WorldWideScience

Sample records for aqueous solution formation

  1. 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

  2. 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.

  3. 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.``

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Aqueous Solution Preparation of Ruthenium Nanoparticles Using Ammonium Formate as the Reducing Agent

    Institute of Scientific and Technical Information of China (English)

    LIU Shaohong; CHEN Jialin; GUAN Weiming; BI Jun; CHEN Nanguang; CHEN Dengquan; LIU Manmen; SUN Xudong

    2012-01-01

    Ruthenium,one of the platinum group metals,has drawn much attention due to its catalytic behavior,hardness,electrical conductivity and density.Ruthenium particles are usually prepared on a small scale by the polyol process,however,the size of the obtained ruthenium nanoparticles is most below 10 nm.In this work,ruthenium particles about 200 nm in diameter were obtained in aqueous solution by using ammonium formate as the reducing agent.Tohave a better control of particle's size and shape,the effects of PVP,mixing mode,reaction temperature,solution pH and calcination temperature were investigated.

  9. Electrical conductivity study on micelle formation of long-chain imidazolium ionic liquids in aqueous solution.

    Science.gov (United States)

    Inoue, Tohru; Ebina, Hayato; Dong, Bin; Zheng, Liqiang

    2007-10-01

    Electrical conductivity was measured for aqueous solutions of long-chain imidazolium ionic liquids (IL), 1-alkyl-3-methylimidazolium bromides with C(12)-C(16) alkyl chains. The break points appeared in specific conductivity (kappa) vs concentration (c) plot indicates that the molecular aggregates, i.e., micelles, are formed in aqueous solutions of these IL species. The critical micelle concentration (cmc) determined from the kappa vs c plot is somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides with the same hydrocarbon chain length. The electrical conductivity data were analyzed according to the mixed electrolyte model of micellar solution, and the aggregation number, n, and the degree of counter ion binding, beta, were estimated. The n values of the present ILs are somewhat smaller than those reported for alkyltrimethylammonium bromides, which may be attributed to bulkiness of the cationic head group of the IL species. The thermodynamic parameters for micelle formation of the present ILs were estimated using the values of cmc and beta as a function of temperature. The contribution of entropy term to the micelle formation is superior to that of enthalpy term below about 30 degrees C, and it becomes opposite at higher temperature. This coincides with the picture drawn for the micelle formation of conventional ionic surfactants.

  10. Prediction of Gas Hydrate Formation Conditions in Aqueous Solutions of Single and Mixed Electrolytes

    DEFF Research Database (Denmark)

    Zuo, You-Xiang; Stenby, Erling Halfdan

    1997-01-01

    In this paper, the extended Patel-Teja equation of state was modified to describe non-ideality of the liquid phase containing water and electrolytes accurately. The modified Patel-Teja equation of state (MPT EOS) was utilized to develop a predictive method for gas hydrate equilibria. The new method...... employs the Barkan and Sheinin hydrate model for the description of the hydrate phase, the original Patel-Teja equation of state for the vapor phase fugacities, and the MPT EOS (instead of the activity coefficient model) for the activity of water in the aqueous phase. The new method has succesfully...... predicted the gas hydrate formation conditions in aqueous solutions of single and mixed electrolytes. The agreement between experimental data and predictions was found to be excellent....

  11. Determination of Gibbs energies of formation in aqueous solution using chemical engineering tools.

    Science.gov (United States)

    Toure, Oumar; Dussap, Claude-Gilles

    2016-08-01

    Standard Gibbs energies of formation are of primary importance in the field of biothermodynamics. In the absence of any directly measured values, thermodynamic calculations are required to determine the missing data. For several biochemical species, this study shows that the knowledge of the standard Gibbs energy of formation of the pure compounds (in the gaseous, solid or liquid states) enables to determine the corresponding standard Gibbs energies of formation in aqueous solutions. To do so, using chemical engineering tools (thermodynamic tables and a model enabling to predict activity coefficients, solvation Gibbs energies and pKa data), it becomes possible to determine the partial chemical potential of neutral and charged components in real metabolic conditions, even in concentrated mixtures.

  12. Formation of hydrated layers in PMMA thin films in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Akers, Peter W. [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); Nelson, Andrew R.J. [The Bragg Institute, Australian Nuclear Science and Technology Organisation, Menai, NSW (Australia); Williams, David E. [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington (New Zealand); McGillivray, Duncan J., E-mail: d.mcgillivray@auckland.ac.nz [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington (New Zealand)

    2015-10-30

    Graphical abstract: - Highlights: • Homogeneous thin PMMA films prepared on Si/SiOx substrates and measured in air and water. • Reproducible formation of highly hydrated layer containing 50% water at the PMMA/SiOx interface. • When heated the films swell at 50 °C without loss of material. • Upon re-cooling to 25 °C the surface roughens and material is lost. - Abstract: Neutron reflectometry (NR) measurements have been made on thin (70–150 Å) poly(methylmethacrylate) (PMMA) films on Si/SiOx substrates in aqueous conditions, and compared with parameters measured using ellipsometry and X-Ray reflectometry (XRR) on dry films. All techniques show that the thin films prepared using spin-coating techniques were uniform and had low roughness at both the silicon and subphase interfaces, and similar surface energetics to thicker PMMA films. In aqueous solution, NR measurements at 25 °C showed that PMMA forms a partially hydrated layer at the SiOx interface 10 Å under the film, while the bulk film remains intact and contains around 4% water. Both the PMMA film layer and the sublayer showed minimal swelling over a period of 24 h. At 50 °C, PMMA films in aqueous solution roughen and swell, without loss of PMMA material at the surface. After cooling back to 25 °C, swelling and roughening increases further, with loss of material from the PMMA layer.

  13. Speciation of phytate ion in aqueous solution. Alkali metal complex formation in different ionic media.

    Science.gov (United States)

    De Stefano, Concetta; Milea, Demetrio; Pettignano, Alberto; Sammartano, Silvio

    2003-08-01

    The acid-base properties of phytic acid [ myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H(12)Phy; Phy(12-)=phytate anion) were studied in aqueous solution by potentiometric measurements ([H+]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0iodide (Et(4)NI; e.g., at I=0.5 mol L(-1), log K(3)(H)=11.7, 8.0, 9.1, and 9.1 in Et(4)NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et(4)NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton-metal-ligand complexes, M(j)H(i)Phy((12-i-j)-), (M+ =Li+, Na+, K+), with jstability of alkali metal complexes follows the trend Li+ > or =Na+K+. Some measurements were also performed at constant ionic strength (I=0.5 mol L(-1)), using different mixtures of Et(4)NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal-proton-ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.

  14. Formation of hexamethylenetetramine by aqueous solutions of formaldehyde and ammonium sulfate

    Science.gov (United States)

    Rodriguez, A. A.; De Haan, D. O.; Kua, J.

    2012-12-01

    Formaldehyde and ammonium sulfate are prominent compounds found in cloudwater. Electronic structure calculations and lab experiments were carried out to explore the oligomerization reactions between formaldehyde and ammonia. Density functional theory calculations along with solvation and thermodynamic corrections were performed to map the kinetic and thermodynamic landscape for the reactions leading to the formation of hexamethylenetetramine (hmta). Three general classes of reactions were considered: nucleophilic addition of amine to formaldehyde, nucleophilic addition of ammonia to imine intermediates ammonia, and dehydration of alkanolamines. The reaction was studied experimentally using bulk-phase aqueous solutions of formaldehyde, ammonium sulfate, and in some experiments, iron (III) sulfate (chosen because Fe3+ forms a brown complex with hmta). Aqueous standard solutions of the reaction product hmta were also made. Reaction mixtures were analyzed using NMR, UV-Vis spectroscopy and LCMS. Compound hmta was the main product observed by both NMR and LCMS. Using LCMS a large peak was observed within minutes of mixing the reactants. The absorbance of the reaction mixture increased strongly below 225 nm but little to no absorbance was observed in the visible spectrum.

  15. Effect of common cryoprotectants on critical warming rates and ice formation in aqueous solutions.

    Science.gov (United States)

    Hopkins, Jesse B; Badeau, Ryan; Warkentin, Matthew; Thorne, Robert E

    2012-12-01

    Ice formation on warming is of comparable or greater importance to ice formation on cooling in determining survival of cryopreserved samples. Critical warming rates required for ice-free warming of vitrified aqueous solutions of glycerol, dimethyl sulfoxide, ethylene glycol, polyethylene glycol 200 and sucrose have been measured for warming rates of order 10-10⁴ K/s. Critical warming rates are typically one to three orders of magnitude larger than critical cooling rates. Warming rates vary strongly with cooling rates, perhaps due to the presence of small ice fractions in nominally vitrified samples. Critical warming and cooling rate data spanning orders of magnitude in rates provide rigorous tests of ice nucleation and growth models and their assumed input parameters. Current models with current best estimates for input parameters provide a reasonable account of critical warming rates for glycerol solutions at high concentrations/low rates, but overestimate both critical warming and cooling rates by orders of magnitude at lower concentrations and larger rates. In vitrification protocols, minimizing concentrations of potentially damaging cryoprotectants while minimizing ice formation will require ultrafast warming rates, as well as fast cooling rates to minimize the required warming rates.

  16. Photochemical Formation of Fe(II) in the Aqueous Solutions of Fe(III)- Dicarboxylates

    Science.gov (United States)

    Okada, K.; Arakaki, T.

    2007-12-01

    Although there have been many studies reporting the photochemical formation of Fe(II) in various aqueous-phase such as rain, cloud waters, seawater and aerosols, the detailed formation mechanisms are not well understood. To better understand the mechanisms of Fe(II) formation, we attempted to determine the molar absorptivity and the quantum yield of Fe(II) photoformation for individual Fe(III)-dicarboxylate species. The concentrations of Fe(II) and total dissolved Fe were measured by a Ferrozine-HPLC method. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of chemical species in the solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)- dicarboxylate complex can be analysed by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III) speciation to determine individual molar absorptivity and quantum yield of Fe(II) photoformation for a specific Fe(III)-dicarboxylate complex. Preliminary results, using an oxalate whose quantum yield has been previously reported, indicate that this approach gives lower quantum yield values in air saturated solutions than previously reported.

  17. Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution

    Science.gov (United States)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Skvortsov, I. A.; Korchagina, A. S.

    2016-09-01

    Heat effects of the dissolution of crystalline γ-aminobutyric acid in water and potassium hydroxide solutions are determined by direct colorimetry at 298.15 K. Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution are calculated.

  18. Supramolecular coordination chemistry in aqueous solution: lanthanide ion-induced triple helix formation.

    Science.gov (United States)

    Lessmann, J J; Horrocks, W D

    2000-07-24

    The self-assembly of dinuclear triple helical lanthanide ion complexes (helicates), in aqueous solution, is investigated utilizing laser-induced, lanthanide luminescence spectroscopy. A series of dinuclear lanthanide (III) helicates (Ln(III)) based on 2,6-pyridinedicarboxylic acid (dipicolinic acid, dpa) coordinating units was synthesized by linking two dpa moieties using the organic diamines (1R,2R)-diaminocyclohexane (chxn-R,R) and 4,4'-diaminodiphenylmethane (dpm). Luminescence excitation spectroscopy of the Eu3+ 7F0-->5D0 transition shows the apparent cooperative formation of neutral triple helical complexes in aqueous solution, with a [Eu2L3] stoichiometry. Eu3+ excitation peak wavelengths and excited-state lifetimes correspond to those of the [Eu(dpa)3]3- model complex. CD studies of the Nd(III) helicate Nd2(dpa-chxn-R,R)3 reveal optical activity of the f-f transitions, indicating that the chiral linking group induces a stable chirality at the metal ion center. Molecular mechanics calculations using CHARMm suggest that the delta delta configuration at the Nd3+ ion centers is induced by the chxn-R,R linker. Stability constants were determined for both ligands with Eu3+, yielding identical results: log K = 31.6 +/- 0.2 (K in units of M-4). Metal-metal distances calculated from Eu3+-->Nd3+ energy-transfer experiments show that the complexes have metal-metal distances close to those calculated by molecular modeling. The fine structure in the Tb3+ emission bands is consistent with the approximate D3 symmetry as anticipated for helicates.

  19. Chemical equilibrium of hydrogen and aqueous solutions of 1 : 1 bicarbonate and formate salts with a common cation

    NARCIS (Netherlands)

    Engel, D.C.; Versteeg, G.F.; Swaaij, W.P.M. van

    1997-01-01

    The chemical equilibrium of hydrogen and aqueous solutions of 1:1 bicarbonate and formate salts with a common cation has been investigated in an intensively stirred batch reactor: MHCO3(aq) + H2(aq) ↔ MOOCH(aq) + H2O(l) This was accomplished for the sodium (M = Na), potassium (M = K) and ammonium (M

  20. FLUORESCENCE SPECTROSCOPIC STUDY OF THE FORMATION OF HYDROPHOBIC MICRODOMAINS IN AQUEOUS-SOLUTIONS OF POLY(ALKYLMETHYLDIALLYLAMMONIUM BROMIDES)

    NARCIS (Netherlands)

    YANG, YJ; ENGBERTS, JBFN

    1991-01-01

    The conformational state of poly(alkylmethyldiallylammonium bromides) was studied in aqueous solutions using pyrene as a fluorescence probe. The results are indicative for the formation of hydrophobic microdomains in the case of several copolymers which possess sufficiently hydrophobic alkyl side ch

  1. EPR study of complex formation between copper (II) ions and sympathomimetic amines in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Preoteasa, E.A. [Inst. of Atomic Physics, IFIN, Bucharest (Romania); Duliu, O.G.; Grecu, V.V. [Bucharest, Univ. (Romania). Dept. of Atomic and Nuclear Physics

    1997-07-01

    The complex formation between sympathomimetic amines (SA): adrenaline (AD), noradrenaline (NA), dopamine (DA), ephedrine (ED) and p-tyramine (pTA), and Cu(II) ion in aqueous solution has been studied by X-band EPR at room temperature. Excepting pTA, all investigated SA yielded two types of complexes in different pH domains. All complexes consistent with a ligand fields having a distorted octahedral symmetry, i.e., hexacoordination of Cu(II). The covalence coefficient calculated from the isotropic g and A values has shown strong ionic sigma-type ligand bonds. A structural model with the Cu(II) ion bound by four catecholic O(hydroxy) atoms for the low pH complexes of AD, NA and DA is proposed. For the high pH complexes of the former compounds as well as for both Ed complexes, the authors suppose Cu(II) bound by two N (amino) and two O (hydroxy) atoms. The spectra are consistent to water binding on the longitudinal octahedron axis in all compounds excepting the high pH complex of Ed, where OH2- ions are bound. Possible implications for the SA-cell receptors interactions are discussed.

  2. Investigation into formation of nanoparticles of tetravalent neptunium in slightly alkaline aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Husar, Richard

    2015-08-20

    Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions. The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO{sub 3}){sub 5}]{sup 6-}) induces the intrinsic formation of nanocrystalline NpO{sub 2} in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group Fm anti 3m). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ζ ∝0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO{sub 2} nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm. Hitherto, unknown polynuclear species as intermediate species of NpO{sub 2} nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides

  3. Chemical dosimetry system for γ-ray irradiation based on the formation of phenol from aqueous benzene solutions.

    Science.gov (United States)

    Takeda, Kazuhiko

    2011-01-01

    A chemical dosimetry system based on the radiochemical formation of phenol from aqueous benzene solutions was applied to measure the intensity of γ-ray irradiation. Using a simple and sensitive isocratic fluorometric HPLC system, radiochemically generated phenol was determined. The radiochemical formation of phenol was linear up to 100 Gy and the lower limit of detection calculated from the detection limits of phenol was estimated to be 7 mGy. The phenol formation rates were not affected by the oxygen saturation. The chemical dosimetry system investigated in this study was sensitive and was easier to use than traditional chemical dosimeters.

  4. Complex formation of CdSe/ZnS/TOPO nanocrystal vs. molecular chaperone in aqueous solution by hydrophobic interaction

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Hiromi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan)]. E-mail: horihiro@cc.tuat.ac.jp; Iwami, Noriya [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Tachibana, Fumi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Ohtaki, Akashi [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Iizuka, Ryo [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Zako, Tamotsu [Bioengineering Laboratory, RIKEN - Institute of Physical and Chemical Research, 2-1, Hirosawa, Wako, Saitama 351-0198 (Japan); Oda, Masaru [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Yohda, Masafumi [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Tani, Toshiro [Department of Applied Physics, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan); Strategic Research Initiative for Future Nano-Science and Technology, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Kogane-i, Tokyo 184-8588 (Japan)

    2007-11-15

    Feasibilities to stabilize CdSe/ZnS/trioctylphosphineoxide (TOPO) nanocrystals (quantum dots, QDs) in aqueous solutions with prefoldin macromolecules in their bioactive states are reported. Prefoldin is a jellyfish-shaped hexameric co-chaperone of the group II chaperonins. As a protein folding intermediate is captured within its central cavity, so CdSe/ZnS/TOPO QDs would also be included within this cavity. It is also found the QDs can be much more dispersed in aqueous solutions and suspended for certain period of time by adding trace amount of t-butanol in the buffer prior to the mixing of the QDs mother solution. While biochemical procedures are evaluated with ordinary fluorescence measurements, possible complex formations are also evaluated with TIRFM single-molecule detection techniques.

  5. Controlling ZIF-67 crystals formation through various cobalt sources in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiangli [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China); Xing, Tiantian [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Lou, Yongbing [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China); Chen, Jinxi, E-mail: chenjinxi@seu.edu.cn [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China)

    2016-03-15

    Zeolitic imidazolate frameworks ZIF-67 were prepared under hydrothermal (120 °C) and non-hydrothermal (room temperature) from various cobalt sources and 2-methylimidazolate (Hmim) in aqueous solution within 30 min. The particle size and morphology were found to be related to the reactivity of the cobalt salt, Hmim/Co{sup 2+} molar ratios and experimental condition. Using Co(NO{sub 3}){sub 2} as cobalt source, small-sized ZIF-67 crystals with agglomeration were formed. For CoCl{sub 2}, small-sized rhombic dodecahedron were obtained. While large-sized crystals of rhombic dodecahedron structure were obtained from CoSO{sub 4} and Co(OAc){sub 2}. Under hydrothermal condition, the size of ZIF-67 crystals tended to be more uniform and the morphology were more regular comparing to non-hydrothermal condition. This study provides a simple way to control the size and morphology of ZIF-67 crystals prepared in aqueous solution. - Graphical abstract: Zeolitic imidazolate frameworks ZIF-67 were prepared under hydrothermal (120 °C) and non-hydrothermal (room temperature) from four different cobalt sources (Co(NO{sub 3}){sub 2}, CoCl{sub 2}, CoSO{sub 4} and Co(OAc){sub 2}) in aqueous solution within 30 min. The particle size and morphology were found to be related to the reactivity of the cobalt salt, Hmim/Co{sup 2+} molar ratios and experimental condition. - Highlights: • The particle size and morphology were determined by the reactivity of cobalt salt. • ZIF-67 could be prepared from CoSO{sub 4} and Co(OAc){sub 2} at Hmim/Co{sup 2+} molar ratio of 10. • Uniform and regular particles were obtained under hydrothermal condition.

  6. Alkyl propoxy ethoxylate "graded" surfactants: micelle formation and structure in aqueous solutions.

    Science.gov (United States)

    Sarkar, Biswajit; Alexandridis, Paschalis

    2010-04-08

    The self-assembly of alkyl propoxy ethoxylate surfactants in aqueous solutions has been investigated with a focus on the (i) thermodynamics of micellization (critical micellization concentration; free energy, enthalpy, and entropy of micellization) and (ii) structure of the micelles (overall shape and size; local environment in the micelle core and corona) as affected by the surfactant composition (variation of degree of ethoxylation). The various results are compared to those for alkyl ethoxylate and poly(ethylene oxide)-b-poly(propylene oxide) amphiphiles with the aim to elucidate the role of the middle, propoxy, block in the novel alkyl propoxy ethoxylate surfactants which exhibit a "graded" hydrophobic-hydrophilic character.

  7. 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

  8. Radiolytic formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manmohan [Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)]. E-mail: manmoku@magnum.barc.ernet.in; Varshney, Lalit [Radiation Technology Development Section, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Francis, Sanju [Radiation Technology Development Section, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2005-05-01

    Ag{sup +} ions, in aqueous polyvinyl alcohol (PVA) solution and in PVA hydrogel matrix have been gamma radiolytically reduced to produce Ag clusters. UV-visible absorption spectral characteristics of Ag clusters obtained under different gamma dose, Ag{sup +} concentration, PVA concentration and crosslinking density of the gel used have been studied. The effect of Ag{sup +} ions on the radiation crosslinking of the PVA chains, have also been investigated by viscosity measurements. The radiation-induced Ag{sup +} ion reduction was followed by crosslinking of the PVA chains. PVA was found to be a very efficient stabilizer to prevent aggregation of Ag clusters. The clusters produced in the hydrogel matrix were expected to be smaller than the pore size ({approx}2-20 nm) of the gels used in the study. These Ag clusters were unable to reduce methyl viologen (MV{sup 2+}) chloride and were stable in air.

  9. Radiolytic formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix

    Science.gov (United States)

    Kumar, Manmohan; Varshney, Lalit; Francis, Sanju

    2005-05-01

    Ag+ ions, in aqueous polyvinyl alcohol (PVA) solution and in PVA hydrogel matrix have been gamma radiolytically reduced to produce Ag clusters. UV-visible absorption spectral characteristics of Ag clusters obtained under different gamma dose, Ag+ concentration, PVA concentration and crosslinking density of the gel used have been studied. The effect of Ag+ ions on the radiation crosslinking of the PVA chains, have also been investigated by viscosity measurements. The radiation-induced Ag+ ion reduction was followed by crosslinking of the PVA chains. PVA was found to be a very efficient stabilizer to prevent aggregation of Ag clusters. The clusters produced in the hydrogel matrix were expected to be smaller than the pore size (∼2-20 nm) of the gels used in the study. These Ag clusters were unable to reduce methyl viologen (MV2+) chloride and were stable in air.

  10. Wet etching of InSb surfaces in aqueous solutions: Controlled oxide formation

    Energy Technology Data Exchange (ETDEWEB)

    Aureau, D., E-mail: damien.aureau@chimie.uvsq.fr [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France); Chaghi, R.; Gerard, I. [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France); Sik, H.; Fleury, J. [Sagem Defense Sécurité, 72-74, rue de la tour Billy, 95101, Argenteuil Cedex (France); Etcheberry, A. [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France)

    2013-07-01

    This paper investigates the wet etching of InSb surfaces by two different oxidant agents: Br{sub 2} and H{sub 2}O{sub 2} and the consecutive oxides generation onto the surfaces. The strong dependence between the chemical composition of the etching baths and the nature of the final surface chemistry of this low band-gap III–V semiconductor will be especially highlighted. One aqueous etching solution combined hydrobromic acid and Bromine (HBr–Br{sub 2}:H{sub 2}O) with adjusted concentrations. The other solution combines orthophosphoric and citric acids with hydrogen peroxide (H{sub 3}PO{sub 4}–H{sub 2}O{sub 2}:H{sub 2}O). Depending on its composition, each formulation gave rise to variable etching rate. The dosage of Indium traces in the etching solution by atomic absorption spectroscopy (AAS) gives the kinetic variation of the dissolution process. The variations on etching rates are associated to the properties and the nature of the formed oxides on InSb surfaces. Surface characterization is specifically performed by X-ray photoelectron spectroscopy (XPS). A clear evidence of the differences between the formed oxides is highlighted. Atomic force microscopy is used to monitor the surface morphology and pointed out that very different final morphologies can be reached. This paper presents new results on the strong variability of the InSb oxides in relation with the InSb reactivity toward environment interaction.

  11. Dynamics of Magnesite Formation at Low-Temperature and High pCO2 in Aqueous Solution

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Odeta; Dixon, David A.; Rosso, Kevin M.; Schaef, Herbert T.; Bowden, Mark E.; Arey, Bruce W.; Felmy, Andrew R.

    2015-09-17

    Like many metal carbonate minerals, despite conditions of supersaturation, precipitation of magnesite from aqueous solution is kinetically hindered at low temperatures, for reasons that remain poorly understood. The present study examines precipitation products from reaction of Mg(OH)2 in aqueous solutions saturated with supercritical CO2 at high pressures (90 atm and 110 atm) and low temperatures (35 °C and 50 °C). Traditional bulk characterization (X-ray diffraction) of the initial solid formed indicated the presence of hydrated magnesium carbonates (hydromagnesite and nesquehonite), thermodynamically metastable phases that were found to slowly react during ageing to the more stable anhydrous form, magnesite, at temperatures as low as 35 °C (135-140 days) and at a faster rate at 50 °C (56 days). Undetected by bulk measurements, detailed examination of the precipitates by scanning electron microscopy (SEM) showed that magnesite is present as a minor component at relatively early reaction times (7 days) at 50 °C. In addition to magnesite dominating the solid phases over time, we find that mangesite nucleation and growth occurs more quickly with increasing partial pressure of CO2, and in electrolyte solutions with high bicarbonate content. Furthermore, formation of magnesite was found to be enhanced in sulfate-rich solutions, compared to chloride-rich solutions. We speculate that much of this behavior is possibly due to sulfate serving as sink of protons generated during carbonation reactions. These results support the importance of integrating magnesite as an equilibrium phase in reactive transport calculations of the effects of carbon dioxide sequestration on subsurface formations at long time scales.

  12. Diketopiperazine-mediated peptide formation in aqueous solution II. Catalytic effect of phosphate

    Science.gov (United States)

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

    1991-05-01

    The previous paper (I) reported that DKP (glycine anhydride) spontaneously reacts with glycine (Gly) or oligoglycines (Gly n ) to produce longer oligoglycines (Gly n+2). This paper presents that phosphate catalyzes the condensation reaction quite effectively. Formation of Gly4 from DKP (0.1 M) and Gly2 (0.1 M) in phosphate solution of various concentrations was investigated at a neutral pH at 41 °C. The yields of Gly4 increased almost linearly with the concentration of phosphate from 0.06 M to 0.24 M. The yield in 0.24 M phosphate solution was approximately one hundred times as high as that in the absence of the phosphate, whereas in the case of Gly3 formation from DKP and Gly the effect of the phosphate was of ten times lower than in the former case. Orthophosphate was the most effective catalyst among the various kind of chemicals tried in the present investigation including polyphosphates.

  13. Thermodynamics of the formation of complexes of copper(II) ions and glycylglycine in aqueous solutions at 298 K according to calorimetry data

    Science.gov (United States)

    Kochergina, L. A.; Emel'yanov, A. V.

    2015-04-01

    Heat effects of the interaction between glycylglycine and copper(II) nitrate solutions are measured by direct calorimetry at a [metal] : [ligand] ratio of 1 : 5 and at different pH values of the solution. The measurements are made at a temperature of 298.15 K and ionic strengths of 0.25, 0.50, and 0.75. KNO3 is used as a background electrolyte. The thermodynamic characteristics of complex formation by the peptide and copper(II) ions in aqueous solutions are determined. Standard enthalpies of the formation of complex particles in aqueous solutions are calculated.

  14. A systematic investigation and insight into the formation mechanism of bilayers of fatty acid/soap mixtures in aqueous solutions.

    Science.gov (United States)

    Xu, Wenlong; Song, Aixin; Dong, Shuli; Chen, Jingfei; Hao, Jingcheng

    2013-10-08

    Vesicles are the most common form of bilayer structures in fatty acid/soap mixtures in aqueous solutions; however, a peculiar bilayer structure called a "planar sheet" was found for the first time in the mixtures. In the past few decades, considerable research has focused on the formation theory of bilayers in fatty acid/soap mixtures. The hydrogen bond theory has been widely accepted by scientists to explain the formation of bilayers. However, except for the hydrogen bond, no other driving forces were proposed systematically. In this work, three kinds of weak interactions were investigated in detail, which could perfectly demonstrate the formation mechanism of bilayer structures in the fatty acid/soap mixtures in aqueous solutions. (i) The influence of hydrophobic interaction was detected by changing the chain length of fatty acid (C(n)H(2n+1)COOH), in which n = 10 to 18, the phase behavior was investigated, and the phase region was presented. With the help of cryogenic transmission electron microscopy (cryo-TEM) observations, deuterium nuclear magnetic resonance ((2)H NMR), and X-ray diffraction (XRD) measurements, the vesicles and planar sheets were determined. The chain length of C(n)H(2n+1)COOH has an important effect on the physical state of the hydrophobic chain, resulting in an obvious difference in the viscoelasticity of the solution samples. (ii) The existence of hydrogen bonds between fatty acids and their soaps in aqueous solutions was demonstrated by Fourier transform infrared (FT-IR) spectroscopy and molecule dynamical simulation. From the pH measurements, the pH ranges of the bilayer formation were at the pKa values of fatty acids, respectively. (iii) Counterions can be embedded in the stern layer of the bilayers and screen the electrostatic repulsion between the COO(-) anionic headgroups. FT-IR characterization demonstrated a bidentate bridging coordination mode between counterions and carboxylates. The conductivity measurements provided the degree

  15. Formation of hydrotalcite in aqueous solutions and intercalation of ATP by anion exchange.

    Science.gov (United States)

    Tamura, Hiroki; Chiba, Jun; Ito, Masahiro; Takeda, Takashi; Kikkawa, Shinichi; Mawatari, Yasuteru; Tabata, Masayoshi

    2006-08-15

    The formation reaction and the intercalation of adenosine triphosphate (ATP) were studied for hydrotalcite (HT), a layered double hydroxide (LDH) of magnesium and aluminum. Hydrotalcite with nitrate ions in the interlayer (HT-NO(3)) was formed (A) by dropwise addition of a solution of magnesium and aluminum nitrates (pH ca. 3) to a sodium hydroxide solution (pH ca. 14) until the pH decreased from 14 to 10 and (B) by dropwise addition of the NaOH solution to the solution of magnesium and aluminum nitrates with pH increasing from 3 to 10. The precipitate obtained with method B was contaminated with aluminum hydroxide and the crystallinity of the product was low, possibly because aluminum hydroxide precipitates at pH 4 or 5 and remains even after HT-NO(3) forms at pH above 8. With method A, however, the precipitate was pure HT-NO(3) with increased crystallinity, since the solubility of aluminum hydroxide at pH above and around 10 is high as dissolved aluminate anions are stable in this high pH region, and there was no aluminum hydroxide contamination. The formed HT-NO(3) had a composition of [Mg(0.71)Al(0.29)(OH)(2)](NO(3))(0.29).0.58H(2)O. To intercalate ATP anions into the HT-NO(3), HT-NO(3) was dispersed in an ATP solution at pH 7. It was found that the interlayer nitrate ions were completely exchanged with ATP anions by ion exchange, and the interlayer distance expanded almost twice with a free space distance of 1.2 nm. The composition of HT-ATP was established as [Mg(0.68)Al(0.32)(OH)(2)](ATP)(0.080)0.88H(2)O. The increased distance could be explained with a calculated molecular configuration of the ATP as follows: An ATP molecule is bound to an interlayer surface with the triphosphate group, the adenosine group bends owing to its bond angles and projects into the interlayer to a height of 1 nm, and the adenosine groups aligned in the interlayer support the interlayer distance.

  16. Isobaric Heat Capacities of Micelle Formation by 1-Methyl-4-n-dodecylpyridinium Iodide in Aqueous Solution; Effects of Added Urea

    NARCIS (Netherlands)

    Posthumus, Willem; Engberts, Jan B.F.N.; Bijma, Koos; Blandamer, Michael J.

    1997-01-01

    Over the temperature range from 303 to 333 K, the enthalpy of micelle formation by 1-methyl-4-n-dodecylpyridinium iodide in aqueous solution is exothermic, characterised by an isobaric heat capacity of micelle formation equal to -439 ± 10 J K-1 mol-1. At 303 K, the critical micellar concentration (2

  17. Formation and decay of the peroxy radicals in the oxidation process of Glyoxal, Methylglyoxal and Hydroxyacetone in aqueous solution

    Science.gov (United States)

    Schaefer, Thomas; Weller, Christian; Herrmann, Hartmut

    2013-04-01

    Volatile organic compounds (VOCs) are emitted into the atmosphere in large amounts from biogenic and anthropogenic sources. For example, the semivolatile carbonyl compounds glyoxal and methylglyoxal will be produced in the oxidation process of isoprene, while hydroxyacetone can be formed by the combustion of biomass. Additionally, these semivolatile carbonyl compounds might be important for the formation of secondary organic aerosol (SOA) by partitioning between gas- and liquid phase of pre-existing particles. In the gas phase as well as in the aqueous phase (cloud droplets, fog, rain and deliquescent particles) these compounds can be further oxidized, e.g., by radicals (OH and NO3) leading to peroxy radical and then to substitued organics. There are still uncertainties concerning the oxidation pathways of glyoxal, after H-atom abstraction by, e.g., OH radicals, via alkyl radical to the peroxy radical under addition of molecular oxygen. One concept[1] claims that for dilute solutions ( 1 mM the formation of the peroxy radicals is a minor reaction pathway because of a lower rate constant of k = 1 × 106 M-1 s-1 estimated after Guzman et al., 2006[3]. The difference in the rate constants of the oxygen addition is of about three orders of magnitude and thus leads to different oxidation products and yields in the aqueous solution. Laboratory studies of glyoxal oxidation under varying oxygen concentrations have been performed in order to investigate the importance of the peroxy radical formation and alkyl radical recombination in more detail. The formation and the decay of the formed glyoxyl radicals and glyoxyl peroxy radicals were studied in low and high concentrated oxygen solutions using a laser photolysis long path absorption setup (LP-LPA). Additionally, the Tdependent decay of the peroxy radicals formed in the oxidation of methyglyoxal and hydroxyacetone was also studied using the same experiment. 1 Buxton, G. V., Malone, T. N. und Salmon, G. A., J. Chem. Soc

  18. Salt-induced vesicle formation from single anionic surfactant SDBS and its mixture with LSB in aqueous solution.

    Science.gov (United States)

    Zhai, Limin; Zhao, Mei; Sun, Dejun; Hao, Jingcheng; Zhang, Lungjun

    2005-03-31

    Vesicles can be formed spontaneously in aqueous solution of a single anionic surfactant sodium dodecyl benzenesulfonate (SDBS) just under the inducement of salt, which makes the formation of vesicle much easier and simpler. The existence of vesicles was demonstrated by TEM image using the negative-staining method. The mechanism of the formation may be attributed to the compression of salt on the electric bilayer of the surfactant headgroups, which alters the packing parameter of the surfactant. The addition of the zwitterionic surfactant lauryl sulfonate betaine (LSB) makes the vesicles more stable, expands the range of formation and vesicle size, and reduces the polydispersity of the vesicles. The vesicle region was presented in a pseudoternary diagram of SDBS/LSB/brine. The variations of vesicle size with the salinity and mixing ratios, as well as the surfactant concentration, were determined using the dynamic light scattering method. It is found that the vesicle size is independent of the surfactant concentration but subject to the salinity and the mixing ratio of the two surfactants.

  19. The formation of magnetic carboxymethyl-dextrane-coated iron-oxide nanoparticles using precipitation from an aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Makovec, Darko [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Gyergyek, Sašo, E-mail: saso.gyergyek@ijs.si [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Primc, Darinka [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Plantan, Ivan [Lek Pharmaceuticals d.d., Mengeš (Slovenia)

    2015-03-01

    The formation of spinel iron-oxide nanoparticles during the co-precipitation of Fe{sup 3+}/Fe{sup 2+} ions from an aqueous solution in the presence of carboxymethyldextrane (CMD) was studied. To follow the formation of the nanoparticles, a mixture of the Fe ions, CMD and ammonia was heated to different temperatures, while the samples were taken, quenched in liquid nitrogen, freeze-dried and characterized using transmission electron microscopy (TEM), X-ray diffractometry (XRD) and magnetometry. The CMD plays a role in the reactions of the Fe ions' precipitation by partially immobilizing the Fe{sup 3+} ions into a complex. At room temperature, the amorphous material is precipitated. Then, above approximately 30 °C, the spinel nanoparticles form inside the amorphous matrix, and at approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles. The CMD bonded to the nanoparticles' surfaces hinders the mass transport and thus prevents their growth. - Highlights: • The carboxymethyl-dextrane coated iron-oxide nanoparticles were synthesized. • The carboxymethyl-dextrane significantly modifies formation of the spinel nanoparticles. • The spinel nanoparticles are formed inside the amorphous matrix. • At approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles.

  20. Formation of cerussite and hydrocerussite during adsorption of lead from aqueous solution on oxidized carbons by cold oxygen plasma

    Energy Technology Data Exchange (ETDEWEB)

    De Velasco Maldonado, Paola S. [Instituto Tecnologico de Aguascalientes, Av. Adolfo López Mateos No. 1801 Ote. C.P, Aguascalientes, Ags, 20256 (Mexico); Hernández-Montoya, Virginia, E-mail: virginia.hernandez@yahoo.com.mx [Instituto Tecnologico de Aguascalientes, Av. Adolfo López Mateos No. 1801 Ote. C.P, Aguascalientes, Ags, 20256 (Mexico); Concheso, A.; Montes-Morán, Miguel A. [Instituto Nacional del Carbon, INCAR-CSIC, Apartado 73, E-33080, Oviedo (Spain)

    2016-11-15

    Highlights: • The formation of cerussite and hydrocerussite was observed on the carbon surface. • Occurrence of CaCO{sub 3} on the carbons surface plays a crucial role in the formation. • The carbons were prepared by carbonization and oxidation with cold oxygen plasma. • Oxidation with cold oxygen plasma increases the formation of these compounds. - Abstract: A new procedure of elimination of Pb{sup 2+} from aqueous solution using carbon adsorbents, in which high amounts of cerussite and hydrocerussite are deposited on the carbon surfaces, is reported. The procedure includes the preparation of carbons from selected lignocellulosic wastes (pecan nut shells and peach stones) by single carbonization and further oxidation with cold oxygen plasma. The materials prior and after the oxidation treatment were characterized using elemental analysis, FT-IR spectroscopy, SEM/EDX analysis, adsorption of N{sub 2} at −196 °C and X-ray photoelectron spectroscopy. The adsorption of Pb{sup 2+} was carried out in batch systems under constant agitation. The formation of cerussite and hydrocerussite on the spent carbon surfaces was confirmed by XRD, SEM/EDX and FT-IR. A Pb{sup 2+} removal mechanism is proposed in which a co-precipitation of lead nitrate and calcium carbonate would render the formation of the lead carbonates. In such mechanism, the occurrence of CaCO{sub 3} on the surface of the adsorbents plays a crucial role. The presence of calcium carbonate on the precursors is understood on the basis of the thermal evolution of calcium oxalate originally present in the biomass. The oxygen plasma treatment helps to expose the calcium carbonate nanocrystals thus improving dramatically the removal capacity of Pb{sup 2+}. Accordingly, retention capacities as high as 63 mg of Pb{sup 2+} per gram of adsorbent have been attained.

  1. Investigation of complex formation processes of hydroxypropylmethylcellulose and polymethacrylic acid in aqueous solutions

    Directory of Open Access Journals (Sweden)

    M. Katayeva

    2012-12-01

    Full Text Available The complex formation process of hydroxypropylcellulose (HPC with polymethacrylic acid (PMA have been studied using methods of turbidimetric and viscosimetric titration. Position of maximum depending on polymer concentration and molecular mass of polysaccharide have different values.

  2. Formation of cerussite and hydrocerussite during adsorption of lead from aqueous solution on oxidized carbons by cold oxygen plasma

    Science.gov (United States)

    De Velasco Maldonado, Paola S.; Hernández-Montoya, Virginia; Concheso, A.; Montes-Morán, Miguel A.

    2016-11-01

    A new procedure of elimination of Pb2+ from aqueous solution using carbon adsorbents, in which high amounts of cerussite and hydrocerussite are deposited on the carbon surfaces, is reported. The procedure includes the preparation of carbons from selected lignocellulosic wastes (pecan nut shells and peach stones) by single carbonization and further oxidation with cold oxygen plasma. The materials prior and after the oxidation treatment were characterized using elemental analysis, FT-IR spectroscopy, SEM/EDX analysis, adsorption of N2 at -196 °C and X-ray photoelectron spectroscopy. The adsorption of Pb2+ was carried out in batch systems under constant agitation. The formation of cerussite and hydrocerussite on the spent carbon surfaces was confirmed by XRD, SEM/EDX and FT-IR. A Pb2+ removal mechanism is proposed in which a co-precipitation of lead nitrate and calcium carbonate would render the formation of the lead carbonates. In such mechanism, the occurrence of CaCO3 on the surface of the adsorbents plays a crucial role. The presence of calcium carbonate on the precursors is understood on the basis of the thermal evolution of calcium oxalate originally present in the biomass. The oxygen plasma treatment helps to expose the calcium carbonate nanocrystals thus improving dramatically the removal capacity of Pb2+. Accordingly, retention capacities as high as 63 mg of Pb2+ per gram of adsorbent have been attained.

  3. Ion pair formation in copper sulfate aqueous solutions at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mendez De Leo, Lucila P. [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina); Escuela de Ciencia y Tecnologia, Universidad Nacional General San Martin, Alem 3901, 1653 Villa Ballester (Argentina); Bianchi, Hugo L. [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina); Escuela de Ciencia y Tecnologia, Universidad Nacional General San Martin, Alem 3901, 1653 Villa Ballester (Argentina); Fernandez-Prini, Roberto [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina) and INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, 1428 Ciudad de Buenos Aires (Argentina)]. E-mail: rfprini@cnea.gov.ar

    2005-05-15

    Ionic association between Cu{sup 2+}(aq) and SO42-(aq) has been studied in the temperature range (298 to 473) K using a spectrophotometric technique. Experiments were designed to minimize the contribution of other protolytic equilibria in solution. The values of the ionic association equilibrium constant at different temperatures and pressures were fitted to an appropriate equation that allows the calculation of the thermodynamic quantities for states close to the saturation line. Using Bjerrum's model for ionic association evidence for two ion pair populations was obtained. The process of ion pairing is discussed and a possibility to reconcile the continuum model (Bjerrum) with molecular simulation results is suggested.

  4. Time-resolved in situ Studies of Apatite Formation in Aqueous Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Borkiewicz, O.; Rakovan, J; Cahill, C

    2010-01-01

    Formation of hydroxylapatite through the precipitation and evolution of calcium phosphate precursor phases under varying conditions of temperature (25-90 C), pH (6.5-9.0), and calcium to phosphorus ratio (1.0, 1.33, 1.5, and 1.67) comparable to those found in many sediments and soils were studied. The products of low-temperature precipitation were analyzed by ex situ X-ray diffraction and SEM, as well as time-resolved in situ synchrotron X-ray diffraction. Rietveld refinement was used for quantitative evaluation of relative abundances during phase evolution. The results of ex situ investigations conducted at ambient temperature and near-neutral pH indicate formation of amorphous calcium phosphate, which over the course of experiments transforms to brushite and ultimately hydroxylapatite. The results of in situ X-ray diffraction experiments suggest a more complex pathway of phase development under the same conditions. Some of the initially formed amorphous calcium phosphate and/or crystalline brushite transformed to octacalcium phosphate. In the later stage of the reactions, octacalcium phosphate transforms quite rapidly to hydroxylapatite. This is accompanied or followed by the transformation of the remaining brushite to monetite. Hydroxylapatite and monetite coexist in the sample throughout the remainder of the experiments. In contrast to the near-neutral pH experiments, the results from ex situ and in situ diffraction investigations performed at higher pH yield similar results. The precipitate formed in the initial stages in both types of experiments was identified as amorphous calcium phosphate, which over the course of the reaction quite rapidly transformed to hydroxylapatite without any apparent intermediate phases. This is the first application of time-resolved in situ synchrotron X-ray diffraction to precipitation reactions in the Ca(OH){sub 2}-H{sub 3}PO{sub 4}-H{sub 2}O system. The results indicate that precursors are likely to occur during the natural or

  5. Formation Equilibria of Ternary Metal Complexes with Citric Acid and Glutamine (Alanine) in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    王进平; 牛春吉; 杨魁跃; 倪嘉缵

    2004-01-01

    The species and their formation constants in the ternary systems were obtained by the Scogs2 software from potentiometric titration data. The Comics software was used to calculate the distribution of species in the ternary systems. MLXH, MLXH2 and MLXH3 are the common species in these systems. The coordination behaviors of the rare earths are very similar and their stability is closely matched. The ternary rare earth complexes are more stable than the corresponding ternary complexes of calcium. The ternary zinc complex with glutamine as the secondary ligand is more stable than the corresponding complexes of rare earths, but the ternary complex with alanine as the secondary ligand shows an inverse trend. The distributions of species in the ternary systems vary with pH changing. A prediction can be made that exogenous rare earths can affect the species of Ca and Zn in human body.

  6. Arylperoxyl radicals. Formation, absorption spectra, and reactivity in aqueous alcohol solutions

    Energy Technology Data Exchange (ETDEWEB)

    Alfassi, Z.B.; Khaikin, G.I.; Neta, P. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

    1995-01-05

    Aryl radicals (phenyl, 4-biphenylyl, 2-naphthyl, 1-naphthyl, and 9-phenanthryl) were produced by the reaction of the corresponding aryl bromide with solvated electrons and reacted rapidly with oxygen to produce the arylperoxyl radicals. These radicals exhibit optical absorptions in the visible range, with [lambda][sub max] at 470, 550, 575, 650, and 700 nm, respectively. Arylperoxyl radicals react with 2,2[prime]-azinobis(3-ethylbenzothiazoiine-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation products as a function of substrate concentration, vary between 4 [times] 10[sup 6] and 2 [times] 10[sup 9] L mol[sup [minus]1] s[sup [minus]1] and increase in the order phenyl-, 4-biphenyl-, 2-naphthyl-, 1-naphthyl-, and 9-phenanthrylperoxyl, the same order as the absorption peaks of these radicals. Good correlation was found between log k and the energy of the absorption peak. 16 refs., 2 figs., 2 tabs.

  7. The Aggregation Behavior and Formation of Nanoparticles of Oleoylchitosan in Dilute Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    LI Yanyan; CHEN Xiguang; SUN Gangzheng; XING Ke

    2008-01-01

    Oleoylchitosans (O-chitosans) with different degrees of substitution (DS) were synthesized by reacting chitosan with oleoyl chloride. The chemical structures of the products were characterized by 1H NMR and FT-IR. These results suggested the for-mation of an amide linkage between the amino groups of chitosan and the carboxyl groups of oleic acid. The viscosity of O-chitosan sharply increased with the increase of concentration, whereas that of unmodified chitosan rose only slightly. This increase became larger as the DS increased. All of the O-chitosans could reduce surface tension slightly. The critical aggregation concentration (CAC) of O-chitosans with DS 5%, 11%, and 27% were 79.43 mgL-1, 31.6 mgL-1, and 10mgL-1, respectively. Nanoparticles were prepared using an O/W emulsification method. The mean diameters of the polymeric amphiphilic nanoparticles of O-chitosans with DS 5% and 11% were around 327.4 nm and 275.3 nm, respectively.

  8. Silver nanocombs and branched nanowires formation in aqueous binary surfactants solution

    Energy Technology Data Exchange (ETDEWEB)

    Umar, Akrajas Ali, E-mail: akrajas@ukm.my [Universiti Kebangsaan Malaysia, Institute of Microengineering and Nanoelectronics (Malaysia); Oyama, Munetaka [Kyoto University, Department of Materials Chemistry, Graduate School of Engineering (Japan); Salleh, Muhamad Mat; Majlis, Burhanuddin Yeop [Universiti Kebangsaan Malaysia, Institute of Microengineering and Nanoelectronics (Malaysia)

    2012-07-15

    Branched nanocrystals, particularly nanocombs, are a unique 1D-morphology that is normally formed in polytypic materials, such as ZnO, and rarely occurs in the highly symmetric fcc metallic system. Here, we report the chemical synthesis of nanocombs of a highly symmetrical fcc silver system that is realized by reducing the silver ions in the presence of a mixture of silver nanoseeds and binary surfactants, namely cetyltrimethylammonium bromide (CTAB) and hexamethylenetetramine (hexamine or HMT), under an alkaline condition. The silver nanocombs feature a high-degree branching orientation toward a single direction with good branch-to-branch spacing. The nanocombs formation was very sensitive to the concentrations of CTAB, HMT and NaOH in the reaction in which, in a typical case, nanocombs or curly nanowires were produced by controlling the concentration of these chemicals in the reaction. We hypothesized that the branching could be due to: (i) a kind of polytypism in such highly symmetrical fcc nanocrystals that was enabled by a selective surfactant adhesion process on the growing crystalline plane and (ii) lattice defects or twinning induced growth redirection in the nanocrystals. The silver nanocombs might generate a peculiar characteristic that is probably superior to those produced by other morphologies, such as nanorods, nanowires, and so on. Thus, it should find extensive use in the currently existing applications.

  9. Hydroxyl radical-induced crosslinking and radiation-initiated hydrogel formation in dilute aqueous solutions of carboxymethylcellulose.

    Science.gov (United States)

    Wach, Radoslaw A; Rokita, Bozena; Bartoszek, Nina; Katsumura, Yosuke; Ulanski, Piotr; Rosiak, Janusz M

    2014-11-04

    Ionizing radiation causes chain scission of polysaccharides in the absence of crosslinking agents. It has been demonstrated before that degradation of carboxyalkylated polysaccharides may be prevented, despite presence of strong electrostatic repulsing forces between chains, at very high polymer concentration in water (paste-like state) when physical proximity promotes recombination of radiation-generated polymer radicals. In such conditions, crosslinking dominates over chain scission and covalent, macroscopic gels can be formed. In an approach proposed in this work, neutralizing the charges on carboxymethylcellulose (CMC) by lowering the pH results in retracting the electrostatic repulsion between chain segments and thus allows for substantial reduction of polymer concentration required to achieve gelation due to domination of crosslinking reactions. Electron-beam irradiation of aqueous solutions of low pH containing 0.5-2% CMC results in hydrogel formation with 70% yield, while both concentration and dose determine their swelling properties. Time-resolved studies by laser flash photolysis clearly indicate strong pH influence on decay kinetics of CMC radicals.

  10. Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

    Science.gov (United States)

    Rudolph, Wolfram W; Irmer, Gert

    2015-01-01

    Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121-3.050 mol L(-1)) range at room temperature (23 °C). A very weak mode at 343 cm(-1) with a full width at half height at 49 cm(-1) in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La(3+) nona-hydrate was also detected in a 1.2 mol L(-1) La(CF3SO3)3(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5-3.050 mol L(-1). The chloro-complexes in LaCl3(aq) are fairly weak and disappear with dilution. At a concentration complexes disappeared. In LaCl3 solutions, with additional HCl, a series of chloro-complexes of the type [La(OH2)(9-n)Cln](+3-n) (n = 1-3) were formed. The La(NO3)3(aq) spectra were compared with a spectrum of a 0.409 mol L(-1) NaNO3(aq) and it was concluded that in La(NO3)3(aq) over the concentration range from 0.121-1.844 mol L(-1), nitrato-complexes, [La(OH2)(9-n)(NO3)n](+3-n) (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution La(OH2)9](3+) with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La-O stretching mode at 328.2 cm(-1), is only slightly smaller than the experimental one.

  11. Ion-pair formation in aqueous strontium chloride and strontium hydroxide solutions under hydrothermal conditions by AC conductivity measurements.

    Science.gov (United States)

    Arcis, H; Zimmerman, G H; Tremaine, P R

    2014-09-01

    Frequency-dependent electrical conductivities of solutions of aqueous strontium hydroxide and strontium chloride have been measured from T = 295 K to T = 625 K at p = 20 MPa, over a very wide range of ionic strength (3 × 10(-5) to 0.2 mol kg(-1)), using a high-precision flow AC conductivity instrument. Experimental values for the concentration-dependent equivalent conductivity, Λ, of the two electrolytes were fitted with the Turq-Blum-Bernard-Kunz ("TBBK") ionic conductivity model, to determine ionic association constants, K(A,m). The TBBK fits yielded statistically significant formation constants for the species SrOH(+) and SrCl(+) at all temperatures, and for Sr(OH)2(0) and SrCl2(0) at temperatures above 446 K. The first and second stepwise association constants for the ion pairs followed the order K(A1)(SrOH(+)) > K(A1)(SrCl(+)) > K(A2)[Sr(OH)2(0)] > K(A2)[SrCl2(0)], consistent with long-range solvent polarization effects associated with the lower static dielectric constant and high compressibility of water at elevated temperatures. The stepwise association constants to form SrCl(+) agree with previously reported values for CaCl(+) to within the combined experimental error at high temperatures and, at temperatures below ∼375 K, the values of log10 KA1 for strontium are lower than those for calcium by up to ∼0.3-0.4 units. The association constants for the species SrOH(+) and Sr(OH)2(0) are the first accurate values to be reported for hydroxide ion pairs with any divalent cation under these conditions.

  12. Formation of Semimetallic Cobalt Telluride Nanotube Film via Anion Exchange Tellurization Strategy in Aqueous Solution for Electrocatalytic Applications.

    Science.gov (United States)

    Patil, Supriya A; Kim, Eun-Kyung; Shrestha, Nabeen K; Chang, Jinho; Lee, Joong Kee; Han, Sung-Hwan

    2015-11-25

    Metal telluride nanostructures have demonstrated several potential applications particularly in harvesting and storing green energy. Metal tellurides are synthesized by tellurization process performed basically at high temperature in reducing gas atmosphere, which makes the process expensive and complicated. The development of a facile and economical process for desirable metal telluride nanostructures without complicated manipulation is still a challenge. In an effort to develop an alternative strategy of tellurization, herein we report a thin film formation of self-standing cobalt telluride nanotubes on various conducting and nonconducting substrates using a simple binder-free synthetic strategy based on anion exchange transformation from a thin film of cobalt hydroxycarbonate nanostructures in aqueous solution at room temperature. The nanostructured films before and after ion exchange transformation reaction are characterized using field emission scanning electron microscope, energy dispersive X-ray analyzer, X-ray photoelectron spectroscopy, thin film X-ray diffraction technique, high resolution transmission electron microscope, and selected area electron diffraction analysis technique. After the ion exchange transformation of nanostructures, the film shows conversion from insulator to highly electrical conductive semimetallic characteristic. When used as a counter electrode in I3(-)/I(-) redox electrolyte based dye-sensitized solar cells, the telluride film exhibits an electrocatalytic reduction activity for I3(-) with a demonstration of solar-light to electrical power conversion efficiency of 8.10%, which is highly competitive to the efficiency of 8.20% exhibited by a benchmarked Pt-film counter electrode. On the other hand, the telluride film electrode also demonstrates electrocatalytic activity for oxygen evolution reaction from oxidation of water.

  13. LC-MS analysis in the e-beam and gamma radiolysis of metoprolol tartrate in aqueous solution: Structure elucidation and formation mechanism of radiolytic products

    Energy Technology Data Exchange (ETDEWEB)

    Slegers, Catherine [Unite d' Analyse Chimique et Physico-chimique des Medicaments, Universite Catholique de Louvain, CHAM 72.30, Avenue E. Mounier, 72, B-1200, Brussels (Belgium)]. E-mail: catherine.slegers@skynet.be; Maquille, Aubert [Unite d' Analyse Chimique et Physico-chimique des Medicaments, Universite Catholique de Louvain, CHAM 72.30, Avenue E. Mounier, 72, B-1200, Brussels (Belgium); Deridder, Veronique [Unite d' Analyse Chimique et Physico-chimique des Medicaments, Universite Catholique de Louvain, CHAM 72.30, Avenue E. Mounier, 72, B-1200, Brussels (Belgium); Sonveaux, Etienne [Unite de Chimie Pharmaceutique et de Radiopharmacie, Universite Catholique de Louvain, Brussels (Belgium); Habib Jiwan, Jean-Louis [Laboratoire de Spectrometrie de Masse, Universite Catholique de Louvain, Louvain-La-Neuve (Belgium); Tilquin, Bernard [Unite d' Analyse Chimique et Physico-chimique des Medicaments, Universite Catholique de Louvain, CHAM 72.30, Avenue E. Mounier, 72, B-1200, Brussels (Belgium)

    2006-09-15

    E-beam and gamma products from the radiolysis of aqueous solutions of ({+-})-metoprolol tartrate, saturated in nitrogen, are analyzed by HPLC with on-line mass and UV detectors. The structures of 10 radiolytic products common to e-beam and gamma irradiations are elucidated by comparing their fragmentation pattern to that of ({+-})-metoprolol. Two of the radiolytic products are also metabolites. Different routes for the formation of the radiolytic products are proposed.

  14. Thermodynamics of the complex formation of copper(II) with L-phenylalanine in aqueous ethanol solutions

    Science.gov (United States)

    Burov, D. M.; Ledenkov, S. F.; Vandyshev, V. N.

    2013-05-01

    Constants of the acid dissociation and complexation of L-phenylalanine (HPhe) with copper(II) ions are determined by potentiometry in aqueous ethanol solutions containing 0 to 0.7 molar fraction of alcohol. Changes in the Gibbs energy for the transfer from water to a binary solvent of L-phenylalanine, Phe- anion, and [CuPhe]+ complex are calculated. It is found that the weakening of solvation of the ligand donor groups in solvents with high ethanol contents is accompanied by an increase in the stability of [CuPhe]+ complex.

  15. 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).

  16. Fac-mer equilibria of coordinated iminodiacetate (ida2-) in ternary CuII(ida)(H-1B)- complex formation (B = imidazole, benzimidazole) in aqueous solution

    Indian Academy of Sciences (India)

    Susmita Bandyopadhyay; G N Mukherjee

    2003-08-01

    pH potentiometric and spectrophotometric investigations on the complex formation equilibria of CuII with iminodiacetate (ida2-) and heterocyclic N-bases, viz. imidazole and benzimidazole (B), in aqueous solution in binary and ternary systems using different molar ratios of the reactants indicated the formation of complexes of the types, Cu(ida), Cu(ida)(OH)-, (ida)Cu(OH)Cu(ida)-, Cu(B)2+, Cu(H-1B)+, Cu(ida)(H-1B)-, (ida)Cu(B)Cu(ida) and (ida)Cu(H-1B)Cu(ida)-. Formation constants of the complexes at 25 ± 1° at a fixed ionic strength, = 0.1 mol dm-3 (NaNO3) in aqueous solution were evaluated and the complex formation equilibria were elucidated with the aid of speciation curves. Departure of the experimental values of the reproportionation constants (log Cu) of ternary Cu(ida)(H-1B)- complexes from the statistically expected values, despite their formation in appreciable amounts at equilibrium, were assigned to fac(f)-mer(m) equilibria of the ida2- ligand coordinated to CuII, as the N-heterocyclic donors, (H-1B)-, coordinate trans- to the N-(ida2-) atom in the binary Cu(ida) complex to form the ternary Cu(ida) (H-1B)- complexes.

  17. Formation of Amino Acids on the Sonolysis of Aqueous Solutions Containing Acetic Acid, Methane, or Carbon Dioxide, in the Presence of Nitrogen Gas.

    Science.gov (United States)

    Dharmarathne, Leena; Grieser, Franz

    2016-01-21

    The sonolysis of aqueous solutions containing acetic acid, methane, or carbon dioxide in the presence of nitrogen gas was found to produce a number of different amino acids at a rate of ∼1 to 100 nM/min, using ultrasound at an operating power of 70 W and 355 kHz. Gas-phase elementary reactions are suggested, and discussed, to account for the formation of the complex biomolecules from the low molar mass solutes used. On the basis of the results, a new hypothesis is presented to explain the formation of amino acids under primitive atmospheric conditions and how their formation may be linked to the eventual abiotic genesis of life on Earth.

  18. Dimer formation in radiation-irradiated aqueous solution of lysozyme studied by light-scattering-intensity measurement

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, S.; Masuda, T.; Kondo, M. (Institute of Physical and Chemical Research, Wako, Saitama (Japan); Tokyo Metropolitan Univ. (Japan). Faculty of Science); Seki, H.; Imamura, M. (Institute of Physical and Chemical Research, Wako, Saitama (Japan))

    1981-07-01

    The reaction of lysozyme with OH radical, Br/sub 2/ anion radical, and e/sup -/sub(aq), produced in an aqueous solution by pulsed electrons and ..gamma..-rays, were investigated. Irradiated enzymes showed an increase in the light scattering intensity (LSI) which is proportional to the absorbed dose. Results obtained from SDS gel electrophoresis confirm dimerization of lysozyme, which is considered to be responsible for the increase in LSI. It was found that the rate constant of the dimerization of protein radicals produced in the reaction with OH radical is 2k = (1.0+-0.3) x 10/sup 6/M/sup -1/s/sup -1/ and the yield of the dimerization is 0.6 in G. The enzymatic activity of the dimer is shown to be reduced to about 30 per cent of that of the intact enzyme. It is concluded that the radiation-induced inactivation of lysozyme is largely due to dimerization.

  19. Dimer formation in radiation-irradiated aqueous solution of lysozyme studied by light-scattering-intensity measurement.

    Science.gov (United States)

    Hashimoto, S; Seki, H; Masuda, T; Imamura, M; Kondo, M

    1981-07-01

    The reaction of lysozyme with OH., Br.-2 and e-aq, produced in an aqueous solution by pulsed electrons and gamma-rays, were investigated. Irradiated enzymes showed an increase in the light scattering intensity (LSI) which is proportional to the absorbed dose. Results obtained from SDS gel electrophoresis confirm dimerization of lysozyme, which is considered to be responsible for the increase in LSI. It was found that the rate constant of the dimerization of protein radicals produced in the reaction with OH. is 2K=(1.0 +/- 0.3) X 10(6)M-1 s-1 and the yield of the dimerization is 0.6 in G. The enzymatic activity of the dimer is shown to be reduced to about 30 per cent of that of the intact enzyme. It is concluded that the radiation-induced inactivation of lysozyme is largely due to dimerization.

  20. Multiscale approach to CO2 hydrate formation in aqueous solution: phase field theory and molecular dynamics. Nucleation and growth.

    Science.gov (United States)

    Tegze, György; Pusztai, Tamás; Tóth, Gyula; Gránásy, László; Svandal, Atle; Buanes, Trygve; Kuznetsova, Tatyana; Kvamme, Bjorn

    2006-06-21

    A phase field theory with model parameters evaluated from atomistic simulations/experiments is applied to predict the nucleation and growth rates of solid CO(2) hydrate in aqueous solutions under conditions typical to underwater natural gas hydrate reservoirs. It is shown that under practical conditions a homogeneous nucleation of the hydrate phase can be ruled out. The growth rate of CO(2) hydrate dendrites has been determined from phase field simulations as a function of composition while using a physical interface thickness (0.85+/-0.07 nm) evaluated from molecular dynamics simulations. The growth rate extrapolated to realistic supersaturations is about three orders of magnitude larger than the respective experimental observation. A possible origin of the discrepancy is discussed. It is suggested that a kinetic barrier reflecting the difficulties in building the complex crystal structure is the most probable source of the deviations.

  1. Network formation in graphene oxide composites with surface grafted PNIPAM chains in aqueous solution characterized by rheological experiments.

    Science.gov (United States)

    GhavamiNejad, Amin; Hashmi, Saud; Joh, Han-Ik; Lee, Sungho; Lee, Youn-Sik; Vatankhah-Varnoosfaderani, Mohammad; Stadler, Florian J

    2014-05-14

    Poly N-isopropyl acrylamide (PNI) radically polymerized in aqueous solution in the presence of graphene oxide (GO) can significantly change the properties of the resulting solution from a regular polymer solution to a soft solid with a GO content of only 0.176 wt% (3 wt% with respect to PNI). However, these properties require the presence of both grafting and supramolecular interactions between polymer chains and hydrophilic groups on GO (-OH, -COOH), proven by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction and spectroscopy (XRD) and Raman spectra. While very low GO-contents (below 0.05 wt%) only lead to a labile structure, which can be disassembled by shear, higher contents yield composites with solid-like characteristics. This is clearly evident from the rheological behaviour, which changes significantly at a GO content around 0.15 wt%. Intensive shearing destroys the weak network, which cannot reform quickly at lower GO-concentrations, while at intermediate concentrations, restructuring is fast. GO-contents of 0.176 wt% lead to a material behaviour, which almost perfectly recovers from small deformations (creep and creep recovery compliance almost match) but larger deformations lead to permanent damage to the sample.

  2. ENVIRONMENTALLY FRIENDLY COMPLEXONES. THE THERMODYNAMIC CHARACTERISTICS OF THE FORMATION OF AL3+ ION COMPLEXES WITH ETHYLENEDIAMINEDISUCCINIC ACID IN AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    L.N. Tolkacheva

    2012-06-01

    Full Text Available Complex formation between Al3+ and ethylenediamine - N,N`-disuccinic acid (H4L was studied at 25°C against the background of 0.1, 0.5, 1.0 N solutions of KNO3 by potentiometry and mathematical modeling. The extrapolation of concentration constants to zero ionic strength was used to calculate the thermodynamic constants of the formation of the AlL–, AlHL complexes using an equation with one individual parameter (logβ0 = 16.27 ± 0.07, 9.19 ± 0.2 respectively.

  3. On the formation and structure of rare-earth element complexes in aqueous solutions under hydrothermal conditions with new data on gadolinium aqua and chloro complexes

    Science.gov (United States)

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

    2007-01-01

    (III) chloro complexes increases steadily with temperature from 0.4 ?? 0.2 to 1.7 ?? 0.3 in the 0.006m chloride solution and from 0.9 ?? 0.7 to 1.8 ?? 0.7 in the 0.1m GdCl3 aqueous solution in the 300-500????C range. Conversely, the number of H2O ligands of Gd(H2O)??-nCln+3-n complexes decreases steadily from 8.9 ?? 0.4 to 5.8 ?? 0.7 in the 0.006m GdCl3 aqueous solution and from 9.0 ?? 0.5 to 5.3 ?? 1.0 in the 0.1m GdCl3 aqueous solution at temperatures from 25 to 500????C. Analysis of our results shows that the chloride ions partially displace the inner-shell water molecules during Gd(III) complex formation under hydrothermal conditions. The Gd-OH2 bond of the partially-hydrated Gd(III) chloro complexes exhibits slightly smaller rates of length contraction (??? 0.005??A??/100????C) for both solutions. The structural aspects of chloride speciation of Gd(III) as measured from this study and of Yb(III) as measured from our previous experiments are consistent with the solubility of these and other REE in deep-sea hydrothermal fluids. ?? 2006 Elsevier B.V. All rights reserved.

  4. Aqueous Biphasic Systems for the Synthesis of Formates by Catalytic CO2 Hydrogenation: Integrated Reaction and Catalyst Separation for CO2 -Scrubbing Solutions.

    Science.gov (United States)

    Scott, Martin; Blas Molinos, Beatriz; Westhues, Christian; Franciò, Giancarlo; Leitner, Walter

    2017-03-22

    Aqueous biphasic systems were investigated for the production of formate-amine adducts by metal-catalyzed CO2 hydrogenation, including typical scrubbing solutions as feedstocks. Different hydrophobic organic solvents and ionic liquids could be employed as the stationary phase for cis-[Ru(dppm)2 Cl2 ] (dppm=bis-diphenylphosphinomethane) as prototypical catalyst without any modification or tagging of the complex. The amines were found to partition between the two phases depending on their structure, whereas the formate-amine adducts were nearly quantitatively extracted into the aqueous phase, providing a favorable phase behavior for the envisaged integrated reaction/separation sequence. The solvent pair of methyl isobutyl carbinol (MIBC) and water led to the most practical and productive system and repeated use of the catalyst phase was demonstrated. The highest single batch activity with a TOFav of approximately 35 000 h(-1) and an initial TOF of approximately 180 000 h(-1) was achieved in the presence of NEt3 . Owing to higher stability, the highest productivities were obtained with methyl diethanolamine (Aminosol CST 115) and monoethanolamine (MEA), which are used in commercial scale CO2 -scrubbing processes. Saturated aqueous solutions (CO2 overpressure 5-10 bar) of MEA could be converted into the corresponding formate adducts with average turnover frequencies up to 14×10(3)  h(-1) with an overall yield of 70 % based on the amine, corresponding to a total turnover number of 150 000 over eleven recycling experiments. This opens the possibility for integrated approaches to carbon capture and utilization.

  5. Molar Absorptivity and Quantum Yield of Fe(II) Photo-formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Comlexes

    Science.gov (United States)

    Hitomi, Y.; Arakaki, T.

    2009-04-01

    Fe(III)/Fe(II) cycle in the environment affects formation of active oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be an important source of photo-chemically formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species in the aqueous solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. Dicarboxylate compounds studied were oxalate, malonate, succinate, malate, and phthalate.

  6. Ultrasound assisted reduction of graphene oxide to graphene in L-ascorbic acid aqueous solutions: kinetics and effects of various factors on the rate of graphene formation.

    Science.gov (United States)

    Abulizi, Abulikemu; Okitsu, Kenji; Zhu, Jun-Jie

    2014-05-01

    The reduction of graphene oxide (GO) to graphene (rGO) was achieved by using 20 kHz ultrasound in L-ascorbic acid (L-AA, reducing agent) aqueous solutions under various experimental conditions. The effects of ultrasound power, ultrasound pulse mode, reaction temperature, pH value and L-AA amount on the rates of rGO formation from GO reduction were investigated. The rates of rGO formation were found to be enhanced under the following conditions: high ultrasound power, long pulse mode, high temperature, high pH value and large amount of L-AA. It was also found that the rGO formation under ultrasound treatment was accelerated in comparison with a conventional mechanical mixing treatment. The pseudo rate and pseudo activation energy (Ea) of rGO formation were determined to discuss the reaction kinetics under both treatment. The Ea value of rGO formation under ultrasound treatment was clearly lower than that obtained under mechanical mixing treatment at the same condition. We proposed that physical effects such as shear forces, microjets and shock waves during acoustic cavitation enhanced the mass transfer and reaction of L-AA with GO to form rGO as well as the change in the surface morphology of GO. In addition, the rates of rGO formation were suggested to be affected by local high temperatures of cavitation bubbles.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. INDUCTION OF AGGREGATE FORMATION OF CATIONIC POLYSOAPS AND SURFACTANTS BY LOW CONCENTRATIONS OF ADDITIVES IN AQUEOUS-SOLUTION

    NARCIS (Netherlands)

    WANG, GJ; ENGBERTS, JBFN

    1994-01-01

    The induction of aggregate formation of cationic polysoaps ((CL)-Copol C1-12), cetyltrimethylammonium bromide (CTAB), n-dodecyltrimethylammonium bromide (DTAB), and n-dodecylmethyldiallylammonium bromide (DMDAAB) by low concentrations of Methyl Orange (10(-5)-10(-4) M) and anionic surfactants (conce

  13. Structures and formation mechanisms of aquo/hydroxo oligomeric beryllium in aqueous solution: a density functional theory study.

    Science.gov (United States)

    Jin, Xiaoyan; Liao, Rongbao; Wu, Hai; Huang, Zhengjie; Zhang, Hong

    2015-09-01

    The structures and formation mechanisms of a wide variety of aquo/hydroxo oligomeric beryllium clusters were investigated using density functional theory. The structural parameters of beryllium clusters were found to vary regularly with the stepwise substitution of bound water molecules in the inner coordination sphere by hydroxyl groups. According to the Gibbs free energies deduced from SMD solvation model computations, unhydrolyzed oligomeric beryllium species are the most favorable products of polymerization, independent of the degrees of hydrolysis of the reactants. Simulation of the formation processes of oligomeric beryllium showed that polymerization, in essence, involves the nucleophilic attack of a terminal hydroxyl group in one BeO4 tetrahedron on the beryllium center in another BeO4 tetrahedron, leading to the bridging of two BeO4 tetrahedrons by a hydroxyl group.

  14. Formation of fractals by the self-assembly of interpolymer adducts of polymethacrylic acid with complementary polymers in aqueous solution

    Indian Academy of Sciences (India)

    Kandhasamy Durai Murugan; Arlin Jose Amali; Paramasivam Natarajan

    2012-03-01

    Interpolymer adducts of poly(methacrylic acid), (PMAA), with poly(vinylpyrrolidone) in presence of sodium chloride or potassium chloride form highly ordered fractal patterns in films on glass surface on drying at ambient temperature. The structure, morphology and the conditions under which the formation of fractal patterns occurs were investigated by SEM, EDX and confocal microscopic techniques. Self-organization of PMAA with complementary polymers such as poly(vinylpyrrolidone) is well-known and in the presence of sodium chloride formation of the fractals in films of the adducts is a novel observation. Fractal formation occurs due to the aggregation of interpolymer adducts. The composition of the fractals in the film is studied by EDX and confocal microscopic images of the fluorophores covalently bound to PMAA. In presence of salts, sodium chloride or potassium chloride, micellar like entities of 80 nm size were formed which further aggregate to form fractal patterns. It is suggested that the fractals result from the interpolymer adduct by Diffusion Limited Aggregation mechanism.

  15. 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.

  16. Mineral catalysis of the formation of the phosphodiester bond in aqueous solution - The possible role of montmorillonite clays

    Science.gov (United States)

    Ferris, James P.; Ertem, Gozen; KAMALUDDIN; Agarwal, Vipin; Hua, Lu Lin

    1989-01-01

    The possible role of montmorillonite clays in the spontaneous formation on the primitive earth of the phosphodiester bond in the presence of water was investigated in experiments measuring the binding of various nucleosides and nucleotides with Na(+)-montmorillonite 22A and the reactions of these compounds with a water-soluble carbodiimide. It was found that, at neutral pH, adenine derivatives bind stronger than the corresponding uracil derivatives, consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. The reaction of the 5-prime-AMP with carbodiimide resulted in the formation of 2-prime,5-prime-pApA (18.9 percent), 3-prime,5-prime-pApA (11 percent), and AppA (4.8 percent). The yields of these oligomers obtained when poly(U) was used in place of the clay were 15.5 percent, 3.7 percent, and 14.9 percent AppA, respectively.

  17. 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

  18. Access to small size distributions of nanoparticles by microwave-assisted synthesis. Formation of Ag nanoparticles in aqueous carboxymethylcellulose solutions in batch and continuous-flow reactors.

    Science.gov (United States)

    Horikoshi, Satoshi; Abe, Hideki; Torigoe, Kanjiro; Abe, Masahiko; Serpone, Nick

    2010-08-01

    This article examines the effect(s) of the 2.45-GHz microwave (MW) radiation in the synthesis of silver nanoparticles in aqueous media by reduction of the diaminesilver(i) complex, [Ag(NH(3))(2)](+), with carboxymethylcellulose (CMC) in both batch-type and continuous-flow reactor systems with a particular emphasis on the characteristics of the microwaves in this process and the size distributions. This microwave thermally-assisted synthesis is compared to a conventional heating (CH) method, both requiring a reaction temperature of 100 degrees C to produce the nanoparticles, in both cases leading to the formation of silver colloids with different size distributions. Reduction of the diaminesilver(i) precursor complex, [Ag(NH(3))(2)](+), by CMC depended on the solution temperature. Cooling the reactor during the heating process driven with 390-Watt microwaves (MW-390W/Cool protocol) yielded silver nanoparticles with sizes spanning the range 1-2 nm. By contrast, the size distribution of Ag nanoparticles with 170-Watt microwaves (no cooling; MW-170W protocol) was in the range 1.4-3.6 nm (average size approximately 3 nm). The overall results suggest the potential for a scale-up process in the microwave-assisted synthesis of nanoparticles. Based on the present data, a flow-through microwave reactor system is herein proposed for the continuous production of silver nanoparticles. The novel flow reactor system (flow rate, 600 mL min(-1)) coupled to 1200-Watt microwave radiation generated silver nanoparticles with a size distribution 0.7-2.8 nm (average size ca. 1.5 nm).

  19. Access to small size distributions of nanoparticles by microwave-assisted synthesis. Formation of Ag nanoparticles in aqueous carboxymethylcellulose solutions in batch and continuous-flow reactors

    Science.gov (United States)

    Horikoshi, Satoshi; Abe, Hideki; Torigoe, Kanjiro; Abe, Masahiko; Serpone, Nick

    2010-08-01

    This article examines the effect(s) of the 2.45-GHz microwave (MW) radiation in the synthesis of silver nanoparticles in aqueous media by reduction of the diaminesilver(i) complex, [Ag(NH3)2]+, with carboxymethylcellulose (CMC) in both batch-type and continuous-flow reactor systems with a particular emphasis on the characteristics of the microwaves in this process and the size distributions. This microwave thermally-assisted synthesis is compared to a conventional heating (CH) method, both requiring a reaction temperature of 100 °C to produce the nanoparticles, in both cases leading to the formation of silver colloids with different size distributions. Reduction of the diaminesilver(i) precursor complex, [Ag(NH3)2]+, by CMC depended on the solution temperature. Cooling the reactor during the heating process driven with 390-Watt microwaves (MW-390W/Cool protocol) yielded silver nanoparticles with sizes spanning the range 1-2 nm. By contrast, the size distribution of Ag nanoparticles with 170-Watt microwaves (no cooling; MW-170W protocol) was in the range 1.4-3.6 nm (average size ~3 nm). The overall results suggest the potential for a scale-up process in the microwave-assisted synthesis of nanoparticles. Based on the present data, a flow-through microwave reactor system is herein proposed for the continuous production of silver nanoparticles. The novel flow reactor system (flow rate, 600 mL min-1) coupled to 1200-Watt microwave radiation generated silver nanoparticles with a size distribution 0.7-2.8 nm (average size ca. 1.5 nm).

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Molar Absorptivity and Concentration-Dependent Quantum Yield of Fe(II) Photo-Formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Complexes

    Science.gov (United States)

    Hitomi, Y.; Arakaki, T.

    2009-12-01

    Redox cycles of iron in the aquatic environment affect formation of reactive oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be important sources of photo-formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. We initiated a study to characterize Fe(II) photo-formation from Fe(III)-dicarboxylates with the concentration ranges that are relevant to the natural aquatic environment. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species. The molar absorptivity of Fe(III)-dicarboxylate species was obtained by UV-VIS spectrophotometer, and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained from photochemical experiments. These experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. We used initial concentrations of less than 10 micromolar Fe(III) to study the photochemical formation of Fe(II). Dicarboxylate compounds studied include oxalate, malonate, succinate, malate, and phthalate. We report molar absorptivity and concentration-dependent quantum yields of Fe(II) photo-formation of individual Fe(III)-dicarboxylates.

  7. 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.

  8. Radiation formation of colloidal silver particles in aqueous systems.

    Science.gov (United States)

    Cuba, Václav; Nemec, Mojmír; Gbur, Tomás; John, Jan; Pospísil, Milan; Múcka, Viliam

    2010-01-01

    This paper reports on the formation of silver nanoparticles initiated by gamma and UV radiation in various aqueous solutions. Inorganic precursors were used for radiation and/or photochemical reduction of Ag(+) ions to a metallic form. The influence of various parameters on the nucleation and formation of colloid particles was studied. Attention was also focused on the composition of the irradiated solution. Aliphatic alcohols were used as scavengers of OH radicals and other oxidizing species. The influence of the stabilizers on the formation and stability of the nanoparticles was studied.

  9. 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.

  10. 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.

  11. Crystalline fibrillar gel formation in aqueous surfactant-antioxidant system.

    Science.gov (United States)

    Joseph, Linet Rose; Tata, B V R; Sreejith, Lisa

    2015-08-01

    Cetyltrimethylammonium bromide (CTAB) is a well-known cationic surfactant capable to micellize into diverse morphologies in aqueous medium. We observed the formation of an opaque gel state from aqueous CTAB solution in the presence of the aromatic additive, para-coumaric acid (PCA). Optical microscopic images revealed the presence of large fibrils in the system at room temperature. Gel nature of the fibrils was confirmed by rheological measurements. Presence of interstitial water in the fibrils was recognized with Raman spectroscopy. On heating the sample above 30 (°) C, the fibrillar gel state changes to a transparent liquid state with Newtonian flow properties. Dynamic light scattering study hinted the presence of small micelles in the solution above 30 (°) C. Thus the system showed a temperature-dependent structural transition from opaque water-swollen gel to transparent micellar liquid. The formation of water-swollen fibrillar network is attributed to surfactant-additive intermolecular interactions in aqueous medium. Transition to micelle phase above 30 (°) C is related to Kraft transition which is observed at significantly lower temperature for CTAB in the absence of PCA. The structural features of PCA play a key role in promoting fibrillar network formation and elevating the Kraft transition in aqueous solution of CTAB.

  12. OPTICAL PROPERTIES OF CARBAMIDE AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    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

  13. Formation of a-Si:H and a-Si{sub 1-x}C{sub x} :H nanowires by Ag-assisted electroless etching in aqueous HF/AgNO{sub 3} solution

    Energy Technology Data Exchange (ETDEWEB)

    Douani, Rachida [Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Piret, Gaelle, E-mail: gaelle.offranc@polytechnique.edu [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Hadjersi, Toufik [Unite de Developpement de la Technologie du Silicium (UDTS), 2, Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Algiers (Algeria); Chazalviel, Jean-Noel; Solomon, Ionel [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France)

    2011-06-01

    The formation of hydrogenated amorphous silicon-carbon alloy (a-Si{sub 1-x}C{sub x}:H) nanowires is studied for different carbon concentrations (0-7%) by using Ag-assisted electroless etching of the thin a-Si{sub 1-x}C{sub x}:H films deposited by plasma-enhanced chemical vapour deposition from silane/methane gas mixtures. The nanowires morphologies (length, density, ...), studied by scanning electron microscopy, strongly depend on the concentration of the etchant (aqueous solution of hydrofluoric acid and silver nitrate), the etching time, and the carbon concentration of the deposited layer.

  14. Aqueous Solution Vessel Thermal Model Development II

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. 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.

  16. In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

    Science.gov (United States)

    Lu, W.J.; Chou, I.-Ming; Burruss, R.C.; Yang, M.Z.

    2006-01-01

    A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

  17. 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.

  18. Study of complex formation between C18H36N2O6 and UO22+ cation in some binary mixed non-aqueous solutions

    Directory of Open Access Journals (Sweden)

    G.H. Rounaghi

    2017-02-01

    Full Text Available The complexation reaction between UO22+ cation and the macrobicyclic ligand C18H36N2O6 was studied in acetonitrile–dimethylformamide (AN–DMF, acetonitrile–tetrahydrofuran (AN–THF, acetonitrile–dichloromethane (AN–DCM binary solvent solutions at different temperatures using the coductometric method. In most cases, C18H36N2O6 forms a 1:1 [M:L] complex with the UO22+ cation. But in some of the studied solvent systems, in addition to formation of a 1:1 complex, a 1:2 [M:L2] complex is formed in solution. A non-linear behavior was observed for changes of logKf of the (C18H36N2O6·UO22+ complex versus the composition of the binary mixed solvents. The sequence of the stability of the (C18H36N2O6·UO22+ complex in pure solvent systems at 25 °C decreases in the order: AN > THF > DMF. In the case of binary solvent solutions, the stability constant of the complex at 25 °C was found to be: AN–DCM > AN–THF > AN–DMF. The values of thermodynamic quantities (ΔSc°,ΔHc°, for the formation of the complex were obtained from temperature dependence of the stability constant of the complex using the van't Hoff plots. The results show that in all cases, the complex is both entropy and enthalpy stabilized and both of these parameters are affected by the nature and composition of the mixed solvent systems.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. "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.

  5. 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....

  6. 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

  7. 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...

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. The thermodynamic characteristics of complex formation of Cd2+ with N,N-Bis(carboxymethyl)aspartic acid in aqueous solutions at 298.15 K

    Science.gov (United States)

    Lytkin, A. I.; Chernyavskaya, N. V.; Litvinenko, V. E.

    2011-01-01

    The equilibrium constants and heats of formation of complexes of N,N-bis(carboxymethyl)aspartic acid (H4Y) with Cd2+ ions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO3) were determined by potentiometric titration and calorimetrically. The thermodynamic characteristics of formation of the CdY2- complex at fixed and zero ionic strength values were calculated. The values obtained were interpreted.

  15. 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.

  16. 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...

  17. 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.

  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. 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.

  20. Effect of aqueous solution and load on the formation of DLC transfer layer against Co-Cr-Mo for joint prosthesis.

    Science.gov (United States)

    Guo, Feifei; Zhou, Zhifeng; Hua, Meng; Dong, Guangneng

    2015-09-01

    Diamond-like carbon (DLC) coating exhibits excellent mechanical properties such as high hardness, low friction and wear, which offer a promising solution for the metal-on-metal hip joint implants. In the study, the hydrogen-free DLC coating with the element Cr as the interlay addition was deposited on the surface of the Co-Cr-Mo alloy by a unbalanced magnetron sputtering method. The coating thickness was controlled as 2 µm. Nano-indentation test indicated the hardness was about 13 GPa. DLC coated Co-Cr-Mo alloy disc against un-coated Co-Cr-Mo alloy pin (spherical end SR9.5) comprised the friction pairs in the pin-on-disc tribotest under bovine serum albumin solution (BSA) and physiological saline(PS).The tribological behavior under different BSA concetrations(2-20 mg/ml), and applied load (2-15N) was investigated.DLC transfer layer did not form under BSA solution, even though different BSA concetration and applied load changed. The coefficient of friction(COF) under 6 mg/ml BSA at 10 N was the lowest as 0.10. A higher COF of 0.13 was obtained under 20 mg/ml BSA. The boundary absorption layer of protein is the main factor for the counterparts. However, the continous DLC transfer layer was observed under PS solution, which make a lower COF of 0.08.

  1. Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

    NARCIS (Netherlands)

    Sabil, K.M.; Duarte, A.R.C.; Zevenbergen, J.F.; Ahmad, M.M.; Yusup, S.; Omar, A.A.; Peters, C.J.

    2010-01-01

    A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time decreas

  2. [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.

  3. 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.

  4. 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.

  5. Temperature and Concentration Effects of Aqueous Solution of Sodium Octanoate on Micelle Formation Measured by Small angle X-ray Scattering

    Directory of Open Access Journals (Sweden)

    A.P. Kuzmenko

    2014-07-01

    Full Text Available Characteristic sizes of sodium octanoate micelles have been determined (by nucleus radius with the use of small angle X-ray scattering technique at various molar concentrations, which are for a spherical shape 1 and nonspherical 1.2 nm, respectively. The value of the critical concentration for micelle formation (CMC2 has been also found equal to 0.7 M.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Use of electrical impedance spectroscopy as a practical method of investigating the formation of aggregates in aqueous solutions of dyes and surfactants.

    Science.gov (United States)

    de Oliveira, Helinando P; de Melo, Celso P

    2011-06-01

    Molecular aggregation plays a key role in the physicochemical properties of dyes and surfactants. In this work, we show that electrical impedance spectroscopy (EIS) provides a practical method for the investigation of processes such as micellization in surfactants and dye dimerization. The electrical characterization of the structural phase transitions associated with aggregation events in these systems allows an accurate and direct determination of relevant parameters such as the corresponding critical concentrations for micelle formation and dimerization of these types of molecules, without the need of recurring to the use of auxiliary probe or reporter molecules. Because of its competitive advantages with respect to currently used methods (such as conductimetry and spectroscopic techniques), we argue that when implemented along the procedures described in this work, EIS becomes a simple and convenient technique for the characterization of aggregation processes in soft matter.

  14. 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.

  15. UV-visible spectroscopic and electrochemical study of the complex formation between Fe(II) and 5-amino-1,10-phenantroline (5-Aphen) in aqueous solution.

    Science.gov (United States)

    Lozano-Camargo, María Luisa; Rojas-Hernández, Alberto; Gómez-Hernández, Martín; Pacheco-Hernández, Ma de Lourdes; Galicia, Laura; Ramírez-Silva, María Teresa

    2007-06-15

    The system Fe(II)-5-Aphen-H(2)O was studied. The spectroscopic and electrochemical results show that only one stable complex between Fe(II) and 5-Aphen forms, having a 1:3 stoichiometric ratio. The spectrophotometry study allowed determination of the formation constant of the complex (logbeta(3)=23.42+/-0.06). Also, the stability of the complex was evaluated as a function of pH; it was found that it decomposed at low pH values depending on the concentration and a pseudo-first order kinetics constant associated with k'=0.011min(-1). The results are in agreement with the electrochemical behaviour observed in the system, which indicated that at pH 1.33 the destruction of the complex [Fe(5-Aphen)3](2+) took place as a function of time; however, when the experiments were carried out at pH 6.19 the complex was stable. The thermodynamic data obtained through the use of MEDUSA allowed construction of predominance zone diagrams of the system Fe(II)-5-Aphen-H(2)O under the experimental conditions used. The thermodynamic results represented in the PZD describe the experimental behaviour reported in this work.

  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. 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.

  18. 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

  19. 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…

  20. 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.

  1. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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....

  16. 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...

  17. 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.

  18. [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.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. 水相中金属铜表面生成亚铜-邻菲罗啉配合物的反应%FORMATION OF BIS ( 1 , 10-PHENANTHROLINE) CUPROUS COMPLEXES ON METALLIC COPPER SURFACE IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    聂崇实; 顾亦君; 孙杰

    1996-01-01

    本文研究了零价铜在邻菲罗啉水溶液中的反应.当溶液敞露于空气并存在有机阴离子X-时,例如苯甲酸盐(Bz)、对甲基苯磺酸盐(Ts)等,铜的表面生成了致密的反应产物的薄层,经IR、UV/VIS、MS和元素分析证明了该薄层为相当纯的亚铜的邻菲罗啉配位化合物,结构为[Cu(phen)2]+X-.在乙醇/甲苯混合溶剂中得到了表面反应产物的晶体[Cu(phen)2](CH3C4H6SO3)C2HsOH,并用X-ray测得了结构.本工作表明溶液中的Cu1离子抑制Cu0氧化成Cu1而影响反应层的形成,同时又促进Cu1氧化成Cu1的过程.%The formation of cuprous complex on metallic copper surface in 1,10-phenanthroline (phen) aqueous solution has been investigated as exposed in air and in the presence of common organic anions (X-) such as benzoate (Bz-) and toluene sulphonate (Ts-). The complexes deposited on the surface of metallic copper have been proved to be rather pure cuprous phenanthroline complexes having the structure [Cu(phen)2]X based on the elemental analysis, IR, UV/C2H5OH was determined by X-ray diffraction analysis. The work demonstrated that the Cu1 ion in the reaction solution hindered the process of Cu0 to Cu1 and in the meanwhile accelerated the process of Cu 1 to Cu 1.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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...

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. A Study on the Aqueous Formation of Secondary Organic Aerosols

    Science.gov (United States)

    Sinclair, K.; Tsigaridis, K.

    2013-12-01

    The effect aerosols have on radiative forcing in the atmosphere is recognized as one of the largest uncertainties in the radiation budget. About 80% of organic aerosol mass in the atmosphere is estimated to be created though secondary processes. Recently, the aqueous formation of secondary organic aerosols (SOA) has become recognized as important when considering the source, transformation and radiative impacts of SOA. This work focuses on implementing a mechanism for aqueous SOA formation that can be used in atmospheric chemistry and models of all scales, from box to global. A box model containing a simplified chemical mechanism for the aqueous production of precursors of aqueous SOA (Myriokefalitakis et al. (2011) is coupled to gas-phase chemistry which uses the carbon bond mechanism (CBM) IV is presented. The model implements aqueous chemistry of soluble gases, both in-cloud and aerosol water, including organic compounds such as glyoxal and methylglyoxal, which have been shown as potentially significant sources for dissolved secondary organic aerosols. This mechanism implements aqueous phase mass transfer and molecular dissociation. The model's performance is evaluated against previous box model studies from the literature. A comparison is conducted between the detailed GAMMA model (McNeill et al., 2012), which is constrained with chamber experiments and the one developed here. The model output under different atmospheric conditions is explored and differences and sensitivities are assessed. The objective of this work is to create a robust framework for simulating aqueous phase formation of SOA and maximizing the computational efficiency of the model, while maintaining accuracy, in order to later use the exact mechanism in global climate simulations.

  11. 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.

  12. 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.

  13. 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....

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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...

  20. 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...

  1. 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.

  2. 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.

  3. 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).

  4. 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...

  5. 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...

  6. 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.

  7. 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 ...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Aqueous gel formation from sodium salts of cellobiose lipids.

    Science.gov (United States)

    Imura, Tomohiro; Yamamoto, Shuhei; Yamashita, Chikako; Taira, Toshiaki; Minamikawa, Hiroyuki; Morita, Tomotake; Kitamoto, Dai

    2014-01-01

    Cellobiose lipids (CLs) are asymmetric bolaform biosurfactants, which are produced by Cryptococcus humicola JCM 10251 and have fungicidal activity. In this study, the sodium salts of CLs (CLNa) were prepared to improve aqueous solubility of the CLs, and their surface and gelation properties in aqueous solutions were examined by surface tension, rheology, and freeze-fracture transmission electron microscopy (FF-TEM) measurements. The surface tension measurements revealed that the CLNa have high surface activity: CMC1 and γCMC1 are 0.1 mg/mL and 34.7 mN/m, respectively. It was also found that the CLNa form giant micelles above their CMC, whose average size is 116.6 ± 31.9 nm. Unlike conventional surfactants, the surface tension reduced further with an increase in concentration and the aqueous solution became viscous at the minimum gelation concentration (MGC: 5.0 mg/mL). In rheological studies, the obtained gels proved to be rather soft and their sol-gel temperature was found to be approximately 50℃. FF-TEM observation of the gels showed 3D supramolecular structures with an entangled fibrous network. Since the present CLNa aqueous gels have a degree of fungicidal activity, they could be useful for novel multifunctional soft materials applicable to the food and cosmetic industries.

  11. 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.

  12. 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.

  13. Dielectric analysis on phase transition and micelle shape of polyoxyethylene trisiloxane surfactant in dilute aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Ya Wen Zhou; Wei Zhou; Fu Han; Bao Cai Xu

    2011-01-01

    The cloudy Silwet L-77 aqueous solution on the concentration range from 0.5% to 50% was investigated by dielectric relaxation spectroscopy. The concentration dependence of phase microstructure was confirmed by means of analyzing the dielectric parameters of bulk solution. The relaxation behavior was assigned to the interfacial polarization between the micelle and the medium, and the relaxation distribution parameter was used to figure the shape transition from sphere to ellipsoid with the concentration increasing. The synchronous reduction of permittivity and conductivity indicated the formation of the lamellar phase. As compensation, the quantity of the surfactant liquid phase gradually decreased, whose shape constantly kept ellipsoidal.

  14. 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

  15. 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-].

  16. Aqueous solutions of uranium(VI) as studied by time-resolved emission spectroscopy: a round-robin test.

    Science.gov (United States)

    Billard, Isabelle; Ansoborlo, Eric; Apperson, Kathleen; Arpigny, Sylvie; Azenha, M Emilia; Birch, David; Bros, Pascal; Burrows, Hugh D; Choppin, Gregory; Couston, Laurent; Dubois, Veronique; Fanghänel, Thomas; Geipel, Gerhard; Hubert, Solange; Kim, Jae I; Kimura, Takaumi; Klenze, Reinhardt; Kronenberg, Andreas; Kumke, Michael; Lagarde, Gerard; Lamarque, Gerard; Lis, Stefan; Madic, Charles; Meinrath, Gunther; Moulin, Christophe; Nagaishi, Ryuji; Parker, David; Plancque, Gabriel; Scherbaum, Franz; Simoni, Eric; Sinkov, Sergei; Viallesoubranne, Carole

    2003-08-01

    Results of an inter-laboratory round-robin study of the application of time-resolved emission spectroscopy (TRES) to the speciation of uranium(VI) in aqueous media are presented. The round-robin study involved 13 independent laboratories, using various instrumentation and data analysis methods. Samples were prepared based on appropriate speciation diagrams and, in general, were found to be chemically stable for at least six months. Four different types of aqueous uranyl solutions were studied: (1) acidic medium where UO2(2+)aq is the single emitting species, (2) uranyl in the presence of fluoride ions, (3) uranyl in the presence of sulfate ions, and (4) uranyl in aqueous solutions at different pH, promoting the formation of hydrolyzed species. Results between the laboratories are compared in terms of the number of decay components, luminescence lifetimes, and spectral band positions. The successes and limitations of TRES in uranyl analysis and speciation in aqueous solutions are discussed.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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 %.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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....

  6. 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.

  7. 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.

  8. 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.

  9. Aqueous SOA formation from radical oligomerization of methyl vinyl ketone (MVK) and methacrolein (MACR)

    Science.gov (United States)

    Renard, P.; Siekmann, F.; Ravier, S.; Temime-Roussel, B.; Clément, J.; Ervens, B.; Monod, A.

    2013-12-01

    It is now accepted that one of the important pathways of secondary organic aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the chemical mechanisms leading to macromolecules are still not well understood. It was recently shown that oligomer production by OH radical oxidation in the aerosol aqueous phase from α-dicarbonyl precursors, such as methylglyoxal and glyoxal, is irreversible and fast. We have investigated the aqueous phase photooxidation of MACR and MVK, which are biogenic organic compounds derived from isoprene. Aqueous phase photooxidation of MVK and MACR was investigated in a photoreactor using photolysis of H2O2 as OH radical source. Electrospray high resolution mass spectrometry analysis of the solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1800 Da within less than 15 minutes of reaction. Highest oligomer formation rates were obtained under conditions of low dissolved oxygen, highest temperature (T = 298 K) and highest precursor initial concentrations ([MVK]0 = 20 mM). A radical mechanism of oligomerization is proposed to explain the formation of the high molecular weight products. Furthermore, we quantified the total amount of carbon present in oligomers. Kinetic parameters of the proposed oligomerization mechanism are constrained by means of a box model that is able to reproduce the temporal evolution of intermediates and products as observed in the laboratory experiments. Additional model simulations for atmospherically-relevant conditions will be presented that show the extent to which these radical processes contribute to SOA formation in the atmospheric multiphase system as compared to other aqueous phase as well as traditional SOA sources. MVK time profile (as measured by UV Spectroscopy) and mass spectra (obtained using UPLC-ESI-MS for the retention time range 0-5 min in the positive mode) at 5, 10 and 50 min of reaction (MVK 20 mM, 25° C, under

  10. 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.

  11. 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.

  12. Monte Carlo simulation of indirect damage to biomolecules irradiated in aqueous solution: The radiolysis of glycylglycine

    Energy Technology Data Exchange (ETDEWEB)

    Bolch, W.E.; Turner, J.E.; Yoshida, H.; Jacobson, K.B.; Hamm, R.N.; Wright, H.A.; Ritchie, R.H.; Klots, C.E.

    1988-07-01

    A Monte Carlo computer code is developed for simulating the radiolysis of glycylglycine in both oxygenated and deoxygenated aqueous solution. Second, this model is used to calculate the yields of various products in solutions irradiated either by 250-kVp X-rays or by /sup 60/Co gamma rays. Third, calculated product yields are compared to measured yields where available. The Monte Carlo computer codes used in this study are modified and extended versions of three existing simulation codes, written at the Oak Ridge National Laboratory (ORNL), which simulate irradiations of pure liquid water. The ORNL codes calculate the formation, diffusion, and reaction of free radicals and other species along charged-particle tracks in liquid water. As part of this research, these codes are extended to simulate irradiation of pure oxygenated water, oxygenated glycylglycine solutions, and deoxygenated glycylglycine solutions. 80 refs., 38 figs., 8 tabs.

  13. 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.

  14. Thermodynamics of micelle formation in a water-alcohol solution of sodium tetradecyl sulfate

    Science.gov (United States)

    Shilova, S. V.; Tret'yakova, A. Ya.; Barabanov, V. P.

    2016-01-01

    The effects of addition of ethanol and propan-1-ol on sodium tetradecyl sulfate micelle formation in an aqueous solution are studied via microprobe fluorescence microscopy and conductometry. The critical micelle concentration, quantitative characteristics of micelles, and thermodynamic parameters of micelle formation are determined. Addition of 5-15 vol % of ethanol or 5-10 vol % of propan-1-ol is shown to result in a lower critical micelle concentration than in the aqueous solution, and in the formation of mixed spherical micelles whose sizes and aggregation numbers are less than those for the systems without alcohol. The contribution from the enthalpy factor to the free energy of sodium tetradecyl sulfate micelle formation is found to dominate in mixed solvents, in contrast to aqueous solutions.

  15. Solubility of vanadium from manganese vanadates in aqueous solutions of soda ash

    Science.gov (United States)

    Khalezov, B. D.; Krasheninin, A. G.; Vatolin, N. A.; Ovchinnikova, L. A.

    2016-05-01

    It is shown that, in the course of developing the technology of pure vanadium pentoxide preparation from manganic vanadium-containing metallurgical slags, their oxidative roasting and cinder formation without alkaline additives are accompanied by the decomposition of spinelides with the formation of manganese meta- and pyrovanadates. Concentrated aqueous solutions of soda ash with an Na2CO3 concentration of 120-150 g/dm3 are accepted as a selective leaching reagent for vanadium from a cinder. Manganese metaand pyrovanadates are synthesized, and the procedure of their preparation is presented. The solubility of vanadium from manganese vanadates in aqueous solutions of soda ash at C_{Na_2 CO_3 } = 150 g/dm^3 is studied at 20-95°C for pyrovanadate and at 85-95°C for metavanadate. It is shown that vanadium should be leached from converter manganic slags roasted without alkaline metal additives at a leaching solution temperature higher than 95°C. There is a possibility to increase the vanadium content in a leaching solution to 60-80 g/dm3. The results obtained are used in the development of the technology of vanadium leaching.

  16. 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.

  17. Lead Removal from Aqueous Solutions Using Novel Gel Adsorbent Synthesized from Natural Condensed Tannin

    Institute of Scientific and Technical Information of China (English)

    占新民; 赵璇; AKANEMiyazaki; YOSHIONakano

    2003-01-01

    Lead has caused serious environmental pollution due to its toxicity, accumulation in food chains and persistence in nature. In this paper, removal of lead from aqueous solutions is investigated using a novel gel adsorbent synthesized from natural condensed tannin. The novel adsorbent performs in aqueous solutions as a weak base with valid basic groups of 1.2mmol·g-1 tannin gel particles and therefore results in the elevation of pH value of aqueous solutions. Even when initial pH is 3.6, final pH at equilibrium can climb up to 6.5 that is above the pH value for Pb(OH)2 precipitation formation and then lead can be removed from wastewater by this so-called surface precipitation. The adsorption isotherm can be expressed by the Langmuir equation and the maximum capacity for adsorption of Pb is up to 92mg·g-l(based on dry adsorbent) when initial pH value is 3.6. Hence, the adsorbent does offer favorable properties in lead removal with respect to its high adsorption capacity at low initial pH value,which is advantageous to lead removal from acidic wastewater. A model is put forward to describe the individual adsorption phenomenon of the tannin gel adsorbent.

  18. Extraction of cobalt(II) from aqueous solution by N,N'-carbonyl difatty amides

    Institute of Scientific and Technical Information of China (English)

    Emad A. Jaffar Al-Mulla; Khalid Waleed S. Al-Janabi

    2011-01-01

    The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal. In this study, solvent extraction of Co(Ⅱ) from aqueous solution using a mixture of N,N'-carbonyl difatty amides (CDFAs) synthesised from palm oil as the extractant was carried out. The effects of various parameters such as acid, contact time, extractant concentration, metal ion concentration and stripping agent and the separation of Co(Ⅱ) from other metal ions such as Fe(Ⅱ), Ni(Ⅱ), Zn(Ⅲ) and Cd(Ⅱ) were investigated. It was found that the extraction of Co(Ⅱ) into the organic phase involved the formation of 1:1 complexes. Co(Ⅱ) was successfully separated from commonly associated metal ions such as Fe(Ⅱ), Ni(Ⅱ), Zn(Ⅲ) and Cd(Ⅱ). Co(Ⅱ) stripping from the loaded organic phase was studied in aqueous solution. These results are useful to recover Co(Ⅱ) from aqueous solution utilising (CDFAs) as an extractant.

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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].

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Raman spectra and ab initio calculation of a structure of aqueous solutions of methanol

    Science.gov (United States)

    Hushvaktov, H. A.; Tukhvatullin, F. H.; Jumabaev, A.; Tashkenbaev, U. N.; Absanov, A. A.; Hudoyberdiev, B. G.; Kuyliev, B.

    2017-03-01

    Small amount of low molecular weight alcohols leads to appearance of some special properties of alcohol-water solutions. In the literature it is associated with structural changes in solution with changing concentration. However, the problem special properties and structure of solutions at low concentration of alcohol is not very clear. Accordingly, we carried out quantum-chemical calculations and experimental studies of aqueous solutions of methyl alcohol. The calculations performed for ten molecular alcohol-water mixtures showed that with a low concentration of methyl alcohol in water the solubility of alcohol is poor: the alcohol molecules are displaced from the water structure and should form a particular structure. Thus, with low concentration of alcohol in the aqueous solution there are two types of structures: the structure of water and the structure of alcohol that should lead to the presence of specific properties. At high concentration of alcohol the structure of water is destroyed and there is just the structure made of alcohol-water aggregates. This interpretation is consistent with the experimental data of Raman spectroscopy. The band of Csbnd O vibrations of alcohol is detected to be of complex character just in the region of the presence of specific properties. Formation of intermolecular H-bonds also complicates the Raman spectra of Osbnd H or O-D vibrations of pure alcohol: a non-coincidence of peak frequencies, a shift of the band towards low-frequency region, a strong broadening of the band.

  20. 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.

  1. Investigation into the temporal stability of aqueous standard solutions of psilocin and psilocybin using high performance liquid chromatography.

    Science.gov (United States)

    Anastos, N; Barnett, N W; Pfeffer, F M; Lewis, S W

    2006-01-01

    This paper reports an investigation into the temporal stability of aqueous solutions of psilocin and psilocybin reference drug standards over a period of fourteen days. This study was performed using high performance liquid chromatography utilising a (95:5% v/v) methanol: 10 mM ammonium formate, pH 3.5 mobile phase and absorption detection at 269 nm. It was found that the exclusion of light significantly prolonged the useful life of standards, with aqueous solutions of both psilocin and psilocybin being stable over a period of seven days.

  2. 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.

  3. 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.

  4. 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.

  5. Formation of aligned silicon-nanowire on silicon in aqueous HF/(AgNO{sub 3} + Na{sub 2}S{sub 2}O{sub 8}) solution

    Energy Technology Data Exchange (ETDEWEB)

    Douani, R. [Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Hadjersi, T. [Unite de Developpement de la Technologie du Silicium (UDTS), 2, Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Alger (Algeria)], E-mail: hadjersi@yahoo.com; Boukherroub, R. [Institut de Recherche Interdisciplinaire (IRI, FRE 2963) and Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, CNRS-8520), Cite Scientifique, Avenue Poincare - B.P. 60069, 59652 Villeneuve d' Ascq (France); Adour, L. [Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Manseri, A. [Unite de Developpement de la Technologie du Silicium (UDTS), 2, Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Alger (Algeria)

    2008-09-15

    Highly oriented silicon nanowire (SiNW) layer was fabricated by etching Si substrate in HF/(AgNO{sub 3} + Na{sub 2}S{sub 2}O{sub 8}) solution at 50 deg. C. The morphology and the photoluminescence (PL) of the etched layer as a function of Na{sub 2}S{sub 2}O{sub 8} concentration were studied. The SiNW layers formed on silicon were investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). It was demonstrated that the morphology of the etched layers depends on the Na{sub 2}S{sub 2}O{sub 8} concentration. Room-temperature photoluminescence (PL) from etched layer was observed. It was found that the utilisation of Na{sub 2}S{sub 2}O{sub 8} decreases PL peak intensity. Finally, a discussion on the formation process of the silicon nanowires is presented.

  6. The shear dependence of the methylcellulose gelation phenomena in aqueous solution and in ceramic paste.

    Science.gov (United States)

    Knarr, Matthias; Bayer, Roland

    2014-10-13

    The gelation temperature of methylcellulose (MC) in aqueous solutions as well as in aqueous ceramic paste depends on the applied shear. Rheological investigations in oscillation vs. shear mode show lower gelation temperature at low shear rates as for the corresponding angular frequencies. Above a critical shear rate the gelation temperature is shifted to higher temperatures. The paste extrusion process uses MC as a plasticizer and runs under high shear conditions. When extruding close to the gelation temperature of the MC in the paste, crack formation and other defects can occur. The upwards shift of the gelation temperature with increasing applied shear gives a larger temperature window during the extrusion process. The understanding of the shear influence on the gelation temperature is important to design the optimal process conditions.

  7. Fe(III) solar light induced degradation of diethyl phthalate (DEP) in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Mailhot, G.; Caceres, J.; Malato, S.; Bolte, M.

    2003-07-01

    The degradation of diethyl phthalate (DEP) photoinduced by Fe(III) in aqueous solution has been investigated under solar irradiation in the CPC reactor at Plataforma Solar de Almeria. Hydroxyl radicals OH, responsible of the degradation, are formed via an intramolecular photo redox process in excited Fe(III) aqua complexes. For prolonged irradiations DEP and its photoproducts are completely mineralized due to the regeneration of the absorbing species and the continuous formation of OH radicals that confers a catalytic aspect to the process. Consequently, the degradation photoinduced by Fe(III) could be an efficient method of DEP removal from water. (Author) 28 refs.

  8. {sup 1}H NMR investigation of self-association of vanillin in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bogdan, Mircea; Floare, Calin G; PIrnau, Adrian, E-mail: mircea.bogdan@itim-cj.r [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

    2009-08-01

    A self-association of vanillin have been studied by {sup 1}H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  9. 1H NMR investigation of self-association of vanillin in aqueous solution

    Science.gov (United States)

    Bogdan, Mircea; Floare, Calin G.; Pîrnau, Adrian

    2009-08-01

    A self-association of vanillin have been studied by 1H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  10. Silver-catalyzed decarboxylative alkynylation of aliphatic carboxylic acids in aqueous solution.

    Science.gov (United States)

    Liu, Xuesong; Wang, Zhentao; Cheng, Xiaomin; Li, Chaozhong

    2012-09-05

    C(sp(3))-C(sp) bond formations are of immense interest in chemistry and material sciences. We report herein a convenient, radical-mediated and catalytic method for C(sp(3))-C(sp) cross-coupling. Thus, with AgNO(3) as the catalyst and K(2)S(2)O(8) as the oxidant, various aliphatic carboxylic acids underwent decarboxylative alkynylation with commercially available ethynylbenziodoxolones in aqueous solution under mild conditions. This site-specific alkynylation is not only general and efficient but also functional group compatible. In addition, it exhibits remarkable chemo- and stereoselectivity.

  11. Comparison of XAD macroporous resins for the concentration of fulvic acid from aqueous solution

    Science.gov (United States)

    Aiken, G.R.

    1979-01-01

    Five macroreticular, nonlonlc AmberlHe XAD resins were evaluated for concentration and Isolation of fulvlc acid from aqueous solution. The capacity of each resin for fulvlc acid was measured by both batch and column techniques. Elution efficiencies were determined by desorptlon with 0.1 N NaOH. Highest recoveries were obtained with the acrylic ester resins which proved to be most efficient for both adsorption and elution of fulvlc acid. Compared to the acrylic ester resins, usefulness of the styrene dvlnybenzene resins to remove fulvlc acid is limited because of slow diffusion-controlled adsorption and formation of charge-transfer complexes, which hinders elution. ?? 1979 American Chemical Society.

  12. Degradation of Hydrogenated Nitrile-butadiene Rubber in Aqueous Solutions of H2S or HCl

    Institute of Scientific and Technical Information of China (English)

    CONG Chuan-bo; CUI Can-can; MENG Xiao-yu; LU Shao-jie; ZHOU Qiong

    2013-01-01

    The degradation of hydrogenated nitrile-butadiene rubber(HNBR) soaped in aqueous solutions of H2S and HCl was investigated.The samples unexposed and exposed to different solutions were characterized by 13C nuclear magnetic resonance(13C NMR),X-ray photoelectron and infrared spectroscopies.In contrast to those of unexposed samples and samples soaped in HCl solution,the mechanical properties of samples exposed to H2S solution significantly deteriorated,in which the new groups of C(=O)-NH2,C-S-C and C=S emerged.The mechanism of C=S and C-S-C formation was speculated,except for that of the formation of group C(=O)-NH2,which was widely discussed in acidic condition such as HC1 solution.The formation of C-S-C was due to radical reaction initiated by mercapto radical and that of C=S was due to nucleophilic reaction initiated by mercapto cations.This finding is helpful to understanding the seal failure of HNBR in working environment containing H2S.

  13. Intermolecular complexation and phase separation in aqueous solutions of oppositely charged biopolymers.

    Science.gov (United States)

    Singh, S Santinath; Siddhanta, A K; Meena, Ramavatar; Prasad, Kamalesh; Bandyopadhyay, S; Bohidar, H B

    2007-07-01

    Turbidity measurements performed at 450nm were used to follow the process of complex formation, and phase separation in gelatin-agar aqueous solutions. Acid (Type-A) and alkali (Type-B) processed gelatin (polyampholyte) and agar (anionic polyelectrolyte) solutions, both having concentration of 0.1% (w/v) were mixed in various proportions, and the mixture was titrated (with 0.01 M HCl or NaOH) to initiate associative complexation that led to coacervation. The titration profiles clearly established observable transitions in terms of the solution pH corresponding to the first occurrence of turbidity (pH(C), formation of soluble complexes), and a point of turbidity maximum (pH(phi), formation of insoluble complexes). Decreasing the pH beyond pH(phi) drove the system towards precipitation. The values of pH(C) and pH(phi) characterized the initiation of the formation of intermolecular charge neutralized soluble aggregates, and the subsequent formation of microscopic coacervate droplets. These aggregates were characterized by dynamic light scattering. It was found that Type-A and -B gelatin samples formed soluble intermolecular complexes (and coacervates) with agar molecules through electrostatic and patch-binding interactions, respectively.

  14. Obtaining nano-sized silver particles in aqueous solution under the influence of the contact nonequilibrium low-temperature plasma

    OpenAIRE

    Сергеева, Ольга Вячеславовна; Пивоваров, Александр Андреевич

    2015-01-01

    The influence of plasma-treating aqueous solution containing silver ions for formation of the nanoparticles of silver, their size and their variation over a predetermined time interval. As a processing tool to use contact nonequilibrium low-temperature plasma is formed between the electrode (anode), located in the gas phase and the liquid surface and recessed electrode in there. The electrolytic solution AgNO3 in the distilled water used as cathode. Studied the characteristics of the obtained...

  15. 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.

  16. Nitrogen-Doped Carbonaceous Materials for Removal of Phenol from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Magdalena Hofman

    2012-01-01

    Full Text Available Carbonaceous material (brown coal modified by pyrolysis, activation, and enrichment in nitrogen, with two different factor reagents, have been used as adsorbent of phenol from liquid phase. Changes in the phenol content in the test solutions were monitored after subsequent intervals of adsorption with selected adsorbents prepared from organic materials. Significant effect of nitrogen present in the adsorbent material on its adsorption capacity was noted. Sorption capacity of these selected materials was found to depend on the time of use, their surface area, and pore distribution. A conformation to the most well-known adsorption isotherm models, Langmuir, and Freundlich ones, confirms the formation of mono- and heterolayer solute (phenol coverage on the surface of the adsorbent applied herein. The materials proposed as adsorbents of the aqueous solution contaminants were proved effective, which means that the waste materials considered are promising activated carbon precursors for liquid phase adsorbents for the environmental protection.

  17. Removal of perfluoroalkyl sulfonates (PFAS) from aqueous solution using permanently confined micelle arrays (PCMAs)

    KAUST Repository

    Wang, Fei

    2014-12-01

    One new sorbent with permanently confined micelle arrays (PCMAs) has been synthesized to remove PFAS compounds from aquatic solutions. The TEM and SEM studies showed that large particle sizes with lots of macro-pores and highly order hexagonal structure of cylindrical micelle had been formed in the sorbent. The FTIR spectrums demonstrated the formation of Si-O-Si covalent bond in the new material. The kinetic study showed that the sorption of PFOS, PFHxS, and PFBuS by PCMAs reached equilibrium within 5 min. The pH and salts in solution are found to have limited effects on sorption of PFOS on the new sorbent, and regeneration experiments revealed that PFAS removal efficiencies by the PCMAs did not decrease after 5 cycle regenerations. The high capabilities of PCMAs make it a potentially attractive sorbent for the removal of PFCs from aqueous solution.

  18. Removal of trivalent samarium from aqueous solutions by activated biochar derived from cactus fibres

    Institute of Scientific and Technical Information of China (English)

    Loukia Hadjittofi; Styliana Charalambous; Ioannis Pashalidis

    2016-01-01

    The efficiency of activated biochar fibres obtained fromOpuntia Ficus Indica regarding the sorption of trivalent samarium (Sm(III)) from aqueous solutions was investigated by batch experiments. The effect of various physicochemical parameters (e.g. pH, initial metal concentration, ionic strength, temperature and contact time) on the Sm(III) adsorption was studied and the surface species were characterized by FTIR spectroscopy prior to and after the lanthanide sorption. The experimental results showed that the acti-vated biochar fibres possessed extraordinary sorption capacity for Sm(III) in acidic solutions (qmax=90 g/kg, pH 3.0) and near neutral solutions (qmax=350 g/kg, pH 6.5). This was attributed to the formation of samarium complexes with the surface carboxylic moieties, available in high density on the lamellar structures of the bio-sorbent.

  19. Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite

    Science.gov (United States)

    Navarro-Gonzalez, R.; Negron-Mendoza, A.; Ramos, S.; Ponnamperuma, C.

    1990-01-01

    The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Initiation of sugars synthesis from formaldehyde in the aqueous solution with ultraviolet radiation

    Science.gov (United States)

    Pestunova, O.; Simonov, A.; Stojanovskii, V.; Snytnikov, V.; Parmon, V.

    Many scientists consider autocatalytic sugars synthesis from formaldehyde in alkaline aqueous solutions via so-called formose reaction as a probable way of sugars formation at the prebiotic stage of the Earth evolution [1, 2]. However, the authors of paper [3] shown, that in the pure aqueous solution of formaldehyde, which does not contain even seeds of monosaccharides, the formose reaction of formaldehyde polymerisation does not occur. In this work we demonstrate that in the above mentioned solution the formose reaction can be initiated by ultraviolet radiation. A quartz cuvette (l = 10 mm) with an aqueous solution of formaldehyde (2 or 0.5 mol/l) and a magnetic stirrer was exposed to an ArF excimer laser radiation (wavelength 193 nm, 15 ns, 150 mJ, beam area 24 mm2). The location of the absorption maximum of carbonyl group of formaldehyde is 190 nm. In the course of the light-initiated reaction, in the UV spectra of solutions two absorption bands at 205 and 270 nm appear. Apparently, these bands are belonging to formic acid and glycolaldehyde, respectively. The increase of the optical density of the solution during such transformation decrease the transparency of the solution for the laser beam, this resulted in a gradual reducing of the reaction rate and the further stop of reaction. The conversion of formaldehyde at the photoreaction stopping was 7 % for the 2 mol/l solution and 16 % for the 0.5 mol/l one. The analysis of exposed solutions with a HPLC method has shown, that one of the products of the reaction is glycol aldehyde (C2O2H4), which formally is a primary C2-sugar. The yield of glycol aldehyde was 0.5 and 0.4 mol % respectively. It is well-known, that glycol aldehyde initiates the autocatalytic formose reaction, being a better initiator than other monosaccharides [4]. In our case, the addition of the UV-exposed solution to a formaldehyde and calcium hydroxide containing solution stimulated the formose reaction with a sharp reduction of the induction

  10. Rheology and electrospinning of regenerated bombyx mori silk fibroin aqueous solutions.

    Science.gov (United States)

    Hodgkinson, Tom; Chen, Ying; Bayat, Ardeshir; Yuan, Xue-Feng

    2014-04-14

    Bombyx mori silk fibroin (BMSF) has received considerable research interest as a potential biomaterial owing to its excellent mechanical properties and benign, versatile material fabrication options, including electrospinning. Despite this, characterizations of regenerated BMSF aqueous solutions and electrospun materials resulting from them are still very limited in the literature. This report details the rheological characterization of regenerated aqueous BMSF solutions under shear and elongational deformation. Well-characterized regenerated BMSF solutions were then systematically electrospun over a range of concentrations and process parameters to determine their effects on electrospinning processing windows and fiber morphology. BMSF solutions could not be electrospun successfully if BMSF concentration was below 20 wt % or the relaxation time measured using the CaBER rheometer was below 0.001 s. Electrospun BMSF fiber diameter was found to increase with solution concentration when stable electrospinning was achieved. An upper threshold of 30 wt % BMSF solution was identified for the formation of fibers with a circular cross section. Adding small amount of high molecular weight poly(ethylene oxide) was an effective rheological modifier that greatly improved the electrospinnability of BMSF solutions. Electrospinning BMSF-PEO solutions over a range of parameters significantly altered the fiber products. Increasing voltage from 0.5 to 1 kV/cm was found to decrease fiber diameter by approximately 50% (p < 0.001). Flow rate was found to have a significant effect on fiber diameter, which decreased with spinneret height. The results presented here provide valuable guidance in the production of BMSF electrospun materials with specific properties for tissue engineering and regenerative medicine.

  11. The Effect of Liquid Crystalline Structures on Antiseizure Properties of Aqueous Solutions of Ethoxylated Alcohols

    Directory of Open Access Journals (Sweden)

    Anna Bak

    2010-01-01

    Full Text Available 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 expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester and characterized by scuffing load (Pt, seizure load (Poz and limiting pressure of seizure (poz. Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the Pt values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value.

  12. The effect of liquid crystalline structures on antiseizure properties of aqueous solutions of ethoxylated alcohols.

    Science.gov (United States)

    Sulek, Marian Wlodzimierz; Bak, Anna

    2010-01-12

    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 expected, the viscosity of LLCs decreases considerably with an increase in shearing rate which is characteristic of liquid crystals being non-Newtonian liquids. Antiseizure properties were determined by means of a four-ball machine (T-02 Tester) and characterized by scuffing load (P(t)), seizure load (P(oz)) and limiting pressure of seizure (p(oz)). Alcohol ethoxylates forming mesophases in aqueous solutions have the strongest effect on the P(t) values which are several times higher than those measured in the presence of water. Ethoxylates with higher degrees of ethoxylation exhibit higher values of scuffing load. Those changes have been interpreted as a result of higher cloud points at which those compounds lose their amphiphilic properties. In general, the presence of mesophases in the bulk phase and particularly in the surface phase may lead to the formation of a lubricant film which separates the frictionally cooperating elements of a friction pair. The antiseizure efficiency of alcohol solutions is highest up to the load value which does not exceed the scuffing load value.

  13. Modeling the methane hydrate formation in an aqueous film submitted to steady cooling

    Energy Technology Data Exchange (ETDEWEB)

    Avendano-Gomez, J.R. [ESIQIE, Laboratorio de Ingenieria Quimica Ambiental, Mexico (Mexico). Inst. Politecnico Nacional; Garcia-Sanchez, F. [Laboratorio de Termodinamica, Mexico (Mexico). Inst. Mexicano del Petroleo; Gurrola, D.V. [UPIBI, Laboratorio de Diseno de Plantas, Mexico (Mexico). Inst. Politecnico Nacional

    2008-07-01

    Gas hydrates, or clathrate hydrates, are ice-like compounds that results from the kinetic process of crystallization of an aqueous solution supersaturated with a dissolved gas. This paper presented a model that took into account two factors involved in the hydrate crystallization, notably the stochastic nature of crystallization that causes sub-cooling and the heat resulting from the exothermic enthalpy of hydrate formation. The purpose of this study was to model the thermal evolution inside a hydrate forming system which was submitted to an imposed steady cooling. The study system was a cylindrical thin film of aqueous solution at 19 Mpa. The study involved using methane as the hydrate forming molecule. It was assumed that methane was homogeneously dissolved in the aqueous phase. Ethane hydrate was formed through a kinetic process of nucleation and crystallization. In order to predict the onset time of nucleation, the induction time needed to be considered. This paper discussed the probability of nucleation as well as the estimation of the rate of nucleation. It also presented the mathematical model and boundary conditions. These included assumptions and derivation of the model; boundary conditions; initial conditions; and numerical solution of the model equation. It was concluded that the heat source must be considered when investigating crystallization effects. 34 refs., 2 tabs., 2 figs.

  14. Effects of dimethyl sulfoxide on the hydrogen bonding structure and dynamics of aqueous N-methylacetamide solution

    Indian Academy of Sciences (India)

    APRAMITA CHAND; SNEHASIS CHOWDHURI

    2016-06-01

    Effects of dimethyl-sulfoxide (DMSO) on the hydrogen bonding structure and dynamics in aqueousN-methylacetamide (NMA) solution are investigated by classical molecular dynamics simulations. Themodifications of structure and interaction between water and NMA in presence of DMSO molecules are calculatedby various site-site radial distribution functions and average interaction energies between these speciesin the solution. It is observed that the aqueous peptide hydrogen bond interaction is relatively stronger withincreasing concentration of DMSO, whereas methyl-methyl interaction between NMA and DMSO decreasessignificantly. The DMSO molecule prefers to interact with amide-hydrogen of NMA even at lower DMSO concentration.The lifetimes and structural-relaxation times of NMA-water, water-water and DMSO-water hydrogenbonds are found to increase with increasing DMSO concentration in the solution. The slower translationaland rotational dynamics of NMA is observed in concentrated DMSO solution due to formation of strongerinter-species hydrogen bonds in the solution.

  15. Photochemical oxidation of chloride ion by ozone in acid aqueous solution.

    Science.gov (United States)

    Levanov, Alexander V; Isaykina, Oksana Ya; Amirova, Nazrin K; Antipenko, Ewald E; Lunin, Valerii V

    2015-11-01

    The experimental investigation of chloride ion oxidation under the action of ozone and ultraviolet radiation with wavelength 254 nm in the bulk of acid aqueous solution at pH 0-2 has been performed. Processes of chloride oxidation in these conditions are the same as the chemical reactions in the system O3 - OH - Cl(-)(aq). Despite its importance in the environment and for ozone-based water treatment, this reaction system has not been previously investigated in the bulk solution. The end products are chlorate ion ClO3(-) and molecular chlorine Cl2. The ions of trivalent iron have been shown to be catalysts of Cl(-) oxidation. The dependencies of the products formation rates on the concentrations of O3 and H(+) have been studied. The chemical mechanism of Cl(-) oxidation and Cl2 emission and ClO3(-) formation has been proposed. According to the mechanism, the dominant primary process of chloride oxidation represents the complex interaction with hydroxyl radical OH with the formation of Cl2(-) anion-radical intermediate. OH radical is generated on ozone photolysis in aqueous solution. The key subsequent processes are the reactions Cl2(-) + O3 → ClO + O2 + Cl(-) and ClO + H2O2 → HOCl + HO2. Until the present time, they have not been taken into consideration on mechanistic description and modelling of Cl(-) oxidation. The final products are formed via the reactions 2ClO → Cl2O2, Cl2O2 + H2O → 2H(+) + Cl(-) + ClO3(-) and HOCl + H(+) + Cl(-) ⇄ H2O + Cl2. Some portion of chloride is oxidized directly by O3 molecule with the formation of molecular chlorine in the end.

  16. Reactivity of polyfunctional alcohols towards atmospheric radicals in the aqueous solution

    Science.gov (United States)

    Hoffmann, D.; Herrmann, H.

    2009-04-01

    Alcohols such as ethylene glycol, propylene glycol and glycerol are widely used compounds in numerous applications. The oxidation of these compounds can influence the tropospheric oxidation budget as well as contribute significantly to the formation of low volatile organic particle constituents, such as mono- and dicarboxylic acids. Model simulations applying the multiphase chemistry mechanism CAPRAM 3.0i (Chemical Aqueous Phase Radical Mechanism) show that the aqueous phase oxidation of ethylene glycol contribute significantly to the formation of the known particle constituent oxalic acid under remote (up to 1.7%) and urban (up to 9.5%) conditions. Due to their high solubility oxidation processes of polyalcohols will take place mainly in the aqueous solution. Oxidation reactions of alcohols are triggered by reactions with atmospheric radicals such as OH, NO3 and SO4-. However, for the detailed implementation of the tropospheric degradation of alcohols in atmospheric chemistry mechanisms many kinetic data, in particular as a function of the temperature, are still needed. Therefore, the reactivity of 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2,3-propanetriol (glycerol), 1,2-butanediol, 1,4-butanediol and 1,5-pentanediol was systematically investigated towards OH, NO3 and SO4- radicals in the aqueous solution. All kinetic measurements were done as a function of the temperature. During these experiments the temperature of the measurement solution was varied between 278 ≤ T [K] ≤ 318. Experiments were carried out using laser flash photolysis technique at a wavelength of 248 nm. Rate constants were measured directly or using competition kinetics in case of OH. The kinetic data and activation parameters obtained will be summarized and discussed with available literature data. Furthermore, the data obtained will be discussed in terms of reactivity correlations and atmospheric relevance. A more detailed implementation of

  17. 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

  18. 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

  19. 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...

  20. 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

  1. 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.

  2. 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.

  3. Fibril Formation and Phase Separation in Aqueous Cellulose Ethers

    Science.gov (United States)

    Maxwell, Amanda; Schmidt, Peter; McAllister, John; Lott, Joseph; Bates, Frank; Lodge, Timothy

    Aqueous solutions of many cellulose ethers are known to undergo thermoreversible gelation and phase separation upon heating to form turbid hydrogels, but the mechanism and resulting structures have not been well understood. Turbidity, light scattering and small-angle neutron scattering (SANS) are used to show that hydroxypropyl methylcellulose (HPMC) chains are dissolved in water below 50 °C and undergo phase separation at higher temperatures. At 70 °C, at sufficiently high concentrations in water, HPMC orders into fibrillar structures with a well-defined radius of 18 +/- 2 nm, as characterized by cryogenic transmission electron microscopy and SANS. The HPMC fibril structure is independent of concentration and heating rate. However, HPMC fibrils do not form a percolating network as readily as is seen in methylcellulose, resulting in a lower hot-gel modulus, as demonstrated by rheology.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.)

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Enhancement of hybridoma formation, clonability and cell proliferation in a nanoparticle-doped aqueous environment

    Directory of Open Access Journals (Sweden)

    Karnieli Ohad

    2008-01-01

    Full Text Available Abstract Background The isolation and production of human monoclonal antibodies is becoming an increasingly important pursuit as biopharmaceutical companies migrate their drug pipelines away from small organic molecules. As such, optimization of monoclonal antibody technologies is important, as this is becoming the new rate-limiting step for discovery and development of new pharmaceuticals. The major limitations of this system are the efficiency of isolating hybridoma clones, the process of stabilizing these clones and optimization of hybridoma cell secretion, especially for large-scale production. Many previous studies have demonstrated how perturbations in the aqueous environment can impact upon cell biology. In particular, radio frequency (RF irradiation of solutions can have dramatic effects on behavior of solutions, cells and in particular membrane proteins, although this effect decays following removal of the RF. Recently, it was shown that nanoparticle doping of RF irradiated water (NPD water produced a stabilized aqueous medium that maintained the characteristic properties of RF irradiated water for extended periods of time. Therefore, the ordering effect in water of the RF irradiation can now be studied in systems that required prolonged periods for analysis, such as eukaryotic cell culture. Since the formation of hybridoma cells involves the formation of a new membrane, a process that is affected by the surrounding aqueous environment, we tested these nanoparticle doped aqueous media formulations on hybridoma cell production. Results In this study, we tested the entire process of isolation and production of human monoclonal antibodies in NPD water as a means for further enhancing human monoclonal antibody isolation and production. Our results indicate an overall enhancement of hybridoma yield, viability, clonability and secretion. Furthermore, we have demonstrated that immortal cells proliferate faster whereas primary human fibroblasts

  2. Radiation chemical studies on thermosensitive N-isopropylacrylamide and its polymer in aqueous solutions.

    Science.gov (United States)

    Acharya, Anjali; Mohan, Hari; Sabharwal, S

    2003-12-01

    The pulse radiolysis technique has been employed to determine the initiation and propagation rates of different transient species involved in the polymerization of N-isopropylacrylamide (NIPA) in aqueous solutions. Polymerization by anionic mechanism has been observed to be faster than by the free-radical mechanism. The kinetic, spectroscopic and redox properties of the transient species formed upon reaction of primary radiolytic species of water radiolysis with NIPA have been evaluated. The one-electron oxidation potential for the formation of a radical cation is quite high (>2 V), but the one-electron reduction potential is low (in the range of -0.3 to -0.7 V). The radical anion of NIPA is able to undergo an electron-transfer reaction with MV(2+), and has a pK(a) value of 3.2. The tert-butyl alcohol radical was also able to initiate polymerization. Gamma radiation-induced polymerization studies showed that the reaction of H(.)/(.)OH/e(aq)(-)/tert-butyl alcohol radicals with NIPA results in a nearly equal yield of the gel fraction. The hydrogel is observed to have very little swelling below pH 3 and above pH 10. The linear polymer of NIPA formed by irradiating dilute aqueous solution is found to be a thermosensitive polymer with lower a critical solution temperature (LCST) of ~33 degrees C. The diameters of polymer molecules were 290 and 20 nm at temperature below and above LCST, respectively.

  3. INTERACTION OF POLY(SODIUM SULFODECYL METHACRYLATE) WITH CETYLTRIMETHYL AMMONIUM BROMIDE IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Cong-hua Lu; Chuan-qiou Luo; Wei-xiao Cao

    2003-01-01

    The interaction of poly(sodium sulfodecyl methacrylate) (PSSM) with cetyltrimethyl ammonium bromide (CTAB)was studied. It was found that the precipitate formed from PSSM and CTAB will be dissolved by excessive CTAB, resultingin the appearance of two maxima of the solution viscosity at the molar ratio (CTAB/-SO3-) of ≈ 0.68 and ≈ 1.30,respectively. The first one is related closely to the aggregation of polymer chains via CTAB molecules and the second oneshould be ascribed to the formation of the mixed micelles comprising surfactant and the polymer's hydrophobic chains. Theeffect of NaCl on the viscosity, the transmittance of the aqueous solution and the solubility of oil-soluble dye (dimethylyellow) in the mixed system were also investigated.

  4. Inclusion complexation of novocaine by beta-cyclodextrin in aqueous solutions.

    Science.gov (United States)

    Iglesias, Emilia

    2006-06-01

    The formation of inclusion complexes between beta-cyclodextrin (beta-CD) and the local anesthetic 2-(diethylamino)ethyl-p-amino-benzoate (novocaine) in aqueous solutions under different acidity conditions, using steady-state fluorescence or UV-vis spectroscopies, electrical conductivity, or the kinetic study of both the nitrosation reaction of the primary amine group in a mild acid medium and the hydrolysis of the ester function under an alkaline medium, has been studied. The inclusion complex formation between neutral or protonated novocaine and beta-CD of 1:1 stoichiometry was observed; however, the magnitude of the binding constants depends on the nature of both the guest and the host, and the higher-affinity guest-host was found under conditions when both the novocaine and the beta-CD were neutral molecules.

  5. 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.

  6. Facile synthesis of “green” gold nanocrystals using cynarin in an aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Katircioğlu, Zeynep; Şakalak, Hüseyin [Department of Metallurgical and Materials Engineering, Selcuk University, Konya 42075 (Turkey); Nanobiotechnology Laboratory, Advanced Technology Research and Application Center, Selcuk University, Konya 42075 (Turkey); Ulaşan, Mehmet [Nanobiotechnology Laboratory, Advanced Technology Research and Application Center, Selcuk University, Konya 42075 (Turkey); Department of Chemistry, Selcuk University, Konya 42075 (Turkey); Gören, Ahmet Ceyhan, E-mail: ahmetceyhan.goren@tubitak.gov.tr [TÜBİTAK UME, Chemistry Group, Organic Chemistry Laboratories, 41470 Gebze, Kocaeli (Turkey); Yavuz, Mustafa Selman, E-mail: selmanyavuz@selcuk.edu.tr [Department of Metallurgical and Materials Engineering, Selcuk University, Konya 42075 (Turkey); Nanobiotechnology Laboratory, Advanced Technology Research and Application Center, Selcuk University, Konya 42075 (Turkey)

    2014-11-01

    Highlights: • The first time a remarkably simple, versatile, environmentally friendly, one-pot and biogenic fabrication and aqueous synthesis of monodisperse gold nanoparticles by using cynarin. • Cynarin as a reductant and capping agent. • Exclusion of extra reducing agents or reductant. • Fabrication of Pd and Ag nanoparticles using cynarin in aqueous media. - Abstract: Herein we describe a water-based protocol that generates Au nanoparticles (AuNPs) by mixing aqueous solutions of HAuCl4 and cynarin (a natural product extract from artichoke leaf). Based on the observations from {sup 1}H NMR spectrum of AuNPs, a polyol oxidation mechanism by metal ions which eventually results in AuNPs formation, is proposed. Basically, the aromatic alcohol groups (1,2-benzenediol) of cynarin are oxidized to α-hydroxy ketone intermediate product, and then further oxidized to the vicinal diketone final product while the Au{sup 3+} ions are reduced to its atomic form (Au{sup 0}) which leads the generation of Au nanoparticles. This new protocol has also been employed to prepare multiply twinned Pd nanoparticles and Ag cubical aggregates. Due to exclusion of organic solvent, surfactant, or stabilizer for all these synthesis, this protocol may provide a simple, versatile, and environmentally benign route to fabricate noble-metal nanoparticles having various compositions and morphologies.

  7. Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

    Indian Academy of Sciences (India)

    Ashavani Kumar; Hrushikesh M Joshi; Anandrao B Mandale; Rajendra Srivastava; Suguna D Adyanthaya; Renu Pasricha; Murali Sastry

    2004-08-01

    In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and nonpolar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR).

  8. 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.

  9. 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.

  10. 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

  11. Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

    Science.gov (United States)

    Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

    2013-08-01

    The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

  12. Extensional flow behavior of aqueous guar gum derivative solutions by capillary breakup elongational rheometry (CaBER).

    Science.gov (United States)

    Szopinski, Daniel; Handge, Ulrich A; Kulicke, Werner-Michael; Abetz, Volker; Luinstra, Gerrit A

    2016-01-20

    The extensional rheological properties of aqueous ionic carboxymethyl hydroxypropyl guar gum (CMHPG) and non-ionic hydroxypropyl guar gum (HPG) solutions between the semi-dilute solution state and the concentrated network solution state were investigated by capillary breakup elongational rheometry (CaBER). Carboxymethylated guar gum derivatives show an instable filament formation in deionized water. The ratio of elongational relaxation time λE over the shear relaxation time λS follows a power law of λE/λS∼(c · [η])(-2). The difference of the relaxation times in shear and elongation can be related to the loss of entanglements and superstructures in elongational flows at higher strains.

  13. 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.

  14. 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

  15. 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.

  16. Transformation of modified brushite to hydroxyapatite in aqueous solution: effects of potassium substitution.

    Science.gov (United States)

    Kumar, M; Xie, J; Chittur, K; Riley, C

    1999-08-01

    Brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4 x 2H2O) was deposited electrolytically from calcium dihydrogen phosphate solution with and without potassium chloride (KCl) as a supporting electrolyte. The kinetics of brushite transformation to hydroxyapatite (HA, Ca5(PO4)3OH) in the presence of calcium and protein free, aqueous body fluid (Hank's balanced salt solution, HBSS) was investigated. We present evidence that the deposition of brushite in a KCl-supported electrochemical bath yields a modified brushite where some of the calcium is substituted by potassium. Transformation of both normal (i.e. potassium free) and modified brushite to hydroxyapatite upon exposure to calcium and protein-free aqueous fluid (HBSS) was followed by reflectance Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. Changes in the morphology of the coatings were studied using scanning electron microscopy (SEM). Results indicate that modified brushite undergoes faster transformation to hydroxyapatite in HBSS in comparison to normal brushite. Our results show that the presence of potassium ions in the brushite not only favors the formation of different intermediate phases but also alters transformation rates to HA.

  17. [Catalytic ozonation by ceramic honeycomb for the degradation of oxalic acid in aqueous solution].

    Science.gov (United States)

    Zhao, Lei; Sun, Zhi-Zhong; Ma, Jun

    2007-11-01

    Comparative experiments for the degradation of oxalic acid in aqueous solution were carried out in the three processes of ozonation alone, ceramic honeycomb-catalyzed ozonation and ceramic honeycomb adsorption. The results show that the degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation, ozonation alone and ceramic honeycomb adsorption systems are 37.6%, 2.2% and 0.4%, and the presence of ceramic honeycomb catalyst significantly improves the degradation rate of oxalic acid compared to the results from non-catalytic ozonation and adsorption. With the addition of tert-butanol, the degradation rates of oxalic acid in catalytic ozonation system decrease by 24.1%, 29.0% and 30.1%, respectively, at the concentration of 5, 10 and 15 mg x L(-1). This phenomenon indicates that ceramic honeycomb-catalyzed ozonation for the degradation of oxalic acid in aqueous solution follows the mechanism of *OH oxidation, namely the heterogeneous surface of catalyst enhances the initiation of *OH. The results of TOC analysis demonstrate that the process of ceramic honeycomb-catalyzed ozonation can achieve the complete mineralization level without the formation of intermediary degradation products. The experimental results suggest that the reaction temperature has positive relationship with the degradation rate of oxalic acid. The degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation system are 16.4%, 37.6%, 61.3% and 68.2%, at the respective reaction temperature of 10, 20, 30 and 40 degrees C.

  18. How does beta-cyclodextrin affect oxygen solubility in aqueous solutions of sodium perfluoroheptanoate?

    Science.gov (United States)

    Dias, A M A; Andrade-Dias, C; Lima, S; Coutinho, J A P; Teixeira-Dias, J J C; Marrucho, I M

    2006-11-15

    The solubility of oxygen in aqueous solutions of sodium perfluoroheptanoate (NaPFHept) at different concentrations was measured at 310.15 K with an apparatus based on the saturation method. The effect of adding beta-cyclodextrin (betaCD) on the solubility of oxygen was also studied. Conductimetry measurements showed that the presence of betaCD in aqueous solutions of NaPFHept increases its critical micellar concentration (CMC). In the presence of betaCD (15 mM), the characteristic minimum of oxygen solubility observed at the CMC is shifted from 83 to 114 mM, and the curvature at the minimum is reduced to 64% of the value in the absence of betaCD. Chemical shift changes for the H5 protons of betaCD, recorded as functions of the initial concentration of NaPFHept, point to the formation of a relatively strong 1:1 inclusion in betaCD of the perfluoroheptanoate anion. Hence, it is suggest that the effect of adding betaCD on the solubility of oxygen cannot be accounted for only by the perfluoroheptanoate anion inclusion in betaCD, but has to be ascribed to the direct influence of this inclusion complex on disrupting the aggregation process reducing the increase of oxygen solubility after the CMC value.

  19. 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.

  20. The effect of different complexing agents on the properties of zinc sulfide thin films deposited from aqueous solutions

    OpenAIRE

    2016-01-01

    The zinc sulfide (ZnS) thin films were prepared on glass substrates by chemical bath deposition using the aqueous solutions of zinc chloride, thiourea, pH regulator and complexing agent (ammonia and hydrazine hydrate, trisodium citrate or sodium hydroxide). The calculations of boundary conditions for formation of zinc sulfide and zinc hydroxide were made at various zinc salt concentrations with different complexing agents. The structural, morphology and optical properties of the ZnS thin film...

  1. Low-temperature liquid-liquid extraction of phenols from aqueous solutions with hydrophilic mixtures of extractants

    Science.gov (United States)

    Rudakov, O. B.; Khorokhordina, E. A.; Preobrazhenskii, M. A.; Rudakova, L. V.

    2016-08-01

    The volume ratios in acetonitrile-ethyl acetate (90 : 10, 95 : 5), acetonitrile-isopropanol-ethyl acetate (70 : 15 : 15, 80 : 5 : 15), and isopropanol-1-butanol (50 : 50) mixtures were determined. Their mixing with water (1 : 1) and storage at-10°C led to partitioning into two immiscible liquid phases without formation of the ice phase. The mixtures were shown to be useful as hydrophilic extractants in low-temperature liquidliquid extraction of phenol from aqueous solutions.

  2. 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.

  3. 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.

  4. 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....

  5. The effect of temperature on radiolysis of iodide ion diluted aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gorbovitskaya, T.; Tiliks, J. [Latvia Univ., Lab. of Radiation Chemistry, Riga (Latvia)

    1996-12-01

    To investigate the radiolysis of iodine containing aqueous solutions a flow type facility (ITF) has a possibility to irradiate aqueous solutions in the steel vessel with {sup 60}Co {gamma}-rays and continuously (on line) to analyze the products of radiolysis both in liquid and in gaseous phases. By means of ITF the formation of I{sub ox} (I{sub 2} + I{sub 3}{sup -} + HOI), IO{sub 3}{sup -}, H{sub 2}O{sub 2} was studied in 10{sup -5} - 10{sup -3} mol/dm{sup 3} CsI aqueous solutions by their radiolysis at dose rate 4.5 kGv/h for six hours in region of temperatures from 313 to 404 K. Some experiments in glass ampoules were also performed. The steady-state concentrations of I{sub ox} and IO{sub 3}{sup -} decreased with increasing temperature as linear function of inverted temperature. The effect decreased with decreasing concentration of iodide ion. As the result, at high temperatures (T{>=}380 K) the steady-state concentration of I{sub ox} does not depend essentially on the iodide ion initial concentration. Molecular iodine (I{sub 2}) released from the solution was the main radiolysis product in gaseous phase. Its steady-state concentration increased with increasing temperature because of iodine solubility in the water and decreased at the same time because the radiolytic iodine concentrations decreased. Therefore the most volatility of irradiated 10{sup -3} and 10{sup -4}M CsI solutions was observed at the temperature about 350 K. The volatility of 10{sup -5}M solutions gradually decreased with increasing temperature. The experimental data were explained on the base of the hypothesis that the reaction between I{sub 2} and radiolytic H{sub 2}O{sub 2} was the limit one determining the temperature dependence of I{sub ox} and IO{sub 3}{sup -}steady-state concentrations. Its activation energy was estimated to be 27,5 kcal.mol{sup -1}. The temperature dependence for reaction (IO{sup -} + H{sub 2}O{sub 2}) was also estimated. (author) 8 figs., 1 tab., 17 refs.

  6. Cu(II) complex formation with xylitol in alkaline solutions.

    Science.gov (United States)

    Norkus, Eugenijus; Vaiciūniene, Jūrate; Vuorinen, Tapani; Gaidamauskas, Ernestas; Reklaitis, Jonas; Jääskeläinen, Anna-Stiina; Crans, Debbie C

    2004-02-25

    The formation of four Cu(II)-xylitol complexes was observed in aqueous alkaline solutions (11.0 or =10), whereas dinuclear complex Cu2Xyl (log beta=29.2 +/- 0.3) is the predominant species at low ligand-to-metal ratio (L:M=0.5). Diffusion coefficients and molar absorptivities of the complex species were determined. pH variable 13C NMR suggested that pKa values of xylitol are rather similar and equal to 13.8 +/- 0.2, 13.9 +/- 0.1 and 13.9 +/- 0.2 for OH-groups adjacent to (C-1,C-5), (C-3) and (C-2,C-4) carbon atoms, respectively.

  7. Temperature and pH driven association in uranyl aqueous solutions

    CERN Document Server

    Druchok, M; 10.5488/CMP.15.43602

    2013-01-01

    An association behavior of uranyl ions in aqueous solutions is explored. For this purpose a set of all-atom molecular dynamics simulations is performed. During the simulation, the fractions of uranyl ions involved in dimer and trimer formations were monitored. To accompany the fraction statistics one also collected distributions characterizing average times of the dimer and trimer associates. Two factors effecting the uranyl association were considered: temperature and pH. As one can expect, an increase of the temperature decreases an uranyl capability of forming the associates, thus lowering bound fractions/times and vice versa. The effect of pH was modeled by adding H^+ or OH^- ions to a "neutral" solution. The addition of hydroxide ions OH^- favors the formation of the associates, thus increasing bound times and fractions. The extra H^+ ions in a solution produce an opposite effect, thus lowering the uranyl association capability. We also made a structural analysis for all the observed associates to reveal...

  8. Temperature and pH driven association in uranyl aqueous solutions

    Directory of Open Access Journals (Sweden)

    M. Druchok

    2012-12-01

    Full Text Available An association behavior of uranyl ions in aqueous solutions is explored. For this purpose a set of all-atom molecular dynamics simulations is performed. During the simulation, the fractions of uranyl ions involved in dimer and trimer formations were monitored. To accompany the fraction statistics one also collected distributions characterizing average times of the dimer and trimer associates. Two factors effecting the uranyl association were considered: temperature and pH. As one can expect, an increase of the temperature decreases an uranyl capability of forming the associates, thus lowering bound fractions/times and vice versa. The effect of pH was modeled by adding H+ or OH- ions to a "neutral" solution. The addition of hydroxide ions OH- favors the formation of the associates, thus increasing bound times and fractions. The extra H+ ions in a solution produce an opposite effect, thus lowering the uranyl association capability. We also made a structural analysis for all the observed associates to reveal the mutual orientation of the uranyl ions.

  9. Sonochemical redox reactions of Pu(III) and Pu(IV) in aqueous nitric solutions.

    Science.gov (United States)

    Virot, Matthieu; Venault, Laurent; Moisy, Philippe; Nikitenko, Sergey I

    2015-02-14

    The behavior of Pu(iv) and Pu(iii) was investigated in aqueous nitric solutions under ultrasound irradiation (Ar, 20 kHz). In the absence of anti-nitrous reagents, ultrasound has no effect on Pu(iv), while Pu(iii) can be rapidly oxidized to Pu(iv) due to the autocatalytic formation of HNO(2) induced by HNO(3) sonolysis. In the presence of anti-nitrous reagents (sulfamic acid or hydrazinium nitrate), Pu(iv) can be sonochemically reduced to Pu(iii). The reduction follows a first order reaction law and leads to a steady state where Pu(iv) and Pu(iii) coexist in solution. The reduction process is attributed to the sonochemical generation of H(2)O(2) in solution. The kinetics attributed to the reduction of Pu(iv) are however higher than those related to the formation of H(2)O(2) which, after several hypotheses, is explained by the sonochemical erosion of the titanium-based sonotrode. Titanium particles thereby generated can be solubilized under ultrasound and generate Ti(iii) as an intermediate species, a strong reducing agent able to react with Pu(iv).

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

    Science.gov (United States)

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

    2010-12-01

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

  11. Phosphate removal from aqueous solutions by nanoscale zero-valent iron.

    Science.gov (United States)

    Wu, Donglei; Shen, Yanhong; Ding, Aqiang; Qiu, Mengyu; Yang, Qi; Zheng, Shuangshuang

    2013-01-01

    In this study, nanoscale zero-valent iron (NZVI) was synthesized by conventional liquid-phase chemical reduction methods without a support material and then characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of NZVI particles on phosphate removal from aqueous solutions was examined. The results showed that the phosphate removal efficiency increased from 34.49% to 87.01% as the dosage of nanoscale iron particles increased from 100 to 600 mg L(-1) with an initial phosphate concentration of 10 mg L(-1), and the phosphate removal efficiency decreased from 72.89% to 51.39% as the initial phosphate concentration increased from 10 to 90 mg L(-1), with 400 mg L(-1) NZVI. Phosphate removal efficiencies of 99.41% and 95.09% were achieved at pH values of 2 and 4, respectively, with an initial phosphate concentration of 20 mg L(-1) and 400mg L(-1) NZVI. The use of NZVI particles synthesized in a carboxymethyl cellulose (CMC)-water solution significantly enhanced phosphate removal from an aqueous solution compared with the use of NZVI synthesized in an ethanol-water solution. NZVI particles achieved 71.34% phosphate removal, which was remarkably higher than that of microscale zero-valent iron (MZVI) particles (16.35%) with 10 mg L(-1) of phosphate and 400mg L(-1) iron. Based on the removal mechanism analysis performed in this study, we recommend that phosphate removal be accomplished by simultaneous adsorption and chemical precipitation. The XRD patterns of the NZVI before and after the reactions indicated the formation of crystalline vivianite (Fe3(PO4)2 x 8H2O) during the procedure.

  12. 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.

  13. 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

  14. [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.

  15. Regeneration of Aqueous Periodate Solutions by Ozone Treatment: A Sustainable Approach for Dialdehyde Cellulose Production.

    Science.gov (United States)

    Koprivica, Slavica; Siller, Martin; Hosoya, Takashi; Roggenstein, Walter; Rosenau, Thomas; Potthast, Antje

    2016-04-21

    A method for easy and fast regeneration of aqueous periodate solutions from dialdehyde cellulose (DAC) production by ozone treatment is presented, along with a direct and reliable simultaneous quantification of iodate and periodate by reversed-phase HPLC. The influence of iodate and ozone concentration, solution pH, and reaction time on the regeneration efficiency was studied, as well as the reaction kinetics. Regeneration of spent periodate solutions by ozone was successfully performed in alkaline medium, which favors the formation of free (.) OH radicals, as supported by the addition of radical scavengers and quantum mechanical calculations. At pH 13 and an ozone concentration of approximately 150 mg L(-1) , periodate was completely regenerated from a 100 mm solution of iodate within 1 h at room temperature. A cyclic process of cellulose oxidation and subsequent regeneration of spent periodate with 90 % efficiency has been developed. So far, commercial applications of DAC have been hampered by difficulties in reusing the costly periodate. This work overcomes this hurdle and presents a highly efficient, clean, and low-cost protocol for the preparation of DAC with integrated periodate recycling, with the possibility of scaling the process up.

  16. Conformational changes in human serum albumin induced by sodium perfluorooctanoate in aqueous solutions.

    Science.gov (United States)

    Messina, Paula V; Prieto, Gerardo; Ruso, Juan M; Sarmiento, Félix

    2005-08-18

    Conformational changes in the bulk solution and at the air-aqueous interface of human serum albumin (HSA) induced by changes in concentration of sodium perfluorooctanoate (C(7)F(15)COO(-)Na(+)) were studied by difference spectroscopy, zeta-potential data, and axisymmetric drop shape analysis. zeta-potential was used to monitor the formation of the HSA-C(7)F(15)COO(-)Na(+) complex and the surface charge of the complex. The conformational transition of HSA in the bulk solution was followed as a function of denaturant concentration by absorbance measurements at 280 nm. The data were analyzed to obtain values for the Gibbs energies of the transition in water (DeltaG(0)(W)) and in a hydrophobic environment (DeltaG(0)(hc)) pertaining to saturated protein-surfactant complexes. The conformational changes that surfactants induce in HSA molecules alter its absorption behavior at the air-water interface. Dynamic surface measurements were used to evaluate this behavior. At low [C(7)F(15)COO(-)Na(+)], proteins present three adsorption regimes: induction time, monolayer saturation, and interfacial gelation. When surfactant concentration increases and conformational changes in the bulk solution occur, the adsorption regimes disappear. HSA molecules in an intermediate conformational state migrate to the air-water interface and form a unique monolayer. At high [C(7)F(15)COO(-)Na(+)], the adsorption of denatured molecules exhibits a behavior analogous to that of dilute solutions.

  17. 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.

  18. 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

  19. 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.

  20. Sonochemical synthesis of silver nanorods by reduction of silver nitrate in aqueous solution.

    Science.gov (United States)

    Zhu, Yu-ping; Wang, Xi-kui; Guo, Wei-lin; Wang, Jin-gang; Wang, Chen

    2010-04-01

    The sonochemical synthesis of silver nanorods has been achieved by ultrasonic irradiation of the aqueous solution of silver nitrate, methenamine (HMTA) and poly (vinyl pyrrolidone) (PVP) for 60 min. The silver nanorods obtained have lengths of 4-7 microm and mean diameters of about 100 nm. The structures of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD), and the chemical composition of the sample was examined by energy-dispersive X-ray spectrum (EDS). The effects of the irradiation time, the concentration of PVP and the reaction temperature on the morphology of silver nanorods were discussed, and the mechanism of the silver nanorods formation was tentatively inferred.

  1. Interpolymer reactions of nonionic polymers with polyacrylic acid in aqueous solutions

    Directory of Open Access Journals (Sweden)

    E. Shaikhutdinov

    2012-03-01

    Full Text Available Results of fundamental investigations in the intermacromolecular reactions and interpolymer complexes to be performed by authors with co-workes within last 20 years have been intergrated and summarized in the present review. The raw of fundamental regularities in the effect of factors of different nature (pH, ionic strength, temperature, hydrophilic-hydrophobic balance of macrochain, etc. on the complexation of nonionic polymers with polycarboxylic acids in aqueous solutions has been revealed. Critical pH upon complexation (pHcrit. has been used for evaluation of the complexing ability of the polymers. It was shown tha tdepending on pHcrit. all systems can be divided into 2 groups, namely, weak complexing and strongly complexing. The existence of two critical pH upon complexation responsible for formation typical interpolymer complexes and hydrophilic associations has been demonstrated by the method of luminescence spectroscopy.

  2. Magnetic field effects on copper metal deposition from copper sulfate aqueous solution.

    Science.gov (United States)

    Udagawa, Chikako; Maeda, Aya; Katsuki, Akio; Maki, Syou; Morimoto, Shotaro; Tanimoto, Yoshifumi

    2014-05-01

    Effects of a magnetic field (≤0.5 T) on electroless copper metal deposition from the reaction of a copper sulfate aqueous solution and a zinc thin plate were examined in this study. In a zero field, a smooth copper thin film grew steadily on the plate. In a 0.38 T field, a smooth copper thin film deposited on a zinc plate within about 1 min. Then, it peeled off repeatedly from the plate. The yield of consumed copper ions increased about 2.1 times compared with that in a zero field. Mechanism of this magnetic field effect was discussed in terms of Lorentz force- and magnetic force-induced convection and local volta cell formation.

  3. Aromatic quinoxaline as corrosion inhibitor for bronze in aqueous chloride solution

    Indian Academy of Sciences (India)

    N Saoudi; A Bellaouchou; A Guenbour; A Ben Bachir; E M Essassi; M El Achouri

    2010-06-01

    A new corrosion inhibitor, viz. 3-ethyl-6-méthyl-quinoxalin-2-one, 1-benzyl-6-methyl-quinoxalin- 2-one, 2-benzyloxy-3,6-dimethyl-quinoxaline, 1-benzyl-3-methyl-quinoxalin-2-one, were synthesized in the laboratory. Their influence on the inhibition on corrosion of bronze in aqueous chloride solution (3% NaCl) was studied by electrochemical polarization methods and weight-loss measurements. The impact of temperature on the effectiveness of the substances mentioned above has been determined between 20 and 60°C. The results showed that the corrosion resistance was greatly enhanced in the presence of inhibitor and that the effectiveness depends on some physicochemical properties of the molecule, related to its functional groups. These compounds act through the formation of a protective film on the surface of the alloy.

  4. [Investigation of the oxidation reaction of O3 with bromide ion in aqueous solution].

    Science.gov (United States)

    Yu, Xiao-Ting; Zhang, Jia-Hui; Pan, Xun-Xi; Zhang, Ren-Xi; Hou, Hui-Qi

    2012-09-01

    The reaction mechanism of O3 with bromide ion in aqueous solution was studied by ion chromatography and UV-Vis spectrometry instruments. Ion chromatography analysis showed that only 10% of Br- which was oxidized by ozone was formed into bromate ion. The results demonstrated that the final products of the oxidation reaction were identified as Br2 and Br3- except for BrO3-. The formation of Br3- which was yielded from the reaction of Br2 with Br- was the major process in the reaction of Br attacked by O3. The characteristic absorption spectrum of Br3- with an absorption peak at 260 nm was also investigated. The results may provide helpful information about the mechanism of the oxidation reaction of Br- with O3 and fate of Br- or its derivatives in the environment by the oxidation processes.

  5. Gamma-irradiation of malic acid in aqueous solutions. [prebiotic significance

    Science.gov (United States)

    Negron-Mendoza, A.; Graff, R. L.; Ponnamperuma, C.

    1980-01-01

    The gamma-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 nonvolatile products. Thin layer chromatography 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 gamma-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.

  6. 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.

  7. Bioactive and Antibacterial Glass Powders Doped with Copper by Ion-Exchange in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Marta Miola

    2016-05-01

    Full Text Available In this work, two bioactive glass powders (SBA2 and SBA3 were doped with Cu by means of the ion-exchange technique in aqueous solution. SBA2 glass was subjected to the ion-exchange process by using different Cu salts (copper(II nitrate, chloride, acetate, and sulphate and concentrations. Structural (X-ray diffraction-XRD, morphological (Scanning Electron Microscopy-SEM, and compositional (Energy Dispersion Spectrometry-EDS analyses evidenced the formation of crystalline phases for glasses ion-exchanged in copper(II nitrate and chloride solutions; while the ion-exchange in copper(II acetate solutions lead to the incorporation of higher Cu amount than the ion-exchange in copper(II sulphate solutions. For this reason, the antibacterial test (inhibition halo towards S. aureus was performed on SBA2 powders ion-exchanged in copper(II acetate solutions and evidenced a limited antibacterial effect. A second glass composition (SBA3 was developed to allow a greater incorporation of Cu in the glass surface; SBA3 powders were ion-exchanged in copper(II acetate solutions (0.01 M and 0.05 M. Cu-doped SBA3 powders showed an amorphous structure; morphological analysis evidenced a rougher surface for Cu-doped powders in comparison to the undoped glass. EDS and X-ray photoelectron spectroscopy (XPS confirmed the Cu introduction as Cu(II ions. Bioactivity test in simulated body fluid (SBF showed that Cu introduction did not alter the bioactive behaviour of the glass. Finally, inhibition halo test towards S. aureus evidenced a good antimicrobial effect for glass powders ion-exchanged in copper(II acetate solutions 0.05 M.

  8. 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...

  9. 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℃,

  10. 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

  11. 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.

  12. 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.)

  13. 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.)

  14. 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.

  15. The interactions between cationic cellulose and Gemini surfactant in aqueous solution.

    Science.gov (United States)

    Zhao, Shaojing; Cheng, Fa; Chen, Yu; Wei, Yuping

    2016-05-05

    Due to the extensive application of cationic cellulose in cosmetic, drug delivery and gene therapy, combining the improvement effect of surfactant-cellulose complexes, to investigate the properties of cellulose in aqueous solution is an important topic from both scientific and technical views. In this study, the phase behavior, solution properties and microstructure of Gemini surfactant sodium 5-nonyl-2-(4-(4-nonyl-2-sulfonatophenoxy)butoxy)phenyl sulfite (9-4-9)/cationic cellulose (JR400, the ammonium groups are directly bonded to the hydroxyethyl substituent with a degree substitution of 0.37) mixture was investigated using turbidity, fluorescence spectrophotometer and shear rheology techniques. As a control, the interaction of corresponding monovalent surfactant, sodium 2-ethoxy-5-nonylbenzenesulfonate (9-2) with JR400 in aqueous solution was also studied. Experimental results showed that 9-4-9/JR400 mixture has lower critical aggregation concentration (CAC) and critical micelle concentration (CMC) (about one order of magnitude) than 9-2/JR400 mixture. A low concentration of Gemini surfactant 9-4-9 appeared to induce an obvious micropolarity and viscosity value variation of the mixture, while these effects required a high concentration of corresponding monovalent one. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements illuminated the formation and collapse procedure of network structure of the 9-4-9/JR400 mixture, which resulted in the increase and decrease of viscosity. These results suggest that the molecular structure of the surfactant has a great effect on its interaction with cationic cellulose. Moreover, the Gemini surfactant/cationic cellulose mixture may be used as a potencial stimuli-responsive drug delivery vector which not only load hydrophilic drugs, but also deliver hydrophobic substances.

  16. [Regularities of formation of chlorophyll-human serum albumin functionally active complexes in the aqueous medium].

    Science.gov (United States)

    Semichaevskiĭ, V D

    1975-01-01

    In the system with constant content of the chlorophyll a and increasing amounts of human serum albumin, dependence of pigment incorporation into the complex upon interaction of its aqueous associates with protein solutions was studied by applying the gel filtration on Sephadex G-75 and by measuring light scattering and rate of sensitized photoreduction of the methyl red by ascorbic-acid. The curves were obtained after extraction of the chlorophyll by acetone from dry pigment-protein films formed after desiccation of the aqueous systems. Sigmoid character of the above dependences, their linearization in Hill's coordinates and the value of cooperativity coefficient close to 2 testifies in favour of the cooperative character of the complex formation, two pigment molecules reacting with a single protein molecule. Measurement of adsorption isotherms and their treatment with use of the Brunauer-Emmett-Teller theory of polymolecular adsorption make it possible to evaluate the maximum molar ratio of the pigment to the protein in the complex (close to 2). The pigment-pigment interaction suggests that the chlorophyll molecules adsorbed on the protein are in the state of loosely packed dimers. Deaggregation of aqueus pigment associates by the protein in the course of complex formation results in a considerable increase of the protosensitizing chlorophyll activity.

  17. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  18. Interactions of nitric oxide with copper(II) dithiocarbamates in aqueous solution.

    Science.gov (United States)

    Díaz, Alicia; Ortiz, Mayreli; Sánchez, Ileana; Cao, Roberto; Mederos, Alfredo; Sanchiz, Joaquin; Brito, Felipe

    2003-07-01

    This is the first report on the formation of air-stable copper nitrosyl complexes. The interaction of nitric oxide, NO, with Cu(DTC)(2).3H(2)O (DTC: dithiocarbamate) and was studied in aqueous solution at pH 7.4 and 293 K. The stability constants were determined from UV-Vis data, using LETAGROP program. The high values obtained, log beta(1)=9.743(5) and log beta(2)=15.44(2) for Cu(ProDTC)(2)-NO, (ProDTC=L-prolinedithiocarbamate) and log beta(1)=8.723(5) and log beta(2)=11.45(2) for Cu(MorDTC)(2)-NO system, (MorDTC=morpholyldithiocarbamate), indicate the formation of two stable nitrosyl complexes, Cu(DTC)(2)NO and Cu(DTC)(2)(NO)(2). Coordinated NO is neither affected by the presence of air nor when the solution is purged with Ar. Cu(MorDTC)(2)NO.3H(2)O was isolated in the solid state and its nuNO (IR) band at 1682 cm(-1), but affected by temperature variations over 333 K.

  19. Environmentally persistent free radicals (EPFRs)-2. Are free hydroxyl radicals generated in aqueous solutions?

    Science.gov (United States)

    Khachatryan, Lavrent; Dellinger, Barry

    2011-11-01

    A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (·OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: (1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, (2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and (3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/mL EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μL phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however, the exact chemical mechanism deserves further study in light of the implication of formation of bound, rather than free, hydroxyl radicals.

  20. Hybrid multiwalled carbon nanotube--Laponite sorbent for removal of methylene blue from aqueous solutions.

    Science.gov (United States)

    Loginov, Maksym; Lebovka, Nikolai; Vorobiev, Eugene

    2014-10-01

    The article discusses adsorption of methylene blue dye by novel hybrid sorbent consisting of Laponite and multiwalled carbon nanotubes. The sorbent was obtained by sonication of the aqueous suspensions of nanotubes at different concentrations of Laponite. The methods of the methylene blue adsorption, dead-end membrane filtration and environmental scanning electron microscopy were used for the sorbent characterization. It may be concluded from the results of filtration and adsorption experiments that sonication of mixed aqueous suspensions of Laponite and multiwalled carbon nanotubes leads to the formation of hybrid particles (ML-particles) with a core-shell structure. The size and the shape of hybrid particles were determined by nanotubes, while their adsorption properties were determined by Laponite particles attached to the surface of nanotubes. The Laponite content in hybrid particles was corresponding to the Laponite to nanotubes ratio in the initial suspension X(L)=0-1. Due to the presence of Laponite in the sorbent, its adsorbing capacity was much higher as compared to the adsorbing capacity of pure nanotubes, and it was directly proportional to the Laponite content. This sorbent may be used either as a purifying additive or as a filtering layer if it is deposited on the surface of a supporting membrane. Due to relatively large size of hybrid particles, they can be easily separated from the purified solution by filtration or centrifugation.

  1. Effect of plasticizer on surface of free films prepared from aqueous solutions of salts of cationic polymers with different plasticizers

    Science.gov (United States)

    Bajdik, János; Fehér, Máté; Pintye-Hódi, Klára

    2007-06-01

    Acquisition of a more detailed understanding of all technological processes is currently a relevant tendency in pharmaceutical technology and hence in industry. A knowledge of film formation from dispersion of polymers is very important during the coating of solid dosage forms. This process and the structure of the film can be influenced by different additives. In the present study, taste-masking films were prepared from aqueous citric acid solutions of a cationic polymer (Eudragit ® E PO) with various hydrophilic plasticizers (glycerol, propylene glycol and different poly(ethylene glycols)). The mechanical properties, film thickness, wetting properties and surface free energy of the free films were studied. The aim was to evaluate the properties of surface of free films to predict the arrangement of macromolecules in films formed from aqueous solutions of salts of cationic polymers. A high molecular weight of the plasticizer decreased the work of deformation. The surface free energy and the polarity were highest for the film without plasticizer; the hydrophilic additives decreased these parameters. The direction of the change in polarity (a hydrophilic component caused a decrease in the polarity) was unexpected. It can be explained by the change in orientation of the macromolecules, a hydrophobic surface being formed. Examination of the mechanical properties and film thickness can furnish additional results towards a knowledge of film formation by this not frequently applied type of polymer from aqueous solution.

  2. Thermodynamic properties of micellization of Sulfobetaine-type Zwitterionic Gemini Surfactants in aqueous solutions--a free energy perturbation study.

    Science.gov (United States)

    Liu, Guoyu; Gu, Daming; Liu, Haiyan; Ding, Wei; Luan, Huoxin; Lou, Yanmin

    2012-06-01

    In this article, the validity and accuracy of the free energy perturbation (FEP) model used in a previous article for ionic liquid-type Gemini imidazolium surfactants (ILGISs) is further evaluated by using it to model the Enthalpy-entropy compensation of Sulfobetaine-type Zwitterionic Gemini Surfactants (SZGSs), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. In the FEP model, the Gibbs free energy contributions to the driving force for micelle formation are computed using hydration data obtained from molecular dynamics simulations. According to the pseudo-phase separation model, the thermodynamic properties of micellization in aqueous solutions for SZGS were discussed. The results show that the micellization of SZGS in aqueous solutions is a spontaneous and entropy-driven process. It is linearly Enthalpy-entropy compensated and different from the micelle formation of ILGIS but similar to anionic surfactants. The compensation temperature was found to be (302±3)K which was lower than ILGIS. As the temperature rises, the micellization is easy initially but then becomes difficult with the unusual changes of enthalpy values from positive to negative. The contribution of entropy change to the micellization tends to decrease but the contribution of enthalpy change tends to increase. In particular, as the number carbon atoms in the alkyl chains and spacer chains are increased, the thermodynamic favorability and stability of the micelles both increase.

  3. Separation of compounds with multiple -OH groups from dilute aqueous solutions via complexation with organoboronate

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Tina Kuo Fung

    1992-05-01

    The complexing extractant agent investigated in this work is 3-nitrophenylboronic acid (NPBA) in its anionic form (NPB). NPBA and Aliquat 336 (quaternary amine) is dissolved in 2-ethyl-l-hexanol, and the extractant is contacted with aq. NaOH. Solutes investigated were 1,2-propanediol, glycerol, fructose, sorbitol and lactic acid. Batch extraction experiments were performed at 25{degree}C. Partition coefficients, distribution ratios and loadings are reported for varying concentrations of solute and NPB. All solutes complexed with NPB{sup {minus}}, with all complexes containing only one NPB{sup {minus}} per complex. The 1:1 complexation constants for the solutes glycerol, fructose and sorbitol follow trends similar to complexation with B(OH){sub 4}{sup {minus}} (aq.), i.e. the complexation constants increase with increasing number of {minus}OH groups available for complexation. Assumption of 1:1 complex is not valid for 1, 2-propanediol, which showed overloading (more than one mole of solute complexed to one mole NPB{sup {minus}}) at higher concentrations. The {minus}OH group on the NPB{sup {minus}} which is left uncomplexed after one solute molecule had bound to the other two {minus}OH groups may be responsible for the overloading. Overloading is also observed in extraction of tactic acid, but through a different mechanism. It was found that TOMA{sup +} can extract lactic acid to an extent comparable to the uptake of lactic acid by NPB{sup {minus}}. The complexation is probably through formation of an acid-base ion pair. Losses of NPBA into the aqueous phase could lead to problems, poor economics in industrial separation processes. One way of overcoming this problem would be to incorporate the NPBA onto a solid support.

  4. 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.

  5. 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.

  6. 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.

  7. All-proportional solid-solution Rh–Pd–Pt alloy nanoparticles by femtosecond laser irradiation of aqueous solution with surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, Md. Samiul Islam, E-mail: samiul-phy@ru.ac.bd; Nakamura, Takahiro; Sato, Shunichi [Tohoku University, Institute of Multidisciplinary Research for Advanced Materials (Japan)

    2015-06-15

    Formation of Rh–Pd–Pt solid-solution alloy nanoparticles (NPs) by femtosecond laser irradiation of aqueous solution in the presence of polyvinylpyrrolidone (PVP) or citrate as a stabilizer was studied. It was found that the addition of surfactant (PVP or citrate) significantly contributed to reduce the mean size of the particles to 3 nm for PVP and 10 nm for citrate, which was much smaller than that of the particles fabricated without any surfactants (20 nm), and improved the dispersion state as well as the colloidal stability. The solid-solution formation of the Rh–Pd–Pt alloy NPs was confirmed by the XRD results that the diffraction pattern was a single peak, which was found between the positions corresponding to each pure Rh, Pd, and Pt NPs. Moreover, all the elements were homogeneously distributed in every particle by STEM-EDS elemental mapping, strongly indicating the formation of homogeneous solid-solution alloy. Although the Rh–Pd–Pt alloy NPs fabricated with PVP was found to be Pt rich by EDS observation, the composition of NPs fabricated with citrate almost exactly preserved the feeding ratio of ions in the mixed solution. To our best knowledge, these results demonstrated for the first time, the formation of all-proportional solid-solution Rh–Pd–Pt alloy NPs with well size control.

  8. 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.

  9. Hybrid Silk Fibers Dry-Spun from Regenerated Silk Fibroin/Graphene Oxide Aqueous Solutions.

    Science.gov (United States)

    Zhang, Chao; Zhang, Yaopeng; Shao, Huili; Hu, Xuechao

    2016-02-10

    Regenerated silk fibroin (RSF)/graphene oxide (GO) hybrid silk fibers were dry-spun from a mixed dope of GO suspension and RSF aqueous solution. It was observed that the presence of GO greatly affect the viscosity of RSF solution. The RSF/GO hybrid fibers showed from FTIR result lower β-sheet content compared to that of pure RSF fibers. The result of synchrotron radiation wide-angle X-ray diffraction showed that the addition of GO confined the crystallization of silk fibroin (SF) leading to the decrease of crystallinity, smaller crystallite size, and new formation of interphase zones in the artificial silks. Synchrotron radiation small-angle X-ray scattering also proved that GO sheets in the hybrid silks and blended solutions were coated with a certain thickness of interphase zones due to the complex interaction between the two components. A low addition of GO, together with the mesophase zones formed between GO and RSF, enhanced the mechanical properties of hybrid fibers. The highest breaking stress of the hybrid fibers reached 435.5 ± 71.6 MPa, 23% improvement in comparison to that of degummed silk and 72% larger than that of pure RSF silk fiber. The hybrid RSF/GO materials with good biocompatibility and enhanced mechanical properties may have potential applications in tissue engineering, bioelectronic devices, or energy storage.

  10. Radiolysis of pyridoxine (vitamin B 6) in aqueous solution under different conditions

    Science.gov (United States)

    Albarrán, Guadalupe; Ramírez-Cahero, Fernando; Aliev, Roustam

    2008-05-01

    Aqueous solutions of pyridoxine (1 mM) without or with additive of K 3[Fe(CN) 6] (2.5 mM) were gamma-irradiated at different doses and dose rate of 2.16 kGy/h in the absence of air, in the presence of air or by their saturation with N 2O. The radiolytic products were analyzed with HPLC, mass spectrometry and UV spectroscopy. 2,4,5-Trihydroxymethyl-3-pyridinol, pyridoxal, isopyridoxal and 6-hydroxypyridoxine were formed by radiolysis in the absence of K 3[Fe(CN) 6], and their concentrations were much higher in samples saturated with N 2O. Pyridoxi-3,6-quinone was found by radiolysis under all the above-mentioned conditions but only in the presence of K 3[Fe(CN) 6]. Besides, the pyridoxal formation increased in the presence of this oxidizing agent. G values of pyridoxal formation and pyridoxine degradation were quantified. Some details of the radiolytic product formation were discussed.

  11. Photophysical efficiency-boost of aqueous aluminium phthalocyanine by hybrid formation with nano-clays.

    Science.gov (United States)

    Staniford, Mark C; Lezhnina, Marina M; Gruener, Malte; Stegemann, Linda; Kuczius, Rauni; Bleicher, Vera; Strassert, Cristian A; Kynast, Ulrich H

    2015-09-11

    Novel organic-inorganic hybrid materials comprising nanoscaled layered silicates and native aluminium hydroxide phthalocyanine (Al(OH)Pc) allowed for the first time the exploitation of their unique photophysical properties in aqueous ambience. In particular, we were able to observe the efficient emission of Al(OH)Pc-nanoclay hybrids and generation of singlet oxygen in aqueous solution.

  12. The nature of aqueous solutions: insights into multiple facets of chemistry and biochemistry from freezing-point depressions.

    Science.gov (United States)

    Zavitsas, Andreas A

    2010-05-25

    Contrary to current widely held beliefs, many concentrated aqueous solutions of electrolytes and nonelectrolytes behave ideally. For both, the same simple equation yields mole fractions of water that are equal to the theoretical activities of water. No empirical activity coefficients or ad hoc parameters are needed. Thermodynamic hydration numbers and the number of particles produced per mole of solute are found by searching freezing-point depression measurements, as if asking the water, "How much available water solvent is left and how many solute particles are there?" The results answer questions currently under debate: Do solutes alter the nature of water outside their immediate surroundings? What is the number of ion pairs formed by various electrolytes and what affects extents of their formation? What are some factors that cause precipitation of proteins, latexes, and so forth from aqueous solutions upon addition of other solutes (Hofmeister series)? Which nonelectrolytes form aggregates in water and what are the implications? Why do different solutes affect viscosity differently? How do ion-selective channels in cell membranes function at the molecular level?

  13. 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.

  14. XPS of fast-frozen hematite colloids in NaCl aqueous solutions: I. Evidence for the formation of multiple layers of hydrated sodium and chloride ions induced by the {001} basal plane

    Energy Technology Data Exchange (ETDEWEB)

    Shchukarev, Andrei; Boily, Jean F.; Felmy, Andrew R.

    2007-12-13

    The influence of the {001} basal plane of hematite on the composition of fast-frozen centrifuged wet pastes of hematite prepared at pH 4 and 9 and at ionic strengths of 0, 10 and 100 mM NaCl was investigated by x-ray photoelectron spectroscopy. Two hematite preparations consisted of micrometer-sized platelets with 42% (HEM-1) and 95% (HEM-8) of the surface terminated by the {001} basal plane. A third preparation of spherical shape with no recognizable crystal plane (HEM-control) was used as a control to these experiments. All hematite samples responded to changes in pH and ionic strength, showing that acid/base reactions of surface hydroxyl groups control the composition of the paste. The HEM-1 and HEM-8 sample exhibited divergent properties at the highest ionic strength (100 mM) with energy loss features in the Na 1s and Cl 2p spectra and an important water content. As the spectra were typical of hydrated Na+ and Cl- ions and that the surface concentrations were unusually large, the HEM-1 and HEM-8 samples are proposed to induce the formation of a three-dimensional distribution of these ions in the paste. The sodium, chloride and water content was also correlated to the fraction of the {001} basal plane present in the sample and provided evidence for an approximate stochiometric Na:Cl:H2O ratio of 1:1:2. The {001} basal plane of hematite is consequently proposeD to be the cause of this feature.

  15. Simulation of 3D mesoscale structure formation in concentrated aqueous solution of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19). Application of dynamic mean-field density functional theory

    NARCIS (Netherlands)

    van Vlimmeren, BAC; Maurits, NM; Zvelindovsky, AV; Sevink, GJA; Fraaije, JGEM

    1999-01-01

    We simulate the microphase separation dynamics of aqueous solutions of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19) by a dynamic variant of mean-field density functional theory for Ga

  16. 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.

  17. 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.

  18. 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.

  19. Gum karaya based hydrogel nanocomposites for the effective removal of cationic dyes from aqueous solutions

    Science.gov (United States)

    Mittal, Hemant; Maity, Arjun; Ray, Suprakas Sinha

    2016-02-01

    Biodegradable hydrogel nanocomposites (HNC) of gum karaya (GK) grafted with poly(acrylic acid) (PAA) incorporated silicon carbide nanoparticles (SiC NPs) were synthesized using the in situ graft copolymerization method and tested for the adsorption of cationic dyes from aqueous solution. The structure and morphology of the HNC were characterized using different spectroscopic and microscopic techniques. The results showed that the surface area and porosity of the hydrogel polymer significantly increased after nanocomposite formation with SiC NPs. The HNC was employed for the removal of cationic dyes, i.e., malachite green (MG) and rhodamine B (RhB) from the aqueous solution. The HNC was found to remove 91% (MG) and 86% (RhB) of dyes with a polymer dose of 0.5 and 0.6 g l-1 in neutral medium, respectively. The adsorption process was found to be highly pH dependent and followed the pseudo-second-order rate model. The adsorption isotherm data fitted well with the Langmuir adsorption isotherm with a maximum adsorption capacity of 757.57 and 497.51 mg g-1 for MG and RhB, respectively. Furthermore, the HNC was demonstrated as a versatile adsorbent for the removal of both cationic and anionic dyes from the simulated wastewater. The HNC showed excellent regeneration capacity and was successfully used for the three cycles of adsorption-desorption. In summary, the HNC has shown its potential as an environment friendly and efficient adsorbent for the adsorption of cationic dyes from contaminated water.

  20. Aqueous-solution synthesis of uniform PbS nanocubes and their optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuan; Li, Qing, E-mail: qli@swu.edu.cn; Wu, Huijie [Southwest University, Institute for Clean Energy & Advanced Materials, Faculty of Materials & Energy (China); Huang, Chengzhi [Southwest University, College of Pharmaceutical Sciences (China); Lin, Hua; Qin, Lizhao [Southwest University, Institute for Clean Energy & Advanced Materials, Faculty of Materials & Energy (China)

    2015-09-15

    PbS nanocubes with uniform size were generated conveniently in aqueous solution at 100 °C. The products were characterized by XRD, FESEM, TEM, UV–Vis–NIR, PL, DLS, Raman, and FT-IR techniques. The mean edge length of the nanocubes is 60 nm and is in high yield. UV–Vis–NIR absorption spectrum indicated that the sample exhibits a blue-shift from 3024 to 288 nm and PL spectrum also indicated that the sample exhibits a blue-shift from 3200 to 328 nm, compared with bulk PbS, respectively. Dark-field light scattering measurements showed that the nanocubes-scattered orange light have a broad absorption band around 610 nm. Such a special property demonstrates that the PbS nanocubes may find potential application in molecular imaging and in vivo cancer diagnosis and therapy. By investigating the intermediates of the reaction process, we observed the important coarse rod-like structures that formed by PbS particles attached to one another at the initial stage of reaction. Then the particle-joint structures decomposed and finally formed PbS nanocubes. Such a morphology evolution of PbS crystals could be summarized as “particle–rod–cube mechanism,” which might be model systems for understanding the growth process of other kinds of nanocubes and directing their synthesis. Graphical Abstract: High-yield PbS nanocubes with an edge length of 60 nm were fabricated successfully in aqueous solution at 100 °C by the assistance of surfactant CTAB. It has been found that the reaction time, temperature, and CTAB play important roles in the formation of uniform PbS nanocubes. A possible growth mechanism called “particle–rod–cube” has been discussed.

  1. Oxidative degradation of alternative gasoline oxygenates in aqueous solution by ultrasonic irradiation: Mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Duk Kyung, E-mail: dkim@aum.edu [Department of Physical Science, Auburn University Montgomery, Montgomery, AL 36117 (United States); O' Shea, Kevin E., E-mail: osheak@fiu.edu [Department of Chemistry and Biochemistry, Florida International University, University Park, Miami, FL 33199 (United States); Cooper, William J. [Department of Civil and Environmental Engineering, Urban Water Research Center, University of California Irvine, Irvine, CA 92697-2175 (United States)

    2012-07-15

    Widespread pollution has been associated with gasoline oxygenates of branched ethers methyl tert-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), and tert-amyl ether (TAME) which enter groundwater. The contaminated plume develops rapidly and treatment for the removal/destruction of these ethers is difficult when using conventional methods. Degradation of MTBE, with biological methods and advanced oxidation processes, are rather well known; however, fewer studies have been reported for degradation of alternative oxygenates. Degradation of alternative gasoline oxygenates (DIPE, ETBE, and TAME) by ultrasonic irradiation in aqueous oxygen saturation was investigated to elucidate degradation pathways. Detailed degradation mechanisms are proposed for each gasoline oxygenate. The common major degradation pathways are proposed to involve abstraction of {alpha}-hydrogen atoms by hydroxyl radicals generated during ultrasound cavitation and low temperature pyrolytic degradation of ETBE and TAME. Even some of the products from {beta}-H abstraction overlap with those from high temperature pyrolysis, the effect of {beta}-H abstraction was not shown clearly from product study because of possible 1,5 H-transfer inside cavitating bubbles. Formation of hydrogen peroxide and organic peroxides was also determined during sonolysis. These data provide a better understanding of the degradation pathways of gasoline oxygenates by sonolysis in aqueous solutions. The approach may also serve as a model for others interested in the details of sonolysis. - Highlights: Black-Right-Pointing-Pointer Gasoline oxygenates (ETBE, TAME, DIPE) were completely degraded after 6 hours under ultrasonic irradiation in O{sub 2} saturation. Black-Right-Pointing-Pointer The major degradation pathways were proposed to involve abstraction of {alpha}-hydrogen atoms by hydroxyl radicals and low temperature pyrolytic degradation. Black-Right-Pointing-Pointer The effect of {beta

  2. Mechanisms of iron-silica aqueous interaction and the genesis of Precambrian iron formation

    Science.gov (United States)

    Chemtob, S. M.; Catalano, J. G.; Moynier, F.; Pringle, E. A.

    2015-12-01

    Iron formations (IFs), Fe- and Si-rich chemical sediments common in Precambrian successions, preserve key information about the compositional, biological, and oxidative evolution of the Precambrian ocean. Stable Si isotopes (δ30Si) of IF have been used to infer paleo-oceanic composition, and secular variations in δ30Si may reflect ancient biogeochemical cycles. The δ30Si of primary Fe-Si precipitates that formed IF depends not only on the δ30Si of aqueous silica but also on the precipitation mechanism. Multiple formation mechanisms for these primary precipitates are plausible. Aqueous Si may have adsorbed on newly precipitated iron oxyhydroxide surfaces; alternatively, Fe and Si may have coprecipitated as a single phase. Here we explore variations in the Si isotope fractionation factor (ɛ) with Fe-Si aqueous interaction mechanism (adsorption vs. coprecipitation). In adsorption experiments, sodium silicate solutions (pH 8.1, 125-2000 µM Si) were reacted with iron oxide particles (hematite, ferrihydrite, goethite, and magnetite) for 24 to 72 hours. Resultant solutions had δ30Si between 0 and +6‰. Calculated ɛ varied significantly with oxide mineralogy and morphology. For ferrihydrite, ɛ = -1.7‰; for hematite, ɛ = -2 to -5‰, depending on particle morphology. Apparent ɛ decreased upon surface site saturation, implying a smaller isotope effect for polymeric Si adsorption than monomeric adsorption. In coprecipitation experiments, solutions of Na-silicate and Fe(II) chloride (0.4-10 mM) were prepared anaerobically, then air-oxidized for 3 days to induce precipitation. At low Si concentrations, magnetite formed; near silica saturation, lepidocrocite and ferrihydrite formed. The Si isotope fractionation factor for coprecipitation was within the range of ɛ observed for adsorption (ɛ = -2.3 ± 1.0‰). These results indicate that the mechanism of Fe-Si interaction affects ɛ, presumably due to varying silicate coordination environments. These isotopic

  3. 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.

  4. 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

  5. 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...

  6. 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.

  7. 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

  8. 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.

  9. Inkjet printing of aqueous rivulets: Formation, deposition, and applications

    Science.gov (United States)

    Bromberg, Vadim

    The past two decades have seen an explosion of research and development into nanotechnology, ranging from synthesis of novel materials that exhibit unique behavior to the assembly of fully functional devices that hold the potential to benefit all sectors of industry and society as a whole. One significant challenge for this emerging technology is the scaling of newly developed processes to the industrial level where manufacturing should be cheap, fast and with high throughput. One approach to this problem has been to develop processes of material deposition and device fabrication via solution-based additive manufacturing techniques such as printing. Specifically, it is envisioned that (in)organic functional nanomaterial that can be processed into solution form can be deposited in a precise manner (i.e., printed) onto sheets of flexible plastic/glass in a process similar to the printing of newspaper (formally, the process is dubbed Roll-to-Roll). This work is focused on experimentally studying and developing one type of solution-based material deposition technique---drop-on-demand ink-jet printing. This technique allows highly-repeatable deposition of small (pico-liter) droplets of functional ink in precise locations on a given target substrate. Although the technology has been in existence and in continuous use for many decades in the paper graphics industry, its application to nanotechnology-based fabrication processes on non-porous substrates presents many challenges stemming from the coupling of the wetting, material transport, evaporation and solid deposition phenomena that occur when printing patterns more complex than single droplets. The focus of this research has been to investigate these phenomena for the case of printed rivulets of water-based inks. A custom ink-jet apparatus has been assembled to allow direct optical observation of the flow and deposition that occur during printing. Experimental results show the importance of substrate surface energy and

  10. 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.

  11. 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.

  12. 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. ...

  13. 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.

  14. 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.

  15. 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...

  16. Aggregation behavior modulation of 1-dodecyl-3-methylimidazolium bromide by organic solvents in aqueous solution.

    Science.gov (United States)

    Wang, Jianji; Zhang, Lamei; Wang, Huiyong; Wu, Changzeng

    2011-05-05

    Material preparation in ionic liquids and environmental pollution control by ionic liquids are often closely dependent on the aggregation behavior of ionic liquids in solution. In the present work, conductivity, fluorescence probe, and dynamic light scattering techniques have been used to study the effect of organic solvents on the aggregation behavior of 1-dodecyl-3-methylimidazolium bromide in water. It was shown that the critical aggregation concentration (CAC), the ionization degree of the aggregates (α), and the standard Gibbs energy of aggregation (ΔG(m)°) of the ionic liquid increase, while its aggregation number (N(agg)) and aggregates' size decrease with increasing concentration of organic additives in water. These results have been discussed from the favorable interactions of alkyl chain of the ionic liquid with the mixed solvents. It is suggested that the solvophobic parameter, characterized quantitatively by Gibbs energy of transfer of hydrocarbon from gas into a given solvent, can be used to account for the effect of organic additives on the formation and growth of the ionic liquid aggregates in water. Aggregation behavior of ionic liquids in aqueous organic solutions can be modulated simply by the solvophobic parameters of hydrocarbon in the mixed solvents.

  17. Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

    Indian Academy of Sciences (India)

    Maram Ravi Kumar; Mundra Adinarayana

    2000-10-01

    The photooxidation of caffeine in presence of peroxydiphosphate (PDP) in aqueous solution at natural H (∼7 5) has been carried out in a quantum yield reactor using a high-pressure mercury lamp. The reactions were followed spectrophotometrically by measuring the absorbance of caffeine at max (272 nm). The rates of reaction were calculated under different experimental conditions. The quantum yields were calculated from the rates of oxidation of caffeine and the intensity of light at 254 nm which was measured by using peroxydisulphate solution as a standard chemical actinometer. The reaction rates of oxidation of caffeine by PDP increase with increase in [PDP] as well as with increase in light intensity, while they are independent of [caffeine]. The quantum yields of oxidation of caffeine by PDP are independent of [PDP] as well as light intensity. However, quantum yields of oxidation of caffeine by PDP increase with increase in caffeine concentration. On the basis of these experimental results and product analysis, a probable mechanism has been suggested in which PDP is activated to phosphate radical anions (PO$_{4}^{\\bullet 2-}$) by direct photolysis of PDP and also by the sensitizing effect of caffeine. The phosphate radical anions thus produced react with caffeine by electron transfer reaction, resulting in the formation of caffeine radical cation, which deprotonates in a fast step to produce C8OH adduct radicals. These radicals might react with PDP to give final product 1,3,7-trimethyluric acid and PO$_{4}^{\\bullet 2-}$ radicals, the latter propagates the chain reaction.

  18. Electrospinning of diosmin from aqueous solutions for improved dissolution and oral absorption.

    Science.gov (United States)

    Vrbata, Petr; Berka, Pavel; Stránská, Denisa; Doležal, Pavel; Lázníček, Milan

    2014-10-01

    A nanofibrous membrane carrier for nearly water insoluble drug diosmin was formulated. The aim of this study was to evaluate the drug release and dissolution properties in an aqueous buffer of pH 7.8, and to compare the suitability of the drug carrier with the available drug forms and screen diosmin absorption extent. The membranes were produced from HPC/PVA/PEO-drug water solutions and then evaluated by SEM and DSC measurements. The results showed that diosmin was incorporated within the nanofibers in an amorphous state, and/or as a solid dispersion. The results of in vitro release experiments excerpt a very fast release of the drug, followed by the formation of an over saturated solution and partial precipitation of the drug (a "spring" effect). The enormous increases in dissolution of the drug from a nanofibrous carrier, compared to a micronized and crystalline form, was achieved. The in vivo bioavailability study carried out on rats showed higher initial drug plasma levels and higher AUC values after administration of the nanofibrous drug formulation, compared to the micronized form. The results of the study demonstrated that the improvement of the diosmin in vitro dissolution also brought the enhanced in vivo absorption extent of the drug.

  19. Surface Complexation at the TiO(2) (anatase)/Aqueous Solution Interface: Chemisorption of Catechol.

    Science.gov (United States)

    Rodríguez; Blesa; Regazzoni

    1996-01-15

    Catechol adsorbs at the TiO(2) (anatase)/aqueous solution interface forming inner-sphere surface complexes. The UV-visible differential reflectance spectrum of surface titanium-catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pK(a1), the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Gamma(max):N(S) (N(S) being the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH >/= pK(a1), the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO(2) suspended in indifferent electrolyte solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: identical withTiOH(1/3-) and identical withOH(1/3+). Although both surface groups undergo protonation-deprotonation reactions, only identical withTiOH(1/3-) are prone to chemisorption.

  20. Polymer-Controlled Growth of CuO Nanodiscs in the Mild Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    PENG Yin; LIU Zhengyin; YANG Zihui

    2009-01-01

    CuO nanodiscs have been synthesized on a large scale by a facile solution-based method using polymers as crystal growth modifiers. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and high resolu-tion transmission electron microscopy (HRTEM) were carded out to characterize the structures and morphologies of the obtained products. The effects of reaction temperature, concentrations of polyacrylamide (PAM) and reac-tants on the morphology and size of the product were studied. The results revealed that the CuO nanodisc had sin-gle-crystal monoclinic structures, and grew along (002) and (110) planes. Experimental conditions had all influence on the shape and size of the final products, but polymer PAM played the key role in formation of the CuO nanodisc.A possible growth mechanism of the CuO nanostructures based on typical polymer-crystal interactions in a mild aqueous solution was given. Polymer-directed crystal growth may provide promising routes to rational synthesis of various ordered inorganic and inorganic-organic hybrid materials with complex forms and structural specialization.

  1. Ultrafiltration Enhanced with Activated Carbon Adsorption for Efficient Dye Removal from Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    董亚楠; 苏延磊; 陈文娟; 彭金明; 张岩; 姜忠义

    2011-01-01

    In this study, orange G dye was efficiently removed from aqueous solution by ultraflltration (UF) membrane separation enhanced with activated carbon adsorption. The powdered activated carbon (PAC) was deposited onto the UF membrane surface, forming an intact filter cake. The enhanced UF process simultaneously exploited the high water permeation flux of porous membrane and the high adsorption ability of PAC toward dye molecules. The influencing factors on the dye removal were investigated. The results indicated that with sufficient PAC incorporation, the formation of intact PAC filtration cake led to nearly complete rejection for dye solution under opti-mized dye concentration and operation pressure, without large sacnticlng the permeation tlux ot the filtration process. Typically, the dye rejection ratio increased from 43.6% for single UF without adsorption to nearly 100% for the enhanced UF process, achieving long time continuous treatment with water permeation flux of 47 L·m^-2·h^-1. The present study demonstrated that adsorption enhanced UF may be a feasible method for the dye wastewater treatment.

  2. 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.

  3. 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.

  4. 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.

  5. Mechanisms of phosphate removal from aqueous solution by blast furnace slag and steel furnace slag

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We report the adsorption of phosphate and discuss the mechanisms of phosphate removal from aqueous solution by burst furnace slag (BFS) and steel furnace slag (SFS). The results show that the adsorption of phosphate on the slag was rapid and the majority of adsorption was completed in 5~10 min. The adsorption capacity of phosphate by the slag was reduced dramatically by acid treatment. The relative contribution of adsorption to the total removal of phosphate was 26%~28%. Phosphate adsorption on BFS and SFS follows the Freundlich isotherm, with the related constants ofk 6.372 and 1/n 1.739 for BFS, and ofk 1.705 and 1/n 1.718 for SFS. The pH and Ca2+ concentration were decreased with the addition of phosphate, suggesting the formation of calcium phosphate precipitation. At pH 2.93 and 6.93, phosphate was desorbed by about 36%~43% and 9%~11%, respectively.These results indicate that the P adsorption on the slag is not completely reversible and that the bond between the slag particles and adsorbed phosphate is strong. The X-ray diffraction (XRD) patterns of BFS and SFS before and after phosphate adsorption verify SFS is related to the formation of phosphate calcium precipitation and the adsorption on hydroxylated oxides. The results show that BFS and SFS removed phosphate nearly 100%, indicating they are promising adsorbents for the phosphate removal in wastewater treatment and pollution control.

  6. Gas-liquid partitioning of halogenated volatile organic compounds in aqueous cyclodextrin solutions

    Energy Technology Data Exchange (ETDEWEB)

    Ondo, Daniel; Barankova, Eva [Department of Physical Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic); Dohnal, Vladimir, E-mail: dohnalv@vscht.cz [Department of Physical Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic)

    2011-08-15

    Highlights: > Binding of halogenated VOCs with cyclodextrins examined through g-l partitioning. > Complex stabilities reflect host-guest size matching and hydrophobic interaction. > Presence of halogens in the guest molecule stabilizes the binding. > Thermodynamic origin of the binding varies greatly among the systems studied. > Results obey the guest-CD global enthalpy-entropy compensation relationship. - Abstract: Gas-liquid partitioning coefficients (K{sub GL}) were measured for halogenated volatile organic compounds (VOCs), namely 1-chlorobutane, methoxyflurane, pentafluoropropan-1-ol, heptafluorobutan-1-ol, {alpha},{alpha},{alpha}-trifluorotoluene, and toluene in aqueous solutions of natural {alpha}-, {beta}-, and {gamma}-cyclodextrins (CDs) at temperatures from (273.35 to 326.35) K employing the techniques of headspace gas chromatography and inert gas stripping. The binding constants of the 1:1 inclusion complex formation between the VOCs and CDs were evaluated from the depression of the VOCs volatility as a function of CD concentration. The host-guest size matching and the hydrophobic interaction concept were used to rationalize the observed widely different affinity of the VOC-CD pairs to form the inclusion complex. The enthalpic and entropic component of the standard Gibbs free energy of complex formation as derived from the temperature dependence of the binding constant indicate the thermodynamic origin of the binding to vary greatly among the systems studied, but follow the global enthalpy-entropy compensation relationships reported previously in the literature.

  7. Transformation of 1H-benzotriazole by ozone in aqueous solution.

    Science.gov (United States)

    Mawhinney, Douglas B; Vanderford, Brett J; Snyder, Shane A

    2012-07-01

    Recent studies have shown that 1H-benzotriazole is a widespread contaminant of wastewater and surface water. Although disinfection by ozone has been shown to efficiently remove this compound, the transformation products have not been identified. To that end, the reaction of ozone with 1H-benzotriazole in aqueous solution has been studied in real time employing quadrupole time-of-flight mass spectrometry (Q-TOF MS) and negative electrospray ionization. The transformation products have been identified by calculating their empirical formulas using accurate mass measurements, and further confirmed by performing the reaction with stable isotope-labeled 1H-benzotriazole and measuring product ion spectra. Stable reaction products were distinguished from transient species by plotting their extracted mass profiles. The products that resulted from ozone and hydroxyl radicals in the reaction were qualitatively identified by modifying the conditions to either promote the formation of hydroxyl radicals, or to scavenge them. Based on experimental evidence, a mechanism for the direct reaction between ozone and 1H-benzotriazole is proposed that results in the formation of 1H-1,2,3-triazole-4,5-dicarbaldehyde, which has an empirical formula of C(4)H(3)O(2)N(3). Lastly, it was confirmed that the same transformation products formed in surface water and tertiary-treated wastewater, although they were observed to degrade at higher ozone doses.

  8. Hexadecyltrimethylammonium bromide micellization in glycine, diglycine, and triglycine aqueous solutions as a function of surfactant concentration and temperatures

    Science.gov (United States)

    Ali, Anwar; Malik, Nisar Ahmad; Uzair, Sahar; Ali, Maroof; Ahmad, Mohammad Faiz

    2014-06-01

    Micellization behavior of hexadecyltrimethylammonium bromide (HTAB) was investigated conductometrically in aqueous solutions containing 0.02 mol kg-1glycine (Gly), diglycine (Gly-Gly), and triglycine (Gly-Gly-Gly) as a function of surfactant concentration at different temperatures. The critical micelle concentration (CMC) of HTAB exhibits a decreasing trend as the number of carbon atoms increases from Gly to Gly-Gly-Gly, favoring the micelle formation. The values of CMC and the degree of counterion dissociation of the micelles were utilized to evaluate the standard free energy for transferring the surfactant hydrophobic chain out of the solvent to the interior of the micelle, Δ G {HP/○}, free energy associated with the surface contributions, Δ G {S/○}, standard free energy, Δ G {m/○}, enthalpy, Δ H {m/○}, and entropy, Δ S {m/○} of micellization were also calculated. The results show that the micellization of HTAB in aqueous solutions as well as in aqueous Gly/Gly-Gly/Gly-Gly-Gly solutions is primarily governed by the entropy gain due to the transfer of the hydrophobic groups of the surfactant from the solvent to the interior part of the micelle. The CMC obtained by fluorometric method is in close agreement with those obtained conductometrically. Furthermore, decrease in the I 1/ I 3 ratio of pyrene fluorescence intensity suggests the solubilization of the additives by the surfactant micelles and that this solubilization increases as the hydrophobicity increases from Gly to Gly-Gly-Gly.

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Magnesium bicarbonate and carbonate interactions in aqueous solutions: An infrared spectroscopic and quantum chemical study

    Science.gov (United States)

    Stefánsson, Andri; Lemke, Kono H.; Bénézeth, Pascale; Schott, Jacques

    2017-02-01

    The interaction of magnesium with bicarbonate and carbonate ions in aqueous solutions was studied using infrared spectroscopy and quantum chemical calculations. Using the infrared vibrational bands for HCO3- and CO32- at 1200-1450 cm-1 (δC-OH, vS and v3) together with their molar absorptivity (ε), the concentrations of the HCO3- and CO32- ions and the corresponding Mg ion pairs have been determined. In the absence of Mg2+, measured spectra were accurately reproduced assuming that only HCO3- and CO32- were present in solution. Upon addition of Mg2+ at fixed pH, infrared spectra were observed to shift indicating presence of the MgHCO3+ and MgCO3 (aq) ion pairs. From measurements, the second ionization constant of carbonic acid and the MgHCO3+ and MgCO3 (aq) ion pair formation constants have been obtained, these being logK2 = -10.34 ± 0.04, logKMgHCO3+ = 1.12 ± 0.11 and logKMgCO3 = 2.98 ± 0.06, respectively. To support our experimental infrared measurements and to gain further insight into the molecular nature of the ion pair formation, density functional theory (DFT) calculations with VPT2 anharmonic correction were conducted. The most stable geometries predicted for the MgHCO3+ and MgCO3 (aq) ion pairs were a bi-dentate [MgHCO3]+(H2O)n and a monodentate [MgHCO3]+(OH)(H2O)n complexes, respectively. The predicted frequencies for HCO3-, CO32- and MgHCO3+ were found to shift toward those experimentally measured with an increasing H2O solvation number where possible band shifts were predicted for MgCO3 (aq) relative to CO32-, this being dependent on the exact structure and hydration of the bulk MgCO3 (aq) ion pair. Experimentally, the ion pair formations were found to have insignificant effects on the δC-OH, vS and v3 vibrational frequencies. The speciation of dissolved inorganic carbon may be significantly influenced by ion pair formation, particularly in alkaline solutions where they may be the predominant species.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Influence of pH, temperature, and concentration on stabilization of aqueous hornet silk solution and fabrication of salt-free materials.

    Science.gov (United States)

    Kameda, Tsunenori

    2015-01-01

    We found that an aqueous solution of silk from cocoons produced by hornet larvae (hornet silk) can be obtained when the solution is adjusted to basic conditions of pH > 9.2. It is known that native hornet cocoons can be dissolved in concentrated aqueous solution of salts, such as lithium bromide (LiBr) and calcium chloride (CaCl2). Upon the removal of these salts from solution by dialysis, solidification, gelation, or sedimentation of hornet silk is known to occur. In the present study, under basic conditions, however, no such solidification occurred, even after salt removal. In this study, ammonia was used for alkalization of solution because it is volatilized during the casting process and pure hornet silk materials can be obtained after drying. The effects of the concentrations of hornet silk and ammonia, as well as dialysis temperature, on preventing gelation during dialysis were investigated. Dialysis conditions that limit the degradation of hornet silk by hydrolysis in alkali solution were identified. Moreover, casting conditions to prepare flexible and transparent hornet silk film from aqueous ammonia solution were optimized. Molecular structural analysis of hornet silk in aqueous ammonia solution and cast film indicated the formation of α-helix conformations.

  12. Competition reactions of H2O•+ radical in concentrated Cl- aqueous solutions: picosecond pulse radiolysis study.

    Science.gov (United States)

    El Omar, Abdel Karim; Schmidhammer, Uli; Rousseau, Bernard; LaVerne, Jay; Mostafavi, Mehran

    2012-11-29

    Picosecond pulse-probe radiolysis measurements of highly concentrated Cl(-) aqueous solutions are used to probe the oxidation mechanism of the Cl(-). The transient absorption spectra are measured from 340 to 710 nm in the picosecond range for the ultrafast electron pulse radiolysis of halide solutions at different concentrations up to 8 M. The amount of Cl(2)(•-) formation within the electron pulse increases notably with increasing Cl(-) concentration. Kinetic measurements reveal that the direct ionization of Cl(-) cannot solely explain the significant amount of fast Cl(2)(•-) formation within the electron pulse. The results suggest that Cl(-) reacts with the precursor of the OH(•) radical, i.e., H(2)O(•+) radical, to form Cl(•) atom within the electron pulse and the Cl(•) atom reacts subsequently with Cl(-) to form Cl(2)(•-) on very short time scales. The proton transfer reaction between H(2)O(•+) and the water molecule competes with the electron transfer reaction between Cl(-) and H(2)O(•+). Molecular dynamics simulations show that number of water molecules in close proximity decreases with increasing concentration of the salt (NaCl), confirming that for highly concentrated solutions the proton transfer reaction between H(2)O(•+) and a water molecule becomes less efficient. Diffusion-kinetic simulations of spur reactions including the direct ionization of Cl(-) and hole scavenging by Cl(-) show that up to 30% of the H(2)O(•+) produced by the irradiation could be scavenged for solutions containing 5.5 M Cl(-). This process decreases the yield of OH(•) radical in solution on the picosecond time scale. The experimental results for the same concentration of Cl(-) at a given absorbed dose show that the radiation energy absorbed by counterions is transferred to Cl(-) or water molecules and the effect of the countercation such as Li(+), K(+), Na(+), and Mg(2+) on the oxidation yield of Cl(-) is negligible.

  13. 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.

  14. Emulsion of aqueous-based nonspherical droplets in aqueous solutions by single-chain surfactants: templated assembly by nonamphiphilic lyotropic liquid crystals in water.

    Science.gov (United States)

    Varghese, Nisha; Shetye, Gauri S; Bandyopadhyay, Debjyoti; Gobalasingham, Nemal; Seo, JinAm; Wang, Jo-Han; Theiler, Barbara; Luk, Yan-Yeung

    2012-07-24

    Single-chain surfactants usually emulsify and stabilize oily substances into droplets in an aqueous solution. Here, we report a coassembly system, in which single types of anionic or non-ionic surfactants emulsify a class of water-soluble nonamphiphilic organic salts with fused aromatic rings in aqueous solutions. The nonamphiphilic organic salts are in turn promoted to form droplets of water-based liquid crystals (chromonic liquid crystals) encapsulated by single-chain surfactants. The droplets, stabilized against coalescence by encapsulated in a layer (or layers) of single chain surfactants, are of both nonspherical tactoid (elongated ellipsoid with pointy ends) and spherical shapes. The tactoids have an average long axis of ∼9 μm and a short axis of ∼3.5 μm with the liquid crystal aligning parallel to the droplet surface. The spherical droplets are 5-10 μm in diameter and have the liquid crystal aligning perpendicular to the droplet surface and a point defect in the center. Cationic and zwitterionic surfactants studied in this work did not promote the organic salt to form droplets. These results illustrate the complex interplay of self-association and thermodynamic incompatibility of molecules in water, which can cause new assembly behavior, including potential formation of vesicles or other assemblies, from surfactants that usually form only micelles. These unprecedented tactoidal shaped droplets also provide potential for the fabrication of new soft organic microcapsules.

  15. 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.

  16. 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...

  17. 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.

  18. 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.

  19. 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.

  20. 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.