoretical guidance for subsequent research in the design and modification of carbon materials for applications in the adsorption removal of antibiotics from aqueous solution.

  2. CATALYSIS BY SURFACTANT AGGREGATES IN AQUEOUS-SOLUTIONS

    NARCIS (Netherlands)

    ENGBERTS, JBFN

    1992-01-01

    Catalysis of organic reactions by unfunctionalized surfactant aggregates (micelles, vesicles) in aqueous solution is largely determined by medium effects induced at the micellar binding sites and by entropy effects due to compartimentalization. The efficiency of these catalytic effects responds to c

  3. Kinetics of absorption of carbon dioxide in aqueous piperazine solutions

    NARCIS (Netherlands)

    Derks, P. W. J.; Kleingeld, T.; van Aken, C.; Hogendoorn, J. A.; Versteeg, G. F.

    2006-01-01

    In the present work the absorption of carbon dioxide into aqueous piperazine (PZ) solutions has been studied in a stirred cell, at low to moderate temperatures, piperazine concentrations ranging from 0.6 to 1.5 kmol m- 3, and carbon dioxide pressures up to 500 mbar, respectively. The obtained experi

  4. DETERMINATION OF CHLORHEXIDINE IN SALIVA AND IN AQUEOUS-SOLUTIONS

    NARCIS (Netherlands)

    de Vries, J.; Ruben, J; Arends, J.

    1991-01-01

    A new method is presented for the determination of chlorhexidine in centrifuged saliva and in aqueous solutions by means of fluorescence spectroscopy. The method relies on complex formation between chlorhexidine and eosin. The fluorescence value of the chlorhexidine-eosin system decreases with incre

  5. Colorimetric and fluorescent detection of biological thiols in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Yin-Hui Li; Jin-Feng Yang; Chang-Hui Liu; Ji-Shan Li; Rong-Hua Yang

    2013-01-01

    A new colorimetric and fluorescent probe,2-(2,4-dinitrostyryl)-1,3,3-trimethyl-3H-indolium iodide (DTI),for selective and sensitive detection of biological thiols is reported.In aqueous solution at physiological pH 7.4,biological thiols react with DTI via Michael addition to give the brownish red adduct concomitant with fluorescence emission decrease.

  6. Adsorption of lead ions from aqueous solutions using clinoptilolite

    OpenAIRE

    Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Golomeov, Blagoj; Blažev, Krsto; Krstev, Aleksandar

    2014-01-01

    The adsorption of lead ions from synthetic aqueous solutions was performed by using natural zeolite (clinoptilolite). In order to determine the effectivity of clinoptilolite a series of experiments were performed under batch conditions from single ion solutions. Experiments were carried out at different initial concentration of lead ions, different initial pH values and different adsorbent mass. The adsorption kinetics is reasonably fast. It means that in the first 20 min approximately 90...

  7. Removal of azo dye from aqueous solutions using chitosan

    Directory of Open Access Journals (Sweden)

    Zuhair Jabbar

    2014-06-01

    Full Text Available Adsorption of Congo Red (CR from aqueous solution onto chitosan was investigated in a batch system. The effects of solution pH, initial dye concentration, and temperature were studied. Results indicated that chitosan could be used as a biosorbent to remove the azo dyes from contaminated water. Synthesize of chitosan involved three main stages as preconditioning, demineralization, deproteinization and deacetylation. Chitosan was characterized using Fourier Transform Infrared Spectroscopy (FTIR and solubility in 1% acetic acid.

  8. Phytoremediation of Heavy Metals in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Felix Aibuedefe AISIEN

    2010-12-01

    Full Text Available One of the major environmental problems is the pollution of water and soil by toxic heavy metals. This study investigated the phytoremediation potential of water hyacinth, for the removal of cadmium (Cd, lead (Pb and zinc (Zn. Water hyacinths were cultured in bore-hole water, supplemented with 5mg/l of Zn and Pb and 1mg/l of Cd at pH 4.5, 6.8 and 8.5. The plants were separately harvested each week for six weeks. The results showed that removal of these metals from solution was fast especially in the first two weeks, after which it became gradual till saturation point was reached. The accumulation of Cd and Zn in leaves and roots increased with increase in pH. The highest accumulation was in the roots with metal concentration of 4870mg/kg, 4150mg/kg and 710mg/kg for Zn, Pb and Cd respectively at pH 8.5. The maximum values of bioconcentration factor (BCF for Zn, Pb and Cd were 1674, 1531 and 1479 respectively, suggesting that water hyacinth was good accumulator of Zn, Pb and Cd, and could be used to treat industrial wastewater contaminated with heavy metals such as Zn, Pb and Cd.

  9. Block copolymer membranes for aqueous solution applications

    KAUST Repository

    Nunes, Suzana Pereira

    2016-03-22

    Block copolymers are known for their intricate morphology. We review the state of the art of block copolymer membranes and discuss perspectives in this field. The main focus is on pore morphology tuning with a short introduction on non-porous membranes. The two main strategies for pore formation in block copolymer membranes are (i) film casting and selective block sacrifice and (ii) self-assembly and non-solvent induced phase separation (SNIPS). Different fundamental aspects involved in the manufacture of block copolymer membranes are considered, including factors affecting the equilibrium morphology in solid films, self-assembly of copolymer in solutions and macrophase separation by solvent-non-solvent exchange. Different mechanisms are proposed for different depths of the SNIPS membrane. Block copolymer membranes can be prepared with much narrower pore size distribution than homopolymer membranes. Open questions and indications of what we consider the next development steps are finally discussed. They include the synthesis and application of new copolymers and specific functionalization, adding characteristics to respond to stimuli and chemical environment, polymerization-induced phase separation, and the manufacture of organic-inorganic hybrids.

  10. Assembly of DNA Architectures in a Non-Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Thomas J. Proctor

    2012-08-01

    Full Text Available In the present work, the procedures for the creation of self-assembled DNA nanostructures in aqueous and non-aqueous media are described. DNA-Surfactant complex formation renders the DNA soluble in organic solvents offering an exciting way to bridge the transition of DNA origami materials electronics applications. The DNA retains its structural features, and these unique geometries provide an interesting candidate for future electronics and nanofabrication applications with potential for new properties. The DNA architectures were first assembled under aqueous conditions, and then characterized in solution (using circular dichroism (CD spectroscopy and on the surface (using atomic force microscopy (AFM. Following aqueous assembly, the DNA nanostructures were transitioned to a non-aqueous environment, where butanol was chosen for optical compatibility and thermal properties. The retention of DNA hierarchical structure and thermal stability in non-aqueous conditions were confirmed via CD spectroscopy. The formation and characterization of these higher order DNA-surfactant complexes is described in this paper.

  11. Critical droplet theory explains the glass formability of aqueous solutions.

    Science.gov (United States)

    Warkentin, Matthew; Sethna, James P; Thorne, Robert E

    2013-01-04

    When pure water is cooled at ~10(6) K / s, it forms an amorphous solid (glass) instead of the more familiar crystalline phase. The presence of solutes can reduce this required (or "critical") cooling rate by orders of magnitude. Here, we present critical cooling rates for a variety of solutes as a function of concentration and a theoretical framework for understanding these rates. For all solutes tested, the critical cooling rate is an exponential function of concentration. The exponential's characteristic concentration for each solute correlates with the solute's Stokes radius. A modification of critical droplet theory relates the characteristic concentration to the solute radius and the critical nucleation radius of ice in pure water. This simple theory of ice nucleation and glass formability in aqueous solutions has consequences for general glass-forming systems, and in cryobiology, cloud physics, and climate modeling.

  12. Raman spectra of amino acids and their aqueous solutions

    Science.gov (United States)

    Zhu, Guangyong; Zhu, Xian; Fan, Qi; Wan, Xueliang

    2011-03-01

    Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids ( L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

  13. Solid-like mechanical behaviors of ovalbumin aqueous solutions.

    Science.gov (United States)

    Ikeda, S; Nishinari, K

    2001-04-12

    Flow and dynamic mechanical properties of ovalbumin (OVA) aqueous solutions were investigated. OVA solutions exhibited relatively large zero-shear viscosity values under steady shear flow and solid-like mechanical responses against oscillating small shear strains, that is, the storage modulus was always larger than the loss modulus in the examined frequency range (0.1--100 rad s(-1)). These results suggest that dispersed OVA molecules arranged into a colloidal crystal like array stabilized by large interparticle repulsive forces. However, marked solid-like mechanical behaviors were detected even when electrostatic repulsive forces among protein molecules were virtually absent, which could not be explained solely on the basis of conventional Derjaguin--Landau--Verwey--Overbeek (DLVO) theory. Large non-DLVO repulsive forces seem to stabilize native OVA aqueous solutions.

  14. Adsorption of EDTA on activated carbon from aqueous solutions.

    Science.gov (United States)

    Zhu, Hai-song; Yang, Xiao-juan; Mao, Yan-peng; Chen, Yu; Long, Xiang-li; Yuan, Wei-kang

    2011-01-30

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R(2) = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (E(a), ΔG(0), ΔH(0), ΔS(0)) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  15. Molecular mechanism of the viscosity of aqueous glucose solutions

    Science.gov (United States)

    Bulavin, L. A.; Zabashta, Yu. F.; Khlopov, A. M.; Khorol'skii, A. V.

    2017-01-01

    Experimental relations are obtained for the viscosity of aqueous glucose solutions in the temperature range of 10-80°C and concentration range 0.01-2.5%. It is found that the concentration dependence of fluidity is linear when the concentration is higher than a certain value and varies at different temperatures. The existence of such a dependence indicates that the mobilities of solvent and solute molecules are independent of the concentration of solutions. This assumption is used to construct a theoretical model, in which the structure of an aqueous glucose solution is presented as a combination of two weakly interacting networks formed by hydrogen bonds between water molecules and between glucose molecules. Theoretical relations are obtained using this model of network solution structure for the concentration and temperature dependence of solution viscosity. Experimental data are used to calculate the activation energies for water ( U w = 3.0 × 10-20 J) and glucose molecules ( U g = 2.8 × 10-20 J). It is shown that the viscosity of a solution in such a network structure is governed by the Brownian motion of solitons along the chains of hydrogen bonds. The weak interaction between networks results in the contributions to solution fluidity made by the motion of solitons in both of them being almost independent.

  16. Spontaneous Oligomerization of Nucleotide Alternatives in Aqueous Solutions

    Science.gov (United States)

    Smith, Karen E.; House, Christopher H.; Dworkin, Jason P.; Callahan, Michael P.

    2017-03-01

    On early Earth, a primitive polymer that could spontaneously form from likely available precursors may have preceded both RNA and DNA as the first genetic material. Here, we report that heated aqueous solutions containing 5-hydroxymethyluracil (HMU) result in oligomers of uracil, heated solutions containing 5-hydroxymethylcytosine (HMC) result in oligomers of cytosine, and heated solutions containing both HMU and HMC result in mixed oligomers of uracil and cytosine. Oligomerization of hydroxymethylated pyrimidines, which may have been abundant on the primitive Earth, might have been important in the development of simple informational polymers.

  17. Dephosphorization of Steelmaking Slag by Leaching with Acidic Aqueous Solution

    Science.gov (United States)

    Qiao, Yong; Diao, Jiang; Liu, Xuan; Li, Xiaosa; Zhang, Tao; Xie, Bing

    2016-09-01

    In the present paper, dephosphorization of steelmaking slag by leaching with acidic aqueous solution composed of citric acid, sodium hydroxide, hydrochloric acid and ion-exchanged water was investigated. The buffer solution of C6H8O7-NaOH-HCl system prevented changes in the pH values. Kinetic parameters including leaching temperature, slag particle size and pH values of the solution were optimized. The results showed that temperature has no obvious effect on the dissolution ratio of phosphorus. However, it has a significant effect on the dissolution ratio of iron. The dephosphorization rate increases with the decrease of slag particle size and the pH value of the solution. Over 90% of the phosphorus can be dissolved in the solution while the corresponding leaching ratio of iron was only 30% below the optimal condition. Leaching kinetics of dephosphorization follow the unreacted shrinking core model with a rate controlled step by the solid diffusion layer, the corresponding apparent activation energy being 1.233 kJ mol-1. A semiempirical kinetic equation was established. After leaching, most of the nC2S-C3P solid solution in the steelmaking slag was selectively dissolved in the aqueous solution and the iron content in the solid residue was correspondingly enriched.

  18. Rheological properties of novel thermo-responsive polycarbonates aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    王月霞; 谭业邦; 黄晓玲

    2008-01-01

    Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol)(PEG) and poly(propylene glycol)(PPG) blocks,using triphosgene as coupling agent and pyridine as catalyst.The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements.Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions.The shear viscosity decreases with increasing poly(ethylene oxide)(PEO) composition.The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration.When the flow curves are fitted to the power law model,flow index is obtained to be less than 1,as exhibiting typical pesudoplastic fluid.The viscoelastic properties of the system also show close dependence on the composition of polycarbonates.Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties.For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1,the sol-gel transition occurs at 37 ℃,which makes the system suitable as an injectable drug delivery system.

  19. Adsorption Kinetics of Methylene Blue from Aqueous Solutions onto Palygorskite

    Institute of Scientific and Technical Information of China (English)

    PENG Shuchuan; WANG Shisheng; CHEN Tianhu; JIANG Shaotong; HUANG Chuanhui

    2006-01-01

    The adsorption kinetics of methylene blue from aqueous solutions on purified palygorskite was investigated. The kinetics data related to the adsorption of methylene blue from aqueous solutions are in good agreement with the pseudo-second order equation in ranges of initial concentration of 120-210 mg/L, oscillation speed of 100-200 r/min and temperature of 298-328K. The experimental results show that methylene blue is only adsorbed onto the external surface of purified palygorskite,and the apparent adsorption activation energy is 13.92 k J/mol. The relatively low apparent adsorption activation energy suggests that the adsorption of methylene blue involves in not only a chemical, but also a physical adsorption process, and it is controlled by the combination of chemical adsorption and liquid-film diffusion.

  20. Photodegradation of Norfloxacin in aqueous solution containing algae

    Institute of Scientific and Technical Information of China (English)

    Junwei Zhang; Dafang Fu; Jilong Wu

    2012-01-01

    Photodegradation of Norfloxacin in aqueous solution containing algae under a medium pressure mercury lamp (15 W,λmax =365 nm) was investigated.Results indicated that the photodegradation of Norfloxacin could be induced by the algae in the heterogeneous algaewater systems.The photodegradation rate of Norfloxacin increased with increasing algae concentration,and was greatly influenced by the temperature and pH of solution.Meanwhile,the cooperation action of algae and Fe(Ⅲ),and the ultrasound were beneficial to photodegradation of Norfloxaciu.The degradation kinetics of Norfloxacin was found to follow the pseudo zero-order reaction in the suspension of algae.In addition,we discussed the photodegradation mechanism of Norfloxacin in the suspension of algae.This work will be helpful for understanding the photochemical degradation of antibiotics in aqueous environment in the presence of algae,for providing a new method to deal with antibiotics pollution.

  1. Predicting accurate absolute binding energies in aqueous solution

    DEFF Research Database (Denmark)

    Jensen, Jan Halborg

    2015-01-01

    Recent predictions of absolute binding free energies of host-guest complexes in aqueous solution using electronic structure theory have been encouraging for some systems, while other systems remain problematic. In this paper I summarize some of the many factors that could easily contribute 1-3 kcal...... mol(-1) errors at 298 K: three-body dispersion effects, molecular symmetry, anharmonicity, spurious imaginary frequencies, insufficient conformational sampling, wrong or changing ionization states, errors in the solvation free energy of ions, and explicit solvent (and ion) effects that are not well......-represented by continuum models. While I focus on binding free energies in aqueous solution the approach also applies (with minor adjustments) to any free energy difference such as conformational or reaction free energy differences or activation free energies in any solvent....

  2. Adsorption of cadmium from aqueous solutions by perlite.

    Science.gov (United States)

    Mathialagan, T; Viraraghavan, T

    2002-10-14

    The present study examined the use of perlite for the removal of cadmium from aqueous solutions. The effects of pH and contact time on the adsorption process were examined. The optimum pH for adsorption was found to be 6.0. Residual cadmium concentration reached equilibrium in 6h and the rate of cadmium adsorption by perlite was rapid in the first hour of the reaction time. Ho's pseudo-second-order model best described the kinetics of the reaction. Batch adsorption experiments conducted at room temperature (22+/-1 degrees C) showed that the adsorption pattern followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies was 55%. Thomas model was used to describe the adsorption data from column studies. The results generally showed that perlite could be considered as a potential adsorbent for cadmium removal from aqueous solutions.

  3. Removal of methyl violet from aqueous solution by perlite.

    Science.gov (United States)

    Doğan, Mehmet; Alkan, Mahir

    2003-11-01

    The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective.

  4. SWELLING EQUILIBRIUM OF NONIONIC POLYACRYLAMIDE HYDROGEL IN AQUEOUS SALT SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of nonionic polyacrylamide hydrogels, using acrylamide as monomer and N,N’-methylene diacrylamide as crosslinking agent, were prepared by the free radical polymerization in aqueous solution. Swelling equilibria for the gels were carried out in aqueous solutions of NaCl, KCl, CaCl2, Na2HPO4 and K2HPO4 with concentration ranging from 10-3 to 5mol/kgH2O at 25℃. Experimental results revealed that the chlorides and phosphates cause a different behavior at higher salt concentration. The swelling ratio increases with increasing concentration of chlorides salts, while decreases with the increased phosphates salt concentration. The phenomena seem to be related to the different interactions of chloride and hydrogen phosphate ions with the network groups. Furthermore, the effects of different concentration of crosslinking agent and total monomers on gel swelling performance were also investigated.

  5. A lithium ion battery using an aqueous electrolyte solution

    Science.gov (United States)

    Chang, Zheng; Li, Chunyang; Wang, Yanfang; Chen, Bingwei; Fu, Lijun; Zhu, Yusong; Zhang, Lixin; Wu, Yuping; Huang, Wei

    2016-06-01

    Energy and environmental pollution have become the two major problems in today’s society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge voltage is up to 3.1 V and energy density based on the two electrode materials is 258 Wh kg‑1. It will be a promising energy storage system with good safety and efficient cooling effects.

  6. Diketopiperazine-mediated peptide formation in aqueous solution

    Science.gov (United States)

    Nagayama, M.; Takaoka, O.; Inomata, K.; Yamagata, Y.

    1990-05-01

    Though diketopiperazines (DKP) are formed in most experiments concerning the prebiotic peptide formation, the molecules have not been paid attention in the studies of chemical evolution. We have found that triglycine, tetraglycine or pentaglycine are formed in aqueous solution of glycine anhydride (DKP) and glycine, diglycine or triglycine, respectively. A reaction of alanine with DKP resulted in the formation of glycylglycylalanine under the same conditions. These results indicate that the formation of the peptide bonds proceeds through the nucleophilic attack of an amino group of the amino acids or the oligoglycines on the DKP accompanied by the ring-opening. The formation of glycine anhydride, di-, tri- and tetraglycine was also observed in a mixed aqueous solution of urea and glycine in an open system to allow the evaporation of ammonia. A probable pathway is proposed for prebiotic peptide formation through diketopiperazine on the primitive Earth.

  7. Zinc chloride aqueous solution as a solvent for starch.

    Science.gov (United States)

    Lin, Meiying; Shang, Xiaoqin; Liu, Peng; Xie, Fengwei; Chen, Xiaodong; Sun, Yongyi; Wan, Junyan

    2016-01-20

    It is important to obtain starch-based homogeneous systems for starch modification. Regarding this, an important key point is to find cheap, low-cost and low-toxicity solvents to allow complete dissolution of starch and its easy regeneration. This study reveals that a ZnCl2 aqueous solution is a good non-derivatizing solvent for starch at 50 °C, and can completely dissolve starch granules. The possible formation of a "zinc-starch complex" might account for the dissolution; and the degradation of starch, which was caused by the H(+) inZnCl2 aqueous solution, could not contribute to full dissolution. From polarized light microscopic observation combined with the solution turbidity results, it was found that the lowest ZnCl2 concentration for full dissolution was 29.6 wt.% at 50 °C, with the dissolving time being 4h. Using Fourier-transform infrared (FTIR), solid state (13)C nuclear magnetic resonance (NMR), and X-ray diffraction (XRD), it was revealed that ZnCl2 solution had no chemical reaction with starch glucosides, but only weakened starch hydrogen bonding and converted the crystalline regions to amorphous regions. In addition, as shown by intrinsic viscosity and thermogravimetric analysis (TGA), ZnCl2 solution caused degradation of starch macromolecules, which was more serious with a higher concentration of ZnCl2 solution.

  8. Fractional Walden rule for electrolytes in supercooled disaccharide aqueous solutions.

    Science.gov (United States)

    Longinotti, M Paula; Corti, Horacio R

    2009-04-23

    The electrical conductivity of CsCl, KCl, Bu(4)NBr, and Bu(4)NI was studied in stable and supercooled (metastable) sucrose and trehalose aqueous solutions over a wide viscosity range. The results indicate that large positive deviations from the Walden rule occur in these systems due to the higher tendency of the ions to move in water-rich regions, as previously observed for NaCl and MgCl(2). The electrical molar conductivity viscosity dependence can be described with a fractional Walden rule (Lambdaeta(alpha) = constant), where alpha is a decoupling parameter which increases with ionic size and varies between 0.61 and 0.74 for all of the studied electrolytes. Using the electrical molar conductivity dependence of ion-ion interactions, an effective dielectric constant was calculated for a trehalose 39 wt% aqueous solution as a function of temperature. Above 278 K, the effective and the bulk solution dielectric constants are similar, but at lower temperatures, where the carbohydrate becomes less mobile than water, the effective dielectric constant approaches the dielectric constant of water. We also conclude that the solute-solvent dielectric friction contribution can be neglected, reinforcing the idea that the observed breakdown of the Walden rule is due to the existence of local microheterogeneities. The Walden plots for the studied ionic solutes show a decoupling similar to that found for the diffusion of water in the same solutions.

  9. Pulse Radiolysis of Adrenaline in Acid Aqueous Solutions

    DEFF Research Database (Denmark)

    Gohn, M.; Getoff, N.; Bjergbakke, Erling

    1976-01-01

    Pulse radiolysis of adrenaline in acid aqueous solutions (pH 1–3) was carried out. The rate constants for the reactions of adrenaline with H and OH were determined: k(H + adr.) = (0·9±0·1) × 109 dm3 mol−1s−1; k(OH + adr.) = (1·65±0·15) × 1010 dm3 mol−1s−1. The H-adduct of adrenaline has two λmax...

  10. EXAFS studies of actinide ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Karim, D P; Georgopoulos, P; Knapp, G S

    1979-01-01

    The applicability of the EXAFS technique in the study of actinide systems is discussed. Uranium L/sub III/-edge spectra obtained on an in-lab rotating anode EXAFS facility are presented and analyzed for crystalline UO/sub 2/F/sub 2/ and aqueous solutions containing hexavalent uranium ions. Methods for the extension of the technique to more dilute systems are discussed.

  11. Degradation of α-Naphthol by Plasma in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Degradation of α-naphthol induced by plasma in aqueous solution was investigatedin different initial concentration with contact glow discharge electrolysis(CGDE). The resultsshowed that the degradation of α-naphthol obeyed the first-rate law. Some of predominant products were analyzed by a high performance liquid chromatography (HPLC). A path of α-naphtholdisappearance caused by plasma was proposed according to the detected intermediate products.

  12. Plasma Induced Degradation of Benzidine in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    高锦章; 盖克; 杨武; 董彦杰

    2003-01-01

    The degradation of benzidine in aqueous solution by the low temperature plasmawas examined. The results showed that the concentration of medium and the value of pH have anappreciable effect on the degradation of benzidine. What is more important is that iron ions actingas a catalyst play an important role in this reaction. For exploring the degradation mechanismof benzidine, some of the intermediate products were recorded by HPLC(high performance liquidchromatography).

  13. Angular correlation of annihilation photons in frozen aqueous solutions

    DEFF Research Database (Denmark)

    Milosevic-Kvajic, M.; Mogensen, O. E.; Kvajic, G.

    1972-01-01

    Linear‐slit angular correlation curves were obtained at about −140°C for frozen aqueous solutions of HF, HCl, HBr, HI, NH3, FeCl2, FeCl3, NaI, H2SO4, NHO3, MnSO4, KMnO4, K2Cr2O7, NaOH, and LiOH. We found no appreciable influence of a 4% concentration of the last seven impurities. Only halide‐cont...

  14. Micellization of Zonyl FSN-100 Fluorosurfactant in Aqueous Solutions

    OpenAIRE

    Skvarla, Juraj; Uchman, M.; Procházka, K.; Tošner, Z.; Garamus, V. M.; Pispas, S.; Štěpánek, M.

    2014-01-01

    We report on micellization of nonionic fluorosurfactant Zonyl FSN-100 in aqueous solutions studied by means of NMR spectroscopy, light and small-angle X-ray scattering, surface tension measurements, isothermal titration calorimetry and fluorescence spectroscopy. The results allow for determination of basic parameters of Zonyl FSN-100 association like critical micellar concentration, size and association number of Zonyl FSN-100 micelles which have a core–shell structure with the core of fluoro...

  15. Removal of arsenic from aqueous solution using electrocoagulation.

    Science.gov (United States)

    Balasubramanian, N; Kojima, Toshinori; Basha, C Ahmed; Srinivasakannan, C

    2009-08-15

    Removal of arsenic from aqueous solution was carried out using electrocoagulation. Experiments were conducted using mild steel sacrificial anode covering wide range in operating conditions to assess the removal efficiency. The maximum arsenic removal efficiency was recorded as 94% under optimum condition. The electrocoagulation mechanism of arsenic removal has been developed to understand the effect of applied charge and electrolyte pH on arsenic removal efficiency. Further the experimental data were tested with different adsorption isotherm model to describe the electrocoagulation process.

  16. Adsorption of Copper from Aqueous Solution Using Mango Seed Powder

    OpenAIRE

    Samiksha V. Ashtikar; Amruta D. Parkhi

    2014-01-01

    The objective of the study was the removal of copper metal ions from aqueous solution using mango seed powder as low cost adsorbent. The influences of contact time, adsorbent doses & temperature were studied in batch experiments at room temperature. The results showed that with increase in the contact time percent removal of copper increases. The adsorption was rapid during first 45 minutes & equilibrium was reached in 90 minutes. The results also showed that with increase in ...

  17. Removal of fluoride ions from aqueous solution by waste mud

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-09-15

    The present study was carried out to assess the ability of original waste mud (o-WM) and different types of activated waste mud which are acid-activated (a-WM) and precipitated waste mud (p-WM), in order to remove excess of fluoride from aqueous solution by using batch technique. The p-WM exhibited greater performance than the others. Adsorption studies were conducted as a function of pH, contact time, initial fluoride concentration, adsorbent concentration, temperature, etc. Studies were also performed to understand the effect of some co-existing ions present in aqueous solutions. Adsorption process was found to be almost independent of pH for all types of waste mud. Among the kinetic models tested for p-WM, pseudo-second-order model fitted the kinetic data well with a perfect correlation coefficient value of 1.00. It was found that the adequate time for the adsorption equilibrium of fluoride was only 1 h. Thermodynamic parameters including the Gibbs free energy ({Delta}G{sup o}), enthalpy ({Delta}H{sup o}), and entropy ({Delta}S{sup o}) revealed that adsorption of fluoride ions on the p-WM was feasible, spontaneous and endothermic in the temperature range of 0-40 deg. C. Experimental data showed a good fit with the Langmuir and Freundlich adsorption isotherm models. Results of this study demonstrated the effectiveness and feasibility of WM for removal of fluoride ions from aqueous solution.

  18. Dermal absorption of a dilute aqueous solution of malathion

    Directory of Open Access Journals (Sweden)

    Scharf John

    2008-01-01

    Full Text Available Malathion is an organophosphate pesticide commonly used on field crops, fruit trees, livestock, agriculture, and for mosquito and medfly control. Aerial applications can result in solubilized malathion in swimming pools and other recreational waters that may come into contact with human skin. To evaluate the human skin absorption of malathion for the assessment of risk associated with human exposures to aqueous solutions, human volunteers were selected and exposed to aqueous solutions of malathion. Participants submerged their arms and hands in twenty liters of dilute malathion solution in either a stagnant or stirred state. The "disappearance method" was applied by measuring malathion concentrations in the water before and after human exposure for various periods of time. No measurable skin absorption was detected in 42% of the participants; the remaining 58% of participants measured minimal absorbed doses of malathion. Analyzing these results through the Hazard Index model for recreational swimmer and bather exposure levels typically measured in contaminated swimming pools and surface waters after bait application indicated that these exposures are an order of magnitude less than a minimal dose known to result in a measurable change in acetylcholinesterase activity. It is concluded that exposure to aqueous malathion in recreational waters following aerial bait applications is not appreciably absorbed, does not result in an effective dose, and therefore is not a public health hazard.

  19. Catalytic oxidation of calcium sulfite in solution/aqueous slurry

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-qin; WU Zhong-biao; WANG Da-hui

    2004-01-01

    Forced oxidation of calcium sulfite aqueous slurry is a key step for the calcium-based flue gas desulfurization(FGD) residue. Experiments were conducted in a semi-batch system and a continuous flow system on lab scales. The main reactor in semi-batch system is a 1000 ml volume flask. It has five necks for continuous feeding of gas and a batch of calcium sulfite solution/aqueous slurry. In continuous flow system, the main part is a jacketed Pyrex glass reactor in which gas and solution/aqueous slurry are fed continuously. Calcium sulfite oxidation is a series of complex free-radical reactions. According to experimental results and literature data, the reactions are influenced significantly by manganese as catalyst. At low concentration of manganese and calcium sulfite, the reaction rate is dependent on 1.5 order of sulfite concentration, 0.5 order of manganese concentration, and zero order of oxygen concentration in which the oxidation is controlled by chemical kinetics. With concentrations of calcium sulfite and manganese increasing, the reactions are independent gradually on the constituents in solution but are impacted by oxygen concentration. Manganese can accelerate the free-radical reactions, and then enhances the mass transfer of oxygen from gas to liquid. The critical concentration of calcium sulfite is 0.007 mol/L, manganese is 10-4 mol/L, and oxygen is of 0.2-0.4 atm.

  20. Direct photolysis of nitroaromatic compounds in aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    CHEN Bing; YANG Chun; GOH Ngoh Khang

    2005-01-01

    The direct photolysis of nitrobenzene and nitrophenols in aqueous solutions irradiated by polychromatic light were investigated.Several aromatic intermediates were identified as three nitrophenol isomers, nitrohydroquinone, nitrosobenzene, nitrocatechol, catechol and phenol. Nitrite and nitrate ions were also detected in the irradiated solution indicating direct photolysis of nitrobenzene or nitrophenols.The degradation of nitrobenzene and nitrophenols and the formation of three nitrophenol isomers were observed to follow zero-order kinetics. The quantum yields for nitrobenzene and nitrophenols removal are about 10-3 and 10-3-10-4 respectively. The mechanism for nitrobenzene degradation was suggested to follow mainly nitro-nitrite intramolecular arrangement.

  1. Analysis and modeling of alkali halide aqueous solutions

    DEFF Research Database (Denmark)

    Kim, Sun Hyung; Anantpinijwatna, Amata; Kang, Jeong Won;

    2016-01-01

    A new model is proposed for correlation and prediction of thermodynamic properties of electrolyte solutions. In the proposed model, terms of a second virial coefficient-type and of a KT-UNIFAC model are used to account for a contribution of binary interactions between ion and ion, and water and ion...... on calculations for various electrolyte properties of alkali halide aqueous solutions such as mean ionic activity coefficients, osmotic coefficients, and salt solubilities. The model covers highly nonideal electrolyte systems such as lithium chloride, lithium bromide and lithium iodide, that is, systems...

  2. Radiolysis of berberine or palmatine in aqueous solution

    Science.gov (United States)

    Marszalek, Milena; Wolszczak, Marian

    2011-01-01

    The reactions of hydrated electron (eaq-), hydrogen atom (H rad ) (reducing species) and Cl2•-, Br2•-, N,O•H radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of eaq- and rad OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with eaq- and radicals generated during radiolysis are unstable and undergo further reactions.

  3. Radiolytic degradation of atrazine aqueous solution containing humic substances.

    Science.gov (United States)

    Basfar, A A; Mohamed, K A; Al-Abduly, A J; Al-Shahrani, A A

    2009-03-01

    Degradation of atrazine herbicide in humic substances (HS) aqueous solutions and distilled water solutions was investigated on a laboratory scale upon gamma-irradiation from a (60)Co source. In addition, the effect of ionizing radiation on the atrazine residues removal efficiency was investigated in relation to degradation of by-products. gamma-Irradiation experiments were carried out for three targeted concentrations (i.e. 0.464, 2.318 and 4.636 microM) with doses over the range 0.1-60 kGy. The initial concentration of herbicide, scavengers and irradiation doses play a significant role in the degradation efficiency as shown by decay constants of atrazine residues. gamma-Radiolysis showed that atrazine exhibited high degradation percentages at low absorbed doses in HS aqueous solutions compared to distilled water solutions. Absorbed doses from 0.6 to 21 kGy and from 6 to 72 kGy at a dose rate of 14.52 kGyh(-1) achieved 90% degradation for atrazine with initial concentrations over the range 0.464-4.636 microM in humic and distilled water solutions, respectively. The radiolytic degradation by-products and their mass balances were qualitatively determined with good confidence using gas chromatography/quadruple mass spectrometry (GC/MS) with electron impact ionization (EI(+)) mode.

  4. Photodegradation in Micellar Aqueous Solutions of Erythrosin Esters Derivatives.

    Science.gov (United States)

    Herculano, Leandro Silva; Lukasievicz, Gustavo Vinicius Bassi; Sehn, Elizandra; Caetano, Wilker; Pellosi, Diogo Silva; Hioka, Noboru; Astrath, Nelson Guilherme Castelli; Malacarne, Luis Carlos

    2015-07-01

    Strong light absorption and high levels of singlet oxygen production indicate erythrosin B as a viable candidate as a photosensitizer in photodynamic therapy or photodynamic inactivation of microorganisms. Under light irradiation, erythrosin B undergoes a photobleaching process that can decrease the production of singlet oxygen. In this paper, we use thermal lens spectroscopy to investigate photobleaching in micellar solutions of erythrosin ester derivatives: methyl, butyl, and decyl esters in low concentrations of non-ionic micellar aqueous solutions. Using a previously developed thermal lens model, it was possible to determine the photobleaching rate and fluorescence quantum efficiency for dye-micelle solutions. The results suggest that photobleaching is related to the intensity of the dye-micelle interaction and demonstrate that the thermal lens technique can be used as a sensitive tool for quantitative measurement of photochemical properties in very diluted solutions.

  5. Corrosion behavior of bulk metallic glasses in different aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The corrosion behavior of as-cast fully amorphous, structural relaxed amorphous and crystallized Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glasses (BMGs) in NaCl, HCl and NaOH solutions was investigated by electrochemical polarization and immersion methods. X-ray photoelectron spectroscopy measurements was used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The corrosion resistance of the Fe65.5Cr4Mo4Ga4P12C5B5.5 BMG was better than its structural relaxation/crystallization counterparts and common alloys (such as stainless steel, carbonized steel, and steel) in the selected aqueous solutions. The high corrosion resistance of this alloy in corrosive solutions leads to the formation of Fe-, Cr- and Mo-enriched protective thin surface films.

  6. Structure of concentrated aqueous solutions of scandium chloride

    Science.gov (United States)

    Smirnov, P. R.; Grechin, O. V.

    2017-03-01

    It is shown via X-ray diffraction that aqueous solutions of scandium chloride form ionic associates in a wide range of concentrations. It is established that the Sc3+ ion coordination number increases upon dilution to 8.2 at an unchanged Sc3+-OH2 distance of 0.215 nm. The second coordination sphere of the cation forms at an average distance of 0.420 nm. The number of solvent molecules in the sphere logically increases during dilution. It is concluded that the anion does not form its own sphere in highly concentrated solutions. This coordination sphere begins to form only in solutions with moderate concentrations at a distance of 0.315 nm, and it contains six water molecules in diluted solutions.

  7. On the structure of an aqueous propylene glycol solution

    Science.gov (United States)

    Rhys, Natasha H.; Gillams, Richard J.; Collins, Louise E.; Callear, Samantha K.; Lawrence, M. Jayne; McLain, Sylvia E.

    2016-12-01

    Using a combination of neutron diffraction and empirical potential structure refinement computational modelling, the interactions in a 30 mol. % aqueous solution of propylene glycol (PG), which govern both the hydration and association of this molecule in solution, have been assessed. From this work it appears that PG is readily hydrated, where the most prevalent hydration interactions were found to be through both the PG hydroxyl groups but also alkyl groups typically considered hydrophobic. Hydration interactions of PG dominate the solution over PG self-self interactions and there is no evidence of more extensive association. This hydration behavior for PG in solutions suggests that the preference of PG to be hydrated rather than to be self-associated may translate into a preference for PG to bind to lipids rather than itself, providing a potential explanation for how PG is able to enhance the apparent solubility of drug molecules in vivo.

  8. Adsorption of nicotine on different zeolite types, from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Stošić Dušan K.

    2007-01-01

    Full Text Available The plant alkaloid, nicotine, is a strongly toxic heterocyclic compound: the lethal dose for an adult human being (40-60 mg is importantly lower in comparison with the other known poisons such as arsenic or strychni­ne. Cigarettes represent "the most toxic and addictive form of nicotine". Besides the negative effects of nicotine on public health produced by self-administration, recently another potentially very dangerous effect has been recognized: because of its miscibility with water, nicotine can be found in industrial wastewaters, and consequently, in groundwater. Therefore, the problem of nicotine removal from aqueous solutions has became an interesting topic. In this work, the removal of nicotine has been probed by adsorption on solid materials. Adsorption of nicotine on different zeolites (clinoptilolite, ZSM-5 and β zeolite and on activated carbon was investigated from aqueous solutions, at 298 K. The obtained results are presented as adsorption isotherms: the amount of adsorbed nicotine as a function of equilibrium concentration. These data were obtained from the residual amount of nicotine in the aqueous phase, by the use of UV spectroscopy. The highest amounts of adsorbed nicotine was found for activated carbon and p zeolite (~ mmol·g-1. The attempt to modify the adsorption properties of ZSM-5 zeolite has been also done: ZSM-5 was modified by ion-exchange with VIII group metal (Cu2+ and Fe3+. In addition, the adsorption of nicotine on ZSM-5 zeolite with different Si/Al ratios has been done. It has been noticed that ion-exchange did not improve the adsorption possibilities, while the adsorption was importantly lower in the case of higher silicon content in ZMS-5 structure. 13C NMR spectra were collected for suspensions formed of solid adsorbent and aqueous solution of nicotine; in this way, the part of nicotine molecule which is most probably connected with the adsorbent was recognized.

  9. The Gibbs-free-energy landscape for the solute association in nanoconfined aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    赵亮; 王春雷; 方海平; 涂育松

    2015-01-01

    The theoretical model and the numerical analyses on the Gibbs-free-energy of the association states of am-phiphilic molecules in nanoconfined aqueous solutions are presented in detail. We exhibit the continuous change of the Gibbs-free-energy trend, which plays a critical role in the association states of the system transforming from the dispersion state, through the “reversible state”, and finally to the aggregation state in amphiphilic molecule solutions. Furthermore, for the“reversible state”, we present the difference in the free-energy bar-rier heights of the dispersion state and aggregation state, resulting from the competition between the entropy, which makes the solute molecules evenly disperse in the solution and the energy contribution driving the am-phiphilic molecules to aggregate into a larger cluster. These findings provide a comprehensive understanding of confinement effects on the solute association processes in aqueous solutions and may further improve the techniques of material fabrication.

  10. Selection of forward osmosis draw solutes for subsequent integration with anaerobic treatment to facilitate resource recovery from wastewater.

    Science.gov (United States)

    Ansari, Ashley J; Hai, Faisal I; Guo, Wenshan; Ngo, Hao H; Price, William E; Nghiem, Long D

    2015-09-01

    Forward osmosis (FO) can be used to extract clean water and pre-concentrate municipal wastewater to make it amenable to anaerobic treatment. A protocol was developed to assess the suitability of FO draw solutes for pre-concentrating wastewater for potential integration with anaerobic treatment to facilitate resource recovery from wastewater. Draw solutes were evaluated in terms of their ability to induce osmotic pressure, water flux, and reverse solute flux. The compatibility of each draw solute with subsequent anaerobic treatment was assessed by biomethane potential analysis. The effect of each draw solute (at concentrations corresponding to the reverse solute flux at ten-fold pre-concentration of wastewater) on methane production was also evaluated. The results show that ionic organic draw solutes (e.g., sodium acetate) were most suitable for FO application and subsequent anaerobic treatment. On the other hand, the reverse solute flux of inorganic draw solutions could inhibit methane production from FO pre-concentrated wastewater.

  11. RHEOLOGICAL BEHAVIOR OF ERWINIA GUM IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Li-na Zhang; Mei Zhang; Jing-hua Chen; Hideki Iijima; Hiromichi Tsuchiya

    1999-01-01

    Erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose and glucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and a rotational viscometer. Its weight-average molecular weight Mw and intrinsic viscosity [η] in 0.2 mol/L NaCl aqueous solution were measured by light scattering method at 35℃ and viscometry at 25℃ and found to be 1.06 × 106 g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gel permeation chromatography (GPC). These results indicated that E gum in water has exceedingly high viscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreased with increasing temperature, and the turning point appeared at 38℃ for dilute solution and 80℃ for concentrated solution suggesting that the aggregates of E gum in water started to disaggregate under these temperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimental results indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.

  12. Monte Carlo Simulation of Aqueous Dilute Solutions of Polyhydric Alcohols

    Science.gov (United States)

    Lilly, Arnys Clifton, Jr.

    In order to investigate the details of hydrogen bonding and solution molecular conformation of complex alcohols in water, isobaric-isothermal Monte Carlo simulations were carried out on several systems. The solutes investigated were ethanol, ethylene glycol, 1,2-propylene glycol, 1,3 -propylene glycol and glycerol. In addition, propane, which does not hydrogen bond but does form water hydrates, was simulated in aqueous solution. The complex alcohol-water systems are very nonideal in their behavior as a function of solute concentration down to very dilute solutions. The water model employed was TIP4P water^1 and the intermolecular potentials employed are of the Jorgensen type^2 in which the interactions between the molecules are represented by interaction sites usually located on nuclei. The interactions are represented by a sum of Coulomb and Lennard-Jones terms between all intermolecular pairs of sites. Intramolecular rotations in the solute are modeled by torsional potential energy functions taken from ethanol, 1-propanol and 2-propanol for C-O and C-C bond rotations. Quasi-component pair correlation functions were used to analyze the hydrogen bonding. Hydrogen bonds were classified as proton acceptor and proton donor bonds by analyzing the nearest neighbor pair correlation function between hydroxyl oxygen and hydrogen and between solvent-water hydrogen and oxygen. The results obtained for partial molar heats of solution are more negative than experimental values by 3.0 to 14 kcal/mol. In solution, all solutes reached a contracted molecular geometry with the OH groups generally on one side of the molecule. There is a tendency for the solute OH groups to hydrogen bond with water, with more proton acceptor bonds than proton donor bonds. The water -solute binding energies correlate with experimental measurements of the water-binding properties of the solute. ftn ^1Jorgensen, W. L. et al, J. Chem. Phys., 79, 926 (1983). ^2Jorgensen, W. L., J. Phys Chem., 87, 5304

  13. Simultaneous leaching and carbon sequestration in constrained aqueous solutions.

    Science.gov (United States)

    Moon, Ji-Won; Cho, Kyu-Seong; Moberly, James G; Roh, Yul; Phelps, Tommy J

    2011-12-01

    The behavior of metal ions' leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86 days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3 g CO(2)/kg FA after 86 days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO(2) capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86 days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals.

  14. Simultaneous leaching and carbon sequestration in constrained aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Phelps, Tommy Joe [ORNL; Moon, Ji Won [ORNL; Roh, Yul [Chonnam National University, Gwangju; Cho, Kyu Seong [ORNL

    2011-01-01

    The behavior of metal ions leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86 days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3 g CO(2)/kg FA after 86 days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO(2) capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86 days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals.

  15. Beryllium Chelation by Dicarboxylic Acids in Aqueous Solution.

    Science.gov (United States)

    Schmidt, Michael; Bauer, Andreas; Schmidbaur, Hubert

    1997-05-07

    Maleic and phthalic acids are found to react with Be(OH)(2), generated in situ from BeSO(4)(aq) and Ba(OH)(2)(aq), in aqueous solution at pH 3.0 or 4.4, respectively (25 degrees C), to give solutions containing the complexes (H(2)O)(2)Be[(OOCCH)(2)] (1) and (H(2)O)(2)Be[(OOC)(2)C(6)H(4)] (3). The products can be isolated in high yield and identified by microanalytical data. With 2 equiv of the dicarboxylic acids and the pH adjusted to 5.5 and 5.9, respectively, by addition of ammonia, the bis-chelate complexes [(NH(4))(+)](2){[Be[(OOCCH)(2)](2)}(2)(-) (2) and [(NH(4))(+)](2){Be[(OOC)(2)C(6)H(4)](2)}(2)(-) (4) are obtained, which can also be isolated. The compounds show distinct (9)Be, (1)H, and (13)C resonances in their NMR spectra in aqueous solutions. Layering of an aqueous solution of compound 4 with acetone at ambient temperature leads to the precipitation of single crystals suitable for an X-ray structure determination. This salt (5) was found to contain the bis-chelated dianion {Be[(OOC)(2)C(6)H(4)](2)}(2)(-) with the beryllium atom in the spiro center of two seven-membered rings and an overall geometry approaching closely C(2) symmetry. These anions are associated with two crystallographically independent but structurally similar counterions [MeC(O)CH(2)CMe(2)NH(3)](+), which are the product of a condensation reaction of the ammonium cation with the acetone solvent. In the crystal the ammonium hydrogen atoms of the cations form N-H.O hydrogen bonds with the oxo functions of the dianion.

  16. Nano particles@Calix arenas via aqueous solution

    Directory of Open Access Journals (Sweden)

    Sahar Dehghani

    2016-05-01

    Full Text Available The electronic structure and magnetic properties of Al2O3, GaN and Fe3O4@ Calix (8 COOH have been studied using ONIOM and DFT methods. The studies focus on how to improve the adsorption of some nano particles solution aqueous for achieving good magnetic and functionalized potential performances. The results revealed that the Fe3O4@ Calix (8 COOH and some of its derivations exhibited better thermodynamic stability. Furthermore, the particle size and magnetic property of the GaN@ Calix (8 COOH nano particles can be controlled by the aqueous. The electrical properties such as NMR Shielding, electron densities, energy densities, potential energy densities, ELF, LOL, ellipticity of electron density, eta index and ECP for nano particles@ Calix (8COOH have been calculated.

  17. Rapid structural analysis of nanomaterials in aqueous solutions

    Science.gov (United States)

    Ryuzaki, Sou; Tsutsui, Makusu; He, Yuhui; Yokota, Kazumichi; Arima, Akihide; Morikawa, Takanori; Taniguchi, Masateru; Kawai, Tomoji

    2017-04-01

    Rapid structural analysis of nanoscale matter in a liquid environment represents innovative technologies that reveal the identities and functions of biologically important molecules. However, there is currently no method with high spatio-temporal resolution that can scan individual particles in solutions to gain structural information. Here we report the development of a nanopore platform realizing quantitative structural analysis for suspended nanomaterials in solutions with a high z-axis and xy-plane spatial resolution of 35.8 ± 1.1 and 12 nm, respectively. We used a low thickness-to-diameter aspect ratio pore architecture for achieving cross sectional areas of analyte (i.e. tomograms). Combining this with multiphysics simulation methods to translate ionic current data into tomograms, we demonstrated rapid structural analysis of single polystyrene (Pst) beads and single dumbbell-like Pst beads in aqueous solutions.

  18. Hydrogen bond breaking in aqueous solutions near the critical point

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2001-01-01

    The nature of water-anion bonding is examined using X-ray absorption fine structure spectroscopy on a 1mZnBr2/6m NaBr aqueous solution, to near critical conditions. Analyses show that upon heating the solution from 25??C to 500??C, a 63% reduction of waters occurs in the solvation shell of ZnBr42-, which is the predominant complex at all pressure-temperature conditions investigated. A similar reduction in the hydration shell of waters in the Br- aqua ion was found. Our results indicate that the water-anion and water-water bond breaking mechanisms occurring at high temperatures are essentially the same. This is consistent with the hydration waters being weakly hydrogen bonded to halide anions in electrolyte solutions. ?? 2001 Elsevier Science B.V.

  19. Separation characteristics of alcohol from aqueous solution by ultrasonic atomization.

    Science.gov (United States)

    Yasuda, Keiji; Mochida, Kyosuke; Asakura, Yoshiyuki; Koda, Shinobu

    2014-11-01

    The generation rate of ultrasonically atomized droplets and the alcohol concentration in droplets were estimated by measuring the flow rate and the alcohol concentration of vapors from a bulk solution with a fountain. The effect of the alcohol concentration in the bulk solution on the generation rate of droplets and the alcohol concentration in droplets were investigated. The ultrasonic frequency was 2.4MHz, and ethanol and methanol aqueous solutions were used as samples. The generation rate of droplets for ethanol was smaller than that for methanol at the same alcohol molar fraction in the bulk solution. For both solutions, at low alcohol concentration in the bulk solution, the alcohol concentration in droplets was lower than that in vapors and the atomized droplets were visible. On the other side, at high concentration, the concentration in droplets exceeded that in vapors and the atomized droplets became invisible. These results could be explained that the alcohol-rich clusters in the bulk solution were preferentially atomized by ultrasonic irradiation. The concentration in droplets for ethanol was higher than that for methanol at low alcohol concentration because the amount of alcohol-rich clusters was larger. When the alcohol molar fraction was greater than 0.6, the atomized droplets almost consisted of pure alcohol.

  20. Removal of Cholera Toxin from Aqueous Solution by Probiotic Bacteria

    Directory of Open Access Journals (Sweden)

    Jussi A. O. Meriluoto

    2012-06-01

    Full Text Available Cholera remains a serious health problem, especially in developing countries where basic hygiene standards are not met. The symptoms of cholera are caused by cholera toxin, an enterotoxin, which is produced by the bacterium Vibrio cholerae. We have recently shown that human probiotic bacteria are capable of removing cyanobacterial toxins from aqueous solutions. In the present study we investigate the ability of the human probiotic bacteria, Lactobacillus rhamnosus strain GG (ATCC 53103 and Bifidobacterium longum 46 (DSM 14583, to remove cholera toxin from solution in vitro. Lactobacillus rhamnosus strain GG and Bifidobacterium longum 46 were able to remove 68% and 59% of cholera toxin from aqueous solutions during 18 h of incubation at 37 °C, respectively. The effect was dependent on bacterial concentration and L. rhamnosus GG was more effective at lower bacterial concentrations. No significant effect on cholera toxin concentration was observed when nonviable bacteria or bacterial supernatant was used.

  1. Preparation of fluorescent polyaniline nanoparticles in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Kleber G. B. [Universidade Federal de Pernambuco, Departamento de Engenharia Mecanica (Brazil); Melo, Etelino F. de [Universidade Federal de Pernambuco, Departamento de Quimica Fundamental (Brazil); Andrade, Cesar A. S. [Universidade Federal de Pernambuco, Departamento de Bioquimica (Brazil); Melo, Celso P. de, E-mail: celso@df.ufpe.br [Universidade Federal de Pernambuco, Departamento de Fisica (Brazil)

    2013-01-15

    We report the synthesis of stable polyaniline nanoparticles (PANI{sub N}Ps) based on the chemical oxidative polymerization of aniline in aqueous solutions of surfactants. Surfactants of three different types-cationic (dodecyltrimethylammonium bromide-DTAB), anionic (sodium dodecyl sulfate-SDS), and non-ionic (Triton X-405-TX-405)-were used. The resulting PANI{sub N}Ps{sub s}urfactant samples were characterized through UV-Vis, fluorescence and Fourier transform infrared spectroscopies, and scanning electronic microscopy (SEM). We have verified that the color of the PANI{sub N}Ps{sub s}urfactant dispersions is affected by a change in the pH of the solution. The PANI-NPs{sub s}urfactant colloidal suspensions in aqueous solution present a surprising high fluorescence quantum yield value (ranging from 1.9 Multiplication-Sign 10{sup -3} to 6.9 Multiplication-Sign 10{sup -3}) that can be controlled as a function of the pH, a fact that we associate to the corresponding protonation degree of the PANI polymeric chains. We suggest that these fluorescent nanocomposites can find important technological applications in different areas such as organic light emitting devices, biosensors, and pigments for coatings.

  2. Lubrication, adsorption, and rheology of aqueous polysaccharide solutions.

    Science.gov (United States)

    Stokes, Jason R; Macakova, Lubica; Chojnicka-Paszun, Agnieszka; de Kruif, Cornelis G; de Jongh, Harmen H J

    2011-04-05

    Aqueous lubrication is currently at the forefront of tribological research due to the desire to learn and potentially mimic how nature lubricates biotribological contacts. We focus here on understanding the lubrication properties of naturally occurring polysaccharides in aqueous solution using a combination of tribology, adsorption, and rheology. The polysaccharides include pectin, xanthan gum, gellan, and locus bean gum that are all widely used in food and nonfood applications. They form rheologically complex fluids in aqueous solution that are both shear thinning and elastic, and their normal stress differences at high shear rates are found to be characteristic of semiflexible/rigid molecules. Lubrication is studied using a ball-on-disk tribometer with hydrophobic elastomer surfaces, mimicking biotribological contacts, and the friction coefficient is measured as a function of speed across the boundary, mixed, and hydrodynamic lubrication regimes. The hydrodynamic regime, where the friction coefficient increases with increasing lubricant entrainment speed, is found to depend on the viscosity of the polysaccharide solutions at shear rates of around 10(4) s(-1). The boundary regime, which occurs at the lowest entrainment speeds, depends on the adsorption of polymer to the substrate. In this regime, the friction coefficient for a rough substrate (400 nm rms roughness) is dependent on the dry mass of polymer adsorbed to the surface (obtained from surface plasmon resonance), while for a smooth substrate (10 nm rms roughness) the friction coefficient is strongly dependent on the hydrated wet mass of adsorbed polymer (obtained from quartz crystal microbalance, QCM-D). The mixed regime is dependent on both the adsorbed film properties and lubricant's viscosity at high shear rates. In addition, the entrainment speed where the friction coefficient is a minimum, which corresponds to the transition between the hydrodynamic and mixed regime, correlates linearly with the ratio

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

    Science.gov (United States)

    Rivlin, Michal; Eliav, Uzi; Navon, Gil

    2014-05-01

    Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2 ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0 ± 1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼104 s-1 at pH 7.4 and 37 °C, the activation energy, 50.2 kJ/mol and its pH dependence at 1.1 °C was fitted to: k (s-1) = 520 + 6.5 × 107[H+] + 3.0 × 109[OH-].

  4. Characterization of aqueous silver nitrate solutions for leakage tests

    Directory of Open Access Journals (Sweden)

    José Ferreira Costa

    2011-06-01

    Full Text Available OBJECTIVE: To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. MATERIAL AND METHODS: A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled and three brands of silver nitrate salt (Merck, Synth or Cennabras at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h and concentrations (1, 5, 25, 50% of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%. RESULTS: The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9. Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm. In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000. CONCLUSIONS: Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were

  5. Characterization of aqueous silver nitrate solutions for leakage tests

    Science.gov (United States)

    COSTA, José Ferreira; SIQUEIRA, Walter Luiz; LOGUERCIO, Alessandro Dourado; REIS, Alessandra; de OLIVEIRA, Elizabeth; ALVES, Cláudia Maria Coelho; BAUER, José Roberto de Oliveira; GRANDE, Rosa Helena Miranda

    2011-01-01

    Objectives To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. Material and Methods A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled) and three brands of silver nitrate salt (Merck, Synth or Cennabras) at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h) and concentrations (1, 5, 25, 50%) of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%). Results The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9). Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm). In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000). Conclusions Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were capable of

  6. ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ON ATTAPULGITE

    Institute of Scientific and Technical Information of China (English)

    WANG Deping; LV Pengfei; YAN Yongsheng; LIU Hui; WANG Guanjun

    2007-01-01

    Batch adsorption experiments were carried out for the removal of methylene blue (MB) from aqueous solution using attapulgite as adsorbent. The effects of various parameters such as temperature, contact time, the pH value, and attapulgite dosage on the adsorption performance were investigated. The standard curve and regression equation were established by spectrophotometry. The adsorption experimental results showed that the adsorption equilibrium data were well in accord with Langmuir adsorptive model. The optimal result was acquired under the experimental condition of attapulgite dosage 0.18g, MB concentration 50.0mg/L, pH 10, and adsorption time 20min at room temperature.

  7. Kinetics of gibbsite leaching in sodium hydroxide aqueous solution

    Directory of Open Access Journals (Sweden)

    Pavlović Ljubica J.

    2002-01-01

    Full Text Available In order to study the kinetics and mechanism of the reaction, laboratory leaching was carried out with industrially produced gibbsite γ-Al(OH3 in aqueous solutions containing an excess of sodium hydroxide. The results obtained reaction temperature, duration and base concentration varied. The basic kinetic parameters were determined from: the reaction rate constant k=8.72·107 exp (-74990/RT and the process activation energy in the range Ea=72.5-96.81 kJ/mol.

  8. Pulse radiolysis of pyridine and methylpyridines in aqueous solutions

    DEFF Research Database (Denmark)

    Solar, S.; Getoff, N.; Sehested, K.

    1993-01-01

    The radicals formed from pyridine, 3-methylpyridine, 3,5-dimethylpyridine, 2,6-dimethylpyridine and 2,4,6-trimethylpyridine by attack of H, e(aq)-, OH and O.- in aqueous solutions were investigated by pulse radiolysis in the pH-range 1-13.8. The UV-vis. absorption spectra as well as the formation...... and decay kinetics for the protonated and unprotonated forms of the methylpyridine radicals studied are presented. The pK(a)-values for the OH-adducts were determined....

  9. Hydrate-based heavy metal separation from aqueous solution

    Science.gov (United States)

    Song, Yongchen; Dong, Hongsheng; Yang, Lei; Yang, Mingjun; Li, Yanghui; Ling, Zheng; Zhao, Jiafei

    2016-02-01

    A novel hydrate-based method is proposed for separating heavy metal ions from aqueous solution. We report the first batch of experiments and removal characteristics in this paper, the effectiveness and feasibility of which are verified by Raman spectroscopy analysis and cross-experiment. 88.01-90.82% of removal efficiencies for Cr3+, Cu2+, Ni2+, and Zn2+ were obtained. Further study showed that higher R141b-effluent volume ratio contributed to higher enrichment factor and yield of dissociated water, while lower R141b-effluent volume ratio resulted in higher removal efficiency. This study provides insights into low-energy, intensive treatment of wastewater.

  10. Fluorescence of aqueous solutions of commercial humic products

    Science.gov (United States)

    Gosteva, O. Yu.; Izosimov, A. A.; Patsaeva, S. V.; Yuzhakov, V. I.; Yakimenko, O. S.

    2012-01-01

    We have studied the spectral luminescence characteristics of aqueous solutions of humic products obtained from different raw material sources, and their behavior as the excitation wavelength increases from 270 nm to 355 nm. We have identified differences in the spectral properties of industrial humic products from coalified materials, lignin-containing organic waste, and humic products from plant raw material (peat, sapropel, vermicompost). We have shown that humic products from plant raw material have spectral properties closer to those for humic substances in natural water or soil than humic products from coalified materials.

  11. Standard Electrode Potentials Involving Radicals in Aqueous Solution: Inorganic Radicals

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, David A.; Huie, Robert E.; Koppenol, Willem H.; Lymar, Sergei V.; Merenyi, Gabor; Neta, Pedatsur; Ruscic, Branko; Stanbury, David M.; Steenken, Steen; Wardman, Peter

    2015-12-01

    Recommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations

  12. Adsorption of Copper from Aqueous Solution Using Mango Seed Powder

    Directory of Open Access Journals (Sweden)

    Samiksha V. Ashtikar

    2014-04-01

    Full Text Available The objective of the study was the removal of copper metal ions from aqueous solution using mango seed powder as low cost adsorbent. The influences of contact time, adsorbent doses & temperature were studied in batch experiments at room temperature. The results showed that with increase in the contact time percent removal of copper increases. The adsorption was rapid during first 45 minutes & equilibrium was reached in 90 minutes. The results also showed that with increase in the adsorbent doses & temperature percent removal of copper increases. Thus mango seeds have the potential to be applied as alternative low-cost biosorbent in the remediation of heavy metal contamination in waste water.

  13. Removal of phenols from aqueous solutions by emulsion liquid membranes.

    Science.gov (United States)

    Reis, M Teresa A; Freitas, Ondina M F; Agarwal, Shiva; Ferreira, Licínio M; Ismael, M Rosinda C; Machado, Remígio; Carvalho, Jorge M R

    2011-09-15

    The present study deals with the extraction of phenols from aqueous solutions by using the emulsion liquid membranes technique. Besides phenol, two derivatives of phenol, i.e., tyrosol (2-(4-hydroxyphenyl)ethanol) and p-coumaric acid (4-hydroxycinnamic acid), which are typical components of the effluents produced in olive oil plants, were selected as the target solutes. The effect of the composition of the organic phase on the removal of solutes was examined. The influence of pH of feed phase on the extraction of tyrosol and p-coumaric was tested for the membrane with Cyanex 923 as an extractant. The use of 2% Cyanex 923 allowed obtaining a very high extraction of phenols (97-99%) in 5-6 min of contact time for either single solute solutions or for their mixtures. The removal efficiency of phenol and p-coumaric acid attained equivalent values by using the system with 2% isodecanol, but the removal rate of tyrosol was found greatly reduced. The extraction of tyrosol and p-coumaric acid from their binary mixture was also analysed for different operating conditions like the volume ratio of feed phase to stripping phase (sodium hydroxide), the temperature and the initial concentration of solute in the feed phase.

  14. Thermodynamics of multisolute adsorption from dilute aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Jossens, L. (Univ. Calif. Berkeley); Fritz, W.; Myers, A.L.; Prausnitz, J.M.; Schluender, E.U.

    1978-01-01

    Equilibrium adsorption data were obtained at 20/sup 0/C on activated carbon for six ternary aqueous systems simulating organic chemical wastewaters (phenol/p-nitrophenol, p-chlorophenol/p-nitrophenol, p-nitrophenol/benzoic acid, p-chlorophenol/phenyl acetic acid, o-phenylphenol/p-nitrophenol, and 2,4-dichlorophenol/dodecyl benzol sulfonic acid). The three-parameter Toth adsorption isotherm represented well the component single-solute data adsorption. With the thermodynamic ideal-adsorbed-solution method, total adsorptions were calculated from single-solute data predicted by the Toth equation and compared with experimental data. Prediction for total adsorption was within approx. 2-10Vertical Bar3<; for adsorption of individual components, within approx. 3-20Vertical Bar3<. A new three-parameter adsorption isotherm was derived, which also represented well the single-solute data. For bi-solute systems where dissociation is negligible, calculated individual adsorptions agreed with experiment within 2Vertical Bar3<. Systematic deviations between calculation and observed results may be due to the acidities of the solutes.

  15. Photoelectron Spectra of Aqueous Solutions from First Principles

    Energy Technology Data Exchange (ETDEWEB)

    Gaiduk, Alex P.; Govoni, Marco; Seidel, Robert; Skone, Jonathan H.; Winter, Bernd; Galli, Giulia

    2016-06-08

    We present a combined computational and experimental study of the photoelectron spectrum of a simple aqueous solution of NaCl. Measurements were conducted on microjets, and first-principles calculations were performed using hybrid functionals and many-body perturbation theory at the G0W0 level, starting with wave functions computed in ab initio molecular dynamics simulations. We show excellent agreement between theory and experiments for the positions of both the solute and solvent excitation energies on an absolute energy scale and for peak intensities. The best comparison was obtained using wave functions obtained with dielectric-dependent self-consistent and range-separated hybrid functionals. Our computational protocol opens the way to accurate, predictive calculations of the electronic properties of electrolytes, of interest to a variety of energy problems.

  16. Adsorption of thorium from aqueous solutions by perlite.

    Science.gov (United States)

    Talip, Z; Eral, M; Hiçsönmez, U

    2009-02-01

    The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

  17. Radiolysis of pentachlorophenol (PCP) in aqueous solution by gamma radiation

    Institute of Scientific and Technical Information of China (English)

    XUE Jun; WANG Jianlong

    2008-01-01

    Steady-state radiolysis experiments were performed to investigate the y-irradiation treatment of pentachlorophenol (PCP) in aqueoussolution. The effect of initial concentration on the PCP degradation was also investigated. The experimental results showed that γ-irradiation was able to degrade PCP in aqueous solution successfully, and the radiolytical degradation process of PCP could be describedby the first-order kinetic model. When the initial concentration of PCP was 25 and 50 mg/L and the radiation dose was 4 and 6 kGy,respectively, the degradation efficiency was 100%. A luminescence bacterial test was used for evaluating the toxicity of the radiolyticintermediate products. Total detoxification of a 75 mg/L PCP solution could be achieved by carrying out the irradiation procedure at the dose of 15 kGy.

  18. Rheological properties of aqueous solutions of biopolymeric hyaluronan

    Science.gov (United States)

    Szwajczak, Elzbieta

    2004-09-01

    Aqueous solutions of hyaluronic acid (hyaluronan, HA) were studied. The HA compound is a natural polysaccharide, bipolymer. It plays an important role in numerous biological processes as a component of the extracellular matrix, connective tissues and, especially, human and animal synovial joints. Natural and artificial solutions of the HA have demonstrated the viscoelastic nature. These properties are shown to be related to the microstructure parameters (bulk concentration, molecular weight) and external parameters (temperature, stress, shear rate). We emphasize the role of the flow properties of polymeric systems. It is found a liquid crystalline "order" can be "induced" during the material flow. The dynamic properties, such as the elastic shear modulus and viscous shear modulus, are given. These results are discussed in relation to the postulated function of hyaluronic acid in synovial joint and with respect to possibilities o their application in medicine and pharmacology.

  19. The crystal growth of barium flouride in aqueous solution

    Science.gov (United States)

    Barone, J. P.; Svrjcek, D.; Nancollas, G. H.

    1983-06-01

    The kinetics of growth of barium flouride seed crystals were investigated in aqueous solution at 25°C using a constant composition method, in which the supersaturation and ionic strength were maintained constant by the addition of titrants consisting of barium nitrate and potassium flouride solutions. The rates of reaction, studied over a range of supersaturation (σ ≈ 0.4 to 1.0), were interpreted in terms of crystal growth models. A spiral growth mechanism best describes the data, and scanning electron microscopy indicates a three-dimensional growth. In the presence of inorganic additives such as phosphate, however, induction periods precede a morphological two-dimensional crystallization. Coulter Counter results show little crystal agglomeration.

  20. Removal of phosphate from aqueous solution with blast furnace slag.

    Science.gov (United States)

    Oguz, Ensar

    2004-10-18

    Blast furnace slag was used to remove phosphate from aqueous solutions. The influence of pH, temperature, agitation rate, and blast furnace slag dosage on phosphate removal was investigated by conducting a series of batch adsorption experiments. In addition, the yield and mechanisms of phosphate removal were explained on the basis of the results of X-ray spectroscopy, measurements of zeta potential of particles, specific surface area, and images of scanning electron microscopy (SEM) of the particles before and after adsorption. The specific surface area of the blast furnace slag was 0.4m(2)g(-1). The removal of phosphate predominantly has taken place by a precipitation mechanism and weak physical interactions between the surface of adsorbent and the metallic salts of phosphate. In this study, phosphate removal in excess of 99% was obtained, and it was concluded that blast furnace slag is an efficient adsorbent for the removal of phosphate from solution.

  1. INTERACTION OF POLYVINYLPYRROLIDONE WITH METAL CHLORIDE AQUEOUS SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Mohammad Saleem Khan; Khaista Gul; Najeeb Ur Rehman

    2004-01-01

    Interactions of polyvinylpyrrolidone (PVP) with metal chlorides (MgCl2, CaCl2, KC1 and BaC12) have been investigated by viscometric and spectrophotometric techniques in aqueous solutions. Intrinsic viscosity [η] of (PVP) has shown a discontinuity with varying concentration of metal chlorides. The decreasing order of effectiveness of cation is K1+>Ca2+> Mg2+> Ba2+ for poly(vinylpyrrolidone) solution. Changes in the absorption spectra of the cosolutes were observed in the presence of PVP in the lower limit of the UV-visible region i.e. 200-210 nm. These changes were attributed to interaction of PVP molecules with the cosolute molecules. As the concentration of the cosolute increased, a red shift in the peaks was observed, indicating an increase in interaction between PVP and cosolutes.

  2. Removal of methylene blue from aqueous solution by graphene oxide.

    Science.gov (United States)

    Yang, Sheng-Tao; Chen, Sheng; Chang, Yanli; Cao, Aoneng; Liu, Yuanfang; Wang, Haifang

    2011-07-01

    Graphene oxide (GO) is a highly effective absorbent of methylene blue (MB) and can be used to remove MB from aqueous solution. A huge absorption capacity of 714 mg/g is observed. At initial MB concentrations lower than 250 mg/L, the removal efficiency is higher than 99% and the solution can be decolorized to nearly colorless. The removal process is fast and more efficient at lower temperatures and higher pH values. The increase of ionic strength and the presence of dissolved organic matter would further enhance the removal process when MB concentration is high. The results indicate that GO can be applied in treating industrial effluent and contaminated natural water. The implications to graphene-based environmental technologies are discussed.

  3. Radiolysis of berberine or palmatine in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Marszalek, Milena [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland); Wolszczak, Marian, E-mail: marianwo@mitr.p.lodz.p [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland)

    2011-01-15

    The reactions of hydrated electron (e{sub aq}{sup -}), hydrogen atom (H{sup {center_dot}}) (reducing species) and Cl{sub 2}{sup {center_dot}}{sup -},Br{sub 2}{sup {center_dot}}{sup -},{sup {center_dot}}N{sub 3},{sup {center_dot}}OH radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of e{sub aq}{sup -} and {sup {center_dot}}OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with e{sub aq}{sup -} and radicals generated during radiolysis are unstable and undergo further reactions.

  4. Influence of coal properties on mercury uptake from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Lakatos, J.; Brown, S.D.; Snape, C.E. [Miskolc University, Miskolc-Egyetemvaros (Hungary). Research Inst. of Applied Chemistry

    1999-10-01

    The uptake of mercury (II) from aqueous solution by a range of coals has been studied and the results have been compared to those for a number of other sorbents, including commercial active carbons and cation-exchange resins. At pH 5 in a buffer medium, the capacities for mercury removal of the low-rank coals and the oxidized bituminous coals investigated are comparable to those of the other sorbents tested. For the lignites investigated, a high content of organic sulfur does not markedly affect the capacity for mercury uptake in relatively neutral and low chloride media, owing to redox reactions being the most likely mechanism involved. However, in highly acidic solutions, the capacities for mercury uptake are considerably greater for the high-sulfur coals investigated than for their low-sulfur counterparts due to chelation being the major sorption process involved. 36 refs., 4 figs., 7 tabs.

  5. Aqueous Solution Thermal Conductivity of Beryllium-Subgroup Metal Chlorides

    Directory of Open Access Journals (Sweden)

    K. Abdullayev

    2013-01-01

    Full Text Available The paper presents experimental data on thermal conductivity of BeCl2 and SrCl2 salt aqueous solutions in the temperature range from 20 to 300 °С  and at various electrolyte concentrations  in mass percent. For the first time thermal conductivity of the system Н2О + BeCl2 has been investigated at high temperatures.The experimental results are described with the help of an empirical equation in the form of: λs = λo (1+ Am + Bm3/2 + Cm2,where λs  and λo – thermal conductivity coefficients of solution and water; A, B and C – coefficients depending on electrolyte nature; m – molality in units mol/kg.The formula error is less than  ±1 %.

  6. Modeling of sodium acetate recovery from aqueous solutions by electrodialysis.

    Science.gov (United States)

    Fidaleo, Marcello; Moresi, Mauro

    2005-09-05

    The main engineering parameters (i.e., ion transport numbers in solution and electro-membranes; effective solute and water transport numbers; effective membrane surface area, membrane surface resistances, and limiting current intensity) affecting the recovery of sodium acetate from model solutions by electrodialysis (ED) were determined in accordance with a sequential experimental procedure. Such parameters allowed a satisfactory simulation of a few validation tests carried out under constant or step-wisely variable current intensity. The performance of this ED process was characterized in terms of a current efficiency (omega) of about 93% in the constant-current region, a water transport number (t(W)) of about 15, and a specific energy consumption (epsilon) increasing from 0.14 to 0.31 kWh/kg for a solute recovery yield of 95% as the current density (j) was increased from 112 to 337 A/m2. The specific resistance of the anion- or cation-exchange membranes were found to be three or two times greater than those measured in aqueous NaCl solutions and are to be used to design and/or optimize ED stacks involved in the downstream processing of acetic acid fermentation broths.

  7. Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

    Science.gov (United States)

    Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    To evaluate the role of upper tropospheric and lower stratospheric aerosols in the global budget of methanol, the solubility and reactivity of CH3OH in aqueous sulfuric acid solutions are under investigation. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H(*), for methanol dissolution into 45 to 70 percent by weight H2SO4. We find that methanol solubility ranges from 10(exp 5) to 10(exp 8) M/atm and increases with decreasing temperature and with increasing sulfuric acid content. These solubility measurements include uptake due to physical solvation and all rapid equilibria which are established in solution. Our data indicate that simple uptake by aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These results differ from those recently reported in the literature, and an explanation of this disparity will be presented. In addition to solvation, reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H may proceed in the atmosphere but is not significant under our experimental conditions. Results obtained using a complementary equilibrium measurement technique confirm this directly. In addition, the extent of methanol sequestration via formation of mono- and dimethylsulfate will be evaluated under several atmospheric conditions.

  8. Removal of heavy metals from aqueous solution by sawdust adsorption

    Institute of Scientific and Technical Information of China (English)

    BULUT Yasemin; TEZ Zeki

    2007-01-01

    The adsorption of lead, cadmium and nicel from aqueous solution by sawdust of walnut was investigated. The effect of contact time,initial metal ion concentration and temperature on metal ions removal has been studied. The equilibrium time was found to be of the order of 60 min. Kinetics fit pseudo first-order, second-order and intraparticle diffusion models, hence adsorption rate constants were calculated. The adsorption data of metal ions at temperatures of 25, 45 and 60C have been described by the Freundlich and Langmuir isotherm models. The thermodynamic parameters such as energy, entropy and enthalpy changes for the adsorption of heavy metal ions have also been computed and discussed. Ion exchange is probably one of the major adsorption mechanisms for binding divalent metal ions to the walnut sawdust. The selectivity order of the adsorbent is Pb(Ⅱ)≈Cd(Ⅱ)>Ni(Ⅱ). From these results, it can be concluded that the sawdust of walnut could be a good adsorbent for the metal ions from aqueous solutions.

  9. New terahertz dielectric spectroscopy for the study of aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    George, Deepu K.; Charkhesht, Ali; Vinh, N. Q., E-mail: Vinh@vt.edu [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2015-12-15

    We present the development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As an important benchmark system, we report on the measurements of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17–37.36 cm{sup −1} or 0.268–60 mm). The system provides a coherent radiation source with power up to 20 mW in the gigahertz-to-terahertz region. The dynamic range of our instrument reaches 10{sup 12} and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with error bars of ±0.02 °C from 0 °C to 90 °C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  10. Gamma radiolytic degradation of naphthalene in aqueous solution

    Science.gov (United States)

    Chu, Libing; Yu, Shaoqing; Wang, Jianlong

    2016-06-01

    The decomposition of naphthalene in aqueous solution was studied using gamma irradiation combined with both H2O2 and TiO2 nanoparticles. Gamma irradiation led to a complete degradation of naphthalene and a partial mineralization. With initial concentration of 5-32 mg/L, more than 98% of naphthalene was removed and TOC reduction reached 28-31% at an absorbed dose of 3.0 kGy. The degradation of naphthalene was faster at neutral pH and the initial degradation rate increased with increasing the initial concentration of naphthalene. Addition of H2O2 and TiO2 nanoparticles all enhanced the degradation and mineralization of naphthalene. TOC removal efficiency increased from 28% (irradiation alone) to 35% with addition of H2O2 (40 mg/L), and to 48% with addition of TiO2 (0.8 g/L). The degradation of naphthalene in aqueous solution by gamma irradiation was mainly through the oxidation by ·OH radicals. The intermediate naphthol and carboxylic acids such as formic acid and oxalic acid were identified by LC-MS and IC.

  11. QENS study on thermal gelation in aqueous solution of methylcellulose

    Energy Technology Data Exchange (ETDEWEB)

    Onoda-Yamamuro, N. [Department of Natural Sciences, College of Science and Engineering, Tokyo Denki University, Hiki-gun, Saitama 350-0394 (Japan)]. E-mail: yamamuro@u.dendai.ac.jp; Yamamuro, O. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, 106-1 Shirakata, Tokai, Ibaraki 319-1106 (Japan); Inamura, Y. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, 106-1 Shirakata, Tokai, Ibaraki 319-1106 (Japan); Nomura, H. [Department of Natural Sciences, College of Science and Engineering, Tokyo Denki University, Hiki-gun, Saitama 350-0394 (Japan)

    2007-04-30

    Dynamics of water and methylcellulose (MC) molecules in MC aqueous solution has been studied by means of quasi-elastic neutron-scattering (QENS) measurements. The dynamic structure factor S(Q,E) of the MC aqueous solution was fitted well to the sum of Lorentzian and delta functions. The former is attributed to diffusive motion of water molecules and the latter to local vibrational motion of MC molecules. The self-diffusion coefficient of water molecules was obtained from the Q dependence of the half-width at half-maximum (HWHM) of the Lorentzian function, while the mean-square displacement of MC molecules from the Q dependence of the intensity of the delta term. Both the diffusion coefficient and the mean-square displacement gradually increased on heating and abruptly decreased around the thermal gelation temperature (around 320 K). The present results revealed that the microscopic motions of both water and MC molecules give rise to dynamic slowing down on thermal gelation.

  12. Radiation crosslinking of methylcellulose and hydroxyethylcellulose in concentrated aqueous solutions

    Science.gov (United States)

    Wach, Radoslaw A.; Mitomo, Hiroshi; Nagasawa, Naotsugu; Yoshii, Fumio

    2003-12-01

    The effects of ionizing radiation on aqueous solutions of cellulose ethers, methylcellulose (MC) and hydroxyethylcellulose (HEC) were investigated. The well-established knowledge states that cellulose and its derivatives belong to degrading type of polymers. However, in our study intermolecular crosslinking initiated by gamma rays or electron beam leaded to the formation of insoluble gel. This is an opposite effect of irradiation to the degradation. Paste-like form of the initial specimen, i.e. concentration 20-30%, when water plasticizes the bulk of polymer; and a high dose rate were favorable for hydrogel formation. Gel fraction up to 60% and 70% was obtained from solutions of HEC and MC, respectively. Produced hydrogels swell markedly in aqueous media by imbibing and holding the solvent. Radiation parameters of irradiation, such as yields of degradation and crosslinking and the gelation dose, were evaluated by sol-gel analysis on the basis of Charlesby-Rosiak equation. Despite of the crosslinked structure, obtained hydrogels can be included into the group of biodegradable materials. They undergo decomposition by the action of cellulase enzyme or microorganisms from compost.

  13. Pulse-Radiolysis of Aqueous KBrO4 Solutions

    DEFF Research Database (Denmark)

    Olsen, K. J.; Sehested, Knud; Appelman, L.H.

    1973-01-01

    Pulse-radiolysis of aqueous KBrO4 solutions show that BrO−4 reacts with e−aq by the reaction BrO−4 + e−aq → BrO−3 + O−. keaq + BrO−4 = (7.0 ± 0.7) × 109 M−1 sec−1. The reactions between BrO−4 and H, OH and O− are slow. The rate constants for these reactions are less than 107 M−1 sec−1.......Pulse-radiolysis of aqueous KBrO4 solutions show that BrO−4 reacts with e−aq by the reaction BrO−4 + e−aq → BrO−3 + O−. keaq + BrO−4 = (7.0 ± 0.7) × 109 M−1 sec−1. The reactions between BrO−4 and H, OH and O− are slow. The rate constants for these reactions are less than 107 M−1 sec−1....

  14. New terahertz dielectric spectroscopy for the study aqueous solutions

    CERN Document Server

    George, Deepu K; Vinh, N Q

    2015-01-01

    We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm-1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-to-terahertz region. The power signal-to-noise ratio of our instrument reaches 1015 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of 0.02 oC from above 0 oC to 90 oC. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  15. Examination of rheological properties of aqueous solutions of sodium caseinate

    Directory of Open Access Journals (Sweden)

    Jolanta Gawałek

    2012-12-01

    Full Text Available Application of sodium caseinate as a functional additive in manufacturing processes requires production of its concentrated aqueous solutions which, in industrial conditions, presents a number of difficulties. In order to develop an effective and optimal industrial process of mixing – manufacturing a concentrated solution of sodium caseinate, it is essential to know rheological properties in a definite range of concentrations changing in the course of the dissolving process. The material for investigations was typical commercial sodium caseinate in the form of dry powder manufactured in Poland from acid casein using the method of extrusion. The objective of the undertaken empirical studies was the assessment of the impact of the concentration on rheological properties of sodium caseinate concentrates. Investigations were carried out for five concentrates manufactured in a mixer equipped in a mechanical agitator at concentrations ranging X (% Î (2.5¸12.5 and changing mass proportions of sodium caseinate in the aqueous solution as follows: GS/G (kgS·kg-1 = 0.025. On the basis of the obtained research results, classical flow curves were plotted for individual concentrates. The determined values of viscosity and density of the examined solutions were correlated in the form of h = f(GS/G and r = f(GS/G dependencies which were used during the determination of classical characteristics of mixing forces essential for the assessment of energetic expenditures required to manufacture concentrates in a mixer equipped in a mechanical agitator. The density of the examined concentrates increased in a way directly proportional, while the dynamic viscosity coefficient increased exponentially together with the increase of sodium caseinate concentration. Sodium caseinate concentrates exhibited Newtonian character in the examined range of concentrations.

  16. Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions.

    Science.gov (United States)

    Jawor-Baczynska, Anna; Moore, Barry D; Lee, Han Seung; McCormick, Alon V; Sefcik, Jan

    2013-01-01

    Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells), usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets) were previously reported in supersaturated solutions of these amino acids and were implicated as intermediate species on non-classical crystallization pathways. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution. At a given temperature, solute molecules in such a mesostructured liquid phase are subject to equilibrium distribution between solute-rich mesospecies and the surrounding bulk solution.

  17. Relationship between solution structure and phase behavior: a neutron scattering study of concentrated aqueous hexamethylenetetramine solutions.

    Science.gov (United States)

    Burton, R C; Ferrari, E S; Davey, R J; Finney, J L; Bowron, D T

    2009-04-30

    The water-hexamethylenetetramine system displays features of significant interest in the context of phase equilibria in molecular materials. First, it is possible to crystallize two solid phases depending on temperature, both hexahydrate and anhydrous forms. Second, saturated aqueous solutions in equilibrium with these forms exhibit a negative dependence of solubility (retrograde) on temperature. In this contribution, neutron scattering experiments (with isotopic substitution) of concentrated aqueous hexamethylenetetramine solutions combined with empirical potential structure refinement (EPSR) were used to investigate the time-averaged atomistic details of this system. Through the derivation of radial distribution functions, quantitative details emerge of the solution coordination, its relationship to the nature of the solid phases, and of the underlying cause of the solubility behavior of this molecule.

  18. Adsorption of cesium on cement mortar from aqueous solutions.

    Science.gov (United States)

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

    2011-10-30

    The adsorption of cesium on cement mortar from aqueous solutions was studied in series of bench-scale tests. The effects of cesium concentration, temperature and contact time on process kinetics and equilibrium were evaluated. Experiments were carried out in a range of initial cesium concentrations from 0.0103 to 10.88 mg L(-1) and temperatures from 278 to 313 K using coupons of cement mortar immersed in the solutions. Non-radioactive cesium chloride was used as a surrogate of the radioactive (137)Cs. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectroscopy. Depending on the initial cesium concentration, its equilibrium concentration in solution ranged from 0.0069 to 8.837 mg L(-1) while the respective surface concentration on coupons varied from 0.0395 to 22.34 μg cm(-2). Equilibrium test results correlated well with the Freundlich isotherm model for the entire test duration. Test results revealed that an increase in temperature resulted in an increase in adsorption rate and a decrease in equilibrium cesium surface concentration. Among several kinetic models considered, the pseudo-second order reaction model was found to be the best to describe the kinetic test results in the studied range of concentrations. The adsorption activation energy determined from Arrhenius equation was found to be approximately 55.9 kJ mol(-1) suggesting that chemisorption was the prevalent mechanism of interaction between cesium ions and cement mortar.

  19. Electrical conductivity of aqueous solutions of aluminum salts

    Science.gov (United States)

    Vila, J.; Rilo, E.; Segade, L.; Cabeza, O.; Varela, L. M.

    2005-03-01

    We present experimental measurements of the specific electrical conductivity (σ) in aqueous solutions of aluminum salts at different temperatures, covering all salt concentrations from saturation to infinite dilution. The salts employed were AlCl3 , AlBr3 , AlI3 , and Al(NO3)3 , which present a 1:3 relationship between the electrical charges of anion and cation. In addition, we have measured the density in all ranges of concentrations of the four aqueous electrolyte solutions at 298.15K . The measured densities show an almost linear behavior with concentration, and we have fitted it to a second order polynomial with very high degree of approximation. The measurement of the specific conductivity at constant temperature reveals the existence of maxima in the conductivity vs concentration curves at molar concentrations around 1.5M for the three halide solutions studied, and at approximately 2M for the nitrate. We present a theoretical foundation for the existence of these maxima, based on the classical Debye-Hückel-Onsager hydrodynamic mean-field framework for electrical transport and its high concentration extensions, and also a brief consideration of ionic frictional coefficients using mode-coupling theory. We also found that the calculated values of the equivalent conductance vary in an approximately linear way with the square root of the concentration at concentrations as high as those where the maximum of σ appears. Finally, and for completeness, we have measured the temperature dependence of the electrical conductivity at selected concentrations from 283to353K , and performed a fit to an exponential equation of the Vogel-Fulcher-Tamman type. The values of the calculated temperatures of null mobility of the four salts are reported.

  20. Transformation and destabilization of graphene oxide in reducing aqueous solutions containing sulfide.

    Science.gov (United States)

    Fu, Heyun; Qu, Xiaolei; Chen, Wei; Zhu, Dongqiang

    2014-12-01

    The colloidal stability of carbon nanomaterials is a key factor controlling their fate and bioavailability in natural aquatic systems. The authors report that graphene oxide nanoparticles could be destabilized in reducing aqueous solutions containing a low concentration (0.5 mM) of sulfide, a naturally occurring reductant. Spectroscopic characterization using combined X-ray photoelectron, Fourier-transform infrared, X-ray diffraction, and Raman analyses revealed that the surface oxygen-containing groups (mainly epoxy groups) of graphene oxide were significantly reduced after reacting with sodium sulfide. The destabilization of graphene oxide was likely caused by the enhanced surface hydrophobicity of the reduced graphene oxide, whereas electrostatic repulsion played a minimal role. Solution pH was found to affect both the deoxygenation process and the aggregation behavior of graphene oxide. Coexisting humic acid reduced the reaction efficiency and stabilized graphene oxide through steric hindrance. These findings suggest for the first time that the colloidal behavior of carbon nanomaterials might change drastically when they enter natural reducing environments containing sulfide such as anaerobic aquifers and sediments.

  1. Persistence of two neonicotinoid insecticides in wastewater, and in aqueous solutions of surfactants and dissolved organic matter.

    Science.gov (United States)

    Peña, A; Rodríguez-Liébana, J A; Mingorance, M D

    2011-07-01

    Wastewater treatment plants receive organic contaminants, such as pesticides, which reach the sewage system from domestic, industrial or agricultural activities. In wastewater, which is a complex mixture of organic and inorganic compounds, biotic or abiotic degradation of contaminants can be affected by the presence of co-solutes. The photodecomposition in natural sunlight of two neonicotinoid insecticides, thiamethoxam and thiacloprid, was investigated in wastewater, aqueous extracts of sewage sludge and in aqueous surfactant solutions, which are abundant in wastewater. Dissipation in the dark was also studied in wastewater, due to reduction of transmitted sunlight in wastewater ponds. With regard to photolysis, thiamethoxam degraded rapidly in all the aqueous solutions. Among them sewage sludge extracts slightly modified (average half-life 17.6h), wastewater increased (13.7h) and non-ionic surfactants led, as a family, to the highest dissipation rates (average 6.2h), with respect to control water (18.7h). Additionally this pesticide also underwent a slower biodegradation process in wastewater in the dark under anaerobic conditions (around 25d). A metabolite of thiamethoxam from the biological decomposition in wastewater was identified by HPLC/MS. On the other hand thiacloprid was found to be resistant to photo- and biodecomposition and remained almost unchanged during the experimental periods in all the tested media.

  2. Arsenic Removal from Aqueous Solutions by Salvadora persica Stem Ash

    Directory of Open Access Journals (Sweden)

    Ferdos Kord Mostafapour

    2013-01-01

    Full Text Available Arsenic is a naturally occurring metalloid, which is widely distributed in nature and is regarded as the largest mass poisoning in history. In the present study, the adsorption potential of Salvadora persica (S. persica stem ash in a batch system for the removal of As(V from aqueous solutions was investigated. Isotherm studies were carried out to evaluate the effect of contact time (20–240 min, pH (2–11, initial arsenic concentration (50–500 μg/L, and adsorbent dose on sorption efficiency. Maximum removal efficiency of 98.33% and 99.32% was obtained at pH 6, adsorbent dosage 3.5 g/L, initial As(V concentration 500 μg/L, and contact time 80 and 60 min for S. persica stem ash at 300 °C and 500 °C, respectively. Also, the adsorption equilibriums were analyzed by the Langmuir and Freundlich isotherm models. Such equilibriums showed that the adsorption data was well fitted with the Freundlich isotherm model for S. persica stem ash at both 300 °C and 500 °C (R2=0.8983 and 0.9274, resp.. According to achieved results, it was defined that S. persica stem ash can be used effectively for As(V removal from the aqueous environment.

  3. Colloidal Stability of Graphene Oxide Nanosheets in Aqueous Solutions

    Science.gov (United States)

    Guikema, Janice; Wang, Yung-Li; Chen, Kai

    2013-03-01

    Carbon-based nanomaterials are increasingly used in commercial products as well as in research and industrial applications. Due to its extraordinary properties, graphene has attracted intense research interest and has been demonstrated in many potential applications including solar cells, conductive ink, and transistors. Graphene oxide has also been studied extensively and has been used to produce biocompatible antibacterial paper. Chemical reduction of graphene oxide is commonly used to produce inexpensive graphene in large quantities. With the increasing use of graphene and graphene oxide in consumer products, these nanomaterials may inevitably be released to aqueous systems, resulting in potential risk to environmental ecosystems and human health. The fate and mobility of graphene and its oxides in aquatic systems is dependent on their colloidal stability. We will discuss our study of the early-stage aggregation kinetics of graphene oxide in aqueous solutions. We prepared a suspension of single-layer graphene oxide nanosheets in water and used time-resolved dynamic light scattering to study the influence of electrolytes and pH on the aggregation kinetics of the nanosheets. Atomic force microscopy was employed to further examine the graphene oxide nanosheets.

  4. Comparison of Photochemical Reactions of m-Cresol in Aqueous Solution and in Ice

    Institute of Scientific and Technical Information of China (English)

    PENG Fei; XUE Hong-hai; TANG Xiao-jian; KANG Chun-li; LI Lin-lin; LI Zhe

    2012-01-01

    We compared the photochemical reaction of m-cresol containing OH precursors such as H2O2,NO2- and NO3- in aqueous solution with those in ice.The results show that the conversion rate of m-cresol in aqueous solution was higher than that in ice,H2O2,NO2- and NO3- all accelerated the photoconversion of m-cresol in both aqueous solution and ice.The photochemical reactions of m-cresol obeys the first order kinetics equation.According to the photoproducts identified by GC-MS,we proposed that hydroxylation and nitration reactions occurred in both aqueous solution and ice.Coupling reaction was common in ice,however,in aqueous solution it was found only in UV system.Our results suggest that the photochemical reactions of m-cresol were different in aqueous solution and in ice.

  5. Study of the nanobubble phase of aqueous NaCl solutions by dynamic light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Bunkin, N F; Shkirin, A V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Burkhanov, I S; Chaikov, L L [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Lomkova, A K [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

    2014-11-30

    Aqueous NaCl solutions with different concentrations have been investigated by dynamic scattering of laser radiation. It is experimentally shown that these solutions contain scattering particles with a wide size distribution in a range of ∼10 – 100 nm. The experimental results indirectly confirm the existence of quasi-stable gas nanobubbles in the bulk of aqueous ionic solutions. (light scattering)

  6. Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers

    Institute of Scientific and Technical Information of China (English)

    SUN Yue; LI Xiao-tao; XU Chao; CHEN Jin-long; LI Ai-min; ZHANG Quan-xing

    2005-01-01

    Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1,AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition,thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

  7. Adsorption of Anthraquinone Dyes from Aqueous Solutions by Penicillium Terrestre

    Institute of Scientific and Technical Information of China (English)

    XIN Bao-ping; LIU Xiao-mei

    2006-01-01

    Penicillium terrestre was used for removing four anthraquinone dyes from aqueous solution. The experiments were performed in Erlenmeyer flasks and spore suspension was used for inoculation. The results show that the mechanism of dye removal by penicillium terrestre is biosorption and the growing pellets exhibit higher adsorptive capacity than the resting or dead ones. The maximum removals of disperse blue 2BLN, reactive brilliant blue KN-R, acid anthraquinone blue and bromamine acid at the concentration of 120 mg/L by biosorption of growing pellets are 100 %, 100 %, 96 % and 91%, respectively. The 100.0 % and 91.4 % KN-R removals are achieved respectively at the much higher concentration of 250 and 400 mg/L. 2.5 g/L glucose is sufficient for 100% KN-R removal by growing pellets. Salinity (NaC1) increase from 0 to 2% (W/V) moderately accelerates both mycelium growth and KN-R removal.

  8. Degradation of aqueous solutions of camphor by heterogeneous photocatalysis.

    Science.gov (United States)

    Sirtori, Carla; Altvater, Priscila K; de Freitas, Adriane M; Peralta-Zamora, Patricio G

    2006-02-28

    In this study the photocatalytic degradation of aqueous solutions of camphor was investigated by using TiO2 and ZnO photocatalysts. In the presence of artificial UV-light the highly photosensitive camphor was almost totally degraded after reaction times of 60 min. However, under these conditions the mineralization degree was lower than 25%. In the presence of semiconductors the degradation was complete after a treatment time of about 30 min. Moreover, the mineralization was considerably greater, mainly with the use of TiO2 (> 80% at reaction time of 60 min). Heterogeneous photocatalytic processes applied in the presence of solar radiation show a promising degradation capability. TiO2-based processes afforded mineralization degrees of about 90% after a reaction time of 120 min, when the system was assisted by aeration.

  9. Microfluidic synthesis of monodisperse Cu nanoparticles in aqueous solution.

    Science.gov (United States)

    Ke, Te; Zeng, Xiao-Fei; Wang, Jie-Xin; Le, Yuan; Chu, Guang-Wen; Chen, Jian-Feng; Shao, Lei

    2011-06-01

    The continuous production of Cu nanoparticles with a particle size of 2-5 nm was conducted by sodium borohydride reduction of copper sulfate in aqueous solution in a tube-in-tube microchannel reactor (TMR), which consists of an inner tube and an outer tube with the reaction performed in the annular microchannel between these two tubes. The as-prepared Cu nanoparticles were compared with those obtained by a conventional batch synthesis process by using transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis spectroscopy. Due to the highly intensified micromixing effects in the TMR, Cu nanoparticles prepared by this route exhibits a smaller particle size, narrower size distribution and better stability in air. The TMR shows an excellent ability of preparing high-quality Cu nanoparticles in mild conditions. In addition, with the unique microchannel structure, the throughput capability of the TMR for the production of Cu nanoparticles is up to several liters per minute.

  10. Conformation of poly(γ-glutamic acid) in aqueous solution.

    Science.gov (United States)

    Muroga, Yoshio; Nakaya, Asami; Inoue, Atsuki; Itoh, Daiki; Abiru, Masaya; Wada, Kaori; Takada, Masako; Ikake, Hiroki; Shimizu, Shigeru

    2016-04-01

    Local conformation and overall conformation of poly(γ-DL-glutamic acid) (PγDLGA) and poly(γ-L-glutamic acid) (PγLGA) in aqueous solution was studied as a function of degree of ionization ε by (1) H-NMR, circular dichroism, and potentiometric titration. It was clarified that their local conformation is represented by random coil over an entire ε range and their overall conformation is represented by expanded random-coil in a range of ε > ε(*) , where ε(*) is about 0.3, 0.35, 0.45, and 0.5 for added-salt concentration of 0.02M, 0.05M, 0.1M, and 0.2M, respectively. In a range of ε acidic media.

  11. Application of ultrasound to textiles washing in aqueous solutions.

    Science.gov (United States)

    Gotoh, Keiko; Harayama, Kokoro

    2013-03-01

    The ultrasound was applied to textile washing as a mechanical action for soil removal. The polyester fabric was soiled with carbon black or oleic acid as a model contaminant, and washed with the original fabric in aqueous solutions without and with alkali or surfactant by applying ultrasound, shaking or stirring action. The detergency and soil redeposition were evaluated from the change in the surface reflectance of artificially soiled fabrics and the original fabric due to washing. In comparison with shaking and stirring actions, ultrasound was found to remove the particulate and oily soils efficiently in a short time and at low bath ratio. With increasing ultrasound power, the detergency of both soils increased and exceeded that obtained with Wascator, a horizontal axis drum type washer. Using three standard fabrics for determining mechanical action during washing, it was shown that ultrasound washing caused little mechanical damage to the fabric. However, the soil redeposition was frequently observed for ultrasonic washing, especially at low bath ratio.

  12. Aqueous dispersions of silver nanoparticles in polyelectrolyte solutions

    Indian Academy of Sciences (India)

    Dan Donescu; Raluca Somoghi; Marius Ghiurea; Raluca Ianchis; Cristian Petcu; Stefania Gavriliu; Magdalena Lungu; Claudia Groza; Carmen R Ionescu; Carmen Panzaru

    2013-03-01

    In this report, we present the versatile and effective technique, using environmental friendly reductant glucose, to prepare stable silver nanodispersions by reduction of Ag+ ions. Alternant copolymers of maleic anhydride with vinyl acetate and styrene sulphonate sodium acid salt polyelectrolytes were synthesized in aqueous solution and used as stabilizers. The formation of nano silver particles was confirmed by UV-Vis spectrophotometry and TEM measurements. Dynamic Light Scattering (DLS) measurements were needed to study how the reagents and their concentrations influence particle size. SEM images show the nanostructure of the hybrid films and indicate a strong interaction between the polyelectrolyte and the silver NPs. Moreover, the silver NPs could be stored for one year without observation of aggregates or sedimentation. The final solid products obtained after evaporating to dryness can be used to produce stable dispersions upon mixing with water. Few of the final products were found to exhibit a high antibacterial and antifungal activity.

  13. Transport Process of Isopropanol Aqueous Solution by Pervaporation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To study the transport process of isopropanol aqueous solution by pervaporation, the transport model of isopropanol and that of water at 323 K in polyvinyl alcohol(PVA) membrane were obtained in this paper. Theoretical predictions agreed well with the experimental results. The interactional parameter between water and PVA membrane is less than that between isopropanol and PVA membrane, which shows that water is preferentially dissolved in PVA membrane. The plasticizing coefficient and diffusion coefficient at infinite dilution of water are larger than those of isopropanol,which shows that the dissolution and permeation in PVA membrane of water are greater than those of isopropanol. Both the interactional parameter between water and isopropanol in the membrane and that in feed rise with the increase of isopropanol content in feed, which shows that the larger isopropanol content is, the higher selectivity of the membrane is and the more remarkable separation effect of pervaporation is.

  14. Adsorption of basic dye from aqueous solution onto fly ash

    Energy Technology Data Exchange (ETDEWEB)

    J.X. Lin; S.L. Zhan; M.H. Fang; X.Q. Qian; H. Yang [Zhejiang University, Hangzhou (China). College of Civil Engineering and Architecture

    2008-04-15

    The fly ash treated by H{sub 2}SO{sub 4} was used as a low-cost adsorbent for the removal of a typical dye, methylene blue, from aqueous solution. An increase in the specific surface area and dye-adsorption capacity was observed after the acid treatment. The adsorption isotherm and kinetics of the treated fly ash were studied. The experimental results were fitted using Langmuir and Freundlich isotherms. It shows that the Freundlich isotherm is better in describing the adsorption process. Two kinetic models, pseudo-first order and pseudo-second order, were employed to analyze the kinetic data. It was found that the pseudo-second-order model is the better choice to describe the adsorption behavior. The thermodynamic study reveals that the enthalpy ({Delta}H{sup 0}) value is positive (5.63 kJ/mol), suggesting an endothermic nature of the adsorption.

  15. Adsorption of CTAB onto perlite samples from aqueous solutions.

    Science.gov (United States)

    Alkan, Mahir; Karadaş, Mecit; Doğan, Mehmet; Demirbaş, Ozkan

    2005-11-15

    In this study, the adsorption properties of unexpanded and expanded perlite samples in aqueous cetyltrimethylammonium bromide (CTAB) solutions were investigated as a function of ionic strength, pH, and temperature. It was found that the amount of cetyltrimethylammonium bromide adsorbed onto unexpanded perlite was greater than that onto expanded perlite. For both perlite samples, the sorption capacity increased with increasing ionic strength and pH and decreasing temperature. Experimental data were analyzed by Langmuir and Freundlich isotherms and it was found that the experimental data were correlated reasonably well by the Freundlich adsorption isotherm. Furthermore, the isotherm parameters (KF and n) were also calculated. The adsorption enthalpy was determined from experimental data at different temperatures. Results have shown that the interaction between the perlite surface and CTAB is a physical interaction, and the adsorption process is an exothermic one.

  16. Infrared spectroscopy for monitoring gas hydrates in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Dobbs, G.T.; Luzinova, Y.; Mizaikoff, B. [Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry; Raichlin, Y.; Katzir, A. [Tel-Aviv Univ., Tel-Aviv (Israel). Shool of Physics and Astronomy

    2008-07-01

    This paper introduced the first principles for monitoring gas hydrate formation and dissociation in aqueous solution by evaluating state-responsive infrared (IR) absorption features of water with fiberoptic evanescent field spectroscopy. A first order linear functional relationship was also derived according to Lambert Beer's law in order to quantify the percentage gas hydrate within the volume of water probed via the evanescent field. In addition, spectroscopic studies evaluating seafloor sediments collected from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix components. As such, evanescent field sensing strategies were established as a promising perspective for monitoring the dynamics of gas hydrates in oceanic environments. 21 refs., 5 figs.

  17. Formation of wormlike micelles in anionic surfactant AES aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The growth and structure of anionic micelles of sodium dodecyl trioxyethylene sulfate (AES) in the presence 3+of multivalent counterion Al were investigated by means of dynamic rheological methods. It has been obtained by the measurements of shear viscosity, complex viscosity and dynamic moduli, as well as the application of Cox-Merz rule and Cole-Cole plot that wormlike micelle and network structure could be formed in AES/AlCl3 aqueous solutions.The structure was of a character of nonlinear viscoelastic fluid and departure from the simple Maxwell model. The technique of freeze-fracture transmission electron microscopy (FF-TEM) was also used to confirm the formation of this interesting structure.``

  18. Experimental study on thermophoresis of colloids in aqueous surfactant solutions

    Science.gov (United States)

    Dong, Ruo-Yu; Zhou, Yi; Yang, Chun; Cao, Bing-Yang

    2015-12-01

    Thermophoresis refers to the motion of particles under a temperature gradient and it is one of the particle manipulation techniques. Regarding the thermophoresis of particles in liquid media, however, many open questions still remain, especially the role of the interfacial effect. This work reports on a systematic experimental investigation of surfactant effects, especially the induced interfacial effect, on the thermophoresis of colloids in aqueous solutions via a microfluidic approach. Two kinds of commonly used surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), are selected and the results show that from relatively large concentrations, the two surfactants can greatly enhance the thermophilic mobilities. Specifically, it is found that the colloid-water interfaces modified with more polar end groups can potentially lead to a stronger thermophilic tendency. Due to the complex effects of surfactants, further theoretical model development is needed to quantitatively describe the dependence of thermophoresis on the interface characteristics.

  19. γ-Irradiation of malic acid in aqueous solutions

    Science.gov (United States)

    Negron-Mendoza, Alicia; Graff, Rebecca L.; Ponnamperuma, Cyril

    1980-12-01

    The γ-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the non-volatile products. Thin layer chromotography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the γ-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  20. Removal of lead from aqueous solutions by Penicillium biomass

    Energy Technology Data Exchange (ETDEWEB)

    Hui Niu; Xue Shu Xu; Jian Hua Wang (Chengdu Univ. of Science and Technology, Sichuan (China). Dept. of Chemical Engineering); Volesky, B. (McGill Univ., Montreal (Canada). Dept. of Chemical Engineering)

    1993-09-05

    The removal of lead ions from aqueous solutions by adsorption on nonliving Penicillium chrysogenum biomass was studied. Biosorption of the Pb[sup +2] ion was strongly affected by pH. Within a pH range of 4 to 5, the saturated sorption uptake of Pb[sup +2] was 116 mg/g dry biomass, higher than that of activated charcoal and some other microorganisms. At pH 4.5, P. chrysogenum biomass exhibited selectivity for Pb[sup +2] over other metal ions such as Cd[sup +2], Cu[sup +2], Zn [sup +2], and As[sub +3]. Sorption preference for metals decreased in the following order: Pb > Cd > Cu > Zn > As. The sorption uptake of Pb[sup +2] remained unchanged in the presence of Cu[sup +2] and As [sup +3], it decreased in the presence of Zn[sup +2], and increased in the presence of Cd[sup +2].

  1. VISCOSITY BEHAVIOR OF LACQUER POLYSACCHARIDE IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    QIU Xingping; ZHANG Lina; DU Yumin; QIAN Baogong

    1991-01-01

    The dependence of measured viscosity on NaCl concentration (0.1 to 3.0M), pH (range of 2-13) and cadoxen composition Wcad (from 2% to 100% ) for the lacquer polysaccharide in NaCl/cadoxen/H2O mixture containing HCl or without were obtained. All the viscosity exponents γ in the Mark-Houwink equations under three different solvent condition are close to 0.5. The wcad dependence of reduced viscosity ηsp/c confirms the single strand chain of the polysaccharide. As the γ values close to 0.5 and values of unperturbed dimension θ/M and [η] much smaller than those for usual linear polymers, these facts suggest that the polysaccharide chains in the aqueous solutions should be dense random coil owing to the highly branched structure.

  2. Ultrasonic Measurements of Temperature in Aqueous Solutions: Why and How

    Directory of Open Access Journals (Sweden)

    A. Afaneh

    2011-01-01

    Full Text Available The paper describes two different approaches to ultrasonic measurements of temperature in aqueous solutions. The first approach uses two narrowband ultrasonic transducers and support electronics that form an oscillating sensor which output frequency is related to the measured temperature. This low-cost sensor demonstrated sensitivity of about 40 Hz/K at the distance of 190 mm and the operating frequency of about 25 kHz. The second approach utilised pulse-echo mode at the centre frequency of 20 MHz. The reflector featured a cavity that was filled with deionised water. The ultrasound propagation delay in the cavity was related to the temperature in the solution. The experiments were conducted for deionised water, and solutions of sodium persulfate, sodium chloride, and acetic acid with concentrations up to 0.5 M. In the experiments (conducted within the temperature range from 15 to 30°C, we observed increases in the ultrasound velocity for increased temperatures and concentrations as was expected. Measurement results were compared with literature data for pure and seawater. It was concluded that ultrasonic measurements of temperature were conducted with the resolution well below 0.1 K for both methods. Advantages of ultrasonic temperature measurements over conventional thermometers were discussed.

  3. Aqueous solution of basic fuchsin as food irradiation dosimeter

    Institute of Scientific and Technical Information of China (English)

    Hasan M. KHAN; Shagufta NAZ

    2007-01-01

    Dosimetric characterization of aqueous solution of basic fuchsin was studied spectrophotometrically for possible application in the low-dose food irradiation dosimetry. Absorption spectra of unirradiated and irradiated solutions were determined and the decrease in absorbance with the dose was noted down. Radiation-induced bleaching of the dye was measured at wavelengths of maximum absorption λmax (540nm) as well as 510nm and 460 nm. At all these wavelengths, the decrease in absorbance of the dosimeter was linear with respect to the absorbed dose from 50 Gy to 600 Gy. The stability of dosimetric solution during post-irradiation storage in the dark at room temperature showed that after initial bleaching during first ten to twenty days, the response was almost stable for about 34 days. The study on the effect of different light and temperature conditions also showed that the response gradually decreased during the storage period of 34 days, which shows that basic fuchsin dye is photosensitive as well as thermally sensitive.

  4. Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles

    Science.gov (United States)

    Zemánková, Katerina; Troncoso, Jacobo; Cerdeiriña, Claudio A.; Romaní, Luis; Anisimov, Mikhail A.

    2016-06-01

    The anomalous behavior of aqueous solutions of amphiphiles in the water-rich region is analyzed via a phenomenological approach that utilizes the isobaric heat capacity Cp as an experimental probe. We report extensive data for solutions of 14 amphiphiles as a function of temperature at atmospheric pressure. Beyond that, Cp data but also isobaric thermal expansivities and isothermal compressibilities for three solutions of tert-butanol as a function of both temperature and pressure are presented. Results rule out the possibility that the observed phenomenology is associated with the anomalous thermodynamics of pure water. Indeed, our Cp data, quantitatively consistent with recent spectroscopic analyses, suggest that water-mediated interactions between the nonpolar parts of amphiphiles are at the origin of anomalies, with the effects of such "hydrophobic aggregation" being observed at mole fractions as small as 0.01. Physicochemical details like the size, the electronic charge distribution and the geometry of amphiphile molecules as well as third-order derivatives of the Gibbs energy and the associated Koga lines support the above claims while they further contribute to characterizing the role of hydrophobicity in these phenomena. Progress with a view to gain a deeper, more concrete understanding remains.

  5. Carbon dioxide capture capacity of sodium hydroxide aqueous solution.

    Science.gov (United States)

    Yoo, Miran; Han, Sang-Jun; Wee, Jung-Ho

    2013-01-15

    The present paper investigates the various features of NaOH aqueous solution when applied as an absorbent to capture carbon dioxide (CO(2)) emitted with relatively high concentration in the flue gas. The overall CO(2) absorption reaction was carried out according to consecutive reaction steps that are generated in the order of Na(2)CO(3) and NaHCO(3). The reaction rate and capture efficiency were strongly dependent on the NaOH concentration in the Na(2)CO(3) production range, but were constant in the NaHCO(3) production step, irrespective of the NaOH concentration. The amount of CO(2) absorbed in the solution was slightly less than the theoretical value, which was ascribed to the low trona production during the reaction and the consequent decrease in CO(2) absorption in the NaOH solution. The mass ratio of absorbed CO(2) that participated in the Na(2)CO(3), NaHCO(3), and trona production reactions was calculated to be 20:17:1, respectively.

  6. Mechanism of chitosan adsorption on silica from aqueous solutions.

    Science.gov (United States)

    Tiraferri, Alberto; Maroni, Plinio; Rodríguez, Diana Caro; Borkovec, Michal

    2014-05-06

    We present a study of the adsorption of chitosan on silica. The adsorption behavior and the resulting layer properties are investigated by combining optical reflectometry and the quartz crystal microbalance. Exactly the same surfaces are used to measure the amount of adsorbed chitosan with both techniques, allowing the systematic combination of the respective experimental results. This experimental protocol makes it possible to accurately determine the thickness of the layers and their water content for chitosan adsorbed on silica from aqueous solutions of varying composition. In particular, we study the effect of pH in 10 mM NaCl, and we focus on the influence of electrolyte type and concentration for two representative pH conditions. Adsorbed layers are stable, and their properties are directly dependent on the behavior of chitosan in solution. In mildly acidic solutions, chitosan behaves like a weakly charged polyelectrolyte, whereby electrostatic attraction is the main driving force for adsorption. Under these conditions, chitosan forms rigid and thin adsorption monolayers with an average thickness of approximately 0.5 nm and a water content of roughly 60%. In neutral solutions, on the other hand, chitosan forms large aggregates, and thus adsorption layers are significantly thicker (∼10 nm) as well as dissipative, resulting in a large maximum of adsorbed mass around the pK of chitosan. These films are also characterized by a substantial amount of water, up to 95% of their total mass. Our results imply the possibility to produce adsorption layers with tailored properties simply by adjusting the solution chemistry during adsorption.

  7. Biosorption of arsenic from aqueous solution using dye waste.

    Science.gov (United States)

    Nigam, Shubha; Vankar, Padma S; Gopal, Krishna

    2013-02-01

    The purpose of this study is to examine on removal of arsenic from water by biosorption through potential application of herbal dye wastes. Four different flower dye residues (after extraction of natural dye) viz. Hibiscus rosasinensis, Rosa rosa, Tagetes erecta, and Canna indica were utilized successfully for the removal of arsenic from aqueous solution. Batch studies were carried out for various parameters viz. pH, sorbent dose, contact time, initial metal ion concentration, and temperature. Data were utilized for isothermal, kinetic, and thermodynamic studies. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDAX), and Fourier transform infrared (FTIR) analyses of biomass were performed. The results showed that 1 g/100 ml for 5.0-5.5 h contact time at pH 6.0-7.5 with agitation rate 150 rpm provided 98, 96, 92, and 85 % maximum absorption of arsenic by R. rosa, H. rosasinensis, T. erecta, and C. indica, respectively, at initial concentration of 500 ppb. Data followed Langmuir isotherm showing sorption to be monolayer on heterogeneous surface of biosorbent. Negative values of ΔG° indicated spontaneous nature, whereas ΔH° indicates exothermic nature of system followed by pseudo-first-order adsorption kinetics. FTIR results showed apparent changes in functional group regions after metal chelation. SEM and EDAX analyses showed the changes in surface morphology of all test biosorbents. Herbal dye wastes, used as biosorbent, exhibited significant (85-98 %) removal of arsenic from aqueous solution. Hence, these biosorbents are cost-effective, easily available, eco-friendly, and comparatively more effective than other biosorbents already in use. These may be used to remove arsenic and other toxic metals from water.

  8. Humic acid removal from aqueous solutions by peroxielectrocoagulation process

    Directory of Open Access Journals (Sweden)

    Ahmad Reza Yazdanbakhsh

    2015-06-01

    Full Text Available Background: Natural organic matter is the cause of many problems associated with water treatment such as the presence of disinfection by-products (DBPs and membrane fouling during water filtration. In this study, the performance of the peroxi-electrocoagulation process (PEP was investigated for the removal of humic acids (HAs from aqueous solutions. Methods: PEP was carried out for the removal of HA using a plexiglas reactor with a volume of 2 L and fitted with iron electrodes and a direct current supply (DC. Samples were taken at various amounts of pH (2-4, current density (1 and 2A/cm2, hydrogen peroxide (50-150 mg/L and reaction time (5-20 minutes and then filtered to remove sludge formed during reaction. Finally, the HA concentration was measured by UV absorbance at 254 nm (UV254. Results: Results indicated that increasing the concentration of H2O2 from 50 to 150 mg/L increased HA removal efficiency from 83% to 94.5%. The highest removal efficiency was observed at pH 3.0; by increasing the pH to the alkaline range, the efficiency of the process was reduced. It was found that HA removal efficiency was high in current density 1A/cm2. Increasing current density up to 1 A cm-2 caused a decrease in removal efficiency. Results of this study showed that under the optimum operating range for the process ([current density] = 1A/cm2, [hydrogen peroxide concentration] = 150 mg/L, [reaction time]= 20 minutes and [pH]= 3.0, HA removal efficiency reached 98%. Conclusion: It can be concluded that PEP has the potential to be utilized for cost-effective removal of HA from aqueous solutions.

  9. Removal of zirconium from aqueous solution by modified clinoptilolite

    Energy Technology Data Exchange (ETDEWEB)

    Faghihian, H., E-mail: h.faghih@sci.ui.ac.ir [Department of Chemistry, University of Isfahan, 81746-73441, Isfahan (Iran, Islamic Republic of); Kabiri-Tadi, M. [Department of Chemistry, University of Isfahan, 81746-73441, Isfahan (Iran, Islamic Republic of)

    2010-06-15

    Adsorptive behavior of natural clinoptilolite was assessed for the removal of zirconium from aqueous solutions. Natural zeolite was characterized by X-ray diffraction, X-ray fluorescence, thermal methods of analysis and FTIR. The zeolite sample composed mainly of clinoptilolite and presented a cation exchange capacity of 1.46 meq g{sup -1}. K, Na and Ca-exchanged forms of zeolite were prepared and their sorption capacities for removal of zirconium from aqueous solutions were determined. The effects of relevant parameters, including initial concentration, contact time, temperature and initial pH on the removal efficiency were investigated in batch studies. The pH strongly influenced zirconium adsorption capacity and maximal capacity was obtained at pH 1.0. The maximum removal efficiency obtained at 40 deg. C and equilibration time of 24 h on the Ca-exchanged form. Kinetics and isotherm of adsorption were also studied. The pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were used to describe the kinetic data. The pseudo-second-order kinetic model provided excellent kinetic data fitting (R{sup 2} > 0.998) with rate constant of 1.60 x 10{sup -1}, 1.96 x 10{sup -1}, 2.45 x 10{sup -1} and 2.02 x 10{sup -1} g mmol{sup -1} min{sup -1} respectively for Na, K, Ca-exchanged forms and natural clinoptilolite. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for zirconium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters were determined and are discussed.

  10. Cations bind only weakly to amides in aqueous solutions.

    Science.gov (United States)

    Okur, Halil I; Kherb, Jaibir; Cremer, Paul S

    2013-04-01

    We investigated salt interactions with butyramide as a simple mimic of cation interactions with protein backbones. The experiments were performed in aqueous metal chloride solutions using two spectroscopic techniques. In the first, which provided information about contact pair formation, the response of the amide I band to the nature and concentration of salt was monitored in bulk aqueous solutions via attenuated total reflection Fourier transform infrared spectroscopy. It was found that molar concentrations of well-hydrated metal cations (Ca(2+), Mg(2+), Li(+)) led to the rise of a peak assigned to metal cation-bound amides (1645 cm(-1)) and a decrease in the peak associated with purely water-bound amides (1620 cm(-1)). In a complementary set of experiments, the effect of cation identity and concentration was investigated at the air/butyramide/water interface via vibrational sum frequency spectroscopy. In these studies, metal ion-amide binding led to the ordering of the adjacent water layer. Such experiments were sensitive to the interfacial partitioning of cations in either a contact pair with the amide or as a solvent separated pair. In both experiments, the ordering of the interactions of the cations was: Ca(2+) > Mg(2+) > Li(+) > Na(+) ≈ K(+). This is a direct cationic Hofmeister series. Even for Ca(2+), however, the apparent equilibrium dissociation constant of the cation with the amide carbonyl oxygen was no tighter than ∼8.5 M. For Na(+) and K(+), no evidence was found for any binding. As such, the interactions of metal cations with amides are far weaker than the analogous binding of weakly hydrated anions.

  11. Selection of suitable fertilizer draw solute for a novel fertilizer-drawn forward osmosis-anaerobic membrane bioreactor hybrid system

    KAUST Repository

    Kim, Youngjin

    2016-02-09

    In this study, a protocol for selecting suitable fertilizer draw solute for anaerobic fertilizer-drawn forward osmosis membrane bioreactor (AnFDFOMBR) was proposed. Among eleven commercial fertilizer candidates, six fertilizers were screened further for their FO performance tests and evaluated in terms of water flux and reverse salt flux. Using selected fertilizers, bio-methane potential experiments were conducted to examine the effect of fertilizers on anaerobic activity due to reverse diffusion. Mono-ammonium phosphate (MAP) showed the highest biogas production while other fertilizers exhibited an inhibition effect on anaerobic activity with solute accumulation. Salt accumulation in the bioreactor was also simulated using mass balance simulation models. Results showed that ammonium sulphate and MAP were the most appropriate for AnFDFOMBR since they demonstrated less salt accumulation, relatively higher water flux, and higher dilution capacity of draw solution. Given toxicity of sulphate to anaerobic microorganisms, MAP appears to be the most suitable draw solution for AnFDFOMBR.

  12. Selection of suitable fertilizer draw solute for a novel fertilizer-drawn forward osmosis-anaerobic membrane bioreactor hybrid system.

    Science.gov (United States)

    Kim, Youngjin; Chekli, Laura; Shim, Wang-Geun; Phuntsho, Sherub; Li, Sheng; Ghaffour, Noreddine; Leiknes, TorOve; Shon, Ho Kyong

    2016-06-01

    In this study, a protocol for selecting suitable fertilizer draw solute for anaerobic fertilizer-drawn forward osmosis membrane bioreactor (AnFDFOMBR) was proposed. Among eleven commercial fertilizer candidates, six fertilizers were screened further for their FO performance tests and evaluated in terms of water flux and reverse salt flux. Using selected fertilizers, bio-methane potential experiments were conducted to examine the effect of fertilizers on anaerobic activity due to reverse diffusion. Mono-ammonium phosphate (MAP) showed the highest biogas production while other fertilizers exhibited an inhibition effect on anaerobic activity with solute accumulation. Salt accumulation in the bioreactor was also simulated using mass balance simulation models. Results showed that ammonium sulfate and MAP were the most appropriate for AnFDFOMBR since they demonstrated less salt accumulation, relatively higher water flux, and higher dilution capacity of draw solution. Given toxicity of sulfate to anaerobic microorganisms, MAP appears to be the most suitable draw solution for AnFDFOMBR.

  13. Adsorption of cesium on cement mortar from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-30

    Highlights: {yields} The adsorption of cesium on cement mortar was investigated in a range of temperatures and cesium concentrations. {yields} The pseudo-second order kinetic model produced a good fit with the experimental kinetic data. {yields} Equilibrium test results correlated well with the Freundlich isotherm adsorption model. {yields} The interaction between cesium ions and cement mortar was dominated by chemical adsorption. - Abstract: The adsorption of cesium on cement mortar from aqueous solutions was studied in series of bench-scale tests. The effects of cesium concentration, temperature and contact time on process kinetics and equilibrium were evaluated. Experiments were carried out in a range of initial cesium concentrations from 0.0103 to 10.88 mg L{sup -1} and temperatures from 278 to 313 K using coupons of cement mortar immersed in the solutions. Non-radioactive cesium chloride was used as a surrogate of the radioactive {sup 137}Cs. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectroscopy. Depending on the initial cesium concentration, its equilibrium concentration in solution ranged from 0.0069 to 8.837 mg L{sup -1} while the respective surface concentration on coupons varied from 0.0395 to 22.34 {mu}g cm{sup -2}. Equilibrium test results correlated well with the Freundlich isotherm model for the entire test duration. Test results revealed that an increase in temperature resulted in an increase in adsorption rate and a decrease in equilibrium cesium surface concentration. Among several kinetic models considered, the pseudo-second order reaction model was found to be the best to describe the kinetic test results in the studied range of concentrations. The adsorption activation energy determined from Arrhenius equation was found to be approximately 55.9 kJ mol{sup -1} suggesting that chemisorption was the prevalent mechanism of interaction between cesium ions and cement mortar.

  14. Lead removal from aqueous solutions by a Tunisian smectitic clay.

    Science.gov (United States)

    Chaari, Islem; Fakhfakh, Emna; Chakroun, Salima; Bouzid, Jalel; Boujelben, Nesrine; Feki, Mongi; Rocha, Fernando; Jamoussi, Fakher

    2008-08-15

    The adsorption of Pb(2+) ions onto Tunisian smectite-rich clay in aqueous solution was studied in a batch system. Four samples of clay (AYD, AYDh, AYDs, AYDc) were used. The raw AYD clay was sampled in the Coniacian-Early Campanian of Jebel Aïdoudi in El Hamma area (South of Tunisia). AYDh and AYDs corresponds to AYD activated by 2.5 mol/l hydrochloric acid and 2.5 mol/l sulphuric acid, respectively. AYDc corresponds to AYD calcined at different temperatures (100, 200, 300, 400, 500 and 600 degrees C). The raw AYD clay was characterized by X-ray diffraction, chemical analysis, infrared spectroscopy and coupled DTA-TGA. Specific surface area of all the clay samples was determined from nitrogen adsorption isotherms. Preliminary adsorption tests showed that sulphuric acid and hydrochloric acid activation of raw AYD clay enhanced its adsorption capacity for Pb(2+) ions. However, the uptake of Pb(2+) by AYDs was very high compared to that by AYDh. This fact was attributed to the greater solubility of clay minerals in sulphuric acid compared to hydrochloric acid. Thermic activation of AYD clay reduced the Pb(2+) uptake as soon as calcination temperature reaches 200 degrees C. All these preliminary results were well correlated to the variation of the specific surface area of the clay samples. The ability of AYDs sample to remove Pb(2+) from aqueous solutions has been studied at different operating conditions: contact time, adsorbent amount, metal ion concentration and pH. Kinetic experiments showed that the sorption of lead ions on AYDs was very fast and the equilibrium was practically reached after only 20 min. The results revealed also that the adsorption of lead increases with an increase in the solution pH from 1 to 4.5 and then decreases, slightly between pH 4.5 and 6, and rapidly at pH 6.5 due to the precipitation of some Pb(2+) ions. The equilibrium data were analysed using Langmuir isotherm model. The maximum adsorption capacity (Q(0)) increased from 25 to 25

  15. Gamma Radiolysis Studies of Aqueous Solution of Brilliant Green Dye

    Directory of Open Access Journals (Sweden)

    D. V. Parwate

    2011-01-01

    Full Text Available The effect of γ–radiation on colour intensity of aqueous solution of Brilliant Green has been investigated at two different concentrations. The degradation of Brilliant Green (BG has also been investigated in presence of suspended ZnO, by adding different amounts of ZnO. Simultaneously the conductance and pH of each solution system were measured before and after γ-irradiation. All the γ–irradiations were performed at a dose rate of 0.60 kGyhr-1 in GC-900. The maximum dose required for the complete degradation of the dye was found to be 0.39 kGy. G(-dye values were found to decrease with increase in gamma dose and were in the range 4.26 - 12.81. The conductance (7.6 - 25.3 μS and pH values increased marginally with dose for both the concentrations. The rate of decolouration was found to be high at lower doses and the efficiency of dye removal was higher at low concentration of the dye. This may be attributed to the presence of reaction by-products from the destruction of parent compound build up and compete for reaction intermediate species. The rate of reaction and rate constants were calculated and it was found that the degradation reaction follows first order kinetics. It was found that the decolouration percentage was more in dye systems in absence of ZnO.

  16. Removal of Nitrate From Aqueous Solution Using Rice Chaff

    Directory of Open Access Journals (Sweden)

    Dehghani

    2015-09-01

    Full Text Available Background Nitrate is largely dissolved in the surface and ground water, due to its high solubility. Continual uptake of nitrite through drinking water can lead to problems and diseases (such as blue baby for humans, especially children. Objectives The aim of this study was to develop a new and inexpensive method for the removal of nitrate from water. In this regard, the possibility of using chaff for removal of nitrate from aqueous solutions was studied and the optimum operating conditions of nitrate removal was determined. Materials and Methods This is a cross-sectional study conducted in laboratory scale. The UV spectrophotometer at a wavelength of maximum absorbance (220 nm was used to determine the nitrate concentration. The effect of pH, amount of chaff, temperature, and contact time were investigated. Results The result of this study revealed that chaff as an absorbent could remove nitrate from solutions, and the efficiency of adsorption increased as contact time increased from 5 to 30 minutes, amount of chaff increased from 1 to 3 g, temperature increased in a range of 300 - 400°C and the amount of pH decreased from 10 to 3. The maximum adsorption rate was around pH 3 (53.14%. Conclusions It was shown that the removal efficiency of nitrate was directly proportional to the amount of chaff, temperature, and contact time but inversely to the pH. This study showed that nitrate removal by chaff is a promising technique.

  17. Structure and phase behavior of aqueous methylcellulose solutions

    Science.gov (United States)

    McAllister, John; Schmidt, Peter; Lodge, Timothy; Bates, Frank

    2015-03-01

    Cellulose ethers (CE) constitute a multi-billion dollar industry, and have found end uses in a broad array of applications from construction materials, food products, personal care products, and pharmaceuticals for more than 80 years. Methylcellulose (MC, with the trade name METHOCEL™) is a CE in which there is a partial substitution of -OH groups with -OCH3 groups. This results in a polymer that is water-soluble at low temperatures, and aqueous solutions of MC display gelation and phase separation at higher temperatures. The nature of MC gelation has been debated for many years, and this project has made significant advances in the understanding of the solution properties of CEs. We have characterized a fibrillar structure of MC gels by cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS). Using light scattering, turbidity measurements, and dynamic mechanical spectroscopy (DMS) we report that MC microphase separates by nucleation and growth of fibril aggregates, and is a different process from LCST phase separation.

  18. Single Molecule Electrochemical Detection in Aqueous Solutions and Ionic Liquids.

    Science.gov (United States)

    Byers, Joshua C; Paulose Nadappuram, Binoy; Perry, David; McKelvey, Kim; Colburn, Alex W; Unwin, Patrick R

    2015-10-20

    Single molecule electrochemical detection (SMED) is an extremely challenging aspect of electroanalytical chemistry, requiring unconventional electrochemical cells and measurements. Here, SMED is reported using a "quad-probe" (four-channel probe) pipet cell, fabricated by depositing carbon pyrolytically into two diagonally opposite barrels of a laser-pulled quartz quadruple-barreled pipet and filling the open channels with electrolyte solution, and quasi-reference counter electrodes. A meniscus forms at the end of the probe covering the two working electrodes and is brought into contact with a substrate working electrode surface. In this way, a nanogap cell is produced whereby the two carbon electrodes in the pipet can be used to promote redox cycling of an individual molecule with the substrate. Anticorrelated currents generated at the substrate and tip electrodes, at particular distances (typically tens of nanometers), are consistent with the detection of single molecules. The low background noise realized in this droplet format opens up new opportunities in single molecule electrochemistry, including the use of ionic liquids, as well as aqueous solution, and the quantitative assessment and analysis of factors influencing redox cycling currents, due to a precisely known gap size.

  19. Drop-on-demand for aqueous solutions of sodium alginate

    Science.gov (United States)

    Herran, C. Leigh; Coutris, Nicole

    2013-06-01

    Inkjet printing is a rapidly growing commercial process for applications that depend on precisely patterning micro-scale droplets. These applications increasingly require complex fluids, introducing viscoelastic properties which play an important role in droplet formation. The objective of this study is to determine how to obtain single, uniform and spherical ("successful") droplets from aqueous solutions of sodium alginate with a piezoelectric drop-on-demand printing method. In order to control the volume and velocities of droplets, the effect on the droplet formation of the characteristics of the waveform such as voltage amplitude and dwell time is studied. The results depend also on the fluid rheology. The viscosity of the chosen fluid is a function of the concentration, as the viscoelastic properties increase at higher concentration. In this paper, the droplet formation process is characterized in terms of both the waveform and the rheological properties of the solution. The characterization of the fluids and waveform will be pursued first and the droplet formation and its control will be studied. Finally, the results will be presented with a map in ranges of the Ohnesorge, Deborah and Weber numbers.

  20. Columnar molecular aggregation in the aqueous solutions of disodium cromoglycate

    Science.gov (United States)

    Agra-Kooijman, Dena M.; Singh, Gautam; Lorenz, Alexander; Collings, Peter J.; Kitzerow, Heinz-S.; Kumar, Satyendra

    2014-06-01

    Stack, chimneylike, and threadlike assemblies have previously been proposed for the structure of disodium cromoglycate (DSCG) aggregates in aqueous solutions. The results of the synchrotron x-ray scattering investigations reported here reveal the formation of simple columnar assemblies with π-π stacking at a separation of 3.4 Å between the DSCG molecules. Lateral separation between the assemblies is concentration and temperature dependent, varying from ˜35 to 42 Å in the orientationally ordered nematic (N) phase and from 27 to 32 Å in the columnar or middle (M) phase having long range lateral positional order. The assemblies' length depends on concentration and consists of ˜23 molecules in the N phase, becoming three to ten times larger in the M phase. The scission energy is concentration dependent in the N phase with values ˜7.19 ± 0.14 kBT (15 wt %), 2.73 ± 0.4 kBT (20 wt %), and 3.05 ± 0.2 kBT (25 wt %). Solutions of all concentrations undergo a spinodal decomposition at temperatures above ˜40 °C, resulting in DSCG-rich regions with the M phase and water-rich regions in the N and isotropic phases.

  1. Corrosion of metastable iron alloys in aqueous solutions

    Science.gov (United States)

    Wolf, Gerhard K.; Ferber, H.

    1983-05-01

    There exist some examples showing that metastable surface alloys can modify the corrision properties of a substrate in the same way as stable alloys do. In the present paper the corrosion behaviour of metastable surface alloys obtained by implanting gold, lead and mercury in iron was studied in aqueous solution of pH = 5.6. Potentiodynamic current density-potential curves were recorded of the implanted samples without further treatment and after isothermal annealing to temperatures up to 800°C. The results were compared with structural information on the alloys obtained by Turos et al. with α-backscattering and channeling experiments. Gold implantation turned out to enhance the active corrosion rate of iron, while lead and mercury had an impeding effect. The annealing experiments showed that the surface alloying facilitated the passivation of iron as long as the substitutional solid solution was "(meta)stable". After the breakdown at higher annealing temperatures leading to surface migration and clustering of the implanted elements a significant increase of the critical current density for passivation took place. This indicates passivation difficulties caused by the heterogeneous distribution of the "alloying" particles. In general the results suggest that substitutional metastable iron alloys cause in a systematic way corrosion inhibition or enhancement. However, their corrosion properties may change completely for non-substitutional distribution of the alloying elements as originating from annealing at higher temperatures.

  2. Cast iron deterioration with time in various aqueous salt solutions

    Indian Academy of Sciences (India)

    Rita Mehra; Aditi Soni

    2002-02-01

    The changes with time in the corrosion rate and corrosion current density on a cast iron electrode in various aqueous salt solutions have been carried out using total immersion test and potentiostatic polarization curves. The concentration of salts taken is expected to be present in potable water. The relative behaviour of these salts towards corrosion has also been studied, which is found to be different from previous studies. The total immersion test parameters viz. weight loss, corrosion rate as well as potentiostatic parameters, open circuit potential, corr, Tafel slopes, corrosion rate, have been calculated by standard methods. Besides these the relative increase in corrosion rate with time as well as the percentage to which corrosion rate should be decreased so as to provide protection towards corrosion have also been calculated. It was found that KCl and NaCl are major contributors than MnSO4, Pb(NO3)2, KI and KBr. The relative increase in corrosion is high in KBr, KI, NaNO3, CaCl2, and less in Pb(NO3)2, NaHCO3 and CaCO3 test solutions. For the reliability of results the data has been statistically analysed.

  3. Enrichment of surfactant from its aqueous solution using ultrasonic atomization.

    Science.gov (United States)

    Takaya, Haruko; Nii, Susumu; Kawaizumi, Fumio; Takahashi, Katsuroku

    2005-08-01

    Dilute aqueous solutions of dodecyl-benzenesulfonic acid sodium salt (DBS-Na) and polyoxyethylenenonylphenyl ethers (PONPEs) were ultrasonically atomized. The surfactants were concentrated in collected mist droplets. The enrichment ratio increased with decreasing surfactant concentration. Depending on the surfactant's molecular weight and affinity to water, different enrichment ratio was observed in the range of low feed concentrations. For anionic surfactant, DBS-Na, the enrichment ratio was significantly improved by KCl addition and a peak appeared on the plot of the ratio against KCl concentration. Addition of NaCl or CaCl2 . 2H2O to the surfactant solution also enhanced the enrichment ratio; however, the effect was relatively small. Such behaviors of the ratio were interpreted as enhanced interfacial adsorption of the surfactant and a lack of supply of surfactant monomers from liquid bulk because of slow breaking of surfactant micelles. Time required for collecting an amount of mist was also observed. Among the three salt systems, the time for KCl system was twice as long as others. This fact suggested that the formation of smaller droplets in KCl system.

  4. Metal ion removal from aqueous solution using physic seed hull.

    Science.gov (United States)

    Mohammad, Masita; Maitra, Saikat; Ahmad, Naveed; Bustam, Azmi; Sen, T K; Dutta, Binay K

    2010-07-15

    The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for the removal of Cd(2+) and Zn(2+) metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd(2+) and Zn(2+) increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages-a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms-Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn(2+) and Cd(2+) was found to be comparable with other available adsorbents. About 36-47% of the adsorbed metal could be leached out of the loaded PSH using 0.1M HCl as the eluting medium.

  5. Adsorption of itaconic acid from aqueous solutions onto alumina

    Directory of Open Access Journals (Sweden)

    JELENA J. GULICOVSKI

    2008-08-01

    Full Text Available Itaconic acid, IA (C5H6O4, was investigated as a potential flocculant for the aqueous processing of alumina powders. The adsorption of IA, as a function of its concentration and pH value of the solution, onto the alumina surface was studied by the solution depletion method. The stability of the suspensions in the presence of itaconic acid was evaluated in light of the surface charge of the alumina powder used, the degree of dissociation of IA, as well as the sedimentation behavior and rheology of the suspensions. It was found that the adsorption process is extremely pH dependent; the maximum adsorption of IA onto alumina surface occurring at a pH close to the value of the first IA dissociation constant, pKa1. Also, IA does not influence the value of the point of zero charge of alumina. It was shown that IA represents an efficient flocculant for concentrated acidic alumina suspensions.

  6. Decomposition of 2-mercaptothiazoline in aqueous solution by ozonation.

    Science.gov (United States)

    Chen, Y H; Chang, C Y; Chen, C C; Chiu, C Y; Yu, Y H; Chiang, P C; Ku, Y; Chen, J N; Chang, C F

    2004-07-01

    This study investigates the ozonation of 2-mercaptothiazoline (2-MT). The 2-MT is one of the important organic additives for the electroplating solution of the printed wiring board industry and has been widely used as a corrosion inhibitor in many industrial processes. It is of concern for the aquatic pollution control especially in the wastewaters. Semibatch ozonation experiments in the completely stirred tank reactor are performed under various concentrations of input ozone. The concentrations of 2-MT, sulfate, and ammonium are analyzed at specified time intervals to elucidate the decomposition of 2-MT during the ozonation. In addition, the time variation of the dissolved ozone concentration (C(ALb)) is continuously monitored in the course of experiments. Total organic carbon (TOC) is chosen and measured as a mineralization index of the ozonation of 2-MT. The results indicate that the decomposition of 2-MT is efficient, while the mineralization of TOC is limited via the ozonation only. Simultaneously, the yield of sulfate with the maximum value of about 47% is characterized by the increases of TOC removal and ozone consumption. These results can provide some useful information for assessing the feasibility of the treatment of 2-MT in the aqueous solution by the ozonation.

  7. Sonochemical degradation of martius yellow dye in aqueous solution.

    Science.gov (United States)

    Singla, Ritu; Grieser, Franz; Ashokkumar, Muthupandian

    2009-01-01

    The sonolytic degradation of the textile dye martius yellow, also known as either naphthol yellow or acid orange 24, was studied at various initial concentrations in water. The degradation of the dye followed first-order kinetics under the conditions examined. Based on gas chromatographic results and sonoluminescence measurements of sonicated aqueous solutions of the dye, it is concluded that pyrolysis does not play a significant role in its degradation. The chromatographic identification of hydroxy added species indicates that an OH radical induced reaction is the main degradation pathway of the dye. Considering the non-volatility and surface activity of the dye, the degradation of the dye most probably takes place at the bubble/solution interface. The quantitative and qualitative formation of the degradation intermediates and final products were monitored using HPLC and ESMS. The analytical results suggest that the sonolytic degradation of the dye proceeds via hydroxylation of the aryl ring and also by C-N bond cleavage of the chromophoric ring, either through OH radical attack or through another unidentified process. The identification of various intermediates and end products also imply that the degradation of martius yellow proceeds through multiple reaction pathways. Total organic carbon (TOC) analyses of the dye solutions at various times following sonication revealed that sonolysis was effective in the initial degradation of the parent dye but very slow in achieving mineralization. The slow rate of mineralization is likely to be due to the inability of many of the intermediate products such as, the carboxylic acids, to accumulate at the bubble (air/water) interface and undergo decomposition due to their high water solubility (low surface activity).

  8. Interaction of gypsum with lead in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Astilleros, J.M., E-mail: jmastill@geo.ucm.es [Dpto. Cristalografia y Mineralogia, Universidad Complutense de Madrid, Jose Antonio Novais, 2, E-28040 Madrid (Spain); Godelitsas, A. [Department of Mineralogy and Petrology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimioupoli Zographou, 15784 Athens (Greece); Rodriguez-Blanco, J.D. [School of Earth and Environments, Faculty of Environment, University of Leeds, Leeds LS2 9JT (United Kingdom); Fernandez-Diaz, L. [Dpto. Cristalografia y Mineralogia, Universidad Complutense de Madrid, Jose Antonio Novais, 2, E-28040 Madrid (Spain); Prieto, M. [Dpto. de Geologia, Universidad de Oviedo, E-30005 Oviedo (Spain); Lagoyannis, A.; Harissopulos, S. [Tandem Accelerator Laboratory, Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Attiki (Greece)

    2010-07-15

    Sorption processes on mineral surfaces are a critical factor in controlling the distribution and accumulation of potentially harmful metals in the environment. This work investigates the effectiveness of gypsum (CaSO{sub 4}.2H{sub 2}O) to sequester Pb. The interaction of gypsum fragments with Pb-bearing solutions (10, 100 and 1000 mg/L) was monitored by performing macroscopic batch-type experiments conducted at room temperature. The aqueous phase composition was periodically determined by Atomic Absorption Spectrometry (AAS), Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Regardless of the [Pb{sub aq}]{sub initial}, a [Pb{sub aq}]{sub final} < 4 mg/L was always reached. The uptake process was fast (t < 1 h) for [Pb{sub aq}]{sub initial} {>=} 100 mg/L and significantly slower (t > 1 week) for [Pb{sub aq}]{sub initial} = 10 mg/L. Speciation calculations revealed that after a long time of interaction (1 month), all the solutions reached equilibrium with respect to both gypsum and anglesite. For [Pb{sub aq}]{sub initial} {>=} 100 mg/L, sorption takes place mainly via the rapid dissolution of gypsum and the simultaneous formation of anglesite both on the gypsum surface and in the bulk solution. In the case of [Pb{sub aq}]{sub initial} = 10 mg/L, no anglesite precipitation was observed, but surface spectroscopy (proton Rutherford Backscattering Spectroscopy, p-RBS) confirmed the formation of Pb-bearing surface layers on the (0 1 0) gypsum surface in this case also. This study shows that the surface of gypsum can play an important role in the attenuation of Pb in contaminated waters.

  9. [Aqueous iodine solutions as disinfectants: composition, stability, comparison with chlorine and bromine solution (author's transl)].

    Science.gov (United States)

    Gottardi, W

    1978-09-01

    The equilibrium concentrations of aqueous iodine solutions in dependence of the total concentration and the pH-value have been calculated with and without regard of the iodate formation. The values obtained by the latter methode enabled by application of the known rate law to calculate the initial rate of the iodate formation and to draw from this conclusions concerning the stability of iodine solutions. On the grounds of these calculations to aqueous iodine solutions in the concentration and pH-range which is relevant for disinfection (greater than 10(-5) M/l, pH 6--9) one can attribute a stability sufficient for the use in practice and - unlike chlorine and bromine solutions - a content of bactericidal "free halogene" which is higher and independent of the pH-value. The disinfecting action of the iodine cation (H2O+J) which is supposed to be very powerful can be neglected because of its low concentration (10(-3)--10(-6%) of the total concentration). Hypoiodic acid which has already been converted into iodate by disproportionation is as good as lost for the disinfection because of the extremely slow reverse reaction.

  10. Improved phenol adsorption from aqueous solution using electrically conducting adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Asghar, Hafiz Muhammad Anwaar; Hussain, Syed Nadir [The University of Manchester, Manchester (United Kingdom); Sattar, Hamed [University of Leeds, Leeds (United Kingdom); Brown, Nigel Willis [Daresbury Innovation Centre, Cheshire (United Kingdom); Roberts, Edward Pelham Lindfield [University of Calgary, Calgary (Canada)

    2014-05-15

    The electrically conducting and partially porous graphite based adsorbent (called Nyex{sup TM} 2000) was tested for its adsorption capacity and electrochemical regeneration ability for the removal of phenol from aqueous solution. Nyex{sup TM} 2000 was tested in comparison with Nyex{sup TM} 1000, which is currently being used for a number of industrial waste water treatment applications. Nyex{sup TM} 1000 exhibited small adsorption capacity of 0.1 mg g{sup -1} for phenol because of having small specific surface area of 1 m{sup 2} g{sup -1}. In contrast, Nyex{sup TM} 2000 with specific surface area of 17 m{sup 2} g{sup -1} delivered an adsorption capacity of 0.8 mg g{sup -1}, which was eight-fold higher than that of Nyex{sup TM} 1000. Nyex{sup TM} 2000 was successfully electrochemically regenerated by passing a current of 0.5 A, charge passed of 31 C g{sup -1} for a treatment time of 45 minutes. These electrochemical parameters were comparable to Nyex{sup TM} 1000 for which a current of 0.5 A, charge passed of 5 C g{sup -1} for a treatment time of 20 minutes were applied for complete oxidation of adsorbed phenol. The comparatively high charge density was found to be required for Nyex{sup TM} 2000, which is justified with its higher adsorption capacity. The FTIR results validated the mineralization of adsorbed phenol into CO{sub 2} and H{sub 2}O except the formation of few by-products, which were in traces when compared with the concentration of phenol removed from aqueous solution. The electrical energy as required for electrochemical oxidation of phenol adsorbed onto Nyex{sup TM} 1000 and 2000 was found to be 214 and 196 J mg{sup -1}, respectively. The comparatively low energy requirement for electrochemical oxidation using Nyex{sup TM} 2000 is consistent with its higher bed electrical conductivity, which is twice that of Nyex{sup TM} 1000.

  11. A study on the reaction between CO2 and alkanolamines in aqueous solutions

    NARCIS (Netherlands)

    Blauwhoff, P.M.M.; Versteeg, G.F.; Swaaij, W.P.M. van

    1983-01-01

    Literature data on the rates of reaction between CO2 and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO2 into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constants were deriv

  12. A study on the reaction between CO2 and alkanolamines in aqueous solutions

    NARCIS (Netherlands)

    Blauwhoff, P.M.M.; Versteeg, G.F.; Swaaij, W.P.M. van

    1984-01-01

    Literature data on the rates of reaction between CO2 and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO2 into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constants were deriv

  13. In Situ Structural Characterization of Ferric Iron Dimers in Aqueous Solutions

    DEFF Research Database (Denmark)

    Zhu, Mengqiang; Puls, Brendan W.; Frandsen, Cathrine

    2013-01-01

    The structure of ferric iron (Fe3+) dimers in aqueous solutions has long been debated. In this work, we have determined the dimer structure in situ in aqueous solutions using extended X-ray absorption fine structure (EXAFS) spectroscopy. An Fe K-edge EXAFS analysis of 0.2 M ferric nitrate solutio...

  14. Density, Viscosity, Solubility, and Diffusivity of N2O in Aqueous Amino Acid Salt Solutions

    NARCIS (Netherlands)

    Kumar, P. Senthil; Hogendoorn, J.A.; Feron, P.H.M.; Versteeg, G.F.

    2001-01-01

    Solubility and diffusivity of N2O in aqueous solutions of potassium taurate are reported over a wide range of concentration and temperature. Also, the solubility of N2O in aqueous potassium glycinate solution is reported at 295 K. The ion specific constants are reported for taurate and glycinate ani

  15. The photochemical decomposition of Indol in an aqueous solution; Descomposicion fotoquimica de Indol en solucion acuosa

    Energy Technology Data Exchange (ETDEWEB)

    Ibarz, A.; Tejero, J.M.; Panades, R.

    1998-06-01

    The photo decomposition of Indol at different pH has been studied. The Indol photo decomposition rate in aqueous solution a maximum at pH 10. By means of a simple mechanism in three steps, it is possible to explain the kinetics behavior of the Indol photo decomposition in aqueous solution. (Author) 6 refs.

  16. Formation of quasi-free and bubble positronium states in water and aqueous solutions

    CERN Document Server

    Stepanov, Serge V; Byakov, Vsevolod M; Zvezhinskiy, D S; Subrahmanyam, V S

    2013-01-01

    It is shown that in aqueous solutions a positronium atom is first formed in the quasi-free state, and, after 50-100 ps, becomes localized in a nanobubble. Analysis of the annihilation spectra of NaNO3 aqueous solutions shows that the hydrated electron is not involved in the positronium (Ps) formation.

  17. Optical properties of chitosan in aqueous solution of L- and D-ascorbic acids

    Science.gov (United States)

    Malinkina, Olga N.; Shipovskaya, Anna B.; Kazmicheva, Olga F.

    2016-04-01

    The optical properties of aqueous chitosan solutions in L- and D-ascorbic acids were studied by optical rotatory dispersion and spectrophotometry. The specific optical rotation [α] of all chitosan solutions tested was positive, in contrast to aqueous solutions of the ascorbic acid enantiomers, which exhibit an inverse relationship of [α] values. Significant differences in the absolute values of [α] of the chitosan solutions at polymer-acid ratios exceeding the equimolar one were found.

  18. Removal of nitrate and phosphate from aqueous solutions by microalgae

    Directory of Open Access Journals (Sweden)

    M.H. Sayadi

    2016-12-01

    Full Text Available The aim of this study was to evaluate the ability of microalgae Spirulina platensis and Chlorella vulgaris to remove nitrate and phosphate in aqueous solutions. Spirulina platensis and Chlorella vulgar is microalgae was collected in 1000 ml of municipal water and KNO3, K2HPO4 was added as sources of nitrate and phosphate in three different concentrations (0.25, 0.35 and 0.45g/L. During the growth period, the concentration of nitrate and phosphate was recorded at 1, 4, 6 and 8 days. The highest nitrate removal on the 8 day for Chlorella vulgaris was 89.80% at the treatment of 0.25g/L and for Spirulina platensis was 81.49% at the treatment of 0.25g/L. The highest phosphate removal for Spirulina platensis was 81.49% at the treatment of 0.45g/L and for Chlorella vulgaris was 88% at the treatment of 0.45g/L. The statistical results showed that the amount of phosphate and nitrate removal during different time periods by Chlorella vulgaris depicted a significant difference at P

  19. Electrochemical degradation of amaranth aqueous solution on ACF.

    Science.gov (United States)

    Fan, Li; Zhou, Yanwei; Yang, Weishen; Chen, Guohua; Yang, Fenglin

    2006-09-21

    The degradation of Amaranth, a kind of azo dye, has been studied under galvanostatic model with activated carbon fiber (ACF) electrode in aqueous solution with electrochemical method. The ACF was used as anode and cathode, respectively for the decolorization process. The onset oxidation potential and reduction potential for Amaranth on ACF were respectively ascertained at 0.6 and -0.4 V. During the range of -1.1 to 0.50 mA cm(-2), the decolorization was clarified into three processes as electroreduction, adsorption and electrooxidation. There were little contributions to the color and COD removals for the process of adsorption. The color removal can be up to 99% when the current density was 0.50 mA cm(-2). The maximum COD removal was 52% for the process of electrooxidation. Hundred percent color removal was obtained when the current density of -1.0 mA cm(-2) was applied. The maximum COD removal was 62% for the electroreduction. The COD removal results from the adsorption of products for the decolorization process of electrooxidation or electroreduction.

  20. Cadmium Removal from Aqueous Solutions by Ground Pine Cone

    Directory of Open Access Journals (Sweden)

    H Izanloo, S Nasseri

    2005-01-01

    Full Text Available A study on the removal of cadmium ions from aqueous solutions by pine cone was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were obtained. The influence of different experimental parameters such as contact time, initial concentration of cadmium, pine cone mass and particle size, and temperature on the kinetics of cadmium removal was studied. Results showed that the main parameters that played an important role in removal phenomenon were initial cadmium concentration, particle size and pine cone mass. The necessary time to reach equilibrium was between 4 and 7 hours based on the initial concentration of cadmium. The capacity of cadmium adsorption at equilibrium increased with the decrease of pine cone particle size. The capacity of cadmium adsorption at equilibrium by pine cone increased with the quantity of pine cone introduced (1–4 g/L. Temperature in the range of 20-30°C showed a restricted effect on the removal kinetics (13.56 mg/g at 20°C and a low capacity of adsorption about 11.48 mg/g at 30°C. The process followed pseudo second-order kinetics. The cadmium uptake of pine cone was quantitatively evaluated using adsorption isotherms. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich equation.

  1. Sonochemical degradation of organophosphorus pesticide in dilute aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    Robina Farooq; FENG Kai-lin; S. F. Shaukat; HUANG Jian-jun

    2003-01-01

    Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2-12. Process parameters studied include pH, steady-state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first-order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water(SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20-70℃ proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.

  2. SORPTION OF Cu2+ FROM AQUEOUS SOLUTIONS BY SLOVAK BENTONITES

    Directory of Open Access Journals (Sweden)

    ANNA BRTÁŇOVÁ

    2012-03-01

    Full Text Available Bentonites are used as barriers in landfills, or in areas of old mining activities to prevent contamination of environment by leachates containing heavy metals. Batch experiments were performed under static conditions to study sorption of Cu2+ from aqueous solutions via adsorption on industrial products made from Slovak bentonites Lieskovec and Jelšový Potok. The samples were characterized by X-ray powder diffraction, infrared spectroscopy and by specific surface area and cation exchange capacities measurements. Effects of pH, concentration of metal cations and contact time were analysed. The adsorption was strongly dependent on pH of the medium, and the uptake of adsorbed metal increased from pH 2.0 to 6.5, while the solubility of Cu at higher pH values decreased. The uptake of Cu2+ was rapid and it increased with increasing metal concentration, while the relative amount of adsorbed Cu2+ decreased. The equilibrium adsorption capacity of the adsorbents used for Cu2+ was extrapolated using the linear Freundlich and Langmuir adsorption isotherms. The Langmuir isotherm was found to fit better the experimental data measured for both bentonites.

  3. Adsorption removal of thiocyanate from aqueous solution by calcined hydrotalcite

    Institute of Scientific and Technical Information of China (English)

    LI Yu-jiang; YANG Min; ZHANG Xiao-jin; WU Tao; CAO Nan; WEI Na; BI Yan-jun; WANG Jing

    2006-01-01

    A hydrotalcite with Mg/Al molar ratio 2 was prepared by co-precipitation method and was characterized by XRD,TG/DTA, Zeta potential and BET surface area. The hydrotalcite was calcined at 500℃, with the dehydration from interlayer, the dehydroxilation from the brucite-like layer and the decomposition of carbonate successively, transformed into the mixed oxide type.The removal of thiocyanate from aqueous solution by using the original hydrotalcite and calcined hydrotalcite (HTC-500) was investigated. The results showed that the thiocyanate adsorption capacity of calcined hydrotalcite was much higher than that of the original form. Calcined hydrotalcite was particularly effective at removing thiocyanate, and that the effective range of pH for the thiocyanate removal are between 5.5-10.0. The experimental data of thiocyanate removal fit nicely with Langmuir isotherm, and the saturated adsorption uptake was 96.2 mg SCN-/g HTC-500. The adsorption ofthiocyanate by calcined hydrotalcite follows first-order kinetics. And the intercalation to the structure recovery for calcined hydrotalcite. But the presence of additional anions could affect the adsorption behavior of thiocyanate.

  4. Adsorption removal of thiocyanate from aqueous solution by calcined hydrotalcite.

    Science.gov (United States)

    Li, Yu-Jiang; Yang, Min; Zhang, Xiao-Jin; Wu, Tao; Cao, Nan; Wei, Na; Bi, Yan-Jun; Wang, Jing

    2006-01-01

    A hydrotalcite with Mg/Al molar ratio 2 was prepared by co-precipitation method and was characterized by XRD, TG/DTA, Zeta potential and BET surface area. The hydrotalcite was calcined at 500 degrees C, with the dehydration from interlayer, the dehydroxilation from the brucite-like layer and the decomposition of carbonate successively, transformed into the mixed oxide type. The removal of thiocyanate from aqueous solution by using the original hydrotalcite and calcined hydrotalcite (HTC-500) was investigated. The results showed that the thiocyanate adsorption capacity of calcined hydrotalcite was much higher than that of the original form. Calcined hydrotalcite was particularly effective at removing thiocyanate, and that the effective range of pH for the thiocyanate removal are between 5.5-10.0. The experimental data of thiocyanate removal fit nicely with Langmuir isotherm, and the saturated adsorption uptake was 96.2 mg SCN-/g HTC-500. The adsorption of thiocyanate by calcined hydrotalcite follows first-order kinetics. And the intercalation to the structure recovery for calcined hydrotalcite. But the presence of additional anions could affect the adsorption behavior of thiocyanate.

  5. Lifetimes of -halo and -azidobenzyl carbocations in aqueous solution

    Indian Academy of Sciences (India)

    R Sanjeev; V Jagannadham

    2002-02-01

    The title cations were produced in aqueous solution by chemical initiation (solvolysis) of benzyl-gem-dihalides and benzyl-gem-diazides. The solvolysis reactions of benzyl-gem-dihalides and benzyl-gem-diazides in water proceed by a stepwise mechanism through -halobenzyl carbocation and -azidobenzyl carbocation intermediates, which are captured by water to give the corresponding carbonyl compounds as the sole detectable products. Rate constant ratio / (M-1) for partitioning of the carbocation between reaction with halide/azide ion and reaction with water is determined by analysis of halide/azide common ion inhibition of the solvolysis reaction. The rate constants (s-1) for the reaction of the cation with solvent water were determined from the experimental values of / and solv, for the solvolysis of the benzyl-gem-dihalides and benzyl-gem-diazides respectively, using = 5 × 109 M-1 s-1 for diffusion-limited reaction of halide/azide ion with -substituted benzyl carbocations. The values of 1/ are thus the lifetimes of the -halobenzyl carbocations and -azidobenzyl carbocations respectively.

  6. The evaporation behavior of sessile droplets from aqueous saline solutions.

    Science.gov (United States)

    Soulié, Virginie; Karpitschka, Stefan; Lequien, Florence; Prené, Philippe; Zemb, Thomas; Moehwald, Helmuth; Riegler, Hans

    2015-09-14

    Quantitative experiments on the evaporation from sessile droplets of aqueous saline (NaCl) solutions show a strong dependence on salt concentration and droplet shape. The experiments were performed with seven decades of initial NaCl concentrations, with various droplet sizes and with different contact angles. The evaporation rate is significantly lower for high salt concentrations and small contact angles than what is expected from the well-accepted diffusion-controlled evaporation scenario for sessile droplets, even if the change of the vapor pressure due to the salt is taken into account. Particle tracking velocimetry reveals that this modification of the evaporation behavior is caused by marangoni flows that are induced by surface tension gradients originating from the local evaporative peripheral salt enrichment. In addition it is found that already very low salt concentrations lead to a pinning of the three phase contact line. Whereas droplets with concentration ≥10(-6) M NaCl are pinned as soon as evaporation starts, droplets with lower salt concentration do evaporate in a constant contact angle mode. Aside from new, fundamental insights the findings are also relevant for a better understanding of the widespread phenomenon of corrosion initiated by sessile droplets.

  7. Photo- and thermal degradation of piroxicam in aqueous solution

    Directory of Open Access Journals (Sweden)

    M Aminuddin

    2011-01-01

    Full Text Available Light and temperature have considerable effect on the degradation of piroxicam in aqueous solutions. The pH and acetate buffer ions also affect the degradation process. The apparent first-order rate constants for the photochemical and thermal degradation of piroxicam have been determined as 2.04-10.01 and 0.86-3.06×10−3 min−1 , respectively. The first-order plots for the degradation of piroxicam showed good linearity within a range of 20-50% loss of piroxicam at pH 2.0-12.0. The rate-pH profile for the photodegradation of piroxicam is a U-shaped curve and for the thermal degradation a bell-shaped curve in the pH range of 2.0-12.0. The thermal degradation of piroxicam was maximum around pH 6.0. It is increased in the presence of acetate ions but was not affected by citrate and phosphate ions.

  8. ADSORPTION FROM AQUEOUS SOLUTION ONTO NATURAL AND ACID ACTIVATED BENTONITE

    Directory of Open Access Journals (Sweden)

    Laila Al-Khatib

    2012-01-01

    Full Text Available Dyes have long been used in dyeing, paper and pulp, textiles, plastics, leather, paint, cosmetics and food industries. Nowadays, more than 100,000 commercial dyes are available with a total production of 700,000 tones manufactured all over the world annually. About 10-15% of dyes are being disposed off as a waste into the environment after dyeing process. This poses certain hazards and environmental problems. The objective of this study is to investigate the adsorption behavior of Methylene Blue (MB from aqueous solution onto natural and acid activated Jordanian bentonite. Both bentonites are firstly characterized using XRD, FTIR and SEM techniques. Then batch adsorption experiments were conducted to investigate the effect of initial MB concentration, contact time, pH and temperature. It was found that the percentage of dye removal was improved from 75.8% for natural bentonite to reach 99.6% for acid treated bentonite. The rate of MB removal followed the pseudo second order model with a high correlation factor. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The Langmuir isotherm model was found more representative. The results indicate that bentonite could be employed as a low cost adsorbent in wastewater treatment for the removal of colour and dyes.

  9. Defluoridation from aqueous solutions by granular ferric hydroxide (GFH).

    Science.gov (United States)

    Kumar, Eva; Bhatnagar, Amit; Ji, Minkyu; Jung, Woosik; Lee, Sang-Hun; Kim, Sun-Joon; Lee, Giehyeon; Song, Hocheol; Choi, Jae-Young; Yang, Jung-Seok; Jeon, Byong-Hun

    2009-02-01

    This research was undertaken to evaluate the feasibility of granular ferric hydroxide (GFH) for fluoride removal from aqueous solutions. Batch experiments were performed to study the influence of various experimental parameters such as contact time (1 min-24h), initial fluoride concentration (1-100 mgL(-1)), temperature (10 and 25 degrees C), pH (3-12) and the presence of competing anions on the adsorption of fluoride on GFH. Kinetic data revealed that the uptake rate of fluoride was rapid in the beginning and 95% adsorption was completed within 10 min and equilibrium was achieved within 60 min. The sorption process was well explained with pseudo-first-order and pore diffusion models. The maximum adsorption capacity of GFH for fluoride removal was 7.0 mgg(-1). The adsorption was found to be an endothermic process and data conform to Langmuir model. The optimum fluoride removal was observed between pH ranges of 4-8. The fluoride adsorption was decreased in the presence of phosphate followed by carbonate and sulphate. Results from this study demonstrated potential utility of GFH that could be developed into a viable technology for fluoride removal from drinking water.

  10. Batch liquid-liquid extraction of phenol from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Palma, M.S.A.; Shibata, C. [Department of Biochemical Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo-SP (Brazil); Paiva, J.L. [Department of Chemical Engineering, Polytechnical School, University of Sao Paulo, Sao Paulo-SP (Brazil); Zilli, M. [Department of Chemical and Process Engineering, University of Genoa, Genoa (Italy); Converti, A.

    2010-01-15

    The aim of this work is the study of batch liquid-liquid extraction of phenol from aqueous solutions in a bench-scale well-mixed reactor. The influence of the ratio of phase volumes, temperature, and rotational speed on phenol removal (0.72-1.1 % w/w) was investigated using methyl isobutyl ketone as an extracting solvent. For this purpose, the ratio of phase volumes were set at 0.1 and 0.2, the temperature at 10, 20, and 30 C, and the rotational speed at 300, 400, and 500 rpm. A physical model based on the material balance of the phases as well as the equation of mass flux between the phases allowed the estimation of the overall coefficient of mass transfer coupled with the superficial area. Moreover, it proved to fit, satisfactorily well, the experimental data of residual phenol concentration in the organic phase versus time under all the conditions investigated. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Structure of aqueous electrolyte solutions near a hydrophobic surface

    Directory of Open Access Journals (Sweden)

    M.Kinoshita

    2007-09-01

    Full Text Available The structure of aqueous solutions of 1:1 salts (KCl, NaCl, KF,and CsI near a hydrophobic surface is analysed using the angle-dependent integral equation theory. Water molecules are taken to be hard spheres imbedded with multipolar moments including terms up to octupole order, and hard spherical ions are immersed in this model water. The many-body interactions associated with molecular polarizability are treated at the self-consistent mean field level. The effects of cationic and anionic sizes and salt concentration in the bulk are discussed in detail. As the salt concentration increases, the layer of water molecules next to the surface becomes denser but its orientational order remains almost unchanged. The concentration of each ion at the surface can be drastically different from that in the bulk. Asa striking example, at sufficiently low salt concentrations, the concentration of I- is about 500 times higher than that of F- at the surface.

  12. Effect of nanotechnology on heavy metal removal from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Hoda Kahrizi; Ali Bafkar; Masumeh Farasati

    2016-01-01

    The effect of nanotechnology on cadmium and zinc removal from aqueous solution was investigated. In order to characterize micro and nano phragmites australis adsorbent, we analyzed the data via FTIR, SEM, PSA, and EDX. The effect of various parameters such as pH, contact time, amount of adsorbent and initial concentration, was investigated. The optimum pH for the removal of cadmium for micro and nano phragmites australis adsorbent was 7, and for the removal of zinc by the micro adsorbent was 7 and by nano adsorbent was 6. The equilibrium time of zinc was 90 min and for the adsorption of cadmium by micro and nano adsorbent were 90 and 30 min, respectively. The optimum dose of micro adsorbent for the removal of cadmium was 0.7 g, and the other dose for the removal of zinc and cadmium was 0.5 g. The evaluation of adsorbent’s distribution coefficient showed that the highest rates of distribution coefficient with initial concentration of 5, 10, 30, and 50 mg/L were 394.83, 587.62, 759.39 and 1101.52 L/kg, respectively, which were observed in nano adsorbent. Desorption experiments for the nano adsorbent in three cycles were done. Among kinetics models, our experimental data were more consistent with Hoo kinetic model and for isotherm models, Freundlich isotherm was more consistent. The results show that nanotechnology could increase the performance of adsorbents and enhance the efficiency of the adsorption of cadmium and zinc ions.

  13. Modeling platinum group metal complexes in aqueous solution.

    Science.gov (United States)

    Lienke, A; Klatt, G; Robinson, D J; Koch, K R; Naidoo, K J

    2001-05-07

    We construct force fields suited for the study of three platinum group metals (PGM) as chloranions in aqueous solution from quantum chemical computations and report experimental data. Density functional theory (DFT) using the local density approximation (LDA), as well as extended basis sets that incorporate relativistic corrections for the transition metal atoms, has been used to obtain equilibrium geometries, harmonic vibrational frequencies, and atomic charges for the complexes. We found that DFT calculations of [PtCl(6)](2-).3H(2)O, [PdCl(4)](2-).2H(2)O, and [RhCl(6)](3-).3H(2)O water clusters compared well with molecular mechanics (MM) calculations using the specific force field developed here. The force field performed equally well in condensed phase simulations. A 500 ps molecular dynamics (MD) simulation of [PtCl(6)](2-) in water was used to study the structure of the solvation shell around the anion. The resulting data were compared to an experimental radial distribution function derived from X-ray diffraction experiments. We found the calculated pair correlation functions (PCF) for hexachloroplatinate to be in good agreement with experiment and were able to use the simulation results to identify and resolve two water-anion peaks in the experimental spectrum.

  14. Morphology control of brushite prepared by aqueous solution synthesis

    Directory of Open Access Journals (Sweden)

    T. Toshima

    2014-03-01

    Full Text Available Dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O, also known as brushite, is one of the important bioceramics due to not only diseases factors such as kidney stone and plaque formation but also purpose as fluoride insolubilization material. It is used medicinally to supply calcium, and is of interest for its unique properties in biological and pathological mineralization. It is important to control the crystal morphology of brushite since its chemical reactivity depends strongly on its surface properties; thus, its morphology is a key issue for its applications as a functional material or precursor for other bioceramics. Here, we report the effects of the initial pH and the Ca and phosphate ion concentrations on the morphology of DCPD particles during aqueous solution synthesis. Crystal morphologies were analyzed by scanning electron microscopy and X-ray diffraction. The morphology phase diagram of DCPD crystallization revealed that increasing the initial pH and/or ion concentration transformed DCPD morphology from petal-like into plate-like structures.

  15. Heavy metal removal from aqueous solutions by activated phosphate rock

    Energy Technology Data Exchange (ETDEWEB)

    Elouear, Z. [Laboratoire Eau Energie et Environnement, Departement de genie geologique, Ecole Nationale d' Ingenieurs de Sfax, BP W 3038, Sfax (Tunisia)], E-mail: zouheir.elouaer@tunet.tn; Bouzid, J.; Boujelben, N. [Laboratoire Eau Energie et Environnement, Departement de genie geologique, Ecole Nationale d' Ingenieurs de Sfax, BP W 3038, Sfax (Tunisia); Feki, M. [Unite de chimie industriel I, Ecole Nationale d' Ingenieurs de Sfax, BP W 3038 Sfax (Tunisia); Jamoussi, F. [Laboratoire de Georessources CERTE BP 95, 2050 Hamam-Lif (Tunisia); Montiel, A. [Societe Anonyme de Gestion des Eaux de Paris, 9 rue Schoelcher, 75675 Paris cedex 14 (France)

    2008-08-15

    The use of natural adsorbent such as phosphate rock to replace expensive imported synthetic adsorbent is particularly appropriate for developing countries such as Tunisia. In this study, the removal characteristics of lead, cadmium, copper and zinc ions from aqueous solution by activated phosphate rock were investigated under various operating variables like contact time, solution pH, initial metal concentration and temperature. The kinetic and the sorption process of these metal ions were compared for phosphate rock (PR) and activated phosphate rock (APR). To accomplish this objective we have: (a) characterized both (PR) and (APR) using different techniques (XRD, IR) and analyses (EDAX, BET-N{sub 2}); and, (b) qualified and quantified the interaction of Pb{sup 2+}, Cd{sup 2+}, Cu{sup 2+} and Zn{sup 2+} with these sorbents through batch experiments. Initial uptake of these metal ions increases with time up to 1 h for (PR) and 2 h for (APR), after then, it reaches equilibrium. The maximum sorption obtained for (PR) and (APR) is between pH 2 and 3 for Pb{sup 2+} and 4 and 6 for Cd{sup 2+}, Cu{sup 2+} and Zn{sup 2+}. The effect of temperature has been carried out at 10, 20 and 40 deg. C. The data obtained from sorption isotherms of metal ions at different temperatures fit to linear form of Langmuir sorption equation. The heat of sorption ({delta}H{sup o}), free energy ({delta}G{sup o}) and change in entropy ({delta}S{sup o}) were calculated. They show that sorption of Pb{sup 2+}, Cd{sup 2+}, Cu{sup 2+} and Zn{sup 2+}on (PR) and (APR) an endothermic process. These findings are significant for future using of (APR) for the removal of heavy metal ions from wastewater under realistic competitive conditions in terms of initial heavy metals, concentrations and pH.

  16. Spreading of aqueous SDS solutions over nitrocellulose membranes.

    Science.gov (United States)

    Zhdanov, S A; Starov, V M; Sobolev, V D; Velarde, M G

    2003-08-15

    Experimental investigations were carried out on the spreading of small drops of aqueous SDS solutions over dry thin porous substrates (nitrocellulose membranes) in the case of partial wetting. The time evolution was monitored of the radii of both the drop base and the wetted area inside the porous substrate. The total duration of the spreading process was subdivided into three stages: the first stage: the drop base expands until the maximum value of the drop base is reached, the contact angle rapidly decreases during this stage; the second stage: the radius of the drop base remains constant and the contact angle decreases linearly with time; the third stage: the drop base shrinks and the contact angle remains constant. The wetted area inside the porous substrate expends during the whole spreading process. Appropriate scales were used with a plot of the dimensionless radii of the drop base, of the wetted area inside the porous substrate and the dynamic contact angle on the dimensionless time. Our experimental data show: the overall time of the spreading of drops of SDS solution over dry thin porous substrates decreases with the increase of surfactant concentration; the difference between advancing and hydrodynamic receding contact angles decreases with the surfactant concentration increase; the constancy of the contact angle during the third stage of spreading has nothing to do with the hysteresis of contact angle, but determined by the hydrodynamic reasons. It is shown using independent spreading experiments of the same drops on nonporous nitrocellulose substrate that the static receding contact angle is equal to zero, which supports our conclusion on the hydrodynamic nature of the hydrodynamic receding contact angle on porous substrates.

  17. Reomoval of Heavy Metals from Aqueous Solutions using Bascteria

    Institute of Scientific and Technical Information of China (English)

    HUANGMin-sheng; PANjing; 等

    2001-01-01

    The accumulation of heavy metals by microbial biomass with high surface area-to-volume ratio holds great potential for heavy metal removal in both soluble and particular forms,especially when the heavy metal concentrations are low(<50mg/L),E.coli and B.Subtilis are effective agents for metal removal.We further investigated the effect of pH,temperature,equilibration time,and pre-treatment reagents on the removal of pH(Ⅱ),Cd(Ⅱ) and Cr(VI) from aqueous solutions by E.Coli and B.subtilis.E.coli and B.subtilis were cultivated for 60 hours,the experimentally determined optimal cultivation time before they were used in metal removal experiments,Under the optimal conditions of pH 6.0,equilibration temperature 30℃ and equilibration time 1 hour,63.39% and 69.90%Cd(Ⅱ) can be removed by E.coli and B.subtilis.Under the optimal conditions of pH5.5,equilibration temperature 30℃ and equliobration time 1 hour,68.51% and 67.36% pB(Ⅱ) can be removed by E.coli and B.subtilis.And under the optimal conditons of pH5.5,equilibration temperature 30℃,and equilibration time 1 hour,60.26% and 54.56% Cr(VI) can be removed by E.coli and B.subtilis.Chemical treatment of cultivated bacteria(0.1mol/L NaOH,0.1mol/L HCl,30% ethanol,and distilled water)affects the efficiency of metal removal by E.coli and B.subtilis,pretreatment of biomass by NaOH enhanced Cd(Ⅱ),Pb(Ⅱ)and Cr(VI) removal,while preteatment by HCl,ethanol and distilled water reduced Ca(Ⅱ) ,Pb(Ⅱ) and Cr(VI) removal,For metal removal from industrial waste discharges,pretreated biomass of E.coli can remove 68.5% of Cd and 58.1% of Cr from solutions,while pretreated biomass of B.subtilis can remove 62.6% of Cd and 57% of Cr from Solutions.

  18. Mineralization of paracetamol in aqueous solution with advanced oxidation processes.

    Science.gov (United States)

    Torun, Murat; Gültekin, Özge; Şolpan, Dilek; Güven, Olgun

    2015-01-01

    Paracetamol is a common analgesic drug widely used in all regions of the world more than hundred tonnes per year and it poses a great problem for the aquatic environment. Its phenolic intermediates are classified as persistent organic pollutants and toxic for the environment as well as human beings. In the present study, the irradiation of aqueous solutions of paracetamol with 60Co gamma-rays was examined on a laboratory scale and its degradation path was suggested with detected radiolysis products. The synergic effect of ozone on gamma-irradiation was investigated by preliminary ozonation before irradiation which reduced the irradiation dose from 5 to 3 kGy to completely remove paracetamol and its toxic intermediate hydroquinone from 6 to 4 kGy as well as increasing the radiation chemical yield (Gi values 1.36 and 1.66 in the absence and presence of ozone, respectively). The observed amount of formed hydroquinone was also decreased in the presence of ozone. There is a decrease in pH from 6.4 to 5.2 and dissolved oxygen consumed, which is up to 0.8 mg l(-1), to form some peroxyl radicals used for oxidation. Analytical measurements were carried out with gas chromatography/mass spectrometry and ion chromatography (IC) both qualitatively and quantitatively. Amounts of paracetamol and hydroquinone were measured with gas chromatography after trimethylsilane derivatization. Small aliphatic acids, such as acetic acid, formic acid and oxalic acid, were measured quantitatively with IC as well as inorganic ions (nitrite and nitrate) in which their yields increase with irradiation.

  19. Ultrasound assisted enzymatic depolymerization of aqueous guar gum solution.

    Science.gov (United States)

    Prajapat, Amrutlal L; Subhedar, Preeti B; Gogate, Parag R

    2016-03-01

    The present work investigates the effectiveness of application of low intensity ultrasonic irradiation for the intensification of enzymatic depolymerization of aqueous guar gum solution. The extent of depolymerization of guar gum has been analyzed in terms of intrinsic viscosity reduction. The effect of ultrasonic irradiation on the kinetic and thermodynamic parameters related to the enzyme activity as well as the intrinsic viscosity reduction of guar gum using enzymatic approach has been evaluated. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. It has been observed that application of ultrasound not only enhances the extent of depolymerization but also reduces the time of depolymerization as compared to conventional enzymatic degradation technique. In the presence of cellulase enzyme, the maximum extent of depolymerization of guar gum has been observed at 60 W of ultrasonic rated power and ultrasonic treatment time of 30 min. The effect of ultrasound on the kinetic and thermodynamic parameters as well as the molecular structure of cellulase enzyme was evaluated with the help of the chemical reaction kinetics model and fluorescence spectroscopy. Application of ultrasound resulted in a reduction in the thermodynamic parameters of activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) by 47%, 50%, 65% and 1.97%, respectively. The changes in the chemical structure of guar gum treated using ultrasound assisted enzymatic approach in comparison to the native guar gum were also characterized by FTIR. The results revealed that enzymatic depolymerization of guar gum resulted in a polysaccharide with low degree of polymerization, viscosity and consistency index without any change in the core chemical structure which could make it useful for incorporation in food products.

  20. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jun-Ho; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng, E-mail: mcho@korea.ac.kr [Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 136-713 (Korea, Republic of); Department of Chemistry, Korea University, Seoul 136-713 (Korea, Republic of); Kim, Heejae; Kim, Seongheun [Department of Chemistry, Korea University, Seoul 136-713 (Korea, Republic of)

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O—D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O—D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O—D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O—D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O—D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O—D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O—D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O—D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O—D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O—D stretch mode is shown to be important and the asymmetric line shapes of the O—D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We

  1. Method for Non-Invasive Determination of Chemical Properties of Aqueous Solutions

    Science.gov (United States)

    Todd, Paul W. (Inventor); Jones, Alan (Inventor); Thomas, Nathan A. (Inventor)

    2016-01-01

    A method for non-invasively determining a chemical property of an aqueous solution is provided. The method provides the steps of providing a colored solute having a light absorbance spectrum and transmitting light through the colored solute at two different wavelengths. The method further provides the steps of measuring light absorbance of the colored solute at the two different transmitted light wavelengths, and comparing the light absorbance of the colored solute at the two different wavelengths to determine a chemical property of an aqueous solution.

  2. Thermodynamics of polyamide separation membrane in contact with aqueous solutions

    Science.gov (United States)

    Zhang, Xijing

    Composite reverse osmosis (RO) membranes, which are typically comprised of a polyamide active-layer that is formed by interfacial polymerization on a porous polysulfone support, are widely used in technologies for desalination and water purification. The water permeation and the rejection of salts or other contaminants are mainly determined by the transport properties of the polyamide active layer. Both the permeabilities of water and salt are described using solution-diffusion model and the mechanism of salt distribution in polyamide is distinguished into ion-exchange and ion partitioning. The ion partition coefficient κ in the active layer is a key thermodynamic parameter that partially controls the ability of the membrane to desalinate water. FT30 membranes are soaked in aqueous solutions of CsCl, KBr, or Na 2WO4, freeze-dried to remove water without disturbing ion distribution, and analyzed by Rutherford backscattering spectrometry. κ is calculated as ˜ 6 from the ion concentration in active layer measured using RBS and porosity in the polysulfone support layer is also derived as 40--50% from RBS data. Stress change induced by salt distribution is investigated with an optical system. Stress goes up to 9 MPa for transferred polyamide active layer from commercial RO membrane FT30 and 8 MPa for lab-synthesized polyamide film. The saturation in stress change is due to the pre-occupation of ions onto all the stress-related sites. The absorption of water in reverse osmosis membranes FT30 and LF10 is investigated by a combination of measurements of water mass uptake and biaxial stress as a function of relative humidity. Water solubility in polyamide active layer is 12 wt% at a relative humidity of 95%. The slope of a water concentration versus humidity curve can be used to calculate inter-diffusivity of water in polyamide active layers. By combining the measurements of water mass uptake and biaxial stress, we estimate the specific volume of water in the active

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

    Directory of Open Access Journals (Sweden)

    Zun Maria

    2014-12-01

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

  4. Laser-induced photoelectrochemistry: scavenging of photoemitted electrons in aqueous and non-aqueous solutions by electroactive organic species

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, J.H. (Lawrence Livermore Lab., CA); Kovalenko, L.J.; Deutscher, S.B.; Harrar, J.E.; Perone, S.P.

    1980-01-01

    Photoemission current at a mercury electrode has been characterized electrochemically for aqueous solutions of methyl viologen, the disodium salt of anthraquinone-1,5-disulfonic acid, hydroquinone, p-benzoquinone, and chlorophyllin, and in DMF solutions of N/sub 2/O and anthraquinone. The scavenging species could be determined by comparing photoemission current-voltage curves with polarographic and cyclic voltammetric data. 11 figures.

  5. Preparation of CdTe nanocrystal-polymer composite microspheres in aqueous solution by dispersing method

    Institute of Scientific and Technical Information of China (English)

    LI Minjie; WANG Chunlei; HAN Kun; YANG Bai

    2005-01-01

    Highly fluorescent CdTe nanocrystals were synthesized in aqueous solution, and then processible CdTe nanocrystal-polymer composites were fabricated by coating the aqueous nanocrystals with copolymers of styrene and octadecyl-p-vinyl-benzyldimethylammonium chloride (SOV- DAC) directly. A dichloromethane solution of CdTe nano- crystal-polymer composites was dispersed in the aqueous solution of poly (vinyl alcohol) (PVA) generating highly fluorescent microspheres. Experimental parameters such as the concentration of nanocrystal-polymer composites, the concentration of PVA, and stirring speed which had important effect on the preparation of the microspheres were investigated in detail with fluorescent microscope characterization.

  6. Formation and disappearance of superoxide radicals in aqueous solutions. [79 references

    Energy Technology Data Exchange (ETDEWEB)

    Allen, A O; Bielski, B H.J.

    1980-01-01

    A literature review of superoxide radicals in aqueous solutions is presented covering the following: history; methods of formation of aqueous HO/sub 2//HO/sub 2//sup -/ by radiolysis and photolysis, electrolysis, mixing nonaqueous solutions into water, chemical reactions, enzymatic generation of O/sub 2//sup -/, and photosensitization; and properties of HO/sub 2//O/sub 2//sup -/ in aqueous solution, which cover spontaneous dismutation rates, pk and absorption spectra, catalyzed dismutation, thermodynamics and the so-called Haber-Weiss Reaction.

  7. Linear polymer aqueous solutions in soft lubrication:From boundary to mixed lubrication

    Institute of Scientific and Technical Information of China (English)

    LIU; ShuHai; TAN; GuiBin; WANG; DeGuo

    2013-01-01

    In order to better understand linear polymer aqueous solutions in soft lubrication from boundary to mixed lubrication,poly(ethylene glycol) and sodium hyaluronateare used as model polymers were investigated by using UMT-2 tribometer with the ball-on-disk mode. The relationship between the master Stribeck curves of the polymer aqueous solutions and the influence factors were investigated. Experimental results indicated that soft lubrication is determined by lubricant rheological properties and surface-lubricant interactions, e.g., wetting behavior of polymer aqueous solution on tribological surfaces.

  8. Hydrate phase equilibria of CO2+N2+aqueous solution of THF, TBAB or TBAF system

    DEFF Research Database (Denmark)

    Sfaxi, Imen Ben Attouche; Durand, Isabelle; Lugo, Rafael

    2014-01-01

    We report hydrate dissociation conditions of CO2 (15 and 30mol%)+N2 (85 and 70mol%) in the presence of aqueous solutions of THF, TBAB or TBAF. The concentrations of TBAB and TBAF in the aqueous solutions are 5wt% and 9wt% while THF concentration in aqueous solution is 3mol%. Two different...... experimental techniques including isochoric pressure search method and a DSC method are used to measure the hydrate dissociation conditions. A comparison is finally made with the literature data. It is expected that this study provides better understanding of hydrate phase equilibria associated with CO2...... capture. © 2014 Elsevier Ltd....

  9. Cryo-irradiation as a terminal method for the sterilization of drug aqueous solutions.

    Science.gov (United States)

    Maquille, Aubert; Habib Jiwan, Jean-Louis; Tilquin, Bernard

    2008-05-01

    The aim of this study is to evaluate the specificities of the irradiation of drugs in frozen aqueous solution. The structures of the degradation products were determined to gain insight into the radiolysis mechanisms occurring in frozen aqueous solutions. Metoclopramide hydrochloride and metoprolol tartrate were chosen as models. The frozen solutions were irradiated at dry ice temperature by high energy electrons at various doses. The drug purity (chemical potency) and the radiolysis products were quantified by HPLC-DAD. Characterization of the degradation products was performed by LC-APCI-MS-MS. The structures of the radiolysis products detected in irradiated frozen aqueous solutions were compared to those detected in solid-state and aqueous solutions (previous studies). For both metoclopramide and metoprolol, solute loss upon irradiation of frozen aqueous solutions was negligible. Five radiolysis products present in traces were identified in irradiated metoclopramide frozen solutions. Three of them were previously identified in solid-state irradiated metoclopramide crystals. The two others were formed following reactions with the hydroxyl radical (indirect effect). Only one fragmentation product was observed in irradiated metoprolol frozen solutions. For both drugs, radiosterilization of frozen solutions, even at high doses (25 kGy), was found to be possible.

  10. 1,3-DIPOLAR CYCLOADDITION OF PHENYL AZIDE TO NORBORNENE IN AQUEOUS-SOLUTIONS

    NARCIS (Netherlands)

    Wijnen, J.W; Steiner, R.A.; Engberts, J.B.F.N.

    1995-01-01

    Second-order rate constants for the cycloaddition of phenyl azide to norbornene were determined in aqueous solutions. In organic solvents this reaction shows a very small solvent effect. In highly aqueous media, however, remarkable accelerations are observed. The solvent dependence of the rate const

  11. [Extraction of 2-amino-4-nitrophenol and 4-phenylphenol from aqueous solutions].

    Science.gov (United States)

    Fursova, I A; Shormanov, V K

    2002-01-01

    The authors provide the results of extraction of 2-amino-4-nitrophenol and 4-phenilphenol from aqueous solutions by five organic soluvants. The dependence of the extraction degree on some factors (nature of extragent, pH of aqueous phase medium, extragents saturation with water) was established. Necessary extraction rate for isolation of preset quality of the test substances was calculated.

  12. Pulse radiolysis of tetrazolium violet in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kovacs, A. [Institute of Isotopes, Hungarian Academy of Sciences, P.O. Box 77, H-1525 Budapest (Hungary)], E-mail: akovacs@iki.kfki.hu; Wojnarovits, L.; Palfi, T. [Institute of Isotopes, Hungarian Academy of Sciences, P.O. Box 77, H-1525 Budapest (Hungary); Emi-Reynolds, G. [Radiation Protection Institute, Ghana Atomic Energy Commission, P.O. Box LG 80, Legon-Accra (Ghana); Fletcher, J. [Department of Physics, University of Cape Coast, Cape Coast (Ghana)

    2008-09-15

    The radiolytic reduction of colourless tetrazolium salts to coloured formazans in liquid and solid state is suggested for dosimetry purposes. In order to clarify the reaction mechanism, a pulse radiolysis study was conducted in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions. Under reducing conditions, fast formation of the electron adduct tetrazolinyl radical was observed: coloured formazan final product formed during the decay of electron adduct. Both the decay of the tetrazolinyl radical and the formation of the formazan were found to be second order. The spectra of the formazan were similar in neutral and alkaline solutions, but with higher absorbance in the latter solutions due to the higher molar absorption coefficient. Under oxidative conditions formazan did not form; hydroxylated products through OH-adducts were observed in the pH range studied.

  13. Pulse radiolysis of tetrazolium violet in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions

    Science.gov (United States)

    Kovács, A.; Wojnárovits, L.; Pálfi, T.; Emi-Reynolds, G.; Fletcher, J.

    2008-09-01

    The radiolytic reduction of colourless tetrazolium salts to coloured formazans in liquid and solid state is suggested for dosimetry purposes. In order to clarify the reaction mechanism, a pulse radiolysis study was conducted in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions. Under reducing conditions, fast formation of the electron adduct tetrazolinyl radical was observed: coloured formazan final product formed during the decay of electron adduct. Both the decay of the tetrazolinyl radical and the formation of the formazan were found to be second order. The spectra of the formazan were similar in neutral and alkaline solutions, but with higher absorbance in the latter solutions due to the higher molar absorption coefficient. Under oxidative conditions formazan did not form; hydroxylated products through OH-adducts were observed in the pH range studied.

  14. Impacts of different draw solutions on a novel anaerobic forward osmosis membrane bioreactor (AnFOMBR).

    Science.gov (United States)

    Tang, Melvin Kai Yin; Ng, How Yong

    2014-01-01

    Two anaerobic forward osmosis (FO) membrane bioreactors (AnFOMBRs), Rchloride and Rsulfate, were operated for 100 days using NaCl and Na2SO4 as the draw solution, respectively. The operating conditions were identical for both systems, with a solids retention time of 30 d, hydraulic retention time of 8 h and using cellulose triacetate FO membrane. High rejection performance of FO membranes resulted in salinity accumulation in the bioreactors. Rchloride and Rsulfate reached a stable conductivity of about 35 and 11 mS/cm, respectively, at the end of the experimental run. Hypersalinity of Rchloride undesirably impacted biological growth; mixed liquor volatile suspended solids in Rchloride was much lower at 376 mg/L, whereas that of Rsulfate was 1,170 mg/L. Organic removals were excellent due to reduced organic loadings at low fluxes and thus, Rsulfate and Rchloride achieved secondary total organic carbon (TOC) removal efficiencies of at least 75%. Both AnFOMBRs started with an initial flux of 5 LMH. Flux for Rchloride stabilized at 0.25 LMH, while Rsulfate at 0.96 LMH. The high salinities of both reactors negatively impacted methanogenic growth. Application of the fluorescence in-situ hybridization (FISH) technique confirmed the ousting of methanogens by sulfate reducing bacteria from the anaerobic consortium. Sparsely located methanogens were detected in Rchloride but none were detected in Rsulfate.

  15. Decomposition Studies of Triphenylboron, Diphenylborinic Acid and Phenylboric Acid in Aqueous Alkaline Solutions Containing Copper

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, C.L. [Westinghouse Savannah River Company, AIKEN, SC (United States); Peterson, R. A.

    1997-02-11

    This report documents the copper-catalyzed chemical kinetics of triphenylboron, diphenylborinic acid and phenylboric acid (3PB, 2PB and PBA) in aqueous alkaline solution contained in carbon-steel vessels between 40 and 70 degrees C.

  16. Absorption of nitric oxide into aqueous solutions of ferrous chelates accompanied by instantaneous reaction

    NARCIS (Netherlands)

    Demmink, J.F; vanGils, I.C.F.; Beenackers, A.A C M

    1997-01-01

    The absorption of nitric oxide (NO) into aqueous solutions of ferrous chelates of nitrilotriacetic acid (NTA), ethylene diaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), and diethylenetriaminepentaacetic acid (DTPA) was studied in a stirred cell reactor. Experimental cond

  17. Thermodynamics of the complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions

    Science.gov (United States)

    Mudarisova, R. Kh.; Badykova, L. A.

    2016-03-01

    The thermodynamics of complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions is studied by means spectroscopy. The standard thermodynamic characteristics (Δ H°; Δ G°; Δ S°) of complexation are calculated.

  18. Albendazole Solubilization in Aqueous Solutions of Nicotinamide: Thermodynamics and Solute Solvent Interactions

    Directory of Open Access Journals (Sweden)

    Sushree Tripathy

    2013-12-01

    Full Text Available The present study deals with experiments so as to highlight the solute (drug albendazole – solvent ( water interactions and related thermodynamic modifications in presence of the hydrotropic agent nicotinamide at different temperatures T (= 298.15 to 313.15K. Density and conductivity values of albendazole have been determined in water in (0.2, 0.4, 0.6, 0.8, 1 and 2 mol dm-3 aqueous solutions of nicotinamide at temperatures T(= 298.15, 303.15, 308.15 and 313.15K, where as solubility was studied at 308.15. A concentration dependent solubility enhancement of albendazole was observed. The solubility data was treated to obtain the concentration dependent solubilization efficiency and the Gibbs free energy of transfer (∆G0tr of albendazole from pure water to the solvent systems. From the density values, the limiting partial molar volumes and expansibilities have been calculated. The limiting molar conductance (L0 and Arrhenius activation energy (Es values have been calculated from the generated conductance values. The thermo physical parameters were discussed in terms of solute solvent interactions.

  19. Removal of Cadmium and Lead Ions from Aqueous Solution by Nanocrystalline Magnetite Through Mechanochemical Activation

    OpenAIRE

    Mohsen Hosseinzadeh; Seyyed Ali Seyyed Ebrahimi; Shahram Raygan; Seyed Morteza Masoudpanah

    2016-01-01

    In this study, the removal of cadmium and lead ions from aqueous solution by nanocrystalline magnetite was investigated. The nanocrystalline magnetite was synthesized by mechanochemical activation of hematite in a high energy planetary mill in argon atmosphere for 45 hours. The ability of the synthesized nanocrystalline magnetite for removal of Cd(II) and Pb(II) from aqueous solutions was studied in a batch reactor under different experimental conditions with different pHs, contact times, ini...

  20. Pervaporation of Aqueous Solution of Acetaldehyde Through ZSM-5 Filled PDMS Composite Membrane

    Institute of Scientific and Technical Information of China (English)

    伍艳辉; 谭惠芬; 李佟茗; 金源

    2012-01-01

    Hydrophobic ZSM-5 zeolite filled polydimethylsiloxane (PDMS) composite membranes with Nylon micro-filtration membrane as the support layer were prepared to separate acetaldehyde from its aqueous solution. The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Their structural morphology and thermal stability were also examined. The swelling study showed that the composite membranes presented higher degree of swelling in aqueous solution of acetaldehyde than in pure water at 25℃,

  1. Relation between the solubility of proteins in aqueous solutions and the second virial coefficient of the solution

    NARCIS (Netherlands)

    Haas, C; Drenth, J; Wilson, WW

    1999-01-01

    Tn recent publications it was pointed out that there is a correlation between the observed values of the solubility of proteins in aqueous solutions and the second virial coefficient of the solution. In this paper we give a theoretical explanation of this relation. The derived theoretical expression

  2. Effect of biochar addition on hydrogen and methane production in two-phase anaerobic digestion of aqueous carbohydrates food waste.

    Science.gov (United States)

    Sunyoto, Nimas M S; Zhu, Mingming; Zhang, Zhezi; Zhang, Dongke

    2016-11-01

    Effect of biochar addition on hydrogen and methane production in two-phase anaerobic digestion of aqueous carbohydrates was studied using bench-scale bioreactors. The cultures with biochar additions were placed in 100ml reactors and incubated at 35°C and pH 5 for hydrogen production. The residual cultures were then used for methane production, incubated at 35°C and pH 7. Daily yields of hydrogen and methane and weekly yield of volatile fatty acids (VFA) were measured. The hydrogen and methane production potentials, rate and lag phases of the two phases were analysed using the Gompertz model. The results showed that biochar addition increased the maximum production rates of hydrogen by 32.5% and methane 41.6%, improved hydrogen yield by 31.0% and methane 10.0%, and shortened the lag phases in the two phases by 36.0% and 41.0%, respectively. Biochar addition also enhanced VFA generation during hydrogen production and VFA degradation in methane production.

  3. Oxidation of atrazine by photoactivated potassium persulfate in aqueous solutions

    Science.gov (United States)

    Khandarkhaeva, M. S.; Aseev, D. G.; Sizykh, M. R.; Batoeva, A. A.

    2016-11-01

    General laws of the photochemical oxidation of atrazine by inorganic peroxo compounds under the impact of solar radiation are studied. It is found that almost complete conversion of atrazine can be achieved via photochemical oxidation with persulfate after 120 min, but no deep mineralization is observed. The effect an aqueous matrix has on the processes of atrazine degradation in combined oxidation systems is considered.

  4. Characterization of trehalose aqueous solutions by neutron spin echo

    CERN Document Server

    Branca, C; Magazù, S; Maisano, G; Mangione, A; Pappas, C; Triolo, A

    2002-01-01

    The present work reports neutron spin-echo (NSE) results on aqueous mixtures of trehalose, a naturally occurring disaccharide of glucose, which shows an extraordinary bioprotective effectiveness against dehydration and freezing. The aim of the work is to furnish new results on the dynamics of the trehalose/water system on the nano- and picosecond scales. (orig.)

  5. Characterization of trehalose aqueous solutions by neutron spin echo

    Energy Technology Data Exchange (ETDEWEB)

    Branca, C.; Faraone, A.; Magazu' , S.; Maisano, G.; Mangione, A. [Dipartimento di Fisica and INFM, Universita di Messina, PO Box 55, 98166 Messina (Italy); Pappas, C.; Triolo, A. [Hahn-Meitner-Institut, BENSC (NI), Glienicker Strasse, 14109 Berlin (Germany)

    2002-07-01

    The present work reports neutron spin-echo (NSE) results on aqueous mixtures of trehalose, a naturally occurring disaccharide of glucose, which shows an extraordinary bioprotective effectiveness against dehydration and freezing. The aim of the work is to furnish new results on the dynamics of the trehalose/water system on the nano- and picosecond scales. (orig.)

  6. Kinetics of ozone-phenol reaction in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, M.G.; Shambaugh, R.L.

    1982-01-01

    The kinetics of the reaction of ozone and phenol in aqueous medium was studied. The reaction was first order with respect to both ozone and phenol. The rate constant was found to increase with increase in the pH of the reaction mixture. Four different catalysts were examined for their effect on the rate of reaction. 30 refs.

  7. Development of tropine-salt aqueous two-phase systems and removal of hydrophilic ionic liquids from aqueous solution.

    Science.gov (United States)

    Wu, Haoran; Yao, Shun; Qian, Guofei; Song, Hang

    2016-08-26

    A novel aqueous two-phase systems (ATPS) composed of a small molecule organic compound tropine and an organic or inorganic salt aqueous solution has been developed for the first time. The phase behavior of tropine-salt ATPS was systemically investigated and the phase equilibrium data were measured in different temperatures and concentrations and correlated by the Merchuk equation with satisfactory results. The detection of the conductivity and particle size proved the formation of micelle in the process of forming tropine-salt ATPS. The separation application of the ATPS was assessed with the removal of hydrophilic benzothiazolium-based ionic liquids (ILs) from aqueous solution. The result showed that ILs were effectively extracted into the top tropine-rich phase. Finally, ILs in the top tropine-rich phase were further separated by the means of adsorption-desorption with DM301 macroporous resin and ethanol. The method of novel tropine-salt ATPS combined with adsorption-desorption is demonstrated a promising alternative thought and approach for the removal or recovery of hydrophilic compounds from aqueous media and also could provide a potential application for bio-separation.

  8. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    Science.gov (United States)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  9. Preparation of nanoparticles of Magnolia bark extract by rapid expansion from supercritical solution into aqueous solutions.

    Science.gov (United States)

    He, Shuai; Zhou, Benjie; Zhang, Shouyao; Lei, Zhengjie; Zhang, Zhongyi

    2011-01-01

    A rapid expansion from supercritical solution into aqueous solution (RESSAS) technology was presented for the micronization of Chinese medicinal material. Magnolia bark extract (MBE) obtained by supercritical carbon dioxide (scCO₂) extraction technology was chosen as the experimental material. RESSAS process produced 303.0 nm nanoparticles (size distribution, 243.6-320.5 nm), which was significantly smaller than the 55.3 µm particles (size distribution, 8.3-102.4 µm) prepared by conventional mechanical milling. The effect of process parameters, including extraction temperature (30 °C, 40 °C, 50 °C), extraction pressure (200, 250, 300 bar) and nozzle size (50, 100, 200 µm), on the size distribution of nanoparticles was investigated. The characteristics of nanoparticles and materials were also studied by scanning electron microscopy (SEM) and laser light scattering (LLS). This study demonstrates that RESSAS is applicable for preparing nanoparticles of MBE at low operating temperature; the process is simple without any residual solvent.

  10. Treatment of infectious skin defects or ulcers with electrolyzed strong acid aqueous solution.

    Science.gov (United States)

    Sekiya, S; Ohmori, K; Harii, K

    1997-01-01

    A chronic ulcer with an infection such as methicillin-resistant Staphylococcus aureus is hard to heal. Plastic and reconstructive surgeons often encounter such chronic ulcers that are resistant to surgical or various conservative treatments. We applied conservative treatment using an electrolyzed strong acid aqueous solution and obtained satisfactory results. The lesion was washed with the solution or soaked in a bowl of the solution for approximately 20 min twice a day. Fresh electrolyzed strong acid aqueous solution is unstable and should be stored in a cool, dark site in a sealed bottle. It should be used within a week after it has been produced. Here we report on 15 cases of infectious ulcers that were treated by electrolyzed strong acid aqueous solution. Of these cases, 7 patients were healed, 3 were granulated, and in 5, infection subsided. In most cases the lesion became less reddish and less edematous. Discharge or foul odor from the lesion was decreased. Electrolyzed strong acid aqueous solution was especially effective for treating a chronic refractory ulcer combined with diabetes melitus or peripheral circulatory insufficiency. This clinically applied therapy of electrolyzed strong acid aqueous solution was found to be effective so that this new therapeutic technique for ulcer treatment can now be conveniently utilized.

  11. Supercooling of aqueous dimethylsulfoxide solution at normal and high pressures: Evidence for the coexistence of phase-separated aqueous dimethylsulfoxide solutions of different water structures.

    Science.gov (United States)

    Kanno, H; Kajiwara, K; Miyata, K

    2010-05-21

    Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for T(H) (homogeneous ice nucleation temperature) and T(m) (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the T(H) curve for a DMSO solution of R=20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at P(c2)= approximately 200 MPa and at T(c2)temperature of SCP). The presence of two T(H) peaks for DMSO solutions (R=15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (Rtemperatures (different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.

  12. Enthalpy of solution of CO{sub 2} in aqueous solutions of 2-amino-2-methyl-1-propanol

    Energy Technology Data Exchange (ETDEWEB)

    Arcis, Hugues [Laboratoire de Thermodynamique des Solutions et des Polymeres, Universite Blaise Pascal, Clermont-Ferrand/CNRS, 63177 Aubiere (France); Rodier, Laurence [Laboratoire de Thermodynamique des Solutions et des Polymeres, Universite Blaise Pascal, Clermont-Ferrand/CNRS, 63177 Aubiere (France); Coxam, Jean-Yves [Laboratoire de Thermodynamique des Solutions et des Polymeres, Universite Blaise Pascal, Clermont-Ferrand/CNRS, 63177 Aubiere (France)]. E-mail: j-yves.coxam@univ-bpclermont.fr

    2007-06-15

    The enthalpies of solution of CO{sub 2} in aqueous solution of 2-amino-2-methyl-1-propanol (AMP) 15 wt% and 30 wt% were measured at 322.5 K and pressures range from (0.2 to 5) MPa using a flow calorimetric technique. The gas solubilities were simultaneously determined from the calorimetric data. The solubilities were compared to available literature values obtained by direct measurements. The experimental enthalpies of solution were compared to the values derived from the literature vapor liquid equilibrium data. This work provides calorimetric data that will be used later for the development of a thermodynamic model to predict both solubilities and enthalpies of solution of acid gases in aqueous amine solutions.

  13. Tetraethyl Orthosilicate Coated Hydroxyapatite Powders for Lead Ions Removal from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Rodica V. Ghita

    2014-01-01

    Full Text Available The goal of this study was to synthetize and characterize a porous material based on tetraethyl orthosilicate (TEOS coated hydroxyapatite (HApTh after removal experiments of Pb2+ ions from aqueous solutions. In order to study the morphology and composition, the samples obtained after removal experiments of Pb2+ ions from aqueous solution with the initial Pb2+ ion concentrations of the aqueous solutions were 0.1 g·L−1 (HApTh-50 and 0.9 g·L−1 (HApTh-450 have been investigated by scanning electron microscopy (SEM equipped with an energy dispersive X-ray spectrometer (EDS, Fourier transform infrared spectroscopy (FTIR, and transmission electron microscopy (TEM. Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into HApTh-50 and HApTh-450 due to the adsorption of Pb2+ ions followed by a cation exchange reaction. The obtained results show that the porous HApTh nanopowders could be used for Pb2+ ions removal from aqueous solutions.

  14. Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions

    Directory of Open Access Journals (Sweden)

    G. Ganbavale

    2014-05-01

    Full Text Available This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K. Water activity (aw at low temperatures (T is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB, differential scanning calorimetry (DSC, and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids and aqueous 2-(2-ethoxyethoxyethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for TTaw can be reversed at low temperatures and that linear extrapolations of high temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.

  15. Sorption Potentials of Waste Tyre for Some Heavy Metals (Pb Cd in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Austin Kanayo ASIAGWU

    2009-07-01

    Full Text Available An investigation into the adsorption potential of activated and inactivated waste tyre powders for some heavy metals (Pb2+ and Cd2+ in their aqueous solution has been studied. The result indicated that inactivated waste tyre is a good non-conventional adsorbent for the removal of Cd from aqueous solution. A total of 93.3% of Cadmium contents was removed. The inactivated waste type proved a good adsorbent for the removal of Pb2+ 5g of 500mm activated tyre removed over 86.66% of Pb2+ from solution.

  16. Modeling flavor release from aqueous sucrose solutions, using mass transfer and partition coefficients

    NARCIS (Netherlands)

    Nahon, D.F.; Harrison, M.; Roozen, J.P.

    2000-01-01

    The penetration theory of interfacial mass transfer was used to model flavor release from aqueous solutions containing different concentrations of sucrose. The mass transfer coefficient and the gas/solution partition coefficient are the main factors of the model influencing the release in time. Para

  17. Aqueous solutions of proline and NaCl studied by differential scanning calorimetry at subzero temperatures

    DEFF Research Database (Denmark)

    Rasmussen, Peter Have; Jørgensen, Bo; Nielsen, Jette

    1997-01-01

    The hydration properties of proline are studied by differential scanning calorimetry (DSC) in aqueous solutions during freezing to -60 degrees C and subsequent heating to +20 degrees C. The concentration of proline in the freeze concentrated solution was estimated to approximately 50 wt% (w/w) in...

  18. Direct evidence on the existence of [Mo132]Keplerate-type species in aqueous solution.

    Science.gov (United States)

    Roy, Soumyajit; Planken, Karel L; Kim, Robbert; Mandele, Dexx v d; Kegel, Willem K

    2007-10-15

    We demonstrate the existence of discrete single molecular [Mo(132)] Keplerate-type clusters in aqueous solution. Starting from a discrete spherical [Mo(132)] cluster, the formation of an open-basket-type [Mo(116)] defect structure is shown for the first time in solution using analytical ultracentrifugation sedimentation velocity experiments.

  19. Study on Thermosensitive Micellization of Dextran-g-PNIPAAm in Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    Dan ZHAO; Li Qun WANG; Ke Hua TU; Song Wei TAN

    2006-01-01

    The thermosensitive micellization of dextran-g-PNIPAAm in aqueous solutions has been investigated by fluorescence spectroscopy, dynamic light scattering and transmission electron microscope. The formed polymeric micelles showed different diameters of about 20 nm or 100nm, when the solution temperature was below or above the phase transition temperature.

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

    NARCIS (Netherlands)

    LAMMERS, G; STAMHUIS, EJ; BEENACKERS, AACM

    1993-01-01

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

  1. Comparison of cytotoxicity in vitro and irritation in vivo for aqueous and oily solutions of surfactants.

    Science.gov (United States)

    Czajkowska-Kośnik, Anna; Wolska, Eliza; Chorążewicz, Juliusz; Sznitowska, Małgorzata

    2015-01-01

    The in vivo model on rabbit eyes and the in vitro cytotoxicity on fibroblasts were used to compare irritation effect of aqueous and oily (Miglyol 812) solutions of surfactants. Tween 20, Tween 80 and Cremophor EL were tested in different concentrations (0.1, 1 or 5%) and the in vitro test demonstrated that surfactants in oil are less cytotoxic than in aqueous solutions. In the in vivo study, the aqueous solutions of surfactants were characterized as non-irritant while small changes in conjunctiva were observed after application the oily solutions of surfactants and the preparations were classified as slightly irritant, however this effect was similar when Miglyol was applied alone. In conclusion, it is reported that the MTT assay does not correlate well with the Draize scores.

  2. Morphological modifications of selenium by recrystallization of its aqueous complex solutions.

    Science.gov (United States)

    Batabyal, Sudip K; Basu, C; Das, A R; Sanyal, G S

    2006-07-01

    Recrystallization of elemental selenium (Se) from aqueous solution in presence of sodium sulphite (Na2SO3) and sodium sulphide (Na2S) acting as complexing agents has resulted in the formation of nano and microstructures of Se having five different morphological modifications. (1) An aqueous solution of sodium selenosulphate (Na2SO3Se) obtained by dissolving Se in Na2SO3 under refluxing condition yields hemispherical microcrystals. (2) The filtrate of the above reaction mixture on aging produces hexagonal prismatic microrods of Se. Addition of Na2SO3Se solution to formalin (HCHO) at room temperature and refluxing conditions generates (3) Se nanorods, and (4) spherical microcrystals, respectively. (5) Recrystallization of Se from aqueous solution of Na2S develops flower shaped microcrystals.

  3. Phase-transition and aggregation characteristics of a thermoresponsive dextran derivative in aqueous solutions.

    Science.gov (United States)

    Shi, Huan-Ying; Zhang, Li-Ming

    2006-10-16

    Grafting of poly(N-vinylcaprolactam) side chains onto a hydrophilic dextran backbone was found to provide the dextran with new, thermoresponsive properties in aqueous solutions. Depending on its solution concentration, the resulting dextran derivative could exhibit a temperature-induced phase-transition and critical transition temperature (T(c)). Different anions and cations of added salts, including five potassium salts and five alkali-metal chlorides, were observed to influence the T(c) value of its aqueous solution. Except for potassium iodide, all added salts were found to lower the T(c) value. The addition of the surfactant, cationic cetyltrimethylammonium bromide or anionic sodium dodecyl sulfate, resulted in an increase of the T(c) value. With the help of the Coomassie Brilliant Blue dye as a polarity probe, the formation of hydrophobic aggregates above the T(c) was revealed for this new dextran derivative in aqueous solution.

  4. Ab initio aqueous thermochemistry: application to the oxidation of hydroxylamine in nitric acid solution.

    Science.gov (United States)

    Ashcraft, Robert W; Raman, Sumathy; Green, William H

    2007-10-18

    Ab initio molecular orbital calculations were performed and thermochemical parameters estimated for 46 species involved in the oxidation of hydroxylamine in aqueous nitric acid solution. Solution-phase properties were estimated using the several levels of theory in Gaussian03 and using COSMOtherm. The use of computational chemistry calculations for the estimation of physical properties and constants in solution is addressed. The connection between the pseudochemical potential of Ben-Naim and the traditional standard state-based thermochemistry is shown, and the connection of these ideas to computational chemistry results is established. This theoretical framework provides a basis for the practical use of the solution-phase computational chemistry estimates for real systems, without the implicit assumptions that often hide the nuances of solution-phase thermochemistry. The effect of nonidealities and a method to account for them is also discussed. A method is presented for estimating the solvation enthalpy and entropy for dilute aqueous solutions based on the solvation free energy from the ab initio calculations. The accuracy of the estimated thermochemical parameters was determined through comparison with (i) enthalpies of formation in the gas phase and in solution, (ii) Henry's law data for aqueous solutions, and (iii) various reaction equilibria in aqueous solution. Typical mean absolute deviations (MAD) for the solvation free energy in room-temperature water appear to be ~1.5 kcal/mol for most methods investigated. The MAD for computed enthalpies of formation in solution was 1.5-3 kcal/mol, depending on the methodology employed and the type of species (ion, radical, closed-shell) being computed. This work provides a relatively simple and unambiguous approach that can be used to estimate the thermochemical parameters needed to build detailed ab initio kinetic models of systems in aqueous solution. Technical challenges that limit the accuracy of the estimates are

  5. The radiolysis of iodine in aqueous solutions containing methane

    Science.gov (United States)

    Paquette, Jean; Ford, Beverly L.

    The γ-radiolysis of iodine, iodine, iodate and periodate solutions containing methane has been investigated. Iodoalkanes are produced in these solutions upon irradiation. In the case of unbuffered iodine, iodate and periodate solutions at an initial concentration of 1.0 × 10 -4 mol dm -3, nearly all of the initial iodine is transformed into iodoalkanes after the absorption of a 4 kGy radiation dose. The yield of iodoalkanes is lower for iodine solutions and for iodide solutions buffered at neutral pH. It is concluded that the main reactions leading to the formation of iodoalkanes are CH 3+I 2→CH 3I+I and CH 3+I→CH 3I. In the case of iodate and periodate, these reactions could be preceeded by reactions involving the methyl radical and oxyiodine species: CH 3+IO x→CH 2O+HIO x-1.

  6. Reaction paths and equilibrium end-points in solid-solution aqueous-solution systems

    Science.gov (United States)

    Glynn, P.D.; Reardon, E.J.; Plummer, L.N.; Busenberg, E.

    1990-01-01

    Equations are presented describing equilibrium in binary solid-solution aqueous-solution (SSAS) systems after a dissolution, precipitation, or recrystallization process, as a function of the composition and relative proportion of the initial phases. Equilibrium phase diagrams incorporating the concept of stoichiometric saturation are used to interpret possible reaction paths and to demonstrate relations between stoichiometric saturation, primary saturation, and thermodynamic equilibrium states. The concept of stoichiometric saturation is found useful in interpreting and putting limits on dissolution pathways, but there currently is no basis for possible application of this concept to the prediction and/ or understanding of precipitation processes. Previously published dissolution experiments for (Ba, Sr)SO4 and (Sr, Ca)C??O3orth. solids are interpreted using equilibrium phase diagrams. These studies show that stoichiometric saturation can control, or at least influence, initial congruent dissolution pathways. The results for (Sr, Ca)CO3orth. solids reveal that stoichiometric saturation can also control the initial stages of incongruent dissolution, despite the intrinsic instability of some of the initial solids. In contrast, recrystallisation experiments in the highly soluble KCl-KBr-H2O system demonstrate equilibrium. The excess free energy of mixing calculated for K(Cl, Br) solids is closely modeled by the relation GE = ??KBr??KClRT[a0 + a1(2??KBr-1)], where a0 is 1.40 ?? 0.02, a1, is -0.08 ?? 0.03 at 25??C, and ??KBr and ??KCl are the mole fractions of KBr and KCl in the solids. The phase diagram constructed using this fit reveals an alyotropic maximum located at ??KBr = 0.676 and at a total solubility product, ???? = [K+]([Cl-] + [Br-]) = 15.35. ?? 1990.

  7. Synthesis of tyrocidine A and its analogues by spontaneous cyclization in aqueous solution.

    Science.gov (United States)

    Bu, Xianzhang; Wu, Xiaoming; Xie, Guiyang; Guo, Zhihong

    2002-08-22

    [reaction: see text] Head-to-tail cyclization of peptides is a multistep process involving tedious C-terminal activation and side chain protection. Here we report a facile, quantitative cyclization method in aqueous ammonia solution for the total syntheses of the cyclic decapeptide antibiotic Tyrocidine A and its analogues from their fully deprotected linear thioester precursors on a solid support. This novel aqueous method is conformation-dependent and may be applicable to syntheses of other natural cyclic peptides.

  8. Solubility of Carbon Dioxide and Hydrogen Sulfide in Aqueous N-Methyldiethanolamine Solutions

    OpenAIRE

    Huttenhuis, P. J. G.; Agrawal, N.J.; Versteeg, G. F.

    2009-01-01

    In this work, 72 new experimental solubility data points for H(2)S and CO(2) mixtures in aqueous N-methyldiethanol amine (MDEA) solutions at different methane partial pressures (up to 69 bara) are presented. They are correlated using an electrolyte equation of state (E-EOS) thermodynamic model. This model has already been used to estimate the CO(2) solubility in aqueous MDEA (Huttenhuis et al. Fluid Phase Equilib. 2008, 264, 99-112) and the H(2)S solubility in aqueous MDEA (Huttenhuis et al. ...

  9. First-principle based modeling of urea decomposition kinetics in aqueous solutions

    Science.gov (United States)

    Nicolle, André; Cagnina, Stefania; de Bruin, Theodorus

    2016-11-01

    This study aims at validating a multi-scale modeling methodology based on an implicit solvent model for urea thermal decomposition pathways in aqueous solutions. The influence of the number of cooperative water molecules on kinetics was highlighted. The obtained kinetic model is able to accurately reproduce urea decomposition in aqueous phase under a variety of experimental conditions from different research groups. The model also highlights the competition between HNCO desorption to gas phase and hydrolysis in aqueous phase, which may influence SCR depollution process operation.

  10. Radiation induced degradation of ketoprofen in dilute aqueous solution

    Science.gov (United States)

    Illés, Erzsébet; Takács, Erzsébet; Dombi, András; Gajda-Schrantz, Krisztina; Gonter, Katalin; Wojnárovits, László

    2012-09-01

    The intermediates and final products of ketoprofen degradation were investigated in 0.4 mmol dm-3 solution by pulse radiolysis and gamma radiolysis. For observation of final products UV-vis spectrophotometry and HPLC separation with diode array detection were used, and for identification MS was used. The reactions of •OH lead to hydroxycyclohexadienyl type radical intermediates, in their further reactions hydroxylated derivatives of ketoprofen form as final products. The hydrated electron is scavenged by the carbonyl oxygen and the electron adduct protonates to ketyl radical •OH is more effective in decomposing ketoprofen than hydrated electron. Chemical oxygen demand and total organic carbon content measurements on irradiated aerated solutions showed that using irradiation technology ketoprofen can be mineralised. The initial toxicity of the solution monitored by the Daphnia magna test steadily decreases with irradiation. Using 5 kGy dose no toxicity of the solution was detected with this test.

  11. Forces between Hydrophobic Solids in Concentrated Aqueous Salt Solution

    OpenAIRE

    Mastropietro, Dean J; Ducker, William A.

    2012-01-01

    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108 degrees. Thus, in 1 M salt solution, it is unnecessar...

  12. Volatile release from aqueous solutions under dynamic headspace dilution conditions.

    Science.gov (United States)

    Marin, M; Baek, I; Taylor, A J

    1999-11-01

    Static equilibrium was established between the gas phase (headspace) and an unstirred aqueous phase in a sealed vessel. The headspace was then diluted with air to mimic the situation when a container of food is opened and the volatiles are diluted by the surrounding air. Because this first volatile signal can influence overall flavor perception, the parameters controlling volatile release under these conditions are of interest. A mechanistic model was developed and validated experimentally. Release of compounds depended on the air-water partition coefficient (K(aw)) and the mass transport in both phases. For compounds with K(aw) values 10(-)(3), mass transport in the gas phase became significant and the Reynolds number played a role. Because release from packaged foods occurs at low Reynolds numbers, whereas most experiments are conducted at medium to high Reynolds numbers, the experimentally defined profile may not reflect the real situation.

  13. Direct Synthesis of Nanoceria in Aqueous Polyhydroxyl Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Karakoti, A. S.; Kuchibhatla, Satyanarayana V N T; Babu, K. S.; Seal, Sudipta

    2007-11-22

    Nanoceria has been shown to possess biomedical properties which have potential use in treatment of diseases caused by reactive oxygen species (ROS) like cancer. In the present work, stability and redox changes in nanoceria in the presence of polyhydroxyl groups such as glucose and dextran is reported. The effect of both acidic and basic medium on stability of nanoceria in the absence of buffer had been examined using UV-Visible spectroscopy and transmission electron microscopy. Experimental results showed that both dextran and glucose can extend the stability of nanoceria in basic medium without interfering with the redox chemistry. A comparison of aqueous and saccharides suspension in acid/base media undergoing redox transformation has been reported.

  14. Chemical and photochemical properties of chloroharmine derivatives in aqueous solutions.

    Science.gov (United States)

    Rasse-Suriani, Federico A O; Denofrio, M Paula; Yañuk, Juan G; Gonzalez, M Micaela; Wolcan, Ezequiel; Seifermann, Marco; Erra-Balsells, Rosa; Cabrerizo, Franco M

    2016-01-14

    Thermal and photochemical stability (Φ(R)), room temperature UV-vis absorption and fluorescence spectra, fluorescence quantum yields (Φ(F)) and lifetimes (τ(F)), quantum yields of hydrogen peroxide (Φ(H2O2)) and singlet oxygen (Φ(Δ)) production, and triplet lifetimes (τ(T)) have been obtained for the neutral and protonated forms of 6-chloroharmine, 8-chloroharmine and 6,8-dichloroharmine, in aqueous media. When it was possible, the effect of pH and oxygen concentration was evaluated. The nature of electronic transitions of protonated and neutral species of the three investigated chloroharmines was established using Time-Dependent Density Functional Theory (TD-DFT) calculations. The impact of all the foregoing observations on the biological role of the studied compounds is discussed.

  15. Electrochemical characteristics of dodecylbenzene sulfonic acid-doped polyaniline in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Choi, B.Y. [Korea Electr. Power Res. Inst., Taejon (Korea, Republic of). Power Utilization Group; Chung, I.J. [Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong Yusong, Taejon 305-701 (Korea, Republic of); Chun, J.H.; Ko, J.M. [Department of Industrial Chemistry, Taejon National University of Technology, 305-3, Samsung-2 dong, Dong-gu, Taejon 300-717 (Korea, Republic of)

    1999-02-26

    The electrochemical characteristics of the polyaniline (PAn) films doped with dodecylbenzene sulfonic acid (DBSA) were investigated in aqueous solutions by means of cyclic voltammetry. The PAn-DBSAs film showed a good electrochemical activity in a weak acid solution as well as in a strong acid solution due to the incorporation of small cation instead of DBSA trapped in the film for charge neutralization of polymer matrix. (orig.) 39 refs.

  16. The standard enthalpies of formation of crystalline N-(carboxymethyl)aspartic acid and its aqueous solutions

    Science.gov (United States)

    Lytkin, A. I.; Chernyavskaya, N. V.; Volkov, A. V.; Nikol'Skii, V. M.

    2007-07-01

    The energy of combustion of N-(carboxymethyl)aspartic acid (CMAA) was determined by bomb calorimetry in oxygen. The standard enthalpies of combustion and formation of crystalline N-(carboxymethyl)aspartic acid were calculated. The heat effects of solution of crystalline CMAA in water and a solution of sodium hydroxide were measured at 298.15 K by direct calorimetry. The standard enthalpies of formation of CMAA and its dissociation products in aqueous solution were determined.

  17. Adsorptive Removal of Acid Blue 80 Dye from Aqueous Solutions by Cu-TiO2

    OpenAIRE

    Ingrid Johanna Puentes-Cárdenas; Griselda Ma. Chávez-Camarillo; César Mateo Flores-Ortiz; María del Carmen Cristiani-Urbina; Alma Rosa Netzahuatl-Muñoz; Juan Carlos Salcedo-Reyes; Aura Marina Pedroza-Rodríguez; Eliseo Cristiani-Urbina

    2016-01-01

    The adsorption performance of a Cu-TiO2 composite for removing acid blue 80 (AB80) dye from aqueous solutions was investigated in terms of kinetics, equilibrium, and thermodynamics. The effect of operating variables, such as solution pH, initial dye concentration, contact time, and temperature, on AB80 adsorption was studied in batch experiments. AB80 adsorption increased with increasing contact time, initial dye concentration, and temperature and with decreasing solution pH. Modeling of adso...

  18. Changes in the color, chemical stability and antioxidant capacity of thermally treated anthocyanin aqueous solution over storage.

    Science.gov (United States)

    Sui, Xiaonan; Bary, Solène; Zhou, Weibiao

    2016-02-01

    Many anthocyanin-containing foods are thermally processed to ensure their safety, and stored for some time before being consumed. However, the combination of thermal processing and subsequent storage has a significant impact on anthocyanins. This study aimed to investigate the color, chemical stability, and antioxidant capacity of thermally treated anthocyanin aqueous solutions during storage at 4, 25, 45, and 65 °C, respectively. Anthocyanin aqueous solutions were thermally treated before storage. Results showed that the degradation rate of anthocyanins in aqueous solutions was much faster than those in real food. The color of the anthocyanin aqueous solutions changed dramatically during storage. The anthocyanin aqueous solutions stored at 4 °C showed the best chemical stability. Interestingly, the antioxidant capacity of the anthocyanin aqueous solutions stored at lower temperatures remained the same; however, the antioxidant capacity of those thermally treated at 120 or 140 °C and stored at 45 or 65 °C significantly decreased.

  19. Microwave-Based Microfluidic Sensor for Non-Destructive and Quantitative Glucose Monitoring in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Thomas Chretiennot

    2016-10-01

    Full Text Available This paper presents a reliable microwave and microfluidic miniature sensor dedicated to the measurement of glucose concentration in aqueous solution. The device; which is integrated with microtechnologies; is made of a bandstop filter implemented in a thin film microstrip technology combined with a fluidic microchannel. Glucose aqueous solutions have been characterized for concentration ranging from 80 g/L down to 0.3 g/L and are identified with the normalized insertion loss at optimal frequency. The sensitivity of the sensor has consequently been estimated at 7.6 × 10−3 dB/(g/L; together with the experimental uncertainty; the resolution of the sensor comes to 0.4 g/L. These results demonstrate the potentialities of such a sensor for the quantitative analysis of glucose in aqueous solution.

  20. Adsorption of Pb2+, Zn2+ and Ni2+ from Aqueous Solution by Helix aspera Shell

    Directory of Open Access Journals (Sweden)

    A. S. Ekop

    2009-01-01

    Full Text Available The adsorption capacity of Helix aspera shell for Pb2+, Zn2+ and Ni2+ has been studied. This shell has the potential of adsorbing Pb2+, Zn2+ and Ni2+ from aqueous solution. The adsorption potentials of Helix aspera shell is largely influenced by the ionic character of the ions and occurred according to the order Pb2+ > Ni2+ > Zn2+. The adsorption of Pb(II, Zn(II and Ni(II ions from aqueous solutions by Helix aspera shell is thermodynamically feasible and is consistent with the models of Langmuir and Freundlich adsorption isotherms. From the results of the study, the shell of Helix aspera is recommended for use in the removal of Pb2+, Zn2+ and Ni2+ from aqueous solution.

  1. Reversible Sol-Gel Transitions in Aqueous Solutions of N-Isopropylacrylamide Ionic Copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Krzyminski, Karol J.; Jasionowski, Marek; Gutowska, Anna

    2008-04-01

    Ionic copolymers of N-isopropylacrylamide (NIPA) exhibiting sol-gel transitions in aqueous solutions were investigated. The studies were aimed at understanding of the structure-property relationship in design of injectable, in situ forming gels for potential biomedical applications in delivery of therapeutics and tissue engineering. Aqueous solutions of NIPA ionic copolymers were found to flow freely at ambient temperatures and formed soft gels with controlled syneresis above 32°C, the lower critical solution temperature of NIPA. The sol-gel transitions and temperature dependent properties of the resulting gels were analyzed using dynamic rheometry, UV and IR spectrometry, and were found to be controlled by the molecular weight and composition of copolymers, ionization state of comonomers, and composition of aqueous solvent.

  2. Fluoresence quenching of riboflavin in aqueous solution by methionin and cystein

    Energy Technology Data Exchange (ETDEWEB)

    Droessler, P.; Holzer, W.; Penzkofer, A.; Hegemann, P

    2003-01-15

    The fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes of riboflavin in methanol, DMSO, water, and aqueous solutions of the sulphur atom containing amino acids methionin and cystein have been determined. In methanol, DMSO, and water (pH=4-8) only dynamic fluorescence reduction due to intersystem crossing and internal conversion is observed. In aqueous methionin solutions of pH=5.25-9 a pH independent static and dynamic fluorescence quenching occurs probably due to riboflavin anion-methionin cation pair formation. In aqueous cystein solutions (pH range from 4.15 to 9) the fluorescence quenching increases with rising pH due to cystein thiolate formation. The cystein thiol form present at low pH does not react with neutral riboflavin. Cystein thiolate present at high pH seems to react with neutral riboflavin causing riboflavin deprotonation (anion formation) by cystein thiolate reduction to the cystein thiol form.

  3. Fluoresence quenching of riboflavin in aqueous solution by methionin and cystein

    Science.gov (United States)

    Drössler, P.; Holzer, W.; Penzkofer, A.; Hegemann, P.

    2003-01-01

    The fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes of riboflavin in methanol, DMSO, water, and aqueous solutions of the sulphur atom containing amino acids methionin and cystein have been determined. In methanol, DMSO, and water (pH=4-8) only dynamic fluorescence reduction due to intersystem crossing and internal conversion is observed. In aqueous methionin solutions of pH=5.25-9 a pH independent static and dynamic fluorescence quenching occurs probably due to riboflavin anion-methionin cation pair formation. In aqueous cystein solutions (pH range from 4.15 to 9) the fluorescence quenching increases with rising pH due to cystein thiolate formation. The cystein thiol form present at low pH does not react with neutral riboflavin. Cystein thiolate present at high pH seems to react with neutral riboflavin causing riboflavin deprotonation (anion formation) by cystein thiolate reduction to the cystein thiol form.

  4. APPLICATION OF NONIONIC TEMPERATURE SENSITIVE HYDROGEL FOR CONCENTRATION OF PROTEIN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    SUN Yishi; QIU Zhiyong; HONG Yaoliang

    1992-01-01

    Six different N-alkyl substituted acrylamide nonionic hydrogels were prepared and their swelling characteristics were measured. Poly N-isopropyl acrylamide (PNIPA) and poly N-n-propylacrylamide (PNNPA) temperature sensitive hydrogels were chosen as the nonionic temperature sensitive hydrogels for concentration of very dilute aqueous protein solution. The separation properties of PNIPA and PNNPA hydrogels with different network dimensions were studied and the modification of the hydrogels was surveyed in order to decrease their surface adsorption of protein molecules. The experimental results of the concentration of BSA (Bovin serum albumin) dilute aqueous solution by hydroxylpropyl methacrylate (HPMA) copolymerized PNIPA hydrogel were given. The value and the limitation of concentration of dilute aqueous protein solution by this method was evaluated.

  5. Sorption of ochratoxin A from aqueous solutions using β-cyclodextrin-polyurethane polymer.

    Science.gov (United States)

    Appell, Michael; Jackson, Michael A

    2012-02-01

    The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1-10 μg·L(-1). These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples.

  6. Osmotic Second Virial Coefficients of Aqueous Solutions from Two-Component Equations of State.

    Science.gov (United States)

    Cerdeiriña, Claudio A; Widom, B

    2016-12-29

    Osmotic second virial coefficients in dilute aqueous solutions of small nonpolar solutes are calculated from three different two-component equations of state. The solutes are five noble gases, four diatomics, and six hydrocarbons in the range C1-C4. The equations of state are modified versions of the van der Waals, Redlich-Kwong, and Peng-Robinson equations, with an added hydrogen-bonding term for the solvent water. The parameters in the resulting equations of state are assigned so as to reproduce the experimental values and temperature dependence of the density, vapor pressure, and compressibility of the solvent, the gas-phase second virial coefficient of the pure solute, the solubility and partial molecular volume of the solute, and earlier estimates of the solutes' molecular radii. For all 15 solutes, the calculations are done for 298.15 K, whereas for CH4, C2H6, and C3H8 in particular, they are also done as functions of temperature over the full range 278.15-348.15 K. The calculated osmotic virial coefficients are compared with earlier calculations of these coefficients for these solutes and also with the results derived from earlier computer simulations of model aqueous solutions of methane. They are also compared with the experimental gas-phase second virial coefficients of the pure gaseous solutes to determine the effect the mediation of the solvent has on the resulting solute-solute interactions in the solution.

  7. Partition Equilibrium Between Charged Membrane and Single Electrolyte Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    徐铜文; 杨伟华; 何柄林

    2001-01-01

    Ionic partition equilibrium in charged membrane immersed in solution of single electrolyte with monovalence or multi-valence is systematically investigated and several expressions are established for determination of partition coefficients. On this basis, the effects of the ratio of membrane charge density to hulk electrolyte solution concentration, the charge sign and valence of electrolyte ions and the type of membrane on the partition equilibrium were analyzed and simulated with in chosen parameters. It is revealed that ion partition is not related solely withthe respective concentrations but also definitely with the concentration ratio of fixed group to bulk solution in addition to the charge sign and the valence. For a counterion, the partition coefficient increases with this ratio and the valence; while for a coion, the partition coefficient decreases with this ratio and the valence. The theoreticalcal culations were compared with the experimental data and a good agreement was observed.

  8. Partition Equilibrium Between Charged Membrane and Single Electrolyte Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ionic partition equilibrium in charged membrane immersed in solution of single electrolyte with mono valence or multi-valence is systematically investigated and several expressions are established for determination of partition coefficients. On this basis, the effects of the ratio of membrane charge density to bulk electrolyte solution concentration, the charge sign and valence of electrolyte ions and the type of membrane on the partition equilibrium were analyzed and simulated within chosen parameters. It is revealed that ion partition is not related solely with the respective concentrations but also definitely with the concentration ratio of fixed group to bulk solution in addition to the charge sign and the valence. For a counterion, the partition coefficient increases with this ratio and the valence; while for a coion, the partition coefficient decreases with this ratio and the valence. The theoretical calculations were compared with the experimental data and a good agreement was observed.

  9. The solubility of toluene in aqueous salt solutions.

    Science.gov (United States)

    Poulson, S; Harrington, R; Drever, J

    1999-03-01

    The solubility of toluene has been measured in distilled water, and in various inorganic salt solutions. Values of the Setschenow constant, K(S), which quantify toluene solubility versus salt concentration, have been determined for each salt. Values of K(S) are compared to the activity of water for the salt solutions. Data from this study, consistent with earlier data, suggests that the effects of salts upon toluene solubility are non-additive. This contrasts the additive behavior of inorganic salts upon the solubility of nonpolar organic compounds, such as benzene and naphthalene, reported in the literature. Specific interaction between slightly polar toluene and ions in solution is suggested as a possible explanation for the non-additive effect of salts on the solubility of toluene.

  10. RECOVERY OF THORIUM AND URANIUM VALUES FROM AQUEOUS SOLUTIONS

    Science.gov (United States)

    Calkins, G.D.

    1958-02-18

    This patent deals with the separation and recovery of uranium from monazite sand. After initial treatment of the sand with sodium hydroxide, a precipitate is obtuined which contains the uranium, thorium, rare earths and some phosphorus. This precipitate is then dissolved in nitric acid. The bulk of the rare earths are removed from thls soiution by adding aa excess of alkali carbonate, causing precipitation of the rare earths together with part of the thorium present. The solution still contains a considerable amount of thorium, some rare earths, and practically all of the uranium originally present. Thorium and rare earth values are readily precipitated from such solution, and the uranium values thus isolated, by the addition of an excess hydrogen peroxide. The pH value of the solution is preferably adjusted to at least 9 prior to the addition of the peroxide.

  11. Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

    Science.gov (United States)

    Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

    2016-08-01

    Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.

  12. Detecting the Biopolymer Behavior of Graphene Nanoribbons in Aqueous Solution

    Science.gov (United States)

    Wijeratne, Sithara S.; Penev, Evgeni S.; Lu, Wei; Li, Jingqiang; Duque, Amanda L.; Yakobson, Boris I.; Tour, James M.; Kiang, Ching-Hwa

    2016-01-01

    Graphene nanoribbons (GNR), can be prepared in bulk quantities for large-area applications by reducing the product from the lengthwise oxidative unzipping of multiwalled carbon nanotubes (MWNT). Recently, the biomaterials application of GNR has been explored, for example, in the pore to be used for DNA sequencing. Therefore, understanding the polymer behavior of GNR in solution is essential in predicting GNR interaction with biomaterials. Here, we report experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces. PMID:27503635

  13. Radiolysis of Reactive Azo Dyes in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Agustin N.M. Bagyo

    2004-07-01

    Full Text Available The effects of radiation on aerated reactive dye solutions i.e Cibacron Violet, Cibacron Orange and Cibacron Yellow solutions have been studied. Parameters analysis were the change of pH after radiation, the change of absorption, degradation products and effects of pH on the radiolysis. The uv-vis absorption of solutions were observed before and after irradiation. pH variation was done from pHs 3, 5, 7, 9 and 12. Irradiation was done at doses of 0, 2, 4, 6, 8 and 10 kGy with dose rate of 5 kGy/h and was determined by a Fricke dosimeter. HPLC with UV detector was used to analyze the degradation products. Oxalic acid was the main degradation product and small amount of succinic acid was also detected.

  14. Forces between hydrophobic solids in concentrated aqueous salt solution.

    Science.gov (United States)

    Mastropietro, Dean J; Ducker, William A

    2012-03-09

    Much research has focused on the discovery and description of long-ranged forces between hydrophobic solids immersed in water. Here we show that the force between high contact-angle solids in concentrated salt solution (1 M KCl) agrees very well with van der Waals forces calculated from Lifshitz theory for separations greater than 5 nm. The hydrophobic solids are octadecyltrichlorosilane-coated glass, with an advancing contact angle of 108°. Thus, in 1 M salt solution, it is unnecessary to invoke the presence of a hydrophobic force at separations greater than 5 nm. Through measurement in salt solution, we avoid the necessity of accounting for large electrostatic forces that frequently occur in pure water and may obscure resolution of other forces.

  15. Waste sizing solution as co-substrate for anaerobic decolourisation of textile dyeing wastewaters

    NARCIS (Netherlands)

    Bisschops, I.; Santos, dos A.B.; Spanjers, H.

    2005-01-01

    Dyeing wastewaters and residual size are textile factory waste streams that can be treated anaerobically. For successful anaerobic treatment of dyeing effluents, a co-substrate has to be added because of their low concentration of easily biodegradable compounds. Starch-based size contains easily bio

  16. Speciation modeling of ammonia and other major solutes in anaerobic digesters

    Science.gov (United States)

    Anaerobic digestion of high-nitrogen wastes can be inhibited by high concentrations of un-ionized ammonia, NH**3 (aq). Understanding the toxicity of NH**3 (aq) to anaerobic digestion requires an understanding of the mechanisms controlling its concentration. Previous work on ammonia toxicity in an...

  17. Electrogenerated chemiluminescence induced by sequential hot electron and hole injection into aqueous electrolyte solution

    Energy Technology Data Exchange (ETDEWEB)

    Salminen, Kalle; Kuosmanen, Päivi; Pusa, Matti [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Kulmala, Oskari [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 (Finland); Håkansson, Markus [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Kulmala, Sakari, E-mail: sakari.kulmala@aalto.fi [Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland)

    2016-03-17

    Hole injection into aqueous electrolyte solution is proposed to occur when oxide-coated aluminum electrode is anodically pulse-polarized by a voltage pulse train containing sufficiently high-voltage anodic pulses. The effects of anodic pulses are studied by using an aromatic Tb(III) chelate as a probe known to produce intensive hot electron-induced electrochemiluminescence (HECL) with plain cathodic pulses and preoxidized electrodes. The presently studied system allows injection of hot electrons and holes successively into aqueous electrolyte solutions and can be utilized in detecting electrochemiluminescent labels in fully aqueous solutions, and actually, the system is suggested to be quite close to a pulse radiolysis system providing hydrated electrons and hydroxyl radicals as the primary radicals in aqueous solution without the problems and hazards of ionizing radiation. The analytical power of the present excitation waveforms are that they allow detection of electrochemiluminescent labels at very low detection limits in bioaffinity assays such as in immunoassays or DNA probe assays. The two important properties of the present waveforms are: (i) they provide in situ oxidation of the electrode surface resulting in the desired oxide film thickness and (ii) they can provide one-electron oxidants for the system by hole injection either via F- and F{sup +}-center band of the oxide or by direct hole injection to valence band of water at highly anodic pulse amplitudes. - Highlights: • Hot electrons injected into aqueous electrolyte solution. • Generation of hydrated electrons. • Hole injection into aqueous electrolyte solution. • Generation of hydroxyl radicals.

  18. Selected specific rates of reactions of transients from water in aqueous solution. Hydrated electron, supplemental data. [Reactions with transients from water, with inorganic solutes, and with solutes

    Energy Technology Data Exchange (ETDEWEB)

    Ross, A.B.

    1975-06-01

    A compilation of rates of reactions of hydrated electrons with other transients and with organic and inorganic solutes in aqueous solution appeared in NSRDS-NBS 43, and covered the literature up to early 1971. This supplement includes additional rates which have been published through July 1973.

  19. Determination of ferrous and ferric iron in aqueous biological solutions

    Energy Technology Data Exchange (ETDEWEB)

    Pepper, S.E. [Earth and Environmental Sciences Division, Los Alamos National Laboratory, 1400 University Drive, Carlsbad, NM 88220 (United States); Borkowski, M., E-mail: marian@lanl.gov [Earth and Environmental Sciences Division, Los Alamos National Laboratory, 1400 University Drive, Carlsbad, NM 88220 (United States); Richmann, M.K.; Reed, D.T. [Earth and Environmental Sciences Division, Los Alamos National Laboratory, 1400 University Drive, Carlsbad, NM 88220 (United States)

    2010-03-24

    A solvent extraction method was employed to determine ferrous and ferric iron in aqueous samples. Fe{sup 3+} is selectively extracted into the organic phase (n-heptane) using HDEHP (bis(2-ethylhexyl) hydrogen phosphate) and is then stripped using a strong acid. After separation, both oxidation states and the total iron content were determined directly by ICP-MS analysis. This extraction method was refined to allow determination of both iron oxidation states in the presence of strong complexing ligands, such as citrate, NTA and EDTA. The accuracy of the method was verified by crosschecking using a refinement of the ferrozine assay. Presented results demonstrate the ability of the extraction method to work in a microbiological system in the presence of strong chelating agents following the bioreduction of Fe{sup 3+} by the Shewanella alga BrY. Based on the results we report, a robust approach was defined to separately analyze Fe{sup 3+} and Fe{sup 2+} under a wide range of potential scenarios in subsurface environments where radionuclide/metal contamination may coexist with strongly complexing organic contaminants.

  20. Pinning of phase separation of aqueous solution of hydroxypropylmethylcellulose by gelation

    Science.gov (United States)

    Kita, Rio; Kaku, Takeshi; Kubota, Kenji; Dobashi, Toshiaki

    1999-08-01

    Opalescence of the aqueous solution of hydroxypropylmethylcellulose (HPMC) induced by heating has been studied in terms of the phase diagram and the phase separation dynamics. The cloud point curve and the sol-to-gel transition curve intersected with each other at about 55 °C. Just above the cloud-point curve at which the spinodal curve has its minimum, a ring-like scattering pattern appeared corresponding to the spinodal decomposition. Temporal growth of the scattering function in the course of phase separation was studied by a time-resolved light scattering technique. The gelation pinned the phase separation (spinodal decomposition) of the aqueous HPMC solution.

  1. Adsorption of Pb2+, Zn2+ and Ni2+ from Aqueous Solution by Helix aspera Shell

    OpenAIRE

    A. S. Ekop; Eddy, N. O.

    2009-01-01

    The adsorption capacity of Helix aspera shell for Pb2+, Zn2+ and Ni2+ has been studied. This shell has the potential of adsorbing Pb2+, Zn2+ and Ni2+ from aqueous solution. The adsorption potentials of Helix aspera shell is largely influenced by the ionic character of the ions and occurred according to the order Pb2+ > Ni2+ > Zn2+. The adsorption of Pb(II), Zn(II) and Ni(II) ions from aqueous solutions by Helix aspera shell is thermodynamically feasible and is consistent with the models of La...

  2. Photocatalytic and photoelectrochemical oxidation mechanisms of methanol on TiO2 in aqueous solution

    Science.gov (United States)

    Ahmed, Amira Y.; Kandiel, Tarek A.; Ivanova, Irina; Bahnemann, Detlef

    2014-11-01

    Methanol is an available, small, and colorless molecule, which can be used for the photocatalytic activity evaluation without the sensitization problem associated with most dye molecules. Thus, TiO2 suspended in aqueous methanol solutions is commonly employed as a model test for the photocatalytic degradation of organic pollutants in aerobic system or for photocatalytic hydrogen production in absence of molecular oxygen. It is, hence, important to explore the mechanism of its photocatalytic and photoelectrochemical oxidation on TiO2 in aqueous solution. In this mini-review, the possible mechanisms for water and methanol oxidation on TiO2 will therefore be presented and discussed.

  3. Label-free monitoring of interaction between DNA and oxaliplatin in aqueous solution by terahertz spectroscopy

    Science.gov (United States)

    Wu, Xiaojun; E, Yiwen; Xu, Xinlong; Wang, Li

    2012-07-01

    We demonstrated the feasibility of applying terahertz time-domain spectroscopy (THz-TDS) to monitor the molecular reactions in aqueous solutions of anticancer drug oxaliplatin with λ-DNA and macrophages DNA. The reaction time dependent refractive index and absorption coefficient were extracted and analyzed. The reaction half-decaying time of about 4.0 h for λ-DNA and 12.9 h for M-DNA was established. The results suggest that the THz-TDS detection could be an effective label-free technique to sense the molecular reaction in aqueous solutions and could be very useful in biology, medicine, and pharmacy industry.

  4. Cooling and Freezing Behaviors of Aqueous Sodium Chloride Solution in a Closed Rectangular Container

    Science.gov (United States)

    Narumi, Akira; Kashiwagi, Takao; Nakane, Ichirou

    This paper investigates cooling and freezing behaviors of NaCl aqueous solution in a rectangular container equipped with horizontal partitions of micro porous film in order to determine the mechanisms of heat and mass transfer through cell wall for the purpose of freezing food. For comparison, experiments were performed using partitions of copper plate, no partition, and water. These processes were visualized and measured using real-time laser holographic interferometry. It was found that there was very little difference in the cooling process due to partitions, but that there were significant differences in freezing process when NaCl aqueous solution is used.

  5. Volumetric and Transport Properties of Aqueous NaB(OH)4 Solutions

    Institute of Scientific and Technical Information of China (English)

    周永全; 房春晖; 房艳; 朱发岩

    2013-01-01

    Density, pH, viscosity, conductivity and the Raman spectra of aqueous NaB(OH)4 solutions precisely measured as functions of concentration at different temperatures (293.15, 298.15, 303.15, 313.15 and 323.15 K) are presented. Polyborate distributions in aqueous NaB(OH)4 solution were calculated, covering all the concentration range, 4B(OH)− is the most dominant species, other polyborate anions are less than 5.0%. The volumetric and the transport properties were discussed in detail, both of these properties indicate that 4B(OH)− behaves as a struc-ture-disordered anion.

  6. Study of Penetration Kinetics of Sodium Hydroxide Aqueous Solution into Wood Samples

    Directory of Open Access Journals (Sweden)

    Lubomír Lapčík

    2013-12-01

    Full Text Available The kinetics of unidirectional penetration of NaOH aqueous solution into rectangular samples of wood oriented parallel to a stern axis were studied. Scots pine (Pinus sylvestris, European larch (Larix decidua, blackthorn (Prunus spinosa, white willow (Salix alba, and horse-chestnut wood (Aesculus hippocastanum were studied in this work. The time dependence of liquid incorporation was measured by the volumetric method as a change of total volume of coexisting liquid (NaOH/H2O phase. The total thickness of the swollen surface layer d and mean value of the apparent diffusion coefficient of aqueous NaOH solution at 22 °C were determined.

  7. Removal of biological stains from aqueous solution using a flow-through decontamination procedure.

    Science.gov (United States)

    Lunn, G; Klausmeyer, P J; Sansone, E B

    1994-01-01

    Chromatography columns filled with Amberlite XAD-16 were used to decontaminate, using a continuous flow-through procedure, aqueous solutions of the following biological stains: acridine orange, alcian blue 8GX, alizarin red S, azure A, azure B, brilliant blue G, brilliant blue R, Congo red, cresyl violet acetate, crystal violet, eosin B, eosin Y, erythrosin B, ethidium bromide, Giemsa stain, Janus green B, methylene blue, neutral red, nigrosin, orcein, propidium iodide, rose Bengal, safranine O, toluidine blue O, and trypan blue. Adsorption was most efficient for stains of lower molecular weight (removing stains from aqueous solution.

  8. Ludwig-Soret effect of non-ionic surfactant aqueous solution studied by beam deflection method

    Science.gov (United States)

    Maeda, Kousaku; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin

    2013-02-01

    We have studied the thermal diffusion of non-ionic surfactant aqueous solutions by a beam deflection method. The thermal diffusion of pentaethylene glycol monododecyl ether (C12E5) and hexaethylene glycol monododecyl ether (C12E6) is studied in the concentration range of 1.0-99.0 wt% and in the temperature range of 20.0-35.0 °C. A stable temperature gradient is applied to the solution, where solute molecules shift to the cold side of the solution for lowconcentration samples. The concentration dependence of the Soret coefficient ST of the C12E6 aqueous solution shows a sign inversion behavior. At all concentrations, the developed concentration gradient is proportionally related to the applied temperature gradient. The results confirm that the magnitude of ST has no temperature gradient dependence under the studied experimental conditions.

  9. Comparative analysis of the effect of pretreating aspen wood with aqueous and aqueous-organic solutions of sulfuric and nitric acid on its reactivity during enzymatic hydrolysis

    DEFF Research Database (Denmark)

    Dotsenko, Gleb; Osipov, D. O.; Zorov, I. N.;

    2016-01-01

    The effect of aspen wood pretreatment methods with the use of both aqueous solutions of sulfuric and nitric acids and aqueous-organic solutions (ethanol, butanol) of sulfuric acid (organosolv) on the limiting degree of conversion of this type of raw material into simple sugars during enzymatic...... of ground wood by 300–400%, compared to the initial raw material. Pretreatment with a 4.8% aqueous solution of nitric acid (125°C, 1.8 MPa, 10 min) is shown to be most effective, as it increases the reactivity of the ground aspen wood by more than 500%....

  10. Rheology of mixed alginate-hyaluronan aqueous solutions.

    Science.gov (United States)

    Travan, Andrea; Fiorentino, Simona; Grassi, Mario; Borgogna, Massimiliano; Marsich, Eleonora; Paoletti, Sergio; Donati, Ivan

    2015-01-01

    The present manuscript addresses the description of binary systems of hyaluronan (HA) and alginate (Alg) in semi-concentrated solution. The two polysaccharides were completely miscible in the entire range of relative weight fraction explored at a total polymer concentration of up to 3% (w/V). The rheological study encompassed steady flow and mechanical spectra for HA/Alg systems at different weight fractions with hyaluronan at different molecular weights. These extensive analyses allowed us to propose a model for the molecular arrangement in solution that envisages a mutual exclusion between the two polysaccharides even though a clear phase separation does not occur. This result may have profound implications when combinations of alginate and hyaluronan are proposed in the field of biomedical materials.

  11. Free energy landscapes of ion coordination in aqueous solution.

    Science.gov (United States)

    Brancato, Giuseppe; Barone, Vincenzo

    2011-11-10

    We show how the fruitful concept of free energy landscape, as invoked in the description of complex biological systems, can be rather easily extended to build up a simple and accurate picture about solvent coordination around ions. This may represent a revealing key element for the qualitative and quantitative physical-chemical interpretation of a large number of phenomena occurring in solution, such as water exchange mechanisms, ion mobility, solvation dynamics, ion channel selectivity, and so on. In particular, using a computational approach rooted into molecular dynamics simulations and enhanced sampling techniques, we show how the free energy landscapes of ion coordination in solution can be very easily and accurately obtained in a number of illustrative examples.

  12. Surfactant-free exfoliation of graphite in aqueous solutions.

    Science.gov (United States)

    Ricardo, Karen B; Sendecki, Anne; Liu, Haitao

    2014-03-14

    We report an ultrasound exfoliation of graphite in a weakly basic solution to produce multi-layer graphene dispersion. A unique feature of this process is that no surfactant was added to stabilize the exfoliated graphene in water. The concentration of the graphene dispersion prepared by this approach can be up to 0.02 mg mL(-1) and it was stable at room temperature for several months.

  13. Study of a Novel Method for the Thermolysis of Solutes in Aqueous Solution Using a Low Temperature Bubble Column Evaporator.

    Science.gov (United States)

    Shahid, Muhammad; Xue, Xinkai; Fan, Chao; Ninham, Barry W; Pashley, Richard M

    2015-06-25

    An enhanced thermal decomposition of chemical compounds in aqueous solution has been achieved at reduced solution temperatures. The technique exploits hitherto unrecognized properties of a bubble column evaporator (BCE). It offers better heat transfer efficiency than conventional heat transfer equipment. This is obtained via a continuous flow of hot, dry air bubbles of optimal (1-3 mm) size. Optimal bubble size is maintained by using the bubble coalescence inhibition property of some salts. This novel method is illustrated by a study of thermal decomposition of ammonium bicarbonate (NH4HCO3) and potassium persulfate (K2S2O8) in aqueous solutions. The decomposition occurs at significantly lower temperatures than those needed in bulk solution. The process appears to work via the continuous production of hot (e.g., 150 °C) dry air bubbles, which do not heat the solution significantly but produce a transient hot surface layer around each rising bubble. This causes the thermal decomposition of the solute. The decomposition occurs due to the effective collision of the solute with the surface of the hot bubbles. The new process could, for example, be applied to the regeneration of the ammonium bicarbonate draw solution used in forward osmosis.

  14. Experimental study of directional solidification of aqueous ammonium chloride solution

    Science.gov (United States)

    Chen, C. F.; Chen, Falin

    1991-01-01

    Directional solidification experiments have been carried out using the analog casting system of NH4Cl-H2O solution by cooling it from below with a constant-temperature surface ranging from -31.5 C to +11.9 C. The NH4Cl concentration was 26 percent in all solutions, with a liquidus temperature of 15 C. It was found that finger convection occurred in the fluid region just above the mushy layer in all experiments. Plume convection with associated chimneys in the mush occurred in experiments with bottom temperatures as high as +11.0 C. However, when the bottom temperature was raised to +11.9 C, no plume convection was observed, although finger convection continued as usual. A method has been devised to determine the porosity of the mush by computed tomography. Using the mean value of the porosity across the mush layer and the permeability calculated by the Kozeny-Carman relationship, the critical solute Rayleigh number across the mush layer for onset of plume convection was estimated to be between 200 and 250.

  15. Interfacial structures of acidic and basic aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Tian, C.; Ji, N.; Waychunas, G.; Shen, Y.R.

    2008-10-20

    Phase-sensitive sum-frequency vibrational spectroscopy was used to study water/vapor interfaces of HCl, HI, and NaOH solutions. The measured imaginary part of the surface spectral responses provided direct characterization of OH stretch vibrations and information about net polar orientations of water species contributing to different regions of the spectrum. We found clear evidence that hydronium ions prefer to emerge at interfaces. Their OH stretches contribute to the 'ice-like' band in the spectrum. Their charges create a positive surface field that tends to reorient water molecules more loosely bonded to the topmost water layer with oxygen toward the interface, and thus enhances significantly the 'liquid-like' band in the spectrum. Iodine ions in solution also like to appear at the interface and alter the positive surface field by forming a narrow double-charge layer with hydronium ions. In NaOH solution, the observed weak change of the 'liquid-like' band and disappearance of the 'ice-like' band in the spectrum indicates that OH{sup -} ions must also have excess at the interface. How they are incorporated in the interfacial water structure is however not clear.

  16. Desalination of aqueous solutions by LTA and MFI zeolite membranes using pervaporation method

    Directory of Open Access Journals (Sweden)

    A. Malekpour

    2011-12-01

    Full Text Available LTA and MFI zeolite membranes were hydrothermally grown on the surface of an α-alumina porous support. The synthesized membranes were used for removal of cationic and anionic species from aqueous solutions by the pervaporation method. The perfection of the membranes was improved by employing the multi-stage synthesis method. The membranes were characterized by XRD, SEM and IR methods. The membranes were initially evaluated by the pervaporation separation of water from aqueous 2-propanol mixtures. The separation factors obtained were 7081 and 105 for NaA and ZSM-5 membranes, respectively. The ability of membranes for desalination of some aqueous solutions containing I-, Cs+ and Sr2+ ions was examined in various conditions. These ionic species were chosen because of their importance in the nuclear sciences. Both membranes effectively removed (more than 99 wt% I-, Cs+ and Sr2+ from their singlesalt solutions (0.001mol dm-3 over a temperature range of 298-338 K. The effects of parameters such as time and temperature on the separation factors and fluxes were investigated. This work shows that, due to their excellent chemical, thermal and mechanical stability, the zeolitic membranes are useful for desalination of aqueous solutions and treating saline wastewaters by pervaporation. Therefore, this method has the ability to desalinate harsh environment solutions involving strong solvent and radioactive components.

  17. Removal of Cadmium and Lead Ions from Aqueous Solution by Nanocrystalline Magnetite Through Mechanochemical Activation

    Directory of Open Access Journals (Sweden)

    Mohsen Hosseinzadeh

    2016-12-01

    Full Text Available In this study, the removal of cadmium and lead ions from aqueous solution by nanocrystalline magnetite was investigated. The nanocrystalline magnetite was synthesized by mechanochemical activation of hematite in a high energy planetary mill in argon atmosphere for 45 hours. The ability of the synthesized nanocrystalline magnetite for removal of Cd(II and Pb(II from aqueous solutions was studied in a batch reactor under different experimental conditions with different pHs, contact times, initial metal ion concentrations and temperatures. The solution’s pH was found to be a key factor in the adsorption of heavy metal ions on Fe3O4. The optimum pH of the solution for adsorption of Cd(II and Pb(II from aqueous solutions was found to be 6.5 and 5.5, respectively. The best models to describe the kinetics and isotherms of single adsorption were both the pseudo first and second-order kinetic models and Langmuir models, respectively, indicating the monolayer chemisorption of Cd(II and Pb(II on Fe3O4 nanoparticles. Moreover, the thermodynamic parameters (i.e., ∆H°, ∆S°, ∆G° were evaluated which indicated that the adsorption was spontaneous and exothermic. The results suggested that the synthesized material (magnetite nanocrystalline particles may be used as effective and economic absorbent for removal of Cd(II and Pb(II from aqueous solutions.

  18. Electrosprayed molybdenum trioxide aqueous solution and its application in organic photovoltaic cells.

    Science.gov (United States)

    Suzuki, Katsumi; Fukuda, Takeshi; Liao, Yingjie

    2014-01-01

    A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer.

  19. Electrosprayed molybdenum trioxide aqueous solution and its application in organic photovoltaic cells.

    Directory of Open Access Journals (Sweden)

    Katsumi Suzuki

    Full Text Available A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer.

  20. [Photosensitized luminescence of singlet oxygen in aqueous solutions].

    Science.gov (United States)

    Krasnovskiĭ, A A

    1979-01-01

    The photoluminescence of singlet oxygen has been observed in air saturated solutions of riboflavin in D2O and mixtures of D2O and H2O. The excitation spectrum coincides with the absorption spectrum of the pigment, the emission maximum lies at 1275 nm. In D2O the quantum yield is approximately 1,2 x 10(-7). H2O quenches the luminescence. Analysis of quenching has shown that the quantum yield in H2O is less than in D2O by the factor of 20.

  1. Growth and Structure of Zirconium Hydrous Polymers in Aqueous Solutions

    Science.gov (United States)

    Singhal; Toth; Beaucage; Lin; Peterson

    1997-10-15

    Zirconium oxychloride solutions prepared at different pH were heated at elevated temperatures for various aging periods to gain an understanding of the growth mechanism and structure of zirconium hydrous polymers. Small angle X-ray scattering (SAXS) measurements were made on these solutions. It was observed that shape of clusters at the earlier stages of growth is close to a rod rather than a sheet as suggested earlier. The scattering data indicate that a rod-shaped primary particle is formed at pH 1.2, and on an increase in the pH, the primary particles become more branched. On aging more than 1250 min at 92°C, these primary particles form large aggregates while retaining the primary particle structure. These aggregates, which are mass fractal in nature, restructure while growing in size and eventually transform into dense particles. Scattering data in this study were not enough to determine a specific kinetic growth model of the aggregates because the scattering intensity at low q constantly changes with time during the restructuring process. Copyright 1997 Academic Press. Copyright 1997Academic Press

  2. Growth and structure of zirconium hydrous polymers in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Singhal, A. [Oak Ridge National Lab., TN (United States)]|[Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Toth, L.M.; Lin, J.S. [Oak Ridge National Lab., TN (United States); Beaucage, G. [Univ. of Cincinnati, OH (United States). Dept. of Materials Science and Engineering; Peterson, J. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry

    1997-10-15

    Zirconium oxychloride solutions prepared at different pH were heated at elevated temperatures for various aging periods to gain an understanding of the growth mechanism and structure of zirconium hydrous polymers. Small angle X-ray scattering (SAXS) measurements were made on these solutions. It was observed that shape of clusters at the earlier stages of growth is close to a rod rather than a sheet as suggested earlier. The scattering data indicate that a rod-shaped primary particle is formed at pH 1.2, and on an increase in the pH, the primary particles become more branched. On aging more than 1,250 min at 92 C, these primary particles form large aggregates while retaining the primary particle structure. These aggregates, which are mass fractal in nature, restructure while growing in size and eventually transform into dense particles. Scattering data in this study were not enough to determine a specific kinetic growth model of the aggregates because the scattering intensity at low q constantly changes with time during the restructuring process.

  3. Hydration and rotational diffusion of levoglucosan in aqueous solutions

    Science.gov (United States)

    Corezzi, S.; Sassi, P.; Paolantoni, M.; Comez, L.; Morresi, A.; Fioretto, D.

    2014-05-01

    Extended frequency range depolarized light scattering measurements of water-levoglucosan solutions are reported at different concentrations and temperatures to assess the effect of the presence and distribution of hydroxyl groups on the dynamics of hydration water. The anhydro bridge, reducing from five to three the number of hydroxyl groups with respect to glucose, considerably affects the hydration properties of levoglucosan with respect to those of mono and disaccharides. In particular, we find that the average retardation of water dynamics is ≈3-4, that is lower than ≈5-6 previously found in glucose, fructose, trehalose, and sucrose. Conversely, the average number of retarded water molecules around levoglucosan is 24, almost double that found in water-glucose mixtures. These results suggest that the ability of sugar molecules to form H-bonds through hydroxyl groups with surrounding water, while producing a more effective retardation, it drastically reduces the spatial extent of the perturbation on the H-bond network. In addition, the analysis of the concentration dependence of the hydration number reveals the aptitude of levoglucosan to produce large aggregates in solution. The analysis of shear viscosity and rotational diffusion time suggests a very short lifetime for these aggregates, typically faster than ≈20 ps.

  4. Dynamic contact angles in oil-aqueous polymer solutions.

    Science.gov (United States)

    Al-Shareef, Amer; Neogi, P; Bai, Baojun

    2017-01-25

    Polymer flooding is an important process in enhanced oil recovery. The displacement front is unstable when low viscosity brine displaces the heavy crude oil in the reservoir. Water-soluble polymers are added to the brine to increase its viscosity which stabilizes the displacement process. To analyze the displacement process at the micro-level, we have investigated the dynamic contact angles in silicone oil-polymer (polyethylene oxide) solution and for the first time. The dynamic contact angle is the apparent contact angle at the three-phase contact line which governs the capillary pressure, and thus is important for the displacement process. The data show no obvious signs of either shear thinning or elastic behavior, although for some systems with highest elastic effects some unexplained effects on dynamic contact angles are observed that correlate with elastic effects. Overall, dynamic contact angles are explained well using existing models for two Newtonian fluids, when the zero shear viscosity is used for the polymer solution.

  5. The decisive role of free water in determining homogenous ice nucleation behavior of aqueous solutions.

    Science.gov (United States)

    Wang, Qiang; Zhao, Lishan; Li, Chenxi; Cao, Zexian

    2016-05-26

    It is a challenging issue to quantitatively characterize how the solute and pressure affect the homogeneous ice nucleation in a supercooled solution. By measuring the glass transition behavior of solutions, a universal feature of water-content dependence of glass transition temperature is recognized, which can be used to quantify hydration water in solutions. The amount of free water can then be determined for water-rich solutions, whose mass fraction, Xf, is found to serve as a universal relevant parameter for characterizing the homogeneous ice nucleation temperature, the meting temperature of primary ice, and even the water activity of solutions of electrolytes and smaller organic molecules. Moreover, the effects of hydrated solute and pressure on ice nucleation is comparable, and the pressure, when properly scaled, can be incorporated into the universal parameter Xf. These results help establish the decisive role of free water in determining ice nucleation and other relevant properties of aqueous solutions.

  6. Electrocrystallizations of copper on glassy carbon in CuCl2 silica sol and aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    Yan Yan Feng; Min Gu; Yun Gui Du

    2012-01-01

    Electrocrystallizations of copper from both CuCl2 silica sol and aqueous solutions were studied by the chronoamperometry technique.It was found that current density contributions of the double-layer charging (iDL) in current-time transients (CTTs) from both of the solutions were large.An adsorption-nucleation based model was proposed to analyze quantitatively the CTTs,by which copper electrocrystallization mechanism was characterized as progressive nucleation with 3D growth (3DP) under diffusion control.The diffusion coefficient of copper ions and the AN∞ products in aqueous solutions were larger than that in silica sols,which indicated that copper nucleation was inhibited in sol solution.The large iDL may be resulted from the adsorption of chloride ions on the electrode surface.

  7. Probing Ionic Liquid Aqueous Solutions Using Temperature of Maximum Density Isotope Effects

    Directory of Open Access Journals (Sweden)

    Mohammad Tariq

    2013-03-01

    Full Text Available This work is a new development of an extensive research program that is investigating for the first time shifts in the temperature of maximum density (TMD of aqueous solutions caused by ionic liquid solutes. In the present case we have compared the shifts caused by three ionic liquid solutes with a common cation—1-ethyl-3-methylimidazolium coupled with acetate, ethylsulfate and tetracyanoborate anions—in normal and deuterated water solutions. The observed differences are discussed in terms of the nature of the corresponding anion-water interactions.

  8. A Concise Equation of State for Aqueous Solutions of Electrolytes Incorporating Thermodynamic Laws and Entropy

    Directory of Open Access Journals (Sweden)

    Raji Heyrovská

    2004-03-01

    Full Text Available Abstract: Recently, the author suggested a simple and composite equation of state by incorporating fundamental thermodynamic properties like heat capacities into her earlier concise equation of state for gases based on free volume and molecular association / dissociation. This work brings new results for aqueous solutions, based on the analogy of the equation of state for gases and solutions over wide ranges of pressures (for gases and concentrations (for solutions. The definitions of entropy and heat energy through the equation of state for gases, also holds for solutions.

  9. Ion spatial distributions at the liquid-vapor interface of aqueous potassium fluoride solutions.

    Science.gov (United States)

    Brown, Matthew A; D'Auria, Raffaella; Kuo, I-F William; Krisch, Maria J; Starr, David E; Bluhm, Hendrik; Tobias, Douglas J; Hemminger, John C

    2008-08-28

    X-Ray photoemission spectroscopy operating under ambient pressure conditions is used to probe ion distributions throughout the interfacial region of a free-flowing aqueous liquid micro-jet of 6 M potassium fluoride. Varying the energy of the ejected photoelectrons by carrying out experiments as a function of X-ray wavelength measures the composition of the aqueous-vapor interfacial region at various depths. The F(-) to K(+) atomic ratio is equal to unity throughout the interfacial region to a depth of 2 nm. The experimental ion profiles are compared with the results of a classical molecular dynamics simulation of a 6 M aqueous KF solution employing polarizable potentials. The experimental results are in qualitative agreement with the simulations when integrated over an exponentially decaying probe depth characteristic of an APPES experiment. First principles molecular dynamics simulations have been used to calculate the potential of mean force for moving a fluoride anion across the air-water interface. The results show that the fluoride anion is repelled from the interface, consistent with the depletion of F(-) at the interface revealed by the APPES experiment and polarizable force field-based molecular dynamics simulation. Together, the APPES and MD simulation data provide a detailed description of the aqueous-vapor interface of alkali fluoride systems. This work offers the first direct observation of the ion distribution at an aqueous potassium fluoride solution interface. The current experimental results are compared to those previously obtained for saturated solutions of KBr and KI to underscore the strong difference in surface propensity between soft/large and hard/small halide ions in aqueous solution.

  10. Sonochemical Decolorization of Methyl Orange in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    XING Tie-ling; Chu K.H.; CHEN Guo-qiang

    2006-01-01

    The sonochemical decolorization of Methylene Orange was studied using a 24 kHz Ultrasound device with a 1.4 cm diameter horn. pH, power density, the effects of pH and power density on decolorization were discussed. The combined effect of radiate time, the initial concentration of dyes and the addition of Fe2+ on the decolorization was studied using response surface methodology. The results showed that the factorial central composite design was successfully employed for experimental design and predication of the results. AtpH = 2.8, T=30℃, power denstity= 300 W/L and Fe2+ of 2 mg/L, the decolorization percentage of 5 mg/L dye solution reached 96% after 60 min ultrasound treatment.The rate of decolorization of the dye was greatly improved in the presence of Fe2+. The sonolysis of the dye followed first-order kinetics.

  11. Photodegradation of α-naphthaleneacetic acid in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Kinetic processes of α-naphthaleneacetic acid (NAA) photolysis were studied under different conditions. The results showed that the ultraviolet light was more effective than fluorescent light in promoting degradation, and the degradation of NAA under ultraviolet light followed the first order kinetics with the photolysis rate constant of 1.15 x 10-2 min-1 and half-life time (t1/2) of 60 min. Further, it was proved that the photolysis rate was higher in the presence of oxygen, titanium dioxide (TiO2), and low pH ( acidic solution). At last, two photolysis intermediates were identified by GC-MS and possible photolysis pathways were proposed.

  12. Removal of Acid Green 25 from Aqueous Solution by Adsorption

    Directory of Open Access Journals (Sweden)

    R. Parimalam

    2012-01-01

    Full Text Available The adsorptive removal of Acid Green 25 by Ananas Comosus (L Activated carbon was investigated in this study. The effects of initial dye concentration, contact time, pH and temperature were studied for the adsorption of Acid Green 25 in batch mode. At 100 mg/L of initial dye concentration the adsorbent removes 182.6 mg/g of dye from solution; it further increases on increasing the temperature. The calculated values of ∆G° indicate that the adsorption process is spontaneous, negative ∆H° indicate that the adsorption process is exothermic and the positive value of ∆S° indicates the increase in randomness. The rate of dye adsorption follows pseudo second order model with an r2 value of 0. 999. Standard adsorption isotherms were used to fit the experimental equilibrium data. The Langmuir, Freundlich, and Tempkin models are appropriate to explain the adsorption phenomenon with good fit.

  13. Degradation of DEET by ozonation in aqueous solution.

    Science.gov (United States)

    Tay, Kheng Soo; Rahman, Noorsaadah Abd; Abas, Mhd Radzi Bin

    2009-08-01

    This study was undertaken in order to understand the factors affecting the degradation of an insect repellent, N,N-diethyl-m-toluamide (DEET) by ozonation. Kinetic studies on DEET degradation were carried out under different operating conditions, such as varied ozone doses, pH values of solution, initial concentrations of DEET, and solution temperatures. The degradation of DEET by ozonation follows the pseudo-first-order kinetic model. The rate of DEET degradation increased exponentially with temperature in the range studied (20-50 degrees C) and in proportion with the dosage of ozone applied. The ozonation of DEET under different pH conditions in the presence of phosphate buffer occurred in two stages. During the first stage, the rate constant, k(obs), increased with increasing pH, whereas in the second stage, the rate constant, k(obs2), increased from pH 2.3 up to 9.9, however, it decreased when the pH value exceeded 9.9. In the case where buffers were not employed, the k(obs) were found to increase exponentially with pH from 2.5 to 9.2 and the ozonation was observed to occur in one stage. The rate of degradation decreased exponentially with the initial concentration of DEET. GC/MS analysis of the by-products from DEET degradation were identified to be N,N-diethyl-formamide, N,N-diethyl-4-methylpent-2-enamide, 4-methylhex-2-enedioic acid, N-ethyl-m-toluamide, N,N-diethyl-o-toluamide, N-acetyl-N-ethyl-m-toluamide, N-acetyl-N-ethyl-m-toluamide 2-(diethylamino)-1-m-tolylethanone and 2-(diethylcarbamoyl)-4-methylhex-2-enedioic acid. These by-products resulted from ozonation of the aliphatic chain as well as the aromatic ring of DEET during the degradation process.

  14. Hydrogen Evolution by Plasma Electrolysis in Aqueous Solution

    Science.gov (United States)

    Mizuno, Tadahiko; Akimoto, Tadashi; Azumi, Kazuhisa; Ohmori, Tadayoshi; Aoki, Yoshiaki; Takahashi, Akito

    2005-01-01

    Hydrogen has recently attracted attention as a possible solution to environmental and energy problems. If hydrogen should be considered an energy storage medium rather than a natural resource. However, free hydrogen does not exist on earth. Many techniques for obtaining hydrogen have been proposed. It can be reformulated from conventional hydrocarbon fuels, or obtained directly from water by electrolysis or high-temperature pyrolysis with a heat source such as a nuclear reactor. However, the efficiencies of these methods are low. The direct heating of water to sufficiently high temperatures for sustaining pyrolysis is very difficult. Pyrolysis occurs when the temperature exceeds 4000°C. Thus plasma electrolysis may be a better alternative, it is not only easier to achieve than direct heating, but also appears to produce more hydrogen than ordinary electrolysis, as predicted by Faraday’s laws, which is indirect evidence that it produces very high temperatures. We also observed large amounts of free oxygen generated at the cathode, which is further evidence of direct decomposition, rather than electrolytic decomposition. To achieve the continuous generation of hydrogen with efficiencies exceeding Faraday efficiency, it is necessary to control the surface conditions of the electrode, plasma electrolysis temperature, current density and input voltage. The minimum input voltage required induce the plasma state depends on the density and temperature of the solution, it was estimated as 120 V in this study. The lowest electrolyte temperature at which plasma forms is ˜75°C. We have observed as much as 80 times more hydrogen generated by plasma electrolysis than by conventional electrolysis at 300 V.

  15. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    Science.gov (United States)

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent.

  16. Study on Properties of Microemulsion AEO-9/Butanol/Cyclohexane/Salt Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    Qiu Guanming; Chen Yongjie; Tian Yiguang; Fang Li; Xiao Linjiu; Sun Yanbin

    2004-01-01

    The microemulsion AEO-9/butanol/cyclohexane/nitrate aqueous solution (or ammonium salt aqueous solution) was studied, which was used as 'micro-reactor' in preparing long afterglow phosphor materials SrAl2O4: Eu2+ ,Dy3+. The phase behavior of microemulsion was investigated. The radius of inner water droplet Rw and the change of standard free energy ΔG*o→i were obtained by means of dilution method and theoretical calculation. The result shows that with the increase of W/S, the area of microemulsion region decreases, Rw and ΔG*o→i increase and the microemulsion stability decreases. The structure change and formation area of microemulsion AEO-9/butanol/cyclohexane/nitrate aqueous solution ( or ammonium salt aqueous solution) were offered for the adoption of a synthesis method with newly high efficiency and utility. The particular size and its distribution theory gist, fluorescence life-span, and quenching concentration parameter data were expected. A new approach was explored for finding a new preparation method of rare earths afterglow materials and increasing luminescence intensity without crashing.

  17. A Large Conformational Change of a Bridged β-Cyclodextrin Dimer in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    Xiao Qi ZHENG; Yong Hui WANG; Qing Xiang GUO; Li YANG; You Cheng LIU

    2003-01-01

    A novel bridged β-CD dimer in which two β-cyclodextrins were linked by a naphthalene at positions 2 and 7 has been synthesized. 1H and 13CNMR measurements showed that a large change in the conformation of the dimer occurred in aqueous solution. The dimer interacted with methyl and ethyl orange to form stable inclusion complexes via "induced fit" mechanism.

  18. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  19. Nanoparticle detection in aqueous solutions using Raman and Laser Induced Breakdown Spectroscopy

    NARCIS (Netherlands)

    Sovago, M.; Buis, E.-J.; Sandtke, M.

    2013-01-01

    We show the chemical identification and quantification of the concentration and size of nanoparticle (NP) dispersions in aqueous solutions by using a combination of Raman Spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS). The two spectroscopic techniques are applied to demonstrate the NP

  20. Computer Simulation of the Process of Quenching Large-Size Parts in Water and Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    N.I.Kobasko; W.S.Morhuniuk; V.V.Dobrivecher; A.M.Weinov

    2004-01-01

    The article presents results of the computer simulation of quenching large-size parts in water and aqueous solutions. It has been shown that the main attention should be paid to eliminating film boiling and providing uniform cooling at the surface of the part to be quenched. Simplified formulas for calculating the optimal time of cooling large-size steel parts are presented.

  1. Plasmon interactions between gold nanoparticles in aqueous solution with controlled spatial separation

    DEFF Research Database (Denmark)

    Sendroiu, I.E.; Mertens, Stijn; Schiffrin, D.J.

    2006-01-01

    The effects of interparticle distance on the UV-visible absorption spectrum of gold nanocrystals aggregates in aqueous solution have been investigated. The aggregates were produced by ion-templated chelation of omega-mercaptocarboxylic acid ligands covalently attached to the nanoparticles surface...

  2. Removal of patulin from aqueous solutions by propylthiol functionalized SBA-15

    Science.gov (United States)

    The goal of this study is to investigate the ability of functionalized silicas to detoxify aqueous solutions including apple juice contaminated with the regulated mycotoxin patulin. Micelle templated silicas with a specific pore size were synthetically modified to possess propanethiol groups, a func...

  3. Performance of multiwall carbon nanotubes for removal phenol from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Mohamad Hadi Dehghani

    2013-05-01

    Conclusion: It is concluded that carbon nanotubes being effective in a wide range of pH, short time to reach equilibrium and the absence of competing ions on the absorption process can be used effectively in removing phenol from aqueous solution.

  4. Enzymatic removal of phenols from aqueous solutions by Coprinus cinereus peroxidase and hydrogen peroxide.

    Science.gov (United States)

    Kauffmann, C; Petersen, B R; Bjerrum, M J

    1999-07-30

    The fungal enzyme Coprinus cinereus peroxidase (CIP) can be used for the removal of toxic phenols from water. After treating aqueous solutions of phenols with CIP and H2O2 the phenols polymerized and precipitated. The decrease in phenol concentration was investigated for 10 different phenols. At neutral pH, the investigated phenols were in general removed with high efficiency.

  5. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions

    NARCIS (Netherlands)

    Avanti, Christina; Saluja, Vinay; Van Streun, Erwin L. P.; Frijlink, Henderik W.; Hinrichs, Wouter L. J.

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence Spectrosc

  6. Solubility of N2O in and density, viscosity, and surface tension of aqueous piperazine solutions

    NARCIS (Netherlands)

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

    2005-01-01

    The physical solubility of N2O in and the density and viscosity of aqueous piperazine solutions have been measured over a temperature range of (293.15 to 323.15) K for piperazine concentrations ranging from about (0.6 to 1.8) kmol·mr-3. Furthermore, the present study contains experimental surface t

  7. Deacidification of oils and fats of biological origine by aqueous solutions of tertiary amines*

    Directory of Open Access Journals (Sweden)

    Peter Siegfried

    2001-01-01

    Full Text Available Deacidification of triacylglycerols by extraction is investigated using aqueous solutions of amines as extractants. Tertiary amines with boiling points ranging between 100° and 170°C, such as 2-methylamino-diethanol, 2-dimethylamino-ethanol, 4-methylmorpholine, 1-dimethylamino-2-propanol etc. were found to be suitable substances. Especially the deacidification by aqueous solutions of 2-dimethylamino-ethanol (DMAE was amply investigated as it is used as an active agent in remedies. Amazingly gelatinous soap stocks are not formed, when the concentration of DMAE exceeds 20% if the free fatty acid content of the oil is below 15%. Two liquid phases are formed in systems composed of triacylglyceroles and aqueous solutions containing 20 to 80% DMAE. Palm oil containing 4.3 wt.% free fatty acids was mixed with an equal amount of an aqueous solution of 30 wt.% DMAE at 60°C. In equilibrium an extract containing 86 wt.% free fatty acids (solvents deducted and a raffinate of 0.09 wt.% free fatty acids are obtained. Loss of neutral oil being 0.7 wt.%.

  8. A Review on Chemical Effects in Aqueous Solution induced by Plasma with Glow Discharge

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Chemical effects in different aqueous solutions induced by plasma with glow dis charge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..

  9. The solubility of hydrogen sulfide in aqueous N-methyldiethanolamine solutions

    NARCIS (Netherlands)

    Huttenhuis, P.J.G.; Agrawal, N.J.; Versteeg, G.F.

    2008-01-01

    In this work the electrolyte equation of state as developed previously for the system MDEA-H2O-CO2-CH4 was further developed for the system MDEA-H2O-H2S-CH4. With this thermodynamic equilibrium model the total solubility of hydrogen sulfide and the speciation in aqueous solutions of N-methyldiethano

  10. Solubility of Carbon Dioxide and Hydrogen Sulfide in Aqueous N-Methyldiethanolamine Solutions

    NARCIS (Netherlands)

    Huttenhuis, P. J. G.; Agrawal, N. J.; Versteeg, G. F.

    2009-01-01

    In this work, 72 new experimental solubility data points for H(2)S and CO(2) mixtures in aqueous N-methyldiethanol amine (MDEA) solutions at different methane partial pressures (up to 69 bara) are presented. They are correlated using an electrolyte equation of state (E-EOS) thermodynamic model. This

  11. Thermodynamics of complexation in an aqueous solution of Tb(III) nitrate at 298 K

    Science.gov (United States)

    Lobacheva, O. L.; Berlinskii, I. V.; Dzhevaga, N. V.

    2017-01-01

    The pH of the formation of hydroxo complexes and hydrates in an aqueous solution of terbium Tb(III) is determined using combined means of potentiometric and conductometric titration. The stability constants of the hydroxo complexes, the products of hydroxide solubility, and the Gibbs energy of terbium hydroxo complex formation are calculated.

  12. Gelation Behavior of 5-Chloro-8-hydroxyquinoline, an Antituberculosis Agent in Aqueous Alcohol Solutions

    OpenAIRE

    Jukka Korpela; Hannu Salo; Erkki Kolehmainen

    2012-01-01

    It was shown that 5-chloro-8-hydroxyquinoline, an antituberculosis agent, gels aqueous alcohol solutions efficiently. Thermal stability and gel-to-sol transition temperature of 1% gel in CD3OD/D2O (2:1) was studied by 1H-NMR. Fibrous structures of four xerogels have been characterized by scanning electron microscope.

  13. Degradation/oxidation susceptibility of organic photovoltaic cells in aqueous solutions.

    Science.gov (United States)

    Habib, K; Husain, A; Al-Hazza, A

    2015-12-01

    A criterion of the degradation/oxidation susceptibility of organic photovoltaic (OPV) cells in aqueous solutions was proposed for the first time. The criterion was derived based on calculating the limit of the ratio value of the polarization resistance of an OPV cell in aqueous solution (Rp(s)) to the polarization resistance of the OPV cell in air (Rp(air)). In other words, the criterion lim(Rp(s)/Rp(air)) = 1 was applied to determine the degradation/oxidation of the OPV cell in the aqueous solution when Rp(air) became equal (increased) to Rp(s) as a function of time of the exposure of the OPV cell to the aqueous solution. This criterion was not only used to determine the degradation/oxidation of different OPV cells in a simulated operational environment but also it was used to determine the electrochemical behavior of OPV cells in deionized water and a polluted water with fine particles of sand. The values of Rp(s) were determined by the electrochemical impedance spectroscopy at low frequency. In addition, the criterion can be applied under diverse test conditions with a predetermined period of OPV operations.

  14. Experimental and modeling studies on the absorption of NO in aqueous ferrous EDTA solutions

    NARCIS (Netherlands)

    Gambardella, F; Alberts, MS; Winkelman, JGM; Heeres, EJ; Alberts, Michel S.; Heeres, H.J.

    2005-01-01

    This work describes an experimental and modeling study on an industrial relevant process (i.e., the absorption of NO in aqueous Fell(EDTA) solutions) to accurately determine the equilibrium constant of the reaction in the temperature range of 299-329 K. The experiments were carried out in a stirred

  15. STEREOCHEMICAL ASPECTS OF HYDRATION OF CARBOHYDRATES IN AQUEOUS-SOLUTIONS .3. DENSITY AND ULTRASOUND MEASUREMENTS

    NARCIS (Netherlands)

    GALEMA, SA; HOILAND, H

    1991-01-01

    Density and ultrasound measurements have been performed in aqueous solutions of pentoses, hexoses, methylpyranosides, and disaccharides as a function of molality of carbohydrate (0-0.3 mol kg-1). Partial molar volumes, partial molar isentropic compressibilities, and hydration numbers have been calcu

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

    NARCIS (Netherlands)

    GALEMA, SA; BLANDAMER, MJ; ENGBERTS, JBFN

    1992-01-01

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

  17. Radiolysis of aqueous solutions of ammonium bicarbonate over a large dose range

    DEFF Research Database (Denmark)

    Draganic, Z.D.; Negrón-Mendoza, A.; Sehested, K.;

    1991-01-01

    Oxygen-free aqueous solutions of 0.05 mol dm-3 ammonium and sodium bicarbonate were studied after receiving various doses of Co-60 gammas (0.01-400 kGy) or 0.5-20 Gy pulses of 10 Mev electrons. Formate and oxalate were found to be the main radiolytic products, in addition to trace amounts of form...

  18. General-base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

    NARCIS (Netherlands)

    Buurma, NJ; Blandamer, MJ; Engberts, JBFN; Buurma, Niklaas J.

    2003-01-01

    The reactivity of 1-benzoyl-3-phenyl-1,2,4-triazole (1a) was studied in the presence of a range of weak bases in aqueous solution. A change in mechanism is observed from general-base catalysed hydrolysis to nucleophilic substitution and general-base catalysed nucleophilic substitution. A slight tend

  19. A New Fluorescent Sensor for Transition Metal Ions in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new fluorescent sensor consisted of fluorenyl and dioxotetraaza unit, namely, 2,10-dimethyl-6-(9-fluorenyl)-1,4,8,11-tetraazaundencane-5,7-dione (L), was synthesized. It is a fluorescent sensor for transition metal ions in aqueous solution.

  20. 99TcO4(-): selective recognition and trapping in aqueous solution.

    Science.gov (United States)

    Alberto, Roger; Bergamaschi, Greta; Braband, Henrik; Fox, Thomas; Amendola, Valeria

    2012-09-24

    Too hot to handle: Unprecedented affinity and specificity for (99)TcO(4)(-) in aqueous solution was shown with the p-xylyl azacryptand in the hexaprotonated form. A crystal structure of the complex reveals how the anion fits within the cavity of the cage, and the formation of multiple H-bond interactions with protonated amino groups stabilize the adduct.

  1. Preparation of Ultrafine Cobalt Powder by Chemical Reduction in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Nanocrystalline cobalt powders have been prepared from aqueous solution by reducing their corresponding metal salts under suitable conditions. The experimental conditions have been studied in detail. X-ray powder diffraction patterns show that the cobalt powder is hexagonal crystallite. The average particle size of the ultrafine cobalt powder is 55 nm.

  2. Chemiluminescence in the reaction of ozone with 6-methyluracil in aqueous solutions

    Science.gov (United States)

    Zimin, Yu. S.; Khairullina, L. R.; Kutlugil'dina, G. G.; Mustafin, A. G.

    2015-12-01

    Chemiluminescence in the visible part of the spectrum during the oxidation of 6-methyluracil with ozone in aqueous solutions was found. The kinetics of variation of the luminescence intensity was studied in the temperature range 287-333 K, and the activation parameters of the process were determined.

  3. The Reaction between Iron(II) Iodide and Potassium Dichromate(VI) in Acidified Aqueous Solution

    Science.gov (United States)

    Talbot, Christopher

    2013-01-01

    This "Science note" teaching lesson explores the possible reaction between the ions in a reaction mixture consisting of iron(II) iodide and potassium dichromate(VI) in acidified aqueous solution. The electrode potentials will be used to deduce any spontaneous reactions under standard thermodynamic conditions (298 K, 1 bar (approximately…

  4. Relaxation of the Silver/Silver Iodide Electrode in Aqueous Solution

    NARCIS (Netherlands)

    Peverelli, K.J.

    1979-01-01

    The aim of this study is to detect and characterize relaxation processes on silver/silver iodide electrodes in aqueous electrolyte solution. The information obtained is to be used for an estimation of the consequences of similar processes on colloidal AgI particles during encounter.In chapter 1 a ge

  5. Poly(vinylpyridine) adsorbent for the removal of SIPA from its aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Wei Hua Tao; Ai Min Li; Chao Long; Hong Ming Qian

    2009-01-01

    Poly(vinylpyridine) WH-225 resin was prepared and characterized.Compared with the commercial hypercrosslinked adsorbent NDA-100 and macroporous adsorbent XAD-4 resins,the newly synthesized poly(vinylpyridine) WH-225 resin exhibited the highest adsorption capacity toward SIPA from aqueous solution.

  6. EXPERIMENTAL CHARACTERIZATION OF FLUOROCARBON-MODIFIED POLYACRYLAMIDE/SURFACTANT AQUEOUS SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Huai-tian Bu; Zhen-zhong Yang; Yun-xiang Zhang

    2003-01-01

    The interaction between surfactants and fluorocarbon-modified polyacrylamide (FC-PAM) in aqueous solutions was evaluated by theological means and fluorescence spectroscopy and was found to be strong regardless of the surfactant's nature. Two representative surfactants, anionic sodium dodecyl sulfate (SDS) and nonionic Triton X-100, were used. The origin of the interaction and its dependence on the surfactant concentration were discussed.

  7. Reentrant condensation of lysozyme: Implications for studying dynamics of lysozyme in aqueous solutions of lithium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Mamontov, Eugene [ORNL; O' Neill, Hugh Michael [ORNL

    2014-01-01

    Recent studies have outlined the use of eutectic solution of lithium chloride in water to study microscopic dynamics of lysozyme in an aqueous solvent that is remarkably similar to pure water in many respects, yet allows experiments over a wide temperature range without the solvent crystallization. The eutectic point in (H2O)R(LiCl) system corresponds to R 7.3, and it is of interest to investigate whether less concentrated aqueous solutions of LiCl could be employed in low-temperature studies of a solvated protein. We have investigated a range of concentrations of lysozyme and LiCl in aqueous solutions to identify systems that do not show phase separation and avoid solvent crystallization on cooling down. Compared to the lysozyme concentration in solution, the concentration of LiCl in the aqueous solvent plays the major role in determining systems suitable for low-temperature studies. We have observed interesting and rich phase behavior reminiscent of reentrant condensation of proteins.

  8. Blueshift of the silver plasmon band using controlled nanoparticle dissolution in aqueous solution

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo; Kneipp, Katrin

    2014-01-01

    In this work, we report the size-dependent blue shift of the silver nanoparticle plasmon band in aqueous solution by means of UV/VIS spectroscopy. An oxidative dissolution scheme allows a gradual decrease in the particle sizes by controlled oxidation during recording of the optical spectra. Hence...

  9. Gelation Behavior of 5-Chloro-8-hydroxyquinoline, an Antituberculosis Agent in Aqueous Alcohol Solutions

    Directory of Open Access Journals (Sweden)

    Jukka Korpela

    2012-09-01

    Full Text Available It was shown that 5-chloro-8-hydroxyquinoline, an antituberculosis agent, gels aqueous alcohol solutions efficiently. Thermal stability and gel-to-sol transition temperature of 1% gel in CD3OD/D2O (2:1 was studied by 1H-NMR. Fibrous structures of four xerogels have been characterized by scanning electron microscope.

  10. Hydrogen-Atom Attack on Methyl Viologen in Aqueous Solution Studied by Pulse Radiolysis

    DEFF Research Database (Denmark)

    Solar, S.; Solar, W.; Getoff, N.;

    1984-01-01

    Using hydrogen at high pressures of up to 150 bar (0.12 mol dm–3 H2) as an OH scavenger in aqueous MV2+ solutions (pH 1) it is possible to differentiate between two kinds of transient formed simultaneously by H-atom attack on methyl viologen. One of them is assigned to an H adduct on the N atom, ...

  11. Sorption of Ochratoxin A from aqueous solutions using beta-cyclodextrin-polyurethane polymer

    Science.gov (United States)

    The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions, including wine, was examined by batch rebinding assays and equilibrium sorption isotherms. The results were fit to two parameter models. Freundlich analysis of the sorption isotherm indicates the polyme...

  12. Removal of lead and zinc ions from aqueous solutions using clinoptilolite

    OpenAIRE

    Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Golomeov, Blagoj; Blažev, Krsto

    2014-01-01

    The removed of lead and zinc ions from synthetic aqueous solutions was performed using clinoptilolite. In order to determine the effectivity of clinoptilolite a series of experiments were performed under batch conditions from single ion solutions. Experiments were carried out at different initial ions concentration, different initial pH values and different adsorbent mass. The adsorption kinetics is reasonably fast. It means that in the first 20 min approximately 90% o...

  13. The Effect of Liquid Crystalline Structures on Antiseizure Properties of Aqueous Solutions of Ethoxylated Alcohols

    OpenAIRE

    2010-01-01

    Aqueous solutions of ethoxylated alcohols which form lyotropic liquid crystals at high concentrations (40–80%) were selected as model lubricating substances. Microscopic studies under polarized light and viscosity measurements were carried out in order to confirm the presence of liquid crystalline structures in the case of alcohol solutions with ethoxylation degrees of 3, 5, 7 and 10. Microscopic images and viscosity coefficient values characteristic of various mesophases were obtained. As ex...

  14. Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions

    CERN Document Server

    Lo Celso, F; Triolo, R; Triolo, A; Strunz, P; Bronstein, L; Zwanziger, J; Lin, J S

    2002-01-01

    Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported. (orig.)

  15. Removal of Organic Dyes from Aqueous Solutions with Surfactant-Modified Magnetic Nanoparticles

    OpenAIRE

    Wybieralska Katarzyna; Wajda Anna

    2014-01-01

    The paper presents the results of studies on the possibility of using magnetic nanoparticles modified with selected hydrophobic surfactants for model post-production water purification. Colloidal solutions of iron hydroxide (III) and iron oxide (II and III) were obtained and their particles were subjected to surface modification using surfactants. Thus obtained magnetic fluids were used as active agents in the process of removing selected organic dyes from their aqueous solutions. The effecti...

  16. Homotopy perturbation method for Ozone decomposition of the second order in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Ayati Z.

    2015-05-01

    Full Text Available In this article the problem of mass transfer of ozone of the second order from a gaseous phase into an aqueous phase has been studied. Homotopy perturbation method is employed to derive an analytical approximation to the solutions of the system of differential equations governing on the problem. Some parametric studies have been included. The effects of the temperature and hydroxyl ion reaction order to the solutions are illustrated by some plots

  17. Strengthening of the Coordination Shell by Counter Ions in Aqueous Th 4+ Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Atta-Fynn, Raymond; Bylaska, Eric J.; de Jong, Wibe A.

    2016-12-29

    The presence of counter ions in solutions containing highly charged metal cations can trigger processes such as ion-pair formation, hydrogen bond breakages and subsequent reformation, and ligand exchanges. In this work, it is shown how halide (Cl-, Br-) and perchlorate (ClO4-) anions affect the strength of the primary solvent coordination shells around Th4+ using explicit solvent and finite temperature ab initio molecular dynamics modeling methods. The 9-fold solvent geometry was found to be the most stable hydration structure in each aqueous solution. Relative to the dilute aqueous solution, the presence of the counter ions did not significantly alter the geometry of the primary hydration shell. However, the free energy analyses indicated that the 10-fold hydrated states were thermodynamically accessible in dilute and bromide aqueous solutions within 1 kcal/mol. Analysis of the results showed that the hydrogen bond lifetimes were longer and solvent exchange energy barriers were larger in solutions with counter ions in comparison with the solution with no counter ions. This implies that the presence of the counter ions induces a strengthening of the Th4+ hydration shell.

  18. Removal of silver(I) from aqueous solutions with low-rank Turkish coals

    Energy Technology Data Exchange (ETDEWEB)

    Karabakan, A.; Karabulut, S.; Denizli, A.; Yurum, Y. [University of Hacettepe, Ankara (Turkey). Dept. of Chemistry

    2004-07-01

    The removal of silver ions from aqueous solutions containing low-to-moderate levels of contamination using Turkish Beypazari low-rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coal surface provided adsorption sites for the removal of silver ions from solution via ion exchange. The equilibrium pH of the coal/solution mixture was shown to be the principal factor controlling the extent of recovery of Ag{sup +} ions from aqueous solutions. The optimum pH was measured as 4.0 and it was found that the maximum removal of silver from solution was achieved within 30 min. The maximum adsorption capacity of the Ag{sup +} ions was 1.87 mg/g coal. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that the use of low-rank coal was considerably more effective in the recovery Ag{sup +} ions from aqueous solutions. Higher amounts of adsorbed Ag{sup +} ions could be desorbed (up to 92%) using 25 mM EDTA. Low-rank Turkish coals were suitable for consecutive use for more than 10 cycles without significant loss of adsorption capacity.

  19. Experimental study of terrestrial plant litter interaction with aqueous solutions

    Science.gov (United States)

    Fraysse, F.; Pokrovsky, O. S.; Meunier, J.-D.

    2010-01-01

    Quantification of silicon and calcium recycling by plants is hampered by the lack of physico-chemical data on reactivity of plant litter in soil environments. We applied a laboratory experimental approach for determining the silica and calcium release rates from litter of typical temperate and boreal plants: pine ( Pinus laricio), birch ( Betula pubescens), larch ( Larix gmelinii), elm ( Ulmus laevis Pall.), tree fern ( Dicksonia squarrosa), and horsetail (Equisetum arvense) in 0.01 M NaCl solutions, pH of 2-10 and temperature equals to 5, 25 and 40 °C. Open system, mixed-flow reactors equipped with dialysis compartment and batch reactors were used. Comparative measurements were performed on intact larch needles and samples grounded during different time, sterilized or not and with addition or not of sodium azide in order to account for the effect of surface to mass ratio and possible microbiological activity on the litter dissolution rates. Litter degradation results suggest that the silica release rate is independent on dissolved organic carbon release (cell breakdown) which implies the presence of phytoliths in a pure "inorganic" pool not complexed with organic matter. Calcium and DOC are released at the very first stage of litter dissolution while Si concentration increases gradually suggesting the presence of Ca and Si in two different pools. The dry-weight normalized dissolution rate at circum-neutral pH range (approx. 1-10 μmol/g DW/day) is 2 orders of magnitude higher than the rates of Si release from common soil minerals (kaolinite, smectite, illite). Minimal Ca release rates evaluated from batch and mixed-flow reactors are comparable with those of most reactive soil minerals such as calcite and apatite, and several orders of magnitude higher than the dissolution rates of major rock-forming silicates (feldspars, pyroxenes). The activation energy for Si liberation from plant litter is approx. 50 kJ/mol which is comparable with that of surface

  20. Anodic oxide growth on Zr in neutral aqueous solution

    Indian Academy of Sciences (India)

    Z Tun; J J Noël; D W Shoesmith

    2008-10-01

    Anodization and subsequent cathodic reactions on a thin-film sample of Zr were studied with in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The NR results during anodization showed the originally 485 Å thick Zr film generally behaved similar to a bulk electrode in neutral solution. The anodization ratio measured at applied potentials increased in steps of 0.5 V was somewhat higher than the value determined by coulometry, while the Pilling Bedworth ratio is in good agreement with published data. Thickening of the oxide layer, accelerated immediately after each potential increase, gradually decreased over several hours, but remained non-zero even after ∼ 12 h. The thickened oxide eventually cracked when its thickness reached ∼ 120 Å, causing loss of passivation. Surprisingly, neither the anodization ratio nor the Pilling Bedworth ratio showed any discontinuity at the time of oxide cracking, and the EIS behaviour remained qualitatively as before. This observation is taken as the evidence that the cracked and intact regions of the electrode behave more or less independently as parallel electrodes. When the potential was eventually switched to cathodic polarity, NR shows, as expected, that the effects of oxide cracking were irreversible. However, the electrode resistance recovered partially suggesting the cracks were rapidly plugged with newly formed oxide.

  1. Foam separation of chromium (Ⅵ) from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    JIAO Cai-shan; DING Yan

    2009-01-01

    Removal of chromium (Ⅵ) dissolved in water by intermittent foam separation was implemented with cetyl trimethy-ammonium bromide as surfactant. The influence of various factors on removal efficiency was systematically studied. The removal efficiency has a maximum value near pH 4.0; thus, most experiments were carried out at pH 4.0. The orthogonal experiment was conducted to confirm the optimal operating parameters. The orthogonal experimental results show that when the liquid feed concentration is 10 mg/L, the pH value of feed solution is 4.00, air flow rates 0.9 L/min, surfactant dosage is 300 mg/L, the maximum removal efficiency of chromium (Ⅵ) reaches 97.80%, and condense multiple reaches 1711. The kinetic test indicates that the foam separation of chromium is a first-order process. The equivalent rate constant calculated from the slope is 0.406 4, and the equivalent rate equation is obtained.

  2. Phase Changes of Monosulfoaluminate in NaCl Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Seyoon Yoon

    2016-05-01

    Full Text Available Monosulfoaluminate (Ca4Al2(SO4(OH12∙6H2O plays an important role in anion binding in Portland cement by exchanging its original interlayer ions (SO42− and OH− with chloride ions. In this study, scanning transmission X-ray microscope (STXM, X-ray absorption near edge structure (XANES spectroscopy, and X-ray diffraction (XRD were used to investigate the phase change of monosulfoaluminate due to its interaction with chloride ions. Pure monosulfoaluminate was synthesized and its powder samples were suspended in 0, 0.1, 1, 3, and 5 M NaCl solutions for seven days. At low chloride concentrations, a partial dissolution of monosulfoaluminate formed ettringite, while, with increasing chloride content, the dissolution process was suppressed. As the NaCl concentration increased, the dominant mechanism of the phase change became ion exchange, resulting in direct phase transformation from monosulfoaluminate to Kuzel’s salt or Friedel’s salt. The phase assemblages of the NaCl-reacted samples were explored using thermodynamic calculations and least-square linear combination (LC fitting of measured XANES spectra. A comprehensive description of the phase change and its dominant mechanism are discussed.

  3. Surface tension of polytetrafluoroethylene and its wetting by aqueous solution of some surfactants and their mixtures

    Science.gov (United States)

    Mańko, Diana; Zdziennicka, Anna; Jańczuk, Bronisław

    2017-01-01

    Measurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-D-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension (γSV) as well as the Lifshitz-van der Waals component of the water surface tension (γWLW). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γSV and γWLW . It occured that by using the values of γSV , γWLW and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.

  4. Removal of dexamethasone from aqueous solution and hospital wastewater by electrocoagulation

    Energy Technology Data Exchange (ETDEWEB)

    Arsand, Daniel R., E-mail: danielarsand@pelotas.ifsul.edu.br [Chemistry Department, Federal University of Santa Maria, RS (Brazil); Kümmerer, Klaus, E-mail: klaus.kuemmerer@leuphana.de [Institute for Environmental Chemistry, Leuphana University Lüneburg (Germany); Martins, Ayrton F., E-mail: martins@quimica.ufsm.br [Chemistry Department, Federal University of Santa Maria, RS (Brazil)

    2013-01-15

    This study is concerned with the removal of the anti-inflammatory dexamethasone from aqueous solution and hospital wastewater by electrocoagulation. The variation of the toxicity during the electrocoagulation was also studied through experiments that were designed and optimized by means of response surface methodology. The coagulation efficiency was evaluated by measuring the dexamethasone concentration by high performance liquid chromatography coupled to a diode array detector. In addition, variation was evaluated through a Vibrio fischeri test. The results showed an increase in the removal of dexamethasone (up to 38.1%) with a rise of the current applied and a decrease of the inter-electrode distance, in aqueous solutions. The application to hospital effluent showed similar results for the removal of dexamethasone. The main effect of the electrocoagulation was that it removed colloids and reduced the organic load of the hospital wastewater. Regarding the current applied, the calculated energy efficiency was 100%. Without pH adjustment of the aqueous solution or hospital wastewater, the residual aluminum concentration always remained lower than 10 mg L{sup −1}, and, with adjustment (to pH 6.5), lower than 0.30 mg L{sup −1}, at the final stage. No toxicity variation was observed during the electrocoagulation process in aqueous solution, either in the presence or absence of dexamethasone. - Highlights: ► Removal of DEX and organic load from aqueous solution and hospital wastewater by EC ► Evaluation of the toxicity during the removal of DEX by EC ► Suggestion of the EC process as a pretreatment for subsequent processes.

  5. Effect of sodium tetraborate (borax) on the thermal properties of frozen aqueous sugar and polyol solutions.

    Science.gov (United States)

    Izutsu, Ken-ichi; Rimando, Annie; Aoyagi, Nobuo; Kojima, Shigeo

    2003-06-01

    The effect of sodium tetraborate (Na(2)B(4)O(7), borax) on the thermal property of frozen aqueous sugar and polyol solutions was studied through thermal analysis. Addition of borax raised the thermal transition temperature (glass transition temperature of maximally freeze-concentrated solutes; T(g)') of frozen sucrose solutions depending on the borax/sucrose concentration ratios. Changes in the T(g)' of frozen mono- and disaccharide solutions suggested various forms of complexes, including those of a borate ion and two saccharide molecules. Borax exerted the maximum effect to raise the oligosaccharide and dextran T(g)'s at borax/saccharide molar ratios of approximately 1-2 (maltose and maltooligosaccharides), 2 (dextran 1060), 5 (dextran 4900), and 10 (dextran 10200). Further addition of borax lowered T(g)'s of the saccharide solutions. Borax also raised T(g) and T(g)' temperatures of frozen aqueous glycerol solutions. The decreased solute mobility in frozen solutions by the borate-polyol complexes suggested higher collapse temperature in the freeze-drying process and improved stability of biological systems in frozen solutions.

  6. Assessing 16-Year-Old Students' Understanding of Aqueous Solution at Submicroscopic Level

    Science.gov (United States)

    Devetak, Iztok; Vogrinc, Janez; Glažar, Saša Aleksij

    2009-03-01

    Submicrorepresentations (SMR) could be an important element, not only for explaining the experimental observations to students, but also in the process of evaluating students’ knowledge and identifying their chemical misconceptions. This study investigated the level of students’ understanding of the solution concentration and the process of dissolving ionic and molecular crystals at particulate level, and identifies possible misconceptions about this process. Altogether 408 secondary school students (average age 16.3) participated in the study. The test of chemical knowledge was applied and the analysis of four selected problems related to drawing SMRs in solution chemistry is presented. Selected students were also interviewed in order to gain more detailed data about their way of solving problems comprised in the knowledge test. The average achievement on solution chemistry items was only 43%. It can be concluded from the results that students have different misconceptions about arrangements of solute particles in the solution and presentation of its concentration at particulate level. Students show quite low achievement scores on the problem regarding drawing the SMR of ionic substance aqueous solution (7.6% correct answers) and even lower ones on the problem regarding drawing the SMR of diluted and saturated aqueous solutions of molecular crystal (no completely correct answers). It can be also concluded that many different misconceptions concerning the particulate level of basic solution chemistry concepts can be identified. In the conclusion some implications for teaching to reach a higher level of understanding of solution chemistry are proposed.

  7. Electrostatic properties of aqueous interfaces probed by small solutes

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael A.; Schweighofer, Karl

    1999-11-01

    The excess chemical potentials of methane and its four fluorinated derivatives across the water-hexane, water-octanol, water-glycerol 1-monooleate and water-1-palmitoyl 2-oleoyl sn-glycero 3-phosphatidylcholine (POPC) interfaces are calculated using the particle insertion method. In all cases, the polar species exhibit interfacial minima indicating that these molecules tend to accumulate in the interfacial region, while the non-polar molecules exhibit no such minimum. The excess chemical potentials are further partitioned into electrostatic and non-electrostatic terms. For polar molecules, the electrostatic term changes nearly linearly over the distance of approximately 10 Å in the interfacial region and appears to depend only weakly on the nature of the interface. Solute molecules are not oriented isotropically at the interface, but tend to align themselves with the excess electric field created by the anisotropic interfacial environment. Using dipoles in a cavity as models, it is further shown that, in the water-POPC system, the electrostatic term changes with the size of the dipole according to the predictions of linear response theory. This approximation does not work as well for the other interfacial systems investigated. This may be an artifact due to the neglect of long-range effects in those simulations. The non-electrostatic term, dominated by the reversible work of cavity formation, shows interfacially induced structure. In particular, it is responsible for a maximum of the excess chemical potential on the dense, water side of the water-POPC interface. The results of this study provide guidance to developing simple but accurate implicit models of interfacial systems.

  8. UV Spectral Analysis of the Chemical Modification and Photolysis of Acetylacetone Modified Alumina Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    Chengbin JING; Xiujian ZHAO; Haizheng TAO; Xina WANG; Aiyun LIU

    2004-01-01

    Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and peptizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red-shift due to the formation of the six-membered ring of the complex between alumina and acetylacetone in the aqueous solution. It was also found that the chemical modification can be dissociated by the UV irradiation with a wavelength shorter than 286 nm as a result of the excitation of π-π* transition in the complex.

  9. The solubility of hydrogen sulfide in aqueous N-methyldiethanolamine solutions

    OpenAIRE

    Huttenhuis, P. J. G.; Agrawal, N.J.; Versteeg, G. F.

    2008-01-01

    In this work the electrolyte equation of state as developed previously for the system MDEA-H2O-CO2-CH4 was further developed for the system MDEA-H2O-H2S-CH4. With this thermodynamic equilibrium model the total solubility of hydrogen sulfide and the speciation in aqueous solutions of N-methyldiethanolamine can be described quantitatively. The model results were compared to experimental H2S solubility data in aqueous MDEA in absence and presence of methane respectively. The application of equat...

  10. The effect of β-cyclodextrin in the photochemical stability of propranolol hydrochloride in aqueous solution

    Directory of Open Access Journals (Sweden)

    Tathiane Lilian Ansolin

    2014-04-01

    Full Text Available The degradation of propranolol hydrochloride (1-isopropylamino-3-(naphthoxy-2-propranolol in an aqueous solution was analyzed when irradiated by light UV, with and without β-cyclodextrin. There was an increase in the compound´s photostability in nanocavity when compared with the drug without the cyclodextrins’ cavity. First order kinetic model was employed for the degradation of propranolol in aqueous media and in cyclodextrins’ cavity. The kinetic parameter was obtained by the drug´s absorption and electronic fluorescence. As a rule, encapsulation of propranolol in β-cyclodextrin decreases photodegradation speed by 53%.

  11. An efficient petiole-feeding bioassay for introducing aqueous solutions into dicotyledonous plants.

    Science.gov (United States)

    Lin, Yu-Hsiang; Lin, Meng-Han; Gresshoff, Peter M; Ferguson, Brett J

    2011-01-01

    Introducing bioactive molecules into plants helps establish their roles in plant growth and development. Here we describe a simple and effective petiole-feeding protocol to introduce aqueous solutions into the vascular stream and apoplast of dicotyledonous plants. This 'intravenous feeding' procedure has wide applicability to plant physiology, specifically with regard to the analysis of source-sink allocations, long-distance signaling, hormone biology and overall plant development. In comparison with existing methods, this technique allows the continuous feeding of aqueous solutions into plants without the need for constant monitoring. Findings are provided from experiments using soybean plants fed with a range of aqueous solutions containing tracer dyes, small metabolites, radiolabeled chemicals and biologically active plant extracts controlling nodulation. Typically, feeding experiments consist of (i) generating samples to feed (extracts, solutions and so on); (ii) growing recipient plants; (iii) setting up the feeding apparatus; and (iv) feeding sample solutions into the recipient plants. When the plants are ready, the feeding procedure can take 1-3 h to set up depending on the size of experiment (not including preparation of materials). The petiole-feeding technique also works with other plant species, including tomato, chili pepper and cabbage plants, as demonstrated here.

  12. Radiosterilization of drugs in aqueous solutions may be achieved by the use of radioprotective excipients.

    Science.gov (United States)

    Maquille, Aubert; Jiwan, Jean-Louis Habib; Tilquin, Bernard

    2008-02-12

    The aim of this study was to assess the feasibility of radiosterilization of drugs aqueous solutions and to evaluate the effects of some additives, such as mannitol, nicotinamide and pyridoxine, which might protect the drug from degradation. Metoclopramide was selected as a model drug. The structures of the degradation products were determined to gain insight on the radiolysis mechanisms in aqueous solution in order to design strategies to lower the drug degradation. Metoclopramide hydrochloride aqueous solutions with and without excipients were irradiated either with gamma rays or high-energy electrons. HPLC-DAD was used to measure the loss of chemical potency and to quantify the degradation products which were also characterized by LC-APCI-MS-MS. Metoclopramide recovery for gamma and electron beam-irradiated solutions containing either mannitol, pyridoxine or nicotinamide meets the pharmacopoeial specifications for metoclopramide content up to a 15 kGy irradiation so that metoclopramide solutions containing these excipients might be radiosterilized at 15 kGy either with gamma rays or high-energy electrons. Structures are proposed for the majority of radiolysis products. Similar radiolysis products were detected for gamma and electron beam irradiations but the chromatographic profiles were different (differences in the distribution of radiolysis products).

  13. Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

    Science.gov (United States)

    Wang, Le; Mu, Wen-ning; Shen, Hong-tao; Liu, Shao-ming; Zhai, Yu-chun

    2015-05-01

    A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaCl2 aqueous solution, liquid-to-solid (L/S) ratio, leaching temperature, and leaching time, were investigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaCl2 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7:1, a leaching temperature of 80°C, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

  14. Studies on the Solute Solvent Interaction of Nimesulide in Aqueous Solutions of Hydrotropic Agents at Different Temperatures

    OpenAIRE

    Solanki, Chandravir S.; Sushree Tripathy; Minaketan Tripathy; Dash, Upendra N.

    2010-01-01

    The present study deals with experiments so as to highlight the solute (drug nimesulide) - solvent(water) interactions and related modifications in case of the presence of hydrotropic agents at different temperatures T(=298.15 to 313.15)K. Density and viscosity values of nimesulide have been determined in water in (0.1, 0.2, 0.4, 0.6, 0.8, 1 and 2) mol dm-3 aqueous solutions of hydrotropic agents (sodium benzoate, sodium salicylate, sodium bromide and nicotinamide) at temperatures 298.15, 303...

  15. Simulations of mean ionic activity coefficients and solubilities in aqueous electrolyte solutions

    Science.gov (United States)

    Panagiotopoulos, Athanassios

    Aqueous electrolyte solutions play an important role in industrial, geochemical and biological applications. The mean ionic activity coefficients quantify the deviation of salt chemical potential from ideal solution behavior; experimental measurements are available for many salts over broad ranges of concentration and temperature, but there have been practically no prior simulation results, because if sampling difficulties for explicit-solvent electrolyte solutions. We have developed a new approach for determination of activity coefficients of aqueous electrolytes. Common fixed-point-charge models for water and ions are unable to reproduce simultaneously activity coefficients and solubilities. Polarizable models perform better, but still predict an incorrect temperature dependence of these properties. Work supported by the U.S. Department of Energy, Office of Basic Energy Science.

  16. Water rotational jump driven large amplitude molecular motions of nitrate ions in aqueous potassium nitrate solution

    CERN Document Server

    Banerjee, Puja; Bagchi, Biman

    2016-01-01

    Molecular dynamics simulations of aqueous potassium nitrate solution reveal a highly complex rotational dynamics of nitrate ions where, superimposed on the expected continuous Brownian motion, are large amplitude angular jumps that are coupled to and at least partly driven by similar large amplitude jump motions in water molecules which are associated with change in the hydrogen bonded water molecule. These jumps contribute significantly to rotational and translational motions of these ions. We explore the detailed mechanism of these correlated (or, coupled) jumps and introduce a new time correlation function to decompose the coupled orientational- jump dynamics of solvent and solute in the aqueous electrolytic solution. Time correlation function provides for the unequivocal determination of the time constant involved in orientational dynamics originating from making and breaking of hydrogen bonds. We discover two distinct mechanisms-both are coupled to density fluctuation but are of different types.

  17. Removal of Cr(VI from aqueous solution using Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae

    Directory of Open Access Journals (Sweden)

    P. Sethuraman,

    2010-06-01

    Full Text Available The objective of this study is to investigate the removal efficiency of Cr(VI by Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae from aqueous solution under different process conditions. Batch mode experiments were carried out as a function of solution pH, biosorbent dosage, Cr(VI concentration and contact time.The FT-IR spectra and SEM analysis of the biosorbent were recorded to analyse the number and position of the functional groups available for the binding of Cr(VI ions and to study the morphology of biosorbent. The batch isothermal equilibrium data were analyzed with Freundlich and Langmuir isotherm models. The kinetic models were examined with pseudo first order and pseudo second order kinetics. The results revealed that the Cr(VI is considerably adsorbed on bacterial biomass and it could be an economical method for the removal of Cr(VI from aqueous solution.

  18. Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Minbiao; /SLAC, PULSE /Stanford U., Phys. Dept.; Odelius3, Michael; /Stockholm U.; Gaffney1, K.J.; /aff SLAC, PULSE

    2010-06-11

    The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO{sub 4} solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extract an average jump angle of 49 {+-} 4{sup o}, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO{sub 4} solution.

  19. Reaction mechanism of 3-chlorophenol with OH, H in aqueous solution.

    Science.gov (United States)

    Zhu, Jie; Chen, Ye-Fei; Dong, Wen-Bo; Pan, Xun-Xi; Hou, Hui-Qi

    2003-01-01

    The reaction mechanism of 3-chlorophenol with OH, H in aqueous solution was studied by transient technology. The 3-chlorophenol aqueous solutions have been saturated with air or N2 previously. Under alkaline condition, the reaction of OH radical with 3-chlorophenol produces 3-chlorinated phenoxyl radical, with the absorption peaks at 400 nm and 417 nm. Under neutral condition, the reaction of OH radical with 3-chlorophenol produces OH-adduct with the maximal absorption at about 340 nm. And in acid solution, the reaction of H with 3-chlorophenol produces H-adduct with the maximal absorption at about 320 nm. 3-chlorophenol is compared with 4-and 2-chlorophenols from the free radical pathways. The results show that the positions of chlorine on the aromatic ring strongly influence the dehalogenation and degradation process.

  20. Shellac-coated iron oxide nanoparticles for removal of cadmium(Ⅱ) ions from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Jilai Gong; Long Chen; Guangming Zeng; Fei Long; Jiuhua Deng; Qiuya Niu; Xun He

    2012-01-01

    This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer,a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups,on the surface of iron oxide magnetic nanoparticles.Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm.Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution.Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g.SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions,and cadmium could easily be desorbed using mild organic acid solutions at low concentration.

  1. Thermal contraction of aqueous glycerol and ethylene glycol solutions for optimized protein-crystal cryoprotection.

    Science.gov (United States)

    Shen, Chen; Julius, Ethan F; Tyree, Timothy J; Moreau, David W; Atakisi, Hakan; Thorne, Robert E

    2016-06-01

    The thermal contraction of aqueous cryoprotectant solutions on cooling to cryogenic temperatures is of practical importance in protein cryocrystallography and in biological cryopreservation. In the former case, differential contraction on cooling of protein molecules and their lattice relative to that of the internal and surrounding solvent may lead to crystal damage and the degradation of crystal diffraction properties. Here, the amorphous phase densities of aqueous solutions of glycerol and ethylene glycol at T = 77 K have been determined. Densities with accuracies of solutions. The use of these densities in contraction matching of internal solvent to the available solvent spaces is complicated by several factors, most notably the exclusion of cryoprotectants from protein hydration shells and the expected deviation of the contraction behavior of hydration water from bulk water. The present methods and results will assist in developing rational approaches to cryoprotection and an understanding of solvent behavior in protein crystals.

  2. Recrystallization of freezable bound water in aqueous solutions of medium concentration

    Science.gov (United States)

    Lishan, Zhao; Liqing, Pan; Ailing, Ji; Zexian, Cao; Qiang, Wang

    2016-07-01

    For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries. Project supported by the Knowledge Innovation Project of Chinese Academy of Sciences on Water Science Research (Grant No. KJZD-EW-M03) and the National Natural Science Foundation of China (Grant Nos. 11474325 and 11290161).

  3. Preparation of stable aqueous solution of keratins, and physiochemical and biodegradational properties of films.

    Science.gov (United States)

    Yamauchi, K; Yamauchi, A; Kusunoki, T; Kohda, A; Konishi, Y

    1996-08-01

    A stable aqueous solution of reduced keratins was prepared by extracting the proteins from wool (Corriedale) with a mixture of urea, mercaptanol, surfactant, and water at 40-60 degrees C. Sodium dodecyl sulfate was especially effective as a surfactant, not only in promoting extraction but also in stabilizing the aqueous protein solution. The proteins had the following constants: MW, 52,000-69,000 daltons; cysteine content, 8-9 mol%; pl about 6.7. A clear film was readily prepared from a keratin solution containing glycerol. The film was insoluble in water and organic solvents including dimethyl sulfoxide. The keratin film was permeable to glucose, urea, and sodium chloride. The keratin film was degraded in vitro (by trypsin) and in vivo (by subcutaneous embedding in mice).

  4. Thermodynamic Modeling of Surface Tension of Aqueous Electrolyte Solution by Competitive Adsorption Model

    Directory of Open Access Journals (Sweden)

    Mohamad Javad Kamali

    2015-01-01

    Full Text Available Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively.

  5. Recrystallization of freezable bound water in aqueous solutions of medium concentrations

    Institute of Scientific and Technical Information of China (English)

    赵立山; 潘礼庆; 纪爱玲; 曹则贤; 王强

    2016-01-01

    For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings diffi-culty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentra-tion range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrys-tallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries.

  6. The Study of Dissolution Kinetics of K2SO4 Crystal in Aqueous Ethanol Solutions with a Statistical Rate Theory

    Institute of Scientific and Technical Information of China (English)

    刘畅; 冯新; 吉晓燕; 陈栋梁; 魏涛; 陆小华

    2004-01-01

    Dissolution kinetics of K2SO4 crystal in aqueous ethanol solutions was studied on-line with ion selective electrode. The concentration of K2SO4 was calculated from the determined electromotive force in which the activity coefficient of components in the liquid phase was calculated with the Pitzer equation. Dissolution kinetic parameters in the modified statistical rate theory were regressed. The correlation results show that dissolution rate of K2SO4 is slower in aqueous ethanol solutions than that in aqueous solutions. The two most important reasons are as follows: (1) The solubility of K2SO4 in aqueous ethanol solutions is lower than that in aqueous solutions, which causes a decrease of the driving force of mass transfer. (2) The process of surface reaction of K2SO4 became slower due to the addition of ethanol, so that the whole process is mainly dominated by the surface reaction instead of mass transfer.

  7. Enzyme stabilization by glass-derived silicates in glass-exposed aqueous solutions

    Science.gov (United States)

    Ives, J.A.; Moffett, J.R.; Arun, P.; Lam, D.; Todorov, T.I.; Brothers, A.B.; Anick, D.J.; Centeno, J.; Namboodiri, M.A.A.; Jonas, W.B.

    2010-01-01

    Objectives: To analyze the solutes leaching from glass containers into aqueous solutions, and to show that these solutes have enzyme activity stabilizing effects in very dilute solutions. Methods: Enzyme assays with acetylcholine esterase were used to analyze serially succussed and diluted (SSD) solutions prepared in glass and plastic containers. Aqueous SSD preparations starting with various solutes, or water alone, were prepared under several conditions, and tested for their solute content and their ability to affect enzyme stability in dilute solution. Results: We confirm that water acts to dissolve constituents from glass vials, and show that the solutes derived from the glass have effects on enzymes in the resultant solutions. Enzyme assays demonstrated that enzyme stability in purified and deionized water was enhanced in SSD solutions that were prepared in glass containers, but not those prepared in plastic. The increased enzyme stability could be mimicked in a dose-dependent manner by the addition of silicates to the purified, deionized water that enzymes were dissolved in. Elemental analyses of SSD water preparations made in glass vials showed that boron, silicon, and sodium were present at micromolar concentrations. Conclusions: These results show that silicates and other solutes are present at micromolar levels in all glass-exposed solutions, whether pharmaceutical or homeopathic in nature. Even though silicates are known to have biological activity at higher concentrations, the silicate concentrations we measured in homeopathic preparations were too low to account for any purported in vivo efficacy, but could potentially influence in vitro biological assays reporting homeopathic effects. ?? 2009 The Faculty of Homeopathy.

  8. The vapour pressure of water as a function of solute concentration above aqueous solutions of fructose, sucrose, raffinose, erythritol, xylitol, and sorbitol

    DEFF Research Database (Denmark)

    Cooke, S.A.; Jonsdottir, Svava Osk; Westh, Peter

    2002-01-01

    The vapour pressure of water above an aqueous solution of sucrose at T = 298.06 K has been measured for 9 sucrose mole fractions up to 0.12. Vapour pressure measurements have also been made on aqueous solutions of meso-erythritol, xylitol, sorbitol, fructose, and raffinose at T = 317.99 K. The ex....... The excess molar enthalpy has also been determined for the aqueous sucrose system at T = 318.15 K. The data obtained are compared to literature data for related systems and the effects of the solutes on solution structure are discussed....

  9. Mössbauer spectroscopic studies of frozen aqueous solutions of Fe3+ salts

    DEFF Research Database (Denmark)

    Mørup, Steen; Knudsen, J. E.; Nielsen, M. K.

    1976-01-01

    Frozen aqueous solutions (FAS) of Fe3+ salts have been investigated by use of Mössbauer spectroscopy in order to study the conditions for formation of glasses. A general discussion of spin–spin relaxation in glasses is given, and we discuss how changes in the spin–spin relaxation time can...... concentration of the solution increases. At low temperatures the crystallization terminates and the remaining liquid solidifies into a glass. During exposure at 200 K, the dilute samples change irreversibly. This is discussed in terms of a metastable phase diagram. The properties of frozen solutions with other...

  10. Structural properties of aqueous metoprolol succinate solutions. Density, viscosity, and refractive index at 311 K

    Science.gov (United States)

    Deosarkar, S. D.; Kalyankar, T. M.

    2013-06-01

    Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.

  11. Removal of Diazinon from aqueous solution by electrocoagulation process using aluminum electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Amooey, Ali Akbar; Ghasemi, Shahram; Mirsoleimani-azizi, Seyed Mohammad; Gholaminezhad, Zohreh; Chaichi, Mohammad Javad [University of Mazandaran, Babolsar (Iran, Islamic Republic of)

    2014-06-15

    Electrocoagulation (EC) is an electrochemical method to treat polluted wastewaters and aqueous solutions. In this paper, the removal of Diazinon was studied by EC on aluminum electrode. The effect of several parameters such as initial concentration of Diazinon, current density, solution conductivity, effect of pH, and electrolysis time were investigated on EC performance. The obtained results showed that the removal efficiency of EC depends on the current density, initial concentration of Diazinon and electrolysis time. The optimum pH is 3 and also the solution conductivity has no significant effect on removal efficiency.

  12. Thermodynamic Study of Hydrolysis Reactions in Aqueous Solution from Ab Initio Potential and Molecular Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    S. Tolosa

    2013-01-01

    Full Text Available A procedure for the theoretical study of chemical reactions in solution by means of molecular dynamics simulations of aqueous solution at infinite dilution is described using ab initio solute-solvent potentials and TIP3P water model to describe the interactions. The procedure is applied to the study of neutral hydrolysis of various molecules (HCONH2, HNCO, HCNHNH2, and HCOOCH3 via concerted and water-assisted mechanisms. We used the solvent as a reaction coordinate and the free energy curves for the calculation of the properties related with the reaction mechanism, namely, reaction and activation energies.

  13. Thermodynamic and transport properties of some biologically active compounds in aqueous solutions at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Dhondge, Sudhakar S., E-mail: s_dhondge@hotmail.co [P.G. Department of Chemistry, S.K. Porwal College, Kamptee, Nagpur 441 002 (India); Zodape, Sangesh P.; Parwate, Dilip V. [Department of Chemistry, R.T.M. Nagpur University, Nagpur 440 033 (India)

    2011-01-15

    The experimental data of density and viscosity have been obtained for aqueous solutions of biologically active compounds like salbutamol sulphate (SS), diethylcarbamazine citrate (DEC), and chlorpheniramine maleate (CPM) in the concentration range (0 to 0.15) mol . kg{sup -1} at three different temperatures. The derived parameters, such as apparent molar volume of solute ({phi}{sub V})), limiting apparent molar volume of solute ({phi}{sub V}{sup 0}), limiting apparent molar expansivity ({phi}{sub E}{sup 0}), thermal expansion coefficient ({alpha}*) and Jones-Dole equation viscosity A and B coefficients, were obtained using the density and viscosity results. It has been observed that the electrolyte-salt (SS) as well as adducts exhibit a positive viscosity B coefficient having negative ((dB)/(dT)). These results are interpreted in the light of possible solute-solute and solute-solvent interactions.

  14. Adsorption of organic acids from dilute aqueous solution onto activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.W.

    1980-06-01

    The radioisotope technique was used to study the removal of organic acid contaminants from dilute aqueous solutions onto activated carbon. Acetic acid, propionic acid, n-butyric acid, n-hexanoic acid and n-heptanoic acid were studied at 278, 298, and 313/sup 0/K. Three bi-solute acid mixtures (acetic and propionic acids, acetic and butanoic acids, and propionic and butanoic acids) were studied at 278 and 298/sup 0/K. Isotherms of the single-solute systems were obtained at three different temperatures in the very dilute concentration region (less than 1% by weight). These data are very important in the prediction of bi-solute equilibrium data. A Polanyi-based competitive adsorption potential theory was used to predict the bi-solute equilibrium uptakes. Average errors between calculated and experimental data ranges from 4% to 14%. It was found that the competitive adsorption potential theory gives slightly better results than the ideal adsorbed solution theory.

  15. Porous Methyltrimethoxysilane Coated Nanoscale-Hydroxyapatite for Removing Lead Ions from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    C. S. Ciobanu

    2014-01-01

    Full Text Available The aim of this study was to synthetize new porous nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp for lead removal form aqueous solutions. The morphological and compositional analysis of MTHAp were investigated by X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM equipped with an energy dispersive X-ray spectrometer (EDS. Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+ at a fixed pH value of 3 and 5 respectively. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp_3 and PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cation exchange reaction. The X-ray diffraction spectra of PbMTHAp_3 and PbMTHAp_5 revealed that the powders, after removal of the Pb2+ ions, were a mixture of Ca2.5Pb7.5(PO46(OH2, Pb2Ca4(PO42(SiO4, and Ca10(PO46(OH2. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb2+ ions from aqueous solutions.

  16. High pressure nanoelectrospray ionization mass spectrometry for analysis of aqueous solutions.

    Science.gov (United States)

    Rahman, Md Matiur; Mandal, Mridul Kanti; Hiraoka, Kenzo; Chen, Lee Chuin

    2013-11-07

    Nanoelectrospray ionization (nanoESI) with a very fine emitter and nanoliter solution flow rate is known to be suitable for aqueous solutions. However, under atmospheric pressure, its stability with aqueous solutions is not always guaranteed particularly in the negative ion mode where corona and arc discharge tend to occur more easily. Electrical discharge can be quenched to a certain extent by adding electron scavenging gases like SF6 or CO2 to the ion source. The onset potential that is required to induce the discharge also increases with an increase of gas pressure. Recently, we have reported on a series of high pressure electrospray ion sources that were stable in both positive and negative ion modes using air or N2 as the working gas. In this paper, we compare the performance of nanoelectrospray under atmospheric pressure and super-atmospheric pressure for the analysis of samples in aqueous solution. The comparative study was performed using the same ion source chamber that could be pressurized up to 6 bar. The pressure in the first pumping stage of the mass spectrometer was kept constant when the ion source pressure was changed by using an additional pump with variable pumping speed. High pressure nanoESI optimized at 2-3 bar demonstrated a 3-5 times improvement in ion signal intensity compared to atmospheric pressure nanoESI, and the signal stability was significantly improved particularly in the negative mode.

  17. Preparation and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution.

    Science.gov (United States)

    Wang, Yu; Gao, Bao-yu; Yue, Wen-wen; Yue, Qin-yan

    2007-01-01

    In order to reduce the impact of eutrophication caused by agricultural residues (i.e., excess nitrate) in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions (SO4(2-), H2PO4(-), NO3(-), and NO2(-)) were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.

  18. Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

    Science.gov (United States)

    Sarkar, Abhijit; Sinha, Biswajit

    2016-11-15

    The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker.

  19. New design of electric double layer capacitors with aqueous LiOH electrolyte as alternative to capacitor with KOH solution

    Science.gov (United States)

    Stepniak, Izabela; Ciszewski, Aleksander

    Activated carbon (AC) fiber cloths and a hydrophobic microporous polypropylene (PP) membrane, both modified with lithiated acetone oligomers, were used as electrodes and a separator in electric double layer capacitors (EDLCs) with aqueous lithium hydroxide (LiOH) as the electrolyte. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge cycle tests and impedance spectroscopy (EIS), compared with a case of the capacitor with aqueous potassium hydroxide (KOH) as an electrolyte. As a result, the capacitor with LiOH aqueous solution and a modified separator and electrodes was found to exhibit higher specific capacitance, maximum energy stored and maximum power than that with KOH aqueous solution.

  20. Removal of chromium(VI) from aqueous solutions by polymer inclusion membranes.

    Science.gov (United States)

    Kozlowski, Cezary A; Walkowiak, Wladyslaw

    2002-11-01

    The transport through polymer inclusion membranes (PIMs) was found as the effective and selective method of chromium(VI) anions removal from chloride acidic aqueous solutions. The optimal PIMs content was as follows: 41 wt% of cellulose triacetate as the support, 23 wt% of tri-n-octylamine as the ionic carrier, and 36 wt% of o-nitrophenyl pentyl ether as the plasticizer. The results obtained show a linear decrease of permeability coefficient and initial flux values with source phase pH increase. Also linear decrease of initial flux in log-log scale with chromium(VI) concentration increase was observed. Value of slope of this relationship was found to be 0.96 which indicates a first order of chromium(VI) reaction with tri-n-octylamine at membrane/aqueous source interface. Transport of chromium(VI) through PIMs reduces the concentration of chromium(VI) in source aqueous phase from 1.0 to 0.0028 ppm, which is below permissible limit in drinking water in Poland. Competitive transport of chromium(VI), cadmium(II), zinc(II), and iron(III) from acidic aqueous solution across PIMs was found to be efficient for chromium(VI) (99%), and cadmium(II) (99%).

  1. On the effect of aqueous ammonia soaking pretreatment on batch and continuous anaerobic digestion of digested swine manure fibers

    DEFF Research Database (Denmark)

    Mirtsou Xanthopoulou, Chrysoula; Jurado, Esperanza; Skiadas, Ioannis;

    2012-01-01

    to enhance their methane productivity in batch experiments. In the present study, continuous experiments at a mesophilic (38°C) CSTR-type anaerobic digester fed with swine manure first and a mixture of manure with AAS-treated digested fibers in the sequel, were performed. The methane yield of AAS...

  2. Recovery of Lead(II from Aqueous Solutions by Zea mays Tassel Biosorption

    Directory of Open Access Journals (Sweden)

    Caliphs M. Zvinowanda

    2010-01-01

    Full Text Available Problem statement: Major adsorbent materials used in heavy metal ion removal from polluted aqueous streams are expensive and difficult to regenerate. In this study, the possibility of using Zea mays tassel, as an alternative low cost biosorbent material to remediate heavy metal pollution was investigated. Lead (II was used because of its wide application in industrial products and well documented toxicity. Approach: Tassel was obtained from mature Zea mays cultivar R52 hybrid plants. The tassel was milled to a powder and was used to adsorb lead(II ions from simulated solutions in batch experiments. The desorption of lead(II was carried out using nitric acid and sodium citrate solutions. The adsorbent was characterized by FTIR, EDX and ESCA before and after application of lead(II solutions. Results: For samples with concentrations of 100 mg L-1 Pb(II, 94-98% was adsorbed and 57-74 and 57-67% recoveries were achieved with 0.5-5 M nitric acid and 0.01-0.2 M sodium citrate as the stripping solutions, respectively. EDX spectrum of pure tassel indicated that group 1 and 2 metals were the major exchangeable ions present on its surface. ESCA analysis picked up small amounts of lead(II in the form of Pb(OH+ and Pb(NH+ ions on the surface of tassel adsorbent exposed to Pb2+ ions and none on pure tassel sample. Functional groups such as -H, -NH2, -C = O and -COOH which are polar and are legends which are capable of binding heavy metals were identified by FTIR. Conclusion: The potential of Zea mays tassel to adsorb and recover heavy metals from aqueous solution was successfully demonstrated with Pb(II sample solutions. The results obtained thus far demonstrated the possibility of using tassel powder in the removal as well as recovery of metals from aqueous solutions.

  3. Solid-, solution-, and gas-state NMR monitoring of ¹³C-cellulose degradation in an anaerobic microbial ecosystem.

    Science.gov (United States)

    Yamazawa, Akira; Iikura, Tomohiro; Shino, Amiu; Date, Yasuhiro; Kikuchi, Jun

    2013-07-29

    Anaerobic digestion of biomacromolecules in various microbial ecosystems is influenced by the variations in types, qualities, and quantities of chemical components. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing the degradation of solids to gases in anaerobic digestion processes. Here we describe a characterization strategy using NMR spectroscopy for targeting the input solid insoluble biomass, catabolized soluble metabolites, and produced gases. ¹³C-labeled cellulose produced by Gluconacetobacter xylinus was added as a substrate to stirred tank reactors and gradually degraded for 120 h. The time-course variations in structural heterogeneity of cellulose catabolism were determined using solid-state NMR, and soluble metabolites produced by cellulose degradation were monitored using solution-state NMR. In particular, cooperative changes between the solid NMR signal and ¹³C-¹³C/¹³C-¹²C isotopomers in the microbial degradation of ¹³C-cellulose were revealed by a correlation heat map. The triple phase NMR measurements demonstrated that cellulose was anaerobically degraded, fermented, and converted to methane gas from organic acids such as acetic acid and butyric acid.

  4. Solid-, Solution-, and Gas-state NMR Monitoring of 13C-Cellulose Degradation in an Anaerobic Microbial Ecosystem

    Directory of Open Access Journals (Sweden)

    Yasuhiro Date

    2013-07-01

    Full Text Available Anaerobic digestion of biomacromolecules in various microbial ecosystems is influenced by the variations in types, qualities, and quantities of chemical components. Nuclear magnetic resonance (NMR spectroscopy is a powerful tool for characterizing the degradation of solids to gases in anaerobic digestion processes. Here we describe a characterization strategy using NMR spectroscopy for targeting the input solid insoluble biomass, catabolized soluble metabolites, and produced gases. 13C-labeled cellulose produced by Gluconacetobacter xylinus was added as a substrate to stirred tank reactors and gradually degraded for 120 h. The time-course variations in structural heterogeneity of cellulose catabolism were determined using solid-state NMR, and soluble metabolites produced by cellulose degradation were monitored using solution-state NMR. In particular, cooperative changes between the solid NMR signal and 13C-13C/13C-12C isotopomers in the microbial degradation of 13C-cellulose were revealed by a correlation heat map. The triple phase NMR measurements demonstrated that cellulose was anaerobically degraded, fermented, and converted to methane gas from organic acids such as acetic acid and butyric acid.

  5. Anaerobic digestion foaming in full-scale biogas plants: A survey on causes and solutions

    DEFF Research Database (Denmark)

    Kougias, Panagiotis; Boe, Kanokwan; O-Thong, Sompong;

    2014-01-01

    Anaerobic digestion foaming is a common operation problem in biogas plants with negative impacts on the biogas plants economy and environment. A survey of 16 Danish full-scale biogas plants on foaming problems revealed that most of them had experienced foaming in their processes up to three times...

  6. Influence of starch origin on rheological properties of concentrated aqueous solutions

    Directory of Open Access Journals (Sweden)

    Stojanović Željko P.

    2011-01-01

    Full Text Available The rheological properties of corn and potato starch concentrated aqueous solutions were investigated at 25ºC. The starches were previously dispersed in water and the solutions were obtained by heating of dispersions at 115-120ºC for 20 minutes. The solutions of potato starch were transparent, while the corn starch solutions were opalescent. The results of dynamic mechanical measurements showed that the values of viscosity, h, storage modulus, G′, and loss modulus, G″, of the corn starch solutions increased with the storage time. This phenomenon was not observed for the potato starch solutions. It was assumed that the increase of h, G′ and G″ is the result of starch solutions retrogradation. The potato starch solutions retrogradation did not occur probably because of the phosphates presence. The viscosity of 2 mass % corn starch solution is less than the viscosity of 2 mass % potato starch solution. By increasing the concentration of corn starch solution the gel with elastic behavior was formed. The corn starch solutions formed gel as early as at 4 mass % concentration, while potato starch solutions achieved the gel state at the concentration of 5 mass %. The value of exponent m (G′ and G″ µ wm during the transition of potato starch solutions to gel is 0.414, which gives the fractal dimensions for corn starch of 2.10. The obtained value of fractal dimension corresponds to slow aggregation. The corn starch solutions with the starch concentrations higher than 4 mass % form weak gels. For these solutions the values of modulus in rubber plateau were determined. It was found that the modulus in rubber plateau increased with the concentration by the exponent of 4.36. Such high exponent value was obtained in the case when the tridimensional network is formed, i.e. when supermolecular structures like associates or crystal domains are formed.

  7. Thermodynamic characteristics of acid-base equilibria of DL-α-alanyl-DL-norleucine in aqueous solutions at 298 K

    Science.gov (United States)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Bychkova, S. A.; Skvortsov, I. A.

    2015-09-01

    Protolytic equilibria in aqueous solutions of DL-α-alanyl-DL-norleucine are studied via potentiometry and calorimetry. Measurements are made at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (against a background of potassium nitrate). The thermodynamic characteristics (p K, Δ G, Δ H, Δ S) of the stepwise dissociation of the dipeptide both in aqueous-salt solutions and in standard solution are obtained for the first time.

  8. The removal of lead ions using zeolite nanoparticles from aqueous solutions

    Science.gov (United States)

    Joshi, Parth

    2016-05-01

    The experiment for adsorption of lead ions from its aqueous solutions were carried out at room temperature and initial concentration of lead ions as well as after adsorption were determined by UV-Visible spectrophotometer. The effect of various parameters such as contact time, zeolite nanoparticles dosage and initial concentration of lead ions on the adsorption capacity of zeolite nanoparticles were studied in batch experiment. The kinetics of the adsorption processes was studied by using pseudo-first order and pseudo-second order. The pseudo-second order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first order. The maximum lead ions adsorbed was found to be 43.91 mg/g. The present study indicated that zeolite nanoparticles could be used as an efficient adsorbent for removal of lead ions from aqueous solution.

  9. Solubilization of benzene, toluene, and xylene (BTX) in aqueous micellar solutions of amphiphilic imidazolium ionic liquids.

    Science.gov (United States)

    Łuczak, Justyna; Jungnickel, Christian; Markiewicz, Marta; Hupka, Jan

    2013-05-09

    Water-soluble ionic liquids may be considered analogues to cationic surfactants with a corresponding surface activity and ability to create organized structures in aqueous solutions. For the first time, the enhanced solubility of the aromatic hydrocarbons, benzene, toluene, and xylene, in aqueous micellar systems of 1-alkyl-3-methylimidazolium chlorides was investigated. Above a critical micelle concentration, a gradual increase in the concentration of aromatic hydrocarbons in the miceller solution was observed. This phenomenon was followed by means of the molar solubilization ratio, the micellar/water partition coefficient, and the number of solubilizate molecules per IL micelle. The molar solubilization ratio for ionic liquid micelles was found to be significantly higher when compared to that of ionic surfactants of similar chain length. The incorporation of the hydrocarbon into the micelle affects also an increase of the aggregation number.

  10. MATHEMATICAL MODELLING OF CaCl2 AQUEOUS SOLUTIONS THERMOPHYSICAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    CRISTINA G. GRIGORAŞ, GABRIELA MUNTIANU, LUCIAN GAVRILĂ *

    2016-12-01

    Full Text Available Calcium chloride is an inorganic salt used in its solid state or as aqueous solutions in a multitude of research and industrial areas going from chemical industry to food, cosmetics or drugs production. This paper was directed to establish mathematical models relating its density and dynamic viscosity with factors such as temperature and concentration since it is known that these properties present a high influence on appropriate transport pipes dimensions and industrial equipment choosing and / or designing processes. The assessment and selection of the adequate models were realized by testing various software’s and equations. The obtained results revealed that calcium chloride aqueous solutions studied thermodynamic properties can accurately be expressed by quadratic (density and respectively by linear equations (dynamic viscosity or by more complex equations. Correlation coefficient, relative error and ANOVA values revealed no significant differences between experimental and calculated data.

  11. Modeling of starch retrogradation onset in its aqueous solution using thermoreversible gelation concept.

    Science.gov (United States)

    Nasseri, R; Mohammadi, N

    2014-01-01

    A model was developed to predict starch retrogradation onset in its aqueous solution and verified with the selected literature data. The most probable chain helix distribution was first estimated via minimizing the system free energy with respect to chain helix length. Later, the calculation was extended to double helix formation among single polymer chains with ζ₂=10 as the retrogradation criterion. ζ₂ is the average double helix length usually equals 10 implying the number of participating residues in the thickness of the thinnest reported starch lamella in the literature. The model prediction namely the retrogradation onset temperature, showed quite reasonable agreement with the selected literature data. Equal chain conformational entropy loss, Δs/k(B)≈-0.7, was inferred for various starch aqueous solutions due to the double helix kind of associations. Nonetheless, the studied systems showed distinct restrictions, σ=9 × 10(-4)-4.7 × 10(-3), against association.

  12. Fast heavy-ion radiation damage of glycine in aqueous solution

    Science.gov (United States)

    Nomura, Shinji; Tsuchida, Hidetsugu; Furuya, Ryosuke; Majima, Takuya; Itoh, Akio

    2016-12-01

    Fast heavy-ion radiolysis of biomolecules in aqueous solution is investigated for an atomistic understanding of radiation damage to normal cells during heavy-particle beam therapy. The smallest amino acid glycine was used as a model biomaterial. Microjets of aqueous glycine solutions under vacuum were irradiated with 4.0-MeV carbon ions corresponding to energies in the Bragg peak region. To understand the effects of the water environment on molecular damage, the yield of glycine dissociation was measured by secondary ion mass spectroscopy. The yield was significantly reduced relative to gas-phase glycine targets. This implies that the numerous water molecules surrounding a single glycine molecule act as a buffer that suppresses dissociation. This is an environmental effect similar to that observed for other biomolecular cluster targets.

  13. Removal of lead from aqueous solution using waste tire rubber ash as an adsorbent

    Directory of Open Access Journals (Sweden)

    H. Z. Mousavi

    2010-03-01

    Full Text Available The purpose of this study was to investigate the possibility of the utilization of waste tire rubber ash (WTRA as a low cost adsorbent for removal of lead (II ion from aqueous solution. The effect of different parameters (such as contact time, sorbate concentration, adsorbent dosage, pH of the medium and temperature were investigated. The sorption process was relatively fast and equilibrium was reached after about 90 min of contact. The experimental data were analyzed by the Freundlich isotherm and the Langmuir isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 22.35 mg/g. The adsorption kinetics was investigated and the best fit was achieved by a first-order equation. The results of the removal process show that the Pb (II ion adsorption on WTRA is an endothermic and spontaneous process. The procedure developed was successfully applied for the removal of lead ions in aqueous solutions.

  14. Water activity of aqueous solutions of ethylene oxide-propylene oxide block copolymers and maltodextrins

    Directory of Open Access Journals (Sweden)

    N. D. D. Carareto

    2010-03-01

    Full Text Available The water activity of aqueous solutions of EO-PO block copolymers of six different molar masses and EO/PO ratios and of maltodextrins of three different molar masses was determined at 298.15 K. The results showed that these aqueous solutions present a negative deviation from Raoult's law. The Flory-Huggins and UNIFAC excess Gibbs energy models were employed to model the experimental data. While a good agreement was obtained with the Flory-Huggins equation, discrepancies were observed when predicting the experimental behavior with the UNIFAC model. The water activities of ternary systems formed by a synthetic polymer, maltodextrin and water were also measured and used to test the predictive capability of both models.

  15. Direct conversion of chitin biomass to 5-hydroxymethylfurfural in concentrated ZnCl2 aqueous solution

    DEFF Research Database (Denmark)

    Wang, Yingxiong; Pedersen, Christian Marcus; Deng, Tiansheng;

    2013-01-01

    The direct conversion of chitin biomass to 5-hydroxymethylfurfural (5-HMF) in ZnCl2 aqueous solution was studied systemically. D-Glucosamine (GlcNH2) was chosen as the model compound to investigate the reaction, and 5-HMF could be obtained in 21.9% yield with 99% conversion of GlcNH2. Optimization...... to be 67 wt.% ZnCl2 aqueous solution, at 120 °C without co-catalyst. The reactions were further studied by in situ NMR, and no intermediate or other byproducts, except humins, were observed. Finally, the substrate scope was expanded from GlcNH2 to N-acetyl-D-glucosamine and various chitosan polymers...

  16. Usefulness of Activated Carbon Prepared from Industrial Wastes in the Removal of Nickel from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    R. Rajalakshmi

    2009-01-01

    Full Text Available Elimination of heavy metals like nickel from waste water is an important subject in view of public health. In the present study, an attempt has been made to study the applicability of industrial by-products as potential metal adsorbents to remove nickel from aqueous solutions and polluted water. A direct proportionality between the percentage of Ni(II removal and adsorbent dosage was noted. Maximum removal ⁄ recovery of nickel was achieved at pH range of 10-12 for all adsorbents. An optimum temperature of 40 °C for efficient removal of Ni(II was observed. The effect of nickel adsorption was affected by salinity. The adsorption isotherm data confirmed to Freundlich and Langmuir isotherms. Conformation of data to the Lagergren᾽s rate equation indicated first order kinetics. The suitability of the industrial by-products in the successful removal of nickel from aqueous solution is quite obvious from the study.

  17. Determination of Trace Iodide in Sodium Bisulfite Aqueous Solution by Ion Chromatography with UV Detection

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y.S.; Kim, D.Y.; Choi, K.S.; Park, S.D.; Han, S.H. [Korea Atomic Energy Research Institute, Taejon (Korea)

    2000-06-01

    The iodide was recovered from a simulated spent fuel to the sodium bisulfite aqueous solution. It was discussed that the trace iodide (below 1 ppm) was determined without the matrix effect of 0.1 M sodium bisulfite and 1 mM HNO{sub 3} in aqueous solution by ion chromatography with UV detection. AS4A-SC(DIONEX) column and UV-absorption spectrophotometer were used. The UV-absorption spectra of sodium bisulfite nitric acid and iodide were obtained, and then 230 nm was selected as an absorption wavelength for iodide determination. 0.1 M NaCl eluent was optimum condition. In this condition the calibration curve of iodide was obtained on the range of about 0-1,000 ppb. The linear coefficient was 0.99993 and the detection limit was 5 ppb. The relative standard deviation was 1.26%. (author). 17 refs., 3 tabs., 4 figs.

  18. Biosorption of Cr(VI from Aqueous Solution Using Murraya koenigii (Curry tree Stems

    Directory of Open Access Journals (Sweden)

    Selvaraj Suresh

    2016-12-01

    Full Text Available In the present work, the sorption capacity of Murraya Koenigii Stems (MKST, an agricultural waste, is identified for the removal of Cr(VI from aqueous solution and the effect of different process parameters likes pH and adsorbent dosage were studied. pH 1 is observed to be the optimum pH for Cr(VI sorption onto the biosorbent. The equilibrium data of Cr(VI sorption fit well with the Langmuir model with a monolayer sorption capacity of 12.25 mg/g. The results show that the metal ion interacts strongly with the biosorbent and can be effectively used in the removal of Cr(VI from aqueous solution. DOI: http://dx.doi.org/10.17807/orbital.v0i0.867

  19. Mechanistic study of fulvic acid assisted propranolol photodegradation in aqueous solution.

    Science.gov (United States)

    Makunina, Maria P; Pozdnyakov, Ivan P; Chen, Yong; Grivin, Vyacheslav P; Bazhin, Nikolay M; Plyusnin, Victor F

    2015-01-01

    Laser flash (355 nm) and stationary (365 nm) photolysis were used to study the mechanisms of propranolol photolysis in the presence of fulvic acid in aqueous solutions. The FA-assisted photodegradation of propranolol was observed using UV-A irradiation (where propranolol is stable). Direct evidence indicated that the photodegradation resulted from the static quenching of the FA triplet state by propranolol via the electron transfer mechanism. The triplet state yield (ϕT≈0.6%) and the T-T absorption coefficient (ɛT(620 nm)≈5×10(4) M(-1) cm(-1)) were estimated for the first time by modeling the yields of the FA triplet state in the presence of propranolol. Thus, fulvic acid is a promising agent for accelerating propranolol photodegradation in aqueous solutions under UV-A light irradiation.

  20. Self-assembling of poly(aspartic acid) with bovine serum albumin in aqueous solutions.

    Science.gov (United States)

    Nita, L E; Chiriac, A P; Bercea, M; Asandulesa, M; Wolf, Bernhard A

    2017-02-01

    Macromolecular co-assemblies built up in aqueous solutions, by using a linear polypeptide, poly(aspartic acid) (PAS), and a globular protein, bovine serum albumin (BSA), have been studied. The main interest was to identify the optimum conditions for an interpenetrated complex formation in order to design materials suitable for biomedical applications, such as drug delivery systems. BSA surface possesses several amino- and carboxylic groups available for covalent modification, and/or bioactive substances attachment. In the present study, mixtures between PAS and BSA were investigated at 37°C in dilute aqueous solution by viscometry, dynamic light scattering and zeta potential determination, as well as in solid state by AFM microscopy and dielectric spectroscopy. The experimental data have shown that the interpolymer complex formation occurs for a PAS/BSA molar ratio around 0.541.

  1. Observation and photophysical characterization of silicon phthalocyanine J-aggregate dimers in aqueous solutions.

    Science.gov (United States)

    Doane, Tennyson; Chomas, Andrew; Srinivasan, Shriya; Burda, Clemens

    2014-06-23

    The use of macrocyclic molecules for both imaging and photodynamic therapy (PDT) has proven to be a powerful method for assessing and treating diseases, respectively. However, many potential candidates for these applications rely on rigid organic structures which are hydrophobic and thus lead to possible aggregation in aqueous solutions such as blood. Here, we describe the discovery of noncovalent J-aggregate dimers of the asymmetrically, axially modified silicon phthalocyanine 4 (Pc 4) in aqueous solutions through steady-state and time-resolved spectroscopy. Remarkably, the monomer-dimer equilibrium is dictated by water content and pH, with free monomers resulting in favorable solvation conditions even after formation of the dimer complex. This work sheds light on previous observations of Pc 4 behavior in cells during PDT, and can further elucidate the structure-activity relationship of these important molecules.

  2. Removal of Arsenic(V) from Aqueous Solutions by Lanthanum-loaded Zeolite

    Institute of Scientific and Technical Information of China (English)

    PU Hongping; HUANG Jiangbo; JIANG Zhe

    2008-01-01

    A new adsorption process for the removal of As(V) ion from aqueous solutions is studied in this paper using lanthanum-loaded zeolite. The removal efficiency of different adsorbents, activated alumina and activated carbon are obtained in the study for comparison. The results show that lanthanum-loaded zeolite is an effective adsorbent for the removal of As(V) from aqueous solutions.Then, the pH effect and regeneration of modified zeolite on the As(V) removing efficiency are also assessed. It functions with a wide range of pH (2-8). After adsorption, zeolite adsorbed with As(V) ions can be regenerated successfully with 1 M NaOH. Based on the data obtained, an adsorption mechanism and the possible complex structure are tentatively presented. Compare to other adsorbents, easy availability of this adsorbent, excellent adsorption capacity, wide optimum pH range, and regeneration are expected to be utilized in practical operations.

  3. Application of magnetic chitosan composites for the removal of toxic metal and dyes from aqueous solutions.

    Science.gov (United States)

    Reddy, D Harikishore Kumar; Lee, Seung-Mok

    2013-12-01

    Magnetic chitosan composites (MCCs) are a novel material that exhibits good sorption behavior toward various toxic pollutants in aqueous solution. These magnetic composites have a fast adsorption rate and high adsorption efficiency, efficient to remove various pollutants and they are easy to recover and reuse. These features highlight the suitability of MCCs for the treatment of water polluted with metal and organic materials. This review outlines the preparation of MCCs as well as methods to characterize these materials using FTIR, XRD, TGA and other microscopy-based techniques. Additionally, an overview of recent developments and applications of MCCs for metal and organic pollutant removal is discussed in detail. Based on current research and existing materials, some new and futuristic approaches in this fascinating area are also discussed. The main objective of this review is to provide up-to-date information about the most important features of MCCs and to show their advantages as adsorbents in the treatment of polluted aqueous solutions.

  4. ESR study on radiation-induced radicals in carboxymethyl cellulose aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Saiki, Seiichi, E-mail: saiki.seiichi@jaea.go.j [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Nagasawa, Naotsugu; Hiroki, Akihiro; Morishita, Norio; Tamada, Masao [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kudo, Hisaaki [Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Katsumura, Yosuke [Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan)

    2011-02-15

    Carboxymethyl cellulose (CMC) at highly concentrated aqueous solution undergoes radiation crosslinking reaction by ionizing irradiation. It is assumed that this radiation-induced reaction takes place by the indirect effect of water radiolysis, especially through the OH radical. However, the reaction mechanism is not well known. In this topic, ESR spectra of CMC radicals formed by reaction with OH radicals were measured directly in aqueous solution to identify the initially formed radical site. The ESR spectra were observed successfully and were interpreted as the overlapping of two spectra; a TripletxDoublet spectrum and a Doublet spectrum. Each spectrum was assigned to radicals located on carboxymethyl groups linked to C6 and C2/C3.

  5. ESR study on radiation-induced radicals in carboxymethyl cellulose aqueous solution

    Science.gov (United States)

    Saiki, Seiichi; Nagasawa, Naotsugu; Hiroki, Akihiro; Morishita, Norio; Tamada, Masao; Kudo, Hisaaki; Katsumura, Yosuke

    2011-02-01

    Carboxymethyl cellulose (CMC) at highly concentrated aqueous solution undergoes radiation crosslinking reaction by ionizing irradiation. It is assumed that this radiation-induced reaction takes place by the indirect effect of water radiolysis, especially through the OH radical. However, the reaction mechanism is not well known. In this topic, ESR spectra of CMC radicals formed by reaction with OH radicals were measured directly in aqueous solution to identify the initially formed radical site. The ESR spectra were observed successfully and were interpreted as the overlapping of two spectra; a Triplet×Doublet spectrum and a Doublet spectrum. Each spectrum was assigned to radicals located on carboxymethyl groups linked to C6 and C2/C3.

  6. Enhanced removal of Hg(II) from acidic aqueous solution using thiol-functionalized biomass.

    Science.gov (United States)

    Chai, Liyuan; Wang, Qingwei; Li, Qingzhu; Yang, Zhihui; Wang, Yunyan

    2010-01-01

    Spent grain, the low-cost and abundant biomass produced in the brewing industry, was functionalized with thiol groups to be used as an adsorbent for Hg(II) removal from acidic aqueous solution. The adsorbents were characterized by the energy-dispersive X-ray analysis (EDAX) and Fourier transform infrared (FTIR) spectroscopy. Optimum pH for Hg(II) adsorption onto the thiol-functionalized spent grain (TFSG) was 2.0. The equilibrium and kinetics of the adsorption of Hg(II) onto TFSG from acidic aqueous solution were investigated. From the Langmuir isotherm model the maximum adsorption capacity of TFSG for Hg(II) was found to be 221.73 mg g(-1), which was higher than that of most various adsorbents reported in literature. Moreover, the adsorption of Hg(II) onto TFSG followed pseudo-second-order kinetic model.

  7. Modeling of Vapor-Liquid-Solid Equilibria in Acidic Aqueous Solutions

    DEFF Research Database (Denmark)

    Christensen, Søren Gregers; Thomsen, Kaj

    2003-01-01

    The phase behavior (vapor - liquid equilibria (VLE) and solid - liquid equilibria (SLE)) and thermal properties of aqueous solutions of ions like (K+, Na+, NH4+, Ca2+, Cl-) in the presence of phosphoric acid (H3PO4, H2PO4-, HPO42- ) and nitric acid (HNO3, NO3-) are described by means of the Exten......The phase behavior (vapor - liquid equilibria (VLE) and solid - liquid equilibria (SLE)) and thermal properties of aqueous solutions of ions like (K+, Na+, NH4+, Ca2+, Cl-) in the presence of phosphoric acid (H3PO4, H2PO4-, HPO42- ) and nitric acid (HNO3, NO3-) are described by means...

  8. Removal of lead from aqueous solutions by condensed tannin gel adsorbent

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Lead has caused serious environmental pollution due toits toxicity, accumulation in food chains and persistence innature. In this paper, lead removal from aqueous solutions wasinvestigated using condensed tannin gel adsorbent synthesized froma natural tannin compound. It is found that the adsorption isstrongly affected by pH values of aqueous solutions. Within pHrange of 3.5-6, when initial lead concentration is 100 mg/L,removal efficiency is more than 90%. Adsorption equilibrium isreached within 150 minutes. The adsorption isotherm fits well withthe Langmuir equation, by which the saturated adsorption uptake of190 mg Pb2+/g dry tannin gel adsorbent is obtained. By means of thermodynamics analysis, it is revealed that the process isexothermic and the adsorption heat is up to 38.4 kJ/mol. Withrespect to high efficiency, moderate pH requirement and minimizedsecond pollution, the tannin gel adsorbent exhibits a promisingpotential in the removal of lead from wastewater.

  9. Molar Absorptivities of Ultraviolet and Visible Bands of Ozone in Aqueous Solutions

    DEFF Research Database (Denmark)

    Hart, E.J.; Sehested, Knud; Holcman, J.

    1983-01-01

    The molar absorptivities of aqueous ozone solutions [.epsilon.(O3)] are reported for the wavelength ranges 190-300 nm and 350-900 nm. At the maxima of these bands, .epsilon.260(O3) = 3292 .+-. 70 M-1 cm-1 and .epsilon.590(O3) = 5.1 .+-. 0.1 M-1 cm-1. The analyses for ozone were carried out...... of aqueous O3 is compared with that of ozone gas....... by absorbance measurements of the gas at 253.7 nm and by oxidation of FeSO4 in H2SO4 solution followed by back-titration of excess Fe2+ with KMnO4. Spectrophotometric analysis of Fe3+ was also used at low ozone concentrations. A stoichiometric ratio, Fe3+/O3, of 1.996 .+-. 0.036 was found. The visible spectrum...

  10. Cyclic electrowinning/precipitation (CEP) system for the removal of heavy metal mixtures from aqueous solutions.

    Science.gov (United States)

    Grimshaw, Pengpeng; Calo, Joseph M; Hradil, George

    2011-11-15

    The description and operation of a novel cyclic electrowinning/precipitation (CEP) system for the simultaneous removal of mixtures of heavy metals from aqueous solutions are presented. CEP combines the advantages of electrowinning in a spouted particulate electrode (SPE) with that of chemical precipitation and redissolution, to remove heavy metals at low concentrations as solid metal deposits on particulate cathode particles without exporting toxic metal precipitate sludges from the process. The overall result is very large volume reduction of the heavy metal contaminants as a solid metal deposit on particles that can either be safely discarded as such, or further processed to recover particular metals. The performance of this system is demonstrated with data on the removal of mixtures of copper, nickel, and cadmium from aqueous solutions.

  11. Determination of hydroxyl radicals with salicylic acid in aqueous nitrate and nitrite solutions

    Institute of Scientific and Technical Information of China (English)

    YANG Xi; ZHAN Man-jun; KONG Ling-ren; WANG Lian-sheng

    2004-01-01

    The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO3-(10 mmol/L, pH = 5) and NO2- (10 mmol/L, pH = 5) solutions under ultraviolet irradiation were at a same magnitude, 10-15 mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO3- and NO2- respectively, all comparable to the results of previous studies.

  12. Removal of trihalomethanes from aqueous solution through armchair carbon nanotubes: a molecular dynamics study.

    Science.gov (United States)

    Azamat, Jafar; Khataee, Alireza; Joo, Sang Woo; Yin, Binfeng

    2015-04-01

    Molecular dynamics simulations were performed to investigate the removal of trihalomethanes (THMs) including CH3Cl, CH2Cl2 and CHCl3 from aqueous solutions by armchair carbon nanotubes (CNTs) under induced pressure. The studied system involved the armchair CNTs embedded between two graphene sheets with an aqueous solution of THMs in the simulation box. An external pressure was applied to the system along the z-axis of the simulation box. Six types of armchair CNTs with different diameter were used in this work, included (4,4), (5,5), (6,6), (7,7), (8,8) and (9,9) CNTs. The results of molecular dynamics simulation display that the armchair CNTs behave differently relative to THMs and water molecules. The permeation of THMs and water molecules through the armchair CNTs was dependent on the diameter of CNTs and the applied pressure.

  13. Production of furfural from waste aqueous hemicellulose solution of hardwood over ZSM-5 zeolite.

    Science.gov (United States)

    Gao, Hongling; Liu, Haitang; Pang, Bo; Yu, Guang; Du, Jian; Zhang, Yuedong; Wang, Haisong; Mu, Xindong

    2014-11-01

    This study aimed to produce furfural from waste aqueous hemicellulose solution of a hardwood kraft-based dissolving pulp production processing in a green method. The maximum furfural yield of 82.4% and the xylose conversion of 96.8% were achieved at 463K, 1.0g ZSM-5, 1.05g NaCl and organic solvent-to-aqueous phase ratio of 30:15 (V/V) for 3h. The furfural yield was just 51.5% when the same concentration of pure xylose solution was used. Under the optimized condition, furfural yield was still up to 67.1% even after the fifth reused of catalyst. Catalyst recycling study showed that ZSM-5 has a certain stability and can be efficiently reused.

  14. Characteristics of zinc oxide nanorod array/titanium oxide film heterojunction prepared by aqueous solution deposition

    Science.gov (United States)

    Lee, Ming-Kwei; Hong, Min-Hsuan; Li, Bo-Wei

    2016-07-01

    The characteristics of a ZnO nanorod array/TiO2 film heterojunction were investigated. A TiO2 film was prepared on glass by aqueous solution deposition with precursors of ammonium hexafluorotitanate and boric acid at 40 °C. Then, a ZnO seed layer was prepared on a TiO2 film/glass substrate by RF sputtering. A vertically oriented ZnO nanorod array was grown on a ZnO seed layer/TiO2 film/glass substrate by aqueous solution deposition with precursors of zinc nitrate and hexamethylenetetramine (HMT) at 70 °C. After thermal annealing in N2O ambient at 300 °C, this heterojunction used as an oxygen gas sensor shows much better rise time, decay time, and on/off current ratio than as-grown and annealed ZnO nanorods.

  15. Removal of Indigo Carmine Dye from Aqueous Solution Using Magnesium Hydroxide as an Adsorbent

    Directory of Open Access Journals (Sweden)

    Thimmasandra Narayan Ramesh

    2015-01-01

    Full Text Available Magnesium hydroxide is used as an adsorbent for the removal of indigo carmine dye from aqueous solution. We have investigated the effectiveness of removal of indigo carmine dye from aqueous solutions at pH 6-7 and 12-13 using magnesium hydroxide thereby varying the dose of the adsorbent, concentration of the dye, duration, and temperature. Structural transformations of adsorbent during the adsorption process at different pH values are monitored using powder X-ray diffraction and infrared spectroscopy. Different types of adsorption isotherm models were evaluated and it was found that Langmuir isotherm fits well at both pH values (6-7 and 12-13. Adsorption of indigo carmine onto magnesium hydroxide at pH 6-7/pH 12-13 follows pseudo-second order rate kinetics.

  16. Chemical modification of amino acids by atmospheric-pressure cold plasma in aqueous solution

    Science.gov (United States)

    Takai, Eisuke; Kitamura, Tsuyoshi; Kuwabara, Junpei; Ikawa, Satoshi; Yoshizawa, Shunsuke; Shiraki, Kentaro; Kawasaki, Hideya; Arakawa, Ryuichi; Kitano, Katsuhisa

    2014-07-01

    Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

  17. Heat of Absorption of CO2 in Aqueous Solutions of DEEA, MAPA and their Mixture

    DEFF Research Database (Denmark)

    Waseem Arshad, Muhammad; von Solms, Nicolas; Thomsen, Kaj

    2013-01-01

    A reaction calorimeter was used to measure the differential heat of absorption of CO2 in phase change solvents as a function of temperature, CO2 loading and solvent composition. The measurements were taken for aqueous solutions of 2-(diethylamino)ethanol (DEEA), 3-(methylamino)propylamine (MAPA......) and their mixture. The tested compositions were 5M DEEA, 2M MAPA and their mixture, 5M DEEA + 2M MAPA which gives two liquid phases on reacting with CO2. Experimental measurements were also carried out for 30% MEA used as a base case. The measurements were taken isothermally at three different temperatures 40, 80...... and 120°C at a CO2 feed pressure of 600kPa. In single aqueous amine solutions, heat of absorption increases with increase in temperature and depends on thetype of amine used. DEEA, a tertiary amine, has lower heat of absorption compared to MAPA being a diamine with primary and secondary amine functional...

  18. Oxidative dissolution of spent nuclear fuel in aqueous alkaline solutions - An alternative to the Purex process?

    Energy Technology Data Exchange (ETDEWEB)

    Runde, Wolfgang; Peper, Shane; Brodnax, Lia; Crooks, William; Zehnder, Ralph; Jarvinen, Gordon

    2004-07-01

    As an alternative to acidic reprocessing of spent nuclear, oxidative dissolution of UO{sub 2} into aqueous alkaline solutions and subsequent separation of fission products is considered. The efficacy of such a method is limited by the kinetics of the UO{sub 2} dissolution and the capacity of alkaline solutions for dissolved U(VI) species. We performed a series of dissolution studies on UO{sub 2} and U{sub 3}O{sub 8} in aqueous alkaline solutions applying various oxidants. Among the oxidative agents commonly used to transform low-valence actinides into their higher oxidation states, H{sub 2}O{sub 2} has proven to be the most effective in basic media. Consequently, we investigated the dissolution of UO{sub 2} and U{sub 3}O{sub 8} in NaOH-H{sub 2}O{sub 2} and Na{sub 2}CO{sub 3}-H{sub 2}O{sub 2} solutions and determined the dissolution kinetics as a function of peroxide and hydroxide (carbonate) concentrations. Methods to remove fission products, e.g., Cs, Sr, Ba and Zr, from alkaline solutions will be evaluated based upon their decontamination factors. We will discuss the feasibility of using chemically oxidizing alkaline solutions as an alternative spent nuclear fuel reprocessing method based on results from experimental quantitative investigations. (authors)

  19. Removal of methylene blue from aqueous solution using cotton stalk, cotton waste and cotton dust

    Energy Technology Data Exchange (ETDEWEB)

    Ertas, Murat [Department of Forest Industrial Engineering, Faculty of Forestry, Kahramanmaras Sutcu Imam University, 46060 Kahramanmaras (Turkey); Acemioglu, Bilal, E-mail: acemioglu@kilis.edu.tr [Department of Chemistry, Faculty of Science and Arts, Kilis 7 Aralik University, 79000 Kilis (Turkey); Alma, M. Hakki [Department of Forest Industrial Engineering, Faculty of Forestry, Kahramanmaras Sutcu Imam University, 46060 Kahramanmaras (Turkey); Usta, Mustafa [Department of Forest Industrial Engineering, Faculty of Forestry, Karadeniz Technical University, 61080 Trabzon (Turkey)

    2010-11-15

    In this study, cotton stalk (CS), cotton waste (CW) and cotton dust (CD) was used as sorbents to remove methylene blue (MB) from aqueous solution by batch sorption technique. Effects of initial dye concentration, solution pH, solution temperature and sorbent dose on sorption were studied. It was seen that the removal of methylene blue increased with increasing initial dye concentration (from 25 to 100 mg/l), solution pH (from 5 to 10), solution temperature (from 20 to 50 deg. C) and sorbent dose (from 0.25 to 1.50 g/50 ml). The maximum dye removal was reached at 90 min. Sorption isotherms were analyzed by Langmuir and Freundlich models at different temperatures of 20, 30, 40 and 50 deg. C, and the results were discussed in detail. Moreover, the thermodynamics of sorption were also studied. It was found that the values of standard free energy ({Delta}G{sup o}) were positive for cotton stalk and negative for cotton waste and cotton dust. The values of standard enthalpy ({Delta}H{sup o}) and entropy ({Delta}S{sup o}) were found to be positive, and the obtained results were interpreted in detail. The results of this study showed that cotton stalk, cotton waste and cotton dust could be employed as effective and low-cost materials for the removal of dyes from aqueous solution.

  20. Volumetric, ultrasonic speed, and viscometric studies of salbutamol sulphate in aqueous methanol solution at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, K., E-mail: krpal25@yahoo.co [Department of Physics, Government College of Engineering, Tirunelveli 627 007, Tamil Nadu (India); Jayabalakrishnan, S.S., E-mail: krishnanpsr@yahoo.co [Department of Physics, P.S.R. Engineering College, Sivakasi 626 140, Tamil Nadu (India)

    2010-08-15

    Values of density, ultrasonic speed, and viscosity of salbutamol sulphate (SBS) have been determined in aqueous methanol solutions at T = (303.15, 308.15, 313.15, and 318.15) K. The apparent molar volume V{sub {phi}}, partial molar volume V{sub {phi}}{sup 0}, molar expansivity E{sub 2}{sup 0}, isobaric thermal expansion coefficient ({alpha}{sub 2}), and second derivative of infinite dilution of partial molar volume with temperature {partial_derivative}{sup 2}V{sub {phi}}{sup 0}/{partial_derivative}T{sup 2} are evaluated using density data. Isentropic compressibility {beta}{sub s}, change in isothermal compressibility {Delta}{beta}{sub s}, relative change in isentropic compressibility ({Delta}{beta}{sub s}/{beta}{sub s}{sup 0}), apparent molar compressibility K{sub {phi}}and partial molar compressibility K{sub {phi}}{sup 0} values are calculated by using data on density with ultrasonic speed. Viscosity B-coefficient, variation of B-coefficient with temperature, i.e.,dB/dT, free energy of activation per mole of solvent {Delta}{mu}{sub 1}{sup 0*} and solute {Delta}{mu}{sub 2}{sup 0*} are evaluated using viscosity data. The above parameters are used to interpret the solute-solute, solute-solvent interactions and structure making/breaking ability of the drug in the given aqueous methanol solution.

  1. Removal of transition metals from dilute aqueous solution by carboxylic acid group containing absorbent polymers

    Science.gov (United States)

    A new carboxylic acid group containing resin with cation exchange capacity, 12.67 meq/g has been used to remove Cu2+, Co2+ and Ni2+ ions from dilute aqueous solution. The resin has Cu2+, Co2+ and Ni2+ removal capacity, 216 mg/g, 154 mg/g and 180 mg/g, respectively. The selectivity of the resin to ...

  2. Adsorption of Chromium(VI) from Aqueous Solutions by Coffee Polyphenol-Formaldehyde/Acetaldehyde Resins

    OpenAIRE

    2013-01-01

    Removal of chromium(VI) from wastewater is essential as it is toxic. Thus, removal of chromium(VI) was performed using coffee polyphenol-formaldehyde/acetaldehyde resins as adsorbents. Adsorbent resins were prepared by condensation of decaffeinated coffee powder with formaldehyde/acetaldehyde and used for the removal of Cr(VI) ions from aqueous solutions. A simple and sensitive solid phase extraction procedure was applied for the determination of chromium at trace levels by spectroscopic meth...

  3. Removal of lead from aqueous solution using waste tire rubber ash as an adsorbent

    OpenAIRE

    Mousavi,H. Z.; Hosseynifar,A.; Jahed,V.; S. A. M. Dehghani

    2010-01-01

    The purpose of this study was to investigate the possibility of the utilization of waste tire rubber ash (WTRA) as a low cost adsorbent for removal of lead (II) ion from aqueous solution. The effect of different parameters (such as contact time, sorbate concentration, adsorbent dosage, pH of the medium and temperature) were investigated. The sorption process was relatively fast and equilibrium was reached after about 90 min of contact. The experimental data were analyzed by the Freundlich iso...

  4. Small-angle neutron scattering studies of sodium butyl benzene sulfonate aggregates in aqueous solution

    Indian Academy of Sciences (India)

    O R Pal; V G Gaikar; J V Joshi; P S Goyal; V K Aswal

    2004-08-01

    The aggregation behaviour of a hydrotrope, sodium -butyl benzene sulfonate (Na-NBBS), in aqueous solutions is investigated by small-angle neutron scattering (SANS). Nearly ellipsoidal aggregates of Na-NBBS at concentrations well above its minimum hydrotrope concentration were detected by SANS. The hydrotrope seems to form self-assemblies with aggregation number of 36–40 with a substantial charge on the aggregate. This aggregation number is weakly affected by the hydrotrope concentration.

  5. Preparation of nanosized barium zirconate powder by precipitation in aqueous solution

    OpenAIRE

    Boschini, Frédéric; Guillaume, Bernard; Rulmont, André; Cloots, Rudi

    2004-01-01

    Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through an homogeneous precipitation of barium and zirconium salts followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio have been determined by means of X-ray diffraction and Inductive Coupled Plasma analyses. It has been demonstrated that a...

  6. Removal Of Copper From Aqueous Solutions By Using Natural And Fe-Modified Clinoptilolite

    Science.gov (United States)

    Lipovský, Marek; Sirotiak, Maroš; Soldán, Maroš

    2015-06-01

    Removal of copper from aqueous solution on the natural and modified clinoptilolite was studied under static conditions. Batch adsorptions of copper were performed to investigate the effects of contact time and initial metal ion concentration. The Freundlich and Langmuir adsorption isotherms were used to analyse the experimental data. The kinetic analyses of the adsorption processes were performed using the pseudo-first-order and pseudo-second-order kinetic models.

  7. Removal Of Copper From Aqueous Solutions By Using Natural And Fe-Modified Clinoptilolite

    Directory of Open Access Journals (Sweden)

    Lipovský Marek

    2015-06-01

    Full Text Available Removal of copper from aqueous solution on the natural and modified clinoptilolite was studied under static conditions. Batch adsorptions of copper were performed to investigate the effects of contact time and initial metal ion concentration. The Freundlich and Langmuir adsorption isotherms were used to analyse the experimental data. The kinetic analyses of the adsorption processes were performed using the pseudo-first-order and pseudo-second-order kinetic models.

  8. A new turn on coumarin-based fluorescence probe for Ga3 + detection in aqueous solution

    Science.gov (United States)

    Yan, Liqiang; Zhou, Yan; Du, Wenqi; Kong, Zhineng; Qi, Zhengjian

    2016-02-01

    The probe CT was synthesized and investigated as a novel label-free chemosensor for Ga3 + detection in water. Probe CT showed remarkable selectivity and sensitivity for Ga3 + in Tris-HCl aqueous buffer solution (pH 7.0). The chemosensor responded rapidly to Ga3 + with a 1:1 stoichiometry. Meanwhile, the unapparent changes of fluorescence lifetime decays suggest the turn-on process of probe CT by Ga3 + which appears to be a static mechanism.

  9. Silver-Catalyzed Decarboxylative Allylation of Aliphatic Carboxylic Acids in Aqueous Solution.

    Science.gov (United States)

    Cui, Lei; Chen, He; Liu, Chao; Li, Chaozhong

    2016-05-06

    Direct decarboxylative radical allylation of aliphatic carboxylic acids is described. With K2S2O8 as the oxidant and AgNO3 as the catalyst, the reactions of aliphatic carboxylic acids with allyl sulfones in aqueous CH3CN solution gave the corresponding alkenes in satisfactory yields under mild conditions. This site-specific allylation method is applicable to all primary, secondary, and tertiary alkyl acids and exhibits wide functional group compatibility.

  10. Direct hydride derivatization of methyl- and ethylmercury chlorides in aqueous solution with KBH4

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A convenient hydride derivatization procedure of methyl-and ethylmercury chlorides to volatile hydrides was reported. In sealed vials methylmercury and ethylmercury compounds in acidic aqueous solutions were converted into their volatile forms by the reaction with potassium tetrahydroborate(KBH4) and elvolved to the headspace of the vials. The gaseous analytes in the headspace were extracted and concentrated by solid phase microextraction(SPME) and injected into gas chromatography (GC) for separation and identified by mass selective detector(MS).

  11. Rheological properties of wormlike micelles formed in the sodium oleate/trisodium phosphate aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Yong Qiang Ji; Wei Shan Wang; Gan Zuo Li; Li Qiang Zheng

    2008-01-01

    Aqueous solution of anionic surfactant,sodium oleate (NaOA),was studied by means of steady-state shear rheology and dynamic oscillatory technique.The system of NaOA/Na3PO4 showed high viscosity,strong viscoelasticity and good ability of countering Ca2+,Mg2+.The Maxwell model and Cole-Cole plot were applied to study the dynamic viscoelasticity of wormlike micelles.The microstructures of the wormlike micelles were characterized by FF-TEM.

  12. Thermodynamic characteristics of protolytic equilibria in aqueous solutions of glycyl peptides

    Science.gov (United States)

    Gridchin, S. N.

    2016-11-01

    Protolytic equilibria in aqueous solutions of glycyl-DL-serine, glycyl-DL-threonine, and glycyl-DL-valine are investigated by means of potentiometry and calorimetry. Dissociation constants and heat effects of the above dipeptides are determined. Standard thermodynamic characteristics (p K°, Δdis G°, Δdis H°, Δdis S°) of the investigated equilibria are calculated. The obtained results are compared to corresponding data on relative compounds.

  13. Spontaneous Vesicle Formation in Mixed Aqueous Solution of Poly-tailed Cationic and Anionic Surfactants

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Spontaneous vesicles from the mixed aqueous solution of poly-tailed cationic surfactant PTA and anionic surfactant AOT are firstly obtained. Vesicle formation and characterizations are demonstrated by negative-staining TEM and dynamic light scattering. A monodisperse vesicle system is obtained with a polydispersity of 0.082. Ultrasonication can promote the vesicle formation. Mechanism of vesicle formation is discussed from the viewpoint of molecular interaction.

  14. Electrospinning of silk fibroin from all aqueous solution at low concentration.

    Science.gov (United States)

    Kishimoto, Yuki; Morikawa, Hideaki; Yamanaka, Shigeru; Tamada, Yasushi

    2017-04-01

    Non-woven mats of Bombyx mori silk fibroin were fabricated using electrospinning with an all aqueous solution at electrospinning at low concentrations of 5wt%. Evaluation of structural and mechanical properties of the non-woven mat fabricated with water solvent revealed that it is safe for use in the human body. It is anticipated for wider use in medical materials such as cellular scaffolds for tissue engineering.

  15. FT-RAMAN SPECTROSCOPY FOR MONITORING THE POLYMERIZATION OF ACRYLIC ACID IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Jiang Yu; Hui-zhou Liu; Jia-yong Chen

    1999-01-01

    FT-Raman spectroscopy was used to monitor the polymerization of acrylic acid in aqueous solution. A simple method to avoid the noise in the background during the signal processing via Fourier transformation was used in this work. The effects of the amount of initiator used on the polymerization are studied. When the amount of the initiator in the polymerization was increased, both the rate and extent of polymerization of acrylic acid will be increased.

  16. Efficient removal of naphthalene-2-ol from aqueous solutions by solvent extraction.

    Science.gov (United States)

    Shao, Jingjing; Cheng, Yan; Yang, Chunping; Zeng, Guangming; Liu, Wencan; Jiao, Panpan; He, Huijun

    2016-09-01

    Naphthalene-2-ol is a typical biologically recalcitrant pollutant in dye wastewater. Solvent extraction of naphthalene-2-ol from aqueous solutions using mixed solvents was investigated. Various extractants and diluents were evaluated, and the effects of volume ratio of extractant to diluent, initial pH, initial concentration of naphthalene-2-ol in aqueous solution, extraction time, temperature, volume ratio of organic phase to aqueous phase (O/A), stirring rate and extraction stages, on extraction efficiency were examined separately. Regeneration and reuse of the spent extractant were also investigated. Results showed that tributyl phosphate (TBP) achieved 98% extraction efficiency for naphthalene-2-ol in a single stage extraction, the highest among the 12 extractants evaluated. Extraction efficiency was optimized when cyclohexane and n-octane were used as diluents. The solvent combination of 20% TBP, 20% n-octanol and 60% cyclohexane (V/V) obtained the maximum extraction efficiency for naphthalene-2-ol, 99.3%, within 20min using three cross-current extraction stages under the following extraction conditions: O/A ratio of 1:1, initial pH of 3, 25°C and stirring rate of 150r/min. Recovery of mixed solvents was achieved by using 15% (W/W) NaOH solution at an O:A ratio of 1:1 and a contact time of 15min. The mixed solvents achieved an extraction capacity for naphthalene-2-ol stably higher than 90% during five cycles after regeneration.

  17. Biosorption characteristics of Uranium (VI) from aqueous solution by pollen pini.

    Science.gov (United States)

    Wang, Feihong; Tan, Lichao; Liu, Qi; Li, Rumin; Li, Zhanshuang; Zhang, Hongsen; Hu, Songxia; Liu, Lianhe; Wang, Jun

    2015-12-01

    Uranium biosorption from aqueous solutions by pollen pini (Pinus massoniana pollen) was studied in a bath system. The biosorbent was characterized by Fourier-transform infrared spectroscopy and scanning electron microscope. The influences of pH, contact time and initial uranium concentration at room temperature were investigated and the experimental curves were obtained. The pollen pini exhibited the highest uranium sorption capacity at pH 5.0 after 2 h contact. At pH 2.5 pollen pini also exhibited a good uranium loading capacity (>15%). Therefore biosorption characteristics of uranium from aqueous solution onto pollen pini were examined at pH 2.5 as well. The kinetics followed a pseudo-second-order rate equation and adsorption process was well fitted with the Freundlich isotherm at both pH. The adsorption of uranium by the biosorbent was confirmed by energy dispersive spectroscopy. The present study suggested that pollen pini could be a suitable biosorbent for biosorption uranium (VI) from aqueous solution in a fast, low cost and convenient approach.

  18. Preparation and characterization of regenerated fiber from the aqueous solution of Bombyx mori cocoon silk fibroin

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Zhenghua [Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Department of Application Engineering, ZheJiang Vocational College of Economic and Trade, HangZhou, ZheJiang 310018 (China); Imada, Takuzo [Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Asakura, Tetsuo, E-mail: asakura@cc.tuat.ac.jp [Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan)

    2009-10-15

    The regenerated silk fibers with high strength and high biodegradability were prepared from the aqueous solution of Bombyx mori silk fibroin from cocoons with wet spinning method. Although the tensile strength of the regenerated silk fibroin fiber, 210 MPa is still half of the strength of native silk fiber, the diameter of the fiber is about 100 {mu}m which is suitable for monofilament of suture together with high biodegradability. The high concentration (30%, w/v) of the aqueous solution of the silk fibroin which corresponds to the high concentration in the middle silkgland of silkworm was obtained. This was performed by adjusting the pH of the aqueous solution to 10.4 which corresponds to pK{sub a} value of the OH group of Tyr residues in the silk fibroin. The mixed solvent, methanol/acetic acid (7:3 in volume ratio) was used as coagulant solvent for preparing the regenerated fiber. The structural change of silk fibroin fiber by stretching was monitored with both {sup 13}C solid state NMR and X-ray diffraction methods, indicating that the high strength of the fiber is related with the long-range orientation of the silk fibroin chain with {beta}-sheet structure.

  19. Enhancement of Pool Boiling Heat Transfer to Lithium Bromide Aqueous Solution

    Science.gov (United States)

    Furukawa, Masahiro; Kaji, Masuo; Suyama, Takayuki; Sekoguchi, Kotohiko

    An experimental study on enhancement of nucleate pool boiling heat tranfer by placing a sponge metal close to a plain heated surface was conducted in order to improve the heat transfer performance of the high temperature generator of absorption chiller/heater. The sponge metal has three dimensional porous mesh framework like sponge. Boiling curves of water under the atmospheric pressure were compared with those of lithium bromide aqueous solution of mass concentration 55 to 58%. Heat transfer characteristics were improved by 2 to3 times both for water and lithium bromide aqueous solution when the sponge metal was placed on the heated surface with and without cleareance. Three kinds of sponge metals were used for lithium bromide aqueous solution under the reduced pressure (24 kPa). At lower heat fluxes,#6 sponge metal which has the finest mesh and the lowest porosity shows excellent results. At high heat fluxes, however,it causes deterioration of heat transfer. Over the wide range of heat fluxes,# 4 sponge metal was found to be most suitable and the optimal clearence was determined as 0.5 mm. The sponge metal is of good practical use as a device to enhance the boiling, since no special manufacturing is required for placing it on the heated surface.

  20. Bio-inspired capillary dry spinning of regenerated silk fibroin aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Wei Wei; Zhang Yaopeng, E-mail: zyp@dhu.edu.cn; Zhao Yingmei; Luo Jie; Shao Huili; Hu Xuechao

    2011-10-10

    To biomimic the spinning process of silkworm or spider, a capillary spinning equipment was applied to spin regenerated silk fibroin (RSF) fibers from RSF aqueous solutions in air. This equipment exhibits a wide processing window for various RSF aqueous solutions. The effects of pH, metal ions, RSF concentration and spinning parameters on the spinnability of the spinning dope and the mechanical properties of the obtained fibers were investigated. As a result, spinning dopes with a pH from 5.2 to 6.9 have good spinnability, especially for the dope with a pH of 6.0 and a Ca{sup 2+} concentration of 0.3 M. The RSF concentration of this dope ranges from 44% to 48%. Under optimized conditions of our dry spinning experiments (L/D, 133; take-up speed, 30 mm/s), the obtained as-spun fiber has a breaking strength of 46 MPa, which can be improved up to 359 MPa after a preliminary post-drawing in 80 vol.% ethanol aqueous solution. Highlights: {yields} Regenerated silk fibroin fibers were prepared by using a dry spinning method. {yields} Dope compositions affect dope spinnability. {yields} Spinning parameters affect dope spinnability and fiber properties. {yields} The breaking stress of the post-treated fiber was up to 359 MPa.