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Sample records for aqueous solutions experimental

  1. 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.

  2. 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.

  3. Experimental study of terrestrial plant litter interaction with aqueous solutions

    Science.gov (United States)

    Fraysse, F.; Pokrovsky, O. S.; Meunier, J.-D.

    2010-01-01

    Quantification of silicon and calcium recycling by plants is hampered by the lack of physico-chemical data on reactivity of plant litter in soil environments. We applied a laboratory experimental approach for determining the silica and calcium release rates from litter of typical temperate and boreal plants: pine ( Pinus laricio), birch ( Betula pubescens), larch ( Larix gmelinii), elm ( Ulmus laevis Pall.), tree fern ( Dicksonia squarrosa), and horsetail (Equisetum arvense) in 0.01 M NaCl solutions, pH of 2-10 and temperature equals to 5, 25 and 40 °C. Open system, mixed-flow reactors equipped with dialysis compartment and batch reactors were used. Comparative measurements were performed on intact larch needles and samples grounded during different time, sterilized or not and with addition or not of sodium azide in order to account for the effect of surface to mass ratio and possible microbiological activity on the litter dissolution rates. Litter degradation results suggest that the silica release rate is independent on dissolved organic carbon release (cell breakdown) which implies the presence of phytoliths in a pure "inorganic" pool not complexed with organic matter. Calcium and DOC are released at the very first stage of litter dissolution while Si concentration increases gradually suggesting the presence of Ca and Si in two different pools. The dry-weight normalized dissolution rate at circum-neutral pH range (approx. 1-10 μmol/g DW/day) is 2 orders of magnitude higher than the rates of Si release from common soil minerals (kaolinite, smectite, illite). Minimal Ca release rates evaluated from batch and mixed-flow reactors are comparable with those of most reactive soil minerals such as calcite and apatite, and several orders of magnitude higher than the dissolution rates of major rock-forming silicates (feldspars, pyroxenes). The activation energy for Si liberation from plant litter is approx. 50 kJ/mol which is comparable with that of surface

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

    Science.gov (United States)

    Chen, C. F.; Chen, Falin

    1991-01-01

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

  5. 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.

  6. Experimental and modeling studies on the absorption of NO in aqueous ferrous EDTA solutions

    NARCIS (Netherlands)

    Gambardella, F; Alberts, MS; Winkelman, JGM; Heeres, EJ; Alberts, Michel S.; Heeres, H.J.

    2005-01-01

    This work describes an experimental and modeling study on an industrial relevant process (i.e., the absorption of NO in aqueous Fell(EDTA) solutions) to accurately determine the equilibrium constant of the reaction in the temperature range of 299-329 K. The experiments were carried out in a stirred

  7. Analysis of experimental series of plutonium nitrate in aqueous solution and their correlation coefficients

    CERN Document Server

    Kilger, Robert; Stuke, Maik

    2016-01-01

    In this work we performed a detailed analysis on the calculation of 43 critical experiments from 6 experimental series all describing plutonium nitrate in aqueous solution contained in metal spheres. The underlying experimental data is taken from the handbook of the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Working Group. We present our modeling assumptions which were derived from the interpretation of the experimental data and discuss the resulting sensitivity analysis. Although the experiments share some components, the derived correlation coefficients are for many cases statistically not significant. Comparing our findings for the correlation coefficients with available data from the DICE Database we find an agreement for the correlation coefficients due to nuclear data. We also compare our results for the correlation coefficients due to experimental uncertainty. Our findings indicate that for the reliable Determination of correlation coefficients a detailed study of the underl...

  8. Experimental study on oxidative decomposition of nitrobenzene in aqueous solution by honeycomb ceramic-catalyzed ozonation

    Institute of Scientific and Technical Information of China (English)

    Lei ZHAO; Jun MA; Zhizhong SUN; Zhengqian LIU; Yixin YANG

    2008-01-01

    The ozonation of nitrobenzene in aqueous solu-tion was carried out in a semi-batch reactor to investigate the degradation efficiency, the effect factors, and the reaction mechanism, where honeycomb ceramic was used as a cata-lyst. The presence of honeycomb ceramic could improve the degradation rate of nitrobenzene by 15.46% compared to the results ofozonation alone. Under the conditions of this exper-iment, the degradation rate of honeycomb ceramic-catalyzed ozonation increased by 12.94% with the increase of the amount of catalyst from 1 to 5 blocks. The degradation rates all increased greatly with the increase of temperature and pH of the solution in the processes of honeycomb ceramic-catalyzed ozonation and ozonation alone. But, when the pH of the solution increased to 9.50, the advantage of the honey-comb ceramic-catalyzed ozonation process would be lost. The experimental findings indicated that in the processes of ozonation alone and honeycomb ceramic-catalyzed ozona-tion, nitrobenzene was primarily oxidized by·OH free radical in aqueous solution. The adsorption of nitrobenzene was too limited to have an important influence on the degradation rate of nitrobenzene. With the same total dosage of applied ozone, the multiple step addition of ozone showed much higher removal efficiency than that obtained by one step in the two processes.

  9. EXPERIMENTAL INVESTIGATION ON CHROMIUM(VI REMOVAL FROM AQUEOUS SOLUTION USING ACTIVATED CARBON RESORCINOL FORMALDEHYDE XEROGELS

    Directory of Open Access Journals (Sweden)

    Eghe A. Oyedoh

    2016-10-01

    Full Text Available The adsorption of chromium(VI metal ion in aqueous solutions by activated carbon resorcinol formaldehyde xerogels (ACRF was investigated. The results showed that pore structure, surface area and the adsorbent surface chemistry are important factors in the control of the adsorption of chromium(VI metal ions. The isotherm parameters were obtained from plots of the isotherms and from the application of Langmuir and Freundlich Isotherms. Based on regression analysis, the Langmuir isotherm model was the best fit. The maximum adsorption capacity of ACRF for chromium (VI was 241.9 mg/g. The pseudo-second-order kinetic model was the best fit to the experimental data for the adsorption of chromium metal ions by activated carbon resorcinol formaldehyde xerogels. The thermodynamics of Cr(VI ions adsorption onto ACRF was a spontaneous and endothermic process.

  10. EXPERIMENTAL CHARACTERIZATION OF FLUOROCARBON-MODIFIED POLYACRYLAMIDE/SURFACTANT AQUEOUS SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Huai-tian Bu; Zhen-zhong Yang; Yun-xiang Zhang

    2003-01-01

    The interaction between surfactants and fluorocarbon-modified polyacrylamide (FC-PAM) in aqueous solutions was evaluated by theological means and fluorescence spectroscopy and was found to be strong regardless of the surfactant's nature. Two representative surfactants, anionic sodium dodecyl sulfate (SDS) and nonionic Triton X-100, were used. The origin of the interaction and its dependence on the surfactant concentration were discussed.

  11. Experimental data of biomaterial derived from Malva sylvestris and charcoal tablet powder for Hg2+ removal from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Alireza Rahbar

    2016-09-01

    Full Text Available In this experimental data article, a novel biomaterial was provided from Malva sylvestris and characterized its properties using various instrumental techniques. The operating parameters consisted of pH and adsorbent dose on Hg2+ adsorption from aqueous solution using M. sylvestris powder (MSP were compared with charcoal tablet powder (CTP, a medicinal drug. The data acquired showed that M. sylvestris is a viable and very promising alternative adsorbent for Hg2+ removal from aqueous solutions. The experimental data suggest that the MSP is a potential adsorbent to use in medicine for treatment of poisoning with heavy metals; however, the application in animal models is a necessary step before the eventual application of MSP in situations involving humans.

  12. 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

  13. Indium recovery from acidic aqueous solutions by solvent extraction with D2EHPA: a statistical approach to the experimental design

    Directory of Open Access Journals (Sweden)

    Fortes M.C.B.

    2003-01-01

    Full Text Available This experimental work presents the optimization results of obtaining a high indium concentration solution and minimum iron poisoning by solvent extraction with D2EHPA solubilized in isoparaffin and exxsol. The variables studied in the extraction step were D2EHPA concentration, acidity of the aqueous phase and time of contact between phases. Different hydrochloric and sulfuric acid concentrations were studied for the stripping step. The optimum experimental conditions resulted in a solution with 99% indium extraction and less than 4% iron. The construction of a McCabe-Thiele diagram indicated two theoretical countercurrent stages for indium extraction and at least six stages for indium stripping. Finally, the influence of associated metals found in typical sulfate leach liquors from zinc plants was studied. Under the experimental conditions for maximum indium extraction, 96% indium extraction was obtained, iron extraction was about 4% and no Ga, Cu and Zn were co-extracted.

  14. Experimental and theoretical investigation of [Al(PCr)(H2O)] complex in aqueous solution

    Science.gov (United States)

    Tenório, Thaís; Lopes, Damiana C. N.; Silva, Andréa M.; Ramos, Joanna Maria; Buarque, Camilla D.

    2014-01-01

    Phosphocreatine is a phosphorylated creatine molecule synthesized in the liver and transported to muscle cells where it is used for the temporary storage of energy. In Alzheimer's disease, the capture of glucose by cells is impaired, which negatively affects the Krebs cycle, leading to problems with the generation of phosphocreatine. Furthermore, the creatine-phosphocreatine system, regulated by creatine kinase, is affected in the brains of Alzheimer's disease patients. Aluminum ions are associated with Alzheimer's disease. Al(III) decreases cell viability and increases the fluidity of the plasma membrane, profoundly altering cell morphology. In this study, one of the complexes formed by Al(III) and phosphocreatine in aqueous solution was investigated by potentiometry, 31P and 27Al NMR, Raman spectroscopy and density functional theory (DFT) calculations. The log KAlPCr value was 11.37 ± 0.03. Phosphocreatine should act as a tridentate ligand in this complex. The 27Al NMR peak at 48.92 ppm indicated a tetrahedral molecule. The fourth position in the arrangement was occupied by a coordinated water molecule. Raman spectroscopy, 31P NMR and DFT calculations (DFT:B3LYP/6-311++G**) indicated that the donor atoms are oxygen in the phosphate group, the nitrogen of the guanidine group and the oxygen of the carboxylate group. Mulliken charges, NBO charges, frontier molecular orbitals, electrostatic potential contour surfaces and mapped electrostatic potential were also examined.

  15. Experimental investigation on the absorption of alcoholic additives in an aqueous lithium bromide solution

    Energy Technology Data Exchange (ETDEWEB)

    Lonardi, Federico; Luke, Andrea [Kassel Univ. (Germany). Fachgebiet Technische Thermodynamik

    2015-07-01

    The increasing energy consumption and the scarcity of energy sources require an optimization of all technical processes. Absorption chillers represent a promising technology in order to provide a cooling demand with low-energy consumption. Indeed, such chillers are driven by low-temperature heat which is often available as waste heat from industrial processes, or can be obtained by the mean of solar collectors. On the other side, absorption chillers are not yet competitive with traditional compression chiller because of their low efficiency and reliability. One way to increase the efficiency of these chillers is by the means of additives. When added in small quantities to the working fluid, they reduce the surface tension, promoting Marangoni convection at the interface of the tube bundle of the absorber. As a consequence, the heat and mass transfer is enhanced. Although several investigations have been carried out in literature, only two kinds of additives are mostly investigated. Nevertheless, enhancement mechanism is not yet fully understood, and different theories have been proposed. In the present work, the influence of additives on the dynamic surface tension of aqueous lithium bromide solution is investigated. Common additives (2-ethylhexanol and 1-octanol) as well as new additives (3-phenyl-1-propan, 3,5,5-trymethyl-1-hexanol) are used. Surface tension is measured by the pendant-drop method. Different parameters, such as additive concentration and surrounding atmosphere, are varied during the experiment. Among the four additives investigated, 2-ethylhexanol shows the fastest absorption rate, while 3-phenyl-1-propanol has no influence in reducing the surface tension. The current study is carried out in the framework of the ITN Marie Curie ''SHINE'' research program financed by the EU.

  16. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    Science.gov (United States)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rügen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate

  17. Experimental study of the bending elasticity of charged lipid bilayers in aqueous solutions with pH5

    Science.gov (United States)

    Mitkova, D.; Stoyanova-Ivanova, A.; Ermakov, Yu A.; Vitkova, V.

    2012-12-01

    Exposure to high concentrations of contaminations due to air polluting gases, vapours and aerosols and possibly altering the normal pH in the body could lead to undesirable changes in the properties of biological cells. Here, we study experimentally the mechanical properties of synthetic phospholipid bilayers containing increasing molar fractions (up to 0.15) of charged lipid (synthetic phosphatidylserine) in aqueous solutions with controlled ionic strength and at pH 5, which is slightly lower than the physiological values of pH. Our observations in phase contrast and fluorescence testified to the coexistence of two phases in membranes for temperatures below 29°C. Micro-sized inhomogeneities in vesicle membranes were systematically observed at temperatures lower than 29°C and for molar fractions of phosphatidylserine in the bilayer higher than 0.1. For the quantitative determination of the membrane bending rigidity, we applied thermal fluctuation analysis of the shape of quasispherical lipid vesicles. As far as the liquid-crystalline state of the bilayer is a necessary condition for the application of the experimental method, only vesicles satisfying this requirement were processed for determination of their membrane bending rigidity. The value obtained for the bending modulus of bilayers with 0.15 molar content of charged lipid is about two times higher than the bending modulus of uncharged membranes in the same bathing solution. These findings are in qualitative agreement with our previous results for the bending rigidity of charged bilayers, measured by vesicle micromanipulation.

  18. Response surface modeling of Pb(II) removal from aqueous solution by Pistacia vera L.: Box-Behnken experimental design.

    Science.gov (United States)

    Yetilmezsoy, Kaan; Demirel, Sevgi; Vanderbei, Robert J

    2009-11-15

    A three factor, three-level Box-Behnken experimental design combining with response surface modeling (RSM) and quadratic programming (QP) was employed for maximizing Pb(II) removal from aqueous solution by Antep pistachio (Pistacia vera L.) shells based on 17 different experimental data obtained in a lab-scale batch study. Three independent variables (initial pH of solution (pH(0)) ranging from 2.0 to 5.5, initial concentration of Pb(II) ions (C(0)) ranging from 5 to 50 ppm, and contact time (t(C)) ranging from 5 to 120 min) were consecutively coded as x(1), x(2) and x(3) at three levels (-1, 0 and 1), and a second-order polynomial regression equation was then derived to predict responses. The significance of independent variables and their interactions were tested by means of the analysis of variance (ANOVA) with 95% confidence limits (alpha=0.05). The standardized effects of the independent variables and their interactions on the dependent variable were also investigated by preparing a Pareto chart. The optimum values of the selected variables were obtained by solving the quadratic regression model, as well as by analysing the response surface contour plots. The optimum coded values of three test variables were computed as x(1)=0.125, x(2)=0.707, and x(3)=0.107 by using a LOQO/AMPL optimization algorithm. The experimental conditions at this global point were determined to be pH(0)=3.97, C(0)=43.4 ppm, and t(C)=68.7 min, and the corresponding Pb(II) removal efficiency was found to be about 100%.

  19. Using Central Composite Experimental Design to Optimize the Degradation of Tylosin from Aqueous Solution by Photo-Fenton Reaction

    Directory of Open Access Journals (Sweden)

    Abd Elaziz Sarrai

    2016-05-01

    Full Text Available The feasibility of the application of the Photo-Fenton process in the treatment of aqueous solution contaminated by Tylosin antibiotic was evaluated. The Response Surface Methodology (RSM based on Central Composite Design (CCD was used to evaluate and optimize the effect of hydrogen peroxide, ferrous ion concentration and initial pH as independent variables on the total organic carbon (TOC removal as the response function. The interaction effects and optimal parameters were obtained by using MODDE software. The significance of the independent variables and their interactions was tested by means of analysis of variance (ANOVA with a 95% confidence level. Results show that the concentration of the ferrous ion and pH were the main parameters affecting TOC removal, while peroxide concentration had a slight effect on the reaction. The optimum operating conditions to achieve maximum TOC removal were determined. The model prediction for maximum TOC removal was compared to the experimental result at optimal operating conditions. A good agreement between the model prediction and experimental results confirms the soundness of the developed model.

  20. Multi-pathway excited state relaxation of adenine oligomers in aqueous solution: a joint theoretical and experimental study.

    Science.gov (United States)

    Banyasz, Akos; Gustavsson, Thomas; Onidas, Delphine; Changenet-Barret, Pascale; Markovitsi, Dimitra; Improta, Roberto

    2013-03-11

    The singlet excited states of adenine oligomers, model systems widely used for the understanding of the interaction of ultraviolet radiation with DNA, are investigated by fluorescence spectroscopy and time-dependent (TD) DFT calculations. Fluorescence decays, fluorescence anisotropy decays, and time-resolved fluorescence spectra are recorded from the femtosecond to the nanosecond timescales for single strand (dA)20 in aqueous solution. These experimental observations and, in particular, the comparison of the fluorescence behavior upon UVC and UVA excitation allow the identification of various types of electronic transitions with different energy and polarization. Calculations performed for up to five stacked 9-methyladenines, taking into account the solvent, show that different excited states are responsible for the absorption in the UVC and UVA spectral domains. Independently of the number of bases, bright excitons may evolve toward two types of excited dimers having π-π* or charge-transfer character, each one distinguished by its own geometry and spectroscopic signature. According to the picture arising from the joint experimental and theoretical investigation, UVC-induced fluorescence contains contribution from 1) exciton states with a different degree of localization, decaying within a few ps, 2) "neutral" excited dimers decaying on the sub-nanosecond timescale, being the dominant species, and 3) charge-transfer states decaying on the nanosecond timescale. The majority of the photons emitted upon UVA excitation are related to charge-transfer states.

  1. 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).

  2. Experimental and numerical study on effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer coefficient.

    Science.gov (United States)

    Rong, Li; Nielsen, Peter V; Zhang, Guoqiang

    2010-04-01

    This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 x 10(4) to 5.43 x 10(4) (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.

  3. [Experimental Research of Hg (II) Removal from Aqueous Solutions of HgCl2 with Nano-TiO2].

    Science.gov (United States)

    Zhou, Xiong; Zhang, Jin-yang; Wang, Ding-yong; Qin, Cai-qing; Xu, Feng; Luo Cheng-zhong; Yang, Xi

    2016-01-15

    Mercury removal from aqueous solutions of HgCl2 was studied by indoor simulation experiments, and the effects of three different diameter of particles of Nano-TiO2 ( Nano-Titanium Dioxide) at different dosage, pH, adsorption time and the initial concentration of Hg2+ on the mercury adsorption from simulated wastewater were investigated. The single factor experiments showed that the optimal conditions were: 7.5 g x L(-1) of 5 nm TiO2 or 2.0 g x L(-1) of 100 nm TiO2, pH 8.0, initial concentration of Hg2+ 15 x mg x L(-1) adsorption time 5 min, and under these conditions the adsorption rates reached 99.5% and 99.3%, relatively. When the content of 25 nm TiO2 was 10 g x L(-1), and the other conditions were pH 8.0, initial concentration of Hg2+ 15 mg x L(-1), adsorption time 60 min, the adsorption rate was 62.8%. The Hg(II) removal effects of the TiO2 particles with different diameters followed the order of 100 nm TiO2 > 5 nm TiO2 > 25 nm TiO2. Component adsorption results showed that the 5 nm TiO2 component adsorption effect was superior to its single adsorption effect, while there was little difference between 100 nm TiO2 component adsorption effect and its single adsorption effect. The results of orthogonal experiments indicated that the influencing factors of the adsorption rate followed the order of pH > the initial concentration of Hg2+ > time > dosage. The optimal experiment scheme was: pH 8.0, a dosage of 100 nm Nano-TiO2 of 2.0 g x L(-1) an initial Hg2+ concentration of 25 mg x L(-1) and adsorption time of 10 min. Under the experimental conditions, the maximum adsorption rate reached 99.9%, at the same time, the equilibrium concentration of Hg(II) was 0.033 mg x L(-1) adsorptive capacity was 26.95 mg x g(-1). The adsorption isotherm was in line with the Langmuir isotherm equation, indicating that the Hg(II) uptake by 100 nm Nano-TiO2 was typical monolayer adsorption.

  4. An experimental study of the solubility and speciation of niobium in fluoride-bearing aqueous solutions at elevated temperature

    Science.gov (United States)

    Timofeev, A.; Migdisov, Art. A.; Williams-Jones, A. E.

    2015-06-01

    The solubility of Nb2O5 and the speciation of niobium in HF-bearing aqueous solutions have been determined at temperatures of 150, 200, and 250 °C and saturated water pressure. At a pH of ∼2 and at low HF concentration, niobium is transported primarily as the species Nb(OH)4+ and at high HF concentration, as the species NbF2(OH)3°. Equilibrium constants for the formation of Nb(OH)4+ range from -11.23 ± 0.26 to -10.86 ± 0.24 and for the formation of NbF2(OH)3° from -3.84 ± 0.20 to -5.08 ± 0.42, at 150 and 250 °C. The results of this study show that the solubility of Nb2O5 (solid) in aqueous fluids increases with increasing HF concentration, but is not strongly affected by temperature. The influence of pH is variable; at low pH and HF concentration, a decrease in pH increases the solubility of Nb2O5 (solid). At higher pH, the reverse may be true. Modeling of the transport and deposition of niobium suggests that simple mixing with a brine is not an effective method for removing niobium from solution. By contrast, interaction of an acidic fluid with carbonate rock results in a rapid reduction in the capacity of the fluid to mobilize niobium.

  5. A Novel Experimental Technique to Monitor the Time-Dependent Water and Ions Uptake when Shale Interacts with Aqueous Solutions

    Science.gov (United States)

    AL-Bazali, Talal

    2013-09-01

    The time-dependent water and ions uptake when shale interacts with aqueous solutions is quantified using a combination of immersion and gravimetric techniques. Results show that when shale interacts with salt solutions, water uptake into shale goes through three distinct stages; water movement out of shale (due to chemical osmosis), water movement into shale (due to diffusion osmosis) and stationary state (equilibrium stage). This work shows that chemical osmosis dominates water movement in early times while diffusion osmosis takes over later. In addition, it is shown that the amount of water movement due to chemical osmosis depends on the chemical potential gradient while the amount of water movement due to diffusion osmosis is highly related to the ionic concentration imbalance. In addition, the amount of ions uptake into shale at equilibrium is shown to depend on the type and concentration of salt solution. Furthermore, this work shows that potassium ion has a strengthening effect on shale while sodium and calcium ions have a weakening effect on shale. Results also show that the shale's compressive strength alteration is greatly influenced by the type and concentration of the salt solution. Furthermore, the shale's compressive strength alteration is shown to be time dependent and correlates very well with the time-dependent flux of water and ions. Finally, it is shown that chemical osmosis and diffusion osmosis take place simultaneously when shale interacts with water-based muds. The overall impact on shale stability is governed by the net water flow resulting from chemical osmosis and diffusion osmosis.

  6. An experimental study of the solubility and speciation of tantalum in fluoride-bearing aqueous solutions at elevated temperature

    Science.gov (United States)

    Timofeev, A.; Migdisov, Art. A.; Williams-Jones, A. E.

    2017-01-01

    The solubility of Ta2O5 (solid) and the speciation of tantalum in HF-bearing aqueous solutions have been determined at temperatures of 100-250 °C and vapour-saturated water pressure. Tantalum is transported as the species Ta(OH)50 at low HF concentration and pH ∼1-3. At higher HF concentration, tantalum mobility is controlled by the species TaF3(OH)3- and TaF50; the presence of TaF50 is only evident at ⩽150 °C. Equilibrium constants range from -17.4 ± 0.45 to -16.4 ± 0.12 for the formation of Ta(OH)50 from crystalline Ta2O5 and from -8.24 ± 0.64 to -8.55 ± 0.68 for the formation of TaF3(OH)3- at 100 and 250 °C, respectively. For TaF50, they were determined to be 0.13 at 100 °C and -0.35 at 150 °C. In many respects, the behaviour of tantalum in acidic fluoride-bearing solutions is similar to that of niobium. The solubility of Ta2O5 (solid) is not dependent on HF concentration in fluoride-poor fluids, but rises rapidly at higher HF concentration. However, at the conditions of our experiments, namely a pH of ∼2, temperature up to 250 °C, and a wide range of HF concentrations, Ta2O5 (solid) solubility is almost invariably lower than that of Nb2O5 (solid). Modelling of Nb and Ta leaching confirmed the preferential mobility of niobium under most conditions expected in natural fluoride-rich hydrothermal systems. This modelling also demonstrated that both niobium and tantalum are rapidly deposited upon removal of fluoride from an acidic brine. As a result of hydrothermal alteration, the Nb/Ta ratios of secondary minerals may increase relative to those of the primary mineral, or remain largely unaffected, depending on the pH of the fluid.

  7. Experimental determination of water activity for binary aqueous cerium(III) ionic solutions: application to an assessment of the predictive capability of the binding mean spherical approximation model.

    Science.gov (United States)

    Ruas, Alexandre; Simonin, Jean-Pierre; Turq, Pierre; Moisy, Philippe

    2005-12-08

    This work is aimed at a description of the thermodynamic properties of actinide salt solutions at high concentration. The predictive capability of the binding mean spherical approximation (BIMSA) theory to describe the thermodynamic properties of electrolytes is assessed in the case of aqueous solutions of lanthanide(III) nitrate and chloride salts. Osmotic coefficients of cerium(III) nitrate and chloride were calculated from other lanthanide(III) salts properties. In parallel, concentrated binary solutions of cerium nitrate were prepared in order to measure experimentally its water activity and density as a function of concentration, at 25 degrees C. Water activities of several binary solutions of cerium chloride were also measured to check existing data on this salt. Then, the properties of cerium chloride and cerium nitrate solutions were compared within the BIMSA model. Osmotic coefficient values for promethium nitrate and promethium chloride given by this theory are proposed. Finally, water activity measurements were made to examine the fact that the ternary system Ce(NO3)3/HNO3/H2O and the quaternary system Ce(NO3)3/HNO3/N2H5NO3/H2O may be regarded as "simple solutions" (in the sense of Zdanovskii and Mikulin).

  8. Removal of cobalt ions from aqueous solutions by polymer assisted ultrafiltration using experimental design approach. part 1: optimization of complexation conditions.

    Science.gov (United States)

    Cojocaru, Corneliu; Zakrzewska-Trznadel, Grazyna; Jaworska, Agnieszka

    2009-09-30

    The polymer assisted ultrafiltration process combines the selectivity of the chelating agent with the filtration ability of the membrane acting in synergy. Such hybrid process (complexation-ultrafiltration) is influenced by several factors and therefore the application of experimental design for process optimization using a reduced number of experiments is of great importance. The present work deals with the investigation and optimization of cobalt ions removal from aqueous solutions by polymer enhanced ultrafiltration using experimental design and response surface methodological approach. Polyethyleneimine has been used as chelating agent for cobalt complexation and the ultrafiltration experiments were carried out in dead-end operating mode using a flat-sheet membrane made from regenerated cellulose. The aim of this part of experiments was to find optimal conditions for cobalt complexation, i.e. the influence of initial concentration of cobalt in feed solution, polymer/metal ratio and pH of feed solution, on the rejection efficiency and binding capacity of the polymer. In this respect, the central compositional design has been used for planning the experiments and for construction of second-order response surface models applicable for predictions. The analysis of variance has been employed for statistical validation of regression models. The optimum conditions for maximum rejection efficiency of 96.65% has been figured out experimentally by gradient method and was found to be as follows: [Co(2+)](0)=65 mg/L, polymer/metal ratio=5.88 and pH 6.84.

  9. Theoretical and experimental studies on freezing point depression and vapor pressure deficit as methods to measure osmotic pressure of aqueous polyethylene glycol and bovine serum albumin solutions.

    Science.gov (United States)

    Kiyosawa, Keitaro

    2003-05-01

    For survival in adverse environments where there is drought, high salt concentration or low temperature, some plants seem to be able to synthesize biochemical compounds, including proteins, in response to changes in water activity or osmotic pressure. Measurement of the water activity or osmotic pressure of simple aqueous solutions has been based on freezing point depression or vapor pressure deficit. Measurement of the osmotic pressure of plants under water stress has been mainly based on vapor pressure deficit. However, differences have been noted for osmotic pressure values of aqueous polyethylene glycol (PEG) solutions measured by freezing point depression and vapor pressure deficit. For this paper, the physicochemical basis of freezing point depression and vapor pressure deficit were first examined theoretically and then, the osmotic pressure of aqueous ethylene glycol and of PEG solutions were measured by both freezing point depression and vapor pressure deficit in comparison with other aqueous solutions such as NaCl, KCl, CaCl(2), glucose, sucrose, raffinose, and bovine serum albumin (BSA) solutions. The results showed that: (1) freezing point depression and vapor pressure deficit share theoretically the same physicochemical basis; (2) theoretically, they are proportional to the molal concentration of the aqueous solutions to be measured; (3) in practice, the osmotic pressure levels of aqueous NaCl, KCl, CaCl(2), glucose, sucrose, and raffinose solutions increase in proportion to their molal concentrations and there is little inconsistency between those measured by freezing point depression and vapor pressure deficit; (4) the osmotic pressure levels of aqueous ethylene glycol and PEG solutions measured by freezing point depression differed from the values measured by vapor pressure deficit; (5) the osmotic pressure of aqueous BSA solution measured by freezing point depression differed slightly from that measured by vapor pressure deficit.

  10. Phase equilibria of carbohydrates: the study of a series of glucose oligomers from glucose to maltopentaose in aqueous solution - Experimental versus predicted data using various UNIQUAC/UNIFAC models

    DEFF Research Database (Denmark)

    Cooke, S.A.; Jonsdottir, Svava Osk; Westh, Peter

    2002-01-01

    Vapour pressures above solutions of glucose (Glc) in water and maltose in water at both 298.06 and 317.99 K have been measured. Vapour pressures above aqueous solutions of maltotriose, maltotetraose and maltopentaose at 317.99 K have also been measured. The experimental results are compared with ...

  11. 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.

  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. 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.

  14. 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

  15. 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

  16. Adsorption of lead ions from aqueous solution using porous carbon derived from rubber tires: experimental and computational study.

    Science.gov (United States)

    Saleh, Tawfik A; Gupta, Vinod K; Al-Saadi, Abdulaziz A

    2013-04-15

    Effective activated porous carbon (AC) was prepared by thermal treatment of waste rubber tires and was further activated using oxidizing agents like nitric acid and hydrogen peroxide. The tire-derived porous carbon was characterized by means of FTIR and X-ray diffraction. Careful analysis of the IR spectra of the synthesized AC reveals a number of bands centered at about 3400, 2350, 1710, 1650, and 1300-1000cm(-1), proving the existence of hydroxyl and carboxylic groups on the surface of AC in addition to CC double bonds. The developed AC was tested and evaluated as a potential adsorbent for the removal of lead (II) ions. Experimental parameters, such as contact time, initial concentration, adsorbent dosage, and pH were optimized. AC was effective in a pH range between 4 and 7 with a highest uptake of lead ions at pH 5 and 6. For further understanding of the chemistry behind the process, density functional theory (DFT) calculations were performed at the B3LYP/6-31G(d) level adopting a functionalized pyrene molecule as a model. The binding energy of Pb(II) ion toward carboxylic acid, carbonyl, and hydroxyl groups was calculated. A binding energy in the range of 310-340kcal/mol, which is considered to be high and to be indicative of a chemisorptions process, was predicted. The adsorption of the lead ion toward the CO groups in relatively all cases shows more stable binding compared to the sorption toward the alcohol groups.

  17. Factorial experimental design for the optimization of catalytic degradation of malachite green dye in aqueous solution by Fenton process

    Directory of Open Access Journals (Sweden)

    A. Elhalil

    2016-09-01

    Full Text Available This work focuses on the optimization of the catalytic degradation of malachite green dye (MG by Fenton process “Fe2+/H2O2”. A 24 full factorial experimental design was used to evaluate the effects of four factors considered in the optimization of the oxidative process: concentration of MG (X1, concentration of Fe2+ (X2, concentration of H2O2 (X3 and temperature (X4. Individual and interaction effects of the factors that influenced the percentage of dye degradation were tested. The effect of interactions between the four parameters shows that there is a dependency between concentration of MG and concentration of Fe2+; concentration of Fe2+ and concentration of H2O2, expressed by the great values of the coefficient of interaction. The analysis of variance proved that, the concentration of MG, the concentration of Fe2+ and the concentration of H2O2 have an influence on the catalytic degradation while it is not the case for the temperature. In the optimization, the great dependence between observed and predicted degradation efficiency, the correlation coefficient for the model (R2=0.986 and the important value of F-ratio proved the validity of the model. The optimum degradation efficiency of malachite green was 93.83%, when the operational parameters were malachite green concentration of 10 mg/L, Fe2+ concentration of 10 mM, H2O2 concentration of 25.6 mM and temperature of 40 °C.

  18. 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)

  19. 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

  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. 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.

  2. 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

  3. 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.

  4. 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.

  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. 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.

  7. Experimental study of evaporation of distilled water and 10% NaCl and СaCl2 aqueous salt solutions droplets under their free falling on a heated surface

    Directory of Open Access Journals (Sweden)

    Feoktistov D.V.

    2017-01-01

    Full Text Available The paper presents the experimental results of evaporation of distilled water and 10% aqueous salt solutions of NaCl and СaCl2 droplets under their free falling on a heated surface. It is proved that it is more expedient to conduct the experimental research in this field according to classical multifactorial experiment. Laser treatment of surfaces is found to increase the evaporation rate and to biases the point of boiling crisis in the region of lower surface temperatures. In this case, in the conditions of boiling crisis the frequency of contact of a droplet with a heated surface will decrease.

  8. 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.

  9. 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.

  10. Experimental determination of the isothermal (vapour + liquid) equilibria of binary aqueous solutions of sec-butylamine and cyclohexylamine at several temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Chiali-Baba Ahmed, Nouria [LATA2M, Laboratoire de Thermodynamique Appliquee et Modelisation Moleculaire, University AbouBekr Belkaid of Tlemcen, Post Office Box 119, Tlemcen 13000 (Algeria); Negadi, Latifa, E-mail: latifanegadi@yahoo.fr [LATA2M, Laboratoire de Thermodynamique Appliquee et Modelisation Moleculaire, University AbouBekr Belkaid of Tlemcen, Post Office Box 119, Tlemcen 13000 (Algeria); Mokbel, Ilham [LSA, Laboratoire des Sciences Analytiques, CNRS-UMR 5280, Universite Claude Bernard - Lyon I, 43, Bd du 11 Novembre 1918, Villeurbanne Cedex 69622 (France); Kaci, Ahmed Ait [Laboratoire de Thermodynamique et Modelisation Moleculaire, Universite des Sciences et de la Technologie Houari Boumediene, Post Office Box 32, El Alia 16111, Bab Ezzouar (Algeria); Jose, Jacques [LSA, Laboratoire des Sciences Analytiques, CNRS-UMR 5280, Universite Claude Bernard - Lyon I, 43, Bd du 11 Novembre 1918, Villeurbanne Cedex 69622 (France)

    2012-01-15

    Highlights: > Vapour pressures of sec-butylamine or cyclohexylamine and their aqueous solutions. > The investigated temperatures are 273 K and 363 K. > The (cyclohexylamine + water) mixture shows positive azeotropic behaviour. > The (sec-butylamine + water) or (cyclohexylamine + water) exhibit positive G{sup E}. - Abstract: The vapour pressures of (sec-butylamine + water), (cyclohexylamine + water) binary mixtures, and of pure sec-butylamine and cyclohexylamine components were measured by means of two static devices at temperatures between 293 (or 273) K and 363 K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (G{sup E}) were calculated for several constant temperatures and fitted to a fourth-order Redlich-Kister equation using the Barker's method. The (cyclohexylamine + water) system shows positive azeotropic behaviour for all investigated temperatures. The two binary mixtures exhibit positive deviations in G{sup E} for all investigated temperatures over the whole composition range.

  11. 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.

  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. 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.

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

    Science.gov (United States)

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

    2011-01-30

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

  15. Removal of arsenic from aqueous solution using electrocoagulation.

    Science.gov (United States)

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

    2009-08-15

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

  16. Conformational flexibility around the Gal-β-(1 → 3)-Glc linkage: Experimental evidence for the existence of the anti-ψ conformation in aqueous solution.

    Science.gov (United States)

    Vidal, Paloma; Jiménez-Barbero, Jesús; Espinosa, Juan F

    2016-10-04

    NOE-based analysis of the disaccharide β-Gal-(1 → 3)-β-Glc-OMe (1), especially a diagnostic Gal1-Glc4 NOE detected in a HSQC-NOESY spectrum, reveals the existence of the anti-ψ conformer in aqueous solution in addition to the major syn conformer. This result provides experimental proof of conformational flexibility around the aglyconic bond of β-(1 → 3) disaccharides, in contrast to previous studies that suggested that the flexibility around this linkage was restricted to the syn conformational region.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. "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.

  10. 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

  11. 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 %.

  12. 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

  13. 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

  14. Aqueous humor changes after experimental filtering surgery.

    Science.gov (United States)

    Radius, R L; Herschler, J; Claflin, A; Fiorentino, G

    1980-02-01

    We studied aqueous humor of rhesus and owl monkeys for its effect on the growth of subconjunctival fibroblasts in tissue culture. Aqueous humor samples obtained before glaucoma surgery inhibited the initiation of growth of fibroblasts. However, postoperative aqueous humor samples supported growth of fibroblasts. The change in aqueous humor physiology lasted for up to two months after glaucoma surgery. Our study indicated that possibly material added to the postoperative aqueous humor inactivates an inhibitor normally present in primary aqueous humor. An alternative explanation would be that primary aqueous humor, in contrast to secondary aqueous humor, lacks sufficient nutrient material to support fibroblast growth in tissue culture.

  15. 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.

  16. 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.

  17. 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...

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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....

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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...

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Experimental Research on Effects of Nozzle Geometrical Structure on Liquid-Vapor Ejector using Aqueous LiBr Solution as Primary Fluid

    Directory of Open Access Journals (Sweden)

    Hongtao Gao

    2012-08-01

    Full Text Available From the standpoint of offering reference for its optimal design, liquid-gas ejector is applied to lithium bromide absorption refrigerator in order to improve mass transfer efficiency. Many nozzles with different geometrical structures are adopted and experimental research is conducted to investigate the influence of physical dimension on performance of ejector. By comparison between convergent-divergent nozzle and convergent nozzle, the results show that, the reason for the influence on cooling capacity is different. With convergent-divergent nozzle, the cooling capacity increases with the decrease of throat diameter. With convergent nozzle, the tendency is on the contrary. With the same minimum cross area, the cooling capacity with convergent-divergent nozzle is better than that with convergent nozzle.

  17. 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.

  18. 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.

  19. 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.

  20. Quantifying the binding strength of salicylaldoxime-uranyl complexes relative to competing salicylaldoxime-transition metal ion complexes in aqueous solution: a combined experimental and computational study.

    Science.gov (United States)

    Mehio, Nada; Ivanov, Alexander S; Williams, Neil J; Mayes, Richard T; Bryantsev, Vyacheslav S; Hancock, Robert D; Dai, Sheng

    2016-05-31

    The design of new ligands and investigation of UO2(2+) complexations are an essential aspect of reducing the cost of extracting uranium from seawater, improving the sorption efficiency for uranium and the selectivity for uranium over competing ions (such as the transition metal cations). The binding strengths of salicylaldoxime-UO2(2+) complexes were quantified for the first time and compared with the binding strengths of salicylic acid-UO2(2+) and representative amidoxime-UO2(2+) complexes. We found that the binding strengths of salicylaldoxime-UO2(2+) complexes are ∼2-4 log β2 units greater in magnitude than their corresponding salicylic acid-UO2(2+) and representative amidoxime-UO2(2+) complexes; moreover, the selectivity of salicylaldoxime towards the UO2(2+) cation over competing Cu(2+) and Fe(3+) cations is far greater than those reported for salicylic acid and glutarimidedioxime in the literature. The higher UO2(2+) selectivity can likely be attributed to the different coordination modes observed for salicylaldoxime-UO2(2+) and salicylaldoxime-transition metal complexes. Density functional theory calculations indicate that salicylaldoxime can coordinate with UO2(2+) as a dianion species formed by η(2) coordination of the aldoximate and monodentate binding of the phenolate group. In contrast, salicylaldoxime coordinates with transition metal cations as a monoanion species via a chelate formed between phenolate and the oxime N; the complexes are stabilized via hydrogen bonding interactions between the oxime OH group and phenolate. By coupling the experimentally determined thermodynamic constants and the results of theoretical computations, we are able to derive a number of ligand design principles to further improve the UO2(2+) cation affinity, and thus further increase the selectivity of salicylaldoxime derivatives.

  1. 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.

  2. 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.

  3. 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.

  4. 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…

  5. 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.

  6. 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.

  7. 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.

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

    OpenAIRE

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

    2009-01-01

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

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

    Science.gov (United States)

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

    2016-11-01

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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  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. 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.

  16. 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....

  17. 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...

  18. 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

  19. 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.

  20. [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.

  1. Solubility of N2O in and density, viscosity, and surface tension of aqueous piperazine solutions

    NARCIS (Netherlands)

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

    2005-01-01

    The physical solubility of N2O in and the density and viscosity of aqueous piperazine solutions have been measured over a temperature range of (293.15 to 323.15) K for piperazine concentrations ranging from about (0.6 to 1.8) kmol·mr-3. Furthermore, the present study contains experimental surface t

  2. A Review on Chemical Effects in Aqueous Solution induced by Plasma with Glow Discharge

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Chemical effects in different aqueous solutions induced by plasma with glow dis charge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..

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

    NARCIS (Netherlands)

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

    2009-01-01

    In this work, 72 new experimental solubility data points for H(2)S and CO(2) mixtures in aqueous N-methyldiethanol amine (MDEA) solutions at different methane partial pressures (up to 69 bara) are presented. They are correlated using an electrolyte equation of state (E-EOS) thermodynamic model. This

  4. Preparation of Ultrafine Cobalt Powder by Chemical Reduction in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Nanocrystalline cobalt powders have been prepared from aqueous solution by reducing their corresponding metal salts under suitable conditions. The experimental conditions have been studied in detail. X-ray powder diffraction patterns show that the cobalt powder is hexagonal crystallite. The average particle size of the ultrafine cobalt powder is 55 nm.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  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. 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.

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

    Science.gov (United States)

    Okada, Masashi; Kang, Chaedong; Okiyama, Haruhiko

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

  15. Radiolysis of paracetamol in dilute aqueous solution

    Science.gov (United States)

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

    2012-09-01

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

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

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

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

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

    NARCIS (Netherlands)

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

    2006-01-01

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

  18. 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.

  19. 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...

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.)

  18. 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.

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

    Science.gov (United States)

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

    2013-02-01

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

  20. 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.

  1. 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.

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

    Science.gov (United States)

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

    2008-08-28

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

  3. 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.

  4. Carbon dioxide solubility in aqueous solutions of sodium chloride at geological conditions: Experimental results at 323.15, 373.15, and 423.15 K and 150 bar and modeling up to 573.15 K and 2000 bar

    Science.gov (United States)

    Zhao, Haining; Fedkin, Mark V.; Dilmore, Robert M.; Lvov, Serguei N.

    2015-01-01

    A new experimental system was designed to measure the solubility of CO2 at pressures and temperatures (150 bar, 323.15-423.15 K) relevant to geologic CO2 sequestration. At 150 bar, new CO2 solubility data in the aqueous phase were obtained at 323.15, 373.15, and 423.15 K from 0 to 6 mol kg-1 NaCl(aq) for the CO2-NaCl-H2O system. A γ - φ (activity coefficient - fugacity coefficient) type thermodynamic model is presented for the calculation of both the solubility of CO2 in the aqueous phase and the solubility of H2O in the CO2-rich phase for the CO2-NaCl-H2O system. Validation of the model calculations against literature data and other models (MZLL2013, AD2010, SP2010, DS2006, and OLI) show that the proposed model is capable of predicting the solubility of CO2 in the aqueous phase for the CO2-H2O and CO2-NaCl-H2O systems with a high degree of accuracy (AAD @gmail.com.

  5. 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.

  6. 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.

  7. Modeling and measurements of solid-liquid and vapor-liquid equilibria of polyols and carbohydrates in aqueous solution

    DEFF Research Database (Denmark)

    Jonsdottir, Svava Osk; Cooke, S.A.; Macedo, E.A.

    2002-01-01

    calculated with molecular mechanics methods has shown to give good predictions of the phase behavior of a variety of mixtures, including glycols and small saccharides in aqueous solution. The method is completely predictive, as the strength of the molecular interactions is determined with a theoretical...... and saccharides in aqueous solution have been predicted with this method, giving results in excellent agreement with the experimental values....

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

    Directory of Open Access Journals (Sweden)

    Mohsen Hosseinzadeh

    2016-12-01

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

  9. 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.

  10. 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....

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. 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.

  18. 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.

  19. 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).

  20. 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...

  1. 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...

  2. 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 ...

  3. The solubility of hydrogen sulfide in aqueous N-methyldiethanolamine solutions

    OpenAIRE

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

    2008-01-01

    In this work the electrolyte equation of state as developed previously for the system MDEA-H2O-CO2-CH4 was further developed for the system MDEA-H2O-H2S-CH4. With this thermodynamic equilibrium model the total solubility of hydrogen sulfide and the speciation in aqueous solutions of N-methyldiethanolamine can be described quantitatively. The model results were compared to experimental H2S solubility data in aqueous MDEA in absence and presence of methane respectively. The application of equat...

  4. 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.

  5. Enthalpy of solution of CO{sub 2} in aqueous solutions of methyldiethanolamine at T = 372.9 K and pressures up to 5 MPa

    Energy Technology Data Exchange (ETDEWEB)

    Arcis, Hugues; Rodier, Laurence; Ballerat-Busserolles, Karine [Laboratoire de Thermodynamique et des Interactions Moleculaire, FRE 3099 Universite Blaise, Pascal Clermont-Ferrand/CNRS, 63177 Aubiere (France); Coxam, Jean-Yves [Laboratoire de Thermodynamique et des Interactions Moleculaire, FRE 3099 Universite Blaise, Pascal Clermont-Ferrand/CNRS, 63177 Aubiere (France)], E-mail: j-yves.coxam@univ-bpclermont.fr

    2009-07-15

    Experimental enthalpies of solution of CO{sub 2} in aqueous solution of methyldiethanolamine (MDEA) of 15 wt% and 30 wt% are reported. The measurements were performed using a flow calorimetric technique at temperature of 372.9 K and pressures range from 0.5 MPa to 5 MPa. Gas solubilities data at same temperature and pressures were derived from the enthalpy data. Experimental enthalpies of solution are combined with available literature data in order to examine pressure and composition influences.

  6. 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.

  7. Modeling of Pervaporation Separation Benzene from Dilute Aqueous Solutions Through Polydimethylsiloxane Membranes

    Institute of Scientific and Technical Information of China (English)

    彭福兵; 姜忠义

    2005-01-01

    A modified solution-diffusion model was established based on Flory-Huggins thermodynamic theory and Fujita's free volume theory. This model was used for description of the mass transfer of removal benzene from dilute aqueous solutions through polydimethylsiloxane (PDMS) membranes. The effect of component concentration on the interaction parameter between components, that of the polymer membrane on the selectivity to benzene, and that of feed concentration and temperature on the permeation flux and separation factor of benzene/water through PDMS membranes were investigated. Calculated pervaporation fluxes of benzene and water were compared with the experimental results and were in good agreement with the experimental data.

  8. Poisson-Fermi model of single ion activities in aqueous solutions

    Science.gov (United States)

    Liu, Jinn-Liang; Eisenberg, Bob

    2015-09-01

    A Poisson-Fermi model is proposed for calculating activity coefficients of single ions in strong electrolyte solutions based on the experimental Born radii and hydration shells of ions in aqueous solutions. The steric effect of water molecules and interstitial voids in the first and second hydration shells play an important role in our model. The screening and polarization effects of water are also included in the model that can thus describe spatial variations of dielectric permittivity, water density, void volume, and ionic concentration. The activity coefficients obtained by the Poisson-Fermi model with only one adjustable parameter are shown to agree with experimental data, which vary nonmonotonically with salt concentrations.

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. The Experimental Research of Emulsified Diesel with Glucose Aqueous Solution on Diesel Engine%葡萄糖水溶液乳化柴油在发动机上的试验研究

    Institute of Scientific and Technical Information of China (English)

    肖明伟; 蒋盛军; 陈振斌; 何金戈

    2013-01-01

    The emulsified diesel fuel with glucose aqueous solution was prepared through compound-surfactants and the specific emulsification technology.The experiments of the fuel economy performances and emission characteristics were performed on a 135 diesel engine fueled with different fuels.The results indicate that:compared with diesel fuel,the emulsified diesel fuel with glucose aqueous solution can reduce the equivalent brake specific fuel consumption and smoke without modification in the engine structure.NOx emissions are reduced obviously except at high load condition,CO emissions are reduced when the diesel engine work on high load condition,but HC emissions are increased at all load condition.The fuel economy performances and emission characteristics can be improved especially when the emulsified diesel fuel with glucose aqueous solution blended with accelerant ferrocene.%使用复配乳化剂通过适当的乳化工艺制备了不同配方的葡萄糖水溶液乳化柴油,并与纯柴油在135柴油机上做了一系列对比试验,研究了发动机燃用不同燃料的燃油经济性和排放特性.试验结果表明:在柴油机参数不作改变的情况下,燃用葡萄糖水溶液乳化柴油可降低发动机的当量燃油消耗率和碳烟排放,在中低负荷时NOx排放量也显著降低,大负荷时CO排放量略有减少,但HC排放在所有负荷工况下都增加;添加助燃剂二茂铁后可进一步改善发动机的燃油经济性和排放特性.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Water activity of aqueous solutions of ethylene oxide-propylene oxide block copolymers and maltodextrins

    Directory of Open Access Journals (Sweden)

    N. D. D. Carareto

    2010-03-01

    Full Text Available The water activity of aqueous solutions of EO-PO block copolymers of six different molar masses and EO/PO ratios and of maltodextrins of three different molar masses was determined at 298.15 K. The results showed that these aqueous solutions present a negative deviation from Raoult's law. The Flory-Huggins and UNIFAC excess Gibbs energy models were employed to model the experimental data. While a good agreement was obtained with the Flory-Huggins equation, discrepancies were observed when predicting the experimental behavior with the UNIFAC model. The water activities of ternary systems formed by a synthetic polymer, maltodextrin and water were also measured and used to test the predictive capability of both models.

  1. Thermodynamic modeling of acidic gas solubility in aqueous solutions of MEA, MDEA and MEA-MDEA blends

    DEFF Research Database (Denmark)

    Vrachnos, Ath.; Kontogeorgis, Georgios; Voutsas, EC

    2006-01-01

    The thermodynamic framework that was developed in a previous work [Vrachnos et al. Ind. Eng. Chem. Res. 2004, 43, 2798] for the description of chemical and vapor-liquid equilibria of carbon dioxide, hydrogen sulfide, and their mixtures in aqueous methyldiethanolamine (MDEA) solutions is revised...... and extended in this study to the absorption of carbon dioxide into aqueous monoethanolamine (MEA) solutions and aqueous MDEA-MEA blends. The results of the model are compared with experimental data taken from the literature. Very satisfactory predictions of acidic gas vapor-liquid equilibrium over MDEA, MEA...

  2. Simulations of mean ionic activity coefficients and solubilities in aqueous electrolyte solutions

    Science.gov (United States)

    Panagiotopoulos, Athanassios

    Aqueous electrolyte solutions play an important role in industrial, geochemical and biological applications. The mean ionic activity coefficients quantify the deviation of salt chemical potential from ideal solution behavior; experimental measurements are available for many salts over broad ranges of concentration and temperature, but there have been practically no prior simulation results, because if sampling difficulties for explicit-solvent electrolyte solutions. We have developed a new approach for determination of activity coefficients of aqueous electrolytes. Common fixed-point-charge models for water and ions are unable to reproduce simultaneously activity coefficients and solubilities. Polarizable models perform better, but still predict an incorrect temperature dependence of these properties. Work supported by the U.S. Department of Energy, Office of Basic Energy Science.

  3. Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Minbiao; /SLAC, PULSE /Stanford U., Phys. Dept.; Odelius3, Michael; /Stockholm U.; Gaffney1, K.J.; /aff SLAC, PULSE

    2010-06-11

    The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO{sub 4} solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extract an average jump angle of 49 {+-} 4{sup o}, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO{sub 4} solution.

  4. Thermodynamic Modeling of Surface Tension of Aqueous Electrolyte Solution by Competitive Adsorption Model

    Directory of Open Access Journals (Sweden)

    Mohamad Javad Kamali

    2015-01-01

    Full Text Available Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively.

  5. Removal of lead from aqueous solution using waste tire rubber ash as an adsorbent

    OpenAIRE

    Mousavi,H. Z.; Hosseynifar,A.; Jahed,V.; S. A. M. Dehghani

    2010-01-01

    The purpose of this study was to investigate the possibility of the utilization of waste tire rubber ash (WTRA) as a low cost adsorbent for removal of lead (II) ion from aqueous solution. The effect of different parameters (such as contact time, sorbate concentration, adsorbent dosage, pH of the medium and temperature) were investigated. The sorption process was relatively fast and equilibrium was reached after about 90 min of contact. The experimental data were analyzed by the Freundlich iso...

  6. Removal Of Copper From Aqueous Solutions By Using Natural And Fe-Modified Clinoptilolite

    Science.gov (United States)

    Lipovský, Marek; Sirotiak, Maroš; Soldán, Maroš

    2015-06-01

    Removal of copper from aqueous solution on the natural and modified clinoptilolite was studied under static conditions. Batch adsorptions of copper were performed to investigate the effects of contact time and initial metal ion concentration. The Freundlich and Langmuir adsorption isotherms were used to analyse the experimental data. The kinetic analyses of the adsorption processes were performed using the pseudo-first-order and pseudo-second-order kinetic models.

  7. Removal Of Copper From Aqueous Solutions By Using Natural And Fe-Modified Clinoptilolite

    Directory of Open Access Journals (Sweden)

    Lipovský Marek

    2015-06-01

    Full Text Available Removal of copper from aqueous solution on the natural and modified clinoptilolite was studied under static conditions. Batch adsorptions of copper were performed to investigate the effects of contact time and initial metal ion concentration. The Freundlich and Langmuir adsorption isotherms were used to analyse the experimental data. The kinetic analyses of the adsorption processes were performed using the pseudo-first-order and pseudo-second-order kinetic models.

  8. 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.

  9. 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.

  10. 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.

  11. Assessing 16-Year-Old Students' Understanding of Aqueous Solution at Submicroscopic Level

    Science.gov (United States)

    Devetak, Iztok; Vogrinc, Janez; Glažar, Saša Aleksij

    2009-03-01

    Submicrorepresentations (SMR) could be an important element, not only for explaining the experimental observations to students, but also in the process of evaluating students’ knowledge and identifying their chemical misconceptions. This study investigated the level of students’ understanding of the solution concentration and the process of dissolving ionic and molecular crystals at particulate level, and identifies possible misconceptions about this process. Altogether 408 secondary school students (average age 16.3) participated in the study. The test of chemical knowledge was applied and the analysis of four selected problems related to drawing SMRs in solution chemistry is presented. Selected students were also interviewed in order to gain more detailed data about their way of solving problems comprised in the knowledge test. The average achievement on solution chemistry items was only 43%. It can be concluded from the results that students have different misconceptions about arrangements of solute particles in the solution and presentation of its concentration at particulate level. Students show quite low achievement scores on the problem regarding drawing the SMR of ionic substance aqueous solution (7.6% correct answers) and even lower ones on the problem regarding drawing the SMR of diluted and saturated aqueous solutions of molecular crystal (no completely correct answers). It can be also concluded that many different misconceptions concerning the particulate level of basic solution chemistry concepts can be identified. In the conclusion some implications for teaching to reach a higher level of understanding of solution chemistry are proposed.

  12. Thermodynamic and transport properties of some biologically active compounds in aqueous solutions at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Dhondge, Sudhakar S., E-mail: s_dhondge@hotmail.co [P.G. Department of Chemistry, S.K. Porwal College, Kamptee, Nagpur 441 002 (India); Zodape, Sangesh P.; Parwate, Dilip V. [Department of Chemistry, R.T.M. Nagpur University, Nagpur 440 033 (India)

    2011-01-15

    The experimental data of density and viscosity have been obtained for aqueous solutions of biologically active compounds like salbutamol sulphate (SS), diethylcarbamazine citrate (DEC), and chlorpheniramine maleate (CPM) in the concentration range (0 to 0.15) mol . kg{sup -1} at three different temperatures. The derived parameters, such as apparent molar volume of solute ({phi}{sub V})), limiting apparent molar volume of solute ({phi}{sub V}{sup 0}), limiting apparent molar expansivity ({phi}{sub E}{sup 0}), thermal expansion coefficient ({alpha}*) and Jones-Dole equation viscosity A and B coefficients, were obtained using the density and viscosity results. It has been observed that the electrolyte-salt (SS) as well as adducts exhibit a positive viscosity B coefficient having negative ((dB)/(dT)). These results are interpreted in the light of possible solute-solute and solute-solvent interactions.

  13. Adsorption of organic acids from dilute aqueous solution onto activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.W.

    1980-06-01

    The radioisotope technique was used to study the removal of organic acid contaminants from dilute aqueous solutions onto activated carbon. Acetic acid, propionic acid, n-butyric acid, n-hexanoic acid and n-heptanoic acid were studied at 278, 298, and 313/sup 0/K. Three bi-solute acid mixtures (acetic and propionic acids, acetic and butanoic acids, and propionic and butanoic acids) were studied at 278 and 298/sup 0/K. Isotherms of the single-solute systems were obtained at three different temperatures in the very dilute concentration region (less than 1% by weight). These data are very important in the prediction of bi-solute equilibrium data. A Polanyi-based competitive adsorption potential theory was used to predict the bi-solute equilibrium uptakes. Average errors between calculated and experimental data ranges from 4% to 14%. It was found that the competitive adsorption potential theory gives slightly better results than the ideal adsorbed solution theory.

  14. 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.

  15. 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.

  16. 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.

  17. Design of Uranium Solution Critical Experimental Device

    Institute of Scientific and Technical Information of China (English)

    YI; Da-yong; GUO; Zhi-jia; YAO; Cheng-zhi; SHI; Chen-lei

    2012-01-01

    <正>In 2012, Department of reactor engineering design completes the design and mechanical analysis of Uranium solution critical experimental device. According to user’s requirements and nuclear safety regulations, design and analysis mainly involves two sets of core structure, uranium solution loop, water loop and experimental bench, etc. The core which includes a core vessel, reactor core support, safety rods, control rods, and so on, is used for containing uranium solution and fuel element and fulfilling the

  18. 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.

  19. 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.

  20. 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

  1. 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-].

  2. Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

    Science.gov (United States)

    Wang, Le; Mu, Wen-ning; Shen, Hong-tao; Liu, Shao-ming; Zhai, Yu-chun

    2015-05-01

    A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaCl2 aqueous solution, liquid-to-solid (L/S) ratio, leaching temperature, and leaching time, were investigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaCl2 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7:1, a leaching temperature of 80°C, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

  3. 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.

  4. 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....

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Slowdown of water diffusion around protein in aqueous solution with ectoine

    Science.gov (United States)

    Yu, I.; Nagaoka, M.

    2004-04-01

    Ectoine is one of the most common compatible solutes found in halophilic bacteria, and has an effect to introduce a tolerance to high salt concentration or high temperature. By analyzing 1 ns molecular dynamics simulations at 370 K, we have shown that, in the ectoine aqueous solution, the water diffusion slows down around a protein (chymotrypsin inhibitor 2 (CI2)), keeping the protein hydration structure essentially unchanged. It is concluded that the slowdown of water diffusion around the backbone amide protons must be one of the decisive factors in reducing the exchange rate of the backbone amide protons, whose reduction is experimentally believed closely related to the tolerance effect.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. The removal of lead ions using zeolite nanoparticles from aqueous solutions

    Science.gov (United States)

    Joshi, Parth

    2016-05-01

    The experiment for adsorption of lead ions from its aqueous solutions were carried out at room temperature and initial concentration of lead ions as well as after adsorption were determined by UV-Visible spectrophotometer. The effect of various parameters such as contact time, zeolite nanoparticles dosage and initial concentration of lead ions on the adsorption capacity of zeolite nanoparticles were studied in batch experiment. The kinetics of the adsorption processes was studied by using pseudo-first order and pseudo-second order. The pseudo-second order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first order. The maximum lead ions adsorbed was found to be 43.91 mg/g. The present study indicated that zeolite nanoparticles could be used as an efficient adsorbent for removal of lead ions from aqueous solution.

  19. MATHEMATICAL MODELLING OF CaCl2 AQUEOUS SOLUTIONS THERMOPHYSICAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    CRISTINA G. GRIGORAŞ, GABRIELA MUNTIANU, LUCIAN GAVRILĂ *

    2016-12-01

    Full Text Available Calcium chloride is an inorganic salt used in its solid state or as aqueous solutions in a multitude of research and industrial areas going from chemical industry to food, cosmetics or drugs production. This paper was directed to establish mathematical models relating its density and dynamic viscosity with factors such as temperature and concentration since it is known that these properties present a high influence on appropriate transport pipes dimensions and industrial equipment choosing and / or designing processes. The assessment and selection of the adequate models were realized by testing various software’s and equations. The obtained results revealed that calcium chloride aqueous solutions studied thermodynamic properties can accurately be expressed by quadratic (density and respectively by linear equations (dynamic viscosity or by more complex equations. Correlation coefficient, relative error and ANOVA values revealed no significant differences between experimental and calculated data.

  20. Removal of lead from aqueous solution using waste tire rubber ash as an adsorbent

    Directory of Open Access Journals (Sweden)

    H. Z. Mousavi

    2010-03-01

    Full Text Available The purpose of this study was to investigate the possibility of the utilization of waste tire rubber ash (WTRA as a low cost adsorbent for removal of lead (II ion from aqueous solution. The effect of different parameters (such as contact time, sorbate concentration, adsorbent dosage, pH of the medium and temperature were investigated. The sorption process was relatively fast and equilibrium was reached after about 90 min of contact. The experimental data were analyzed by the Freundlich isotherm and the Langmuir isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 22.35 mg/g. The adsorption kinetics was investigated and the best fit was achieved by a first-order equation. The results of the removal process show that the Pb (II ion adsorption on WTRA is an endothermic and spontaneous process. The procedure developed was successfully applied for the removal of lead ions in aqueous solutions.

  1. 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.

  2. Heat of Absorption of CO2 in Aqueous Solutions of DEEA, MAPA and their Mixture

    DEFF Research Database (Denmark)

    Waseem Arshad, Muhammad; von Solms, Nicolas; Thomsen, Kaj

    2013-01-01

    A reaction calorimeter was used to measure the differential heat of absorption of CO2 in phase change solvents as a function of temperature, CO2 loading and solvent composition. The measurements were taken for aqueous solutions of 2-(diethylamino)ethanol (DEEA), 3-(methylamino)propylamine (MAPA......) and their mixture. The tested compositions were 5M DEEA, 2M MAPA and their mixture, 5M DEEA + 2M MAPA which gives two liquid phases on reacting with CO2. Experimental measurements were also carried out for 30% MEA used as a base case. The measurements were taken isothermally at three different temperatures 40, 80...... and 120°C at a CO2 feed pressure of 600kPa. In single aqueous amine solutions, heat of absorption increases with increase in temperature and depends on thetype of amine used. DEEA, a tertiary amine, has lower heat of absorption compared to MAPA being a diamine with primary and secondary amine functional...

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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....

  9. 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.

  10. 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.

  11. Aggregation kinetics of graphene oxides in aqueous solutions: experiments, mechanisms, and modeling.

    Science.gov (United States)

    Wu, Lei; Liu, Lin; Gao, Bin; Muñoz-Carpena, Rafael; Zhang, Ming; Chen, Hao; Zhou, Zuhao; Wang, Hao

    2013-12-10

    Although graphene oxide (GO) has been used in many applications to improve human life quality, its environmental fate and behavior are still largely unknown. In this work, a novel approach that combines experimental measurements and theoretical calculations was used to determine the aggregation kinetics of GO sheets in aqueous solutions under different chemistry conditions (e.g., cation valence and pH). Experimental data showed that both cation valence and pH showed significant effect on the aggregation of GO sheets. The measured critical coagulation concentrations were in good agreement with the predictions of the extended Schulze-Hardy rule. Ca(2+) and Mg(2+) were more effective than Na(+) in aggregating the GO sheets, which could be attributed to the cross-linking between GO sheets by the divalent cations through "bridging" the functional groups at the edges of the GO sheets. When solution pH increases, deprotonation of carboxylic groups was found to play a key role in increasing GO sheet stability and surface charge development. These results suggested that edge-to-edge and face-to-face interactions were the dominant modes of GO aggregation in the presence of divalent metal ions and H(+), respectively. A modified attachment efficiency (α) model was developed on the basis of the Maxwell approach with considerations of both primary and secondary minima. The model predictions matched the experimental measurements of the aggregation kinetics of GO sheets in aqueous solutions under all of the tested experimental conditions well.

  12. 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.

  13. 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.

  14. 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.

  15. Removal of Copper (II Ions from Aqueous Solutions by Adsorption with Low Cost Acid Activated Cynodon Dactylon Carbon

    Directory of Open Access Journals (Sweden)

    U. Gayathri

    2011-01-01

    Full Text Available The main purpose of this work was to exploit low cost and efficient sorbents for the removal of copper from aqueous solution using Cynodon dactylon carbon. It was observed from the experimental results that almost 90-100% copper can be removed from the aqueous solution. Adsorption kinetics and equilibrium have been investigated as a function of initial copper ion concentration. pH, contact time and adsorbent dosage. Kinetics studies suggested that the adsorption allowed first order reaction. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models. On the basis of experimental results and the model parameters, it can be concluded that the carbonaceous Cynodon dactylon is effective for the removal of copper ion from aqueous solution.

  16. 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.

  17. Solubility of carbon dioxide and hydrogen sulfide in aqueous N-methyldiethanolamine solutions

    Energy Technology Data Exchange (ETDEWEB)

    Huttenhuis, P.J.G.; Agrawal, N.J.; Versteeg, G.F. [Procede Group BV, Enschede (Netherlands)

    2009-04-15

    In this work, 72 new experimental solubility data points for H{sub 2}S and CO{sub 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{sub 2} solubility in aqueous MDEA (Huttenhuis et al. Fluid Phase Equilib. 2008, 264, 99-112) and the H{sub 2}S solubility in aqueous MDEA (Huttenhuis et al. Int. J. Oil, Gas Coal Technol. 2008, 1, 399-424). Here, the model is further extended to predict the behavior of CO{sub 2} and H{sub 2}S when they are present simultaneously in aqueous MDEA. The application of an equation of state is a new development for this type of system, i.e., of acid-gas-amine systems. The molecular interactions are described by Schwarzentruber et al.'s modification of the Redlich-Kwong-Soave equation of state, with terms added to account for ionic interactions in the liquid phase. The model is used to describe acid-gas solubility data for the CO{sub 2}-H{sub 2}S-MDEA-H{sub 2}O system reported in the open literature and experimental data reported here for the CO{sub 2}-H{sub 2}S-MDEA-H{sub 2}O-CH{sub 4} system.

  18. Biosorption of copper (II) ions from synthetic aqueous solutions by drying bed activated sludge

    Energy Technology Data Exchange (ETDEWEB)

    Benaissa, H., E-mail: ho_benaissa@yahoo.fr [Laboratory of Sorbent Materials and Water Treatment, Department of Chemistry, Faculty of Sciences, University of Tlemcen, P.O. Box 119, 13000 Tlemcen (Algeria); Elouchdi, M.A. [Laboratory of Sorbent Materials and Water Treatment, Department of Chemistry, Faculty of Sciences, University of Tlemcen, P.O. Box 119, 13000 Tlemcen (Algeria)

    2011-10-30

    Highlights: {yields} Dried activated sludge has been investigated for the removal of copper ions from aqueous synthetic solutions, in batch conditions. {yields} Copper uptake was time contact, initial copper concentration, initial pH solution and copper salt type dependent. {yields} Maximum copper uptake obtained was q{sub m} = 62.50 mg/g (0.556 mmol/g) under the investigated experimental conditions. - Abstract: In the present work, the usefulness of dried activated sludge has been investigated for the removal of copper ions from synthetic aqueous solutions. Kinetic data and equilibrium sorption isotherm were measured in batch conditions. The influence of some parameters such as: contact time, initial copper concentration, initial pH of solution and copper salt nature on copper biosorption kinetics has been studied. Copper uptake was time contact, initial copper concentration, initial pH solution and copper salt type dependent. Maximum copper sorption was found to occur at initial pH 5. Two simplified kinetic models including a first-order rate equation and a pseudo second-order rate equation were selected to describe the biosorption kinetics. The process followed a pseudo second-order rate kinetics. The process mechanism was found to be complex, consisting of external mass transfer and intraparticle mass transfer diffusion. Copper biosorption process was particle-diffusion-controlled, with some predominance of some external mass transfer at the initial stages for the different experimental parameters studied. Langmuir and Freundlich models were used to describe sorption equilibrium data at natural pH of solution. Results indicated that the Langmuir model gave a better fit to the experimental data than the Freundlich model. Maximum copper uptake obtained was q{sub m} = 62.50 mg/g (0.556 mmol/g) under the investigated experimental conditions. Scanning electron microscopy coupled with X-ray energy dispersed analysis for copper-equilibrated dried activated sludge

  19. Oxidative dissolution of spent nuclear fuel in aqueous alkaline solutions - An alternative to the Purex process?

    Energy Technology Data Exchange (ETDEWEB)

    Runde, Wolfgang; Peper, Shane; Brodnax, Lia; Crooks, William; Zehnder, Ralph; Jarvinen, Gordon

    2004-07-01

    As an alternative to acidic reprocessing of spent nuclear, oxidative dissolution of UO{sub 2} into aqueous alkaline solutions and subsequent separation of fission products is considered. The efficacy of such a method is limited by the kinetics of the UO{sub 2} dissolution and the capacity of alkaline solutions for dissolved U(VI) species. We performed a series of dissolution studies on UO{sub 2} and U{sub 3}O{sub 8} in aqueous alkaline solutions applying various oxidants. Among the oxidative agents commonly used to transform low-valence actinides into their higher oxidation states, H{sub 2}O{sub 2} has proven to be the most effective in basic media. Consequently, we investigated the dissolution of UO{sub 2} and U{sub 3}O{sub 8} in NaOH-H{sub 2}O{sub 2} and Na{sub 2}CO{sub 3}-H{sub 2}O{sub 2} solutions and determined the dissolution kinetics as a function of peroxide and hydroxide (carbonate) concentrations. Methods to remove fission products, e.g., Cs, Sr, Ba and Zr, from alkaline solutions will be evaluated based upon their decontamination factors. We will discuss the feasibility of using chemically oxidizing alkaline solutions as an alternative spent nuclear fuel reprocessing method based on results from experimental quantitative investigations. (authors)

  20. Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

    Science.gov (United States)

    Sarkar, Abhijit; Sinha, Biswajit

    2016-11-15

    The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker.

  1. 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.

  2. 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.

  3. A highly selective sorbent for removal of Cr(VI) from aqueous solutions based on Fe{sub 3}O{sub 4}/poly(methyl methacrylate) grafted Tragacanth gum nanocomposite: Optimization by experimental design

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, Susan, E-mail: ssadeghi@birjand.ac.ir; Rad, Fatemeh Alavi; Moghaddam, Ali Zeraatkar

    2014-12-01

    In this work, poly(methyl methacrylate) grafted Tragacanth gum modified Fe{sub 3}O{sub 4} magnetic nanoparticles (P(MMA)-g-TG-MNs) were developed for the selective removal of Cr(VI) species from aqueous solutions in the presence of Cr(III). The sorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), a vibrating sample magnetometer (VSM), and thermo-gravimetric analysis (TGA). A screening study on operational variables was performed using a two-level full factorial design. Based on the analysis of variance (ANOVA) with 95% confidence limit, the significant variables were found. The central composite design (CCD) has also been employed for statistical modeling and analysis of the effects and interactions of significant variables dealing with the Cr(VI) uptake process by the developed sorbent. The predicted optimal conditions were situated at a pH of 5.5, contact time of 3.4 h, and 3.0 g L{sup −1} dose. The Langmuir, Freundlich, and Temkin isotherm models were used to describe the equilibrium sorption of Cr(VI) by the absorbent, and the Langmuir isotherm showed the best concordance as an equilibrium model. The adsorption process was followed by a pseudo-second-order kinetic model. Thermodynamic investigations showed that the biosorption process was spontaneous and exothermic. - Highlights: • Fe3O4 nanoparticles were modified with Poly(methyl methacrylate) grafted Tragacanth gum • P(MMA)-g-TG -MNPs can preferentially adsorb Cr(VI) in the presence of Cr(III) • The effects of operational parameters on Cr(VI) removal were evaluated by RSM • Adsorption mechanism, kinetics, and isotherm have been explored • The sorbent was successfully used to remove Cr(VI) from different water samples.

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

    Institute of Scientific and Technical Information of China (English)

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

    2012-01-01

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

  5. Enhanced Oil Recovery from Oil-wet Carbonate Rock by Spontaneous Imbibition of Aqueous Surfactant Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Standnes, Dag Chun

    2001-09-01

    The main theme of this thesis is an experimental investigation of spontaneous imbibition (SI) of aqueous cationic surfactant solution into oil-wet carbonate (chalk- and dolomite cores). The static imbibition process is believed to represent the matrix flow of oil and water in a fractured reservoir. It was known that aqueous solution of C{sub 12}-N(CH{sub 3}){sub 3}Br (C12TAB) was able to imbibe spontaneously into nearly oil-wet chalk material, but the underlying mechanism was not understood. The present work was therefore initiated, with the following objectives: (1) Put forward a hypothesis for the chemical mechanism underlying the SI of C12TAB solutions into oil-wet chalk material based on experimental data and (2) Perform screening tests of low-cost commercially available surfactants for their ability to displace oil by SI of water into oil-wet carbonate rock material. It is essential for optimal use of the surfactant in field application to have detailed knowledge about the mechanism underlying the SI process. The thesis also discusses some preliminary experimental results and suggests mechanisms for enhanced oil recovery from oil-wet carbonate rock induced by supply of thermal energy.

  6. Biosorption characteristics of Uranium (VI) from aqueous solution by pollen pini.

    Science.gov (United States)

    Wang, Feihong; Tan, Lichao; Liu, Qi; Li, Rumin; Li, Zhanshuang; Zhang, Hongsen; Hu, Songxia; Liu, Lianhe; Wang, Jun

    2015-12-01

    Uranium biosorption from aqueous solutions by pollen pini (Pinus massoniana pollen) was studied in a bath system. The biosorbent was characterized by Fourier-transform infrared spectroscopy and scanning electron microscope. The influences of pH, contact time and initial uranium concentration at room temperature were investigated and the experimental curves were obtained. The pollen pini exhibited the highest uranium sorption capacity at pH 5.0 after 2 h contact. At pH 2.5 pollen pini also exhibited a good uranium loading capacity (>15%). Therefore biosorption characteristics of uranium from aqueous solution onto pollen pini were examined at pH 2.5 as well. The kinetics followed a pseudo-second-order rate equation and adsorption process was well fitted with the Freundlich isotherm at both pH. The adsorption of uranium by the biosorbent was confirmed by energy dispersive spectroscopy. The present study suggested that pollen pini could be a suitable biosorbent for biosorption uranium (VI) from aqueous solution in a fast, low cost and convenient approach.

  7. Enhancement of Pool Boiling Heat Transfer to Lithium Bromide Aqueous Solution

    Science.gov (United States)

    Furukawa, Masahiro; Kaji, Masuo; Suyama, Takayuki; Sekoguchi, Kotohiko

    An experimental study on enhancement of nucleate pool boiling heat tranfer by placing a sponge metal close to a plain heated surface was conducted in order to improve the heat transfer performance of the high temperature generator of absorption chiller/heater. The sponge metal has three dimensional porous mesh framework like sponge. Boiling curves of water under the atmospheric pressure were compared with those of lithium bromide aqueous solution of mass concentration 55 to 58%. Heat transfer characteristics were improved by 2 to3 times both for water and lithium bromide aqueous solution when the sponge metal was placed on the heated surface with and without cleareance. Three kinds of sponge metals were used for lithium bromide aqueous solution under the reduced pressure (24 kPa). At lower heat fluxes,#6 sponge metal which has the finest mesh and the lowest porosity shows excellent results. At high heat fluxes, however,it causes deterioration of heat transfer. Over the wide range of heat fluxes,# 4 sponge metal was found to be most suitable and the optimal clearence was determined as 0.5 mm. The sponge metal is of good practical use as a device to enhance the boiling, since no special manufacturing is required for placing it on the heated surface.

  8. Accumulation of yellow Monascus pigments by extractive fermentation in nonionic surfactant micelle aqueous solution.

    Science.gov (United States)

    Xiong, Xu; Zhang, Xuehong; Wu, Zhenqiang; Wang, Zhilong

    2015-02-01

    Monascus species can produce various secondary metabolites of polyketide structure. In the current study, it is found that an interesting phenomenon, i.e., submerged culture of Monascus species in an aqueous solution majorly accumulated intracellular orange Monascus pigments exhibiting one peak at 470 nm with absorbance of 32 OD while extractive fermentation in a nonionic surfactant micelle aqueous solution produced extracellular and intracellular yellow Monascus pigments exhibiting one peak at 410 nm with absorbance 30 OD and 12 OD, respectively. The spectrum profiles of both intracellular and extracellular Monascus pigments were affected by surfactant loading, extractive fermentation time, and surfactant adding time. Meanwhile, the instability of orange Monascus pigments in the extracellular nonionic surfactant micelle aqueous solution was also confirmed experimentally. The mechanism behind this phenomenon is attributed to the export of intracellular yellow Monascus pigments into its broth by extractive fermentation. The transferring of intracellular yellow Monascus pigments into its broth blocks yellow Monascus pigments from further enzymatic conversion or eliminates the feedback inhibition of yellow Monascus pigments based on the biosynthetic pathway of Monascus pigments.

  9. Ce/SBA-15联合Oxone去除水中染料RhB的试验研究%Experimental study on RhB removal from aqueous solution by Ce/SBA-15 combined with oxone

    Institute of Scientific and Technical Information of China (English)

    许丹丹

    2014-01-01

    将负载型的Ce∕SBA-15与过硫酸氢钾复合盐(Oxone)联合,考察了该联合体系对染料罗丹明B(RhB)的去除效果。结果表明:该体系中RhB的去除符合准一级动力学方程,提高Ce∕SBA-15和Oxone投加量,降低初始RhB浓度和提高反应温度会增强RhB的去除效果,未调节溶液初始pH值时, RhB的去除效果最好。制备的Ce∕SBA-15在5次循环使用后仍具有约80%的RhB去除率, RhB的去除机制为表面吸附催化。 Ce∕SBA-15与Oxone联合产生以硫酸根自由基为主的处理技术对难降解污染物质具有潜在的实际应用价值。%The effect of supported Ce/SBA-15-oxone combined system on Rhodamine B removal from aqueous solution was investigated. The results showed that, the process of RhB removal followed pseudo-first or‐der kinetics equation, the removal rate of RhB increased with increasing Ce/SBA-15 and oxone dosage, reaction temperature and decreasing initial RhB concentration. The maximum removal efficiency was achieved under the condition that the initial pH value of the solution was unjusted. The material Ce/SBA-15 possessed good reusability, and when reused up to 5 cycles, the removal rate of RhB by it could still maintained at about 80%. The mechanism of RhB removal was surface adsorption and catalysis. It could draw a conclusion that, the com‐bined process of Ce/SBA-15-oxone which could generate sulfate radicals had potential application value in the field of hard-degradable pollutants treatment.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.``

  19. γ-Irradiation of malic acid in aqueous solutions

    Science.gov (United States)

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

    1980-12-01

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

  20. Removal of lead from aqueous solutions by Penicillium biomass

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-09-05

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

  1. VISCOSITY BEHAVIOR OF LACQUER POLYSACCHARIDE IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    QIU Xingping; ZHANG Lina; DU Yumin; QIAN Baogong

    1991-01-01

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

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

    Directory of Open Access Journals (Sweden)

    A. Afaneh

    2011-01-01

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

  3. Aqueous solution of basic fuchsin as food irradiation dosimeter

    Institute of Scientific and Technical Information of China (English)

    Hasan M. KHAN; Shagufta NAZ

    2007-01-01

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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. A computational approach to calculate the heat of transport of aqueous solutions

    Science.gov (United States)

    Di Lecce, Silvia; Albrecht, Tim; Bresme, Fernando

    2017-01-01

    Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl− ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions.

  9. Volumetric behaviour of amino acids and their group contributions in aqueous lactose solutions at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Amalendu, E-mail: palchem@sify.co [Department of Chemistry, Kurukshetra University, Kurukshetra 136 119 (India); Chauhan, Nalin [Department of Chemistry, Kurukshetra University, Kurukshetra 136 119 (India)

    2011-02-15

    Densities, {rho}, for glycine, L-alanine, L-valine, and L-leucine [(0.05 to 0.30) m] in aqueous lactose solutions ranging from pure water to 6 mass% lactose were determined at T = (293.15, 298.15, 303.15, and 308.15) K. The density was used to compute apparent molar volume, V{sub {phi}}, partial molar volume at infinite dilution, V{sub {phi}}{sup o}, and experimental slope, S{sub V} were obtained and interpreted in terms of solute-solvent and solute-solute interactions. These data were used to calculate the ({partial_derivative}V{sub {phi}}{sup 0}/{partial_derivative}T){sub P} values. The partial molar volume of transfer, {Delta}V{sub {phi}}{sup 0} from water to aqueous lactose solutions at infinite dilution has also been calculated. In addition to this, the linear correlation of V{sub {phi}}{sup 0} with number of carbon atoms in the alkyl chain of amino acids was utilized to determine the respective contributions of NH{sub 3}{sup +}COO{sup -}, and CH{sub 2} groups to V{sub {phi}}{sup 0}.

  10. 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.

  11. 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....

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. {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.

  6. 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.

  7. Stepwise aggregation of dimethyl-di-n-octylammonium chloride in aqueous solutions: from dimers to vesicles.

    Science.gov (United States)

    Leclercq, Loïc; Nardello-Rataj, Véronique; Turmine, Mireille; Azaroual, Nathalie; Aubry, Jean-Marie

    2010-02-01

    The self-aggregation of dimethyl-di-n-octylammonium chloride, in diluted aqueous solutions, was studied with various experimental and theoretical techniques: zetametry, conductimetry, dimethyl-di-n-octylammonium and chloride-selective electrodes, tensiometry, NMR spectroscopy ((1)H and DOSY), and molecular modeling (PM3 and molecular dynamic). The combination of the data obtained by these techniques led us to propose a stepwise aggregation process with increasing concentration: dimers (0.2-10 mM), bilayers (10-30 mM), and finally vesicles (>30 mM).

  8. Interactions between crystal violet and AOT in aqueous solutions and in AOT/isooctane/water microemulsions

    Institute of Scientific and Technical Information of China (English)

    HAO Xiaojuan; AN Xueqin; CHEN Zhiyun; SHEN Weiguo

    2004-01-01

    The absorbance of crystal violet (CV) in a series of aqueous solutions and a series of sodium bis(2-ethyl- hexyl) sulfosuccinate (AOT)/isooctane/water microemulsions has been determined. Association models have been used to analyse the experimental data to obtain the association constants of CV and AOT in the above two media. It was found that about up to 57% CV was associated by AOT in AOT/ isooctane/water microemulsions, which reduced the reaction rate of alkaline fading of crystal violet in the microemulsions.

  9. Polar-solvation classical density-functional theory for electrolyte aqueous solutions near a wall

    Science.gov (United States)

    Warshavsky, Vadim; Marucho, Marcelo

    2016-04-01

    A precise description of the structural and dielectric properties of liquid water is critical to understanding the physicochemical properties of solutes in electrolyte solutions. In this article, a mixture of ionic and dipolar hard spheres is considered to account for water crowding and polarization effects on ionic electrical double layers near a uniformly charged hard wall. As a unique feature, solvent hard spheres carrying a dipole at their centers were used to model water molecules at experimentally known concentration, molecule size, and dipolar moment. The equilibrium ionic and dipole density profiles of this electrolyte aqueous model were calculated using a polar-solvation classical density-functional theory (PSCDFT). These profiles were used to calculate the charge density distribution, water polarization, dielectric permittivity function, and mean electric potential profiles as well as differential capacitance, excess adsorptions, and wall-fluid surface tension. These results were compared with those corresponding to the pure dipolar model and unpolar primitive solvent model of electrolyte aqueous solutions to understand the role that water crowding and polarization effects play on the structural and thermodynamic properties of these systems. Overall, PSCDFT predictions are in agreement with available experimental data.

  10. Experimental validation of a rate-based model for CO2 capture using an AMP solution

    DEFF Research Database (Denmark)

    Gabrielsen, Jostein; Svendsen, H. F.; Michelsen, Michael Locht

    2007-01-01

    Detailed experimental data, including temperature profiles over the absorber, for a carbon dioxide (CO"2) absorber with structured packing in an integrated laboratory pilot plant using an aqueous 2-amino-2-methyl-1-propanol (AMP) solution are presented. The experimental gas-liquid material balance...

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. XANES Reveals the Flexible Nature of Hydrated Strontium in Aqueous Solution.

    Science.gov (United States)

    D'Angelo, Paola; Migliorati, Valentina; Sessa, Francesco; Mancini, Giordano; Persson, Ingmar

    2016-05-05

    X-ray absorption near-edge structure (XANES) spectroscopy has been used to determine the structure of the hydrated strontium in aqueous solution. The XANES analysis has been carried out using solid [Sr(H2O)8](OH)2 as reference model. Classical and Car-Parrinello molecular dynamics (MD) simulations have been carried out and in the former case two different sets of Lennard-Jones parameters have been used for the Sr(2+) ion. The best performing theoretical approach has been chosen on the basis of the experimental results. XANES spectra have been calculated starting from MD trajectories, without carrying out any minimization of the structural parameters. This procedure allowed us to properly account for thermal and structural fluctuations occurring in the aqueous solution in the analysis of the experimental spectrum. A deconvolution procedure has been applied to the raw absorption data thus increasing the sensitivity of XANES spectroscopy. One of the classical MD simulations has been found to provide a XANES theoretical spectrum in better agreement with the experimental data. An 8-fold hydration complex with a Sr-O distance of 2.60 Å has been found to be compatible with the XANES data, in agreement with previous findings. However, the hydration shells of the strontium ions have been found to have a flexible nature with a fast ligand exchange rate between the first and second hydration shell occurring in the picosecond time scale.

  17. Studies on the Solute Solvent Interaction of Nimesulide in Aqueous Solutions of Hydrotropic Agents at Different Temperatures

    Directory of Open Access Journals (Sweden)

    Chandravir S. Solanki

    2010-01-01

    Full Text Available The present study deals with experiments so as to highlight the solute (drug nimesulide - solvent(water interactions and related modifications in case of the presence of hydrotropic agents at different temperatures T(=298.15 to 313.15K. Density and viscosity values of nimesulide have been determined in water in (0.1, 0.2, 0.4, 0.6, 0.8, 1 and 2 mol dm-3 aqueous solutions of hydrotropic agents (sodium benzoate, sodium salicylate, sodium bromide and nicotinamide at temperatures 298.15, 303.15, 308.15 and 313.15 K where as the solubility was studied at 308.15 K. From the density values, the limiting partial molar volumes and expansibilities have been calculated. The experimental viscosity values have been analyzed in terms of jones-dole equation and on the basis of transition theory for relative viscosity.

  18. 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).

  19. 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.

  20. Recovery of nickel from aqueous solutions by complexation-ultrafiltration process with sodium polyacrylate and polyethylenimine.

    Science.gov (United States)

    Shao, Jiahui; Qin, Shu; Davidson, Joshua; Li, Wenxi; He, Yiliang; Zhou, H Susan

    2013-01-15

    The recovery of nickel from aqueous dilute solutions by complexation-ultrafiltration process with sodium polyacrylate (PAAS) and polyethylenimine (PEI) was studied. Experiments were performed as a function of aqueous pH, polymer/Ni(2+) ratio and background electrolyte concentration. At optimum experimental conditions, the nickel removal rate reaches 99.5% using PAAS and 93.0% using PEI as the complexation agent. The nickel removal rate was found to decrease as the adding salt NaCl concentration increases for both complexation agents. A series of experiments implied that the mechanism could be the compressing electric double layer other than the competitive complexation. Diafiltration technique was further performed to regenerate complexation agents and recover nickel. The nickel removal rates were found to be close to those obtained with the original PEI and PAAS. Finally, Langmuir-type binding isotherm equation was employed to evaluate the extent of nickel bound to PAAS and PEI. The overall results from the two-step process of complexation-UF and decomplexation-UF separation showed that it could be a promising method for nickel removal and recovery from aqueous solutions.

  1. Elaeagnus angustifolia STONE AS A LOW-COST BIOSORBENT PRECURSOR FOR REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION

    OpenAIRE

    KILIÇ, Murat; POYRAZ, Zakir

    2012-01-01

    In this study, the removal of methylene blue from aqueous solutions by biosorption onto Elaeagnus angustifolia stone has investigated. Optimum biosorption conditions have determined as a function of pH, biosorbent dosage, initial methylene blue concentration, contact time and temperature of the solution for the removal of methylene blue. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models have used to describe the biosorption isotherm model. The experimental data have fitted t...

  2. Mineral Surface after Reaction with Aqueous Solution at High Temperatures and Pressures

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This work presents new experimental results on surface chemistry of reacting minerals and interface kinetics between mineral and aqueous solutions. These experiments were carried out using a flow reactor (packed bed reactor) of an open system as well as a continuous stirred tank reactor, CSTR. The authors measured reaction rates of such minerals as zeolite, albite and carbonate (rhodochrosite, dolomite) in various solutions, and tested corresponding mineral surface by using SEM, XPS, SIMS, etc. This paper mainly presents the experimental results of zeolite dissolution in water and in low pH solutions at room temperature, and dolomite dissolution at elevated temperatures. The results show that the release rates of Si, Al and Na of zeolite are different in most cases. The incongruent dissolution of zeolite is related to surface chemical modifications. The Na, Al and Si release rates for dissolution of albite and zeolite in water and various solutions were measured as a function of temperature, flow velocity, pH and solution composition in the reaction system. In most cases, dissolutions of both albite and zeolite are incongruent. Dissolution of dolomite is also incongruent in most cases and varied with T, pH, and nature of aqueous solutions. For dolomite dissolution, the release rates of Mg are less than those of Ca at high temperatures as T increases from 25 to 300° C. SIMS study indicates that the contents of Al, Na and Si in the leached layer of zeolite or albite surface, change with the distance from the surface, exhibiting a non-linear behaviour within a thickness range of 1000%. The distributions of Ca, Mg, Mn, H and Cl in the leached surface layer of carbonate have a non-linear behaviour too.

  3. Uranium removal from aqueous solution by coir pith: equilibrium and kinetic studies.

    Science.gov (United States)

    Parab, Harshala; Joshi, Shreeram; Shenoy, Niyoti; Verma, Rakesh; Lali, Arvind; Sudersanan, M

    2005-07-01

    Basic aspects of uranium adsorption by coir pith have been investigated by batch equilibration. The influence of different experimental parameters such as final solution pH, adsorbent dosage, sorption time, temperature and various concentrations of uranium on uptake were evaluated. Maximum uranium adsorption was observed in the pH range 4.0-6.0. The Freundlich and Langmuir adsorption models were used for the mathematical description of the adsorption equilibrium. The equilibrium data fitted well to both the equilibrium models in the studied concentration range of uranium (200-800 mg/l) and temperatures (305-336 K). The coir pith exhibited the highest uptake capacity for uranium at 317 K, at the final solution pH value of 4.3 and at the initial uranium concentration of 800 mg/l. The kinetics of the adsorption process followed a second-order adsorption. The adsorbent used proved to be suitable for removal of uranium from aqueous solutions. 0.2 N HCl was effective in uranium desorption. The results indicated that the naturally abundant coir pith of otherwise nuisance value exhibited considerable potential for application in removal of uranium from aqueous solution.

  4. [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.

  5. 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.

  6. On the performance of quantum chemical methods to predict solvatochromic effects. The case of acrolein in aqueous solution

    DEFF Research Database (Denmark)

    Aidas, Kestutis; Møgelhøj, Andreas; Nilsson, Elna Johanna Kristina

    2008-01-01

    The performance of the Hartree–Fock method and the three density functionals B3LYP, PBE0, and CAM-B3LYP is compared to results based on the coupled cluster singles and doubles model in predictions of the solvatochromic effects on the vertical n¿* and ¿* electronic excitation energies of acrolein...... of acrolein in vapor phase and aqueous solution. The gas-to-aqueous solution shift of the n¿* excitation energy is well reproduced by using all density functional methods considered. However, the B3LYP and PBE0 functionals completely fail to describe the ¿* electronic transition in solution, whereas...... the recent CAM-B3LYP functional performs well also in this case. The ¿* excitation energy of acrolein in water solution is found to be very dependent on intermolecular induction and nonelectrostatic interactions. The computed excitation energies of acrolein in vacuum and solution compare well to experimental...

  7. Vapor Pressure of Saturated Aqueous Solutions of Potassium Sulfate from 310 K to 345 K

    Directory of Open Access Journals (Sweden)

    Matias O. Maggiolo

    2011-01-01

    Full Text Available The experimental evaluation of the vapor pressure of saturated aqueous solutions of potassium sulfate was carried out in the range of temperatures 310 K≤T≤345 K. The experimental data were used to determine the corresponding values of the water activity in such solutions. The analytical expressions as a function of temperature of both, vapor pressure and water activity, were obtained from the correlation of the experimental results. The vapor pressure expression was also extrapolated to a different temperature range in order to make a comparison with the results obtained by other authors.

  8. 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

  9. 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

  10. 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...

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Tea Wastes Efficiency on Removal of Cd(II From Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mehrdad Cheraghi

    2016-07-01

    Full Text Available Background & Aims of the Study: Heavy metals, such as cadmium (Cd(II, enter into the environment and cause health hazard due to their toxicity and bioaccumulation in the human body. Therefore, they must be removed from water. In recent years, much attention has been focused on the use of material residues as low-cost adsorbents for the removal of heavy metal ions from aqueous solutions. The aim of this paper is the assessment of tea wastes efficiency on removal of Cd(II from aqueous solutions. Materials and Methods: The present study was conducted in experimental scale. In this paper, tea wastes were prepared and used as an adsorbent for the removal of Cd(II ions from water. In batch tests, the effect of parameters like pH (1.0-8.0, initial metal concentration (100-800 mg L-1, contact time (15-120 min, adsorbent dose (1.0-5.0 g and temperature (25-55 °C on the adsorption process was studied. Results: The results demonstrated that the maximum percentage of Cd(II adsorption was found at pH 6.0 and the equilibrium was achieved after 60 min with 3.0 g tea wastes. The experimental isotherm data were analyzed, using the Langmuir and Freundlich models and it was found that the removal process followed the Langmuir isotherm. In addition, the adsorption kinetics followed the pseudo-second-order kinetic model. The maximum adsorption capacity calculated by Langmuir fitting was 71.4 mg g−1. Conclusion: The results suggest that tea wastes could be employed as an effective material for the removal of Cd(II ions from aqueous solutions and the maximum adsorption capacity was found to be 71.4 mg g−1.

  16. 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.

  17. Experimentally observed flows inside inkjet-printed aqueous rivulets

    Science.gov (United States)

    Bromberg, Vadim; Singler, Timothy

    2013-11-01

    Understanding the flow inside sessile liquid masses of different shapes is important in a variety of solution-based material deposition and patterning processes. We investigated the shape evolution and internal flow of inkjet-printed aqueous rivulets of finite length using optical microscopy. Rivulets were formed by printing a pre-determined number of drops at controlled frequency and spatial overlap. Capillary-driven rivulet breakup into individual drops was inhibited by chemical modification of substrates that resulted in controlled contact angle hysteresis with zero static receding contact angle. A variety of novel capillary- and evaporatively-driven flows were identified using fluorescent particles as flow tracers. Flow regimes were investigated as a function of advancing contact angle, deposition parameters, and fluid properties.

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

    Directory of Open Access Journals (Sweden)

    M.H. Sayadi

    2016-12-01

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

  19. Electrochemical degradation of amaranth aqueous solution on ACF.

    Science.gov (United States)

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

    2006-09-21

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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Untangling Element Fluxes From The Subducting Slabs: Aqueous Solutions Through The Electrostatic Lense

    Science.gov (United States)

    Galvez, M.; Connolly, J. A.; Manning, C. E.

    2015-12-01

    Understanding the deep cycling of elements hinges on characterizing the chemistry of fluids in subduction zones. Aqueous solutions dielectric properties determine their characteristics as solvents for rocks. Predicting the composition and speciation of fluid solutions at equilibrium with complex mineral assemblages has been a long lasting challenge. We have developed a model to explore the composition and speciation of metamorphic aqueous solutions to upper mantle pressure and temperature. Our model combines Gibbs free energy minimization of rock and molecular fluids with an electrostatic approach to describe solute-solute and solute-solvent interactions in the fluid phase. Using an extension of the Debye-Onsager-Kirkwood model to characterize the dielectric properties of COH solutions, we derive aqueous fluid speciation by solving the mass action and charge balance of the system. This framework is applied to various slab lithologies. We find, e.g., that the pH of carbonated basalts and pelites is alkaline, i.e. ~2-2.5 pH units above neutrality, in C and Cl-free fluids and shows an isothermal decrease above the albite-jadeite-quartz equilibrium, at P ~ 2 GPa. C and Chlorine (1M) decrease the alkalinity by a combined ~ 1.5 pH unit, with variations tied to the thermal structure and mineral assemblages along typical P-T paths. The results produced are compared with experimental solubility measurements on identical systems. Significant discrepancies reveal that the process of solute polymerization at elevated T and P is more general than previously recognized. Unaccounted species contain, in addition to Na, Si and Al, an important fraction of the total dissolved load of the elements K, Ca and Mg (>50% at T= 600 °C and P = 2 Ga). Finally, we show that knowledge of the acid-base properties of metamorphic fluid solutions affect the (de)coupling between C and alkali-earth mobility, and magnitude of low-T C transfers associated to carbonate dissolution through time. This

  7. Biosorption of malachite green from aqueous solutions by Pleurotus ostreatus using Taguchi method.

    Science.gov (United States)

    Chen, Zhengsuo; Deng, Hongbo; Chen, Can; Yang, Ying; Xu, Heng

    2014-03-12

    Dyes released into the environment have been posing a serious threat to natural ecosystems and aquatic life due to presence of heat, light, chemical and other exposures stable. In this study, the Pleurotus ostreatus (a macro-fungus) was used as a new biosorbent to study the biosorption of hazardous malachite green (MG) from aqueous solutions. The effective disposal of P. ostreatus is a meaningful work for environmental protection and maximum utilization of agricultural residues.The operational parameters such as biosorbent dose, pH, and ionic strength were investigated in a series of batch studies at 25°C. Freundlich isotherm model was described well for the biosorption equilibrium data. The biosorption process followed the pseudo-second-order kinetic model. Taguchi method was used to simplify the experimental number for determining the significance of factors and the optimum levels of experimental factors for MG biosorption. Biosorbent dose and initial MG concentration had significant influences on the percent removal and biosorption capacity. The highest percent removal reached 89.58% and the largest biosorption capacity reached 32.33 mg/g. The Fourier transform infrared spectroscopy (FTIR) showed that the functional groups such as, carboxyl, hydroxyl, amino and phosphonate groups on the biosorbent surface could be the potential adsorption sites for MG biosorption. P. ostreatus can be considered as an alternative biosorbent for the removal of dyes from aqueous solutions.

  8. Adsorption of Pb(2+) from aqueous solution using spinel ferrite prepared from steel pickling sludge.

    Science.gov (United States)

    Fang, Binbin; Yan, Yubo; Yang, Yang; Wang, Fenglian; Chu, Zhen; Sun, Xiuyun; Li, Jiansheng; Wang, Lianjun

    2016-01-01

    In this paper, spinel ferrite with high crystallinity and high saturation magnetization was successfully prepared from steel pickling sludge by adding iron source and precipitator in the hydrothermal condition. The obtained spinel ferrite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and Zeta potential methods and investigated as an adsorbent for removal of Pb(2+) from aqueous solution. Batch experiments were performed by varying the pH values, contact time, temperature and initial metal concentration. The result of pH impact showed that the adsorption of Pb(2+) was a pH dependent process, and the pH 5.8 ± 0.2 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies revealed that Pb(2+) adsorption onto spinel ferrite followed a pseudo-second order model, and the Langmuir isotherm model provided the perfect fit to the equilibrium experimental data. At different temperatures, the maximum Pb(2+) adsorption capacities calculated from the Langmuir equation were in the range of 126.5-175.4 mg/g, which can be in competition with other adsorbents. The thermodynamic results showed that the spinel ferrite could spontaneously and endothermically adsorb Pb(2+) from aqueous solution. The regeneration studies showed that spinel ferrite could be used five times (removal efficiency (%) >90%) by desorption with HNO3 reagent.

  9. A relativistic density functional study of uranyl hydrolysis and complexation by carboxylic acids in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Rupashree Shyama

    2009-02-10

    In this work, the complexation of uranium in its most stable oxidation state VI in aqueous solution was studied computationally, within the framework of density functional (DF) theory. The thesis is divided into the following parts: Chapter 2 briefly summarizes the relevant general aspects of actinide chemistry and then focuses on actinide environmental chemistry. Experimental results on hydrolysis, actinide complexation by carboxylic acids, and humic substances are presented to establish a background for the subsequent discussion. Chapter 3 describes the computational method used in this work and the relevant features of the parallel quantum chemistry code PARAGAUSS employed. First, the most relevant basics of the applied density functional approach are presented focusing on relativistic effects. Then, the treatment of solvent effects, essential for an adequate modeling of actinide species in aqueous solution, will be introduced. At the end of this chapter, computational parameters and procedures will be summarized. Chapter 4 presents the computational results including a comparison to available experimental data. In the beginning, the mononuclear hydrolysis product of UO{sub 2}{sup 2+}, [UO{sub 2}OH]{sup +}, will be discussed. The second part deals with actinide complexation by carboxylate ligands. First of all the coordination number for uranylacetate will be discussed with respect to implications for the complexation of actinides by humic substances followed by the uranyl complexation of aromatic carboxylic acids in comparison to earlier results for aliphatic ones. In the end, the ternary uranyl-hydroxo-acetate are discussed, as models of uranyl humate complexation at ambient condition.

  10. Elaeagnus angustifolia STONE AS A LOW-COST BIOSORBENT PRECURSOR FOR REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION

    Directory of Open Access Journals (Sweden)

    Murat KILIÇ

    2012-06-01

    Full Text Available In this study, the removal of methylene blue from aqueous solutions by biosorption onto Elaeagnus angustifolia stone has investigated. Optimum biosorption conditions have determined as a function of pH, biosorbent dosage, initial methylene blue concentration, contact time and temperature of the solution for the removal of methylene blue. Langmuir, Freundlich and Dubinin-Radushkevich (D-R isotherm models have used to describe the biosorption isotherm model. The experimental data have fitted to pseudo-first order, pseudo-second order and intraparticle diffusion model to examine the sorption kinetics. The values of ΔG°, ΔH° and ΔS° have calculated by thermodynamic study to determine the nature of biosorption process. Experimental results have shown that Elaeagnus angustifolia stone can be used as an effective and low cost biosorbent precursor for the removal of methylene blue from aqueous solutions.

  11. Effects of the aqueous extract solution of Radix Puerariae on tissues of brain, kidney, fat and pancreas in experimental diabetic rats%葛根水煎液对糖尿病大鼠脑、肾、脂肪、胰腺组织的影响

    Institute of Scientific and Technical Information of China (English)

    涂星; 卢映; 唐洪梅; 房财富

    2013-01-01

    目的:观察葛根水煎液对糖尿病大鼠的脑、肾、脂肪和胰腺组织的影响.方法:设立正常对照组、模型对照组和给药模型组,采用高脂饮食加腹腔注射链脲佐菌素(STZ)对2型糖尿病大鼠造模,运用石蜡包埋切片技术制作脑、肾、脂肪和胰腺的组织切片,并作光镜观察.结果:葛根水煎液能够较好地修复胰岛代偿性肥大,改善病理状态下的胰岛的体积和细胞形态;减小肾小球体积的病理性增大;改善糖尿病大鼠大脑皮层神经元细胞的变性以及脂肪细胞的变性、坏死和溶解等改变.结论:葛根水煎液能够修复和保护实验型糖尿病大鼠的脑、肾、脂肪和胰腺组织,改善其生理机能.%OBJECTIVE To observe the effects of the aqueous extract solution of Radix Puerariae on brain,kidney,fat and pancreas tissues.METHODS Three groups-the normal control group,model control group and experimental model group were set up.The type 2 diabetic model was established by feeding the Wistar rats with the high fat food firstly and intra-peritoneal injection with streptozotocin(STZ).The technology of paraffin wax slice was used to make the pathological section of brain,kidney,fat and pancreas tissue and then observed them under light microscope (LM).RESULTS The aqueous extract solution of Radix Puerariae was able to repair the compensatory hypertrophy of pancreatic islets and could ameliorate the volume and shape of the islet cell which was under pathological state.It could diminish the pathological dilatation of glomerulus,and ameliorate the degeneration of neuronal cells which located in cerebral cortex and the degeneration,lytic necrosis of the adipocyte.CONCLUSION The aqueous extract solution of Radix Puerariae was able to protect and repair the brain,kidney,fat and pancreatic tissue of the experimental diabetic rats,and to improve their physiological functions.

  12. Removal of Pb(II) from aqueous solution on chitosan/TiO(2) hybrid film.

    Science.gov (United States)

    Tao, Yugui; Ye, Lianbin; Pan, Jun; Wang, Yaoming; Tang, Bin

    2009-01-30

    This paper presents the adsorption of Pb(II) from aqueous solution using chitosan/TiO(2) hybrid film (CTF) adsorbent. Batch experiments were carried out as a function of solution pH, adsorption time, Pb(II) concentration and temperature. The equilibrium data fitted well with the linear Freundlich model. The adsorption process was proved to be the second grade reaction and the theoretically maximum adsorption amount at equilibrium was 36.8 mg-Pb/g. The influence parameters were optimized by response surface method (RSM), such as initial metal concentration, pH and temperature. The extreme points were gained by the Statistical Analysis System software: initial metal concentration is 50-55 mg/l, pH is 3-4 and temperature is 60 degrees C. Very high regression coefficient (R(2)=0.9689) indicates excellent evaluation of experimental data by second-order polynomial regression model. Under this condition the theoretical adsorption efficiency is 90.6%. It illuminates that this model is reliable to optimize the adsorption process and CTF is suitable for adsorbing Pb(II) from aqueous solution.

  13. Catalytic ozonation of pentachlorophenol in aqueous solutions using granular activated carbon

    Science.gov (United States)

    Asgari, Ghorban; Samiee, Fateme; Ahmadian, Mohammad; Poormohammadi, Ali; solimanzadeh, Bahman

    2014-11-01

    The efficiency of granular activated carbon (GAC) was investigated in this study as a catalyst for the elimination of pentachlorophenol (PCP) from contaminated streams in a laboratory-scale semi-batch reactor. The influence of important parameters including solution pH (2-10), radical scavenger (tert-butanol, 0.04 mol/L), catalyst dosage (0.416-8.33 g/L), initial PCP concentration (100-1000 mg/L) and ozone flow rate (2.3-12 mg/min) was examined on the efficiency of the catalytic ozonation process (COP) in degradation and mineralization of PCP in aqueous solution. The experimental results showed that catalytic ozonation with GAC was most effective at pH of 8 with ozone flow rate of 12 mg/min and a GAC dosage of 2 g. Compared to the sole ozonation process (SOP), the removal levels of PCP and COP were, 98, and 79 %, respectively. The degradation rate of kinetics was also investigated. The results showed that using a GAC catalyst in the ozonation of PCP produced an 8.33-fold increase in rate kinetic compared to the SOP under optimum conditions. Tert-butanol alcohol (TBA) was used as a radical scavenger. The results demonstrated that COP was affected less by TBA than by SOP. These findings suggested that GAC acts as a suitable catalyst in COP to remove refractory pollutants from aqueous solution.

  14. Adsorption of Cu2+ from aqueous solution onto modified glass beads with 3-aminopropyltriethoxysilane

    Directory of Open Access Journals (Sweden)

    Z Torkshavand

    2014-08-01

    Full Text Available The discharge of heavy metals into the aquatic ecosystem is a main concern over the last few decades. These pollutants are introduced into aquatic systems as a result of various industrial operations. This study investigates the efficiency of the modified glass beads with APTES ligand for removal of Cu2+ from the aqueous solution. Response surface methodology based on Box-Behnken was used to assess the effect of independent variables, including flow rate, solution pH, initial concentration and glass beads size on the response function and prediction of the best response value. Atomic absorption spectroscopic analysis of eluents of a column of the modified glass beads showed that Cu2+ ion was more than 90% entrapped on a column of glass beads. The isotherm evaluations indicate that the equilibrium data for Cu2+ adsorption could be fitted with the Langmuir model. Experimental data were also evaluated in terms of adsorption kinetics using the pseudo-first-order and pseudo-second-order kinetic models. The results also showed that the adsorption process of the Cu2+ well suited with the pseudo-second-order kinetics model. All the results demonstrated that modified glass beads successfully absorbed heavy metals from aqueous solution.

  15. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

    Science.gov (United States)

    Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

    2016-10-01

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

  16. Adsorption of Methylene Blue from Aqueous Solutions by Polyvinyl Alcohol/Graphene Oxide Composites.

    Science.gov (United States)

    Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Wang, Xiaohui; Hu, Song; Chen, Long; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2016-02-01

    As a new member of the carbon family, graphene oxide (GO) has shown excellent adsorption ability to micro-pollutants in aqueous solutions. However, its tiny size makes it difficult to be removed from aqueous solutions using the conventional separation methods, which limits its practical application in the environmental protection. In this study, polyvinyl alcohol (PVA) was used as carrier immobilizing GO, and novel PVA/GO composites were prepared. The morphology and physicochemical properties of the composites were characterized by SEM, FTIR and TGA analysis. The adsorption properties of methylene blue (MB) onto the composites were studied through investigating the experimental parameters such as solution pH, adsorbent dosage, contact time and temperature. The isotherm data were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich models. The calculated maximum adsorption capacity reached 476.2 mg/g at 50% GO content. The pseudo-first-order kinetic, pseudo-second-order kinetic and intra-particle diffusion models were used to explore the adsorption kinetics. The results showed that the dynamic data were fitted to the pseudo-second-order kinetic model.

  17. Sorption of Ni(II) ions from aqueous solution by Lewatit cation-exchange resin.

    Science.gov (United States)

    Dizge, Nadir; Keskinler, Bülent; Barlas, Hulusi

    2009-08-15

    Ion-exchange is an alternative process for uptake of heavy metals from aqueous solutions. In the present study, the sorption of nickel(II) ions from aqueous solution was investigated by using Lewatit MonoPlus SP 112 (strongly acidic, macroporous cation-exchange resin) in a batch adsorption system as a function of pH (2.0-8.0), initial nickel concentration (50-200 mg/L), resin dosage (0.5-2.0 g/L), contact time (0.5-3h), and temperatures (298-318K). The data were analyzed on the basis of Lagergren pseudo-first order, pseudo-second order (Types 1-5), Elovich and external, Weber-Morris intraparticle, pore-surface mass diffusion models. The experimental data showed that the maximum pH for efficient sorption of nickel(II) was 6.0. At the optimal conditions, nickel(II) ions sorption on the resin was decreased when the initial metal concentration increased. The results indicated that the resin dosage strongly affected the amount of nickel(II) ions removed from aqueous solution. The adsorption process was very fast due to 80% of nickel(II) sorption was occurred within 30 min and equilibrium was reached at about 90 min. Freundlich and Langmuir adsorption isotherm models were used for sorption equilibrium data and the maximum adsorption capacity (171 mg/g) of Lewatit MonoPlus SP 112 was obtained from Langmuir isotherm. The thermodynamic parameters (DeltaG degrees, free energy change; DeltaS degrees, enthalpy change; and DeltaH degrees, entropy change) for sorption of nickel(II) ions were evaluated. The rise in temperature caused a partly increase in the value of the equilibrium constant (K(c)) for the sorption of nickel(II) ions. Moreover, column flow adsorption study was also studied. Breakthrough curves were obtained from column flow studies by using both synthetic solution and rinsing bath water of filter industry. The column regeneration was carried out for two sorption-desorption cycles. The eluant used for regeneration of the cation-exchange resin was 7% (w/w) HCl. The

  18. Removal of chlorophenols from aqueous solutions by sorption onto walnut, pistachio and hazelnut shells

    Directory of Open Access Journals (Sweden)

    Kuśmierek Krzysztof

    2015-03-01

    Full Text Available The efficiency of walnut, pistachio and hazelnut shells to remove three monochlorophenols (2-CP, 3-CP and 4-CP from aqueous solutions has been investigated. To describe the kinetic data pseudo-first and pseudo-second order models were used. The kinetics data were fitted better into the pseudo-second order model with the coefficient of determination values greater than 0.99. The k2 values increased in the order 4-CP < 3-CP < 2-CP. Sorption was also analyzed as a function of solution concentration at equilibrium. The experimental data received were found to be well described by the Freundlich isotherm equation. Effectiveness of chlorophenols removal from water on the walnut, pistachio and hazelnut shells was comparable. Individual differences in sorption of monochlorophenols were also negligible.

  19. Study of Bovine Serum Albumin Solubility in Aqueous Solutions by Intrinsic Viscosity Measurements

    Directory of Open Access Journals (Sweden)

    Martin Alberto Masuelli

    2013-01-01

    Full Text Available The behavior of bovine serum albumin (BSA in water is scarcely studied, and the thermodynamic properties arising from the experimental measurements have not been reported. Intrinsic viscosity measurements are very useful in assessing the interaction between the solute and solvent. This work discussed in a simple determination of the enthalpy of BSA in aqueous solution when the concentration ranges from 0.2 to 36.71% wt. and the temperature from 35 to 40°C. The relationship between the concentration and intrinsic viscosity is determined according to the method of Huggins. The temperature increase reduces the ratio between inherent viscosity and concentration (ηi/c. This is reflected in the Van't Hoff curve. Furthermore, this work proposes hydrodynamic cohesion value as an indicator of the degree of affinity of protein with water and thermodynamic implications in conformational changes.

  20. Boron removal from aqueous solutions by ion-exchange resin: column sorption-elution studies.

    Science.gov (United States)

    Köse, T Ennil; Oztürk, Neşe

    2008-04-01

    A column sorption-elution study was carried out by using a strong base anion-exchange resin (Dowex 2 x 8) for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of feed flow rate and the total and breakthrough capacity values of the resin were calculated. The boron on the resin was quantitatively eluted with 0.5M HCl solution at different flow rates. Three consecutive sorption-elution-washing-regeneration-washing cycles were applied to the resin in order to investigate the reusability of the ion-exchange resin. Total capacity values remained almost the same after three sorption-elution-regeneration cycles. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic column parameters required for process design. The results proved that the models would describe the breakthrough curves well.

  1. Ozone degradation of alkylbenzene sulfonate in aqueous solutions using a stirred tank reactor with recirculation.

    Science.gov (United States)

    Jurado-Alameda, Encarnación; Vicaria, José M; Altmajer-Vaz, Deisi; Luzón, Germán; Jiménez-Pérez, José L; Moya-Ramírez, Ignacio

    2012-01-01

    The degradation of linear alkylbenzene sulfonates (LAS) in aqueous solutions by ozone has been investigated. The ozonation process was performed in a stirred tank reactor with recirculation which simulates the clean-in-place process used in many industrial facilities. The gas-liquid mass transfer of ozone in a buffer solution at different temperatures (25-55°C) was also studied in the same device, revealing that ozone decomposition can be considered negligible under the experimental conditions assayed. The effect of the initial LAS concentration, temperature, and ozone concentration on the concentration of homologues and total LAS were analysed as a function of time. Both concentrations diminished with time, this effect being more significant when higher temperatures were assayed. The relative proportion of homologues shows that the homologues of higher chain length are degraded in a greater proportion than are the homologues with shorter chain lengths.

  2. Terahertz microfluidic chips for detection of amino acids in aqueous solutions

    Science.gov (United States)

    Su, Bo; Zhang, Cong; Fan, Ning; Zhang, Cunlin

    2016-11-01

    Microfluidic technology can control the fluidic thickness accurately in less than 100 micrometers. So the combination of terahertz (THz) and microfluidic technology becomes one of the most interesting directions towards biological detection. We designed microfluidic chips for terahertz spectroscopy of biological samples in aqueous solutions. Using the terahertz time-domain spectroscopy (THz-TDS) system, we experimentally measured the transmittance of the chips and the THz absorption spectra of L-threonine and L-arginine, respectively. The results indicated the feasibility of performing high sensitivity THz spectroscopy of amino acids solutions. Therefore, the microfluidic chips can realize real-time and label-free measurement for biochemistry samples in THz-TDS system.

  3. Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder.

    Science.gov (United States)

    Chowdhury, Shamik; Chakraborty, Sagnik; Saha, Papita

    2011-06-01

    Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media.

  4. 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.

  5. 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.

  6. Synthesis and Spectroscopic Characterizations of an Insulinomimetic Peroxovanadate Complex in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    蔡淑惠; 于贤勇; 陈忠; 万惠霖

    2003-01-01

    The reaction system of diperoxooxalatovanadate {K3[ VO(O2)2·(C204)] ·H2O, bpV(Oxa)} and imidazole was studied in an aqueous solution by 1D multinudear (IH, DC and slY) NMR,2D NMR diffusion ordered spectroscopy (DOSY), and variable temperature NMR techniques. It was shown that DOSY was a useful tool for the study of a mixture. All of the 1H and 13C NMR signals of the peroxovanadate (V) complexes were assigned. The NMR experimental results indicated that a new complex was formed through the coordination interactions between bpV(Oxa) and imidazole. The newly-formed complex is stable under the experimental condition. Electrospray ionization mass spectrometry (ESI-MS) provides positive evidence to support the conclusion.

  7. First Observation of Electron Transfer Mediated Decay in Aqueous Solutions: A Novel Probe of Ion Pairing

    CERN Document Server

    Unger, I; Thürmer, S; Aziz, E F; Cederbaum, L S; Muchová, E; Slavíček, P; Winter, B; Kryzhevoi, N V

    2016-01-01

    A major goal of many spectroscopic techniques is to provide comprehensive information on the local chemical environment. Electron transfer mediated decay (ETMD) is a sensitive probe of the environment since it is actively involved in this non-local radiationless decay process through electron and energy transfer steps. We report the first experimental observation of ETMD in the liquid phase. Using liquid-jet X-ray photoelectron spectroscopy we explore LiCl aqueous solution, and detect low-energy electrons unambiguously emerging from the ETMD processes of core-ionized Li+. We interpret the experimental results with molecular dynamics and high-level ab initio calculations. By considering various solvation-structure models we show that both water molecules and Cl- anions can participate in ETMD, with each process having its characteristic spectral fingerprint. Different ion associations lead to different spectral shapes. The potential application of the unique sensitivity of the ETMD spectroscopy to the local hy...

  8. Class B Fire-Extinguishing Performance Evaluation of a Compressed Air Foam System at Different Air-to-Aqueous Foam Solution Mixing Ratios

    Directory of Open Access Journals (Sweden)

    Dong-Ho Rie

    2016-06-01

    Full Text Available The purpose of this research is to evaluate the fire-extinguishing performance of a compressed air foam system at different mixing ratios of pressurized air. In this system, compressed air is injected into an aqueous solution of foam and then discharged. The experimental device uses an exclusive fire-extinguishing technology with compressed air foam that is produced based on the Canada National Laboratory and UL (Underwriters Laboratories 162 standards, with a 20-unit oil fire model (Class B applied as the fire extinguisher. Compressed air is injected through the air mixture, and results with different air-to-aqueous solution foam ratios of 1:4, 1:7, and 1:10 are studied. In addition, comparison experiments between synthetic surfactant foam and a foam type which forms an aqueous film are carried out at an air-to-aqueous solution foam ratio of 1:4. From the experimental results, at identical discharging flows, it was found that the fire-extinguishing effect of the aqueous film-forming foam is greatest at an air-to-aqueous solution foam ratio of 1:7 and weakest at 1:10. Moreover, the fire-extinguishing effect of the aqueous film-forming foam in the comparison experiments between the aqueous film-forming foam and the synthetic surfactant foam is greatest.

  9. 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.

  10. 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

  11. Near-infrared transmission spectroscopy of aqueous solutions: The influence of optical pathlength on signal-to-noise ratio

    DEFF Research Database (Denmark)

    Jensen, P.S.; Bak, J.

    2002-01-01

    The optimal choice of optical pathlength, source intensity, and detector for near-infrared transmission measurements of trace components in aqueous solutions depends on the strong absorption of water. In this study we examine under which experimental circumstances one may increase the pathlength...... to obtain a measurement with higher signal-to-noise ratio. The noise level of measurements at eight different pathlengths from 0.2 to 2.0 mm of pure water and of 1 g/dL aqueous glucose signals were measured using a Fourier transform near-infrared spectrometer and a variable pathlength transmission cell...

  12. 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.

  13. Enthalpy of solution of CO{sub 2} in aqueous solutions of methyldiethanolamine at T = 322.5 K and pressure up to 5 MPa

    Energy Technology Data Exchange (ETDEWEB)

    Arcis, Hugues; Rodier, Laurence; Ballerat-Busserolles, Karine [Thermodynamique et Interactions Moleculaires, FRE3099, Universite Blaise Pascal Clermont-Ferrand / CNRS, 63177 Aubiere (France); Coxam, Jean-Yves [Thermodynamique et Interactions Moleculaires, FRE3099, Universite Blaise Pascal Clermont-Ferrand / CNRS, 63177 Aubiere (France)], E-mail: j-yves.coxam@univ-bpclermont.fr

    2008-06-15

    Enthalpies of solution of CO{sub 2} in aqueous solution of methyldiethanolamine (MDEA) are determined for two different concentrations, respectively, 15 wt% and 30 wt%, at the temperature of 322.5 K and at pressures up to 5 MPa using a flow calorimetric technique. Gas solubilities were consequently deduced from the calorimetric data and compared to available literature values. Experimental enthalpies of solution were compared to direct measurements and to values derived from VLE data available using a simple model based on ideal property considerations.

  14. Modeling of (vapor + liquid) equilibrium and enthalpy of solution of carbon dioxide (CO{sub 2}) in aqueous methyldiethanolamine (MDEA) solutions

    Energy Technology Data Exchange (ETDEWEB)

    Arcis, Hugues; Rodier, Laurence; Ballerat-Busserolles, Karine [Thermodynamique et Interactions Moleculaires, FRE3099, Universite Blaise Pascal Clermont-Ferrand, CNRS, 24 av. des Landais, 63177 Aubiere (France); Coxam, Jean-Yves [Thermodynamique et Interactions Moleculaires, FRE3099, Universite Blaise Pascal Clermont-Ferrand, CNRS, 24 av. des Landais, 63177 Aubiere (France)], E-mail: j-yves.coxam@univ-bpclermont.fr

    2009-06-15

    A thermodynamic model was used to estimate enthalpy of solution of carbon dioxide (CO{sub 2}) in methyldiethanolamine (MDEA) aqueous solutions. The model was based on a set of equations for chemical equilibria, phase equilibria, charge, and mass balances. Non-ideality in the liquid phase was taken into account by interaction parameters fitted to (vapor + liquid) equilibrium data. The enthalpies of solution of CO{sub 2} were derived from the model using classical thermodynamic relations and were compared to experimental values obtained in previous works.

  15. Free energetics of carbon nanotube association in pure and aqueous ionic solutions.

    Science.gov (United States)

    Ou, Shuching; Patel, Sandeep; Bauer, Brad A

    2012-07-19

    Carbon nanotubes are a promising platform across a broad spectrum of applications ranging from separations technology, drug delivery, to bio(electronic) sensors. Proper dispersion of carbon nanotube materials is important to retaining the electronic properties of nanotubes. Experimentally it has been shown that salts can regulate the dispersing properties of CNTs in aqueous system with surfactants (Niyogi, S.; Densmore, C. G.; Doorn, S. K. J. Am. Chem. Soc.2009, 131, 1144-1153); details of the physicochemical mechanisms underlying such effects continue to be explored. We address the effects of inorganic monovalent salts (NaCl and NaI) on dispersion stability of carbon nanotubes.We perform all-atom molecular dynamics simulations using nonpolarizable interaction models to compute the potential of mean force between two (10,10) single-walled carbon nanotubes (SWNTs) in the presence of NaCl/NaI and compare to the potential of mean force between SWNTs in pure water. Addition of salts enhances stability of the contact state between two SWNT's on the order of 4 kcal/mol. The ion-specific spatial distribution of different halide anions gives rise to starkly different contributions to the free energy stability of nanotubes in the contact state. Iodide anion directly stabilizes the contact state to a much greater extent than chloride anion. The enhanced stability arises from the locally repulsive forces imposed on nanotubes by the surface-segregated iodide anion. Within the time scale of our simulations, both NaI and NaCl solutions stabilize the contact state by equivalent amounts. The marginally higher stability for contact state in salt solutions recapitulates results for small hydrophobic solutes in NaCl solutions (Athawale, M. V.; Sarupria, S.; Garde, S. J. Phys. Chem. B2008, 112, 5661-5670) as well as single-walled carbon nanotubes in NaCl and CaCl2 aqueous solutions.

  16. 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.

  17. 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.

  18. Sonochemical Decolorization of Methyl Orange in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

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

    2006-01-01

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

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

    Directory of Open Access Journals (Sweden)

    R. Parimalam

    2012-01-01

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

  20. 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.

  1. Proton hydration in aqueous solution: Fourier transform infrared studies of HDO spectra

    Science.gov (United States)

    Śmiechowski, Maciej; Stangret, Janusz

    2006-11-01

    This paper attempts to elucidate the number and nature of the hydration spheres around the proton in an aqueous solution. This phenomenon was studied in aqueous solutions of selected acids by means of Fourier transform infrared spectroscopy of semiheavy water (HDO), isotopically diluted in H2O. The quantitative version of difference spectrum procedure was applied for the first time to investigate such systems. It allowed removal of bulk water contribution and separation of the spectra of solute-affected HDO. The obtained spectral data were confronted with ab initio calculated structures of small gas-phase and polarizable continuum model (PCM) solvated aqueous clusters, H+(H2O)n, n =2-8, in order to help in establishing the structural and energetic states of the consecutive hydration spheres of the hydrated proton. This was achieved by comparison of the calculated optimal geometries with the interatomic distances derived from HDO band positions. The structure of proton hydration shells outside the first hydration sphere essentially follows the model structure of other hydrated cations, previously revealed by affected HDO spectra. The first hydration sphere complex in diluted aqueous solutions was identified as an asymmetric variant of the regular Zundel cation [The Hydrogen Bond: Recent Developments in Theory and Experiments, edited by P. Schuster, G. Zundel, and C. Sandorfy (North-Holland, Amsterdam, 1976), Vol. II, p. 683], intermediate between the ideal Zundel and Eigen structures [E. Wicke et al., Z. Phys. Chem. Neue Folge 1, 340 (1954)]. Evidence was found for the existence of strong and short hydrogen bonds, with oxygen-oxygen distance derived from the experimental affected spectra equal 2.435Å on average and in the PCM calculations about 2.41-2.44Å. It was also evidenced for the first time that the proton possesses four well-defined hydration spheres, which were characterized in terms of hydrogen bonds' lengths and arrangements. Additionally, an outer

  2. STUDIES ON REVERSE OSMOSIS SEPARATION OF AQUEOUS ORGANIC SOLUTIONS BY PAA/PSF COMPOSITE MEMBRANE

    Institute of Scientific and Technical Information of China (English)

    Jun Fang; De-min Jia; Ji-cai Huang; Qun-hui Guo; Feng-lian Wu

    2000-01-01

    The reverse osmosis (RO) separation of aqueous organic solutions, such as alcohols, amines, aldehydes, acids,ketones, and esters etc., by PAA (polyacrylic acid)/PSF (polysulfone) composite membrane has been studied. It was found that the separation results for aliphatic alcohols, amines and aldehydes are satisfactory, the solute rejection (Ra) and the volume fluxes of solutions (Jr) for 1000 ppm ethanol, ethylamine and ethyl aldehyde are 66.2%, 61.0%, 84.0% and 0.90×alcohols, amines and aldehydes, and the Ra for n-amyl alcohol, n-butylamine and n-butyl aldehyde reached 94.3%, 88.6%and 96.0%, respectively. Satisfactory separation results (Ra>70%) for ketones, esters, phenols and polyols have been obtained with the PAA/PSF composite membrane. The effect of operating pressure on the properties of reverse osmosis has also been investigated. Analysis of experimental data with Spiegler-Kedem's transport model has been carried out and the membrane constants such as reflection coefficient σ, solute and hydraulic permeabilities ω and Lp for several organic solutes have been obtained.

  3. Physicochemical Properties of Amino Acids in Aqueous Caffeine Solution at 25, 30, 35 and 40 ℃

    Institute of Scientific and Technical Information of China (English)

    ALI A.; SABIR S.; SHAHJAHAN; HYDER S.

    2006-01-01

    Density, viscosity, and refractive index, for glycine, DL-alanine, L-serine and DL-valine have been determined in aqueous solution of 0.05 mol/kg caffeine as a function of amino acid (AA) concentration at 25, 30, 35, and 40 ℃.The density data have been used to compute apparent molar volume. The partial molar volume (limiting apparent molar volume) was obtained by applying the Masson's equation. The viscosity data have been analyzed by means of Jones-Dole equation. The values of Falkenhagen coefficient and Jones-Dole coefficient thus obtained are used to interpret the solute-solute and solute-solvent interactions, respectively. Hydration number was also computed. The transition-state theory was applied to obtain the activation parameters of viscous flow, I.e., free energy of activation per mole of solvent, and solute. The enthalpy and entropy of activation of viscous flow were computed for the system. Refractive index was used to calculate molar refractivity of the mixtures. The results have been interpreted in the lightof various interactions occurring between the components of the mixtures under applied experimental conditions.

  4. The behavior and toxicity of metal oxide nanoparticles in aqueous solution

    Science.gov (United States)

    Mwaanga, Phenny

    The dissolution and aggregation of metal oxides nanoparticles (NPs) in aqueous solution not only alter the abundance and toxicology of NPs, but also makes the effective assessment and the correct interpretation of effects of NPs on organisms challenging. The extent to which these processes (dissolution and aggregation) occur largely depend on pH, ionic strength, dissolved natural organic matter (NOM) and NPs characteristics. This study investigated the dissolution and aggregation behavior of the four metal oxide NPs (nZnO, nCuO, nFe2O3 and nTiO2) in aqueous solution as influenced by pH, ionic strength and NOM and examined the toxicity of these NPs to Daphnia magna and interpreted the toxicity in terms of NPs' behavior in aqueous solution. The dissolution of NPs in distilled and dionized (DDI) water, culture (FETAX) solution, solutions of varying pH, ionic strength and NOM content was investigated. Differences in the dissolution patterns in different solution conditions were observed among the NPs, with some NPs (nTiO2.) showing low dissolution under all solution conditions. Visual Minteq model showed that the distribution of dissolved metal oxides NPs species was regulated by pH and NOM. The experimental dissolution data were corroborated by Visual Minteq and by the empirical double exponent dissolution rate model. In the aggregation investigation, the aggregation behavior and fractal dimensions of the metal oxides NPs were studied in solutions such as DDI, FETAX solution, solutions of varying pH, ionic strength and NOM content. The rate of aggregation was found to increase with ionic strength and to decrease with increase in NOM concentration. Increased aggregation corresponded to lower fractal dimensions and increased sedimentation. Arising from the dissolution and aggregation investigations, the interaction of NOM with NPs in aqueous solution was examined. Specifically, the influence of the NOM on NPs dispersion at different pH values was investigated using TiO2

  5. Biosorption of hexavalent chromium from aqueous solutions by Macadamia nutshell powder

    Science.gov (United States)

    Pakade, Vusumzi Emmanuel; Ntuli, Themba Dominic; Ofomaja, Augustine Enakpodia

    2016-04-01

    Macadamia nutshell biosorbents treated in three different activating agents [raw Macadamia nutshell powder (RMN), acid-treated Macadamia nutshell (ATMN) and base-treated Macadamia nutshell (BTMN)] were investigated for the adsorption of hexavalent chromium [Cr(VI)] from aqueous solutions. Fourier transform infrared spectroscopy spectra of free and Cr(VI)-loaded sorbents as well as thermogravimetric analysis revealed that the acid and base treatments modified the surface properties of the sorbent. Surface characteristics were also evaluated by the scanning electron microscopy and surface area analyzer. The optimum conditions for the adsorption of Cr(VI) by sorbents were pH 2, contact time 10 h, adsorbent mass 0.2 g and concentration 100 mg L-1. The equilibrium data were fitted into the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms, and no single model could clearly explain the sorption mechanism. Maximum binding capacities of 45.23, 44.83 and 42.44 mg g-1 for RMN, ATMN and BTMN, respectively, were obtained. The kinetic data were analyzed using the pseudo-first, pseudo-second and Elovich kinetic models, and it was observed that the pseudo-second-order model produced the best fit for the experimental data. Macadamia nutshell sorbents showed potential as low-cost adsorbent for the removal of Cr(VI) from aqueous solution.

  6. Removal of Pb (II from Aqueous Solutions Using Waste Tea Leaves

    Directory of Open Access Journals (Sweden)

    Mehrdad Cheraghi

    2015-03-01

    Full Text Available Background: The presence of lead in natural waters has become an important issue around the world. Lead has been identified as a highly toxic metal that can cause severe environmental and public health problems and its decontamination is of utmost importance. The aim of this work was to evaluate the adsorption of lead (Pb(II on waste tea leaves as a cheap purification method. Methods: In this experimental study, prepared waste tea leaves were used as adsorbent for the removal of Pb (II from aqueous solutions. Adsorption experiments were carried out as batch studies at different contact time, pH, amount of adsorbent, initial metal concentration and temperature. Results: The results showed that maximum removal efficiency was observed at pH 6. Also the adsorption of Pb (II ions increased with decreasing initial metal concentration. The Langmuir isotherm model fits well with the equilibrium adsorption isotherm data and its calculated maximum monolayer adsorption capacity was 166.6 mg g-1 at a temperature of 25±0.1˚C. The kinetic data obtained have been analyzed using pseudo-first-order and pseudo-second-order models. The best fitted kinetic model was found to be pseudo-second-order. Conclusion: The results suggest that tea wastes could be employed as cheap material for the removal of lead from aqueous solutions.

  7. [Removal of Sulfate Ions from Aqueous Solution by Adsorption with Hydrotalcite- like Composite].

    Science.gov (United States)

    Gu, Yi-bing; Ma, Yong-wen; Wan, Jin-quan; Wang, Yan; Guan, Ze-yu

    2016-03-15

    Hydrotalcite-like composite synthesized by co-precipitation method was used as an adsorbent to remove the sulfate ions in aqueous solution. XRD, FT-IR , SEM and EDS elemental analysis were used to clarify the structure and composition of the hydrotalcite- like composite. The influences of time, initial pH value and coexisting ions on adsorption performance were investigated. The result showed the material was the composite of zinc aluminum nitrate hydrotalcite-like compounds and zinc aluminum phenylalanine hydrotalcite-like compounds. Hydrotalcite-like composite had a good performance in adsorption of sulfate ions, and the maximum adsorption capacity was 52.75 mg · g⁻¹. The data fitted pseudo-second order kinetic model best, which indicated that chemical adsorption was the rate-limiting step. Freundlich isotherm was more suitable to describe the adsorption process, and this meant the adsorption of sulfate ions by hydrotalcite-like composite was multilayered adsorption. Thermodynamic parameters showed that the adsorption process was endothermic and spontaneous at room temperature. Hydrotalcite-like composite adsorbed sulfate ions mainly through ion exchange, electrostatic force and physical adsorption. The experimental results showed that the hydrotalcite-like composite had potential for sulfate ion removal in the aqueous solution.

  8. A new alternative adsorbent for the removal of cationic dyes from aqueous solution

    Directory of Open Access Journals (Sweden)

    T. Santhi

    2016-09-01

    Full Text Available Adsorption of Malachite green (MG and Methylene blue (MB from aqueous solutions on low cost adsorbent prepared from Annona squmosa seed (CAS is studied experimentally. Results obtained indicate that the removal efficiency of Malachite green and Methylene blue at 27 ± 2 °C exceeds 75.66% and 24.33% respectively, and that the adsorption process is highly pH-dependent. Results showed that the optimum pH for dye removal is 6.0. The amount of dye adsorbed from aqueous solution increases with the increase of the initial dye concentration. Smaller adsorbent particle adds to increase the percentage removal of Malachite green and Methylene blue. The equilibrium data fitted well to the Langmuir model (R2 > 0.97 and the adsorption kinetic followed the pseudo-second-order equation (R2 > 0.99. The maximum adsorption capacities of MG, MB on CAS are 25.91 mg g−1 and 08.52 mg g−1 respectively. These results suggest that A. squmosa seed is a potential low-cost adsorbent for the dye removal from industrial wastewater. The adsorption capacity of CAS on MG is greater than MB.

  9. Removal of Pb(II) from aqueous solution by oxidized multiwalled carbon nanotubes.

    Science.gov (United States)

    Xu, Di; Tan, Xiaoli; Chen, Changlun; Wang, Xiangke

    2008-06-15

    Oxidized multiwalled carbon nanotubes (MWCNTs) were employed as sorbent to study the sorption characteristic of Pb(II) from aqueous solution as a function of contact time, pH, ionic strength, foreign ions, and oxidized MWCNTs' contents under ambient conditions using batch technique. The results indicate that sorption of Pb(II) on oxidized MWCNTs is strongly dependent on pH values, and independent of ionic strength and the type of foreign ions. The removal of Pb(II) to oxidized MWCNTs is rather quickly and the kinetic sorption can be described by a pseudo-second-order model very well. Sorption of Pb(II) is mainly dominated by surface complexation rather than ion exchange. The efficient removal of Pb(II) from aqueous solution is limited at pH 7-10. X-ray photoelectron spectroscopy (XPS) is performed to study the sorption mechanism at a molecular level and thereby to identify the species of the sorption processes. The 3-D relationship of pH, Ceq and q indicates that all the data of Ceq-q lie in a straight line with slope -V/m and intercept C0V/m for the same initial concentration of Pb(II) and same content of oxidized MWCNTs of each experimental data.

  10. Removal of lead(II) from aqueous solutions using carbonate hydroxyapatite extracted from eggshell waste.

    Science.gov (United States)

    Liao, Dexiang; Zheng, Wei; Li, Xiaoming; Yang, Qi; Yue, Xiu; Guo, Liang; Zeng, Guangming

    2010-05-15

    Carbonate hydroxyapatite (CHAP) synthesized from eggshell waste was used for removing lead ion from aqueous solutions. The effects of pH, contact time and initial concentration were studied in batch experiments. The maximum uptake of lead ion was obtained at pH 6.0. Adsorption equilibrium was established by 60 min. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models were applied to study the kinetics of the sorption processes. The pseudo-second order kinetic model provided the best correlation (R(2)>0.9991) of the used experimental data compared to the pseudo-first order and intraparticle diffusion kinetic models. The adsorption of lead ion by CHAP increased as the initial concentration of lead ion increased in the medium. The maximum lead ion adsorbed was found to be 101 mg g(-1). It was found that the adsorption of Pb(II) on CHAP was correlated well (R(2)=0.9995) with the Langmuir equation as compared to Freundlich isotherm equation under the concentration range studied. This study indicated that CHAP could be used as an efficient adsorbent for removal of lead ion from aqueous solution.

  11. Removal of BTEX from aqueous solution using Moringa oleifera seed cake.

    Science.gov (United States)

    Almeida, Ione L Silva; Antoniosi Filho, Nelson R; Alves, Maria I Ribeiro; Carvalho, Brenda G; Coelho, Nivia M Melo

    2012-06-01

    In this study, the removal of BTEX (benzene, toluene, ethylbenzene, p-xylene and o-xylene) from aqueous solution using Moringa oleifera seed cake (MOSC) was investigated. The effect of parameters such as contact time, pH and initial BTEX concentration were studied to optimize the conditions for maximum removal. Maximum removal values of 75 +/- 1%, 85 +/- 2%, 86 +/- 2%, 88 +/- 2% and 87 +/- 1% were obtained for benzene, toluene, ethylbenzene, p-xylene and o-xylene, respectively, at pH 7.0, with a 20 min contact time for an adsorbent dose of 10 g L(-1) of 1 mg L(-1) BTEX concentration. The adsorption data fitted the Langmuir and Freundlich adsorption isotherms. The capacity of MOSC to adsorb BTEX was compared with that for a commercial activated carbon. The results from the two methods were not significantly different (judged by t-test at 95% confident interval). A low cost, easy purchase and the satisfactory experimental results indicated that MOSC is a promising natural material for the removal of BTEX from aqueous solution.

  12. Influence of concentration on the radiolytic decomposition of thiamine, riboflavin, and pyridoxine in aqueous solution

    Directory of Open Access Journals (Sweden)

    Guadalupe Albarrán

    2014-10-01

    Full Text Available Vitamin loss during irradiation has been claimed as a critical area in food irradiation technology, especially that of thiamine (B1, which has been considered as the most sensitive to radiation. Although it has been suggested that no vitamin deficiency could result from consuming irradiated food, a long debate on the loss of vitamins and other nutrients during food irradiation has been maintained by the lack of experimental studies monitoring decomposition rates at different concentrations and doses. Since thiamine, riboflavin, and pyridoxine are labile vitamins, this study has focused on their radiolytic decomposition in dilute aqueous solutions in the presence of air. The decomposition process was followed by HPLC and UV-spectroscopy. The results obtained in aqueous solutions showed a dependence of the decomposition as a nonlinear function of the dose. Of these three compounds, the decomposition was higher for thiamine than for riboflavin and even less in pyridoxine.

  13. The Zeta Potential of Surface-Functionalized Metallic Nanorod Particles in Aqueous Solution

    Energy Technology Data Exchange (ETDEWEB)

    Dougherty, G M; Rose, K A; Tok, J B; Pannu, S S; Chuang, F S; Sha, M Y; Chakarova, G; Penn, S G

    2007-05-07

    Metallic nanoparticles suspended in aqueous solutions, and functionalized with chemical and biological surface coatings, are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. In this paper we describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11-mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self-assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. Zeta potential data for typical charge-stabilized polystyrene particles are also presented for comparison. Experimental data are compared with theory. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.

  14. An Exact Method to Determine the Conductivity of Aqueous Solutions in Acid-Base Titrations

    Directory of Open Access Journals (Sweden)

    Norma Rodríguez-Laguna

    2015-01-01

    Full Text Available Several works in the literature show that it is possible to establish the analytic equations to estimate the volume V of a strong base or a strong acid (Vb and Va, resp. being added to a solution of a substance or a mix of substances during an acid-base titration, as well as the equations to estimate the first derivative of the titration plot dpH/dV, and algebraic expressions to determine the buffer β capacity with dilution βdil. This treatment allows establishing the conditions of thermodynamic equilibria for all species within a system containing a mix of species from one or from various polyacid systems. The present work shows that it is possible to determine exactly the electric conductivity of aqueous solutions for these Brønsted acid-base titrations, because the functional relation between this property and the composition of the system in equilibrium is well known; this is achieved using the equivalent conductivity λi values of each of the ions present in a given system. The model employed for the present work confirms the experimental outcomes with the H2SO4, B(OH3, CH3COOH, and H3PO4 aqueous solutions’ titration.

  15. [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.

  16. The removal of phenol from aqueous solutions by adsorption using surfactant-modified bentonite and kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Alkaram, Uday F.; Mukhlis, Abduljabar A. [Department of Chemistry, College of Education, Ibn Al-Haitham, University of Baghdad, Baghdad (Iraq); Al-Dujaili, Ammar H., E-mail: ahdujaili@yahoo.com [Department of Chemistry, College of Education, Ibn Al-Haitham, University of Baghdad, Baghdad (Iraq)

    2009-09-30

    The natural bentonite (BC) and kaolinite (KC) were modified with two surfactant of hexadecyltrimethylammonium bromide (HDTMA) and phenyltrimethylammonium bromide (PTMA) to form four kinds of organic-modified clays, i.e., HDTMA-bentonite (BHM), HDTMA-kaolinite (KHM), PTMA-bentonite (KPM) and PTMA-kaolinite (KPM). The modified minerals were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and FT-IR spectroscopy. The surface areas were determined using methylene blue adsorption method. Cation-exchange capacity (CEC) was estimated using an ethylenediamine complex of copper method and the modifier loading was calculated from the total carbon analysis. The ability of raw and organo-modified clays to remove phenol from aqueous solutions has been carried out as a function of contact time, pH and temperatures using a batch technique. The removal of phenol from aqueous solutions by modified clays seems to be more effective than unmodified samples. The adsorption capacity was found to increase with increasing temperature indication that the adsorptions were endothermic. The adsorption of phenol onto these clays was found to be increased by increasing of pH value and the adsorption patterns data are correlated well by Langmuir and Freundlich isotherm models and that the adsorption is physical in nature. The experimental data fitted very well with the pseudo-second-order kinetic model. The thermodynamic study of adsorption process showed that the adsorption of phenol with these six adsorbents was carried out spontaneously, and the process was endothermic in nature.

  17. 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.

  18. 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.

  19. 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.

  20. Preparation and Characterization of Palmitoyl Grafted Cellulose Nano Absorbent for the Efficient Adsorption of Pyrene from Aqueous Solution.

    Science.gov (United States)

    Jadhav, Arvind H; Mai, Xuan Thang; Appiah-Ntiamoah, Richard; Lee, Hanyeong; Momade, Francis W Y; Seo, Jeong Gil; Kim, Hern

    2015-10-01

    Palmitoyl grafted modified cellulose were prepared by simple chemical grafting method and applied as nano adsorbent for removal of pyrene from aqueous solution. The chemical properties and morphology of prepared nano-adsorbent were characterized by FT-IR, XRD, SEM, EDX, TGA, and contact angle. Results showed that palmitoyl successfully grafted on the surface of cellulose and possess effective organic functional groups for the adsorption of pyrene from aqueous solution. The adsorption performance of modified cellulose was significantly improved toward pyrene in aqueous solution. It is worthy to note that 0.25 g of palmitoyl grafted cellulose (PMC) removed 92% pyrene compared to unmodified cellulose which adsorbed 36% pyrene from 1.65 ppm aqueous solution of pyrene in very short contact time at room temperature. Results showed that, presence of various organic functional groups from palmitoyl chains grafted on cellulose backbone affected to pyrene removal. After completion of adsorption phenomenon nano-adsorbent can be removed by simply filtration process and reused several times. The adsorption capacity was studied under different experimental conditions and their effects on adsorption such as temperature, pH, and contact time were also studied. The kinetics and isotherms of material were also determined.

  1. 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

  2. [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.

  3. Pseudomorphic replacement of diopside during interaction with (Ni,Mg)Cl2 aqueous solutions : Implications for the Ni-enrichment mechanism in talc- and serpentine-type phases

    NARCIS (Netherlands)

    Majumdar, Alik S.; King, Helen E.; John, Timm; Kusebauch, Christof; Putnis, Andrew

    2014-01-01

    A hydrothermal experimental study of diopside interaction with (Ni,Mg)Cl2 aqueous solutions has been carried out to clarify the replacement mechanism and pattern of element mobilization and its relevance to peridotite alteration. Three different solution compositions were used with Ni/Mg ratios of 0

  4. Calcite precipitation from aqueous solution: transformation from vaterite and role of solution stoichiometry

    NARCIS (Netherlands)

    Nehrke, G.

    2007-01-01

    The morphology of vaterite precipitated by bubbling CO2 through a CaCl2 solution is framboidal aggregates. It is not possible, even when using the identical experimental setup and conditions, to reproduce aggregates having identical morphology. The density of the aggregates and crystallite size can

  5. 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.

  6. 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.

  7. A simple physical model for steam absorption into a falling film of aqueous lithium bromide solution on a horizontal tube

    Science.gov (United States)

    Auracher, Hein; Wohlfeil, Arnold; Ziegler, Felix

    2008-03-01

    For one horizontal tube in an absorber the Nusselt solution for film thickness and velocity distribution was applied, assuming steady state in heat transfer and a semi-infinite body’s concentration profile with unsteady state mass transfer. The model was applied to the absorption of steam into aqueous lithium bromide in absorption chillers. The results are compared to published experimental values and show fair agreement.

  8. COMPARATIVE EVALUATION OF COMMERCIAL AND SEWAGE SLUDGE BASED ACTIVATED CARBONS FOR THE REMOVAL OF TEXTILE DYES FROM AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    S. Sreedhar Reddy, B. Kotaiah

    2006-10-01

    Full Text Available The sorption of dyes from aqueous solutions on to sludge-based activated carbon have been studied and compared with commercial activated carbon. Adsorption parameters for the Langmuir and Freundlich isotherms were determined and the effects of effluent pH, adsorbent dosage, contact time and initial dye concentration were studied. A pseudo-second order kinetic model has been proposed to correlate the experimental data.

  9. Application of adsorption process by activated carbon derived from scrap tires for Pb+2 removal from aqueous solutions

    OpenAIRE

    Edris Hoseinzadeh; Ali Reza Rahmani; Ghorban Asgari; Mohamad Taghi Samadi; Ghodratollah Roshanaei; Mohammad Reza Zare

    2013-01-01

    Background and Aim: Heavy metals have been recognized as very poisonous elements and their discharge into water sources can cause damaging effects on human and environmental health. The present study aimed at producing activated carbon from scrap tires and using it in removing Pb+2 from synthetic aqueous solutions. Materials and Methods: In this experimental study, activated carbon powder was derived from scrap tires under laboratory conditions. The effect of Pb (II) ions wi...

  10. Chemical Bonding in Aqueous Ferrocyanide: Experimental and Theoretical X-ray Spectroscopic Study

    CERN Document Server

    Engel, Nicholas; Suljoti, Edlira; Garcia-Diez, Raul; Lange, Kathrin M; Atak, Kaan; Golnak, Ronny; Kothe, Alexander; Dantz, Marcus; Kühn, Oliver; Aziz, Emad F

    2013-01-01

    Resonant inelastic X-ray scattering (RIXS) and X-ray absorption (XA) experiments at the iron L- and nitrogen K-edge are combined with high-level first principles restricted active space self-consistent field (RASSCF) calculations for a systematic investigation of the nature of the chemical bond in potassium ferrocyanide in aqueous solution. The atom- and site-specific RIXS excitations allow for direct observation of ligand-to-metal (Fe L-edge) and metal-to-ligand (N K-edge) charge transfer bands and thereby evidence for strong {\\sigma}-donation and {\\pi}-back-donation. The effects are identified by comparing experimental and simulated spectra related to both the unoccupied and occupied molecular orbitals in solution.

  11. Biosorption of Methyl Blue Onto Tartaric Acid Modified Wheat Bran From Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Shuhua Yao

    2012-12-01

    Full Text Available Tartaric acid modified wheat bran was utilized as adsorbent to remove methyl blue, a basic dye from aqueous solution. Batch experiments were carried out to study the effect of various experimental parameters such as initial solution pH, contact time, initial dye concentration and adsorbent dosage, on dye adsorption. The results showed that the modification of wheat bran by tartaric acid significantly improved its adsorption capacity, and made thismaterial a suitable adsorbent to remove 1.6 times higher than that of unmodified one. The amount of methyl blue adsorbed was found to vary with initial solution pH, adsorbent dosage, contact time and initial methyl blue concentration. Kinetics study showed that theoverall adsorption rate of methyl blue was illustrated by pseudo-second-order kinetic model. The applicability of theLangmuir and Freundlich models for the data was tested. Both models adequately described the experimental data of the biosorption of methyl blue. The maximum adsorption capacity for methyl blue calculated from Langmuir model was 25.18 mg/g. The study has shown the effectiveness of modified wheat bran in the removal of methylblue, and that it can be considered as an attractive alternative to the more expensive technologies used in wastewater treatment.

  12. Mercury adsorption on granular activated carbon in aqueous solutions containing nitrates and chlorides.

    Science.gov (United States)

    Di Natale, F; Erto, A; Lancia, A; Musmarra, D

    2011-09-15

    Adsorption is an effective process to remove mercury from polluted waters. In spite of the great number of experiments on this subject, the assessment of the optimal working conditions for industrial processes is suffering the lack of reliable models to describe the main adsorption mechanisms. This paper presents a critical analysis of mercury adsorption on an activated carbon, based on the use of chemical speciation analysis to find out correlations between mercury adsorption and concentration of dissolved species. To support this analysis, a comprehensive experimental study on mercury adsorption at different mercury concentrations, temperatures and pH was carried out in model aqueous solutions. This study pointed out that mercury capture occurs mainly through adsorption of cationic species, the adsorption of anions being significant only for basic pH. Furthermore, it was shown that HgOH(+) and Hg(2+) are captured to a higher extent than HgCl(+), but their adsorption is more sensitive to solution pH. Tests on the effect of temperature in a range from 10 to 55 °C showed a peculiar non-monotonic trend for mercury solution containing chlorides. The chemical speciation and the assumption of adsorption exothermicity allow describing this experimental finding without considering the occurrence of different adsorption mechanisms at different temperature.

  13. Effect of adsorbents and chemical treatments on the removal of strontium from aqueous solutions.

    Science.gov (United States)

    Ahmadpour, A; Zabihi, M; Tahmasbi, M; Bastami, T Rohani

    2010-10-15

    In the present investigation, three different solid wastes namely almond green hull, eggplant hull, and moss were initially treated and used as adsorbents for the adsorption of strontium ion from aqueous solutions. Adsorbent types and chemical treatments are proved to have effective roles on the adsorption of Sr(II) ion. Among the three adsorbents, almond green hull demonstrated strong affinity toward strontium ion in different solutions. The effectiveness of this new adsorbent was studied in batch adsorption mode under a variety of experimental conditions such as: different chemical treatments, various amounts of adsorbent, and initial metal-ion concentration. The optimum doses of adsorbent for the maximum Sr(II) adsorption were found to be 0.2 and 0.3 g for 45 and 102 mg L(-1) solutions, respectively. High Sr(II) adsorption efficiencies were achieved only in the first 3 min of adsorbent's contact time. The kinetics of Sr(II) adsorption on almond green hull was also examined and it was observed that it follows the pseudo second-order behavior. Both Langmuir and Freundlich models well predicted the experimental adsorption isotherm data. The maximum adsorption capacity on almond green hull was found to be 116.3 mg g(-1). The present study also confirmed that these low cost agriculture byproducts could be used as efficient adsorbents for the removal of strontium from wastewater streams.

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

    Directory of Open Access Journals (Sweden)

    Ingrid Johanna Puentes-Cárdenas

    2016-01-01

    Full Text Available 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 adsorption kinetics showed good agreement of experimental data with the pseudo-second-order kinetics model. The experimental equilibrium data for AB80 adsorption were evaluated for compliance with different two-parameter, three-parameter, and four-parameter isotherm models. The Langmuir isotherm model best described the AB80 adsorption equilibrium data. The thermodynamic data revealed that the AB80 adsorption process was endothermic and nonspontaneous. Kinetics, equilibrium, and thermodynamic results indicate that Cu-TiO2 adsorbs AB80 by a chemical sorption reaction.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-02-11

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

  16. 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.

  17. 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.

  18. BIOSORPTION STUDIES OF CADMIUM (II IONS FROM AQUEOUS SOLUTIONS ONTO ORANGE RIND (CITRUS SINENSIS L. OSBECK

    Directory of Open Access Journals (Sweden)

    Satish A. Bhalerao

    2015-03-01

    Full Text Available The biosorption studies for effective removal of cadmium (II ions from aqueous solutions using orange rind (Citrus sinensis L. Osbeck, cost effective biosorbent, was carried out in batch system. FTIR analysis of biosorbent confirmed that carboxyl, hydroxyl, carbonyl group which was responsible for biosorption of cadmium (II ions. The SEM represents porous structure with surface area. The effects of operational factors including solution pH, biosorbent dose, initial cadmium (II ions concentration, contact time and temperature were studied. The optimum solution pH for cadmium (II ions biosorption by biosorbent was 7.0 with the optimal removal 80.30 %. The biosorbent dose 5 mg/ml was enough for optimal removal of 65.15 %. The biosorption process was relatively fast and equilibrium was achieved after 90 minutes of contact. The experimental equilibrium biosorption data were analysed by four widely used two-parameters Langmuir, Freundlich, Dubinin-Kaganer-Redushkevich (DKR and Temkin isotherm models. Langmuir isotherm model provided a better fit with the experimental data than Freundlich, Temkin and Dubinin-Kaganer-Redushkevich (DKR isotherm models by high correlation coefficient value (R2 = 0.911. The maximum adsorption capacity determined from Langmuir isotherm was found to be 83.33 mg/g of biosorbent. Simple kinetic models such as pseudo-first-order, pseudo-second-order, Elovich equation and Weber and Morris intra-particle diffusion rate equation were employed to determine the adsorption mechanism. Results clearly indicates that the pseudo-second-order kinetic model (R2 = 0.998 was found to be correlate the experimental data strongest than other three kinetic models and this suggests that chemical adsorption process was more dominant. Thermodynamic study revealed that the biosorption process was spontaneous, endothermic and increasing randomness of the solid solution interfaces. Orange rind (Citrus sinensis L. Osbeck was successfully used for the

  19. Optimized atomistic force fields for aqueous solutions of Magnesium and Calcium Chloride: Analysis, achievements and limitations

    Science.gov (United States)

    Elfgen, Roman; Hülsmann, Marco; Krämer, Andreas; Köddermann, Thorsten; Kirschner, Karl N.; Reith, Dirk

    2016-10-01

    Molecular simulations are an important tool in the study of aqueous salt solutions. To predict the physical properties accurately and reliably, the molecular models must be tailored to reproduce experimental data. In this work, a combination of recent global and local optimization tools is used to derive force fields for MgCl2 (aq) and CaCl2 (aq). The molecular models for the ions are based on a Lennard-Jones (LJ) potential with a superimposed point charge. The LJ parameters are adjusted to reproduce the bulk density and shear viscosity of the different solutions at 1 bar and temperatures of 293.15, 303.15, and 318.15 K. It is shown that the σ-value of chloride consistently has the strongest influence on the system properties. The optimized force field for MgCl2 (aq) provides both properties in good agreement with the experimental data over a wide range of salt concentrations. For CaCl2 (aq), a compromise was made between the bulk density and shear viscosity, since reproducing the two properties requires two different choices of the LJ parameters. This is demonstrated by studying metamodels of the simulated data, which are generated to visualize the correlation between the parameters and observables by using projection plots. Consequently, in order to derive a transferable force field, an error of ˜3% on the bulk density has to be tolerated to yield the shear viscosity in satisfactory agreement with experimental data.

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

    Institute of Scientific and Technical Information of China (English)

    伍艳辉; 谭惠芬; 李佟茗; 金源

    2012-01-01

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

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

    NARCIS (Netherlands)

    Haas, C; Drenth, J; Wilson, WW

    1999-01-01

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

  2. Melting of the precipitated ice IV in LiCl aqueous solution and polyamorphism of water.

    Science.gov (United States)

    Mishima, Osamu

    2011-12-08

    Melting of the precipitated ice IV in supercooled LiCl-H(2)O solution was studied in the range of 0-0.6 MPa and 160-270 K. Emulsified solution was used to detect this metastable transition. Ice IV was precipitated from the aqueous solution of 2.0 mol % LiCl (or 4.8 mol % LiCl) in each emulsion particle at low-temperature and high-pressure conditions, and the emulsion was decompressed at different temperatures. The melting of ice IV was detected from the temperature change of the emulsified sample during the decompression. There was an apparently sudden change in the slope of the ice IV melting curve (liquidus) in the pressure-temperature diagram. At the high-pressure and high-temperature side of the change, the solute-induced freezing point depression was observed. At the low-pressure and low-temperature side, ice IV transformed into ice Ih on the decompression, and the transition was almost unrelated to the concentration of LiCl. These experimental results were roughly explained by the presumed existence of two kinds of liquid water (low-density liquid water and high-density liquid water), or polyamorphism in water, and by the simple assumption that LiCl dissolved maily in high-density liquid water.

  3. Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

    Science.gov (United States)

    Morrison, Benjamin C.; Borrero-Echeverry, Daniel

    2015-11-01

    Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH4SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water (ν ~ 1 . 6 cSt and ρ ~ 1 . 1 g/cc). We present an empirical model for predicting the refractive index of aqueous NH4SCN solutions as a function of temperature and NH4SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. This work was supported by the National Science Foundation (CBET-0853691) and by the James Borders Physics Student Fellowship at Reed College.

  4. 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.

  5. 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.)

  6. 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.)

  7. 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.

  8. Degradation of atrazine by microwave-assisted electrodeless discharge mercury lamp in aqueous solution.

    Science.gov (United States)

    Ta, Na; Hong, Jun; Liu, Tingfeng; Sun, Cheng

    2006-11-02

    The present study investigates the degradation of atrazine (2-chloro-4-(ethyl amino)-6-isopropyl amino-s-triazine) in aqueous solution by a developed new method, namely by means of a microwave-assisted electrodeless discharge mercury lamp (MW-EDML). An experimental design was conducted to assess the influence of various parameters: pH value, initial concentration, amount of EDML, initial volume and coexisted solvent. Atrazine was degraded completely by EDML in a relatively short time (i.e. t(1/2)=1.2 min for 10 mg/l). Additionally, the identification of main degradation products during atrazine degradation process was conducted by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). This study proposes the degradation mechanism including four possible pathways for atrazine degradation according to the degradation products.

  9. Probing ion-specific effects on aqueous acetate solutions: Ion pairing versus water structure modifications

    Directory of Open Access Journals (Sweden)

    Tristan Petit

    2014-05-01

    Full Text Available The effect of monovalent cations (Li+, K+, NH4+, Na+ on the water structure in aqueous chloride and acetate solutions was characterized by oxygen K-edge X-ray absorption spectroscopy (XAS, X-ray emission spectroscopy, and resonant inelastic X-ray scattering (RIXS of a liquid microjet. We show ion- and counterion dependent effects on the emission spectra of the oxygen K-edge, which we attribute to modifications of the hydrogen bond network of water. For acetates, ion pairing with carboxylates was also probed selectively by XAS and RIXS. We correlate our experimental results to speciation data and to the salting-out properties of the cations.

  10. Malachite green "a cationic dye" and its removal from aqueous solution by adsorption

    Science.gov (United States)

    Raval, Nirav P.; Shah, Prapti U.; Shah, Nisha K.

    2016-12-01

    Adsorption can be efficiently employed for the removal of various toxic dyes from water and wastewater. In this article, the authors reviewed variety of adsorbents used by various researchers for the removal of malachite green (MG) dye from an aqueous environment. The main motto of this review article was to assemble the scattered available information of adsorbents used for the removal of MG to enlighten their wide potential. In addition to this, various optimal experimental conditions (solution pH, equilibrium contact time, amount of adsorbent and temperature) as well as adsorption isotherms, kinetics and thermodynamics data of different adsorbents towards MG were also analyzed and tabulated. Finally, it was concluded that the agricultural solid wastes and biosorbents such as biopolymers and biomass adsorbents have demonstrated outstanding adsorption capabilities for removal of MG dye.

  11. EFFECT OF HYPERCROSSLINKED RESINS SURFACE CHEMISTRY ON THEADSORPTION OF PHENOL FROM AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Guan-hua Meng; Ai-min Lia; Wei-ben Yang; Fu-qiang Liu; Quan-xing Zhang

    2006-01-01

    Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate.

  12. Photocatalytic decomposition of humic acids in anoxic aqueous solutions producing hydrogen, oxygen and light hydrocarbons.

    Science.gov (United States)

    Klauson, Deniss; Budarnaja, Olga; Beltran, Ignacio Castellanos; Krichevskaya, Marina; Preis, Sergei

    2014-01-01

    Photocatalytic water splitting for hydrogen and oxygen production requires sacrificial electron donors, for example, organic compounds. Titanium dioxide catalysts doped with platinum, cobalt, tungsten, copper and iron were experimentally tested for the production of hydrogen, oxygen and low molecular weight hydrocarbons from aqueous solutions of humic substances (HS). Platinum-doped catalyst showed the best results in hydrogen generation, also producing methane, ethene and ethane, whereas the best oxygen production was exhibited by P25, followed by copper--and cobalt-containing photocatalysts. Iron-containing photocatalyst produced carbon monoxide as a major product. HS undergoing anoxic photocatalytic degradation produce hydrogen with minor hydrocarbons, and/or oxygen. It appears that better hydrogen yield is achieved when direct HS splitting takes place, as opposed to HS acting as electron donors for water splitting.

  13. Molar extinction coefficients of some carbohydrates in aqueous solutions

    Indian Academy of Sciences (India)

    K Singh; G K Sandhu; B S Lark; S P Sud

    2002-03-01

    Molar extinction coefficients of some carbohydrates viz. L-arabinose (C5H10O5), D-glucose (C6H12O6), D-mannose (C6H12O6), D-galactose (C6H12O6), D(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer–Lambert law is obeyed very well.

  14. Geosorption of As(III) from aqueous solution by red clays: kinetic studies.

    Science.gov (United States)

    Rivera-Hernández, José R; Green-Ruiz, Carlos

    2014-05-01

    The geosorption of As(III) on red clays from aqueous solution under different environmental conditions (i.e. initial concentration, pH and temperature) was studied. This process reached its equilibrium quickly (clays at 0.1 mg As(III) L(-1) was 10, while for 10 mg As(III) L(-1) was 4. There wasn't a significant effect of temperature on the As(III) adsorption. The kinetic pseudo-second order and the isothermal Langmuir were the models that best described the experimental data, suggesting an adsorption process in multistep. Likewise, there are not interactions between neighbor active sites on the red clay surface.

  15. Surface heterogeneity effects of activated carbons on the kinetics of paracetamol removal from aqueous solution

    Science.gov (United States)

    Ruiz, B.; Cabrita, I.; Mestre, A. S.; Parra, J. B.; Pires, J.; Carvalho, A. P.; Ania, C. O.

    2010-06-01

    The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules.

  16. Removal of copper ions from aqueous solution by calcium alginate immobilized kaolin

    Institute of Scientific and Technical Information of China (English)

    Yanhui Li; Yanzhi Xia; Bing Xia; Quansheng Zhao; Fuqiang Liu; Pan Zhang; Qiuju Du; Dechang Wang; Da Li; Zonghua Wang

    2011-01-01

    Kaolin has been widely used as an adsorbent to remove heavy metal ions from aqueous solutions. However, the lower heavy metal adsorption capacity of kaolin limits its practical application. A novel environmental friendly material, calcium alginate immobilized kaolin (kaolin/CA), was prepared using a sol-gel method. The effects of contact time, pH, adsorbent dose, and temperature on Cu2+ adsorption by kaolin/CA were investigated. The Langmuir isotherm was used to describe the experimental adsorption, the maximum Cu2+ adsorption capacity of the kaolin/CA reached up to 53.63 mg/g. The thermodynamic studies showed that the adsorption reaction was a spontaneous and endothermic process.

  17. Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder.

    Science.gov (United States)

    Ghaemi, Ahad; Torab-Mostaedi, Meisam; Ghannadi-Maragheh, Mohammad

    2011-06-15

    In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic.

  18. Removal of Ni (II) from aqueous solutions by adsorption onto Ricinus communis seed shell activated carbons.

    Science.gov (United States)

    Thamilarasu, P; Karunakaran, K

    2011-01-01

    The adsorption studies on the removal of Ni(II) from aqueous solution using Ricinus communis seed shells activated carbon and polypyrrole coated Ricinus communis seed shells activated carbon were carried out under various experimental conditions. The effects of various process parameters have been investigated by following the batch adsorption technique. Adsorption data was modeled with Freundlich, Langmuir and tempkin adsorption isotherms. Thermodynamics parameters such as DeltaH0, DeltaS0, and DeltaG0 were calculated indicating that the adsorption was spontaneous and endothermic nature. A mechanism, involving intra particle diffusion and surface adsorption, has been proposed for the adsorption of Ni(II) onto the adsorbent. Adsorbent used in this study is characterized by FTIR and SEM before and after the adsorption of metal ions.

  19. Application of Polyaniline Nano Composite for the Adsorption of Acid Dye from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    J.Raffiea Baseri

    2012-01-01

    Full Text Available In this research, Polyaniline coated sawdust (Polyaniline nano composite was synthesized via direct chemical polymerization and used as an adsorbent for the removal of acid dye (Acid Violet 49 from aqueous solutions. The effect of some important parameters such as pH, initial concentration of dye, contact time and temperature on the removal efficiency was investigated in batch adsorption system. The adsorption capacity of PAC was high (96.84 % at a pH of 3-4. The experimental data fitted well for pseudo second order model. Langmuir model is more appropriate to explain the nature of adsorption with high correlation coefficient. The Energy of activation from arrehenius plot suggested that the adsorption of AV49 onto PAC involves physisorption mechanism.

  20. A multistate empirical valence bond model for solvation and transport simulations of OH- in aqueous solutions.

    Science.gov (United States)

    Ufimtsev, Ivan S; Kalinichev, Andrey G; Martinez, Todd J; Kirkpatrick, R James

    2009-11-07

    We describe a new multistate empirical valence bond (MS-EVB) model of OH(-) in aqueous solutions. This model is based on the recently proposed "charged ring" parameterization for the intermolecular interaction of hydroxyl ion with water [Ufimtsev, et al., Chem. Phys. Lett., 2007, 442, 128] and is suitable for classical molecular simulations of OH(-) solvation and transport. The model reproduces the hydration structure of OH(-)(aq) in good agreement with experimental data and the results of ab initio molecular dynamics simulations. It also accurately captures the major structural, energetic, and dynamic aspects of the proton transfer processes involving OH(-) (aq). The model predicts an approximately two-fold increase of the OH(-) mobility due to proton exchange reactions.

  1. Foam separation of chromium (Ⅵ) from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    JIAO Cai-shan; DING Yan

    2009-01-01

    Removal of chromium (Ⅵ) dissolved in water by intermittent foam separation was implemented with cetyl trimethy-ammonium bromide as surfactant. The influence of various factors on removal efficiency was systematically studied. The removal efficiency has a maximum value near pH 4.0; thus, most experiments were carried out at pH 4.0. The orthogonal experiment was conducted to confirm the optimal operating parameters. The orthogonal experimental results show that when the liquid feed concentration is 10 mg/L, the pH value of feed solution is 4.00, air flow rates 0.9 L/min, surfactant dosage is 300 mg/L, the maximum removal efficiency of chromium (Ⅵ) reaches 97.80%, and condense multiple reaches 1711. The kinetic test indicates that the foam separation of chromium is a first-order process. The equivalent rate constant calculated from the slope is 0.406 4, and the equivalent rate equation is obtained.

  2. The efficiency of magnetic carbon activated by iron oxide nanoparticles in removing of Cu (II from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Salehe Salehnia

    2016-04-01

    Full Text Available Background and Aim: Copper ions, due to forming complexes with organic and mineral compounds, can have worrying effects on health and environment. In the present study, the effect of powdered magnetic carbon activated by iron-oxide nanoparticles in removing of CU (V; II from aqueous solutions was assessed. Materials and Methods: This experimental study aimed at determining the effect of powdered magnetic carbon activated  by iron-oxide nanoparticles  parameters including PH, contact time, absorbing dose, and initial concentration on copper(II removal .from aqueous solutions; through an indirect current. In order to assess the qualities of the synthetized adsorbent, TGA, FT-IR and SEM tests were applied. Residual concentration of copper was measured at 324nm wavelength by means of atomic absorption spectrometry flame. The obtained data was analyzed using Langmuir and Freundlich isotherm model. Result: It was found that synthetic nanoparticles(PH=10, with the adsorbent dosage of 1gr/l, can remove more than 96% of copper ions from aqueous solutions at 2 minutes. Also, the results showed that copper absorption pattern is more in accord with Langmuir model.  Conclusion: Based on the current findings , magnetic synthesized nanoparticles coated with carbon. are in sporadic form in aqueous solutions. and can easily be separated using external magnetic environment. Moreover, because of existant active carbon sites absorption in iron oxide structure suferficial absorbtion capacity increases and and these nanoparticles reveal to have a high performance in the removing process of copper pollutants from aqueous solutions.

  3. Molecular Modeling and Monte Carlo Simulation of Concentrated Aqueous Alkali Halide Solutions at 25 C.

    Science.gov (United States)

    Llano-Restrepo, Mario Andres

    A study of concentrated aqueous alkali halide solutions is made at the molecular level, through modeling and computer simulation of their structural and thermodynamic properties. It is found that the HNC approximation is the best integral equation theory to predict such properties within the framework of the primitive model (PM). The intrinsic limitations of the PM in describing ionic association and hydration effects are addressed and discussed in order to emphasize the need for explicitly including the water molecules in the treatment of aqueous electrolyte solutions by means of a civilized model (CM). As a step toward developing a CM as simple as possible, it is shown that a modified version of the SPC model of liquid water in which the Lennard-Jones interaction between intermolecular oxygen sites is replaced by a hard core interaction, is still successful enough to predict the degree of hydrogen bonding of real water. A simple civilized model (SCM) (in which the ions are treated as hard spheres interacting through Coulombic potentials and the water molecules are simulated using the simplified SPC model) is introduced in order to study the changes in the structural features of various aqueous alkali halide solutions upon varying both the concentration and the size of the ions. Both cations and anions are found to be solvated by the water molecules at expense of a breakdown in the hydrogen-bonded water network. Hydration numbers are reported for the first time for NaBr and KBr, and the first simulation -based estimates for LiBr, NaI and KI are also obtained. In several cases, values of the hydration numbers based on the SCM are found to be in excellent agreement with available experimental results obtained from x-ray diffraction measurements. Finally, it is shown that a neoprimitive model (NPM) can be developed by incorporating some of the structural features seen in the SCM into the short-range part of the PM interionic potential via a shielded square well whose

  4. Effect of temperature on the dilution enthalpies of {alpha},{omega}-amino acids in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Romero, C.M., E-mail: cmromeroi@unal.edu.co [Departamento de Quimica, Facultad de Ciencias, Universidad Nacional de Colombia, Bogota (Colombia); Cadena, J.C., E-mail: jccadena@unal.edu.co [Departamento de Quimica, Facultad de Ciencias, Universidad Nacional de Colombia, Bogota (Colombia); Lamprecht, I., E-mail: ingolf.lamprecht@t-online.de [Institut fuer Biologie, Freie Universitaet Berlin, Berlin (Germany)

    2011-10-15

    Highlights: > The dilution of 3-amino propanoic acid, 4-amino butanoic acid, 5-amino pentanoic acid, and 6-amino hexanoic acid in water is an exothermic process at T = (293.15, 298.15, 303.15, and 308.15) K. > The limiting experimental slopes of the enthalpies of dilution with respect to the molality change {Delta}m, are negative suggesting that the solutes interact with water primarily through their alkyl groups. > The value of the pairwise coefficient is positive at the temperatures considered, and the magnitude increases linearly with the number of methylene groups. > The comparison between the pairwise interaction coefficients for {alpha},{omega}-amino acids and {alpha}-amino acids shows that the change in the enthalpic interaction coefficient is related to the relative position of the polar groups. - Abstract: Dilution enthalpies of aqueous solutions of 3-amino propanoic acid, 4-amino butanoic acid, 5-amino pentanoic acid, and 6-amino hexanoic acid were determined at T = (293.15, 298.15, 303.15, and 308.15) K using an LKB flow microcalorimeter. The homotactic interaction coefficients were obtained according to the McMillan-Mayer theory from the experimental data. For all the systems studied, the dilution of {alpha},{omega}-amino acids in water is an exothermic process; the pair coefficients have positive values which increases with chain length. The obtained values of the interaction coefficients are interpreted in terms of solute-solvent and solute-solute interactions and are used as indicative of hydrophobic behavior of the amino acid studied.

  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. Using Tunisian Phosphate Rock and Her Converted Hydroxyapatite for Lead Removal from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Hassen Bachoua

    2014-07-01

    Full Text Available Natural and synthesis apatites represent a cost effective soil amendment, which can be used for in situ reduction of lead bioavailability and mobility. In our previous work, we selected Tunisian Phosphate Rock (TPR and Hydroxyapatite (CaHAp as promising minerals for the removal of lead from aqueous solutions. X-ray powder diffraction patterns (DRX, Infra Red (IR, Thermogravimetric analysis (TGA and Scanning Electron Microscopy (SEM were used to characterize TPR and CaHAp. CaHAp was prepared from TPR and employed for the removal of Pb2+ ions at different concentrations from aqueous solution to determine the adsorption properties of CaHAp and compare them with those of a TPR. The kinetic data obtained indicated that the adsorption performances of the adsorbents depended both on their specific surface area and crystallinity. Complexation of lead ion on the adsorbent surface favoured the dissolution of hydroxyapatites characterized by a Ca/Pb molar ratio of 1.69. The maximum adsorption capacity of CaHAp for Pb2+ ions at 25 °C was 1.806 mmol /g relative to 1.035 mmol /g for TPR at the same temperature. The higher capacity of CaHAp was explained in terms of its porosity and crystallinity. The Pb2+ ions sorption results could be modelled by the Langmuir and Freundlich isotherms. The simulations of adsorption isotherms of Pb2+ on CaHAp allow us to conclude that there is a good correlation between the experimental data and the Langmuir model. On TPR, we show a good correlation between the experimental data and the Langmuir and Freundlich model.

  7. Application of artificial neural network (ANN in Biosorption modeling of Chromium (VI from aqueous solutions

    Directory of Open Access Journals (Sweden)

    F Mohammadi

    2016-03-01

    Full Text Available Background and Objectives: In this work, biosorption of hexavalent chromium from aqueous solution with excess municipal sludge was studied. Moreover, the performance of neural networks to predict the biosorption rate was investigated. Materials and Methods: The effect of operational parameters including initial metal concentration, initial pH, agitation speed, adsorbent dosage, and agitation time on the biosorption of chromium was assessed in a batch system. A part of the experimental results was modeled using Feed-Forward Back propagation Neural Network (FFBP-ANN. Another part of the test results was simulated to assess the model accuracy. Transfer function in the hidden layers and output layers and the number of neurons in the hidden layers were optimized. Results: The maximum removal of chromium obtained from batch studies was more than 96% in 90 mg/L initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/L. Maximum biosorption capacity was 41.69 mg/g. Biosorption data of Cr(VI are described well by Freundlich isotherm model and adsorption kinetic followed pseudo-second order model.  Tangent sigmoid function determined was the most appropriate transfer function in the hidden and output layer. The optimal number of neurons in hidden layers was 13. Predictions of model showed excellent correlation (R=0.984 with the target vector. Simulations performed by the developed neural network model showed good agreement with experimental results. Conclusion: Overall, it can be concluded that excess municipal sludge performs well for the removal of Cr ions from aqueous solution as a biological and low cost biosorbent. FFBP-ANN is an appropriate technique for modeling, estimating, and prediction of biosorption process If the Levenberg-Marquardt training function, tangent sigmoid transfer function in the hidden and output layers and the number of neurons is between 1.6 to 1.8 times the input data, proper predication results could be

  8. Interfacial behavior of perchlorate versus chloride ions in saturated aqueous salt solutions

    Energy Technology Data Exchange (ETDEWEB)

    Ghosal, S; Kuo, I W; Baer, M D; Bluhm, H

    2009-04-14

    In recent years combination of theoretical and experimental work have presented a novel view of the aqueous interface wherein hard and/or multiply charged ions are excluded from the interface, but large polarizable anions show interfacial enhancement relative to the bulk. The observed trend in the propensity of anions to adsorb at the air/water interface appears to be reverse of the Hofmeister series for anions. This study focuses on experimental and theoretical examination of the partitioning behavior of perchlorate (ClO{sub 4}{sup -}) and chloride (Cl{sup -}) ions at the air/water interface. We have used ambient pressure X-ray photoelectron spectroscopy technique to directly probe the interfacial concentrations of ClO{sub 4}{sup -} and Cl{sup -} ions in sodium perchlorate and sodium chloride solutions, respectively. Experimental observations are compared with first principles molecular dynamics simulations. Both experimental and simulation results show enhancement of ClO{sub 4}{sup -} ion at the interface, compared with the absence of such enhancement in the case of Cl{sup -} ion. These observations are in agreement with the expected trend in the interfacial propensity of anions based on the Hofmeister series.

  9. 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.

  10. 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.

  11. Adsorption of Cu2+ Ions From Aqueous Solutions Using Oxidized Multi-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Soheil Sobhanardakani

    2015-06-01

    Full Text Available Copper ion (Cu2+ is one of the heavy metal ions that cause environmental pollution specifically in water. Copper ion cations are not biodegradable and tend to cumulate in living organisms. Consequently, the removal of Cu2+ in environmental samples plays an important role in environmental pollution monitoring. The purpose of the present work was to prepare oxidized Multi-Walled Carbon Nano Tubes (MWCNTs for removal of Cu2+ ions from aqueous solutions. This study was conducted under laboratory conditions. Multi-Walled Carbon Nano Tubes were oxidized and characterized by Fourier Transform Infrared Spectroscopy (FTIR, Scanning Electron Microscope (SEM and the Brunauer, Emmett, and Teller (BET methods. The effects of various factors, such as solution pH (3 - 9, adsorbent dose (0.006 - 0.06 g and contact time (10 - 120 minutes were investigated. Results showed that the suitable pH for Cu2+ ions removal was about 6.0, and the optimal dose was 0.03 g. Isotherm studies indicated that the Langmuir model fits the experimental data better than the Freundlich model. Maximum Cu2+ adsorption capacity was calculated as 200 mg g-1. The kinetics of the adsorption process was tested for the pseudo-first-order and pseudo-second-order models. The comparison among the models showed that the pseudo-second order model best described the adsorption kinetics. The results showed that oxidized MWCNTs can be used as a low cost adsorbent for the removal of Cu2+ ions from aqueous solutions.

  12. 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.

  13. 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.

  14. Immobilization of Rose Waste Biomass for Uptake of Pb(II) from Aqueous Solutions.

    Science.gov (United States)

    Ansari, Tariq Mahmood; Hanif, Muhammad Asif; Mahmood, Abida; Ijaz, Uzma; Khan, Muhammad Aslam; Nadeem, Raziya; Ali, Muhammad

    2011-01-01

    Rosa centifolia and Rosa gruss an teplitz distillation waste biomass was immobilized using sodium alginate for Pb(II) uptake from aqueous solutions under varied experimental conditions. The maximum Pb(II) adsorption occurred at pH 5. Immobilized rose waste biomasses were modified physically and chemically to enhance Pb(II) removal. The Langmuir sorption isotherm and pseudo-second-order kinetic models fitted well to the adsorption data of Pb(II) by immobilized Rosa centifolia and Rosa gruss an teplitz. The adsorbed metal is recovered by treating immobilized biomass with different chemical reagents (H(2)SO(4), HCl and H(3)PO(4)) and maximum Pb(II) recovered when treated with sulphuric acid (95.67%). The presence of cometals Na, Ca(II), Al(III), Cr(III), Cr(VI), and Cu(II), reduced Pb(II) adsorption on Rosa centifolia and Rosa gruss an teplitz waste biomass. It can be concluded from the results of the present study that rose waste can be effectively used for the uptake of Pb(II) from aqueous streams.

  15. 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.

  16. Use of iron oxide magnetic nanosorbents for Cr (VI removal from aqueous solutions: A review

    Directory of Open Access Journals (Sweden)

    Nirmala Ilankoon

    2014-10-01

    Full Text Available This review paper focuses on the use of iron oxide nanosorbents for the removal of hexavalent Chromium [Cr(VI], from aqueous media. Cr(VI is a well-known toxic heavy metal, which can cause severe damages to the human health even with the presence of trace levels. Chromium continuously enters into water streams from different sources. Several methods are available for Cr(VI removal and some of them are well established in industrial scale whilst some are still in laboratory scale. Reduction followed by chemical precipitation, adsorption, electro-kinetic remediation, membrane separation processes and bioremediation are some of the removal techniques. Each method is associated with both advantages and disadvantages. Currently, the use of nanosorbents for the aqueous chromium removal is popular among researchers and iron oxide nanoparticles are the most frequently used nanosorbents. This review paper summarizes the performance of different iron oxide nanosorbents studied on the last decade. The direct comparison of these results is difficult due to different experimental conditions used in each study. Adsorption isotherms and adsorption kinetics models are also discussed in this review paper. The effect of solution pH, temperature, initial Cr(VI concentration, adsorbent dosage and other coexisting ions are also briefly discussed. From the results it is evident that, more attention needs to be paid on the industrial application of the technologies which were successful in the laboratory scale.

  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. Dynamics of biological water: insights from molecular modeling of light scattering in aqueous trehalose solutions.

    Science.gov (United States)

    Lupi, Laura; Comez, Lucia; Paolantoni, Marco; Fioretto, Daniele; Ladanyi, Branka M

    2012-06-28

    Extended depolarized light scattering (EDLS) measurements have been recently employed to investigate the dynamics of water solvating biological molecules, giving evidence of the presence of two different dynamical regimes among water molecules. An interpretation of EDLS has been proposed that provides an independent estimate of the retardation factor of slowdown with respect to fast water molecules and of the number of solvent molecules affected by this slowing down. Nevertheless this measure is an inherently complex one, due to the collective nature of the physical property probed. In the present work a molecular dynamics (MD) approach has been used to more deeply understand experimental results. Time correlation functions of the collective polarizability anisotropy have been calculated for the prototype disaccharide trehalose in aqueous solutions as a function of concentration. The unique capability of MD to disentangle the contributions to the dynamics arising from solute, solvent, and cross terms between the two allowed us to check the reliability of an interpretation that assumes a spectral separation of water and sugar dynamics, as well as to highlight the very presence of two distinct relaxation processes in water. The two processes have been attributed to the dynamics of bulk and hydration water, respectively. A retardation factor of ~5 and concentration dependent hydration numbers have been observed, in good agreement with experimental results [Paolantoni, M.; et al. J. Phys. Chem. B 2009, 113, 7874-7878].

  19. Removal of arsenate and arsenite from aqueous solution by waste cast iron.

    Science.gov (United States)

    Choi, Nag-Choul; Kim, Song-Bae; Kim, Soon-Oh; Lee, Jae-Won; Park, Jun-Boum

    2012-01-01

    The removal of As(III) and As(V) from aqueous solution was investigated using waste cast iron, which is a byproduct of the iron casting process in foundries. Two types of waste cast iron were used in the experiment: grind precipitate dust (GPD) and cast iron shot (CIS). The X-ray diffraction analysis indicated the presence of Feo on GPD and CIS. Batch experiments were performed under different concentrations of As(III) and As(V) and at various initial pH levels. Results showed that waste cast iron was effective in the removal of arsenic. The adsorption isotherm study indicated that the Langmuir isotherm was better than the Freundlich isotherm at describing the experimental result. In the adsorption of both As(IH) and As(V), the adsorption capacity of GPD was greater than CIS, mainly due to the fact that GPD had higher surface area and weight percent of Fe than CIS. Results also indicated the removal of As(III) and As(V) by GPD and CIS was influenced by the initial solution pH, generally decreasing with increasing pH from 3.0 to 10.5. In addition, both GPD and CIS were more effective at the removal of As(III) than As(V) under given experimental conditions. This study demonstrates that waste cast iron has potential as a reactive material to treat wastewater and groundwater containing arsenic.

  20. Synthesis and characterization of polyaniline/zeolite nanocomposite for the removal of chromium(VI from aqueous solution

    Directory of Open Access Journals (Sweden)

    Abdulsalam A. Shyaa

    2015-01-01

    Batch adsorption experiments were used to investigate the effect of various experimental parameters on the equilibrium adsorption of chromium(VI on PANI/zeolite nanocomposite. The adsorption characteristics of the composite toward Cr(VI in dilute aqueous solution were followed spectrophotometrically. The effect of contact time, size of the sorbent and the concentration of Cr(VI in solution on the metal uptake behavior of the composite were studied. It has been observed that the capacity of chromium adsorption on PANI/zeolite increases with initial metal concentration, the metal ion adsorption on surfactant is well represented by the Freundlich isotherm.

  1. 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.

  2. A novel cloud-point extraction process for preconcentrating selected polycyclic aromatic hydrocarbons in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bai, D.; Li, J.; Chen, S.B.; Chen, B.-H. [National University of Singapore (Singapore). Dept. of Chemical and Environmental Engineering

    2001-10-01

    Polycyclic aromatic hydrocarbons (PAHs) released in such processes as incomplete coal combustion and during the disposal of coal tar, are subject to strict emission controls in which the determination of PAHs has to be addressed. PAHs have low aqueous solubility which necessitates preconcentration prior to the analytical determination of PAHs. A novel but simple cloud-point extraction (CPE) process is developed to preconcentrate the trace of selected polycyclic aromatic hydrocarbons (PAHs) with the use of the readily biodegradable nonionic surfactant of secondary ethyoxylated alcohol Tergitol 15-S-7 as extractant. The concentrations of PAHs, mixtures of naphthalene and phenanthrene as well as pyrene in the spiked samples were determined with the new CPE process at ambient temperature (23{degree}C) followed by high performance liquid chromatography (HPLC) with fluorescence detection. More than 80% of phenanthrene and pyrene, respectively, and 96% of naphthalene initially present in the aqueous solutions with concentrations near or below their aqueous solubilities were recovered using this new CPE process. Importantly Tergitol 15-S-7 does not give any fluorometric signal to interfere with fluorescence detection of PAHs in the UV range. No special washing step is, thus, required to remove surfactant before HPLC analyses. Different experimental conditions were studied. The optimum conditions for the preconcentration and determination of these selected PAHs at ambient temperature have been established as the following: (1) 3 wt% surfactant; (2) addition of 0.5 M Na{sub 2}SO{sub 4}; (3) 10 min for equilibration time; and (4) 3000 rpm for centrifugal speed with duration of 10 min. 50 refs., 7 figs.

  3. Removal of cobalt ions from aqueous solutions by polymer assisted ultrafiltration using experimental design approach: part 2: Optimization of hydrodynamic conditions for a crossflow ultrafiltration module with rotating part.

    Science.gov (United States)

    Cojocaru, Corneliu; Zakrzewska-Trznadel, Grazyna; Miskiewicz, Agnieszka

    2009-09-30

    Application of shear-enhanced crossflow ultrafiltration for separation of cobalt ions from synthetic wastewaters by prior complexation with polyethyleneimine has been investigated via experimental design approach. The hydrodynamic conditions in the module with tubular metallic membrane have been planned according to full factorial design in order to figure out the main and interaction effects of process factors upon permeate flux and cumulative flux decline. It has been noticed that the turbulent flow induced by rotation of inner cylinder in the module conducts to growth of permeate flux, normalized flux and membrane permeability as well as to decreasing of permeate flux decline. In addition, the rotation has led to self-cleaning effect as a result of the reduction of estimated polymer layer thickness on the membrane surface. The optimal hydrodynamic conditions in the module have been figured out by response surface methodology and overlap contour plot, being as follows: DeltaP=70 kPa, Q(R)=108 L/h and W=2800 rpm. In such conditions the maximal permeate flux and the minimal flux decline has been observed.

  4. Evaluation of adsorption of uranium from aqueous solution using biochar materials

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Wagner Clayton; Guilhen, Sabine Neusatz; Ortiz, Nilce; Fungaro, Denise Alves, E-mail: wcorrea@ipen.br, E-mail: snguilhen@ipen.br, E-mail: notriz@ipen.br, E-mail: dfungaro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Uranium is present in the environment as a result of leaching from natural deposits and activities associated with nuclear fuel, copper mining, uranium mining, milling industry, etc. For the purpose of protecting ecosystem stability and public health, it is crucial to eliminate uranium from aqueous solutions before they are discharged into the environment. Various technologies have been used for removing U(VI) ions from aqueous systems. Among these methods, adsorption has been applied in wastewater because of simple operation procedure and high removal efficiency. Brazil is the largest producer of charcoal in the world, with nearly half of the woody biomass harvested for energy in Brazil being transformed into charcoal. Biochar exhibits a great potential as an adsorbent because of favorable physical/chemical surface characteristics. The objective of this work was to evaluate the adsorption potential of biochar materials prepared from pyrolysis of Bamboo (CBM), Eucalyptus (CEM) and Macauba (CMA) nuts for the removal of uranium from solutions. Adsorption experiments were carried out by a batch technique. Equilibrium adsorption experiments were performed by shaking a known amount of biochar material with 100 mL of U(VI) solution in Erlenmeyer flasks in a shaker at 120 rpm and room temperature (25 deg C) for 24 h. The adsorbent was separated by centrifugation from the solution. The U(VI) concentration remaining in the supernatant solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The influences of different experimental parameters such as solution pH and bioadsorbent dose on adsorption were investigated. The highest uranium adsorption capacity were obtained at pH 3.0 and 16 g/L biomass dosage for CMA, pH 3.0 and 12 g/L biomass dosage for CBM and pH 2.0 and 10 g/L biomass dosage for CEM. The results demonstrated that the biomass derived char can be used as a low-cost adsorbent for removal of uranium from wastewater. (author)

  5. Effect of alkyl chain length and temperature on the thermodynamic properties of ionic liquids 1-alkyl-3-methylimidazolium bromide in aqueous and non-aqueous solutions at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, Rahmat [Department of Chemistry, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)], E-mail: rahsadeghi@yahoo.com; Shekaari, Hemayat [Department of Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Hosseini, Rahim [Department of Chemistry, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

    2009-02-15

    The alkyl chain length of 1-alkyl-3-methylimidazolium bromide ([Rmim][Br], R = propyl (C{sub 3}), hexyl (C{sub 6}), heptyl (C{sub 7}), and octyl (C{sub 8})) was varied to prepare a series of room-temperature ionic liquids (RTILs), and experimental measurements of density and speed of sound at different temperatures ranging from (288.15 to 308.15) K for their aqueous and methanolic solutions in the dilute concentration region (0.01 to 0.30) mol . kg{sup -1} were taken. The values of the compressibilities, expansivity and apparent molar properties for [C{sub n}mim][Br] in aqueous and methanolic solutions were determined at the investigated temperatures. The obtained apparent molar volumes and apparent molar isentropic compressibilities were fitted to the Redlich-Mayer and the Pitzer's equations from which the corresponding infinite dilution molar properties were obtained. The values of the infinite dilution molar properties were used to obtain some information about solute-solvent and solute-solute interactions. The thermodynamic properties of investigated ionic liquids in aqueous solutions have been compared with those in methanolic solutions. Also, the comparison between thermodynamic properties of investigated solutions and those of electrolyte solutions, polymer solutions, cationic surfactant solutions and tetraalkylammonium salt solutions have been made.

  6. Bioremediation of heavy metal contaminated aqueous solution by using red algae Porphyra leucosticta.

    Science.gov (United States)

    Ye, Jianjun; Xiao, Henglin; Xiao, Benlin; Xu, Weisheng; Gao, Linxia; Lin, Gan

    2015-01-01

    Bioremediation is an effective process for the removal and recovery of heavy metal ions from aqueous solutions. In this study, red algae Porphyra leucosticta was examined to remove Cd(II) and Pb(II) ions from wastewater through biological enrichment and biological precipitation. The experimental parameters that affect the bioremediation process such as pH, contact time and biomass dosage were studied. The maximum bioremediation capacity of metal ions was 31.45 mg/g for Cd(II) and 36.63 mg/g for Pb(II) at biomass dosage 15 g/L, pH 8.0 and contact time 120 minutes containing initial 10.0 mg/L of Cd(II) and 10.0 mg/L of Pb(II) solution. Red algae Porphyra leucosticta biomass was efficient at removing metal ions of 10.0 mg/L of Cd(II) and 10.0 mg/L of Pb(II) solution with bioremediation efficiency of 70% for Cd(II) and 90% for Pb(II) in optimal conditions. At the same time, the removal capacity for real industrial effluent was gained at 75% for 7.6 mg/L Cd(II) and 95% for 8.9 mg/L Pb(II). In conclusion, it is demonstrated that red algae Porphyra leucosticta is a promising, efficient, cheap and biodegradable sorbent biomaterial for reducing heavy metal pollution in the environment and wastewater.

  7. Removal of Pb(II) from aqueous solutions by graphene oxide aerogels.

    Science.gov (United States)

    Tabrizi, N S; Zamani, S

    2016-01-01

    This paper reports the application of graphene oxide aerogels (GOAs) for adsorption of lead(II) ions from aqueous solutions. The aerogels were fabricated from graphene oxide (GO) colloidal suspensions by unidirectional freeze drying method. The synthesized GO powders, as well as the aerogels, were thoroughly characterized by various techniques. The experimental data showed that the kinetic of adsorption followed a pseudo-second-order model with sharp lead(II) ions uptake within the first 90 min. Kinetic data analysis revealed that the adsorption process was controlled by film diffusion mechanism. The equilibrium data were best fitted to Langmuir model and the qmax was calculated to be as high as 158 mg/g. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and endothermic with increased randomness at the solid-liquid interface. Experiments showed that almost all the adsorbed ions could desorb into the solution only by decreasing the solution pH below the isoelectric point of the adsorbent. In addition to abundant oxygen containing functional groups existing on the surface of GO sheets, high porosity and surface area of the aerogel are believed to be influential factors in the adsorption process.

  8. Removal of heavy metal ions from aqueous solution using red loess as an adsorbent.

    Science.gov (United States)

    Xing, Shengtao; Zhao, Meiqing; Ma, Zichuan

    2011-01-01

    The adsorption behaviors of heavy metals onto novel low-cost adsorbent, red loess, were investigated. Red loess was characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectra. The results indicated that red loess mainly consisted of silicate, ferric and aluminum oxides. Solution pH, adsorbent dosage, initial metal concentration, contact time and temperature significantly influenced the efficiency of heavy metals removal. The adsorption reached equilibrium at 4 hr, and the experimental equilibrium data were fitted to Langmuir monolayer adsorption model. The adsorption of Cu(II) and Zn(II) onto red loess was endothermic, while the adsorption of Pb(II) was exothermic. The maximum adsorption capacities of red loess for Pb(II), Cu(II) and Zn(II) were estimated to be 113.6, 34.2 and 17.5 mg/g, respectively at 25 degrees C and pH 6. The maximum removal efficiencies were 100% for Pb(II) at pH 7, 100% for Cu(II) at pH 8, and 80% for Zn(II) at pH 8. The used adsorbents were readily regenerated using dilute HCl solution, indicating that red loess has a high reusability. All the above results demonstrated that red loess could be used as a possible alternative low-cost adsorbent for the removal of heavy metals from aqueous solution.

  9. Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

    Science.gov (United States)

    Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

    2015-02-11

    The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide.

  10. Adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite from aqueous solution.

    Science.gov (United States)

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

    2007-09-01

    The adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite (EP) from aqueous solution were investigated with respect to the changes in pH of solution, adsorbent dosage, contact time and temperature of solution. For the adsorption of both metal ions, the Langmuir isotherm model fitted to equilibrium data better than the Freundlich isotherm model. Using the Langmuir model equation, the monolayer adsorption capacity of EP was found to be 8.62 and 13.39 mg/g for Cu(II) and Pb(II) ions, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data and the mean free energies of adsorption were found as 10.82 kJ/mol for Cu(II) and 9.12 kJ/mol for Pb(II) indicating that the adsorption of both metal ions onto EP was taken place by chemical ion-exchange. Thermodynamic functions, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were also calculated for each metal ions. These parameters showed that the adsorption of Cu(II) and Pb(II) ions onto EP was feasible, spontaneous and exothermic at 20-50 degrees C. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for both metal ions followed well pseudo-second-order kinetics.

  11. Studies on adsorption of mercury from aqueous solution on activated carbons prepared from walnut shell.

    Science.gov (United States)

    Zabihi, M; Haghighi Asl, A; Ahmadpour, A

    2010-02-15

    The adsorption ability of a powdered activated carbons (PAC) derived from walnut shell was investigated in an attempt to produce more economic and effective sorbents for the control of Hg(II) ion from industrial liquid streams. Carbonaceous sorbents derived from local walnut shell, were prepared by chemical activation methods using ZnCl(2) as activating reagents. Adsorption of Hg(II) from aqueous solutions was carried out under different experimental conditions by varying treatment time, metal ion concentration, pH and solution temperature. It was shown that Hg(II) uptake decreases with increasing pH of the solution. The proper choice of preparation conditions were resulted in microporous activated carbons with different BET surface areas of 780 (Carbon A, 1:0.5 ZnCl(2)) and 803 (Carbon B, 1:1 ZnCl(2))m(2)/g BET surface area. The monolayer adsorption capacity of these particular adsorbents were obtained as 151.5 and 100.9 mg/g for carbons A and B, respectively. It was determined that Hg(II) adsorption follows both Langmuir and Freundlich isotherms as well as pseudo-second-order kinetics.

  12. Removal of sulfamethoxazole and ciprofloxacin from aqueous solutions by graphene oxide.

    Science.gov (United States)

    Chen, Hao; Gao, Bin; Li, Hui

    2015-01-23

    As a promising nanomaterial, graphene-oxide (GO) has shown great sorption potential for environmental contaminants. This study evaluated the ability and mechanism of GO to remove sulfamethoxazole (SMX) and ciprofloxacin (CIP) from aqueous solution. Experimental and modeling results showed that GO effectively sorbed both CIP and SMX with maximum sorption capacity of 379 and 240 mg g(-1), respectively. The sorption of CIP was mainly controlled by the electrostatic attractions; while SMX sorption was mainly though π-π EDA attraction on the basal planes of the GO. Solution pH showed strong effect on the sorption ability of GO to the two antibiotics: at pH of 2, GO sorption ability decreased for both CIP and SMX; at pH of 9, GO completely lost SMX sorption ability but still showed strong sorption to CIP. Both NaCl and CaCl2 decreased CIP sorption onto GO and CaCl2 showed high efficiency even at low ionic strength. The effect of NaCl and CaCl2 on SMX sorption was weaker, but higher ionic strength also reduced the sorption of SMX onto GO. At solution pH of 2, sorption of CIP destabilized GO suspension to form aggregates. Results obtained from this work demonstrated that GO can be used as an effective adsorbents to removal antibiotics from water.

  13. Graphene oxide as filter media to remove levofloxacin and lead from aqueous solution.

    Science.gov (United States)

    Dong, Shunan; Sun, Yuanyuan; Wu, Jichun; Wu, Benjun; Creamer, Anne Elise; Gao, Bin

    2016-05-01

    There is an increasing need to develop novel and high-efficiency water purification technologies. This work systematically evaluated the potential of using graphene oxide (GO) directly as filter media for the removal of levofloxacin (LEV), an emerging contaminate, and lead (Pb), a heavy metal, from aqueous solution. Batch and fixed-bed experiments were conducted to determine the sorption behaviors of LEV and Pb onto the GO. In the batch system, GO showed strong sorption of the two contaminants with Langmuir maximum adsorption capacities of 256.6 and 227.2 mg g(-1), respectively. The removal of LEV and Pb by GO in fixed-bed columns was high under all tested conditions in both single and mixed solution systems. The removal efficiency of the two contaminants in the GO-sand columns increased with increasing GO content, but decreased with increasing injection flow rate. In the mixed solution system, although LEV and Pb competed for sorption, the GO media still had high removal efficiencies for them. The column experimental data were well described by the Bed Depth Service Time (BDST) model, suggesting the model can be used for the design of GO-sand filters in large-scale applications. Findings from this work demonstrated that GO is a promising nano-adsorbent that can be used as a high-efficiency filter media in water treatment to remove hazardous metal elements and emerging contaminants.

  14. Removal of heavy metal ions from aqueous solution using red loess as an adsorbent

    Institute of Scientific and Technical Information of China (English)

    Shengtao Xing; Meiqing Zhao; Zichuan Ma

    2011-01-01

    The adsorption behaviors of heavy metals onto novel low-cost adsorbent,red loess,were investigated.Red loess was characterized by X-ray diffraction,scanning electron microscopy and Fourier transform infrared spectra.The results indicated that red loess mainly consisted of silicate,ferric and aluminum oxides.Solution pH,adsorbent dosage,initial metal concentration,contact time and temperature significantly influenced the efficiency of heavy metals removal.The adsorption reached equilibrium at 4 hr,and the experimental equilibrium data were fitted to Langmuir monolayer adsorption model.The adsorption of Cu(Ⅱ) and Zn(Ⅱ) onto red loess was endothermic,while the adsorption of Pb(Ⅱ) was exothermic.The maximum adsorption capacities of red loess for Pb(Ⅱ),Cu(Ⅱ)and Zn(Ⅱ) were estimated to be 113.6,34.2 and 17.5 mg/g,respectively at 25°C and pH 6.The maximum removal efficiencies were 100% for Pb(Ⅱ) at pH 7,100% for Cu(Ⅱ) at pH 8,and 80% for Zn(Ⅱ) at pH 8.The used adsorbents were readily regenerated using dilute HCI solution,indicating that red loess has a high reusability.All the above results demonstrated that red loess could be used as a possible alternative low-cost adsorbent for the removal of heavy metals from aqueous solution.

  15. [Degradation of nitrobenzene in aqueous solution by modified ceramic honeycomb-catalyzed ozonation].

    Science.gov (United States)

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

    2005-11-01

    Comparative experiments of modified ceramic honeycomb, ceramic honeycomb-catalyzed ozonation and ozonation alone were conducted with nitrobenzene as the model organic pollutant. It was found that the processes of modified ceramic honeycomb and ceramic honeycomb-catalyzed ozonation could increase the removal efficiency of nitrobenzene by 38.35% and 15.46%, respectively, compared with that achieved by ozonation alone. Under the conditions of this experiment, the degradation rate of modified ceramic honeycomb-catalyzed ozonation increased by 30.55% with the increase of amount of catalyst to 5 blocks. The degradation rate of three process all increased greatly with the increase of temperature and value of pH in the solution. But when raising the pH value of the solution to 10.00, the advantage of modified ceramic honeycomb-catalyzed ozonation processes lost. The experimental results indicate that in modified ceramic honeycomb-catalyzed ozonation, nitrobenzene is primarily oxidized by *OH free radical in aqueous solution. The adsorption of nitrobenzene is too limited to have any influence on the degradation efficiency of nitrobenzene. With the same total dosage of applied ozone, the multiple steps addition of ozone showed a much higher removal efficiency than that obtained by one step in three processes. Modified ceramic honeycomb had a relative longer lifetime.

  16. Fragile to strong crossover at the Widom line in supercooled aqueous solutions of NaCl

    Energy Technology Data Exchange (ETDEWEB)

    Gallo, P. [Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Rome, Italy and INFN, Sezione di Roma Tre, Via della Vasca Navale 84, I-00146 Rome (Italy); Corradini, D.; Rovere, M., E-mail: rovere@fis.uniroma3.it [Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Rome (Italy)

    2013-11-28

    We study by molecular dynamics simulations the dynamical properties of an aqueous solution of NaCl at a concentration of 0.67 mol/kg upon supercooling. In a previous study of the same ionic solution, we have located the liquid-liquid critical point (LLCP) and determined the Widom line connected to the liquid-liquid transition. We present here the results obtained from the study of the self-intermediate scattering function in a large range of temperatures and densities approaching the LLCP. The structural relaxation is in agreement with the mode coupling theory (MCT) in the region of mild supercooling. In the deeper supercooled region the α-relaxation time as function of temperature deviates from the MCT power law prediction showing a crossover from a fragile to a strong behavior. This crossover is found upon crossing the Widom line. The same trend was found in bulk water upon supercooling and it appears almost unchanged by the interaction with ions apart from a shift in the thermodynamic plane toward lower pressures and higher temperatures. These results show that the phenomenology of supercooled water transfers from bulk to solution where the study of the supercooled region is experimentally less difficult.

  17. Fragile to strong crossover at the Widom line in supercooled aqueous solutions of NaCl.

    Science.gov (United States)

    Gallo, P; Corradini, D; Rovere, M

    2013-11-28

    We study by molecular dynamics simulations the dynamical properties of an aqueous solution of NaCl at a concentration of 0.67 mol/kg upon supercooling. In a previous study of the same ionic solution, we have located the liquid-liquid critical point (LLCP) and determined the Widom line connected to the liquid-liquid transition. We present here the results obtained from the study of the self-intermediate scattering function in a large range of temperatures and densities approaching the LLCP. The structural relaxation is in agreement with the mode coupling theory (MCT) in the region of mild supercooling. In the deeper supercooled region the α-relaxation time as function of temperature deviates from the MCT power law prediction showing a crossover from a fragile to a strong behavior. This crossover is found upon crossing the Widom line. The same trend was found in bulk water upon supercooling and it appears almost unchanged by the interaction with ions apart from a shift in the thermodynamic plane toward lower pressures and higher temperatures. These results show that the phenomenology of supercooled water transfers from bulk to solution where the study of the supercooled region is experimentally less difficult.

  18. 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.

  19. Precipitation of Co(2+) carbonates from aqueous solution: insights on the amorphous to crystalline transformation.

    Science.gov (United States)

    González-López, Jorge; Fernández-González, Ángeles; Jiménez, Amalia

    2016-04-01

    Cobalt is toxic metal that is present only as a trace in the Earth crust. However, Co might concentrate on specific areas due to both natural and anthropogenic factors and thus, soils and groundwater can be contaminated. It is from this perspective that we are interested in the precipitation of cobalt carbonates, since co-precipitation with minerals phases is a well-known method for metal immobilization in the environment. In particular, the carbonates are widely used due to its reactivity and natural abundance. In order to evaluate the cobalt carbonate precipitation at room temperature, a simple experimental work was carried out in this work. The precipitation occurred via reaction of two common salts: 0.05M of CoCl2 and 0.05M of Na2CO3 in aqueous solution. After reaction, the precipitated solid was kept in the remaining water at 25 oC and under constant stirring for different aging times of 5 min, 1 and 5 hours, 1, 2, 4, 7, 30 and 60 days. In addition to the aging and precipitation experiments, we carried out experiments to determine the solubility of the solids. In these experiments each precipitate was dissolved in Milli-Q water until equilibrium was reached and then the aqueous solution was analyzed regarding Co2+ and total alkalinity. Furthermore, acid solution calorimetry of the products were attained. Finally, we modeled the results using the PHREEQC code. Solid and aqueous phase identification and characterization have been extensively reported in a previous work (González-López et al., 2015). The main results of our investigation were the initial precipitation of an amorphous cobalt carbonate that evolve towards a poorly crystalline cobalt hydroxide carbonate with aging treatment. Solubility of both phases have been calculated under two different approaches: precipitation and dissolution. Values of solubility from each approach were obtained with a general error due to differences in experiment conditions, for instance, ionic strength, temperature and

  20. On the light intensity transmitted through water and aqueous supersaturated ammonium dihydrogen phosphate solutions containing different antisolvents

    Science.gov (United States)

    Sangwal, Keshra

    2017-02-01

    Experimental data of the dependence of transmitted laser light intensity I of aqueous ADP solutions saturated at 303.15 K on feeding time t of three antisolvents (i.e. acetone, methanol and ethanol) are analyzed using mathematical equations based on two approaches. The first approach is based on exponential decrease in I with increasing t whereas the second one is based on the concept of adsorption of antisolvent molecules onto solvent and solute molecules. It was found that: (1) the latter approach is superior to the former one for explaining the observed dependence of transmitted laser-beam intensities of pure solvent and aqueous saturated ADP solutions, (2) the parameter A of the second approach provides better insight into the processes of adsorption of antisolvents in terms of the differential heat Qdiff of adsorption, and (3) the trends of changes in the values Qdiff for different antisolvents in water and aqueous solutions are associated with the dielectric constants of different antisolvents and are directly connected with the chemical constitution of the methanol, ethanol and acetone molecules.

  1. Removal of thorium (IV) ions from aqueous solution by a novel nanoporous ZnO: Isotherms, kinetic and thermodynamic studies.

    Science.gov (United States)

    Kaynar, Ümit H; Ayvacıklı, Mehmet; Hiçsönmez, Ümran; Kaynar, Sermin Çam

    2015-12-01

    The adsorption of thorium (IV) from aqueous solutions onto a novel nanoporous ZnO particles prepared by microwave assisted combustion was studied using batch methods under different experimental conditions. The effect of contact time, solution pH, initial concentration and temperature on adsorption process was studied. The ability of this material to remove Th (IV) from aqueous solution was characterises by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption percent and distribution coefficient for nanoporous ZnO powders in optimum conditions were 97% ± 1.02; 8080 L kg(-1)for Th (IV), respectively. Based on the Langmuir model, the maximum adsorption capacity of nanoporous ZnO for Th (IV) was found to be 1500 g kg(-1). Thermodynamic parameters were determined and discussed. The results indicated that nanoporous ZnO was suitable as sorbent material for recovery and adsorption of Th (IV) ions from aqueous solutions. The radioactive Th (VI) in surface water, sea water and waste waters from technologies producing nuclear fuels, mining (uranium and thorium) and laboratories working with radioactive materials (uranium and thorium) can be removed with this nanoporous ZnO.

  2. 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.

  3. 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

  4. 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...

  5. 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.

  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. 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.

  10. 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.

  11. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-09-15

    The biosorption of Cu(II) from aqueous solutions by mimosa tannin resin (MTR) was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmiur isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, and the Elovich and the intraparticle diffusion equation - to determine the best fit equation for the biosorption of copper ions onto mimosa tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well. Thermodynamic parameters such as the entropy change, enthalpy change and Gibb's free energy change were found out to be 153.0 J mol{sup -1} K{sup -1}, 42.09 kJ mol{sup -1} and -2.47 kJ mol{sup -1}, respectively.

  13. Experimental studies on removal of carbon dioxide by aqueous ammonia fine spray

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Experimental studies on carbon dioxide capture in a spray scrubber were carried out.Fine spray of aqueous ammonia was used as CO2 absorbent.Effects of different operating and design parameters on CO2 removal efficiency including concentration of aqueous ammonia,liquid flow rate,total gas flow rate,initial temperature and concentration of carbon dioxide were investigated.

  14. 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.

  15. Equilibrium solubility of CO{sub 2} in aqueous solutions of 1-amino-2-propanol as function of concentration, temperature, and pressure

    Energy Technology Data Exchange (ETDEWEB)

    Rebolledo-Morales, Miguel Angel; Rebolledo-Libreros, Maria Esther [Instituto Mexicano del Petroleo, Direccion de Investigacion y Posgrado, Programa de Ingenieria Molecular, Area de Investigacion de Termofisica, Eje Central Lazaro Cardenas Norte 152, 07730 Mexico, D.F. (Mexico); Trejo, Arturo, E-mail: atrejo@imp.m [Instituto Mexicano del Petroleo, Direccion de Investigacion y Posgrado, Programa de Ingenieria Molecular, Area de Investigacion de Termofisica, Eje Central Lazaro Cardenas Norte 152, 07730 Mexico, D.F. (Mexico)

    2011-05-15

    Research highlights: Gas solubility of CO{sub 2} in aqueous solutions of 1-amino-2-propanol was measured. Solubility increases as pressure and concentration of 1-amino-2-propanol increase. The Kent-Eisenberg model was used to correlate all the experimental results. Aqueous solutions of MIPA are an excellent alternative to use in gas purification. - Abstract: Using a dynamic method with recirculation of the vapour phase, experimental values for the gas solubility of carbon dioxide in aqueous solutions of 1-amino-2-propanol (MIPA) were measured at T = (313.15 and 393.15) K, over the pressure range of (0.2 to 2436.4) kPa. The concentrations of the studied aqueous MIPA solutions were (0.20, 0.30, 0.40, and 0.50) mass fraction. The results of gas solubility are given as the partial pressure of CO{sub 2}, p{sub CO{sub 2}}, against its mole ratio, {alpha}{sub CO{sub 2}} (mol CO{sub 2} {center_dot} mol{sup -1} MIPA), and its mole fraction, x{sub CO{sub 2}}. It is observed that the solubility of CO{sub 2} increases as the concentration of MIPA in solution increases, at a given temperature throughout the pressure range considered; also the solubility values increase, under constant temperature, as the pressure increases in the studied concentration range of MIPA. The physicochemical model of Kent and Eisenberg was used to correlate simultaneously all the experimental results of the solubility of CO{sub 2} in the studied aqueous solutions of MIPA. The model correlates satisfactorily the experimental results. The deviation for pressure was 96.9 kPa using 62 experimental solubility points. The solubility results of carbon dioxide presented in this work are compared with those reported in the literature for aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA), and N-methyldiethanolamine (MDEA) and it is possible to conclude that the aqueous solutions of MIPA are an excellent alternative to use in gas purification processes, since the

  16. A study of Reactive Red 198 adsorption on iron filings from aqueous solutions.

    Science.gov (United States)

    Azhdarpoor, Abooalfazl; Nikmanesh, Roya; Khademi, Fahime

    2014-01-01

    In recent years, reactive dyes have been widely used in textile industries with particular efficiency. They dyes are often toxic, carcinogenic and mutagenic. Improper treatment and non-scientific disposal of dyed wastewater from these industries into water sources has created many environmental problems and concerns around the world. The purpose of the present study is to investigate the efficiency of iron filings in adsorption of Reactive Red 198 from aqueous solutions. This study was conducted using an experimental method at the laboratory scale. In this study, the effects of operating parameters such as pH (1-11), initial dye concentration (40-400 mg/L), contact time (5-120 min) and iron dose (0.1-1 g) with a mesh ofDye concentration was determined using a spectrophotometer at a wavelength of 520 nm. The results indicated that maximum adsorption capacity of the dye in question was obtained at pH 3, contact time of 60 min and adsorbent dose of 1 g. At initial dye concentration of 100 and 200 mg/L, by increasing the dose of waste iron from 0.1 to 1 g, the removal percentage increased from approximately 76.89% to 97.28% and from 22.64% to 68.03%, respectively. At pH 3, contact time of 5 min and constant waste iron dose of 0.8 g, the dye removal efficiency was 85.34%. By increasing the contact time to 120 min, the removal efficiency increased to 99.2%. Welding iron waste as an inexpensive and available adsorbent has an optimum ability for adsorption of Reactive Red 198 from aqueous solutions.

  17. Possibility of using by-products of the steelmaking industry for removing lead from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Martín, M. I.

    2008-06-01

    Full Text Available A study is made of the use of two steelmaking industry by-products (rolling mill scale and blast furnace sludge as adsorbent materials for removing Pb2+ ions from aqueous solutions. The adsorption of Pb2+ on these materials has been studied by the determination of adsorption isotherms. Several variables that affect the process (contact time, initial lead ion concentration and temperature were evaluated. The adsorption processes are analysed using the Langmuir theory. Desorption processes for the metal from loaded by-products were also studied under different experimental conditions. This paper shows that these industrial residues are effective adsorbents for lead ions in aqueous solutions within the range of working concentrations.

    Se estudia el uso de dos subproductos de la industria del acero (cascarilla de laminación y lodo de horno alto como materiales adsorbentes para eliminar iones Pb2+ de soluciones acuosas. La adsorción de Pb2+ sobre estos materiales se ha estudiado determinando las isotermas de adsorción. Se evaluaron diferentes variables que afectan al proceso (tiempo de contacto, concentración inicial de iones plomo y temperatura. Los procesos de adsorción se estudian usando la teoría de Langmuir. Los procesos de desorción de los metales también se estudiaron bajo diferentes condiciones experimentales. Este trabajo muestra que estos residuos industriales son adsorbentes efectivos de iones plomo en soluciones acuosas en el rango de las concentraciones de trabajo utilizadas.

  18. 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.

  19. 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.

  20. 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.