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Sample records for polluted aqueous solutions

  1. Mechanisms of removing pollutants from aqueous solutions by microorganisms and their aggregates: a review.

    PubMed

    Wu, Yonghong; Li, Tianling; Yang, Linzhang

    2012-03-01

    With the public's enhanced awareness of eco-safety, environmentally benign measures based on microorganisms and microbial aggregates have become more accepted as methods of removing pollutants from aquatic systems. In this review, the application of microorganisms and microbial aggregates for removing pollutants from aqueous solutions is introduced and described based on mechanisms such as assimilation, adsorption, and biodegradation. The advantages of and future studies regarding the use of microorganisms and microbial aggregates to remove pollutants are discussed. Due to the limitation of a single microorganism species in adapting to heterogeneous conditions, this review demonstrates that the application of microbial aggregates consisting of multiple photoautotrophic and heterotrophic microorganisms, is a promising method of removing multiple pollutants from complex wastewaters and warrants further research.

  2. Microwave-induced carbon nanotubes catalytic degradation of organic pollutants in aqueous solution.

    PubMed

    Chen, Jing; Xue, Shuang; Song, Youtao; Shen, Manli; Zhang, Zhaohong; Yuan, Tianxin; Tian, Fangyuan; Dionysiou, Dionysios D

    2016-06-05

    In this study, a new catalytic degradation technology using microwave induced carbon nanotubes (MW/CNTs) was proposed and applied in the treatment of organic pollutants in aqueous solution. The catalytic activity of three CNTs of 10-20nm, 20-40nm, and 40-60nm diameters were compared. The results showed that organic pollutants such as methyl orange (MO), methyl parathion (MP), sodium dodecyl benzene sulfonate (SDBS), bisphenol A (BPA), and methylene blue (MB) in aqueous solution could be degraded effectively and rapidly in MW/CNTs system. CNTs with diameter of 10-20nm exhibited the highest catalytic activity of the three CNTs under MW irradiation. Further, complete degradation was obtained using 10-20nm CNTs within 7.0min irradiation when 25mL MO solution (25mg/L), 1.2g/L catalyst dose, 450W, 2450MHz, and pH=6.0 were applied. The rate constants (k) for the degradation of SDBS, MB, MP, MO and BPA using 10-20nm CNTs/MW system were 0.726, 0.679, 0.463, 0.334 and 0.168min(-1), respectively. Therefore, this technology may have potential application for the treatment of targeted organic pollutants in wastewaters.

  3. Amino-functionalized silica magnetite nanoparticles for the simultaneous removal of pollutants from aqueous solution

    NASA Astrophysics Data System (ADS)

    Hozhabr Araghi, Samira; Entezari, Mohammad H.

    2015-04-01

    Amino-functionalized silica magnetite nanoparticles (A-S-MNPs) have been prepared through coating of sono-synthesized magnetite nanoparticles (MNPs) in a basic medium by SiO2. Then, the resultant silica magnetite nanoparticles (S-MNPs) were modified with 3-aminpropyltriethoxysilane (APTES). The modification was carried out by the organic solvent method in dry hexane to graft amine groups on the surface. The adsorption behavior of this novel magnetic sorbent was studied for the simultaneous removal of two organic pollutants containing the sulfonate group, e.g., Reactive Black 5 (RB5) and sodium dodecylbenzenesulfonate (SDBS) in aqueous solutions. The results show that a pseudo-second-order model fits well the experimental data and the rate constant of adsorption for SDBS is higher than for RB5. The adsorption capacity was obtained by the Langmuir isotherm. The qmax was 83.33 and 62.5 mg/g for RB5 and SDBS at pH 2 and 298 K, respectively. Furthermore, the loaded A-S-MNPs can be recovered easily from aqueous solution by magnetic separation and regenerated by simply washing with 0.1 M NaOH solution. Therefore, the synthesized novel magnetic sorbent can be used as an effective and recyclable adsorbent for the simultaneous removal of dye and surfactant from aqueous solutions.

  4. Fungal biosorption--an alternative to meet the challenges of heavy metal pollution in aqueous solutions.

    PubMed

    Dhankhar, Rajesh; Hooda, Anju

    2011-04-01

    The removal of heavy metal from the environment, especially wastewater, is now shifting from the use of conventional methods to the use of biosorption, which may be defined as the binding and concentration of selected heavy metal ions or other molecules on to certain biological material. Although most biosorption research concerns metal and related pollutants, including radionuclides, the term is now applied for particulates and all manner of organic pollutants as well. Such pollutants can be in gaseous, soluble and insoluble forms. Biosorption is a physical process carried out through mechanisms such as ion exchange, surface complexation and precipitation. It is a property of both living and dead organisms (and their components) and has been heralded as a promising biotechnology for pollutant removal from solution. Various biomasses such as plant products (tree bark, peanut skin, sawdust, plant weeds etc.) have been tested for metal biosorption with very encouraging results. In this comprehensive review, biosorptive ability of fungal biomass toward heavy metals is emphasized. A detailed description of adsorption properties and mode of action of fungal biosorbents is offered in order to explain the heavy metal selectivity displayed by these biosorbents. The cell structure and cell wall of the fungal cell is evaluated in terms of metal sequestration. The parameters influencing the passive uptake of pollutants are analysed. The binding mechanism is discussed, including the key functional groups involved in the process. Quantification of metal-biomass interactions is fundamental to evaluation of potential implementation strategies; hence sorption isotherms and sorption kinetics, as well as models used to characterize fungal biosorbent sorption, are reviewed. Despite the continuing dramatic increase in published research on biosorption, there has been little or no exploitation in an industrial context. Thus, the current status and future directions regarding

  5. Pollution Solution

    ERIC Educational Resources Information Center

    Vannan, Donald A.

    1972-01-01

    Stresses briefly the need for individuals' actions for controlling the environmental pollution. A number of projects are suggested for teachers to involve children in this area. Simulated discussion groups of sellers'' and consumers, use of pictures, onion juice, and a water filtration contest are a few of the sources used. (PS)

  6. Pollution Solution

    ERIC Educational Resources Information Center

    Vannan, Donald A.

    1972-01-01

    Stresses briefly the need for individuals' actions for controlling the environmental pollution. A number of projects are suggested for teachers to involve children in this area. Simulated discussion groups of sellers'' and consumers, use of pictures, onion juice, and a water filtration contest are a few of the sources used. (PS)

  7. Use of two grasses for the phytoremediation of aqueous solutions polluted with terbuthylazine.

    PubMed

    Buono, Daniele Del; Pannacci, Euro; Bartucca, Maria Luce; Nasini, Luigi; Proietti, Primo; Tei, Francesco

    2016-09-01

    The capacity of two grasses, tall fescue (Festuca arundinacea) and orchardgrass (Dactylis glomerata), to remove terbuthylazine (TBA) from polluted solutions has been assessed in hydroponic cultures. Different TBA concentrations (0.06, 0.31, 0.62, and 1.24 mg/L) were chosen to test the capacity of the two grasses to resist the chemical. Aerial biomass, effective concentrations (to cause reductions of 10, 50, and 90% of plant aerial biomass) and chlorophylls contents of orchardgrass were found to be more affected. Tall fescue was found to be more capable of removing the TBA from the growth media. Furthermore, enzymes involved both in the herbicide detoxification and in the response to herbicide-induced oxidative stress were investigated. Glutathione S-transferase (GST, EC. 2.5.1.18) and ascorbate peroxidase (APX, EC. 1.11.1.11) of tall fescue were found to be unaffected by the chemical. GST and APX levels of orchardgrass were decreased by the treatment. These negative modulations exerted by the TBA on the enzyme of orchardgrass explained its lower capacity to cope with the negative effects of the TBA.

  8. Sorption potential of Moringa oleifera pods for the removal of organic pollutants from aqueous solutions.

    PubMed

    Akhtar, Mubeena; Moosa Hasany, S; Bhanger, M I; Iqbal, Shahid

    2007-03-22

    Moringa oleifera pods Lamarck (Drumstick or Horseradish) is a multipurpose medium or small size tree from sub-Himalayan regions of north-west India and indigenous to many parts of Asia, Africa, South America, and in the Pacific and Caribbean Islands. Its pods (MOP) have been employed as an inexpensive and effective sorbent for the removal of organics, i.e., benzene, toluene, ethylbenzene and cumene (BTEC) from aqueous solutions using HPLC method. Effect of different parameters, i.e., sorbent dose 0.05-0.8g, 25cm(-3) agitation time 5-120min, pH 1-10, temperature 283-308K and concentration of sorbate (1.3-13)x10(-3), (1.1-11)x10(-3), (0.9-9)x10(-3), (0.8-8)x10(-3)moldm(-3), on the sorption potential of MOP for BTEC have been investigated. The pore area and average pore diameter of the MOP by BET method using nitrogen as a standard are calculated to be 28.06+/-0.8m(2)g(-1) and 86.2+/-1.3nm respectively. Freundlich, Langumir and Dubinin-Radushkevich (D-R) sorption isotherms were employed to evaluate the sorption capacity of MOP. Sorption capacities of BTEC onto MOP have been found to be 46+/-10, 84+/-9, 101+/-4, 106+/-32mmolg(-1) by Freundlich, 8+/-0.1, 9+/-0.1, 10+/-0.3, 9+/-0.1mmolg(-1) by Langumir and 15+/-1, 21+/-1, 23+/-2, 22+/-3mmolg(-1) by D-R isotherms respectively, from BTEC solutions at 303K. While the mean energy of sorption process 9.6+/-0.3, 9.2+/-0.2, 9.3+/-0.3, 9.5+/-0.4kJmol(-1) for BTEC is calculated by D-R isotherm only. Rate constant of BTEC onto MOP 0.033+/-0.003, 0.030+/-0.002, 0.029+/-0.002, 0.027+/-0.002min(-1) at solution concentration of 1.3x10(-3), 1.1x10(-3), 0.9x10(-3) and 0.8x10(-3)moldm(-3) and at 303K have been calculated by employing Lagergren equation. Thermodynamic parameters DeltaH -8+/-0.4, -10+/-0.6, -11+/-0.7, -11+/-0.7kJmol(-1), DeltaS -22+/-2, -26+/-2, -27+/-2, -29+/-3Jmol(-1)K(-1) and DeltaG(303K) -0.9+/-0.2, -1.9+/-0.2, -2.3+/-0.1 and -2.6+/-0.2kJmol(-1) were also estimated for BTEC respectively at temperatures 283-308K. The

  9. Efficient degradation of organic pollutants in aqueous solution with bicarbonate-activated hydrogen peroxide.

    PubMed

    Xu, Aihua; Li, Xiaoxia; Xiong, Hui; Yin, Guochuan

    2011-02-01

    Bicarbonate anion is an efficient activator for hydrogen peroxide to generate many active oxygen species including peroxymonocarbonate (HCO(4)(-)), superoxide ion (O(2)(-)) and singlet oxygen ((1)O(2)). This study aims to understand the oxidative degradation of organic pollutants including methyl blue, methyl orange, rhodamine B, and 4-chlorophenol, with H(2)O(2) activated by sodium bicarbonate at room temperature. The obtained results indicate that such a method is apparently efficient in versatile pollutant degradation. Compared with using H(2)O(2) alone under similar pH conditions, the degradation rates of the pollutants were greatly enhanced through adding NaHCO(3). Through LC-MS, FT-IR and the TOC analysis, the degradation of methylene blue was revealed to proceed by the transformation of dimethylamino group in methylene blue to methylamino, aldehyde and nitro group, and the opening of phenyl ring into small molecular compounds and CO(2). The studies using the (1)O(2) scavenger sodium azide and the O(2)(-) indicator nitro blue tetrazolium suggest that the active O(2)(-) intermediate, generated from HCO(4)(-) decomposition, rather than (1)O(2) was involved in the pollutant degradation.

  10. Reflectance of aqueous solutions

    NASA Technical Reports Server (NTRS)

    Querry, M. R.

    1972-01-01

    The optical properties and optical constants of water and aqueous solutions were studied to develop an accurate tabulation of graphical representations of the optical constants through a broad spectrum. Manuscripts of articles are presented concerning extinction coefficients, relative specular reflectance, and temperature effect on the water spectrum. Graphs of absolute reflectance, phase shifts, index of refraction, and extinction coefficients for water, heavy water and aqueous solutions are included.

  11. [Surface organic modification of acid vermiculite and its adsorption of hydrophobic micro pollutants in aqueous solutions].

    PubMed

    Jiang, Zheng-Ming; Yu, Xu-Biao; Hu, Yun; Ren, Yuan; Li, Xue-Hui; Wei, Chao-Hai

    2013-07-01

    To solve the problems of intercalated organoclay such as low surface area and inhomogeneous organic loading, natural vermiculite was activated by acid leaching and then modified by trimethylchlorosilane (CTMS) and triethylchlorosilane (CTES). The modified materials were characterized by FTIR, BET, SEM and TG. Experimental results indicated that the surface area of the modified acid vermiculite (361.0 m2 x g(-1)) was much larger than that of the intercalated organovermiculite (6.0 m2 x g(-1)), moreover, the organic groups were grafted onto the surface covalently. Diethyl phthalate (DEP), a typical hydrophobic micro-organic pollutant, was used to test the adsorption capacity of different adsorbents. The adsorption amounts of DEP were 63.7, 51.2 and 15.7 mg x g(-1) for CTES, CTMS and intercalated organovermiculite in this study, respectively. The high organic affinity of modified acid vermiculite was due to both the bigger surface area and the homogeneous organic loading. The adsorption kinetics was found to follow the pseudosecond-order model. The isotherms exhibited linear characteristics and could be described by Henry and Freundlich equations, indicating that the partition process is the main control mechanism of the removal of DEP.

  12. Electrochemical removal of microcystin-LR from aqueous solution in the presence of natural organic pollutants.

    PubMed

    Tran, Nam; Drogui, Patrick

    2013-01-15

    Removal of microcystin-LR (MC-LR) from water was evaluated using an electro-oxidation process. Different operating parameters were investigated, including current density, reaction time, anode material and type of supporting electrolyte. The current density and the type of anode material played an important role in the MC-LR degradation efficiency, whereas the type of sodium salts influenced the removal efficiency. The degradation of MC-LR was mainly attributed to direct anodic oxidation. The best operating conditions (98% of MC-LR removal) for MC-LR (initial concentration of 11-13 μg L(-1)) degradation in solution were obtained at a current density of 38 mA cm(-2) for 60 min with a recycling rate of 0.1 L min(-1) using a Ti/BDD anode in the presence of 0.2 g L(-1) of Na(2)SO(4). The colour caused by the presence of natural organic matter (humic acid) could be diminished by up to 81%. Likewise, MC-LR decomposition exhibited first-order reaction behaviours with a rate coefficient of 0.049 min(-1). Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Equilibrium adsorption studies of some aromatic pollutants from dilute aqueous solutions on activated carbon at different temperatures

    SciTech Connect

    Khan, A.R.; Ataullah, R.; Al-Haddad, A.

    1997-10-01

    Aqueous solutions of phenol, p-chlorophenol, and p-nitrophenol have been used to determine the adsorption isotherm for single solute systems on activated carbon at different temperatures. The experimental program has been conducted to investigate the influence of concentration and temperature. All the reported equilibrium isotherm equations have been tried on present and published experimental data. A generalized isotherm equation which was proposed by Khan et al. and tested for bi-solute adsorption data has been modified for single-solute system. The temperature dependency has also been incorporated into a generalized equation. It has been noticed that the Radke and Prausnitz and generalized isotherm equations could represent the entire data with a minimum average percentage error. The influence of different adsorbents, sorbate concentrations, and pH of aqueous solutions has also been discussed in detail. The temperature dependency has been investigated using both the Dubinin-Astakov and the modified generalized equation. The generalized equation describes the experimental and published data adequately and provides a single value of differential molar heat of adsorption, {Delta}H{sub ads}, for a single solute adsorption system. The Dubinin-Astakov isotherm equation has shown an increasing trend of {Delta}H{sub ads} as the loading of adsorbent has increased.

  14. The photochemistry of carbon nanotubes and its impact on the photo-degradation of dye pollutants in aqueous solutions.

    PubMed

    Wu, Bingdang; Zhu, Dunxue; Zhang, Shujuan; Lin, Weizhen; Wu, Guozhong; Pan, Bingcai

    2015-02-01

    It is reported that carbon nanotubes (CNTs) could either generate reactive oxygen species (ROS) under light irradiation or serve as high-efficient scavenger for ROS. However, it is unclear which role predominates as CNTs enter into aquatic environment. To answer this question, a systematic study of the photochemistry of a pristine and a surface-functionalized CNTs in aqueous suspensions was investigated with both time-resolved and steady state analytical approaches. The transient absorption spectra demonstrate that CNTs could be photo-ionized and trap hydrated electrons upon high energy irradiation. In steady state UV irradiation, CNTs could promote the generation of ROS, such as (1)O2 and OH. However, in the presence of H2O2, the OH scavenging effect predominated in the aqueous suspensions of CNTs. The presence of CNTs suppressed the photo-degradation of dye pollutants, as an integrated result of inner filter effect, adsorption effect, and ROS generation and scavenging effect. The results provide useful information for the understanding of the environmental implications of CNTs. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Dopamine crosslinked graphene oxide membrane for simultaneous removal of organic pollutants and trace heavy metals from aqueous solution.

    PubMed

    Wang, Jing; Huang, Tiefan; Zhang, Lin; Yu, Qiming Jimmy; Hou, Li'an

    2017-09-08

    A graphene oxide-polydopamine-(β-cyclodextrin) (GPC) ultrafiltration membrane was fabricated by using the method of drop-coating combined with vacuum filtration. The prepared GPC membrane was characterized with FTIR and XPS spectrophotometry and evaluated for its performances for the rejection of organic molecules (methylene blue) and adsorption of trace heavy metals (Pb(2+)) from aqueous solutions. The membrane exhibited an excellent rejection coefficient of 99.2% for methylene blue and the permeation flux was 12 L m(-2) h(-1) at 0.1 bar. The membrane also exhibited fast adsorption kinetics for Pb(2+) and the adsorption capacity was 101.6 mg g(-1) at a solution pH of 6. The performance of the membrane could almost be completely recovered after a simple clean and regeneration process. These results indicate that the GPC membrane has potential applications in treatment of complex industrial wastewater streams.

  16. Nitrilotriacetic acid functionalized Adansonia digitata biosorbent: Preparation, characterization and sorption of Pb (II) and Cu (II) pollutants from aqueous solution.

    PubMed

    Adewuyi, Adewale; Pereira, Fabiano Vargas

    2016-11-01

    Nitrilotriacetic acid functionalized Adansonia digitata (NFAD) biosorbent has been synthesized using a simple and novel method. NFAD was characterized by X-ray Diffraction analysis technique (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analyzer, Fourier Transform Infrared spectrometer (FTIR), particle size dispersion, zeta potential, elemental analysis (CHNS/O analyzer), thermogravimetric analysis (TGA), differential thermal analysis (DTA), derivative thermogravimetric analysis (DTG) and energy dispersive spectroscopy (EDS). The ability of NFAD as biosorbent was evaluated for the removal of Pb (II) and Cu (II) ions from aqueous solutions. The particle distribution of NFAD was found to be monomodal while SEM revealed the surface to be heterogeneous. The adsorption capacity of NFAD toward Pb (II) ions was 54.417 mg/g while that of Cu (II) ions was found to be 9.349 mg/g. The adsorption of these metals was found to be monolayer, second-order-kinetic, and controlled by both intra-particle diffusion and liquid film diffusion. The results of this study were compared better than some reported biosorbents in the literature. The current study has revealed NFAD to be an effective biosorbent for the removal of Pb (II) and Cu (II) from aqueous solution.

  17. A comprehensive study of physical and physiological parameters that affect bio-sorption of metal pollutants from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Fosso-Kankeu, E.; Mulaba-Bafubiandi, A. F.; Mamba, B. B.; Marjanovic, L.; Barnard, T. G.

    An attempt was made to remove silver (I), chromium (III), and lead (II) from aqueous solutions. To optimize the bio-sorption capacity of microorganisms ( Bacillus subtilis and Bacillaceae bacterium), the effect of process parameters such as pH, temperature, metal load and culture age on the metal uptake was investigated. Indigenous strains of B. subtilis and Bacillaceae bacterium found in gold and copper mines in South Africa were exposed to silver (I), chromium (III), and lead (II) solutions under different physico-chemical and physiological conditions. Optimum conditions for the uptake of silver (I), chromium (III) and lead (II) by microorganisms used in this study were determined. The pH range 7-8, higher temperature (45 °C) and stationary growth phase, were observed as being suitable physical and physiological conditions for optimum removal of metals (Ag-87.2%; Cr-94% and Pb-98.5%). On the other hand very low pH (3) adversely affected the metal removal ability of bacteria. Silver (I) was the most poorly uptaken metal. It was also found that silver inhibited bacteria growth. Attempt to elute metal from the above cell biomass showed that 56.6% silver (I) and 88.3% lead (II) could effectively be desorbed at pH 5. It was additionally observed that optimum conditions for metal removal were specific to microbial bio-sorbent and the targeted metal. Design and implementation of bioremediation processes therefore require thorough study of specific interactions among metals and bio-sorbents involved.

  18. Ion segregation in aqueous solutions.

    PubMed

    Bian, Hongtao; Li, Jiebo; Zhang, Qiang; Chen, Hailong; Zhuang, Wei; Gao, Yi Qin; Zheng, Junrong

    2012-12-13

    Microscopic structures and dynamics of aqueous salt solutions were investigated with the ultrafast vibrational energy exchange method and anisotropy measurements. In KSCN aqueous solutions of various concentrations, the rotational time constants of SCN(-) anions are proportional to the viscosities of the solutions. However, the reorientation dynamics of the water molecules are only slightly affected by the solution viscosity. With the addition of strongly hydrated F(-) anions, the rotations of both SCN(-) anions and water molecules slow down. With the addition of weakly hydrated I(-) anions, only the rotation of SCN(-) anions slows down with that of water molecules unaffected. Vibrational energy exchange measurements show that the separation among SCN(-) anions decreases with the addition of F(-) and increases with the addition of I(-). The series of experiments clearly demonstrate that both structures and dynamics of ion and water are segregated in the strong electrolyte aqueous solutions.

  19. Supercooling behavior in aqueous solutions.

    PubMed

    Kimizuka, Norihito; Suzuki, Toru

    2007-03-08

    Using the emulsion method, we measured the homogeneous nucleation temperature depression, DeltaT(f,hom), and equilibrium melting points depression, DeltaT(m), of various aqueous solutions and then calculated lambda for each solute using the linear relationship DeltaT(f,hom) = lambdaDeltaT(m). We defined lambda as the solute-specific supercooling capacity and examined its correlation with some known hydration characteristics. The results showed that lambda is correlated with D0, the self-diffusion coefficient of solute molecules in infinite dilution.

  20. 2010 Water & Aqueous Solutions

    SciTech Connect

    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).

  1. CESIUM RECOVERY FROM AQUEOUS SOLUTIONS

    DOEpatents

    Goodall, C.A.

    1960-09-13

    A process is given for precipitating cesium on zinc ferricyanide (at least 0.0004 M) from aqueous solutions containing mineral acid in a concentration of from 0.2 N acidity to 0.61 N acid-deficiency and advantageously, but not necessarily, also aluminum nitrate in a concentration of from l to 2.5 M.

  2. Cesium recovery from aqueous solutions

    DOEpatents

    Goodhall, C. A.

    1960-09-13

    A process for recovering cesium from aqueous solutions is given in which precipitation on zinc ferricyanide is used. The precipitation is preferably carried out in solutions containing at least 0.0004M zinc ferricyanide, an acidity ranging from 0.2N mineral acid to 0.61N acid deficiency, and 1 to 2.5M aluminum nitrate. (D.L.C.)

  3. CESIUM RECOVERY FROM AQUEOUS SOLUTIONS

    DOEpatents

    Schneider, R.A.

    1961-06-20

    Cesium may be precipitated from an aqueous solution whose acidity ranges between a pH of 1.5 and a molarity of 5 on cobaltous, zinc, cadmium, nickel, or ferrous cobalticyanide. This precipitation brings about a separation from most fission products. Ruthenium which coprecipitates to a great degree can be removed by dissolving in sulfuric acid and boiling the solution in the presence of periodic acid for volatilization; other coprecipitated fission products can then be precipitated from the sulfuric acid solution with a ferric hydroxide carrier.

  4. The Pollution Solution.

    ERIC Educational Resources Information Center

    Stephens, Lillian

    1981-01-01

    Presented are methods to help teachers continue the environmental awareness programs they have already started by providing up-to-date information and activities dealing with air pollution, water pollution, and solid waste disposal. (Author/KC)

  5. The Pollution Solution.

    ERIC Educational Resources Information Center

    Stephens, Lillian

    1981-01-01

    Presented are methods to help teachers continue the environmental awareness programs they have already started by providing up-to-date information and activities dealing with air pollution, water pollution, and solid waste disposal. (Author/KC)

  6. Sucrose diffusion in aqueous solution

    PubMed Central

    Murray, Benjamin J.

    2016-01-01

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes–Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  7. Stabilized aqueous hydrogen peroxide solution

    SciTech Connect

    Malin, M.J.; Sciafani, L.D.

    1988-05-17

    This patent describes a stabilized aqueous hydrogen peroxide solution having a pH below 7 and an amount of Ferric ion up to about 2 ppm comprising hydrogen peroxide, acetanilide having a concentration which ranges between 0.74 M Mol/L and 2.22 mMol/L, and o-benzene disulfonic acid or salt thereof at a concentration between about 0.86 mMol/L to about 1.62 mMol/L.

  8. Specular reflectance of aqueous solutions.

    NASA Technical Reports Server (NTRS)

    Querry, M. R.; Waring, R. C.; Holland, W. E.; Mansell, G. R.

    1971-01-01

    Description of two laboratory instruments for measuring the specular reflectance of aqueous solutions. The instruments are an organic-dye-laser spectrophotometer for the 360- to 650-nm wavelength region and a reflectometer accessory for a Perkin-Elmer E-system spectrophotometer which will operate in the 0.2- to 20-micron wavelength region. The reflectometer accessory has been used to measure the relative infrared specular reflectance in limited spectral regions for aqueous solutions of NaCl, K2SO4, ZnSO4, (NH4)2SO4, and NH4H2PO4 with radiant flux incident at about 70 deg and polarized perpendicular to the plane of incidence. The laser spectrometer has been used to measure the absolute reflectance of aqueous solutions of NaCl in the wavelength region from 575 to 610 nm for light incident at angles of about 60, 65, and 70 deg and polarized parallel to the plane of incidence.

  9. Specular reflectance of aqueous solutions.

    NASA Technical Reports Server (NTRS)

    Querry, M. R.; Waring, R. C.; Holland, W. E.; Mansell, G. R.

    1971-01-01

    Description of two laboratory instruments for measuring the specular reflectance of aqueous solutions. The instruments are an organic-dye-laser spectrophotometer for the 360- to 650-nm wavelength region and a reflectometer accessory for a Perkin-Elmer E-system spectrophotometer which will operate in the 0.2- to 20-micron wavelength region. The reflectometer accessory has been used to measure the relative infrared specular reflectance in limited spectral regions for aqueous solutions of NaCl, K2SO4, ZnSO4, (NH4)2SO4, and NH4H2PO4 with radiant flux incident at about 70 deg and polarized perpendicular to the plane of incidence. The laser spectrometer has been used to measure the absolute reflectance of aqueous solutions of NaCl in the wavelength region from 575 to 610 nm for light incident at angles of about 60, 65, and 70 deg and polarized parallel to the plane of incidence.

  10. Thermosensitive aqueous solutions of polyvinylacetone

    NASA Astrophysics Data System (ADS)

    Wu, Wei-Tai; Wang, Yusong; Shi, Lei; Zhu, Qingren; Pang, Wenmin; Xu, Guoyong; Lu, Fei

    2006-04-01

    The dimethylketals of poly(vinyl alcohol), termed polyvinylacetone (PVKA), of moderate ketalization degree in the range from 0.28 to 0.6 exhibited temperature-induced phase transition in aqueous solution, as revealed by cloud point measurements and electron micrographs, which was then further investigated on molecular level using solution-state 1H NMR measurements. The present phase transition is caused by the amphiphilic characteristics in the polymer chain. Moreover, this finding could be further applied as a novel strategy in the syntheses of thermosensitive polymer by the hydrophobic functionalities of linear polyol.

  11. REMOVAL OF CHLORIDE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Schulz, W.W.

    1959-08-01

    The removal of chlorides from aqueons solutions is described. The process involves contacting the aqueous chloride containing solution with a benzene solution about 0.005 M in phenyl mercuric acetate whereby the chloride anions are taken up by the organic phase and separating the organic phase from the aqueous solutions.

  12. Iron-based adsorbent prepared from Litchi peel biomass via pyrolysis process for the removal of pharmaceutical pollutant from synthetic aqueous solution.

    PubMed

    Foletto, Vitória Segabinazzi; Ferreira, Ananda Bulegon; da Cruz Severo, Eric; Collazzo, Gabriela Carvalho; Foletto, Edson Luiz; Dotto, Guilherme Luiz

    2017-03-10

    A porous iron-based adsorbent obtained from litchi peel via pyrolysis process was prepared in this work, in order to evaluate its adsorptive potential for the removal of a pharmaceutical dye (amaranth) from aqueous solution. The material was characterized by X-ray diffraction, nitrogen adsorption-desorption isotherms, and scanning electron microscopy. Several isotherm and kinetic models were tested aiming to represent the amaranth dye adsorption. The prepared sample presented magnetic property, and a mesoporous texture constituted of graphite and three iron-based phases. The adsorption kinetics of amaranth on the adsorbent followed the pseudo-second-order model, whereas the equilibrium data were in good agreement with the BET isotherm, being represented by a sigmoid-shaped adsorption isotherm. The maximum adsorption capacity for the amaranth dye was found to be 44.87 mg g(-1), demonstrating that the material prepared in this work showed to be a promising adsorbent for the removal of amaranth from aqueous solution.

  13. SEPARATION OF RUTHENIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Beederman, M.; Vogler, S.; Hyman, H.H.

    1959-07-14

    The separation of rathenium from a rathenium containing aqueous solution is described. The separation is accomplished by adding sodium nitrite, silver nitrate and ozone to the ruthenium containing aqueous solution to form ruthenium tetroxide and ihen volatilizing off the ruthenium tetroxide.

  14. ENGINEERING BULLETIN: AIR STRIPPING OF AQUEOUS SOLUTIONS

    EPA Science Inventory

    Air striding is a means to transfer contaminants from aqueous solutions to air. ontaminants are not destroyed by air stripping but are physically separated from the aqueous solutions. ontaminant vapors are transferred into the air stream and, if necessary, can be treated by incin...

  15. ENGINEERING BULLETIN: AIR STRIPPING OF AQUEOUS SOLUTIONS

    EPA Science Inventory

    Air striding is a means to transfer contaminants from aqueous solutions to air. ontaminants are not destroyed by air stripping but are physically separated from the aqueous solutions. ontaminant vapors are transferred into the air stream and, if necessary, can be treated by incin...

  16. RECOVERY OF TETRAVALENT CATIONS FROM AQUEOUS SOLUTIONS

    DOEpatents

    Moore, R.L.

    1958-05-01

    The recovery of plutonium, zirconium, and tetravalent cerium values from aqueous solutions is described. It consists of adding an alkyl phosphate to a nnineral acid aqueous solution containing the metal to be recovered, whereby a precipitate forms with the tetravalent values, and separating the precipitate from the solution. All alkyl phosphates, if water-soluble, are suitable for the process; however, monobutyl phosphate has been found best.

  17. Photocatalytic removal of organic pollutants in aqueous solution by Bi(4)Nb(x)Ta((1-x))O(8)I.

    PubMed

    Hu, Xing-Yun; Fan, Jing; Zhang, Ke-Lei; Wang, Jian-Ji

    2012-06-01

    In this work, Bi(4)Nb(x)Ta((1-x))O(8)I photocatalysts have been synthesized by solid state reaction method and characterized by powder X-ray diffraction, scanning electron microscope and UV-Vis near infrared diffuse reflectance spectroscopy. The photocatalytic activity of these photocatalysts was evaluated by the degradation of methyl orange (MO) in aqueous solutions under visible light, UV light and solar irradiation. The effects of catalyst dosage, initial pH and MO concentration on the removal efficiency were studied, and the photocatalytic reaction kinetics of MO degradation as well. The results indicated that Bi(4)Nb(x)Ta((1-x))O(8)I exhibited high photocatalytic activity for the removal of MO in aqueous solutions. For example, the removal efficiency of MO by Bi(4)Nb(0.1)Ta(0.9)O(8)I was as high as 92% within 12 h visible light irradiation under the optimal conditions: initial MO concentration of 5-10 mg L(-1), catalyst dosage of 6 g L(-1) and natural pH (6-8), the MO molecules could be completely degradated by Bi(4)Nb(0.1)Ta(0.9)O(8)I within 40 min under UV light irradiation, and the photodegradation efficiency reaches to 60% after 7 h solar irradiation. Furthermore, the photocatalytic degradation of Bisphenol A (BPA) was also investigated under visible light irradiation. It is found that 99% BPA could be mineralized by Bi(4)Nb(0.1)Ta(0.9)O(8)I after 16 h visible light irradiation. Through HPLC/MS, BOD, TOC, UV-Vis measurements, we determined possible degradation products of MO and BPA. The results indicated that MO was degradated into products which are easier to be biodegradable and innocuous treated, and BPA could be mineralized completely. Furthermore, the possibility for the photosensitization effect in the degradation process of MO under visible light irradiation has been excluded. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Ibuprofen photodegradation in aqueous solutions.

    PubMed

    Iovino, Pasquale; Chianese, Simeone; Canzano, Silvana; Prisciandaro, Marina; Musmarra, Dino

    2016-11-01

    The advanced treatment of polluted liquid streams containing traces of pharmaceutical compounds is a major issue, since more and more effluents from pharma labs and wastewaters containing the excretions of medically treated humans and animals are discharged in the conventional wastewater treatment plants without previous effective treatments. Ibuprofen is a widely used non-steroidal anti-inflammatory drug (NSAID), which explains why it is found in wastewaters so often. In this paper, the removal of IBP from simulated water streams was investigated by using a lab-scale experimental device, consisting of a batch reactor equipped with a lamp emitting monochromatic UV light at a fixed wavelength (254 nm) and various intensities. Three sets of experiments were carried out: the first to study IBP concentration as a function of time, at different volumes of treated solutions (V = 10-30 mL); the second to explore the effect of pH on IBP degradation as a function of time (pH = 2.25-8.25) and the third to evaluate the effect of different UV light intensities on IBP degradation (E = 100-400 mJ m(-2)). The IBP initial concentration (IBP 0) was varied in the range 30-60 mg L(-1). The results obtained show that the concentration of IBP decreases along with treatment time, with a negative effect of the treated volume, i.e. smaller volumes, such as lower liquid heights, are more easily degraded. Moreover, the higher the pH, the better the IBP degradation; actually, when pH increases from 2.25 to 6.6 and 8.25, the IBP concentration, after an hour of treatment, decreases respectively to 45, 34 and 27 % of its initial value. In addition, as the intensity of light increases from 100 to 400 mJ m(-2), the IBP concentration decreases to 34 % of its initial value. A reaction scheme is put forward in the paper, which well describes the effects of volume, pH and light intensity on the IBP degradation measured experimentally. Moreover, the IBP degradation by-products have

  19. Thermodynamic properties of potassium chloride aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zezin, Denis; Driesner, Thomas

    2017-04-01

    Potassium chloride is a ubiquitous salt in natural fluids, being the second most abundant dissolved salt in many geological aqueous solutions after sodium chloride. It is a simple solute and strong electrolyte easily dissociating in water, however the thermodynamic properties of KCl aqueous solutions were never correlated with sufficient accuracy for a wide range of physicochemical conditions. In this communication we propose a set of parameters for a Pitzer-type model which allows calculation of all necessary thermodynamic properties of KCl solution, namely excess Gibbs free energy and derived activity coefficient, apparent molar enthalpy, heat capacity and volume, as well as osmotic coefficient and activity of water in solutions. The system KCl-water is one of the best studied aqueous systems containing electrolytes. Although extensive experimental data were collected for thermodynamic properties of these solutions over the years, the accurate volumetric data became available only recently, thus making possible a complete thermodynamic formulation including a pressure dependence of excess Gibbs free energy and derived properties of the KCl-water liquids. Our proposed model is intended for calculation of major thermodynamic properties of KCl aqueous solutions at temperatures ranging from freezing point of a solution to 623 K, pressures ranging from saturated water vapor up to 150 MPa, and concentrations up to the salt saturation. This parameterized model will be further implemented in geochemical software packages and can facilitate the calculation of aqueous equilibrium for reactive transport codes.

  20. SEPARATION OF RUTHENIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Callis, C.F.; Moore, R.L.

    1959-09-01

    >The separation of ruthenium from aqueous solutions containing uranium plutonium, ruthenium, and fission products is described. The separation is accomplished by providing a nitric acid solution of plutonium, uranium, ruthenium, and fission products, oxidizing plutonium to the hexavalent state with sodium dichromate, contacting the solution with a water-immiscible organic solvent, such as hexone, to extract plutonyl, uranyl, ruthenium, and fission products, reducing with sodium ferrite the plutonyl in the solvent phase to trivalent plutonium, reextracting from the solvent phase the trivalent plutonium, ruthenium, and some fission products with an aqueous solution containing a salting out agent, introducing ozone into the aqueous acid solution to oxidize plutonium to the hexavalent state and ruthenium to ruthenium tetraoxide, and volatizing off the ruthenium tetraoxide.

  1. Evaluation of meat and bone meal combustion residue as lead immobilizing material for in situ remediation of polluted aqueous solutions and soils: "chemical and ecotoxicological studies".

    PubMed

    Deydier, E; Guilet, R; Cren, S; Pereas, V; Mouchet, F; Gauthier, L

    2007-07-19

    As a result of bovine spongiform encephalopathy (BSE) crisis, meat and bone meal (MBM) production can no longer be used to feed cattle and must be safely disposed of or transformed. MBM specific incineration remains an alternative that could offer the opportunity to achieve both thermal valorization and solid waste recovery as ashes are calcium phosphate-rich material. The aim of this work is to evaluate ashes efficiency for in situ remediation of lead-contaminated aqueous solutions and soils, and to assess the bioavailability of lead using two biological models, amphibian Xenopus laevis larvae and Nicotiana tabaccum tobacco plant. With the amphibian model, no toxic or genotoxic effects of ashes are observed with concentrations from 0.1 to 5 g of ashes/L. If toxic and genotoxic effects of lead appear at concentration higher than 1 mg Pb/L (1 ppm), addition of only 100 mg of ashes/L neutralizes lead toxicity even with lead concentration up to 10 ppm. Chemical investigations (kinetics and X-ray diffraction (XRD) analysis) reveals that lead is quickly immobilized as pyromorphite [Pb10(PO4)6(OH)2] and lead carbonate dihydrate [PbCO(3).2H2O]. Tobacco experiments are realized on contaminated soils with 50, 100, 2000 and 10000 ppm of lead with and without ashes amendment (35.3g ashes/kg of soil). Tobacco measurements show that plant elongation is bigger in an ashes-amended soil contaminated with 10000 ppm of lead than on the reference soil alone. Tobacco model points out that ashes present two beneficial actions as they do not only neutralize lead toxicity but also act as a fertilizer.

  2. Radiolysis of aqueous solutions of thiamine

    NASA Astrophysics Data System (ADS)

    Chijate, C.; Albarran, G.; Negron-Mendoza, A.

    1998-06-01

    The results of the radiolysis of aqueous solutions of thiamine (vitamin B 1) are presented. The yields for decomposition of thiamine and the product of radiolytic products were determined. The G values decrease as the dose increases. Some radiolytic products were identified. Decomposition of thiamine was slightly dependent on the presence of oxygen and on the pH of the solution. At pH 4.4 with a concentration of 2.5 × 10 -4 mol L -1 of thiamine in an oxygen free aqueous solution, the G 0 value for decomposition is 5.0.

  3. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C.

    1994-01-01

    A process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flow cell containing flow bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flow cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flow cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  4. ADSORPTION OF CERIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Roberts, F.P.

    1963-08-13

    Cerium can be removed from aqueous nitric acid (2 to 13 M) solutions by passing the latter over a PbO/sub 2/-containing anion exchange resin. The cerium is taken up by the resin, while any lanthanides, yttrium, and strontium present remain in the solution. (AEC)

  5. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  6. Precipitation of neptunium dioxide from aqueous solution

    SciTech Connect

    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

  7. Adsorption properties of kaolinite-based nanocomposites for Fe and Mn pollutants from aqueous solutions and raw ground water: kinetics and equilibrium studies.

    PubMed

    Shaban, Mohamed; Hassouna, Mohamed E M; Nasief, Fadya M; AbuKhadra, Mostafa R

    2017-08-17

    Raw kaolinite was used in the synthesis of metakaolinite/carbon nanotubes (K/CNTs) and kaolinite/starch (K/starch) nanocomposites. Raw kaolinite and the synthetic composites were characterized using XRD, SEM, and TEM techniques. The synthetic composites were used as adsorbents for Fe and Mn ions from aqueous solutions and natural underground water. The adsorption by the both composites is highly pH dependent and achieves high efficiency within the neutral pH range. The experimental adsorption data for the uptake of Fe and Mn ions by K/CNTs were found to be well represented by the pseudo-second-order kinetic model rather than the intra-particle diffusion model or Elovich model. For the adsorption using K/starch, the uptake results of Fe ions was well fitted by the second-order model, whereas the uptake of Mn ions fitted well to the Elovich model rather than pseudo-second-order and intra-particle diffusion models The equilibrium studies revealed the excellent fitting of the removal of Fe and Mn ions by K/CNTs and Fe using K/starch with the Langmuir isotherm model rather than with Freundlich and Temkin models. But the adsorption of Mn ions by K/starch is well fitted with Freundlich rather than Temkin and Langmuir isotherm models. The thermodynamic studies reflected the endothermic nature and the exothermic nature for the adsorption by K/CNTs and K/starch nanocomposites, respectively. Natural ground water contaminated by 0.4 mg/L Fe and 0.5 mg/L Mn was treated at the optimum conditions of pH 6 and 120 min contact time. Under these conditions, 92.5 and 72.5% Fe removal efficiencies were achieved using 20 mg of K/CNTs and K/starch nanocomposites, respectively. Also, K/CNTs nanocomposite shows higher efficiency in the removal of Mn ions as compared to K/starch nanocomposite.

  8. Thermodynamic Properties of Aqueous Solution of Ammonia

    NASA Astrophysics Data System (ADS)

    Kitamura, Hiroshi; Oguchi, Kosei

    Present status on the thermodynamic properties of experimental data and their correlations of both ammonia and aqueous solution of ammonia was introduced in this paper. The aqueous solution of ammonia is used for not only a working fluid in absorption refrigerator cycles but also working fluids in bottoming cycles of steam power plants and other heat recovering systems. Therefore, the thermodynamic properties of this substance are required in a wide range of temperatures, pressures and compositions. The experimental results of pVTx properties for ammonia and aqueous solution of ammonia and their comparisons with a formulation by Tillner-Roth and Friend1) were critically surveyed. The “Guideline on the IAPWS Formulation 2000 for the Thermodynamic Properties of Ammonia-Water Mixtures”, correlated by Tillner-Roth and Friend1), was approved on September, 2001, by the International Association for the Properties of Water and Steam (IAPWS) 2).

  9. RECOVERY OF PROTACTINIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Elson, R.E.

    1959-07-14

    The recovery of fluoride complexed protactinium from aqueous acidic solutions by solvent extraction is described. Generally the prccess of the invention com rises mixing an aqueous solution containing protactinium in a complexed form with an organic solvent which is specific for protactinium, such as diisopropyl carbinol, then decomposing the protactinium complex by adjusting the acidity of the aqueous solution to between 0-3 to 0-9 M in hydrogen ion concentration, and introducing a source of aluminum ions in sufficient quantity to establish a concentration of 0.5 to 1.2 M aluminum ion, whereupon decomposition of the protactinium fluoride complex takes place and the protactinium ion is taken up by the organic solvent phase.

  10. Superlubricity of a Mixed Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Ma, Zhi-Zuo; Zhang, Chen-Hui; Luo, Jian-Bin; Lu, Xin-Chun; Wen, Shi-Zhu

    2011-05-01

    A super-low friction coefficient of 0.0028 is measured under a pressure of 300 MPa when the friction pair (the silicon nitride ball sliding on the silicate glass) is lubricated by the mixed aqueous solution of glycerol and boric acid. The morphorlogies of the hydroxylated glass plate are observed by an atomic force microscope (AFM) in deionized water, glycerol, boric acid and their mixed aqueous solution. Bonding peaks of the retained liquids adhered on the surface of the sliding track are detected by an infrared spectrum apparatus and a Raman spectrum apparatus. The mechanism of the superlubricity of the glycerol and boric acid mixed aqueous solution is discussed. It is deduced that the formation of the lubricant film has enough strength to support higher loads, the hydration effect offering the super lower shear resistance. Key words: superlubricity, water based lubricant, ultra-low friction

  11. Removal of uranium from aqueous HF solutions

    DOEpatents

    Pulley, Howard; Seltzer, Steven F.

    1980-01-01

    This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a selected range and is employed in an amount providing a calcium fluoride/uranium weight ratio in a selected range. As applied to dilute HF solutions containing 120 ppm uranium, the method removes at least 92% of the uranium, without introducing contaminants to the product solution.

  12. Aqueous Solution Chemistry of Plutonium

    SciTech Connect

    Clark, David L.

    2014-01-28

    Things I have learned working with plutonium: Chemistry of plutonium is complex; Redox equilibria make Pu solution chemistry particularly challenging in the absence of complexing ligands; Understanding this behavior is key to successful Pu chemistry experiments; There is no suitable chemical analog for plutonium.

  13. Hydrophobic Solvation: Aqueous Methane Solutions

    ERIC Educational Resources Information Center

    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.

  14. Hydrophobic Solvation: Aqueous Methane Solutions

    ERIC Educational Resources Information Center

    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.

  15. Aqueous Solution Chemistry on Mars

    NASA Astrophysics Data System (ADS)

    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.

  16. Removal of metal ions from aqueous solution

    DOEpatents

    Jackson, Paul J.; Delhaize, Emmanuel; Robinson, Nigel J.; Unkefer, Clifford J.; Furlong, Clement

    1990-11-13

    A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat unit for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heayv metals from solution. This also results in the removal of the metals from the column in a concentrated form.

  17. Removal of metal ions from aqueous solution

    DOEpatents

    Jackson, Paul J.; Delhaize, Emmanuel; Robinson, Nigel J.; Unkefer, Clifford J.; Furlong, Clement

    1990-01-01

    A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat units for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heavy metals from solution. This also results in the removal of the metals from the column in a concentrated form.

  18. Unusual hydrophobic interactions in acidic aqueous solutions.

    PubMed

    Chen, Hanning; Xu, Jianqing; Voth, Gregory A

    2009-05-21

    Hydrophobic interaction, which is believed to be a primary driving force for many fundamental chemical and biological processes such as nanostructure self-assembly, micelle formation, and protein folding, is different in acidic aqueous solutions compared to salt solutions. In this study, the aggregation/dispersion behavior of nonpolar hydrophobic molecules in aqueous solutions with varying acid (HCl) concentrations is investigated using novel molecular dynamics simulations and compared to the hydrophobic behavior in corresponding salt (NaCl) solutions. The formation of unusual weakly bound hydrophobe-hydrated proton solvation structures is observed and can be attributed to the unique "amphiphilic" characteristic of hydrated protons. This molecular-level mechanism for the acid-enhanced dissolution of hydrophobic particles also provides a novel interpretation for the apparent anomaly of the hydronium cation in the Hofmeister series.

  19. RECOVERY OF PLUTONIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Reber, E.J.

    1959-09-01

    A process is described for recovering plutonium values from aqueous solutions by precipitation on bismuth phosphate. The plutonium is secured in its tetravalent state. bismuth salt is added to the solution, and ant excess of phosphoric acid anions is added to the solution in two approximately equal installments. The rate of addition of the first installment is about two to three times as high as the rate of addition of the second installment, whereby a precipitate of bismuth phosphate forms, the precipitate carrying the plutonium values. The precipitate is separated from the solution.

  20. The molecular velocity of sound. [aqueous solutions

    NASA Technical Reports Server (NTRS)

    Auslaender, D.; Onitiu, L.

    1974-01-01

    The molecular velocity of sound was calculated according to Rao's formula and the temperature and concentration dependences of this value were studied in aqueous solutions of alkali and alkaline-earth halides. Study of relative association brought to light characteristic effects of ions. The variation of the relative association can be explained by a breaking of hydrogen bonds by ions and thermal agitation.

  1. Water & Aqueous Solutions. Final Progress Report

    SciTech Connect

    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.

  2. PHOTOREACTION OF VALEROPHENONE IN AQUEOUS SOLUTION

    EPA Science Inventory

    Kinetics and products of the photoreaction of the phenyl ketone valerophenone were investigated as a function of temperature, pH, and wavelength in aqueous solution. Under these conditions (<10-4M), the photoreactions are pseudo-first-order with respect to valerophenone concentra...

  3. The molecular velocity of sound. [aqueous solutions

    NASA Technical Reports Server (NTRS)

    Auslaender, D.; Onitiu, L.

    1974-01-01

    The molecular velocity of sound was calculated according to Rao's formula and the temperature and concentration dependences of this value were studied in aqueous solutions of alkali and alkaline-earth halides. Study of relative association brought to light characteristic effects of ions. The variation of the relative association can be explained by a breaking of hydrogen bonds by ions and thermal agitation.

  4. PHOTOREACTION OF VALEROPHENONE IN AQUEOUS SOLUTION

    EPA Science Inventory

    Kinetics and products of the photoreaction of the phenyl ketone valerophenone were investigated as a function of temperature, pH, and wavelength in aqueous solution. Under these conditions (<10-4M), the photoreactions are pseudo-first-order with respect to valerophenone concentra...

  5. SEPARATION OF SCANDIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Peppard, D.F.; Nachtman, E.S.

    1958-02-25

    This patent relates to a process for the separation of scandium from yttrium, thorium, and trivalent rare earths and with their separation from each other. It has been found that scandium and yttrium can be separated from trivalent rare earths in acidic solution, for example, a solution 6 M in HCl, by contacting with tributyl phosphate, whereupon the scandum is preferentially extracted into the organic phase, leaving the yttrium and trivalent rare earths in the aqueous phase.

  6. A lithium ion battery using an aqueous electrolyte solution

    PubMed Central

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

    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 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. PMID:27328707

  7. Polyamide nanofiltration membranes to remove aniline in aqueous solutions.

    PubMed

    Hidalgo, A M; León, G; Gómez, M; Murcia, M D; Bernal, M D; Ortega, S

    2014-01-01

    Aniline is commonly used in a number of industrial processes. It is known to be a harmful and persistent pollutant and its presence in wastewater requires treatment before disposal. In this paper, the effectiveness of nanofiltration (NF) to remove aniline from aqueous solutions is studied in a flat membrane test module using two thin-layer composite membranes of polyamide (NF97 and NF99HF). The influence of different operational variables (applied pressure, feed concentration and pH) on the removal of aniline from synthetic aqueous solutions was analysed. The experimental NF results are compared with results previously obtained by reverse osmosis. Based on this comparative study, the effective order for aniline rejection is: HR98PP > NF97 > DESAL3B > SEPA-MS05 > NF99HF.

  8. A lithium ion battery using an aqueous electrolyte solution

    NASA Astrophysics Data System (ADS)

    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.

  9. A lithium ion battery using an aqueous electrolyte solution.

    PubMed

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

    2016-06-22

    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.

  10. Photodegradation of Norfloxacin in aqueous solution containing algae.

    PubMed

    Zhang, Junwei; Fu, Dafang; Wu, Jilong

    2012-01-01

    Photodegradation of Norfloxacin in aqueous solution containing algae under a medium pressure mercury lamp (15 W, lambda(max) = 365 nm) was investigated. Results indicated that the photodegradation of Norfloxacin could be induced by the algae in the heterogeneous algae-water 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 Norfloxacin. 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.

  11. Pollution! Find a STEM solution!

    NASA Astrophysics Data System (ADS)

    Takač, Danijela; Moćan, Marina

    2016-04-01

    Primary and secondary school Pantovčak is an innovative school in downtown Zagreb, Croatia. The school is involved in many projects concerning STEM education. Pollution! Find a STEM solution! is a two year long cross-curricular project that grew out of identified need to develop STEM and ICT skills more. Pisa results make evident that students' knowledge is poor and motivation for math and similar subjects is low. Implying priorities of European Commission, like e-learning, raises motivation and also develops basic skills and improves knowledge in science, math, physic, ICT. Main objectives are to increase students' interest in STEM education and careers and introduce them to all available new trends in technology, engineering and science in their region by visiting clean technology industries and strengthening links with them, to introduce some future digital jobs and prepare students for rapid technological changes by integrating ICT into classroom practice more, to highlight the importance of global environmental issues and improve the knowledge in the areas of sustainable development and renewable energy, to develop collaborative partnership between schools and the wider community in formal, non-formal and informal learning, to support multilingualism by publishing Open Educational Resources in 8 different languages and to strengthen the professional profile of the teaching profession. The project brings together 231 teachers and 2729 students from five different European countries in learning to think globally and work on activities that contribute to the community's well-being. There are altogether 33 activities, divided in 4 categories. STEM activities are focused on students building the devices for measuring air, light and noise pollution in their school and homes. They use the scientific method to analyze the data and compare the results with their peers to find a solution. Eskills, digital literacy and digital jobs are focused on introducing career

  12. Exclusion of Nitrate from Frozen Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Marrocco, H. A.; Michelsen, R. R.

    2013-12-01

    Reactions occurring at the surface of ice, sea ice, and snow in Earth's cryosphere have an impact on the composition of the overlying atmosphere. In order to elucidate reaction mechanisms and model their contributions to atmospheric processes, the morphology of frozen aqueous surfaces and amounts of reactants contained therein must be determined. To this end, the exclusion of nitrate ions to the surface of frozen aqueous solutions has been studied by attenuated total reflection infrared spectroscopy (ATR-IR). In this technique the near-surface region of the frozen films are interrogated to a depth of a few hundred nanometers from the film-crystal interface. Aqueous solutions (0.001 to 0.01 M) of sodium nitrate (NaNO3), magnesium nitrate (Mg(NO3)2), and nitric acid (HNO3) were quickly frozen on the germanium ATR crystal and observed at a constant temperature of about -18°C. In addition to ice and the solutes, liquid water in varying amounts was observed in the spectra. The amount of nitrate in the surface liquid is three to four orders of magnitude higher than in the unfrozen solution. While all the nitrate salts exhibit exclusion to the unfrozen surface, the dynamics are different for different counter-ions. Results are compared to freezing point depression data and the predictions of equilibrium thermodynamics.

  13. Critical Heat Flux of Butanol Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Shotaro; Shoji, Masahiro

    It is known that the addition of small amount of alcohol such as butanol to water enhances the CHF. Such aqueous solution is actively applied to heat transfer devices such as heat pipes and microchannel cooling systems, however, the fundamental characters of boiling have not been fully understood. In the present research, the experiment of boiling heat transfer is performed on a heated wire by employing butanol aqueous solution as a typical test solution and by changing concentration 1-butanol and subcooling in a wide range. Bubbling aspects were observed using high-speed video camera. It is found from the experiment that CHF is 2 to 3 times higher than that of pure water and generating bubbles are tiny even at the saturated condition. The dependence of CHF on subcooling is found to be curious showing that CHF decreases first, takes a minimum, and then increases with increasing subcooling. These results suggest that the butanol aqueous solution is a promising liquid for the application of boiling to a small-scaled cooling device.

  14. Hydroxide ion hydration in aqueous solutions.

    PubMed

    Smiechowski, Maciej; Stangret, Janusz

    2007-04-19

    Hydroxide ion hydration was studied in aqueous solutions of selected alkali metal hydroxides by means of Fourier transform infrared (FTIR) spectroscopy of HDO isotopically diluted in H2O. The quantitative difference spectra 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 solvation model (PCM) solvated aqueous clusters, OH-(H2O)n, n = 1-7, to establish the structural and energetic states of hydration spheres of the hydrated hydroxide anion. This was achieved by comparison of the calculated optimal geometries with the interatomic distances derived from HDO band positions. The energetic state of water in OH- hydration shells, as revealed by solute-affected HDO spectra, is similar to that of an isoelectronic F- anion. No evidence was found for the existence of stable hydroxide dimer, H3O2-, in an aqueous solution. Spectral data do confirm, however, existence of a weak interaction with a single water molecule at the hydrogen site of OH-.

  15. Water Pollution (Causes, Mechanisms, Solution).

    ERIC Educational Resources Information Center

    Strandberg, Carl

    Written for the general public, this book illustrates the causes, status, problem areas, and prediction and control of water pollution. Water pollution is one of the most pressing issues of our time and the author communicates the complexities of this problem to the reader in common language. The purpose of the introductory chapter is to show what…

  16. Water Pollution (Causes, Mechanisms, Solution).

    ERIC Educational Resources Information Center

    Strandberg, Carl

    Written for the general public, this book illustrates the causes, status, problem areas, and prediction and control of water pollution. Water pollution is one of the most pressing issues of our time and the author communicates the complexities of this problem to the reader in common language. The purpose of the introductory chapter is to show what…

  17. Aqueous solution dispersement of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    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.

  18. Optimization of aqueous degassing of rubber solutions

    SciTech Connect

    Rotenberg, E.B.; Slutsman, N.N.

    1983-02-01

    The optimality criterion of the aqueous degassing process of rubber solutions is proposed. The limitation system for the variables of the process is formulated. The problems of determination of the optimal temperature and average residence time of a rubber crumb in each degasifier, the number of degasifiers, and the total average residence time of a rubber crumb in the system at the planning and control stages are solved.

  19. REMOVAL OF CHLORIDE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Hyman, M.L.; Savolainen, J.E.

    1960-01-01

    A method is given for dissolving reactor fuel elements in which the uranium is associated with a relatively inert chromium-containing alloy such as stainless steel. An aqueous mixture of acids comprising 2 to 2.5 molar hydrochloric acid and 4 to 8 molar nitric acid is employed in dissolving the fuel element. In order io reduce corrosion in subsequent processing of the resulting solution, chloride values are removed from the solution by contacting it with concentrated nitric acid at an elevated temperature.

  20. Aggregation of sodium alkylbenzenesulfonates in aqueous solution

    SciTech Connect

    Magid, L.J.; Shaver, R.J.; Gulari, E.; Bedwell, B.; Alkhafaji, S.

    1981-01-01

    The surfactant 6 phenyl C/sub 12/SNa forms small spherical micelles in aqueous solution, having an aggregation number of 20 to 30 and a fractional charge of 0.45. These micelles are hydrated to the extent of approximately 18 moles H/sub 2/O per moles of surfactant. A second larger aggregate is also present in 6 phenyl C/sub 12/SNa solutions; its importance increases with solution age. Addition of NaCl causes both aggregates to apparently increase modestly in size. The surfactant 8 phenyl C/sub 16/SNa also contains both aggregates in its solutions; the larger one is relatively more important here. The larger aggregate does not correspond to dispersed bits of a liquid crystalline mesophase.

  1. 21 CFR 524.1200b - Kanamycin ophthalmic aqueous solution.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Kanamycin ophthalmic aqueous solution. 524.1200b... § 524.1200b Kanamycin ophthalmic aqueous solution. (a) Specifications. The drug, which is in an aqueous... kanamycin activity (as the sulfate) per milliliter of solution. (b) Sponsor. See No. 000856 in §...

  2. 21 CFR 524.1200b - Kanamycin ophthalmic aqueous solution.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Kanamycin ophthalmic aqueous solution. 524.1200b... § 524.1200b Kanamycin ophthalmic aqueous solution. (a) Specifications. The drug, which is in an aqueous... kanamycin activity (as the sulfate) per milliliter of solution. (b) Sponsor. See No. 000856 in §...

  3. 21 CFR 524.1200b - Kanamycin ophthalmic aqueous solution.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Kanamycin ophthalmic aqueous solution. 524.1200b... § 524.1200b Kanamycin ophthalmic aqueous solution. (a) Specifications. The drug, which is in an aqueous... kanamycin activity (as the sulfate) per milliliter of solution. (b) Sponsor. See No. 000856 in §...

  4. 21 CFR 524.1200b - Kanamycin ophthalmic aqueous solution.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Kanamycin ophthalmic aqueous solution. 524.1200b... § 524.1200b Kanamycin ophthalmic aqueous solution. (a) Specifications. The drug, which is in an aqueous... kanamycin activity (as the sulfate) per milliliter of solution. (b) Sponsor. See No. 000856 in §...

  5. Bentonite for ciprofloxacin removal from aqueous solution.

    PubMed

    Genç, Nevim; Can Dogan, Esra; Yurtsever, Meral

    2013-01-01

    Ciprofloxacin hydrochloride (CIP) is the second generation of fluoroquinolone antibiotics whose residues are found in wastewater and surface water. CIP has high aqueous solubility under different pH conditions and high stability in the soil system. In this study, bentonite was used as a potential sorbent for the removal of CIP from aqueous solutions using batch experiments. The effects of various parameters such as contact time, pH, adsorbent dosage, agitation speed, ionic strength and initial concentration of CIP in aqueous solution on the adsorption capacity were investigated. The optimum contact time, pH, agitation speed and adsorbent dosage were found to be 30 min, 4.5 pH, 150 rpm and 2.5 g L(-1), respectively. When the ionic strength was increased from 5 to 50 mM, the adsorption of CIP decreased from 97.8 to 93.4%. The isotherm adsorption data fitted well with the Langmuir model, Kl and qe were found to be 0.27 L mg(-1) and 147.06 mg g(-1), and the data fitted well with the pseudo-second order kinetics, whereby k was found to be 2.19 g mg(-1) h(-1).

  6. Density of aqueous solutions of CO2

    SciTech Connect

    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.

  7. Stability of melatonin in aqueous solution.

    PubMed

    Cavallo, A; Hassan, M

    1995-03-01

    Melatonin solutions are frequently used in human, animal, and in vitro research. Generally, fresh solutions are prepared, for fear of instability of melatonin in solution. We tested the high-performance liquid chromatography (HPLC) stability of melatonin in aqueous solutions stored room temperature, 4 degrees C, and -70 degrees C for up to 6 months. Solutions were prepared in a laminar flow hood using sterile technique, directly into sterile, pyrogen-free glass vacuum vials for storage. Different concentrations were tested (1.0-113.0 micrograms/ml). There was no loss of potency as assessed by HPLC, and the preparations remained sterile and pyrogen-free. We conclude that melatonin solutions may be prepared in batches maintained in sterile, pyrogen-free vials at 4 degrees C or at -70 degrees C until use within 6 months. This method will save on research time used for preparation of fresh solutions and will reduce the number of dose validation tests for each new experiment.

  8. Reversible State Transition in Nanoconfined Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Wang, Chunlei; Liu, Jian; Wen, Binghai; Tu, Yusong; Wang, Zuowei; Fang, Haiping

    2014-02-01

    Using molecular dynamics simulations, we find a reversible transition between the dispersion and aggregation states of solute molecules in aqueous solutions confined in nanoscale geometry, which is not observed in macroscopic systems. The nanoscale confinement also leads to a significant increase of the critical aggregation concentration (CAC). A theoretical model based on Gibbs free energy calculation is developed to describe the simulation results. It indicates that the reversible state transition is attributed to the low free energy barrier (of order kBT) in between two energy minima corresponding to the dispersion and aggregation states, and the enhancement of the CAC results from the fact that at lower concentrations the number of solute molecules is not large enough to allow the formation of a stable cluster in the confined systems.

  9. NIR spectroscopic properties of aqueous acids solutions.

    PubMed

    Omar, Ahmad Fairuz; Atan, Hanafi; Matjafri, Mohd Zubir

    2012-06-15

    Acid content is one of the important quality attributes in determining the maturity index of agricultural product, particularly fruits. Despite the fact that much research on the measurement of acidity in fruits through non-destructive spectroscopy analysis at NIR wavelengths between 700 to 1,000 nm has been conducted, the same response towards individual acids is not well known. This paper presents NIR spectroscopy analysis on aqueous citric, tartaric, malic and oxalic solutions through quantitative analysis by selecting a set of wavelengths that can best be used to measure the pH of the solutions. The aquaphotomics study of the acid solutions has generated R² above 0.9 for the measurement of all acids. The most important wavelengths for pH are located at 918-925 nm and 990-996 nm, while at 975 nm for water.

  10. Hydrogen production via photolytic oxidation of aqueous sodium sulfite solutions.

    PubMed

    Huang, Cunping; Linkous, Clovis A; Adebiyi, Olawale; T-Raissi, Ali

    2010-07-01

    Sulfur dioxide (SO(2)) emission from coal-burning power plants and refinery operations has been implicated as a cause of acid rain and other air pollution related problems. The conventional treatment of SO(2)-contaminated air consists of two steps: SO(2) absorption using an aqueous sodium hydroxide solution, forming aqueous sodium sulfite (Na(2)SO(3)), and Na(2)SO(3) oxidation via air purging to produce sodium sulfate (Na(2)SO(4)). In this process, the potential energy of SO(2) is lost. This paper presents a novel ultraviolet (UV) photolytic process for production of hydrogen from aqueous Na(2)SO(3) solutions. The results show that the quantum efficiency of hydrogen production can reach 14.4% under illumination from a low pressure mercury lamp. The mechanism occurs via two competing reaction pathways that involve oxidation of SO(3)(2-) to SO(4)(2-) directly and through the dithionate (S(2)O(6)(2-)) ion intermediate. The first route becomes dominant once a photostationary state for S(2)O(6)(2-) is established. The initial pH of Na(2)SO(3) solution plays an important role in determining both the hydrogen production rate and the final products of the photolytic oxidation. At initial solution pH of 9.80 Na(2)SO(3) photo-oxidation generates Na(2)SO(4) as the final reaction product, while Na(2)S(2)O(6) is merely a reaction intermediate. The highest hydrogen production rate occurs when the initial solution pH is 7.55. Reduction in the initial solution pH to 5.93 results in disproportionation of HSO(3)(-) to elemental sulfur and SO(4)(2-) but no hydrogen production.

  11. Aqueous Solution Vessel Thermal Model Development II

    SciTech Connect

    Buechler, Cynthia Eileen

    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.

  12. RECOVERY OF ACTINIDES FROM AQUEOUS NITRIC ACID SOLUTIONS

    DOEpatents

    Ader, M.

    1963-11-19

    A process of recovering actinides is presented. Tetravalent actinides are extracted from rare earths in an aqueous nitric acid solution with a ketone and back-extracted from the ketone into an aqueous medium. The aqueous actinide solution thus obtained, prior to concentration by boiling, is sparged with steam to reduce its ketone to a maximum content of 3 grams per liter. (AEC)

  13. Speciation in aqueous solutions of nitric acid.

    PubMed

    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.

  14. Synthesis of Polyoxovanadates from Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Bouhedja, L.; Steunou, N.; Maquet, J.; Livage, J.

    2001-12-01

    Polyoxovanadates have been synthesized from aqueous solutions of VV in the presence of inorganic Na+ and organic [N(CH3)4]+ cations. Decavanadate crystals are precipitated at room temperature around pH 7, whereas layered compounds Na[V3O8].H2O and N(CH3)4[V4O10] are formed at the same pH under hydrothermal conditions. In situ51V NMR experiments show that upon heating solute decavanadate species are progressively transformed into cyclic metavanadates [V4O12]4-. A chemical mechanism is suggested for the formation of these layered vanadium oxides. It involves the ring-opening polymerization of cyclic metavanadates arising from co-ordination expansion favored by protonation or vanadium reduction.

  15. Multistep nucleation of nanocrystals in aqueous solution

    NASA Astrophysics Data System (ADS)

    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.

  16. Sound absorption in nonelectrolyte aqueous solutions

    NASA Astrophysics Data System (ADS)

    Endo, Harumi; Honda, Kazuyuki

    2001-10-01

    We indicate that the curve fitting for Debye-type relaxation spectrum of sound absorption (SA) cannot sufficiently account for the observed data of nonelectrolyte aqueous solutions (NEAS). To solve these problems, we introduce the distribution function of relaxation time [DFRT, F(τ)] from a diffusion equation of concentration fluctuations using the fluctuation dispersion theory. The SA expression is described by four-adjustable parameters. By use of the mixtures of 1-propanol, t-butanol, and monobutyl triethylene glycol with water, our calculation of SA shows the best fit between the observed and calculated curves, compared with other models. It was found that at lower frequencies the SA behaves as the square root of frequency. The approximate expression of DFRT was expressed in terms of a power law of relaxation time, F(τ)∝τ-γ, which is the same as the expression of dielectric relaxation by Matsumoto and Higashi. Our exponent (γ) of relaxation time is varied from 5/2 in hydrophilic solutes to 3/2 in hydrophobic solutes. The power (γ) of relaxation time was regarded as a parameter to explain the hydrophobic and hydrophilic in the dissolved states of a solute. Our SA expression of γ=5/2 for solutes of a small correlation length leads to that of Romanov-Solov'ev, where the value of 5/2 is that of the Debye distribution for the relaxation time in the Romanov-Solov'ev model.

  17. Spontaneous precipitation of struvite from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Bouropoulos, Nicolaos Ch; Koutsoukos, Petros G.

    2000-06-01

    The kinetics of the spontaneous precipitation of struvite was investigated in aqueous supersaturated solutions containing stoichiometric concentrations of Mg 2+, NH 4+ and PO 43- ions, ionic strenght 0.15 M NaCl and at 25°C in a batch, stirred reactor at constant supersaturation. The induction times preceding the onset of struvite precipitation and the initial rates of precipitation were measured directly from the traces of titrants added in order to maintain the solution supersaturation. From the measurement of the induction times as a function of the solution supersaturation, the stability diagram of the system was constructed. In all cases the only solid-phase forming was identified as struvite. Kinetic analysis of the rates, which depended strongly on the solution supersaturation yielding a second-order dependence, suggested a surface diffusion mechanism. The precipitated struvite crystals showed a high negative charge which increased as a function of the solution pH while the presence of magnesium ions affected the microelectrophoretic mobility of struvite dispersions yielding an isoelectric point at pMg of 1.75.

  18. Uranyl fluoride luminescence in acidic aqueous solutions

    SciTech Connect

    Beitz, J.V.; Williams, C.W.

    1996-08-01

    Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269 {+-} 0.006 ms, was observed from uranyl in 1 M HF + 1 M HClO{sub 4} at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to UO{sub 2}F{sub 2}. Studies on the effect of added LiNO{sub 3} or Na{sub 2}WO{sub 4}{center_dot}2H{sub 2}O showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the UF{sub 6} content of WF{sub 6} gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure WF{sub 6}.

  19. Aqueous Solutions of Ionic Liquids: Microscopic Assembly.

    PubMed

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

    2016-02-03

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

  20. Infrared spectra of cesium chloride aqueous solutions

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2000-10-01

    The aqueous solutions of CsCl were studied at room temperature by infrared (IR) spectroscopy in the entire solubility range, 0-1200 g/L, using attenuated total reflection (ATR) sampling. The influence of anomalous dispersion on the IR-ATR spectra was evaluated by calculating the imaginary refractive index, k(ν), of each sample. Factor analysis (FA) was used to determine the number and abundance of species in the solutions. FA applied to both k(ν) spectra and IR-ATR spectra produced two principal spectra with a similar abundance of species. This result indicates that, even at high salt concentration, the optical effects do not influence the chemical analysis of IR-ATR spectra. The spectral modifications related to the salt concentrations are mainly first order. Second order effects were observed, but being weak, were not investigated. The two principal spectra are related to the two species present in the solution: pure water and CsCl-solvated water. From the latter, 2.8±0.4 water molecules were calculated to be associated with each close-bound Cs+/Cl- ion pair. In the case of KCl and NaCl aqueous solutions, both of which showed the same number of species, the number of water molecules associated to an ion pair was 5.0±0.4. That the latter number is different from that of CsCl indicates that the interaction between water molecules and ion pairs is different when cation Na or K in the chloride salt is replaced by Cs.

  1. Models of globular proteins in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Wentzel, Nathaniel James

    Protein crystallization is a continuing area of research. Currently, there is no universal theory for the conditions required to crystallize proteins. A better understanding of protein crystallization will be helpful in determining protein structure and preventing and treating certain diseases. In this thesis, we will extend the understanding of globular proteins in aqueous solutions by analyzing various models for protein interactions. Experiments have shown that the liquid-liquid phase separation curves for lysozyme in solution with salt depend on salt type and salt concentration. We analyze a simple square well model for this system whose well depth depends on salt type and salt concentration, to determine the phase coexistence surfaces from experimental data. The surfaces, calculated from a single Monte Carlo simulation and a simple scaling argument, are shown as a function of temperature, salt concentration and protein concentration for two typical salts. Urate Oxidase from Asperigillus flavus is a protein used for studying the effects of polymers on the crystallization of large proteins. Experiments have determined some aspects of the phase diagram. We use Monte Carlo techniques and perturbation theory to predict the phase diagram for a model of urate oxidase in solution with PEG. The model used includes an electrostatic interaction, van der Waals attraction, and a polymerinduced depletion interaction. The results agree quantitatively with experiments. Anisotropy plays a role in globular protein interactions, including the formation of hemoglobin fibers in sickle cell disease. Also, the solvent conditions have been shown to play a strong role in the phase behavior of some aqueous protein solutions. Each has previously been treated separately in theoretical studies. Here we propose and analyze a simple, combined model that treats both anisotropy and solvent effects. We find that this model qualitatively explains some phase behavior, including the existence of

  2. Terahertz absorption of dilute aqueous solutions.

    PubMed

    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

  3. Italian ryegrass for the phytoremediation of solutions polluted with terbuthylazine.

    PubMed

    Mimmo, Tanja; Bartucca, Maria Luce; Del Buono, Daniele; Cesco, Stefano

    2015-01-01

    The phytoextraction capacity of Italian ryegrass (Lolium multiflorum L.) to remove terbuthylazine (TBA) from aqueous solution has been assessed using a plant-based biotest (RHIZOtest). Three TBA concentrations (0.5, 1.0 and 2.0 mg L(-1)) were chosen to evaluate the tolerance capacity of the ryegrass. Even though the treatments negatively affected plants, they were able to remove up to 30-40% of TBA. In addition, some enzymatic activities involved in the response to TBA-induced stress were determined. Glutathione S-transferase (GST) has been activated with a TBA-dose dependent trend; ascorbate peroxidase (APX) activities have been induced within the first hours after the treatments, followed by decreases or disappearance in plants exposed to two higher dosages. In conclusion, this case-study highlights that the combination of ryegrass and RHIZOtest resulted to be effective in the remediation of aqueous solutions polluted by TBA.

  4. Phase behavior of DODAB aqueous solution

    SciTech Connect

    Voronov, V. P.; Kuryakov, V. N.; Muratov, A. R.

    2012-12-15

    Phase behavior of DODAB aqueous solution, prepared without sonication, was studied by adiabatic scanning calorimetry. Measurements revealed four phase transitions with the temperatures 35.2, 39.6, 44.6, and 52.4 Degree-Sign C at heating and one transition at the temperature 40.4 Degree-Sign C at cooling. The first three transitions at heating occur in unilamellar vesicles. The first and third transitions correspond to the subgel-gel and gelliquid phase transitions, corresponding enthalpy jumps are equal to 33 and 49 kJ/mol. The second transition appears after some aging and is similar to gel-ripple phase transition in a DPPC solution, with the enthalpy jump under the transition exceeding 7.4 kJ/mol. The transition occurs in unilamellar vesicles. The transition at the temperature 52.4 Degree-Sign C occurs in another subsystem of the solution, which we believe to be multilamellar vesicles. The enthalpy jump at this transition is equal to 97 kJ/mol, and data analysis suggests that this is a subgel-liquid transition. The phase transition at cooling is the liquid-gel transition in unilamellar vesicles. During the measurements, a slow evolution of the solution occurs, consisting in a change of concentrations of unilamellar and multilamellar vesicles. This transformation mainly occurs at low temperatures.

  5. Heterogeneous nucleation of aspartame from aqueous solutions

    NASA Astrophysics Data System (ADS)

    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.

  6. Functionalized polymers for binding to solutes in aqueous solutions

    DOEpatents

    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. Process for decomposing nitrates in aqueous solution

    DOEpatents

    Haas, Paul A.

    1980-01-01

    This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.degree.-200.degree. C.

  8. Pulse radiolysis of epicatechin in aqueous solution

    NASA Astrophysics Data System (ADS)

    Li, Fengmei; Fang, Xingwang

    1998-06-01

    Pulse radiolysis of epicatechin in aqueous solution has been done to investigate the reactions of epicatechin derived phenoxy radical (EpO) at neutral pH. EpO was generated by N 3 reacting toward EpOH, the rate constant was measured to be 3 × 10 8 dm 3 mol -1 s -1. The biomolecular termination of EpO is rather slow ((2 k < × 10 6 dm 3 mol -1 s -1) and results in products exhibiting strong visible absorption around 450 nm. No reactions have been observed for EpO with O 2 and O 2 in the time scale of pulse radiolysis (0.01 s), suggesting the bimolecular rate constant are less than 10 4 and 5 × 10 6 dm 3 mol -1 s -1, respectively.

  9. Abiotic transformation of DDT in aqueous solutions.

    PubMed

    Pirnie, Erica F; Talley, Jeffrey W; Hundal, Lakhwinder S

    2006-11-01

    Significant concentrations of chlorinated pesticides such as 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its two main transformation products, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) are still present in soil and sediment systems more than 30 years after DDT use was banned in the United States. DDT enters waterways via the runoff from industrial point sources, agricultural lands and atmospheric deposition. We evaluated zero-valent iron (Fe(0)), ferrous sulfide (FeS), as well as combining them with hydrogen peroxide (H(2)O(2)) as viable treatment technologies for degrading DDT in an aqueous solution. Treatment of DDT with Fe(0) and FeS resulted in approximately 88% and 56% transformation of DDT within 150h, respectively. DDE production was insignificant in all systems. The DDT removal was slower with FeS than with Fe(0), but the amounts of DDD and DDE produced did not exceed baseline. Treatment with a 1:1 mixture of Fe(0)-FeS removed about 95% of the added mass of DDT within 4days and generated significant amounts of DDD and minor amounts of DDMU. When small amounts of H(2)O(2) were introduced halfway through the Fe(0) and FeS treatment times, the mass of DDT decreased by 87% and 96%, respectively, within 2days. Our results demonstrate that mixtures of Fe(0)-FeS in combination with H(2)O(2) can be used for rapid and efficient removal of DDT from aqueous solutions.

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

    PubMed

    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.

  11. Catalyzed reduction of nitrate in aqueous solutions

    SciTech Connect

    Haas, P.A.

    1994-08-01

    Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH{sub 3}, hydrazine, or organic compounds containing oxygen would be advantageous for reduction of nitrate in sodium nitrate solutions. Objective of this seed money study was to determine minimum conditions for reduction. Proposed procedure was batchwise heating of aqueous solutions in closed vessels with monitoring of temperatures and pressures. A simple, convenient apparatus and procedure were demonstrated for observing formation of gaseous products and collecting samples for analyses. The test conditions were 250{degree}C and 1000 psi max. Any useful reduction of sodium nitrate to sodium hydroxide as the primary product was not found. The nitrate present at pHs < 4 as HNO{sub 3} or NH{sub 4}NO{sub 3} is easily decomposed, and the effect of nitromethane at these low pHs was confirmed. When acetic acid or formic acid was added, 21 to 56% of the nitrate in sodium nitrate solutions was reduced by methanol or formaldehyde. With hydrazine and acetic acid, 73 % of the nitrate was decomposed to convert NaNO{sub 3} to sodium acetate. With hydrazine and formic acid, 36% of the nitrate was decomposed. If these products are more acceptable for final disposal than sodium nitrate, the reagents are cheap and the conversion conditions would be practical for easy use. Ammonium acetate or formate salts did not significantly reduce nitrate in sodium nitrate solutions.

  12. Photochemistry of norharmane in aqueous solution.

    PubMed

    Gonzalez, M Micaela; Salum, M Laura; Gholipour, Yousef; Cabrerizo, Franco M; Erra-Balsells, Rosa

    2009-08-01

    The photochemistry of norharmane (9H-pyrido[3,4-b]indole) in acidic (pH 5.0+/-0.1) and alkaline (pH 10.0+/-0.1) aqueous solutions was studied. The photochemical reactions were monitored by TLC, UV/VIS absorption spectroscopy, high-performance liquid chromatography (HPLC), electronic ionization-mass spectrometry (EI-MS), UV-laser desorption/ionization-time of flight-mass spectrometry (UV-LDI-TOF-MS) and an enzymatic method for H2O2 determination. The neutral (nHoN) and the protonated (nHoH+) forms of norharmane irradiated under Ar atmosphere were photostable, but they suffered a photochemical transformation in the presence of O2, yielding as photoproducts norharmane dimers, trimers and tetramers. nHoN shown to be more photostable than nHoH+. The nHoH+ and nHoN consumption quantum yields were 1.82x10(-3) and 0.51x10(-3), respectively, and the mechanisms involved in its photochemistry are discussed. H2O2 and singlet oxygen (1O2) were also detected and quantified in irradiated solutions of norharmane, and their role in the photochemistry of norharmane is discussed.

  13. Stability of cefozopran hydrochloride in aqueous solutions.

    PubMed

    Zalewski, Przemysław; Skibiński, Robert; Paczkowska, Magdalena; Garbacki, Piotr; Talaczyńska, Alicja; Cielecka-Piontek, Judyta; Jelińska, Anna

    2016-01-01

    The influence of pH on the stability of cefozopran hydrochloride (CZH) was investigated in the pH range of 0.44-13.00. Six degradation products were identified with a hybrid ESI-Q-TOF mass spectrometer. The degradation of CZH as a result of hydrolysis was a pseudo-first-order reaction. As general acid-base hydrolysis of CZH was not occurred in the solutions of hydrochloric acid, sodium hydroxide, acetate, borate and phosphate buffers, kobs = kpH because specific acid-base catalysis was observed. Specific acid-base catalysis of CZH consisted of the following reactions: hydrolysis of CZH catalyzed by hydrogen ions (kH+), hydrolysis of dications (k1H2O), monocations (k2H2O) and zwitter ions (k3H2O) and hydrolysis of zwitter ions (k1OH-) and monoanions (k2OH-) of CZH catalyzed by hydroxide ions. The total rate of the reaction was equal to the sum of partial reactions: [Formula: see text]. CZH similarly like other fourth generation cephalosporin was most stable at slightly acidic and neutral pH and less stable in alkaline pH. The cleavage of the β-lactam ring resulting from a nucleophilic attack on the carbonyl carbon in the β-lactam moiety is the preferred degradation pathway of β-lactam antibiotics in aqueous solutions.

  14. Modification of polystyrene surface in aqueous solutions.

    PubMed

    Mielczarski, J A; Jeyachandran, Y L; Mielczarski, E; Rai, B

    2011-10-15

    Herein, we report our analysis of the surface modification of polystyrene (PS) when treated under ambient conditions with a common biological buffer such as phosphate buffered saline (PBS) or aqueous solutions of the ionic constituents of PBS. Attenuated total reflection Fourier transform infrared spectroscopy was used for the analysis because the resultant spectra are very sensitive to minor changes in the chemical and structural properties of PS films. In addition, ultraviolet-visible spectroscopy was applied to characterize the surface modifications of PS. Treatment with PBS resulted in the most significant chemical and structural surface modifications of the PS films, as compared with each of the solutions of the constituents of PBS, which were tested separately. A multistep mechanism for the wet modification of PS is discussed. We postulate that the observed surface modifications are the result of photo-oxidation/reduction, swelling, and conformational changes and re-arrangement of the polymer chain. The resultant surface modifications could be similar to those produced by commonly used dry processes such as plasma treatments and electron, ion or ultraviolet irradiation. We found that the modifications that occurred in PBS were more stable than those initiated by dry processes. The formation of active groups on the surface of PS can be controlled by adsorption of bovine serum albumin or thermal annealing of PS before PBS treatment. This approach provides a simple and efficient method for the surface modification of PS for biomedical applications. Copyright © 2011. Published by Elsevier Inc.

  15. Removal of copper from aqueous solution using perlite

    NASA Astrophysics Data System (ADS)

    Tanaydin, Mehmet Kayra; Tanaydin, Zümra Bakici; Ince, Muharrem; Demırkiran, Nizamettin

    2017-04-01

    The wastewaters containing organic and inorganic pollutants after many industrial processes such as metal plating, mining, textile, alloy, battery and industrial chemicals, are often discharged to environment. Heavy metals among these pollutants have highly stable, toxic, non-degradable and carcinogenic characters. They affect not only ecological system, but also human health and many life forms. Therefore, these contaminants should be eliminated or reduced to allowable levels before releasing to environment. Most of heavy metals have toxic character even at low concentrations of about 0.1-0.3 ppm. Treatment technologies such as filtration, ion exchange, precipitation, electrodeposition, reverse osmosis, sedimentation, and adsorption have been applied for removal of heavy metals from aqueous solutions. Adsorption is one of the most common and widely applied methods to eliminate the metal ions from waste solutions because of its simplicity and cost effectiveness. Activated carbon, clay minerals, ion exchange resins and various agricultural residues can be used as adsorbent materials in this process [1-3].

  16. Formation of hydroxyapatite in various aqueous solutions

    NASA Astrophysics Data System (ADS)

    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

  17. A Polymer "Pollution Solution" Classroom Activity.

    ERIC Educational Resources Information Center

    Helser, Terry L.

    1996-01-01

    Explains an approach to presenting polymer chemistry to nonmajors that employs polystyrene foam, foam peanuts made from water soluble starch, and water soluble plastic bags. Students are presented with a pollution scenario and are guided to the discovery of solutions. (DDR)

  18. A Polymer "Pollution Solution" Classroom Activity.

    ERIC Educational Resources Information Center

    Helser, Terry L.

    1996-01-01

    Explains an approach to presenting polymer chemistry to nonmajors that employs polystyrene foam, foam peanuts made from water soluble starch, and water soluble plastic bags. Students are presented with a pollution scenario and are guided to the discovery of solutions. (DDR)

  19. Thermal properties of ethylene glycol aqueous solutions.

    PubMed

    Baudot, A; Odagescu, V

    2004-06-01

    Preventing ice crystallization by transforming liquids into an amorphous state, vitrification can be considered as the most suitable technique allowing complex tissues, and organs cryopreservation. This process requires the use of rapid cooling rates in the presence of cryoprotective solutions highly concentrated in antifreeze compounds, such as polyalcohols. Many of them have already been intensively studied. Their glass forming tendency and the stability of their amorphous state would make vitrification a reality if their biological toxicity did not reduce their usable concentrations often below the concentrations necessary to vitrify organs under achievable thermal conditions. Fortunately, it has been shown that mixtures of cryoprotectants tend to reduce the global toxicity of cryoprotective solutions and various efficient combinations have been proposed containing ethanediol. This work reports on the thermal properties of aqueous solutions with 40, 43, 45, 48, and 50% (w/w) of this compound measured by differential scanning calorimetry. The glass forming tendency and the stability of the amorphous state are evaluated as a function of concentration. They are given by the critical cooling rates v(ccr)above which ice crystallization is avoided, and the critical warming rates v(cwr) necessary to prevent ice crystallization in the supercooled liquid state during rewarming. Those critical rates are calculated using the same semi-empirical model as previously. This work shows a strong decrease of averaged critical cooling and warming rates when ethanediol concentration increases, V(ccr) and V(cwr) = 1.08 x 10 (10) K/min for 40% (w/w) whereas V(ccr) = 11 and V(cwr) = 853 K/min for 50% (w/w). Those results are compared with the corresponding properties of other dialcohols obtained by the same method. Ethylene glycol efficiency is between those of 1,2-propanediol and 1,3-propanediol.

  20. Ultrasonic degradation of sulfadiazine in aqueous solutions.

    PubMed

    Lastre-Acosta, Arlen Mabel; Cruz-González, Germán; Nuevas-Paz, Lauro; Jáuregui-Haza, Ulises Javier; Teixeira, Antonio Carlos Silva Costa

    2015-01-01

    Advanced oxidation methods, like ultrasound (US), are a promising technology for the degradation of emerging pollutants in water matrices, such as sulfonamide antibiotics. Nevertheless, few authors report the degradation of sulfonamides by high-frequency US (>100 kHz), and limited information exist concerning the use of ultrasonic-driven processes in the case of sulfadiazine (SDZ). In this study, SDZ degradation was investigated with the aim to evaluate the influence of initial concentration, pH and US frequency, and power. Ultrasonic frequencies of 580, 862, and 1,142 kHz at different power values and SDZ initial concentrations of 25, 50, and 70 mg L(-1) were used. The results show that SDZ degradation followed pseudo first-order reaction kinetics with k values and percent removals decreasing for increasing solute initial concentration. Higher SDZ percent removals and removal rates were observed for the lowest operating frequency (580 kHz), higher dissipated power, and in slightly acidic solution (pH 5.5). Addition of the radical scavenger n-butanol confirmed that hydroxyl radical-mediated reactions at the interface of the cavitation bubbles are the prevailing degradation mechanism, which is directly related to the pKa-dependent speciation of SDZ molecules. Finally, addition of H2O2 had a detrimental effect on SDZ degradation, whereas the addition of the Fenton reagent showed a positive effect, revealing to be a promising alternative for the removal of sulfadiazine.

  1. PROCESS OF SEPARATING URANIUM FROM AQUEOUS SOLUTION BY SOLVENT EXTRACTION

    DOEpatents

    Warf, J.C.

    1958-08-19

    A process is described for separating uranium values from aqueous uranyl nitrate solutions. The process consists in contacting the uramium bearing solution with an organic solvent, tributyl phosphate, preferably diluted with a less viscous organic liquida whereby the uranyl nitrate is extracted into the organic solvent phase. The uranvl nitrate may be recovered from the solvent phase bv back extracting with an aqueous mediuin.

  2. Stabilizing the viscosity of an aqueous solution of polysaccharide polymer

    SciTech Connect

    Wellington, S.L.

    1980-08-19

    In an oil recovery process in which an aqueous solution thickened with a water-soluble anionic polysaccharide polymer (Xanthan gum polymer) is injected into a subterranean reservoir, the stability of the solution viscosity is improved by deoxygenating the aqueous liquid and then adding a sulfurcontaining antioxidant, a readily oxidizable water-soluble alcohol or glycol and the xanthan gum polymer.

  3. Structure of aqueous sodium perchlorate solutions.

    PubMed

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

    2008-12-04

    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

  4. Component dynamics in polyvinylpyrrolidone concentrated aqueous solutions

    NASA Astrophysics Data System (ADS)

    Busselez, Rémi; Arbe, Arantxa; Cerveny, Silvina; Capponi, Sara; Colmenero, Juan; Frick, Bernhard

    2012-08-01

    2H-nuclear magnetic resonance (NMR) and neutron scattering (NS) on isotopically labelled samples have been combined to investigate the structure and dynamics of polyvinylpyrrolidone (PVP) aqueous solutions (4 water molecules/monomeric unit). Neutron diffraction evidences the nanosegregation of polymer main-chains and water molecules leading to the presence of water clusters. NMR reveals the same characteristic times and spectral shape as those of the slower process observed by broadband dielectric spectroscopy in this system [S. Cerveny et al., J. Chem. Phys. 128, 044901 (2008)], 10.1063/1.2822332. The temperature dependence of such relaxation time crosses over from a cooperative-like behavior at high temperatures to an Arrhenius behavior at lower temperatures. Below the crossover, NMR features the spectral shape as due to a symmetric distribution of relaxation times and the underlying motions as isotropic. NS results on the structural relaxation of both components-isolated via H/D labeling-show (i) anomalously stretched and non-Gaussian functional forms of the intermediate scattering functions and (ii) a strong dynamic asymmetry between the components that increases with decreasing temperature. Strong heterogeneities associated to the nanosegregated structure and the dynamic asymmetry are invoked to explain the observed anomalies. On the other hand, at short times the atomic displacements are strongly coupled for PVP and water, presumably due to H-bond formation and densification of the sample upon hydration.

  5. Photochemistry of dihydrobiopterin in aqueous solution.

    PubMed

    Vignoni, Mariana; Cabrerizo, Franco M; Lorente, Carolina; Claparols, Catherine; Oliveros, Esther; Thomas, Andrés H

    2010-02-21

    Dihydrobiopterin (H(2)Bip) and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails. The photochemistry of H(2)Bip was studied in neutral aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC and enzymatic methods for hydrogen peroxide (H(2)O(2)) determination. Photoproducts were analyzed by means of electrospray ionization mass spectrometry. Under anaerobic conditions, excitation of H(2)Bip leads to the formation of at least two isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. This reaction takes place from the singlet excited state of the reactant. To the best of our knowledge, this is the first time that the photodimerization of a dihydropterin is reported. In the presence of air, the dimers are again the main photoproducts at the beginning of the reaction, but a small proportion of the reactant is converted into Bip. As the reaction proceeds and enough Bip accumulates in the solution, a photosensitized process starts, where Bip photoinduces the oxidation of H(2)Bip to Bip, and H(2)O(2) is formed. As a consequence, the rates of H(2)Bip consumption and Bip formation increase as a function of irradiation time, resulting in an autocatalytic photochemical process. In this process, Bip in its triplet excited state reacts with the ground state of H(2)Bip. The mechanisms involved are analyzed and the biological implications of the results are discussed.

  6. Note on the stability of mefloquine hydrochloride in aqueous solution

    PubMed Central

    Reber-Liske, Rosemaria

    1983-01-01

    Using Desjardins' technique for the testing of antimalarials against Plasmodium falciparum in vitro, a 4-year-old solution of mefloquine in water (10-3 mol/litre) was compared with a freshly prepared solution. The results showed that the two solutions had almost identical activity. There was no evidence for any instability of mefloquine in aqueous solution. PMID:6349842

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  8. SEPARATION OF PLUTONIUM FROM AQUEOUS SOLUTIONS BY ION-EXCHANGE

    DOEpatents

    Schubert, J.

    1958-06-01

    A process is described for the separation of plutonium from an aqueous solution of a plutonium salt, which comprises adding to the solution an acid of the group consisting of sulfuric acid, phosphoric acid, and oxalic acid, and mixtures thereof to provide an acid concentration between 0.0001 and 1 M, contacting the resultant solution with a synthetic organic anion exchange resin, and separating the aqueous phase and the resin which contains the plutonium.

  9. Reverse osmosis separation of radium from dilute aqueous solutions

    SciTech Connect

    Subramanian, K.S.; Sastri, V.S.

    1980-03-01

    Porous cellulose acetate membranes obtained from Osmonics Inc. were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with aqueous sodium chloride solution as the reference system. Reverse osmosis separation behavior of radium-226 as nitrate, chloride, and sulfate salts was studied. Reverse osmosis method of removing radium-226 from aqueous solutions has been compared with other methods, and it has been shown to be one of the best methods for alleviating radium contamination problems.

  10. ELECTROCHEMICAL DECHLORINATIONOF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

    EPA Science Inventory

    This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-CI BP) in aqueous environment using palladium modified granular graphite electrodes. 2-CI BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

  11. ELECTROCHEMICAL DECHLORINATIONOF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

    EPA Science Inventory

    This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-CI BP) in aqueous environment using palladium modified granular graphite electrodes. 2-CI BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

  12. Reductive dehalogenation of bromoform in aqueous solution.

    PubMed

    Betterton, E A; Arnold, R G; Kuhler, R J; Santo, G A

    1995-06-01

    The hybrid semiconducter-macrocycle catalyst TiO2-cobalt phthalocyanine promotes the solar photolysis of aqueous bromoform under anaerobic conditions. The major decomposition products are dibromoethane and HBr. Bromomethane and methane were produced only after prolonged photolysis (30 hr). Acetone, derived from added 2-propanol, was the only observed oxidation product. Preliminary experiments showed that electrolytic reduction of aqueous carbon tetrachloride at a vitamin B12-modified silver electrode produced the expected lower homologues but with surprisingly high yields of methane.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Degradation of 2-mercaptobenzothiazole in aqueous solution by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Bao, Qiburi; Chen, Lujun; Tian, Jinping; Wang, Jianlong

    2014-10-01

    Industrial wastewaters containing 2-mercaptobenzothiazole (MBT), a widely used chemical additive, usually cannot be treated properly by conventional biological methods, thus cause an environmental risk. Ionizing radiation was proposed as a method for abatement of several refractory pollutants from water. The paper investigated MBT degradation using irradiation technology. The decomposition kinetics was described, and the transformation and the change of biodegradability were discussed. The results of gamma radiation experiments on MBT-containing aqueous solutions indicated that reactive radicals resulting from water radiolysis effectively degrade MBT and improve the biodegradability of the solutions. At a 20 mg/L MBT concentration, the removal of 82% was achieved at the absorbed dose of 1.2 kGy. The results of specific oxygen uptake rate (SOUR) test showed that MBT was decomposed into biodegradable products, after irradiation at 20 kGy. Radicals attacked the sulfur atoms of the studied molecule leading to the release of sulfate ions, but the mineralization of organic carbons was rather weak. Initial concentration significantly affected the degradation efficacy of MBT by gamma radiation.

  15. Quantitative ionization energies and work functions of aqueous solutions.

    PubMed

    Olivieri, Giorgia; Goel, Alok; Kleibert, Armin; Cvetko, Dean; Brown, Matthew A

    2016-10-26

    Despite the ubiquitous nature of aqueous solutions across the chemical, biological and environmental sciences our experimental understanding of their electronic structure is rudimentary-qualitative at best. One of the most basic and seemingly straightforward properties of aqueous solutions-ionization energies-are (qualitatively) tabulated at the water-air interface for a mere handful of solutes, and the manner in which these results are obtained assume the aqueous solutions behave like a gas in the photoelectron experiment (where the vacuum levels of the aqueous solution and of the photoelectron analyzer are equilibrated). Here we report the experimental measure of a sizeable offset (ca. 0.6 eV) between the vacuum levels of an aqueous solution (0.05 M NaCl) and that of our photoelectron analyzer, indicating a breakdown of the gas-like vacuum level alignment assumption for the aqueous solution. By quantifying the vacuum level offset as a function of solution chemical composition our measurements enable, for the first time, quantitative determination of ionization energies in liquid solutions. These results reveal that the ionization energy of liquid water is not independent of the chemical composition of the solution as is usually inferred in the literature, a finding that has important ramifications as measured ionization energies are frequently used to validate theoretical models that posses the ability to provide microscopic insight not directly available by experiment. Finally, we derive the work function, or the electrochemical potential of the aqueous solution and show that it too varies with the chemical composition of the solution.

  16. Detection of copper ions from aqueous solutions using layered double hydroxides thin films deposited by PLD

    NASA Astrophysics Data System (ADS)

    Vlad, A.; Birjega, R.; Matei, A.; Luculescu, C.; Nedelcea, A.; Dinescu, M.; Zavoianu, R.; Pavel, O. D.

    2015-10-01

    Layered double hydroxides (LDHs) thin films with Mg-Al were deposited using pulsed laser deposition (PLD) technique. We studied the ability of our films to detect copper ions in aqueous solutions. Copper is known to be a common pollutant in water, originating from urban and industrial waste. Clay minerals, including layered double hydroxides (LDHs), can reduce the toxicity of such wastes by adsorbing copper. We report on the uptake of copper ions from aqueous solution on LDH thin films obtained via PLD. The obtained thin films were characterized using X-ray Diffraction, Atomic Force Microscopy, and Scanning Electron Microscopy with Energy Dispersive X-ray analysis. The results in this study indicate that LDHs thin films obtained by PLD have potential as an efficient adsorbent for removing copper from aqueous solution.

  17. Singlet Oxygen in Aqueous Solution: A Lecture Demonstration

    ERIC Educational Resources Information Center

    Shakhashiri, Bassam Z.; Williams, Lloyd G.

    1976-01-01

    Describes a demonstration that illustrates the red chemiluminescence due to singlet molecular oxygen that can be observed when aqueous solutions of hypochlorite ion and hydrogen peroxide are mixed. (MLH)

  18. Singlet Oxygen in Aqueous Solution: A Lecture Demonstration

    ERIC Educational Resources Information Center

    Shakhashiri, Bassam Z.; Williams, Lloyd G.

    1976-01-01

    Describes a demonstration that illustrates the red chemiluminescence due to singlet molecular oxygen that can be observed when aqueous solutions of hypochlorite ion and hydrogen peroxide are mixed. (MLH)

  19. Trace hydrazines in aqueous solutions accurately determined by gas chromatography

    NASA Technical Reports Server (NTRS)

    Welz, E. A., Jr.

    1967-01-01

    Trace amounts of hydrazines in aqueous solutions can be determined by using polythyleneimine /PEI/ in conjunction with the gas chromatographic column. The PEI specifically retains water without altering the separability or elution order of the hydrazine and associated constituents.

  20. Extraction of ethylene glycol from aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Butyrskaya, E. V.; Belyakova, N. V.; Rozhkova, M. V.; Nechaeva, L. S.

    2012-11-01

    A method is proposed for extracting ethylene glycol from aqueous salt solutions by dialysis through ion-exchange membranes, based on the Donnan exclusion of the electrolyte. Dialysis is performed in the continuous and batch modes. It is found that the batch mode of dialysis is more effective for extracting ethylene glycol from its aqueous salt solutions. The effect of the ionic form of the membrane on ethylene glycol fluxes is explained through computer simulation.

  1. Scanning force microscopy under aqueous solutions.

    PubMed

    Bustamante, C; Rivetti, C; Keller, D J

    1997-10-01

    Merely ten years after its invention, the scanning force microscope is becoming a powerful method to investigate the structure and dynamics of biological molecules under aqueous environments. From the visualization of transcription in real time to the mechanical manipulation of individual proteins, the advances made during the past year open up a vast number of exciting applications of this technique in biology.

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

    PubMed Central

    Finch, Amethist S.; Anton, Christopher M.; Jacob, Christina M.; Proctor, Thomas J.; Stratis-Cullum, Dimitra N.

    2012-01-01

    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.

  3. Extracting alcohols from aqueous solutions. [USDOE patent application

    DOEpatents

    Compere, A.L.; Googin, J.M.; Griffith, W.L.

    1981-12-02

    The objective is to provide an efficient process for extracting alcohols in aqueous solutions into hydrocarbon fuel mixtures, such as gasoline, diesel fuel and fuel oil. This is done by contacting an aqueous fermentation liquor with a hydrocarbon or hydrocarbon mixture containing carbon compounds having 5-18 carbon atoms, which may include gasoline, diesel fuel or fuel oil. The hydrocarbon-aqueous alcohol solution is then mixed with one or more of a group of polyoxyalkylene polymers to extract the alcohol into the hydrocarbon fuel-polyoxyalkylene polymer mixture.

  4. Urban Air Pollution from Ethanol (E85) in the Presence of Aqueous Aerosols and Fog

    NASA Astrophysics Data System (ADS)

    Ginnebaugh, D. L.; Jacobson, M. Z.

    2010-12-01

    This is a study to examine the effect of ethanol (E85) versus gasoline on urban air pollution in the presence of aqueous aerosols and fog. In previous work, we analyzed the temperature-dependence of ethanol and gasoline exhaust chemistry and its impact on urban air pollution considering only gas-phase chemistry. We used the near-explicit Master Chemical Mechanism (MCM, version 3.1, LEEDS University) with the SMVGEAR II chemical ordinary differential solver to provide the speed necessary to simulate explicit chemistry. The MCM has over 13,500 organic reactions and 4,600 species. SMVGEAR II is a sparse-matrix Gear solver that reduces the computation time significantly while maintaining any specified accuracy. We found that the average ozone concentrations through the range of temperatures tested could be higher with E85 than with gasoline by up to 8 parts per billion volume (ppbv) at room temperature but much higher at cold temperatures and low sunlight (winter conditions) for a region with a high nitrogen oxide (NOx) to non-methane organic gases (NMOG) ratio. We also found that the solution to chemistry in a 3-D urban airshed model was practical. We now extend our study to include aqueous chemistry in the presence of aerosols and fog. We combine the Chemical Aqueous Phase Radical Mechanism, CAPRAM 3.0 with the MCM 3.1 and gas-particle transfer in box model calculations. CAPRAM treats aqueous phase chemistry among 390 species and 829 reactions (including 51 gas-to-aqueous phase reactions). We investigate the impact aqueous reactions have on unburned ethanol and acetaldehyde mixing ratios in the atmosphere in particular because acetaldehyde is an ozone precursor and carcinogen, and aqueous oxidation has potential to speed the conversion of unburned ethanol to acetaldehyde. Acetaldehyde also forms acetic acid in aqueous solution. Acetic acid vapor is an eye, nose, and lung irritant, so both species contribute negatively to human health. We look at the impact of aerosol

  5. Quasi-Immiscible Spreading of Aqueous Surfactant Solutions on Entangled Aqueous Polymer Solution Subphases

    PubMed Central

    Sharma, Ramankur; Corcoran, Timothy E.; Garoff, Stephen; Przybycien, Todd M.; Swanson, Ellen R.; Tilton, Robert D.

    2014-01-01

    Motivated by the possibility of enhancing aerosol drug delivery to mucus-obstructed lungs, the spreading of a drop of aqueous surfactant solution on a physically entangled aqueous poly(acrylamide) solution subphase that mimics lung airway surface liquid was investigated. Sodium dodecyl sulfate was used as the surfactant. To visualize spreading of the drop and mimic the inclusion of a drug substance, fluorescein, a hydrophilic and non-surface active dye, was added to the surfactant solution. The spreading progresses through a series of events. Marangoni stresses initiate the convective spreading of the drop. Simultaneously, surfactant escapes across the drop’s contact line within a second of deposition and causes a change in subphase surface tension outside the drop on the order of 1 mN/m. Convective spreading of the drop ends within 2–3 seconds of drop deposition, when a new interfacial tension balance is achieved. Surfactant escape depletes the drop of surfactant and the residual drop takes the form of a static lens of non-zero contact angle. On longer time scales, the surfactant dissolves into the subphase. The lens formed by the water in the deposited drop persists for as long as 3 minutes after the convective spreading process ends due to the long diffusional timescales associated with the underlying entangled polymer solution. The persistence of the lens suggests that the drop phase behaves as if it were immiscible with the subphase during this time period. Whereas surfactant escapes the spreading drop and advances on the subphase/vapor interface, hydrophilic dye molecules in the drop do not escape, but remain with the drop throughout the convective spreading. The quasi-immiscible nature of the spreading event suggests that the chemical properties of the surfactant and subphase are much less important than their physical properties, consistent with prior qualitative studies of spreading of different types of surfactants on entangled polymer subphases: the

  6. Quasi-immiscible spreading of aqueous surfactant solutions on entangled aqueous polymer solution subphases.

    PubMed

    Sharma, Ramankur; Corcoran, Timothy E; Garoff, Stephen; Przybycien, Todd M; Swanson, Ellen R; Tilton, Robert D

    2013-06-26

    Motivated by the possibility of enhancing aerosol drug delivery to mucus-obstructed lungs, the spreading of a drop of aqueous surfactant solution on a physically entangled aqueous poly(acrylamide) solution subphase that mimics lung airway surface liquid was investigated. Sodium dodecyl sulfate was used as the surfactant. To visualize spreading of the drop and mimic the inclusion of a drug substance, fluorescein, a hydrophilic and non-surface-active dye, was added to the surfactant solution. The spreading progresses through a series of events. Marangoni stresses initiate the convective spreading of the drop. Simultaneously, surfactant escapes across the drop's contact line within a second of deposition and causes a change in subphase surface tension outside the drop on the order of 1 mN/m. Convective spreading of the drop ends within 2-3 s of drop deposition, when a new interfacial tension balance is achieved. Surfactant escape depletes the drop of surfactant, and the residual drop takes the form of a static lens of nonzero contact angle. On longer time scales, the surfactant dissolves into the subphase. The lens formed by the water in the deposited drop persists for as long as 3 min after the convective spreading process ends due to the long diffusional time scales associated with the underlying entangled polymer solution. The persistence of the lens suggests that the drop phase behaves as if it were immiscible with the subphase during this time period. Whereas surfactant escapes the spreading drop and advances on the subphase/vapor interface, hydrophilic dye molecules in the drop do not escape but remain with the drop throughout the convective spreading. The quasi-immiscible nature of the spreading event suggests that the chemical properties of the surfactant and subphase are much less important than their physical properties, consistent with prior qualitative studies of spreading of different types of surfactants on entangled polymer subphases: the selection of

  7. The effect of aqueous solution in Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  8. Removal of hexavalent chromium from aqueous solution by iron nanoparticles.

    PubMed

    Niu, Shao-Feng; Liu, Yong; Xu, Xin-Hua; Lou, Zhang-Hua

    2005-10-01

    Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe(0)) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contaminated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe(0) type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe(0) nanoparticles>Fe(0) nanoparticles>Fe(0) powder>Fe(0) filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)(3) should be the final product of Cr(VI). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater.

  9. Removal of hexavalent chromium from aqueous solution by iron nanoparticles*

    PubMed Central

    Niu, Shao-feng; Liu, Yong; Xu, Xin-hua; Lou, Zhang-hua

    2005-01-01

    Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe0) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contaminated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe0 type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe0 nanoparticles>Fe0 nanoparticles>Fe0 powder>Fe0 filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)3 should be the final product of Cr(VI). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater. PMID:16187417

  10. Uranium biosorption from aqueous solution onto Eichhornia crassipes.

    PubMed

    Yi, Zheng-ji; Yao, Jun; Chen, Hui-lun; Wang, Fei; Yuan, Zhi-min; Liu, Xing

    2016-04-01

    Batch experiments were conducted to investigate the biosorption of U(VI) from aqueous solutions onto the nonliving biomass of an aquatic macrophyte Eichhornia crassipes. The results showed that the adsorption of U(VI) onto E. crassipes was highly pH-dependent and the best pH for U(VI) removal was 5.5. U(VI) adsorption proceeded rapidly with an equilibrium time of 30 min and conformed to pseudo-second-order kinetics. The Langmuir isotherm model was determined to best describe U(VI) biosorption with a maximum monolayer adsorption capacity of 142.85 mg/g. Thermodynamic calculation results indicated that the U(VI) biosorption process was spontaneous and endothermic. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis implied that the functional groups (amino, hydroxyl, and carboxyl) may be responsible for the U(VI) adsorption process, in which the coordination and ion exchange mechanisms could be involved. We conclude that E. crassipes biomass is a promising biosorbent for the removal of uranium pollutants.

  11. Ethylbenzene Removal by Carbon Nanotubes from Aqueous Solution

    PubMed Central

    Bina, Bijan; Pourzamani, Hamidreza; Rashidi, Alimorad; Amin, Mohammad Mehdi

    2012-01-01

    The removal of ethylbenzene (E) from aqueous solution by multiwalled, single-walled, and hybrid carbon nanotubes (MWCNTs, SWCNTs, and HCNTs) was evaluated for a nanomaterial dose of 1 g/L, concentration of 10–100 mg/L, and pH 7. The equilibrium amount removed by SWCNTs (E: 9.98 mg/g) was higher than by MWCNTs and HCNTs. Ethylbenzene has a higher adsorption tendency on CNTs, so that more than 98% of it adsorbed in first 14 min, which is related to the low water solubility and the high molecular weight. The SWCNTs performed better for ethylbenzene sorption than the HCNTs and MWCNTs. Isotherms study indicates that the BET isotherm expression provides the best fit for ethylbenzene sorption by SWCNTs. Carbon nanotubes, specially SWCNTs, are efficient and rapid adsorbents for ethylbenzene which possess good potential applications to maintain high-quality water. Therefore, it could be used for cleaning up environmental pollution to prevent ethylbenzene borne diseases. PMID:22187576

  12. Aqueous solutions at the interface with phospholipid bilayers.

    PubMed

    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

  13. Interactions of Cl- and OH radical in aqueous solution.

    PubMed

    Valiev, Marat; D'Auria, Raffaella; Tobias, Douglas J; Garrett, Bruce C

    2009-08-06

    There is a considerable controversy surrounding the nature of the Cl-/OH complex in aqueous solution, which appears as a byproduct of the irradiation of salt solutions in nuclear reactor operation, radioactive waste storage, medicine, and environmental problems. In this work, we report results of combined quantum mechanical molecular mechanics calculations of ground-state free-energy surfaces and absorption spectrum through the CCSDT level of theory that are consistent with the experimental data and suggest that hemibonded HOCl- species may indeed exist in bulk aqueous solution.

  14. ``Phase'' Behavior of Aqueous Solutions of Poly(N-isopropylacrylamide)

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Tomoaki; Kobayashi, Kunihiko; Osa, Masashi; Yoshizaki, Takenao

    2008-03-01

    A series of linear poly(N-isopropylacrylamide)(PNIPAM) samples were prepared by living anionic polymerization. The cloud-point curves for their aqueous solutions were determined by monitoring the transmittance of light through the solutions. The transmittance decreased monotonically with increasing temperature below the cloud point, as expected, but unexpectedly, it remained at a constant value if heating was stopped at a temperature. It means that the decrease in transmittance with increasing temperature does not necessarily correspond to the phase separation, i.e., the cloud-point curve for an aqueous solution of PNIPAM is not always identical with the coexistence curve.

  15. SOLVENT EXTRACTION OF THORIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Warf, J.C.

    1959-04-21

    The separation of thorium values from rare earth metals contained ln aqueous solutions by means of extraction with a water immiscible alkyl phosphate diluted with a hydrocarbon such as hexane is described. While the extraction according to this invention may be carried out from any aqueous salt solution, it is preferred to use solutions containing free mineral acid. Hydrochloric acid and in particular nitric acid are sultable in a concentration ranging from 0.1 to 7 normal. The higher acid concentration results in higher extraction values.

  16. SEPARATION OF TECHNETIUM FROM AQUEOUS SOLUTIONS BY COPRECIPITATION WITH MAGNETITE

    DOEpatents

    Rimshaw, S.J.

    1961-10-24

    A method of separating technetium in the 4+ oxidation state from an aqueous basic solution containing products of uranium fission is described. The method consists of contacting the solution with finely divided magnetite and recovering a technetium-bearing precipitate. (AEC)

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

    ERIC Educational Resources Information Center

    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…

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

    ERIC Educational Resources Information Center

    Gao, Daqing

    2009-01-01

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

  19. Properties of aqueous solutions in THz frequency range

    NASA Astrophysics Data System (ADS)

    Cherkasova, O.; Nazarov, M.; Shkurinov, A.

    2017-01-01

    Terahertz time-domain spectroscopy has been used for measuring of bovine serum albumin and glucose solutions response. The transmission and the attenuated total internal reflection geometries have been combined for analyzing the dielectric properties of aqueous solutions spectra at 0.07-3.2 THz.

  20. REMOVAL OF CESIUM BY SORPTION FROM AQUEOUS SOLUTIONS

    DOEpatents

    Ames, L.L.

    1962-01-16

    ABS>A process is given for selectively removing cesium from acid aqueous solutions containing cesium in microquantities and other cations in macroquantities by absorption on clinoptilolite. The cesium can be eluted from the clinoptilolite with a solution of ammonia, potassium hydroxide, or rubidium hydroxide. (AEC)

  1. Molecular dynamics simulation of aqueous solutions of glycine betaine

    NASA Astrophysics Data System (ADS)

    Civera, Monica; Fornili, Arianna; Sironi, Maurizio; Fornili, Sandro L.

    2003-01-01

    Molecular dynamics simulation is used to investigate hydration properties of glycine betaine in a large range of solute concentrations. Statistical analyses of the system trajectories evidence microscopic details suggesting an interpretation of experimental results recently obtained for aqueous solutions of trimethylamine- N-oxide, a bioprotectant closely related to glycine betaine.

  2. Adsorption of arsenic from aqueous solution using magnetic graphene oxide

    NASA Astrophysics Data System (ADS)

    Sherlala, A. I. A.; Raman, A. A.; Bello, M. M.

    2017-06-01

    A binary of graphene oxide (GO) and iron oxide (IO) was prepared and used for the removal of arsenic from aqueous solution. The synthesized compound was characterized using XRD analysis. The prepared composite was used for the adsorption of arsenic from aqueous solution. Central Composite Design was used to design the adsorption experiments and to investigate the effects of operational parameters (initial concentration of arsenic, adsorbent dosage, pH and time) on the adsorption capacity and efficiency. The adsorbent shows a high adsorption capacity for the arsenic. The adsorption efficiency ranges between 33.2 % and 99.95 %. The most significant factors affecting the adsorption capacity were found to be the initial concentration of arsenic and the adsorbent dosage. The initial pH of the solution slightly affects the adsorption capacity, with the maximum adsorption capacity occurring around pH 6 - 7. Thus, the developed adsorbent has a potential for effective removal of arsenic from aqueous solution.

  3. Antiscalant properties of Spergularia rubra and Parietaria officinalis aqueous solutions

    NASA Astrophysics Data System (ADS)

    Cheap-Charpentier, Hélène; Gelus, Dominique; Pécoul, Nathalie; Perrot, Hubert; Lédion, Jean; Horner, Olivier; Sadoun, Jonathan; Cachet, Xavier; Litaudon, Marc; Roussi, Fanny

    2016-06-01

    The formation of calcium carbonate in water has important implications in industry. Chemical antiscalant is usually used to control scale depositions. Plant extracts have been recently used as new green antiscalant agents, as they can be easily prepared and are environmentally friendly. In this study, stock aqueous solutions of Spergularia rubra and Parietaria officinalis, two plants used in traditional medicine to treat or prevent urolithiasis, were obtained by infusion. The antiscaling properties of these extracts towards CaCO3 formation were tested by using chronoamperometry and Fast Controlled Precipitation methods. The aqueous solution of S. rubra was further fractionated to isolate compounds of lower polarity. Their efficiency towards CaCO3 precipitation was characterized by Fast Controlled Precipitation method. The inhibiting efficiency of this fractionated solution was greater than that of the stock aqueous solution.

  4. Ion clustering in aqueous solutions probed with vibrational energy transfer

    PubMed Central

    Bian, Hongtao; Wen, Xiewen; Li, Jiebo; Chen, Hailong; Han, Suzee; Sun, Xiuquan; Song, Jian; Zhuang, Wei; Zheng, Junrong

    2011-01-01

    Despite prolonged scientific efforts to unravel the hydration structures of ions in water, many open questions remain, in particular concerning the existences and structures of ion clusters in 1∶1 strong electrolyte aqueous solutions. A combined ultrafast 2D IR and pump/probe study through vibrational energy transfers directly observes ion clustering in aqueous solutions of LiSCN, NaSCN, KSCN and CsSCN. In a near saturated KSCN aqueous solution (water/KSCN molar ratio = 2.4/1), 95% of the anions form ion clusters. Diluting the solution results in fewer, smaller, and tighter clusters. Cations have significant effects on cluster formation. A small cation results in smaller and fewer clusters. The vibrational energy transfer method holds promise for studying a wide variety of other fast short-range molecular interactions.

  5. EMERGING TECHNOLOGY BULLETIN: REMOVAL OF PHENOL FROM AQUEOUS SOLUTIONS USING HIGH ENERGY ELECTRON BEAM IRRADIATION

    EPA Science Inventory

    Irradiation of aqueous solutions with high-energy electrons results in the formation of the aqueous electron, hydrogen radical, H-, and the hydroxyl radical, OH-. These reactive transient species initiate chemical reactions capable of destroying organic compounds in aqueous solut...

  6. Application of magnetic chitosan composites for the removal of toxic metal and dyes from aqueous solutions.

    PubMed

    Reddy, D Harikishore Kumar; Lee, Seung-Mok

    2013-12-01

    Magnetic chitosan composites (MCCs) are a novel material that exhibits good sorption behavior toward various toxic pollutants in aqueous solution. These magnetic composites have a fast adsorption rate and high adsorption efficiency, efficient to remove various pollutants and they are easy to recover and reuse. These features highlight the suitability of MCCs for the treatment of water polluted with metal and organic materials. This review outlines the preparation of MCCs as well as methods to characterize these materials using FTIR, XRD, TGA and other microscopy-based techniques. Additionally, an overview of recent developments and applications of MCCs for metal and organic pollutant removal is discussed in detail. Based on current research and existing materials, some new and futuristic approaches in this fascinating area are also discussed. The main objective of this review is to provide up-to-date information about the most important features of MCCs and to show their advantages as adsorbents in the treatment of polluted aqueous solutions. © 2013.

  7. On crack closure of precipitation hardened steels in aqueous solution

    NASA Astrophysics Data System (ADS)

    Hamano, R.

    1989-06-01

    Fatigue crack propagation tests were carried out in air and in a 3.5 pct NaCl aqueous solution under cathodic potential of -0.85 V (Ag/AgCl) for aged-hardened high strength steel (Ni-Al-Cr-Mo-C steel). the emphasis in the study was placed on the crack closure behavior of age-hardened materials in air and in the NaCl aqueous solution. The degree of crack closure in air was dependent on the behavior of plastic deformation such as inhomogeneous or homogeneous slip under mixed modes I and II. The underaged material containing coherent precipitates with the matrix had a higher crack opening load in air, compared with the overaged steel containing incoherent precipitates with the matrix. The degrec of crack closure of the underaged material in the NaCl aqueous solution was lower than that in air and was similar to that of overaged materials in the NaCl aqueous solution. It was shown that the decreased crack closure level for the underaged material resulted from accelerated fatigue crack growth under mode I due to hydrogen embrittlement in the aqueous solution.

  8. Surface tension of low-temperature aqueous solutions

    SciTech Connect

    Horibe, A.; Fukusako, S.; Yamada, M.

    1996-03-01

    Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20{degrees}C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.

  9. Mesoscale inhomogeneities in aqueous solutions of small amphiphilic molecules.

    PubMed

    Subramanian, Deepa; Boughter, Christopher T; Klauda, Jeffery B; Hammouda, Boualem; Anisimov, Mikhail A

    2013-01-01

    Small amphiphilic molecules, also known as hydrotropes, are too small to form micelles in aqueous solutions. However, aqueous solutions of nonionic hydrotropes show the presence of a dynamic, loose, non-covalent clustering in the water-rich region, This clustering can be viewed as "micelle-like structural fluctuations". Although these fluctuations are short ranged (approximately 1 nm) and short lived (10 ps-50 ps), they may lead to thermodynamic anomalies. In addition, many experiments on aqueous solutions of hydrotropes show the occasional presence of mesoscale (approximately 100 nm) inhomogeneities. We have combined results obtained from molecular dynamics simulations, small-angle neutron scattering, and dynamic light-scattering experiments carried out on tertiary butyl alcohol (hydrotrope)-water solutions and on tertiary butyl alcohol-water-cyclohexane (hydrophobe) solutions to elucidate the nature and structure of these inhomogeneities. We have shown that stable mesoscale inhomogeneities occur in aqueous solutions of nonionic hydrotropes only when the solution contains a third, more hydrophobic, component. Moreover, these inhomogeneities exist in ternary systems only in the concentration range where structural fluctuations and thermodynamic anomalies are observed in the binary water-hydrotrope solutions. Addition of a hydrophobe seems to stabilize the water-hydrotrope structural fluctuations, and leads to the formation of larger (mesoscopic) droplets. The structure of these mesoscopic droplets is such that they have a hydrophobe-rich core, surrounded by a hydrogen-bonded shell of water and hydrotrope molecules. These droplets can be extremely long-lived, being stable for over a year. We refer to the phenomenon of formation of mesoscopic droplets in aqueous solutions of nonionic hydrotropes containing hydrophobes, as mesoscale solubilization. This phenomenon may represent a ubiquitous feature of nonionic hydrotropes that exhibit clustering in water, and may have

  10. Biosorption and bioreduction of copper from different copper compounds in aqueous solution.

    PubMed

    Andreazza, Robson; Okeke, Benedict C; Pieniz, Simone; Bento, Fátima M; Camargo, Flávio A O

    2013-06-01

    High copper concentration is toxic for living organisms including humans. Biosorption is a bioremediation technique that can remove copper and other pollutants from aqueous medium and soils, consequently cleaning the environment. The aim of this study was, therefore, to investigate the influence of different copper compounds (Cu(II) as CuCl2; Cu(II) as CuSO4; and Cu(I) as CuCl) on copper bioreduction and biosorption using four copper-resistant bacteria isolated from the rhizosphere of two plants (Avena sativa and Plantago lanceolata) in aqueous matrix. Copper resistance profile, bioreduction, and biosorption after 48 h of incubation were evaluated. The isolates displayed high copper resistance. However, isolate A1 did not grow very well in the CuCl2 and isolate T5 was less resistant to copper in aqueous solutions amended with CuCl (Cu(I)). The best copper source for copper bioreduction and biosorption was CuSO4 and the isolates removed as much as ten times more copper than in aqueous solutions amended with the other copper compounds. Moreover, Cu(I) did not succumb to biosorption, although the microbes were resistant to aqueous solutions of CuCl. In summary, Cu(II) from CuSO4 was furthermost susceptible to bioreduction and biosorption for all isolates. This is an indication that copper contamination of the environment from the use of CuSO4 as an agrochemical is amenable to bioremediation.

  11. Reorientation and Allied Dynamics in Water and Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Laage, Damien; Stirnemann, Guillaume; Sterpone, Fabio; Rey, Rossend; Hynes, James T.

    2011-05-01

    The reorientation of a water molecule is important for a host of phenomena, ranging over—in an only partial listing—the key dynamic hydrogen-bond network restructuring of water itself, aqueous solution chemical reaction mechanisms and rates, ion transport in aqueous solution and membranes, protein folding, and enzymatic activity. This review focuses on water reorientation and related dynamics in pure water, and for aqueous solutes with hydrophobic, hydrophilic, and amphiphilic character, ranging from tetra-methylurea to halide ions and amino acids. Attention is given to the application of theory, simulation, and experiment in the probing of these dynamics, in usefully describing them, and in assessing the description. Special emphasis is placed on a novel sudden, large-amplitude jump mechanism for water reorientation, which contrasts with the commonly assumed Debye rotational diffusion mechanism, characterized by small-amplitude angular motion. Some open questions and directions for further research are also discussed.

  12. Separation and concentration of lower alcohols from dilute aqueous solutions

    DOEpatents

    Moore, Raymond H.; Eakin, David E.; Baker, Eddie G.; Hallen, Richard T.

    1991-01-01

    A process for producing, from a dilute aqueous solution of a lower (C.sub.1 -C.sub.5) alcohol, a concentrated liquid solution of the alcohol in an aromatic organic solvent is disclosed. Most of the water is removed from the dilute aqueous solution of alcohol by chilling sufficiently to form ice crystals. Simultaneously, the remaining liquid is extracted at substantially the same low temperature with a liquid organic solvent that is substantially immiscible in aqueous liquids and has an affinity for the alcohol at that temperature, causing the alcohol to transfer to the organic phase. After separating the organic liquid from the ice crystals, the organic liquid can be distilled to enrich the concentration of alcohol therein. Ethanol so separated from water and concentrated in an organic solvent such as toluene is useful as an anti-knock additive for gasoline.

  13. Phytodegradation potential of bisphenolA from aqueous solution by Azolla Filiculoides

    PubMed Central

    2014-01-01

    Many organic hazardous pollutants such as bisphenolA (BPA) which are toxic and not easily biodegradable can concerns for environmental pollution worldwide. The objective of this study was to examine whether Azolla Filiculoides is able to remove BPA from aqueous solutions. In this study, the Azolla with different biomass (0.3, 0.6, 0.9, 1.2 g) has been cultured in solution that was contained 5, 10, 25 and 50 ppm BPA. Samples were collected every 2 days from all of containers. The analytical determination of BPA was performed by using of DR4000 uv-visible at λmax = 276 nm. The results indicated that Azolla has high ability to remove BPA from aqueous solutions. The BPA removal was 60-90%. The removal efficiency is increasing with decreasing of BPA concentration and increasing of biomass amount and vice versa. The removal efficiency was more than 90% when BPA concentration was 5 ppm and amount of biomass was 0.9gr. It is concluded that Azolla able remove BPA by Phytodegradation from the aqueous solutions. Since conventional methods of BPA removal need to high cost and energy, phytoremediation by Azolla as a natural treatment system can decrease those issues and it can be a useful and beneficial method to removal of BPA. PMID:24693863

  14. Electrochemical Removal Of Selenate From Aqueous Solutions

    PubMed Central

    Baek, Kitae; Kasem, Naji; Ciblak, Ali; Vesper, Dorothy; Padilla, Ingrid; Alshawabkeh, Akram N.

    2013-01-01

    Removal of selenate from solution is investigated in batch electrochemical systems using reactive iron anodes and copper plate cathode in a bicarbonate medium. Iron anodes produce ferrous hydroxide, which is a major factor in the removal of selenate from solution. Iron anodes also generate a significant decrease in the oxidation-reduction potential (ORP) of the solution because it prevents generation of oxygen gas at the anode by electrolysis. The removal rates varied from 45.1 to 97.4%, depending on current density and selenate concentration. The transformation of selenate by the process is modeled based on a heterogeneous reaction coupled with electrochemical generation of ferrous and hydroxide. The rates are optimized at lower initial concentrations, higher electrical currents, and the presence of anions. Presence of dissolved oxygen does not cause any significant effects the removal of selenate. PMID:23378820

  15. Oxidation of Hydrazine in Aqueous Solutions

    DTIC Science & Technology

    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

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

    PubMed

    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.

  17. Method for removing organic liquids from aqueous solutions and mixtures

    DOEpatents

    Hrubesh, Lawrence W.; Coronado, Paul R.; Dow, Jerome P.

    2004-03-23

    A method for removing organic liquids from aqueous solutions and mixtures. The method employs any porous material preferably in granular form and having small pores and a large specific surface area, that is hydrophobic so that liquid water does not readily wet its surface. In this method, organics, especially organic solvents that mix with and are more volatile than water, are separated from aqueous solution by preferentially evaporating across the liquid/solid boundary formed at the surfaces of the hydrophobic porous materials. Also, organic solvents that are immiscible with water, preferentially wet the surfaces of the hydrophobic material and are drawn within the porous materials by capillary action.

  18. Photochemical properties of Yt base in aqueous solution.

    PubMed Central

    Paszyc, S; Rafalska, M

    1979-01-01

    Photoreactivity of Yt base [I] has been studied in aqueous solution [pH approximately 6] saturated with oxygen. Two photoproducts (II,III], resulting from irradiation at lambda = 253.7 nm and lambda greater than or equal to 290 nm, were isolated and their structures determined. The quantum yield for Yt base disappearance [zeta dis] is 0.002 [lambda = 313 nm]. It was shown that dye-sensitized photooxidation of Yt base in aqueous solution occurs according to a Type I mechanism, as well as with participation of singlet state oxygen. Quantum yields, fluorescence decay times and phosphorescence of Yt base have been also determined. PMID:424298

  19. Photodegradation of triazine herbicides in aqueous solutions and natural waters.

    PubMed

    Evgenidou, E; Fytianos, K

    2002-10-23

    The photodegradation of three triazines, atrazine, simazine, and prometryn, in aqueous solutions and natural waters using UV radiation (lambda > 290 nm) has been studied. Experimental results showed that the dark reactions were negligible. The rate of photodecomposition in aqueous solutions depends on the nature of the triazines and follows first-order kinetics. In the case of the use of hydrogen peroxide and UV radiation, a synergistic effect was observed. The number of photodegradation products detected, using FIA/MS and FIA/MS/MS techniques, suggests the existence of various degradation routes resulting in complex and interconnected pathways.

  20. Valence Electronic Structure of Aqueous Solutions: Insights from Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Seidel, Robert; Winter, Bernd; Bradforth, Stephen E.

    2016-05-01

    The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.

  1. Valence Electronic Structure of Aqueous Solutions: Insights from Photoelectron Spectroscopy.

    PubMed

    Seidel, Robert; Winter, Bernd; Bradforth, Stephen E

    2016-05-27

    The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.

  2. Absorption into silicone rubber membranes from powders and aqueous solutions.

    PubMed

    McCarley, Kelly D; Bunge, Annette L

    2003-01-02

    This study compared the rate and amount of absorption from aqueous solutions and pure powders of 3- and 4-cyanophenol (CP) into silicone rubber (SR) membranes. SR membranes were cast directly onto a zinc-selenide attenuated total reflectance (ATR) crystal, which was then mounted on a Fourier transform infrared (FTIR) spectrometer. CP was presented to the SR membrane from aqueous solutions or powders sufficient to completely cover the membrane surface. The concentration of CP in the membrane at the interface with the crystal was determined by IR absorption of the C triple bond N stretch. The amount of CP in the SR membrane at steady state was determined by extraction and UV absorption measurements of the extract. The concentration of CP in SR membranes was found to depend weakly on the concentration of the aqueous solution. The amount of CP in SR membranes equilibrated with pure powders was essentially the same as for the CP-saturated solutions. Diffusion coefficients for 3 and 4-CP (2.8+/-0.2 and 2.5+/-0.6 x 10(-7) cm(2) s(-1), respectively) were not statistically different. The absorption rate of CP into SR membranes was almost the same from the powder and aqueous solution indicating that the rate of mass transfer from the powder to membrane was larger than 0.04 cm h(-1).

  3. Natural adsorbents of dyes from aqueous solution

    NASA Astrophysics Data System (ADS)

    Rahmani, Meryem; El Hajjaji, souad; Dahchour, Abdelmalek; El M'Rabet, Mohammadine

    2017-04-01

    Contamination of natural waters is a current environmental problem and lot of work has been done to find methods for its, prevention and remediation such as ionic exchange, adsorption on active carbon, filtration, electrolysis, biodegradation …etc. Adsorption is one of the most applied methods according to its effectiveness and easy management. Some adsorbents with good properties such as active alumina, zeolites, crop residues … etc, are suitable to substitute usual active carbon. This study aimed at the removal of dyes using oil shale as natural support, and its optimization by factorial experiment. Three factors were considered namly:pollutant concentration, pH and weight of the adsorbent. Tests have been performed with cationic and anionic dyes. Experimental results show that pseudo-first-order kinetic model provided the best fit to the experimental data for the adsorption by the oil shale. Langmuir, Freundlich and Temkin isotherm models were tested to fit experimental data, the adsorption equilibrium was well described by Freundlich isotherm for methylorange and Temkin for methyl blue. Analysis were completed by oil shale characterization educing XRD, IR, XRF techniques, and cationic exchange capacity.

  4. Degradation/oxidation susceptibility of organic photovoltaic cells in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Habib, K.; Husain, A.; Al-Hazza, A.

    2015-12-01

    A criterion of the degradation/oxidation susceptibility of organic photovoltaic (OPV) cells in aqueous solutions was proposed for the first time. The criterion was derived based on calculating the limit of the ratio value of the polarization resistance of an OPV cell in aqueous solution (Rps) to the polarization resistance of the OPV cell in air (Rpair). In other words, the criterion lim(Rps/Rpair) = 1 was applied to determine the degradation/oxidation of the OPV cell in the aqueous solution when Rpair became equal (increased) to Rps as a function of time of the exposure of the OPV cell to the aqueous solution. This criterion was not only used to determine the degradation/oxidation of different OPV cells in a simulated operational environment but also it was used to determine the electrochemical behavior of OPV cells in deionized water and a polluted water with fine particles of sand. The values of Rps were determined by the electrochemical impedance spectroscopy at low frequency. In addition, the criterion can be applied under diverse test conditions with a predetermined period of OPV operations.

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

    PubMed

    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.

  6. Automated iodine monitor system. [for aqueous solutions

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The feasibility of a direct spectrophotometric measurement of iodine in water was established. An iodine colorimeter, was built to demonstrate the practicality of this technique. The specificity of this method was verified when applied to an on-line system where a reference solution cannot be used, and a preliminary design is presented for an automated iodine measuring and controlling system meeting the desired specifications. An Automated iodine monitor/controller system based on this preliminary design was built, tested, and delivered to the Johnson Space Center.

  7. Photocatalytic degradation of molinate in aqueous solutions.

    PubMed

    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.

  8. Optical properties of DNA in aqueous solution.

    PubMed

    Umazano, J P; Bertolotto, J A

    2008-04-01

    In the study of DNA electric birefringence, it is usual to use theories that consider that molecules in solution are small in relation to the light wavelength. In this work, we study the DNA electric birefringence using a broken-rod macroion (BRM) model composed of two cylindrical arms which does not restrict the size of the molecules. To achieve this, we include the inhomogeneity effect of the light electric field through the molecule and the interaction between its different parts. To analyze the interaction between a molecule and the incident beam of light, we apply the discrete dipole approximation (DDA), according to which each molecule is described as a finite array of electronic coupled oscillators. The electric birefringence is calculated from the oscillator polarizability. This is obtained from experimental data of electric birefringence saturation and from the increment of the solution refraction index in relation to that of the solvent. Furthermore, the oscillator polarizability is also estimated from DNA absorption spectrum using the Kronig-Kramers relations. This allows us to analyze the contributions of the different absorption bands of DNA to the electric birefringence. We analyze the influence of the inhomogeneity of the light electric field and of the intramolecular interactions in the characterization of DNA optical properties using electric birefringence measurements.

  9. Dissociation of methane hydrate in aqueous NaCl solutions.

    PubMed

    Yagasaki, Takuma; Matsumoto, Masakazu; Andoh, Yoshimichi; Okazaki, Susumu; Tanaka, Hideki

    2014-10-09

    Molecular dynamics simulations of the dissociation of methane hydrate in aqueous NaCl solutions are performed. It is shown that the dissociation of the hydrate is accelerated by the formation of methane bubbles both in NaCl solutions and in pure water. We find two significant effects on the kinetics of the hydrate dissociation by NaCl. One is slowing down in an early stage before bubble formation, and another is swift bubble formation that enhances the dissociation. These effects arise from the low solubility of methane in NaCl solution, which gives rise to a nonuniform spatial distribution of solvated methane in the aqueous phase. We also demonstrate that bubbles form near the hydrate interface in dense NaCl solutions and that the hydrate dissociation proceeds inhomogeneously due to the bubbles.

  10. Drag enhancement of aqueous electrolyte solutions in turbulent pipe flow.

    PubMed

    Doherty, Andrew P; Spedding, Peter L; Chen, John J J

    2010-04-22

    Detailed experimental results are presented for both laminar and turbulent flow of aqueous solutions in pipes of different diameters. Nonelectrolytes, such as sugar solutions followed the normal Moody pressure loss curves. Drag enhancement was demonstrated for turbulent flow of aqueous electrolyte solutions but not for laminar flow. The increased pressure drop for turbulent electrolyte flow was attributed to an electroviscous effect and a theory was developed to explain the drag enhancement. The increased pressure drop for the turbulent region of flow was shown to depend on the Debye length in the laminar sublayer on the pipe wall. Reasonable predictions of the increasing drag were obtained for both 1:1 and 2:1 electrolyte solutions.

  11. RECOVERY OF URANIUM FROM AQUEOUS PHOSPHATE-CONTAINING SOLUTIONS

    DOEpatents

    Igelsrud, I.; Stephen, E.F.

    1959-08-11

    ABS>A method is presented for recovering hexavalent uranium from an acidic phosphaie solution. A high molecular weight amine, such as a mixture of cccoanut oil amines, is added to the solution in such amount as to give a ratio of about 2000 parts by weight of amine to 1 part by weight of uranium. The uranium is precipitated with the amines and the whole filtered from the solution. The uranium is leached from the amine mass by washing with aqueous sodium carbonate solution; and the amine mixture is available for reuse.

  12. Radiolysis of paracetamol in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    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.

  13. Special Features of Copper(II) Detection in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Sergeev, A. A.; Mironenko, A. Y.; Leonov, A. A.; Nazirov, A. E.; Voznesenskiy, S. S.; Bratskaya, S. Y.; Kulchin, Y. N.

    New approach to organize fluorescent sensor system for determination of metal ions in aqueous solutions was presented. The approach is based on modification of hydrophilic polymer with sensitive fluorescent indicators. Possibility to register Cu2+ ions by analyzing of luminescence excitation spectra and lifetimes of the sensitive coating is presented.

  14. [Anomalous Properties of Water and Aqueous Solutions at Low Temperatures].

    PubMed

    Matsumoto, Masakazu

    2015-01-01

    Water has many anomalous properties below the room temperature. The temperature range overlaps with that of the Earth's atmosphere and also with that natural life forms favor. We review the origin of the anomalous properties of water and aqueous solutions in association with the hypothetical second critical point and liquid-liquid phase separation of water hidden in the supercooled state of liquid water.

  15. REMOVAL OF CESIUM FROM AQUEOUS SOLUTIONS BY ADSORPTION

    DOEpatents

    Knoll, K.C.

    1963-07-16

    A process of removing microquantities of cesium from aqueous solutions also containing macroquantities of other ions by adsorption on clinoptilolite is described. The invention resides in the pretreatment of the clinoptilolite by heating at 400 deg C and cooling prior to use. (AEC)

  16. Hydrogen generation by electrolysis of aqueous organic solutions

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Chun, William (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor)

    2002-01-01

    A device for electrolysis of an aqueous solution of an organic fuel. The electrolyte is a solid-state polymer membrane with anode and cathode catalysts on both surfaces for electro-oxidization and electro-reduction. A low-cost and portable hydrogen generator can be made based on the device with organic fuels such as methanol.

  17. RECOVERY OF METAL VALUES FROM AQUEOUS SOLUTIONS BY SOLVENT EXTRACTION

    DOEpatents

    Moore, R.L.

    1959-09-01

    An organic solvent mixure is described for extracting actinides from aqueous solutions; the solvent mixture consists of from 10 to 25% by volume of tributyl phosphate and the remainder a chlorine-fluorine-substituted saturated hydrocarbon having two carbon atoms in the molecule.

  18. Photodecomposition of an acaricide, fenazaquin, in aqueous alcoholic solution.

    PubMed

    Bhattacharyya, Jayati; Banerjee, Hemanta; Bhattacharyya, Anjan

    2003-07-02

    Fenazaquin (I) is a new acaricide of the quinazoline class. The photodecomposition of I was studied in aqueous methanolic and 2-propanolic solution under UV light (30 h) and sunlight (70 h) separately. The photolytic half-lives in aqueous methanolic solution were found to be 17.1 h (UV) and 38.1 h (sunlight), whereas these were 12.9 h (UV) and 29.2 h (sunlight) for aqueous 2-propanolic solution; all followed a first-order reaction kinetics. Six photoproducts were obtained: beta-phenyl (p-tert-butyl) ethyl alcohol (II), 4-hydroxyquinazoline (III), p-tert-butyl vinyl benzene (IV), 2,4-dihydroxyquinazoline (V), phenyl (p-tert-butyl) acetic acid (VI), and 2-methyl-2-[4'-(2' '-hydroxyethyl)phenyl]propanoic acid (VII). Compounds VI and VII could be isolated only from aqueous 2-propanolic solution under sunlight irradiation. The major degradation products are formed as a result of cleavage of the ether bridge linking the quinazoline and phenyl ring systems of the molecule, oxidation of the tert-butyl substituent, and oxidation of the heterocyclic portion of the quinazoline ring. A probable mechanism of formation of the photoproducts is also suggested.

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

    NASA Astrophysics Data System (ADS)

    Ryo, Y.; Kawaguchi, M.

    1992-05-01

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

  20. Colorimetric "naked eye" sensing of anions in aqueous solution.

    PubMed

    Gunnlaugsson, Thorfinnur; Kruger, Paul E; Jensen, Paul; Tierney, Juliann; Ali, Haslin Dato Paduka; Hussey, Gillian M

    2005-12-23

    [structure: see text] The synthesis and UV-vis and NMR spectroscopic studies of thiourea-based colorimetric sensors for anions are presented. These sensors can recognize anions through hydrogen binding even in competitive pH-buffered aqueous solutions, giving rise to large color changes that are clearly visible to the naked eye.

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

    PubMed

    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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Hydrogen generation by electrolysis of aqueous organic solutions

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Chun, William (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor)

    2006-01-01

    A device for electrolysis of an aqueous solution of an organic fuel. The electrolyte is a solid-state polymer membrane with anode and cathode catalysts on both surfaces for electro-oxidization and electro-reduction. A low-cost and portable hydrogen generator can be made based on the device with organic fuels such as methanol.

  3. Hydrogen generation by electrolysis of aqueous organic solutions

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Chun, William (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor)

    2002-01-01

    A device for electrolysis of an aqueous solution of an organic fuel. The electrolyte is a solid-state polymer membrane with anode and cathode catalysts on both surfaces for electro-oxidization and electro-reduction. A low-cost and portable hydrogen generator can be made based on the device with organic fuels such as methanol.

  4. Non-aqueous solution preparation of doped and undoped lixmnyoz

    DOEpatents

    Boyle, Timothy J.; Voigt, James A.

    1997-01-01

    A method for generation of phase-pure doped and undoped Li.sub.x Mn.sub.y O.sub.z precursors. The method of this invention uses organic solutions instead of aqueous solutions or nonsolution ball milling of dry powders to produce phase-pure precursors. These precursors can be used as cathodes for lithium-polymer electrolyte batteries. Dopants may be homogeneously incorporated to alter the characteristics of the powder.

  5. The precipitation of potassium aluminium sulphate from aqueous solution

    NASA Astrophysics Data System (ADS)

    Mullin, J. W.; Žáček, S.

    1981-06-01

    A precipitation study has been made with potassium aluminium sulphate (potash alum) produced by mixing aqueous solutions of its constituent salts. Rates of nucleation, as indicated by the induction period, were measured for both agitated and non-agitated solutions over the temperature range 15-35°C. Nucleation rates increase with increases in agitation, temperature and supersaturation, but the latter has the dominant effect, as predicted by classical nucleation theory. The temperature-dependence of the interfacial tension is evaluated.

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

    PubMed

    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.

  7. Mineralization of aniline in aqueous solution by electrochemical activation of persulfate.

    PubMed

    Chen, Wen-Shing; Huang, Chi-Pin

    2015-04-01

    Oxidative degradation of aniline in aqueous solution was carried out by coupling electrolysis with persulfate oxidation, in which a synergistic effect occurred. Experiments were performed under a batch-wise mode to evaluate the influence of various operation parameters on the electrolytic behavior, such as acidity of aqueous solution, temperature, electrode potential, persulfate anion concentration and nitrogen/oxygen gas dosage. The aniline pollutants could be almost entirely mineralized by means of electro-activated persulfate oxidation, wherein sulfate radicals were presumed to be principal oxidizing agents. Besides, electrogenerated hydrogen peroxide originated from cathodic reduction of oxygen, supplied chiefly by anodic oxidation of water, would contribute partially for decomposition of aniline. On the whole, the electro-activated persulfate process is a very promising method for treatment of aniline in wastewater.

  8. Surface tensions of inorganic multicomponent aqueous electrolyte solutions and melts.

    PubMed

    Dutcher, Cari S; Wexler, Anthony S; Clegg, Simon L

    2010-11-25

    A semiempirical model is presented that predicts surface tensions (σ) of aqueous electrolyte solutions and their mixtures, for concentrations ranging from infinitely dilute solution to molten salt. The model requires, at most, only two temperature-dependent terms to represent surface tensions of either pure aqueous solutions, or aqueous or molten mixtures, over the entire composition range. A relationship was found for the coefficients of the equation σ = c(1) + c(2)T (where T (K) is temperature) for molten salts in terms of ion valency and radius, melting temperature, and salt molar volume. Hypothetical liquid surface tensions can thus be estimated for electrolytes for which there are no data, or which do not exist in molten form. Surface tensions of molten (single) salts, when extrapolated to normal temperatures, were found to be consistent with data for aqueous solutions. This allowed surface tensions of very concentrated, supersaturated, aqueous solutions to be estimated. The model has been applied to the following single electrolytes over the entire concentration range, using data for aqueous solutions over the temperature range 233-523 K, and extrapolated surface tensions of molten salts and pure liquid electrolytes: HCl, HNO(3), H(2)SO(4), NaCl, NaNO(3), Na(2)SO(4), NaHSO(4), Na(2)CO(3), NaHCO(3), NaOH, NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4), NH(4)HCO(3), NH(4)OH, KCl, KNO(3), K(2)SO(4), K(2)CO(3), KHCO(3), KOH, CaCl(2), Ca(NO(3))(2), MgCl(2), Mg(NO(3))(2), and MgSO(4). The average absolute percentage error between calculated and experimental surface tensions is 0.80% (for 2389 data points). The model extrapolates smoothly to temperatures as low as 150 K. Also, the model successfully predicts surface tensions of ternary aqueous mixtures; the effect of salt-salt interactions in these calculations was explored.

  9. Experimental measurements of U60 nanocluster stability in aqueous solution

    NASA Astrophysics Data System (ADS)

    Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

    2015-05-01

    In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the

  10. Solubility of nitrous oxide in alkanolamine aqueous solutions

    SciTech Connect

    Tsai, T.C.; Ko, J.J.; Wang, H.M.; Lin, C.Y.; Li, M.H.

    2000-04-01

    The solubility of nitrous oxide (N{sub 2}O) in alkanolamine aqueous solutions has been measured at (30, 35, and 40) C. The systems studied are monoethanolamine, diethanolamine, diisopropanolamine, triethanolamine, and 2-amino-2-methyl-1-propanol aqueous solutions. The concentration of amine for monoethanolamine ranges from (1 to 6) kmol/m{sup 3} and for other amines from (0.5 to 3) kmol/m{sup 3}. The accuracy of the measurement is estimated to be {+-}2%. A semiempirical model of the excess Henry's constant proposed by Wang et al. (1992) was used to correlate the solubility of N{sub 2}O in amine solutions. The parameters of the correlation were determined from the measured solubility data and the available data in the open literature. For a wide temperature range from (15 to 75) C, the obtained correlation has been shown to represent reasonably the solubility of N{sub 2}O in six amine aqueous solutions: MEA, DEA, DIPA, TEA, MDEA, and AMP. For the purpose of process design, the obtained correlations are, in general, satisfactory for estimating the solubility of N{sub 2}O in amine solutions, which in turn can be used to estimate the correct free-gas solubility of CO{sub 2} in amines.

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

    PubMed

    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.

  12. Laboratory study of soil flushing by aqueous solutions

    SciTech Connect

    Park, J.; O`Neill, M.W.; Symons, J.M.

    1998-10-01

    This paper explores the removal of organics from soils in a simulated in-situ environment using aqueous solution extraction. A laboratory investigation is described in which organic compounds representative of the major groups of organic contaminants were adsorbed in low concentrations onto slightly organic, loamy soil, and various aqueous solutions were permeated through the soil under controlled hydraulic gradients and effective stress conditions, simulating the in-situ extraction process. The effectiveness of the extraction process was evaluated by periodically measuring the concentration of the contaminants in the permeameter effluent. Simple contact shaking tests were also performed and compared with the results of the permeation tests to ascertain whether contact shaking tests can be used as an index to the effectiveness of permeation testing. The results may be applicable to injection and extraction wells, in which the solution extract is pumped to a location on the ground surface for treatment.

  13. Molecular mechanism of the viscosity of aqueous glucose solutions

    NASA Astrophysics Data System (ADS)

    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.

  14. Spontaneous Oligomerization of Nucleotide Alternatives in Aqueous Solutions.

    PubMed

    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.

  15. Brillouin and Raman Scattering Study of Ethylene Glycol Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Seshimo, Y.; Ike, Y.; Kojima, S.

    2008-02-01

    We studied the cluster structure of ethylene glycol aqueous solutions by Brillouin and Raman scattering. We measured the ultrasonic sound velocity of the sample by Brillouin scattering. From the concentration dependence of the sound velocity, we studied the cluster structure in the solution. We showed that the number of H2O molecule neighboring a EG molecule becomes a little higher with increasing temperature and the intermolecular interaction between EG and H2O molecules weakened with increasing temperature. In Raman scattering study, We studied the hydrogen bond in the solution using the OD stretching band. We revealed that the strength of the hydrogen bond is independent of the EG concentration.

  16. Spontaneous Oligomerization of Nucleotide Alternatives in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  17. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, C.S.; Chriswell, C.D.

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%. 5 figs.

  18. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, Charles S. [Ames, IA; Chriswell, Colin D. [Slater, IA

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%.

  19. REMOVAL OF SELECTED POLLUTANTS FROM AQUEOUS MEDIA BY HARDWOOD MULCH

    EPA Science Inventory

    Generic hardwood mulch, usually used for landscaping, was utilized to remove several selected pollutants (heavy metals and toxic organic compounds) typically found in urban stormwater (SW) runoff. The hardwood mulch sorbed all the selected pollutants from a spiked stormwater mix...

  20. REMOVAL OF SELECTED POLLUTANTS FROM AQUEOUS MEDIA BY HARDWOOD MULCH

    EPA Science Inventory

    Generic hardwood mulch, usually used for landscaping, was utilized to remove several selected pollutants (heavy metals and toxic organic compounds) typically found in urban stormwater (SW) runoff. The hardwood mulch sorbed all the selected pollutants from a spiked stormwater mix...

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Structures and stability of salt-bridge in aqueous solution.

    PubMed

    Sagarik, Kritsana; Chaiyapongs, Supaporn

    2005-09-01

    Structures and stability of salt-bridges in aqueous solutions were investigated using a complex formed from the guanidinium (Gdm+) and formate (FmO-) ions as a model system. The Test-particle model (T-model) potentials to describe the interactions in the Gdm+-H2O, FmO(-)-H2O and Gdm+-FmO- complexes were constructed, tested and applied in molecular dynamics (MD) simulations of the aqueous solutions at 298 K. The three-dimensional structures and energetic of the hydrogen bond (H-bond) networks of water in the first hydration shells of the Gdm+ and FmO- ions, as well as the Gdm+-FmO- complex, were visualized and analyzed using various probability distribution (PD) maps. The structures of the average potential energy landscapes at the H-bond networks were employed to characterize the stability and dynamic behavior of water molecules in the first hydration shells of the solutes. It was observed that water molecules in the first hydration shell of the close-contact Gdm+-FmO- complex form associated H-bond networks, which introduce a net stabilization effect to the ion-pair, whereas those in the interstitial H-bond network destabilize and break the solvent-separated Gdm+-FmO- complex. The present results showed that, in order to provide complete insights into the structures and stability of ion-pairs in aqueous solutions, explicit water molecules have to be included in the model calculations.

  3. Perchlorate production by photodecomposition of aqueous chlorine solutions.

    PubMed

    Rao, Balaji; Estrada, Nubia; McGee, Shelly; Mangold, Jerry; Gu, Baohua; Jackson, W Andrew

    2012-11-06

    Aqueous chlorine solutions (defined as chlorine solutions (Cl(2,T)) containing solely or a combination of molecular chlorine (Cl(2)), hypochlorous acid (HOCl), and hypochlorite (OCl(-))) are known to produce toxic inorganic disinfection byproduct (e.g., chlorate and chlorite) through photoactivated transformations. Recent reports of perchlorate (ClO(4)(-)) production-a well-known thyroid hormone disruptor- from stored bleach solutions indicates the presence of unexplored transformation pathway(s). The evaluation of this potential ClO(4)(-) source is important given the widespread use of aqueous chlorine as a disinfectant. In this study, we perform detailed rate analysis of ClO(4)(-) generation from aqueous chlorine under varying environmental conditions including ultraviolet (UV) light sources, intensity, solution pH, and Cl(2,T) concentrations. Our results show that ClO(4)(-) is produced upon UV exposure of aqueous chlorine solutions with yields ranging from 0.09 × 10(-3) to 9.2 × 10(-3)% for all experimental conditions. The amount of ClO(4)(-) produced depends on the starting concentrations of Cl(2,T) and ClO(3)(-), UV source wavelength, and solution pH, but it is independent of light intensity. We hypothesize a mechanistic pathway derived from known reactions of Cl(2,T) photodecomposition that involves the reaction of Cl radicals with ClO(3)(-) to produce ClO(4)(-) with calculated rate coefficient (k(ClO4-)) of (4-40) × 10(5) M(-1) s(-1) and (3-250) × 10(5) M(-1) s(-1) for UV-B/C and UV-A, respectively. The measured ClO(4)(-) concentrations for both UV-B and UV-C experiments agreed well with our model (R(2) = 0.88-0.99), except under UV-A light exposure (R(2) = 0.52-0.93), suggesting the possible involvement of additional pathways at higher wavelengths. Based on our results, phototransformation of aqueous chlorine solutions at concentrations relevant to drinking water treatment would result in ClO(4)(-) concentrations (~0.1 μg L(-1)) much below the proposed

  4. Water Evaporation from Acoustically Levitated Aqueous Solution Droplets.

    PubMed

    Combe, Nicole A; Donaldson, D James

    2017-09-28

    We present a systematic study of the effect of solutes on the evaporation rate of acoustically levitated aqueous solution droplets by suspending individual droplets in a zero-relative humidity environment and measuring their size as a function of time. The ratios of the early time evaporation rates of six simple salts (NaCl, NaBr, NaNO3, KCl, MgCl2, CaCl2) and malonic acid to that of water are in excellent agreement with predictions made by modifying the Maxwell equation to include the time-dependent water activity of the evaporating aqueous salt solution droplets. However, the early time evaporation rates of three ammonium salt solutions (NH4Cl, NH4NO3, (NH4)2SO4) are not significantly different from the evaporation rate of pure water. This finding is in accord with a previous report that ammonium sulfate does not depress the evaporation rate of its solutions, despite reducing its water vapor pressure, perhaps due to specific surface effects. At longer evaporation times, as the droplets approach crystallization, all but one (MgCl2) of the solution evaporation rates are well described by the modified Maxwell equation.

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

    PubMed

    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.

  6. Radiolytic degradation of malathion and lindane in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mohamed, K. A.; Basfar, A. A.; Al-Kahtani, H. A.; Al-Hamad, K. S.

    2009-11-01

    Degradation of malathion and lindane pesticides present in an aqueous solution was investigated on a laboratory scale upon gamma-irradiation from a 60Co source. The effects of pesticide group, presence of various additives and absorbed dose on efficiency of pesticide degradation were investigated. Gamma-irradiation was carried out in distilled water solutions (malathion and lindane) and in combination with humic solution (HS), nitrous oxide (N 2O) and HS/N 2O (lindane) over the range 0.1-2 kGy (malathion) and 5-30 kGy (lindane). Malathion was easily degraded at low absorbed doses compared to lindane in distilled water solutions. Absorbed doses required to remove 50% and 90% of initial malathion and lindane concentrations in distilled water solutions were 0.53 and 1.77 kGy (malathion) and 17.97 and 28.79 kGy (lindane), respectively. The presence of HS, N 2O and HS/N 2O additives in aqueous solutions, significantly improved the effectiveness of radiolytic degradation of lindane. Chemical analysis of the pesticides and the by-products resulted from the radiolytic degradation were made using a gas chromatography associated with mass spectrometry (GC-MS). Additionally, the final degradation products of irradiation as detected by ion chromatography (IC) were acetic acid and traces of some anions (phosphate and chloride).

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

    PubMed

    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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Separate determination of nitrophenols and aminophenols in aqueous solutions

    SciTech Connect

    Korenman, Y.I.; Bortnikova, R.N.; Nefedova, T.A.; Sotnikova, N.G.

    1985-05-01

    Nitro and aminophenols are widely distributed, highly toxic components of waste waters from the phenolic industry. This article proposes a rapid extraction photometric method for determination of the most widespread isomers of nitro and aminophenols (ortho-substituted). Preliminary separation of the components being determined is based on the substantial difference in the ability of 2-nitrophenol and 2-aminophenol to be extracted from aqueous solutions by organic solvents. It is shown that the distribution coefficient for 2-nitrophenol in the system dibutyl ether-water is almost 40 times larger than the corresponding value for 2-aminophenol. The method described made possible the determination of 2-nitrophenol and 2-aminophenol in aqueous solution after their separation with satisfactory accuracy. The maximum error for the determination of 2-aminophenol was 12% and for 2-nitrophenol, 4%.

  9. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution, II

    NASA Astrophysics Data System (ADS)

    Saita, Takao; Matumura, On

    1983-08-01

    It has been found that Na-PAA molecules in dilute aqueous solution are degraded by shearing stress, oxidation and photolysis during usual viscosity measurements with a capillary viscometer. The results of previous viscosity measurements, mainly about the mechanochemical degradation in air and in air-free conditions, showed that the degradation rate increases with increasing shear stress, and with decreasing polymer concentration. In this work, the effects of the molecular weight and temperature on the degradation rate are measured using a capillary viscometer in air, and the photodegradation of Na-PAA and PAA in aqueous solution irradiated with UV light are studied by viscosity measurements in air, and by UV absorption and ESR methods. The results show that the degradation of molecules is enhanced by an increase in the molecular weight and strongly accelerated by a rise in temperature and by UV irradiation, and is accompanied by free-radical chain reactions.

  10. Laser purification of ultradispersed diamond in aqueous solution

    SciTech Connect

    Dolgaev, Sergei I; Kirichenko, N A; Lubnin, Evgenii N; Simakin, Aleksandr V; Shafeev, Georgii A; Kulevskii, L A

    2004-09-30

    The effect of pulsed radiation from a 2.92-{mu}m, 130-ns Cr{sup 3+}:Yb{sup 3+}:Ho{sup 3+}:YSGG holmium laser and a 510-nm, 20-ns copper vapour laser on an aqueous suspension of ultradispersed diamond is studied. X-ray photoelectron spectroscopy and electron energy loss spectroscopy revealed that exposure of the suspension to holmium laser radiation reduces the concentration of nondiamond carbon impurity in it. This is due to the dissolution of carbon impurity in supercritical aqueous solution, caused by radiation absorption. Dissolution of the nondiamond fraction may serve as an indicator of the solution being in the supercritical state as a result of laser irradiation of liquids. This process can be used for efficient purification of ultradispersed diamonds. (laser applications and other topics in quantum electronics)

  11. Interaction between pirenoxine and bovine serum albumin in aqueous solution.

    PubMed

    Liao, Zhixi; Yu, Xianyong; Yao, Qing; Yi, Pinggui

    2014-08-14

    This work concerns the interaction of prenoxine sodium (PRX) and bovine serum albumin (BSA), which was conducted by spectroscopic means: fluorescence spectra, ultraviolet-visible spectra (UV-vis) and circular dichroism spectra (CD spectra) in physiological conditions. The results revealed the PRX can quench the fluorescence of BSA remarkably in aqueous solution. The quench mechanism has been obtained after corrected the fluorescence intensities for inner filter effects. The binding constants (Ka) were calculated according to the relevant fluorescence data at different temperatures. Moreover, from a series of analyses, we have obtained the binding sites, the binding distance and binding force. The effect of PRX on the conformation of BSA has been analyzed using synchronous fluorescence under experimental conditions. In addition, the CD spectra proved that the secondary structure of BSA changed in the presence of PRX in aqueous solution.

  12. Interaction between pirenoxine and bovine serum albumin in aqueous solution

    NASA Astrophysics Data System (ADS)

    Liao, Zhixi; Yu, Xianyong; Yao, Qing; Yi, Pinggui

    2014-08-01

    This work concerns the interaction of prenoxine sodium (PRX) and bovine serum albumin (BSA), which was conducted by spectroscopic means: fluorescence spectra, ultraviolet-visible spectra (UV-vis) and circular dichroism spectra (CD spectra) in physiological conditions. The results revealed the PRX can quench the fluorescence of BSA remarkably in aqueous solution. The quench mechanism has been obtained after corrected the fluorescence intensities for inner filter effects. The binding constants (Ka) were calculated according to the relevant fluorescence data at different temperatures. Moreover, from a series of analyses, we have obtained the binding sites, the binding distance and binding force. The effect of PRX on the conformation of BSA has been analyzed using synchronous fluorescence under experimental conditions. In addition, the CD spectra proved that the secondary structure of BSA changed in the presence of PRX in aqueous solution.

  13. SANS simulation of aggregated protein in aqueous solution

    NASA Astrophysics Data System (ADS)

    Sugiyama, Masaaki; Hamada, Kei; Kato, Koichi; Kurimoto, Eiji; Okamoto, Kenta; Morimoto, Yukio; Ikeda, Susumu; Naito, Sachio; Furusaka, Michihiko; Itoh, Keiji; Mori, Kazuhiro; Fukunaga, Toshiharu

    2009-02-01

    Small-angle neutron scattering (SANS) of aggregated protein in an aqueous solution is simulated based on the crystallographic data of the protein. After obtaining the crystallographic data of the target protein, hydrogen atoms are added to the data and then some hydrogen atoms are replaced with deuterium atoms. The structure models are made with this data and then their gyration radii and SANS intensities are calculated. Compared the calculated SANS data with the experimental one, the most probable structure is determined. With this analysis method, the aggregate structure of proteasome α7-subunit (PRSα) in an aqueous solution was investigated. Three structural models, a simple monomer and two types of dimers, were supposed as the aggregated structure of PRSα. The analysis showed that the best compromised structure was the dimer, which was consistent with electron microscopy observation.

  14. Adsorption analysis of ammonia in an aqueous solution

    SciTech Connect

    Arman, B.; Panchal, C.B.

    1993-08-01

    An analysis is carried out to determine the effects of the diffusional resistance on the rate of the adsorption of ammonia in an aqueous solution. A performance prediction model is developed to calculate the local rate of heat and mass transfer, including physical and thermodynamic property calculations of the mixture. An algorithm is developed for calculating the interfacial conditions. The local heat- and mass-transfer calculation is then incorporated into the performance prediction method for adsorption for a given geometry.

  15. Freezing and thawing of aqueous solutions in emulsions

    NASA Astrophysics Data System (ADS)

    Hauptmann, Astrid; Handle, Karl; Hölzl, Georg; Loerting, Thomas

    2016-04-01

    The freezing behaviour of aqueous solutions in different emulsions is investigated by analytical methods such as differential scanning calorimetry and optical cryomicroscopy. We show that freezing temperature, freeze concentration and correspondingly cold-crystallization and melting change depending on the properties of the surrounding oil and emulsifier, size distribution of emulsified droplets and the parameters of emulsification. Relevance to freezing of cloud droplets is discussed.

  16. Formation and reactivity of phenylperoxyl radicals in aqueous solutions

    SciTech Connect

    Alfassi, Z.B.; Marguet, S.; Neta, P. )

    1994-08-18

    The reaction of phenyl radicals with oxygen, to produce phenylperoxyl radicals, and the reactions of several phenylperoxyl radicals with a number of organic compounds in aqueous solutions have been studied by pulse radiolysis. Phenyl radicals were produced by reduction of aryl halides with hydrated electrons. The rate constant for the reaction of 4-carboxyphenyl with O[sub 2] was determined from the rate of buildup of the peroxyl radical absorption at 520 nm as a function of [O[sub 2

  17. An MD Simulation of Concentrated Aqueous Solutions of Caesium Iodide

    NASA Astrophysics Data System (ADS)

    Tamura, Y.; Ohtaki, H.; Okada, I.

    1991-12-01

    Molecular dynamics simulations of concentrated aqueous Csl solutions have been performed for Csl: H2O = 1:20 (2.78 molal) at 298 K and 341 K and 1:10 (5.56 molal) at 349 K. Effects of temperature and concentration on the structures of the hydrated ions, the ion pairs, and ionic aggregates are discussed by comparing the results with X-ray diffraction data obtained under similar conditions [1

  18. Relationship between supercooling stability and solution structure in sodium acetate aqueous solution

    NASA Astrophysics Data System (ADS)

    Machida, Hironobu; Sugahara, Takeshi; Hirasawa, Izumi

    2017-10-01

    We have observed the solution structure of the supercooled sodium acetate aqueous solution, especially for the existence of clusters and their crystallization process, by means of Scanning electron microscopy (SEM) with the freeze replica method. Microscopic internal structure of sodium acetate trihydrate crystals mainly constitutes the aggregates of 100-200 nm in diameter, which consists of the clusters of 10-20 nm in diameter. In the case of a supercooled aqueous solution of 293 K, two types of aspect in the vitrified aqueous solution mainly exist: one is the clusters of 10-20 nm in diameter; the other is the smooth zone without any structure. At 263 K, the relationship among clusters of 10-20 nm and their aggregates of 100-200 nm was clearly observed. The aggregates construct the three-dimensional loose networks, which are not fully packed, different from the crystal.

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

    PubMed

    Kemer, Baris; Ozdes, Duygu; Gundogdu, Ali; Bulut, Volkan N; Duran, Celal; Soylak, Mustafa

    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 1h. Thermodynamic parameters including the Gibbs free energy (DeltaG degrees ), enthalpy (DeltaH degrees ), and entropy (DeltaS degrees ) revealed that adsorption of fluoride ions on the p-WM was feasible, spontaneous and endothermic in the temperature range of 0-40 degrees 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.

  20. Aqueous ozone solutions for pesticide removal from potatoes.

    PubMed

    Heleno, Fernanda F; de Queiroz, Maria Eliana Lr; Faroni, Lêda Ra; Neves, Antônio A; de Oliveira, André F; Costa, Luiz Pl; Pimenta, Gustavo G

    2016-12-01

    The presence of pesticide residues in potatoes is of concern because of the potential impact to human health due to the high consumption of this vegetable. In this study, aqueous solutions with and without ozone saturation as postharvest wash treatment at pH 4.0, 7.0, and 9.0 were tested to remove chlorothalonil from potatoes. The method used for pesticide analysis has been validated, presenting recovery values of 94-103%, with variations in the repeatability coefficients of ≤10.6%, and a quantification limit of 0.05 mg kg(-1) Regardless of pH, treatment with aqueous ozone solutions removed 70-76% of the pesticide present in the potato. In the no-ozone treatments, the percentage average removal of chlorothalonil residues in potatoes was only 36%. Over 24 days of storage, the quality of potatoes washed with aqueous ozone solutions was not significantly different from those washed with pure water. © The Author(s) 2016.

  1. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution.

  2. Solubility of volatile organic compounds in aqueous ammonia solution.

    PubMed

    Görgényi, Miklós; Dewulf, Jo; Van Langenhove, Herman; Király, Zoltán

    2005-05-01

    The Ostwald solubility coefficient, L of 17 volatile organic compounds (VOCs) from the gas phase into water and dilute aqueous ammonia solutions was determined by the equilibrium partitioning in closed system-solid phase micro extraction (EPICS-SPME) method at 303 K and at 0-2.5 mol dm(-3) ammonia concentrations. Ammonia increased the solubility of all VOCs nearly linearly, but to a different extent. The difference in the solubility values in aqueous ammonia solutions (Lmix) compared to pure water (L) is explained on the basis of a Linear Solvation Energy Relationship (LSER) equation made applicable for solvent mixtures, logLmix - logL = x((sNH3 - sH2O)pi2H + (aNH3 - aH2O)Sigma2H + (bNH3 - bH2O)Sigmabeta2H + (vNH3 - VH2O)Vx). sNH3 - sH2O, aNH3 - aH2O, bNH3 - bH2O, vNH3 - vH2O are the differences of solvent parameters, x is the mole fraction, pi2H is the solute dipolarity-polarizability, Sigmaalpha2H is the effective hydrogen bond acidity of the solute, Sigmabeta2H is the effective hydrogen bond basicity of the solute and Vx, the McGowan characteristic volume. The most significant term was v, the phase hydrophobicity. The solubility behavior was explained by the change in structure of the aqueous solution: the presence of ammonia reduces the cavity effect. These findings show that the presence of compounds such as ammonia, frequently observed in environmental waters, especially wastewaters, affect the fugacity of VOCs, having consequences for the environmental partitioning of VOCs and having technical consequences towards wastewater treatment technologies.

  3. Oxidation of ammonium sulfite in aqueous solutions using ozone technology

    NASA Astrophysics Data System (ADS)

    Li, Yue; Shang, Kefeng; Lu, Na; Li, Jie; Wu, Yan

    2013-03-01

    How to deal with unstable ammonium sulfite, the byproduct of flue gas desulfuration by ammonia absorption methods, has been a difficult problem in recent years. Oxidation of ammonium sulfite in aqueous solutions using ozone produced by a surface discharge system was investigated in the paper. The oxidation efficiency of ammonium sulfite by ozone and traditional air aeration were compared, and the factors including ozone concentration, gas flow rate, initial concentration of ammonium sulfite solution and reaction temperature were discussed. The results show that the oxidation efficiency of ammonium sulfite by ozone technology reached nearly 100% under the optimum conditions, which had a significant increase compared with that by air aeration.

  4. Preparation of thin ceramic films via an aqueous solution route

    DOEpatents

    Pederson, Larry R.; Chick, Lawrence A.; Exarhos, Gregory J.

    1989-01-01

    A new chemical method of forming thin ceramic films has been developed. An aqueous solution of metal nitrates or other soluble metal salts and a low molecular weight amino acid is coated onto a substrate and pyrolyzed. The amino acid serves to prevent precipitation of individual solution components, forming a very viscous, glass-like material as excess water is evaporated. Using metal nitrates and glycine, the method has been demonstrated for zirconia with various levels of yttria stabilization, for lanthanum-strontium chromites, and for yttrium-barium-copper oxide superconductors on various substrates.

  5. Radiolysis of berberine or palmatine in aqueous solution

    NASA Astrophysics Data System (ADS)

    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.

  6. Ice nucleation and supercooling behavior of polymer aqueous solutions.

    PubMed

    Kimizuka, Norihito; Viriyarattanasak, Chotika; Suzuki, Toru

    2008-02-01

    We determined the homogeneous nucleation temperature depression, DeltaT(f,hom), the equilibrium melting point depression, DeltaT(m), and the value lambda, which can be obtained from the linear relationship DeltaT(f,hom)=lambdaDeltaT(m), for aqueous solutions of PEG (200-20,000 g mol(-1)), PVP (10,000, 35,000, 40,000 g mol(-1)), and dextran (10,000 g mol(-1)) in the concentration range 0-40 wt% using the emulsion method. The molecular weight dependence of T(f,hom), T(m), and lambda in PEG aqueous solutions was found to change in the vicinity of Mw 600-1540 at all concentrations. In addition, it was confirmed that for all of the polymers studied, there was a good linear relationship between lambda and the logarithmic value of the self-diffusion coefficient D(0) of the solute molecule. These results indicate that the parameters that describe non-equilibrium freezing, such as T(f,hom) and lambda, are dependent on solution properties such as viscosity and self-diffusion of solute molecules.

  7. Association of riboflavin, caffeine, and sodium salicylate in aqueous solution

    NASA Astrophysics Data System (ADS)

    Baranovskii, S. F.; Bolotin, P. A.

    2007-03-01

    We have used UV and visible spectrophotometry to study self-association of aromatic riboflavin molecules (RFN, vitamin B2, 7,8-dimethyl-10-N-(1'-D-ribityl)isoalloxazine) in aqueous solution (pH 6.86) at T = 298 K, using a dimer model. We have determined the equilibrium dimerization constant for riboflavin, KdB = 125 ± 40 M-1. We have studied heteroassociation in the system of molecules of 7,8-dimethyl-10-ribitylisoalloxazine with 1,3,7-trimethylxanthine (caffeine) and sodium salicylate (NAS) in aqueous solution (pH 6.86; T = 298 K). We have determined the heteroassociation constants for RFN-NAS and RFN-caffeine molecules in the absence and in the presence of urea in solutions using a modified Benesi-Hildebrand equation: 25 ± 4, 17 ± 3, and 74 ± 11, 53 ± 7 M-1 respectively. We have determined the dimerization constants for NAS (2.7 ± 0.5 M-1) and caffeine (17.0 ± 1.5 M-1). We conclude that heteroassociation of the aromatic molecules leads to a lower effective riboflavin concentration in solution, and the presence of urea in mixed solutions leads to an decrease in the complexation constants for the RFN-NAS and RFN-caffeine systems.

  8. Structure of concentrated aqueous solutions of scandium chloride

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  10. Thermal analysis of a growing crystal in an aqueous solution

    NASA Astrophysics Data System (ADS)

    Shiomi, Yuji; Kuroda, Toshio; Ogawa, Tomoya

    1980-10-01

    The temperature profiles around growing crystals in aqueous solutions of Rochelle salt were measured with accuracy of 0.005°C in a two-dimensional cell which was used for elimination of thermal convection current in the cell. The temperature distribution became stationary after 2 h from injection of the mother liquid, but the concentration distribution did not become stationary because the diffusion constant of solute in the solution was much smaller than the thermal diffusivity of the solution. The growth rate was linearly proportional to the temperature gradient at every growing interface. Since crystal growth is a typical interaction process between thermal and material flow, the experimental results were analysed by such an interaction model. The analysis confirms that the material flow is limited by diffusion within a layer width of about a few hundreds micrometers on the growing interface.

  11. On the structure of an aqueous propylene glycol solution

    NASA Astrophysics Data System (ADS)

    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.

  12. On the structure of an aqueous propylene glycol solution.

    PubMed

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

    2016-12-14

    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.

  13. Method of solidifying waste materials, such as radioactive or toxic materials, contained in aqueous solutions

    SciTech Connect

    Knieper, J.; May, K.; Printz, H.

    1984-07-24

    A method is disclosed of solidifying waste materials, such as radioactive or toxic materials, which are contained in aqueous solutions. To accomplish this solidification, an inorganic, non-metallic binding agent such as gypsum is intermixed with the aqueous solution and a substance such as pumice or ceramic tile which promotes the intermixing of the binding agent and the aqueous solution.

  14. Efficient removal of naphthalene-2-ol from aqueous solutions by solvent extraction.

    PubMed

    Shao, Jingjing; Cheng, Yan; Yang, Chunping; Zeng, Guangming; Liu, Wencan; Jiao, Panpan; He, Huijun

    2016-09-01

    Naphthalene-2-ol is a typical biologically recalcitrant pollutant in dye wastewater. Solvent extraction of naphthalene-2-ol from aqueous solutions using mixed solvents was investigated. Various extractants and diluents were evaluated, and the effects of volume ratio of extractant to diluent, initial pH, initial concentration of naphthalene-2-ol in aqueous solution, extraction time, temperature, volume ratio of organic phase to aqueous phase (O/A), stirring rate and extraction stages, on extraction efficiency were examined separately. Regeneration and reuse of the spent extractant were also investigated. Results showed that tributyl phosphate (TBP) achieved 98% extraction efficiency for naphthalene-2-ol in a single stage extraction, the highest among the 12 extractants evaluated. Extraction efficiency was optimized when cyclohexane and n-octane were used as diluents. The solvent combination of 20% TBP, 20% n-octanol and 60% cyclohexane (V/V) obtained the maximum extraction efficiency for naphthalene-2-ol, 99.3%, within 20min using three cross-current extraction stages under the following extraction conditions: O/A ratio of 1:1, initial pH of 3, 25°C and stirring rate of 150r/min. Recovery of mixed solvents was achieved by using 15% (W/W) NaOH solution at an O:A ratio of 1:1 and a contact time of 15min. The mixed solvents achieved an extraction capacity for naphthalene-2-ol stably higher than 90% during five cycles after regeneration.

  15. Protein Conformation and Supercharging with DMSO from Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Sterling, Harry J.; Prell, James S.; Cassou, Catherine A.; Williams, Evan R.

    2011-07-01

    The efficacy of dimethyl sulfoxide (DMSO) as a supercharging reagent for protein ions formed by electrospray ionization from aqueous solution and the mechanism for supercharging were investigated. Addition of small amounts of DMSO to aqueous solutions containing hen egg white lysozyme or equine myoglobin results in a lowering of charge, whereas a significant increase in charge occurs at higher concentrations. Results from both near-UV circular dichroism spectroscopy and solution-phase hydrogen/deuterium exchange mass spectrometry indicate that DMSO causes a compaction of the native structure of these proteins at low concentration, but significant unfolding occurs at ~63% and ~43% DMSO for lysozyme and myoglobin, respectively. The DMSO concentrations required to denature these two proteins in bulk solution are ~3-5 times higher than the concentrations required for the onset of supercharging, consistent with a significantly increased concentration of this high boiling point supercharging reagent in the ESI droplet as preferential evaporation of water occurs. DMSO is slightly more basic than m-nitrobenzyl alcohol and sulfolane, two other supercharging reagents, based on calculated proton affinity and gas-phase basicity values both at the B3LYP and MP2 levels of theory, and all three of these supercharging reagents are significantly more basic than water. These results provide additional evidence that the origin of supercharging from aqueous solution is the result of chemical and/or thermal denaturation that occurs in the ESI droplet as the concentration of these supercharging reagents increases, and that proton transfer reactivity does not play a significant role in the charge enhancement observed.

  16. The radiolysis of bromophenol blue in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Abdel Rahim, F.; Eid, S. A.; Souka, N.; McLaughlin, W. L.

    The effect of gamma radiation on the color intensity of aerated and oxygenated aqueous solution of bromophenol blue (BPB) was investigated. Ionizing radiation at increasing absorbed doses ( D) brought about gradual bleaching (i.e. decrease in optical absorbance, -Δ A) of bromophenol blue solutions. The molar extinction coefficients of acidic, neutral, and alkaline solutions were measured and found to be independent of temperature during spectrophotometry between 20 and 40°C. Aerated and oxygen-saturated acidic solutions showed a linear response -Δ A vs D) up to doses of 2.4 and 2.1 kGy, respectively. Aerated alkaline solutions on the other hand showed a linear response up to 4.8 kGy. The decoloration yields for 5 × 10 -5 M bromophenol blue aqueous solutions, G(-BPB), obtained from the decrease in absorbance at 591 nm wavelength for acidic, neutral, and alkaline solutions, were 0.244, 0.113, and 0.098 (100 eV) -1, respectively. The first-order rate constant for the reaction of OH radical with bromophenol, obtained from competition reactions with ethanol at pH 4, was found to be 9.1 +- 1.2 × 10 9 M -1 s -1. The degree of decoloration of bromophenol blue in acidic solutions was found to decrease upon the addition of ethanol, G(-BPB) decreasing from 0.24 to 0.088 upon the addition of ethanol at a concentration of 10 -2M. Suggestions are made for possible radiation dosimetry in the dose range (0.1-5 kGy) by means of spectrophotometric analysis of absorption spectra.

  17. PHARMACEUTICALS AS UBIQUITOUS POLLUTANTS: SIGNIFICANCE, CONCERNS, SOLUTIONS

    EPA Science Inventory

    Those chemical pollutants that are regulated under various international, federal, and state programs represent but a small fraction of the universe of chemicals that occur in the environment as a result of both natural processes and human influence. Although this galaxy of targe...

  18. PHARMACEUTICALS AS UBIQUITOUS POLLUTANTS: SIGNIFICANCE, CONCERNS, SOLUTIONS

    EPA Science Inventory

    Those chemical pollutants that are regulated under various international, federal, and state programs represent but a small fraction of the universe of chemicals that occur in the environment as a result of both natural processes and human influence. Although this galaxy of targe...

  19. Osmotic potential calculations of inorganic and organic aqueous solutions over wide solute concentration levels and temperatures.

    PubMed

    Cochrane, T T; Cochrane, T A

    2016-01-01

    To demonstrate that the authors' new "aqueous solution vs pure water" equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures. The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of "free" water molecules per unit volume of solution, "Nf," and (c) the "t" factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate Nf was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors' equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures. The provisional equations formulated to calculate Nf, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of Nf using recorded relative density data at 20 °C. They were

  20. Ultrasound response of aqueous poly(ionic liquid) solution.

    PubMed

    Li, Kai; Kobayashi, Takaomi

    2016-05-01

    Ultrasound (US) effects on aqueous poly(ionic liquid) (PIL) solution were investigated using viscosity and FT-IR spectroscopy after exposure to US of 23, 43, and 96 kHz frequencies at 50 W. The viscosity of the poly(1-vinyl-3-butyl-imidazolium chloride) (PIL) aqueous solution decreased during exposure to US. It then increased gradually within about 10 min as US stopped. The aqueous PIL behavior was then observed using FT-IR spectroscopy. The US exposure enhanced the FT-IR band intensity of the OH stretching. The band intensity returned to its original value after the US stopped. These results responded cyclically to the US on/off. Analysis of the FT-IR spectra revealed that US influenced the breakage and reformation of hydrogen bonds in the PIL and water. Two-dimensional correlation and deconvolution were used to analyze the change of components in the region of 3000-3700 cm(-1) for US exposure. Results of these analyses suggest that US exposure might break hydrogen bonds between PIL segments and water. In the absence of US, hydrogen bonds reformation was also observed between the PIL and water. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Stability of metal oxide nanoparticles in aqueous solutions.

    PubMed

    Tso, Chih-ping; Zhung, Cheng-min; Shih, Yang-hsin; Tseng, Young-Ming; Wu, Shian-chee; Doong, Ruey-an

    2010-01-01

    The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. With increasing amount of commercial nanoparticles released into nature, their fate and effects on the ecosystem and human health are of growing concern. This study investigated the stability and morphology of three metal oxide nanoparticles in aqueous solutions. The commercially available nanoparticles, TiO(2), ZnO, SiO(2), aggregated quickly into micrometer-size particles in aqueous solutions, which may not threaten human health. Their changes in morphology and characteristics were further examined by dynamic light scattering (DLS) method and transmission electron microscopy (TEM). Among the several dispersion approaches, ultrasonication was found to be the most effective for disaggregating nanoparticles in water. For these three selected nanoparticles, ZnO could not remain stable in suspensions, presumably due to the dissolution of particles to form high concentration of ions, resulting in enhanced aggregation of particles. In addition, the existence of dissolved organic matters stabilized nanoparticles in lake water and wastewater for several hours in spite of the high concentration of cations in these real-water samples. The fate of metal oxide nanoparticles in natural water bodies would be determined by the type and concentration of cations and organic matters. Results obtained in this study revealed that the stability of nanoparticles changed under different aqueous conditions and so did their fate in the environment.

  2. Dielectric properties of solutions of oil materials solubilized by sodium dodecyl sulfate in aqueous solutions

    SciTech Connect

    Abe, M.; Shimizu, A.; Ogino, K.

    1982-08-01

    One of the most important properties of micellar systems is their ability to solubilize a variety of species. For aqueous micelles, solubilization is related closely to the hydrophobic and hydrophilic properties of the solubilizate. Different sites of solubilization and orientations may be involved, depending on the structure of the solubilizate. A number of studies on solubilization have been performed experimentally and theoretically. Dielectric constant measurement has proved to be a powerful tool for the investigation of permanent dipole moments of various molecules and of the behavior in solution of various substances, and has been applied in various fields. This technique has been used to determine the chemical structure of surfactants, but not to investigate the solubilization of oily materials in aqueous solution. The dielectric constants and ac electric conductivities observed when a solubilizate is added to an aqueous solution of an anionic surfactant and the differences in the solubilizing behavior due to different kinds of polar groups are discussed. 30 references.

  3. Equilibrium modeling of cadmium biosorption from aqueous solution by compost.

    PubMed

    Ahmad, Iftikhar; Akhtar, Muhammad Javed; Jadoon, Iram Bashir Khan; Imran, Muhammad; Imran, Muhammad; Ali, Shahid

    2017-02-01

    One of the most serious environmental issues of the present century is metal contamination of the aqueous environment due to the release of metal-containing effluents into the water bodies. Cadmium (Cd) is one of the toxic heavy metals which is not biodegradable thereby causing high risks to animals, plants, and humans. In the present study, potential and feasibility of compost derived from fruits and vegetables for Cd biosorption from aqueous solution were investigated. The batch biosorption experiments were performed to evaluate the effects of Cd concentrations (5, 15, 30, and 60 mg/L), compost biomass (0.5, 1.0, and 1.5 g/100 mL), pH (4, 6, and 8), contact time (1, 4, and 19 h), and temperature (28 and 35 °C) on Cd sorption and removal by compost. The biosorption of Cd was found to be highly dependent on initial Cd concentration, sorbent biomass, pH, contact time, and temperature of aqueous solution. It was observed that Cd sorption by compost was rapid up to 4 h, and then it became slow and stable as the contact time shifted towards equilibrium state (19 h). At equilibrium, the Cd sorption (q = 0.33-5.43 mg/g compost) and removal (45-99%) were observed at pH 6 and temperature 28 °C depending upon Cd concentrations and sorbent biomass in aqueous solution. The equilibrium experimental data were fitted well with Langmuir adsorption isotherm model (q max = 6.35-7.14 mg/g compost, R (2) = 0.77-0.98). FTIR spectrum of the compost indicated the presence of hydroxyl and carboxyl groups, which might be involved in the biosorption of Cd through ion exchange and complexation mechanisms. The optimal environmental conditions (pH 6, sorbent biomass 0.5 g/100 mL, and temperature 28 °C) induced more Cd sorption on compost at equilibrium. Results show compost as a cost-effective adsorbent material having high potential for heavy metal remediation from aqueous solution.

  4. Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Iraci, L. T.; Essin, A. M.; Golden, D. M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The global methanol budget is currently unbalanced, with source terms significantly larger than the sinks terms. To evaluate possible losses of gaseous methanol to sulfate aerosols, the solubility and reactivity of methanol in aqueous sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosols is under investigation. Methanol will partition into sulfate aerosols according to its Henry's law solubility. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H*, for cold (196 - 220 K) solutions ranging between 45 and 70 wt % H2SO4. We have found that methanol solubility ranges from approx. 10(exp 5) - 10(exp 7) M/atm for UT/LS conditions. Solubility increases with decreasing temperature and with increasing sulfuric acid content. Although methanol is slightly more soluble than are acetone and formaldehyde, current data indicate that uptake by clean aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These solubility measurements include uptake due to physical solvation and any rapid equilibria which are established in solution. 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 is not significant over our experimental time scale for solutions below 80 wt % H2SO4. To confirm this directly, results obtained using a complementary equilibrium measurement technique will also be presented.

  5. Opto-electrochemical spectroscopy of metals in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Habib, K.

    2016-03-01

    In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance-emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0%-2.5% H2SO4) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0%, 1.5%, 2.0%, and 2.5% H2SO4 solutions. The electrical resistance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

  6. Opto-electrochemical spectroscopy of metals in aqueous solutions

    SciTech Connect

    Habib, K.

    2016-03-15

    In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance–emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0%–2.5% H{sub 2}SO{sub 4}) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0%, 1.5%, 2.0%, and 2.5% H{sub 2}SO{sub 4} solutions. The electrical resistance–emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

  7. Photodegradation of 2-chloropyridine in aqueous solution: Reaction pathways and genotoxicity of intermediate products.

    PubMed

    Skoutelis, Charalambos; Antonopoulou, Maria; Konstantinou, Ioannis; Vlastos, Dimitris; Papadaki, Maria

    2017-01-05

    2-Chloropyridine, an important precursor of the chemical industry is also a persistent water pollutant. The genotoxicity of photolytically treated 2-chloropyridine aqueous solution to human lymphocytes initially increases and fluctuates during treatment finally reaching the control values after prolonged treatment. Intermediate products formed were identified; a kinetic scheme for their formation is presented. To identify the source of genotoxicity variations and the potential in vitro effects on human lymphocytes of the partially photo-treated aqueous solution, the genotoxicity of four (the only) commercially available intermediates, i.e., 1H-pyrrole-2-carboxaldehyde, 6-chloro-2-pyridinecarboxylic acid, 2,3-dichloropyridine and 2-pyridinecarbonitrile was measured; the obtained results were used for the reasoning on the variation of the solution genotoxic (including clastogenic as well as aneugenic) events and cytotoxic activity. It was found that 1H-pyrrole-2-carboxaldehyde and 6-chloro-2-pyridinecarboxylic acid were highly genotoxic even at the very low concentration measured here. Thus, they likely had a significant contribution to the photolytically treated solution genotoxicity. 2,3-Dichloropyridine was found to be genotoxic but only at concentrations higher than the ones measured in this work. Thus, it was not likely to have contributed to the solution genotoxicity. Finally, at the concentrations measured in this work 2-pyridinecarbonitrile was found to be only cytotoxic.

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

    NASA Astrophysics Data System (ADS)

    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

  9. Degradation of chelating agents in aqueous solution using advanced oxidation process (AOP).

    PubMed

    Sillanpää, Mika E T; Kurniawan, Tonni Agustiono; Lo, Wai-hung

    2011-06-01

    This article presents an overview with critical analysis of technical applicability of advanced oxidation process (AOP) in removing chelating agents from aqueous solution. Apart from the effect of metals for chelating agents as a major influencing factor, selected information such as pH, oxidant's dose, concentrations of pollutants and treatment performance is presented. The performance of individual AOP is compared. It is evident from our literature survey that photocatalysis with UV irradiation alone or coupled with TiO(2), ozonation and Fenton's oxidation are frequently applied to mineralize target pollutants. Overall, the selection of the most suitable AOP depends on the characteristics of effluents, technical applicability, discharge standard, regulatory requirements and environmental impacts.

  10. Advanced oxidation for the treatment of chlorpyrifos in aqueous solution.

    PubMed

    Ismail, M; Khan, Hasan M; Sayed, Murtaza; Cooper, William J

    2013-10-01

    Chlorpyrifos is an organophosphate pesticide and is significant because of its extensive use, persistence in the environment, wide distribution, and its toxicity may lead to lung and central nervous system damage, developmental and autoimmune disorders and vomiting. In the present study, the irradiation of chlorpyrifos in aqueous solution by (60)Co γ-rays was conducted on a laboratory scale and the removal efficiency of chlorpyrifos was investigated. The SPME-GC-ECD method was used for analysis of chlorpyrifos. Aqueous solutions of different concentrations of target compound (200-1000 μg L(-1)) were irradiated through 30-575 Gy. Gamma irradiation showed 100% degradation for a 500 μg L(-1) solution at an absorbed dose of 575 Gy (the dose rate was 300 Gy h(-1)). The radiolysis of chlorpyrifos was pseudo-first order (decay) with respect to dose. The dose constants determined in this study ranged from 8.2×10(-3) to 2.6×10(-2) Gy(-1), and decreased with an increase in the initial concentration of chlorpyrifos, while the radiation chemical yield (G-value) for the loss of chlorpyrifos was found to decrease with increasing absorbed dose. The effect of saturated solutions of N2 and N2O, and radical scavengers tert-butanol, iso-propanol, H2O2, NaNO3 and NaNO2 on the degradation of chlorpyrifos were also studied. The results showed that the oxidative OH was the most important in the degradation of chlorpyrifos, while the reductive radicals, aqueous electron and H, were of less importance for the degradation of chlorpyrifos. The inorganic by-products Cl(-), SO4(2-) and PO4(3-) were quantitatively determined by IC.

  11. Dynamic self-assembly of coordination polymers in aqueous solution.

    PubMed

    Li, Wen; Kim, Yongju; Li, Jingfang; Lee, Myongsoo

    2014-08-07

    The construction of supramolecular polymers has been intensively pursued because the nanostructures formed through weak non-covalent interactions can be triggered by external stimuli leading to smart materials and sensors. Self-assemblies of coordination polymers consisting of metal ions and organic ligands in aqueous solution also provide particular contributions in this area. The main motivation for developing those coordination polymers originates from the value-added combination between metal ions and ligands. This review highlights the recent progress of the dynamic self-assembly of coordination polymers that result from the sophisticated molecular design, towards fabricating stimuli-responsive systems and bio-related materials. Dynamic structural changes and switchable physical properties triggered by various stimuli are summarized. Finally, the outlook for aqueous nanostructures originated from the dynamic self-assembly of coordination polymers is also presented.

  12. Solubility of uranous sulfate in aqueous sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Suzuki, Shigeru; Hirono, Shuichiro; Awakura, Yasuhiro; Majima, Hiroshi

    1990-10-01

    To provide important thermodynamic data for use in uranium hydrometallurgy, solubilities of uranous sulfate were determined as a function of free acid concentration and temperature. Two sets of experiments were performed in this study. One set was the precipitation experiments of uranous sulfate crystals, in which concentrated uranous sulfate solution was mixed with sulfuric acid solution of suitable concentration. The other set was the dissolution experiments of uranous sulfate crystals in aqueous sulfuric acid solutions. It is noteworthy that good agreement exists between the solubilities determined by the two methods. At elevated temperatures, say, 363 K, the presence of free sulfuric acid is required to avoid precipitation of uranous hydroxide resulting from the hydrolysis of uranous sulfate. Generally speaking, however, an increase in free sulfuric acid concentration results in a slight decrease in uranous sulfate solubility. The elevation of solution temperature causes a decrease in solubility of uranous sulfate. It should be noted that the solid uranous sulfates equilibrated with saturated solutions at 298 K were U(SO4)2 2H2O in dilute sulfuric acid solution and U(SO4)2 4H2O in concentrated sulfuric acid solution, while those at 333 K and 363 K were mainly U(SO4)2 4H2O.

  13. Diffusion of Trehalose and Sucrose in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Feick, E.; von Meerwall, E.; Ekdawi, N.; de Pablo, J.

    2000-10-01

    Trehalose is emerging as superior substitute for sucrose in solution as a cryoprotectant, e. g., to preserve organs destined for transplantation. We have used the proton NMR pulsed-gradient spin-echo method between T = 30 and 85 deg. C to study the self-diffusion of solvent and solute in aqueous solutions of these molecules as function of their concentration, c. We find that both solute molecules diffuse substantially more slowly than water at corresponding c and T; that addition of water accelerates solute diffusion more rapidly than that of water; and that while at a given c and T water diffusion is insensitive to solute identity, trehalose diffusion is slower than sucrose diffusion. The latter effect increases with c, approaching a factor of two at the highest c. In these respects our results correspond closely to those of our extensive numerical simulations of these systems. Free-volume theory is employed to explore the cooperative kinetic interactions between solvent and solutes, and to account tentatively for part of the superiority of trehalose to sucrose as preservation agent. Differences in crystallization behavior also seem to be involved.

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

    PubMed

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    USGS Publications Warehouse

    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. Process for disposal of aqueous solutions containing radioactive isotopes

    DOEpatents

    Colombo, Peter; Neilson, Jr., Robert M.; Becker, Walter W.

    1979-01-01

    A process for disposing of radioactive aqueous waste solutions whereby the waste solution is utilized as the water of hydration to hydrate densified powdered portland cement in a leakproof container; said waste solution being dispersed without mechanical inter-mixing in situ in said bulk cement, thereafter the hydrated cement body is impregnated with a mixture of a monomer and polymerization catalyst to form polymer throughout the cement body. The entire process being carried out while maintaining the temperature of the components during the process at a temperature below 99.degree. C. The container containing the solid polymer-impregnated body is thereafter stored at a radioactive waste storage dump such as an underground storage dump.

  17. Rapid structural analysis of nanomaterials in aqueous solutions

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  18. Simulation of osmotic pressure in concentrated aqueous salt solutions.

    SciTech Connect

    Luo, Y.; Roux, B.; Univ. of Chicago

    2010-01-01

    Accurate force fields are critical for meaningful simulation studies of highly concentrated electrolytes. The ion models that are widely used in biomolecular simulations do not necessarily reproduce the correct behavior at finite concentrations. In principle, the osmotic pressure is a key thermodynamic property that could be used to test and refine force field parameters for concentrated solutions. Here we describe a novel, simple, and practical method to compute the osmotic pressure directly from molecular dynamics (MD) simulation of concentrated aqueous solutions by introducing an idealized semipermeable membrane. Simple models for Na+, K+, and Cl- are tested and calibrated to accurately reproduce the experimental osmotic pressure at high salt concentration, up to the solubility limit of 4-5 M. The methodology is general and can be extended to any type of solute as well as nonadditive polarizable force fields.

  19. Photobleaching mechanisms of Radachlorin photosensitizer in aqueous solution

    NASA Astrophysics Data System (ADS)

    Beltukova, D. M.; Vasyutinskii, O. S.; Glazov, A. L.; Semenova, I. V.; Smolin, A. G.

    2017-02-01

    The time dependence of the fluorescence intensity of aqueous solutions of Radachlorin photosensitizer at different concentrations and the influence of the dissolved oxygen concentration on the fluorescence dynamics are analyzed. The experimental results are interpreted based on the numerical solution of the system of kinetic equations describing the photochemical processes that lead to the formation and degradation of singlet oxygen in solution. The influence of possible mechanisms of photosensitizer photobleaching is analyzed. It is shown that the main photobleaching mechanism under our experimental conditions is the chemical reaction between the photosensitizer in the triplet state and dissolved oxygen molecules. Two rate constants of electron-transfer chemical reactions, which are important for understanding the nature of the occurring photoprocesses, are determined.

  20. Direct contact membrane distillation of sugar aqueous solutions

    SciTech Connect

    Izquierdo-Gil, M.A.; Garcia-Payo, M.C.; Fernandez-Pineda, C.

    1999-06-01

    Results are given from direct contact membrane distillation, using tangential flows to the membrane, with sugar aqueous solutions. Several effects on the distillation process are examined: flow rate through the cell, nature of the feed solutions, initial concentrations of the feed solutions, average temperature, and temperature difference. On the basis of enthalpy flux conservation in the different regions, various systems of equations are proposed for the estimation of the interfacial temperatures. Based on the known temperatures of the liquid-vapor interfaces, the experimental distillate fluxes for several sets are fitted to the gas stagnant film diffusion model to obtain the effective diffusion coefficients of the water vapor-air mixture, D{sub ef}, and the results are analyzed.

  1. The adsorption of nicotine from aqueous solutions on different zeolite structures.

    PubMed

    Rakić, Vesna; Damjanović, Ljiljana; Rac, Vladislav; Stosić, Dusan; Dondur, Vera; Auroux, Aline

    2010-03-01

    The present work is focused on the adsorption of nicotine from aqueous solutions. Based on the data available in the literature, serious concern is claimed regarding the appearance of nicotine in ground, surface and municipal wastewaters. In order to investigate the possibility of abatement by adsorption, three different types of zeolites (BEA, MFI and HEU) have been applied as adsorbents. In addition, the adsorption was performed on activated carbon, a solid customarily used for removal of pollutants from water. The adsorption of nicotine was studied by isothermal microcalorimetry, which provided the heats evolved as a result of adsorption. The values of these heats revealed that the investigated solids are energetically heterogeneous for the adsorption of nicotine from aqueous solution. Additionally, the amounts of adsorbed pollutant were determined and presented in the form of adsorption isotherms. The obtained adsorption isotherms were interpreted using Langmuir, Freundlich, and Sips equations; the latter was found to express high level of agreement with experimental data of nicotine adsorption on the investigated solids. The possibilities to regenerate the adsorbents were examined by means of thermogravimetry coupled with mass spectrometry. From all obtained results, it was possible to distinguish zeolite BEA as a material which possesses the capacity for adsorption of nicotine comparable to that of activated carbon.

  2. Removal of selected pollutants from aqueous media by hardwood mulch.

    PubMed

    Ray, Asim B; Selvakumar, Ariamalar; Tafuri, Anthony N

    2006-08-21

    Generic hardwood mulch, usually used for landscaping, was utilized to remove several selected pollutants (heavy metals and toxic organic compounds) typically found in urban stormwater (SW) runoff. The hardwood mulch sorbed all the selected pollutants from a spiked stormwater mixture, including copper (Cu(2+)), cadmium (Cd(2+)), chromium (Cr(6+)), lead (Pb(2+)), zinc (Zn(2+)), 1,3 dichlorobenzene (DCB), naphthalene (NP), fluoranthene (FA), butylbenzylphthalate (BBP), and benzo(a)pyrene (B[a]P). Masses of the pollutants sorbed depended upon the pollutant species, contact time, and initial concentration which varied from 20 to 100%. Sorption rates of the metals, in general, were more rapid than those of the organics; however, mass removals (percent) of the organics, in contrast to those of the metals, were independent of their initial concentrations. With the exception of Cd, percentages (weight) of the metals removed declined as their initial concentrations decreased. None of the sorbed pollutants desorbed to any significant extent upon extended washing with water. It is quite feasible that in the presence of mulch the uptake of these pollutants by the aquatic species will be reduced significantly.

  3. Efficient application of nano-TiO2 thin films in the photocatalytic removal of Alizarin Yellow from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Tiwari, Diwakar; Lalhriatpuia, C.; Lalhmunsiama; Lee, Seung-Mok; Kong, Sung-Ho

    2015-10-01

    The aim of this investigation is to obtain thin films of nano-TiO2 on a borosilicate glass substrate using sol-gel template method. The thin film was immobilized with and without polyethylene glycol as filler media and annealed at 500 °C. Further, thin films were characterized by the IR, XRD, XRF and XPS analytical methods. The surface morphology of these films was obtained by the FE-SEM images and the BET specific surface area and pore sizes were obtained. The nano-TiO2 was, perhaps, formed a nanopillar onto the substrate. The thin films were successfully employed in the photocatalytic degradation of Alizarin Yellow (AY), an azo dye, from aqueous solutions using the UV-light irradiation under batch reactor operations. Various physico-chemical parametric studies, viz., effect of pH, Alizarin Yellow concentration and interfering ions were studied to deduce the mechanism involved in photocatalytic degradation of this pollutant. The time dependence degradation of Alizarin Yellow was provided to demonstrate the kinetics of degradation of this pollutant from aqueous solutions. It was observed that the degradation of Alizarin Yellow followed pseudo-first-order rate kinetics. Study was further extended with total organic carbon measurement using TOC analyser to demonstrate an apparent mineralization of Alizarin Yellow from aqueous solutions. The presence of several interfering ions or even rad OH scavengers suppressed the photo-catalytic action of thin films in AY degradation from aqueous solutions.

  4. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles.

    PubMed

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4(2-), NO3(-) and Cl(-)); however, CO3(2-) exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.

  5. Nanoscale adhesive forces between silica surfaces in aqueous solutions.

    PubMed

    Troncoso, Paula; Saavedra, Jorge H; Acuña, Sergio M; Jeldres, Ricardo; Concha, Fernando; Toledo, Pedro G

    2014-06-15

    Nanoscale adhesive forces between a colloidal silica probe and a flat silica substrate were measured with an atomic force microscope (AFM) in a range of aqueous NaCl, CaCl2, and AlCl3 solutions, with concentrations ranging from 10(-)(6) to 10(-)(2) M at pH ∼5.1. Notably, the measured force curves reveal large pull-off forces in water which increase in electrolyte solutions, with jump-off-contact occurring as a gradual detachment of the probe from the flat substrate rather than as a sharp discontinuous jump. The measured force curves also show that the number and size of the steps increase with concentration and notably with electrolyte valence. For the higher concentration and valence the steps become jumps. We propose that these nanoscale adhesive forces between mineral surfaces in aqueous solutions may arise from newly born cavities or persistent subnanometer bubbles. Formation of cavities or nanobubbles cannot be observed directly in our experiments; however, we cannot disregard them as responsible for the discontinuities in the measured force data. A simple model based on several cavities bridging the two surfaces we show that is able to capture all the features in the measured force curves. The silica surfaces used are clean but not intentionally hydroxylated, as contact angle measurements show, and as such may be responsible for the cavities. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Reaction of lincosamide antibiotics with manganese oxide in aqueous solution.

    PubMed

    Chen, Wan-Ru; Ding, Yunjie; Johnston, Cliff T; Teppen, Brian J; Boyd, Stephen A; Li, Hui

    2010-06-15

    Lincosamides are among the most frequently detected antibacterial agents in effluents from wastewater treatment plants and surface runoff at agricultural production systems. Little is known about their transformations in the environment. This study revealed that manganese oxide caused rapid and extensive decomposition of clindamycin and lincomycin in aqueous solution. The reactions occurred mainly at the pyranose ring of lincosamides, initially by formation of complexes with Mn and cleavage of the ether linkage, leading to the formation of a variety of degradation products via subsequent hydrolytic and oxidative reactions. The results of LC-MS/MS and FTIR analysis confirm cleavage of the C-O-C bond in the pyranose ring, formation of multiple carbonyl groups, and transformation of the methylthio moiety to sulfur oxide. The overall transformation was controlled by interactions of cationic species of lincosamides with MnO(2) surfaces. The presence of electrolytes (i.e., NaCl, CaCl(2), and MnCl(2)) and dissolved organic matter in aqueous solution, and increase of solution pH, diminished lincosamide binding to MnO(2) hence reducing the rate and magnitude of the transformations. Results from this study indicate that manganese dioxides in soils and sediments could contribute to the decomposition of lincosamide antibiotics released into the environment.

  7. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles

    PubMed Central

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO42-, NO3- and Cl-); however, CO32- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions. PMID:26630014

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

    PubMed

    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

  9. Theoretical study of decomposition of methanediol in aqueous solution.

    PubMed

    Inaba, Satoshi

    2015-06-04

    Methanediol is a product of the hydration of formaldehyde and is more abundant than formaldehyde in aqueous solution. We carried out a number of quantum chemical simulations to study the decomposition of methanediol in aqueous solution. The decomposition of a methanediol proceeds by transferring a proton from a hydroxyl to an oxygen atom of the other hydroxyl in the methanediol. The decomposition of the methanediol completes after the cleavage of the bond between the formaldehyde and the water molecule. The probability of the proton transfer increases by the quantum mechanical tunneling at the low temperature because the width of the potential barrier for the decomposition becomes similar to the de Broglie wavelength of the proton. We consider the catalytic effect of water molecules in aqueous solution. The structure of the methanediol is not required to change significantly when undergoing decomposition due to the active role of water molecules to transfer a proton. We consider three types of arrangement for water molecules with respect to a methanediol: (1) a ring structure formed by a methanediol and water molecules; (2) a water cluster attracted to a methanediol by hydrogen bonds; and (3) a water cluster and additional water molecules, both of which are attracted to a methanediol by hydrogen bonds. The activation energy for the decomposition is reduced by a water cluster more efficiently than water molecules in a ring structure. However, the activation energy reduced by a water cluster is still larger than that obtained from laboratory experiments. We include water molecules that are attracted to a methanediol by hydrogen bonds during the water-cluster-catalyzed decomposition of a methanediol. The hydrogen bonds with the water molecules permit little change in the structure of the methanediol during the decomposition and play a significant role to reduce the activation energy for the decomposition. The rate constant obtained from the theoretical simulation

  10. Adsorption of phosphate from aqueous solution by hydrous zirconium oxide.

    PubMed

    Rodrigues, Liana Alvares; Maschio, Leandro José; Coppio, Luciana de Simone Cividanes; Thim, Gilmar Patrocínio; da Silva, Maria Lúcia Caetano Pinto

    2012-06-01

    Synthetic ZrO2 x nH2O was used for phosphate removal from aqueous solution. The optimum adsorbent dose obtained for phosphate adsorption on to hydrous zirconium oxide was 0.1 g. The kinetic process was described very well by a pseudo-second-order rate model. The phosphate adsorption tended to increase with the decrease in pH. The adsorption capacity increased from 61 to 66 mg g(-1) when the temperature was increased from 298 to 338 K. A phosphate desorption of approximately 74% was obtained using water at pH 12.

  11. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Saita, Takao

    1980-12-01

    It is shown using a capillary viscometer that the viscosity of a dilute aqueous solution of sodium-polyacrylate at 20°C decreases gradually for each flow time measurement and also decreases with the time of rest. Assuming that the polymer degradation is caused by shearing stress and oxidation, their effects are discussed with the data obtained using a closed-type capillary viscometer derived for this investigation. It is proved from the results that rupture of the Na-PAA molecule is caused by mechanochemical degradation, and also photo-degradation under the usual illumination and sunlight in a laboratory.

  12. Removal of synthetic food dyes in aqueous solution by Octolig.

    PubMed

    Martin, Dean F; Alessio, Rachael J; McCane, Cheryl H

    2013-01-01

    We studied six of the seven food dyes commonly used, e.g., FD&C Blue No. 1 and No. 2, Green No. 3, Red No. 3 and No. 40, Yellow No. 5 and No. 6. Quantitative removal was achieved by passage of dyes in aqueous solutions over chromatography columns packed with Octolig, a polyethylenediimine covalently attached to high-surface-area silica. A structural feature most of the dyes have in common are the presence of sulfonate groups attached to aromatic molecules. Prior studies and the current one indicated that the seventh food dye (Green No. 3) should also be quantitatively removed. Matrix effects were considered, but none were observed.

  13. Photochemical dehydrogenation of ethanol in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Handman, J.; Harriman, A.; Porter, G.

    1984-02-01

    The cyclic photodissociation of water has not yet been achieved in a homogeneous solution using visible light. The replacement of the sacrificial electron donor with such waste materials as sulfide is suggested as a method for improving homogeneous systems. Attention is given to the efficient photogeneration of H2 by means of a system that employs a low grade fermentation product, aqueous ethanol, as electron donor. The photoproduction of H2 is coupled to the oxidation of the ethanol by means of NADH/alcohol dehydrogenase as a relay.

  14. Fluorescence of aqueous solutions of commercial humic products

    NASA Astrophysics Data System (ADS)

    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.

  15. Adsorption of phosphate from aqueous solution using activated red mud

    SciTech Connect

    Pradhan, J.; Das, J.; Das, S.; Thakur, R.S.

    1998-08-01

    Adsorption of phosphate (PO{sub 4}{sup 3{minus}}) from aqueous solution on activated red mud (ARM) was studied as a function of time, pH, temperature, concentration of adsorbent and adsorbate in acetic acid-sodium acetate buffer medium. The adsorption of phosphate follows Langmuir as well as Freundlich adsorption isotherms. The process efficiency was found to be 80--90% at room temperature. This can be extended to the treatment of industrial effluents containing phosphates like that from phosphatic fertilizer plants.

  16. Polymerization of beta-amino acids in aqueous solution

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

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

    SciTech Connect

    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

  18. Formation of glycolaldehyde phosphate from glycolaldehyde in aqueous solution

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R.; Arrhenius, G.; Eschenmoser, A.; Bada, J. L. (Principal Investigator)

    1999-01-01

    Amidotriphosphate (0.1 M) in aqueous solution at near neutral pH in the presence of magnesium ions (0.25 M) converts glycolaldehyde (0.025 M) within days at room temperature into glycolaldehyde phosphate in (analytically) nearly quantitative yields (76% in isolated product). This robust phosphorylation process was observed to proceed at concentrations as low as 30 microM glycolaldehyde and 60 microM phosphorylation reagent under otherwise identical conditions. In sharp contrast, attempts to achieve a phosphorylation of glycolaldehyde with cyclotriphosphate ('trimetaphosphate') as phosphorylating reagent were unsuccessful. Mechanistically, the phosphorylation of glycolaldehyde with amidotriphosphate is an example of intramolecular delivery of the phosphate group.

  19. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV-vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved.

  20. Hydrate-based heavy metal separation from aqueous solution

    NASA Astrophysics Data System (ADS)

    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.

  1. Polymerization of beta-amino acids in aqueous solution

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

  2. Highly Efficient Transition Metal Nanoparticle Catalysts in Aqueous Solutions.

    PubMed

    Wang, Changlong; Ciganda, Roberto; Salmon, Lionel; Gregurec, Danijela; Irigoyen, Joseba; Moya, Sergio; Ruiz, Jaime; Astruc, Didier

    2016-02-24

    A ligand design is proposed for transition metal nanoparticle (TMNP) catalysts in aqueous solution. Thus, a tris(triazolyl)-polyethylene glycol (tris-trz-PEG) amphiphilic ligand, 2, is used for the synthesis of very small TMNPs with Fe, Co, Ni, Cu, Ru, Pd, Ag, Pt, and Au. These TMNP-2 catalysts were evaluated and compared for the model 4-nitrophenol reduction, and proved to be extremely efficient. High catalytic efficiencies involving the use of only a few ppm metal of PdNPs, RuNPs, and CuNPs were also exemplified in Suzuki-Miyaura, transfer hydrogenation, and click reactions, respectively.

  3. λ-Radiolysis of aqueous solution of glucosides

    NASA Astrophysics Data System (ADS)

    Rongyao, Yuan; Jilan, Wu

    In this paper, three types of aqueous solution of glucoside, baicalin (I), 1, 8-dihydroxyanthraquinone-β-D-glucoside (II) and glycyrrhizin (III), have been investigated. The yields of decomposition of glucosides are determined. Their G values decrease as doses increase. Some radiolysis products are identified. The influences of different radical scavengers such as, O 2, N 2O, KCNS and isopropanol, are observed. Radiolysis is mainly caused by OH radical. Radiation induced hydrolysis of glucosidic linkage is not the main process, the proportions of dissociated aglycon to total radiolysis products are less than 10%.

  4. Gas solubilities in aqueous solutions of organic substances

    SciTech Connect

    Rischbieter, E.; Schumpe, A.; Wunder, V.

    1996-07-01

    The solubilities of He, N{sub 2}, O{sub 2}, CH{sub 4}, and CO{sub 2} in aqueous solutions of glycerol, acetic acid, glucose, sucrose, and lactose were measured at 303.2 K. Additional data were generated for CO{sub 2} at 293.2 K and 323.2 K. The present results and literature data were analyzed to develop an empirical model. The parameter set allows predictions for 15 gases and 63 organic substances at temperatures between 273 K and 343 K.

  5. Formation of glycolaldehyde phosphate from glycolaldehyde in aqueous solution

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R.; Arrhenius, G.; Eschenmoser, A.; Bada, J. L. (Principal Investigator)

    1999-01-01

    Amidotriphosphate (0.1 M) in aqueous solution at near neutral pH in the presence of magnesium ions (0.25 M) converts glycolaldehyde (0.025 M) within days at room temperature into glycolaldehyde phosphate in (analytically) nearly quantitative yields (76% in isolated product). This robust phosphorylation process was observed to proceed at concentrations as low as 30 microM glycolaldehyde and 60 microM phosphorylation reagent under otherwise identical conditions. In sharp contrast, attempts to achieve a phosphorylation of glycolaldehyde with cyclotriphosphate ('trimetaphosphate') as phosphorylating reagent were unsuccessful. Mechanistically, the phosphorylation of glycolaldehyde with amidotriphosphate is an example of intramolecular delivery of the phosphate group.

  6. Structural aspects of magnetic fluid stabilization in aqueous agarose solutions

    NASA Astrophysics Data System (ADS)

    Nagornyi, A. V.; Petrenko, V. I.; Avdeev, M. V.; Yelenich, O. V.; Solopan, S. O.; Belous, A. G.; Gruzinov, A. Yu.; Ivankov, O. I.; Bulavin, L. A.

    2017-06-01

    Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM).

  7. Primary nucleation of sodium perborate in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Chianese, A.; Contaldi, A.; Mazzarotta, B.

    1986-11-01

    The nucleation kinetics of sodium perborate in aqueous solutions, have been studied at different contents of sodium metaborate. Measurements of metastable zone width and induction periods, carried out under controlled conditions of temperature, supersaturation, and stirring rate, show the great influence of sodium metaborate content over both the sodium perborate solubility and its nucleation kinetics. Furthermore, from the experimental results, nucleation rate relationships and interfacial tension values for the examined systems have been determined. An interesting result of the study has been the good agreement obtained between the interfacial tension values derived from two different sets of experimental data regarding the metastable zone width and the induction period respectively.

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

    PubMed

    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. Removal of pesticides from aqueous solutions using liquid membrane emulsions

    SciTech Connect

    Norwood, V.M. III

    1991-12-31

    Extractive liquid membrane technology is based on a water-in-oil emulsion as the vehicle to effect separation. An aqueous internal reagent phase is emulsified into an organic phase containing a surfactant and optional complexing agents. The emulsion, presenting a large membrane surface area, is then dispersed in an aqueous continuous phase containing the species to be removed. The desired species is transferred from the continuous, phase through the organic liquid membrane and concentrated in the internal reagent phase. Extraction and stripping occur simultaneously rather than sequentially as in conventional solvent extraction. Experiments were conducted to assess the feasibility of using liquid membranes to extract pesticides from rinsewaters typical of those generated by fertilizer/agrichemical dealers. A liquid membrane emulsion containing 10% NaOH as the internal reagent phase was used to extract herbicides from aqueous solution at a continuous phase:emulsion ratio of 5:1. Removals of 2,4-D, MCPA, Carbaryl, Diazinon, and Atrazine were investigated.

  10. Removal of pesticides from aqueous solutions using liquid membrane emulsions

    SciTech Connect

    Norwood, V.M. III.

    1991-01-01

    Extractive liquid membrane technology is based on a water-in-oil emulsion as the vehicle to effect separation. An aqueous internal reagent phase is emulsified into an organic phase containing a surfactant and optional complexing agents. The emulsion, presenting a large membrane surface area, is then dispersed in an aqueous continuous phase containing the species to be removed. The desired species is transferred from the continuous, phase through the organic liquid membrane and concentrated in the internal reagent phase. Extraction and stripping occur simultaneously rather than sequentially as in conventional solvent extraction. Experiments were conducted to assess the feasibility of using liquid membranes to extract pesticides from rinsewaters typical of those generated by fertilizer/agrichemical dealers. A liquid membrane emulsion containing 10% NaOH as the internal reagent phase was used to extract herbicides from aqueous solution at a continuous phase:emulsion ratio of 5:1. Removals of 2,4-D, MCPA, Carbaryl, Diazinon, and Atrazine were investigated.

  11. Stability studies on aqueous and oily ophthalmic solutions of diclofenac.

    PubMed

    Ahuja, Munish; Dhake, Avinash Shridhar; Sharma, Surendra Kumar; Majumdar, Dipak Kanti

    2009-04-01

    Various aqueous and oily diclofenac ophthalmic formulations were subjected to accelerated and long term stability studies. Degradation of diclofenac was found to follow first-order kinetics. Among the aqueous formulations containing preservative, formulation with PMA, PMN, SA, MP/PP and SMS showed diclofenac content above 90% after 6 months of accelerated and 12 months of room temperature storage. Diclofenac 0.1%, w/v aqueous formulation (pH 7.4), with 5-10% overages, containing SMS, MP/PP or PMN look promising taking both stability and corneal permeability in view. However, for use in cataract surgery formulation without preservative appears ideal. Oily ophthalmic formulations except those in olive and mustard oil, had more than 90% drug content after 6 months of accelerated and 12 months of room temperature storage. Diclofenac (0.2%, w/v) ophthalmic solution in sesame oil with 3% overage and containing benzyl alcohol (0.5%, v/v) as preservative, appears ideal, taking both stability and corneal permeability in view.

  12. Excess Thermodynamic Properties of Concentrated Aqueous Solutions at High Temperatures

    SciTech Connect

    Guszkiewicz, M.S.

    2001-06-07

    Measurements of the vapor pressure of the solvent in wide ranges of concentration and temperature provide information on solute solvation and ion pairing--the two phenomena most often invoked for description of dilute solutions. Even in moderately concentrated solutions, as interionic distances become comparable to ionic diameters, these simple concepts gradually lose their meaning and solutions behave like molten salts. The usefulness of experimental vapor pressure results increases rapidly with their accuracy, since derived properties, such as solution enthalpies and heat capacities, can be calculated. Very accurate results can be obtained by the isopiestic method, but primary vapor pressure data for standard solutions are needed. In order to obtain vapor pressures at conditions where accurate isopiestic standards are not available and to establish more accurate standards, the ORNL isopiestic apparatus was modified for simultaneous direct vapor pressure measurements and isopiestic comparisons. There are no comprehensive solution theories derived from molecular level models and able to predict thermodynamic properties of various electrolytes as the composition changes from dilute solutions to molten salts in a wide range of temperatures. Empirical and semi-empirical models are useful for representation of experimental results, interpretation of measurements of other properties such as conductance., solubility or liquid-vapor partitioning of solutes, and for verification of theoretical predictions. Vapor pressures for aqueous CaCl{sub 2}, CaBr{sub 2}, LiCl, LiBr, LiI, NaI were measured at temperatures between 380 and 523 K in the concentration range extended to water activities below 0.2 (over 30 mol/kg for LiCl). General equations based on the modified Pitzer ion-interaction model were used to obtain enthalpy and heat capacity surfaces, which are compared with direct calorimetric measurements.

  13. Supercritical fluid precipitation of recombinant human immunoglobulin from aqueous solutions.

    PubMed

    Nesta, D P; Elliott, J S; Warr, J P

    2000-02-20

    Supercritical carbon dioxide was used as an antisolvent for producing recombinant human immunoglobulin G (rIgG) particulate powders. Liquid carbon dioxide (CO(2)) was premixed with ethanol to create a single-phase, modified supercritical fluid (SCF). The modified SCF was then vigorously mixed with a pharmaceutically acceptable, aqueous formulation of rIgG, and the mixture was immediately atomized into a pressurized vessel where rapid expansion of the modified SCF extracted the aqueous phase, resulting in precipitation of the protein powder. The process was reproducible, and resulting powder products were characterized by their aqueous solubilities, and the spectroscopic profile, molecular integrity, and antigen binding activity of the individual soluble fractions. Molecular integrity was assessed via size-exclusion high-performance liquid chromatography (SEC), whereas antigen binding activity was determined using an enzyme-linked immunosorbent assay (ELISA). Attempts to characterize particle size and morphology were confounded due to the extremely deliquescent nature of the powders, causing them to absorb moisture rapidly and become gummy. Operational conditions were optimized to a point which yielded powders that were completely soluble, and had ultraviolet (UV) spectroscopic and SEC profiles indistinguishable from those of the reference standard starting solution from which the powders were derived. Antigen binding activities of the powders, however, were

  14. Electrochemistry in Near-Critical and Supercritical Fluids. 3. Studies of Br(-), I(-), and Hydroquinone in Aqueous Solutions.

    DTIC Science & Technology

    1986-02-01

    extraction of coal , 5 tar sands, 6 and biomass. 7 Complete oxidation cf most organic pollutants has also been achieved in a mixture of supercritical water...80-8169 136 ELECTROCHEMISTRY IN MERM-CRI TICAL AMD SUPERCRITICAL In1 FLUIDS I STUDIES OF 9.. (U) TEXAS UNIV AT AUSTIN DEPT OF CHENISTRY N M FLARSHEIM... Supercritical Fluids. 3. Studies of B and Hydroquinone in Aqueous Solutions By William M. Flarsheim*, Yu-Min Tsou*, Isacc Trachtenberg*, Keith P. Johnson

  15. Degradation of aqueous DEA solutions in heat transfer tubes

    SciTech Connect

    Meisen, A.; Chakma, A.

    1985-01-01

    Experiments were performed on the degradation of aqueous diethanolamine (DEA) solutions passing through a coiled heat transfer tube (2.0032 mm ID, 3.175 mm OD, 4.8 m long) immersed in a constant temperature bath. The operating conditions were: DEA flow rate 0.011 to 0.0172 L/s, DEA concentration 20 to 40 wt%, DEA temperature 60 to 200/sup 0/C, CO/sub 2/ partial pressure 1.38 to 4.18 MPa. The degradation rate was found to increase with temperature, DEA concentration and CO/sub 2/ partial pressure; it decreased with solution flow rate. The degradation was accompanied by the formation of a fouling deposit. A simple mathematical model is presented for predicting DEA degradation.

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

    PubMed

    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.

  17. Photoelectron Spectra of Aqueous Solutions from First Principles

    SciTech Connect

    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.

  18. Products of radiation removal of lead from aqueous solutions.

    PubMed

    Drtinova, B; Pospisil, M; Cuba, V

    2010-01-01

    The influence of typical *OH radical scavengers as potassium formate and isopropanol on the radiation-induced removal of lead was individually studied. The lead can be completely removed from aqueous solutions containing 1x10(-2) mol/L of formate already at the dose of 2.5 kGy. With increasing concentration of formate (5x10(-5)-1x10(-2) mol/L) increases the amount of Pb(formate)(+) species in the solution before irradiation. The radiation product is metallic lead at low concentration of formate to PbCO(3) at higher concentration of scavenger. In the system with 10% isopropanol dominates the species Pb(2+) and the product of radiation reduction is then metallic lead. Copyright 2009 Elsevier Ltd. All rights reserved.

  19. Anomalies in, and crystallization of supercooled water and aqueous solutions

    NASA Astrophysics Data System (ADS)

    Angell, C. A.

    1984-03-01

    This report summarizes research work performed under ONR auspices during the period 1978-1983. Thermodynamic studies of pure water and various aqueous solutions containing simple molecular second components such as H2O2N2H4 and formamide have been performed at temperatures down to -120 C, in order to perform extrapolations to obtain properties of normal water, i.e. water free from anomalous structure fluctuations. Properties studied have been heat capacity, expansivity and compressibility. On certain of these solutions, viscosity and also dielectric relaxation studies have been performed. Spectroscopic measurements in both the far infrared, and the near infrared, have yielded information on vibrational modes and characteristic hydrogen bonding structures. All together these measurements have done much to elucidate the anomalous behavior of water in the supercooled regime.

  20. Adsorption of citric acid from dilute aqueous solutions by hydroxyapatite.

    PubMed

    Vega, Enrique D; Narda, Griselda E; Ferretti, Ferdinando H

    2003-12-01

    The role of citric acid in the demineralization of dental enamel, which is mainly constituted by hydroxyapatite, is important for periodontal regeneration and in the conditioning of enamel or dentin for bonding restorative resins. The adsorption of citric acid from aqueous solutions onto synthetic hydroxyapatite at 278, 288, 298, and 308 K and pH 4.8 has been studied by means of UV spectroscopy. The adsorption reaction, which takes place by an interaction between phosphate groups and citrate anions at the solid-solution interface, yields an adsorbate-adsorbent complex of high stability. The adsorption isotherms fit the Langmuirian shape. The proposed adsorption model, where citrate species interact in a bidentate manner (one citrate ion links two phosphate sites), is coherent with the experimental data. The activation standard heat and activation standard entropy were calculated. All the thermodynamic and kinetic parameters were in concordance with the adsorption reaction proposed in this work.

  1. Colloidal interactions between asphaltene surfaces in aqueous solutions.

    PubMed

    Liu, Jianjun; Zhang, Liyan; Xu, Zhenghe; Masliyah, Jacob

    2006-02-14

    Asphaltene at oil/water interfaces plays a dominant role in the recovery of crude oil. In this study, asphaltene monolayer films were deposited on hydrophobic silicon wafers and silica spheres from oil-water interfaces using a Langmuir interfacial trough. The morphology of the deposited asphaltene films was characterized with an atomic force microscope (AFM). The colloidal forces between the prepared asphaltene films in aqueous solutions were measured with AFM to shed light on the stabilization of water or oil droplets coated with asphaltene films. Factors such as solution pH, KCl concentration, calcium addition, and temperature all showed a strong impact on colloidal forces between the prepared asphaltene films. The findings provided a better understanding of asphaltene interfacial films at an oil/water interface in stabilizing bitumen-in-water and water-in-bitumen emulsions.

  2. Aggregation and micelle formation of ionic liquids in aqueous solution

    NASA Astrophysics Data System (ADS)

    Miskolczy, Zsombor; Sebők-Nagy, Krisztina; Biczók, László; Göktürk, Sinem

    2004-12-01

    Association of ionic liquids possessing n-octyl moiety either in the cation or in the anion has been studied in aqueous solution with conductivity and turbidity measurements as well as using 2-hydroxy-substituted Nile Red solvatochromic probe. 1-Butyl-3-methylimidazolium octyl sulfate was found to act as a surfactant above 0.031 M critical micelle concentration. In contrast, 1-methyl-3-octylimidazolium chloride produced inhomogeneous solution of larger aggregates, which were dissolved on the addition of more than 2:1 molar excess of sodium dodecyl sulfate (SDS) due to mixed micelle formation. Even small amount (<10 mM) of ionic liquids could markedly reduce the polarity of the Stern layer of SDS micelle.

  3. Adsorption of thorium from aqueous solutions by perlite.

    PubMed

    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.

  4. [Conformation of trypsin molecules in aqueous solutions containing 2-chloroethanol].

    PubMed

    Kushner, V P

    1980-01-01

    Changes in the macromolecular parameters of trypsin in the presence of 2-chloroethanol in aqueous solutions have been studied by means of optical and hydrodynamic methods. At temperature--dependent volume fraction of 2-chloroethanol in solution upsilon t < 0.30 the globular structure of trypsin is destroyed but the regularity of polypeptide chains within the limits of secondary structure is maintained. At 0.30 < upsilon < 0.80 the solvation envelope of macromolecules is kept constant mainly owing to hydration, but the solubilization takes place only at upsilon < 0.30. At upsilon < 0.80 spiralization sharply increases and reaches in pure 2-chloroethanol its maximum value (50%). The intrinsic viscosity moreover reaches only half the whole value [eta]coil--[eta]glob.

  5. Mg isotope fractionation between inorganic aragonite and aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Zhang, S.; Hu, P.

    2012-12-01

    Recent studies showed δ26Mg values of some species of Scleractinian corals, and aragonitic sponges and Scaphopod are inconsistent with the Mg isotope fractionation calibrated previously between inorganic aragonite and seawater. In this study, we explored Mg isotope fractionation between aragonite and aqueous solution under various experimental conditions, including salinity (mostly in fresh water), Mg/Ca ratio (3-5 in molar), Ca concentration (400-1500 ppm), temperature (25-55oC) and duration of experiments (3-21 days). Precipitation experiments were conducted using 'free-drift' method. The starting solution was made by mixing an appropriate amount of reagent-grade NaHCO3, CaCl2 and MgCl2 in deionized water, flushed with CO2 gas. The mixed solution was filtered after these reagents completely dissolved before any experiment, and then passively-degassed in a water bath kept at a constant temperature. Over the course of the experiments, pH and alkalinity of the aqueous solution were closely monitored. At the end of the experiment, the precipitates were cleaned, characterized by SEM and checked by XRD. The solution and precipitates were treated by acid. The supernatant was passed through two chromatographic columns to extract pure Mg, and measured for their δ26Mg values. In each case, a leaching procedure is employed to clean aragonite before their isotopic compositions were measured. Our preliminary results show that the Mg isotope fractionation between aragonite and solution varies with Ca concentration at a given Mg/Ca ratio, i.e., aragonite are strongly depleted in 26Mg in solution with high and low Ca concentration (e.g., Ca = 400ppm and 2000 ppm), but less depleted in solutions with intermediate Ca concentration (e.g., Ca= 1000 ppm). At a given Ca and Mg/Ca, the fractionation factor is temperature-dependent, defining linear relationship with 1/T (T is temperature in Kelvin) with temperature sensitivity of ~ 0.01‰/oC. These results seem to suggest a kinetic

  6. Nitrate Concentration near the Surface of Frozen Aqueous Solutions.

    PubMed

    Marrocco, Harley A; Michelsen, Rebecca R H

    2014-12-26

    Photolysis of nitrate plays an important role in the emission of nitrogen oxides from snow and ice, which affects the composition of the overlying atmosphere. In order to quantify these reactions, it is necessary to know how much nitrate is available for photolysis near the surfaces of snow and ice. The concentration of nitrate excluded from frozen solutions of nitric acid, sodium nitrate, and magnesium nitrate was measured with attenuated total reflection infrared spectroscopy. Liquid water and nitrate were observed at and near the bottom surface of frozen aqueous solutions during annealing from -18 to -2 °C. At -2 °C, the nitrate concentration was determined to be ∼1.0 mol/L for frozen NaNO(3) and Mg(NO(3))(2) solutions and ∼0.8 mol/L for frozen HNO(3) solutions. At lower temperatures, nitrate concentration ranged from 1.6 to 3.7 mol/L. Ideal thermodynamics overestimates nitrate concentration at colder temperatures where the brine is highly concentrated for all solutions. The nitrate concentration at ice surfaces is well described by bulk freezing point depression data close to the melting point of ice and for nitric acid at colder temperatures. Effects of temperature and counterions and implications for modeling snow chemistry are discussed.

  7. Reversible absorption of SO2 by amino acid aqueous solutions.

    PubMed

    Deng, Renpan; Jia, Lishan; Song, Qianqian; Su, Shuai; Tian, Zhongbiao

    2012-08-30

    Six water-soluble amino acids (glycine, l-α-alanine, dl-alanine, β-alanine, proline and arginine) aqueous solutions were applied to remove SO(2) from SO(2)-N(2) system in this report. All the tested amino acids solutions were found to be excellent absorbents for SO(2) removal, and SO(2) saturation uptake of β-alanine solution was the highest under the same experimental conditions. The effects of amino acid concentration, SO(2) concentration, absorption temperature, desorption temperature and initial pH value of the absorbent on the removal of SO(2) were investigated with β-Ala solution. The experimental results showed that SO(2) saturation uptake increased with the increase in β-alanine solution and SO(2) concentration. Room temperature (20-30°C) was found to be optimal for SO(2) absorption. Additionally the SO(2) desorption capacity increased with increasing desorption temperature. The neutral environment pH value of 6.8 was found to be optimal for SO(2) removal. Ten continuous absorption-desorption cycles showed that the absorbent had an excellent regeneration performance. (13)C NMR and ultraviolet analyses offer ample evidence to speculate that the bonding between SO(2) and β-alanine was not covalent but some weak interactive forces, such as dispersion force, induction force, dipole-dipole force and hydrogen bond. Copyright © 2012 Elsevier B.V. All rights reserved.

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

    PubMed

    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. Copyright 2005 Wiley Periodicals, Inc

  9. Short-range interactions of concentrated proline in aqueous solution.

    PubMed

    Busch, Sebastian; Lorenz, Christian D; Taylor, Jonathan; Pardo, Luis Carlos; McLain, Sylvia E

    2014-12-11

    Molecular interactions for proline in a highly concentrated aqueous solution (up to 1:5 proline:water molecular ratio) have been investigated using a variety of experimental and computational techniques. Rather than the solution containing either small crystallites or large aggregates of proline, three-dimensional structural analysis reveals the presence of proline-proline dimers. These dimers appear to be formed by cyclic electrostatic interactions between CO2(-) and NH2(+) groups on neighboring proline molecules, which causes the ring motifs of proline to be roughly parallel to one another. In addition, water appears to aggregate around the electrostatic groups of the proline-proline dimers where it may in fact bridge these groups on different molecules. The observed short-range interactions for proline in solution may explain its function as a hydrotrope in vivo in which this observed dimerization might allow proline molecules to generate small pockets of a hydrophobic environment that can associate with nonpolar motifs of other molecules in solution. The results presented here emphasize the need for careful three-dimensional analysis to assess the short-range order of highly concentrated solutions.

  10. Removal of phthalate esters from aqueous solutions by chitosan bead.

    PubMed

    Chen, Chih-Yu; Chung, Ying-Chien

    2006-01-01

    Removal of phthalate esters (PAEs) by chitosan bead in aqueous solution was studied. The adsorption isotherms of PAEs by chitosan bead were well described by Freundlich isotherm equations. Results of kinetic experiments indicated that diheptyl phthalate (DHpP) had the highest adsorption capacity (1.52 mg/g) among six PAEs in our research. PAE adsorption efficiency by chitosan bead was examined in both batch and continuous systems, and DHpP attained 74.9% recovery efficiency from chitosan bead by shaking with an equal volume mixture of methanol and water. The recovered chitosan bead was reusable as an adsorbent. The influences of temperature, pH, Ca+2, and NaCl on PAE adsorption were also evaluated to determine performance in different water environments (e.g., groundwater, surface water, and sea water). The results showed that PAE adsorption decreased as temperature increased. From pH experiments it appeared that pH 8.0 was optimal for adsorption. The effect of Ca+2 showed that adsorption efficiency did not change by increasing the concentrations of Ca+2 until 400 mg/L. NaCl coexistence showed an insignificant effect on PAE adsorption. Furthermore, the chitosan bead was also applied to treating the discharge of a plastics plant, and the treatment results resembled those of a laboratory continuous system. This is the first report to use chitosan bead as an adsorbent to adsorb phthalate esters from aqueous solution. These results indicate that the application of chitosan bead is feasible in the aqueous environments of Taiwan.

  11. Preparation of metallic nanoparticles by irradiation in starch aqueous solution

    SciTech Connect

    Nemţanu, Monica R. Braşoveanu, Mirela Iacob, Nicuşor

    2014-11-24

    Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔE{sub ab} (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle h{sup o} was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

  12. Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    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.

  13. Adsorption of dyes on carbon nanomaterials from aqueous solutions.

    PubMed

    Rodríguez, A; Ovejero, G; Sotelo, J L; Mestanza, M; García, J

    2010-10-01

    The removal of methylene blue (MB), a cationic dye and orange II (OII), an anionic dye, from aqueous solution by using carbon nanomaterials as multiwalled carbon nanotubes (MWNTs) and carbon nanofibers (CNF) as adsorbents was studied in batch experiments. The effect of pH, temperature and surface modification of adsorbent on the removal of MB and OII was also investigated. The removals of OII and MB by adsorption on MWNT were maximum at pH 3.0 and pH 7.0, respectively. However, in the case CNF was employed as adsorbent, the optimum values of pH were 9.0 and 5.0 for OII and MB, respectively. Langmuir and Freundlich isotherms are applied to fit the adsorption data of both dyes. Equilibrium data were well described by the typical Langmuir adsorption isotherm. Overall, the study demonstrated that MWNTs and CNFs can effectively remove cationic and anionic dyes as MB and OII from aqueous solutions under these experimental conditions.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Removal of Congo Red from aqueous solution by cattail root.

    PubMed

    Hu, Zhenhu; Chen, Hui; Ji, Feng; Yuan, Shoujun

    2010-01-15

    In this study, cattail root was used to remove Congo Red (CR) from aqueous solution. The effects of operation variables, such as cattail root dosage, contact time, initial pH, ionic strength and temperature on the removal of CR were investigated using batch adsorption technique. Removal efficiency increased with increase of cattail root dosage and ionic strength, but decreased with increase of temperature. The equilibrium data fitted well to the Langmuir model (R(2)>0.98) and the adsorption kinetic followed the pseudo-second-order equation (R(2)>0.99). Thermodynamics parameters such as standard free energy change (Delta G degrees), standard enthalpy change (Delta H degrees), and standard entropy change (DeltaS degrees ) were analyzed. The values of Delta G degrees were between -7.871 and -4.702 kJ mol(-1), of Delta H degrees was -54.116 kJ mol(-1), and of DeltaS degrees was -0.157 kJ mol(-1)K(-1), revealing that the removal of CR from aqueous solution by cattail root was a spontaneous and exothermic adsorption process. The maximum adsorption capacities of CR on cattail root were 38.79, 34.59 and 30.61 mg g(-1) at 20, 30 and 40 degrees C, respectively. These results suggest that cattail root is a potential low-cost adsorbent for the dye removal from industrial wastewater.

  16. Efficient removal of mercury from aqueous solutions and industrial effluent.

    PubMed

    Dos Santos, Maria B P; Leal, Katia Z; Oliveira, Fernando J S; Sella, Silvia M; Vieira, Méri D; Marques, Elisa M D; Gomes, Vanessa A C

    2015-01-01

    The objective of this study was to examine the ability of a solid waste produced during beneficiation of ornamental rocks to remove mercury (Hg) from an industrial effluent and aqueous solutions under various conditions. Batch studies have been carried out by observing the effects of pH, concentration of the adsorbate, contact time, and so on. Various sorption isotherm models such as Langmuir, Freundlich, and Tóth have been applied for the adsorbent. Film and intraparticle diffusion were both found to be rate-limiting steps. Adsorption was properly described by the Freundlich model (capacity constant of 0.3090 (mg g(-1))(mg L(-1))(-1/n) and adsorption intensity indicator of 2.2939), which indicated a favorable sorption and encouraged subsequent studies for treatment of Hg-containing industrial effluent. Industrial effluent treatment efficiency reached Hg removals greater than 90% by using ornamental rock solid waste (ORSW). Besides, desorption studies indicated that the maximum recovery of mercury was 100 ± 2% for 1 mol L(-1) HNO3 and 74 ± 8% for 0.1 mol L(-1) HNO3. The ORSW could be reused thrice without significant difference on the Hg removal rate from industrial effluent. These findings place ORSW as a promising efficient and low-cost adsorbent for the removal of Hg from aqueous solutions and industrial effluent.

  17. Electroreduction of carbon dioxide in aqueous solutions at metal electrodes

    SciTech Connect

    Augustynski, J.; Jermann, B.; Kedzierzawski, P.

    1996-12-31

    The quantities of carbon stored in the form of atmospheric carbon dioxide, CO{sub 2} in the hydrosphere and carbonates in the terrestrial environment substantially exceed those of fossil fuels. In spite of this the industrial use of carbon dioxide as a source of chemical carbon is presently limited to preparation of urea and certain carboxylic acids as well as organic carbonates and polycarbonates. However, the situation is expected to change in the future, if effective catalytic systems allowing to activate carbon dioxide will become available. In this connection, the electrochemical reduction of CO{sub 2}, requiring only an additional input of water and electrical energy, appears as an attractive possibility. For more than 100 years formic acid and formates of alkali metals were considered as the only significant products of the electroreduction of carbon dioxide in aqueous solutions. The highest current efficiencies, exceeding 90 %, were obtained either with mercury or with amalgam electrodes. The only comprehensive study regarding kinetics of CO{sub 2} reduction in aqueous solution has been performed by Eyring et al. using a mercury cathode. This paper describes electrolysis studies.

  18. Pulse radiolysis of aqueous solutions of sodium tetraphenylborate

    NASA Astrophysics Data System (ADS)

    Crawford, Charles L.; Gholami, Mohammad R.; Bhave, Ravindra N.; Hanrahan, Robert J.

    1994-09-01

    In previous work on the 60Co γ-radiolysis of aqueous tetraphenylborate (TPB -) solutions carried out in this laboratory, it was found that several organic products, including benzene, phenol and biphenyl, are produced with substantial yield. However, the reaction mechanism was not established. In the present study, reactions initiated by OḢ radicals, N 3 radicals and e -aq in aqueous TPB - solutions were studied by pulse radiolysis using a 600 keV Febetron electron accelerator. The lack of reactivity between TPB - and e -aq was demonstrated by directly monitoring the transient optical absorbance of e -aq. Concerning the reaction with O Ḣ, two schemes were considered: (1) electron transfer from B(C 6H 5) -4 to O Ḣ; or (2) O Ḣ addition to B(C 6H 5) -4. Comparison of observed transient absorption spectra with expectations based on two different schemes suggests that O Ḣ addition is the dominant reaction pathway under conditions of N 2O saturation, with an experimentally determined second-order rate constant of 6.2×10 9M -1s -1. A mechanism based on an initial first-order self-decomposition of the O Ḣ adduct, (C 6H 5) 3BC 6H 5OH -· with a measured rate constant of 4×10 4s -1 is proposed. Kinetic modeling on the proposed mechanistic scheme gives good agreement with our experimental results.

  19. Photochemistry of Tetrabromobisphenol A in Frozen and Liquid Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Reich, J.; Grannas, A. M.; Dolak, E.

    2012-12-01

    Brominated flame retardants are an emerging environmental contaminant and are now globally distributed in the environment, including the Polar Regions. Because bioaccumulation presents serious concerns for human and wildlife health within the Arctic, it is important to assess the potential fate of these contaminants. Despite some established knowledge regarding photochemical processes in reactive frozen media, little published literature exists regarding the chemical transformations and fate of brominated flame retardants in the Arctic. Here, we consider the photochemical transformation of tetrabromobisphenol A (TBBPA). We have conducted field-based experiments in Barrow, Alaska to investigate the potential photochemical degradation of TBBPA in snow/ice samples and found that TBBPA was efficiently photodegraded in frozen aqueous samples under natural Barrow sunlight. The main pathway of degradation was direct photolysis and the addition of photosensitizers had no significant impact on TBBPA photodegradation. In aqueous solution the solubility and light absorption properties of TBBPA are pH dependent, indicating that the photodegradation of TBBPA in the environment will be highly pH dependent. Reactions than are pH dependent may be affected by the nature of the liquid-like layers in snow/ice as well as the presence of other solutes that may indirectly affect the local pH. Here we will discuss our field and laboratory-based results investigating the role that snow/ice composition may play on TBBPA photochemical reactivity.

  20. Preparation of metallic nanoparticles by irradiation in starch aqueous solution

    NASA Astrophysics Data System (ADS)

    NemÅ£anu, Monica R.; Braşoveanu, Mirela; Iacob, Nicuşor

    2014-11-01

    Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔEab (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle ho was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

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

    NASA Astrophysics Data System (ADS)

    George, Deepu K.; Charkhesht, Ali; Vinh, N. Q.

    2015-12-01

    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-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 1012 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.

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

    PubMed

    George, Deepu K; Charkhesht, Ali; Vinh, N Q

    2015-12-01

    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(-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(12) and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with error bars of ±0.02 °C from 0 °C to 90 °C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

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

    SciTech Connect

    George, Deepu K.; Charkhesht, Ali; Vinh, N. Q.

    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.

  4. Gamma radiolytic degradation of naphthalene in aqueous solution

    NASA Astrophysics Data System (ADS)

    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.

  5. Method of precipitating uranium from an aqueous solution and/or sediment

    SciTech Connect

    Tokunaga, Tetsu K; Kim, Yongman; Wan, Jiamin

    2013-08-20

    A method for precipitating uranium from an aqueous solution and/or sediment comprising uranium and/or vanadium is presented. The method includes precipitating uranium as a uranyl vanadate through mixing an aqueous solution and/or sediment comprising uranium and/or vanadium and a solution comprising a monovalent or divalent cation to form the corresponding cation uranyl vanadate precipitate. The method also provides a pathway for extraction of uranium and vanadium from an aqueous solution and/or sediment.

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

    PubMed

    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.

  7. Sorption of hydrophobic organic compounds on natural sorbents and organoclays from aqueous and non-aqueous solutions: a mini-review.

    PubMed

    Moyo, Francis; Tandlich, Roman; Wilhelmi, Brendan S; Balaz, Stefan

    2014-05-09

    Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    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.

  11. Synthesis of magnetic biocomposite for efficient adsorption of azo dye from aqueous solution.

    PubMed

    Sivashankar, R; Sathya, A B; Krishnakumar, Uma; Sivasubramanian, V

    2015-11-01

    A novel magnetic biocomposite was synthesized using metal chlorides and aquatic macrophytes by co-precipitation method. The resulting product, magnetic biocomposite was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and Scanning electron microscope (SEM). The adsorption performance of the magnetic biocomposite was tested with removal of Metanil Yellow dye from aqueous solution. The effect of influencing parameters such as initial dye concentration, solution pH and agitation were investigated. The equilibrium isotherm was well described by the Langmuir model with the with maximum adsorption capacity of 90.91mg/g. Adsorption kinetics experiments were carried out and the data were well fitted by a pseudo-second-order equation. The results revealed that the magnetic biocomposite could efficiently adsorb the azo dyes from aqueous solution, and the spent adsorbents could be recovered completely by magnetic separation process. Therefore, the prepared magnetic biocomposite could thus be used as promising adsorbent for the removal of azo dyes from polluted water.

  12. Kinetics and thermodynamic study of aniline adsorption by multi-walled carbon nanotubes from aqueous solution.

    PubMed

    Al-Johani, Hind; Abdel Salam, Mohamed

    2011-08-15

    Multi-walled carbon nanotubes (MWCNTs) were used in the adsorptive removal of aniline, an organic pollutant, from an aqueous solution. It was found that carbon nanotubes with a higher specific surface area adsorbed and removed more aniline from an aqueous solution. The adsorption was dependent on factors, such as MWCNTs dosage, contact time, aniline concentration, solution pH and temperature. The adsorption study was analyzed kinetically, and the results revealed that the adsorption followed pseudo-second order kinetics with good correlation coefficients. In addition, it was found that the adsorption of aniline occurred in two consecutive steps, including the slow intra-particle diffusion of aniline molecules through the nanotubes. Various thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), were calculated. The results indicated that the spontaneity of the adsorption, exothermic nature of the adsorption and the decrease in the randomness reported as ΔG°, ΔH° and ΔS°, respectively, were all negative.

  13. A new sand adsorbent for the removal and reuse of nickel ions from aqueous solutions.

    PubMed

    Tao, Wenhong; Qi, Ling; Duan, Huimin; Liu, Shiquan

    2017-04-01

    Nickel ions (Ni(II)) in aqueous solutions were removed by a sand adsorbent with a surface functionalized porous coating. The sand adsorbent has a very large surface area of 150 m(2)/g. The influence of pH, initial concentration of the solution, temperature, contact time and adsorbent dosage on the removal efficiency of the synthesized sand adsorbent toward Ni(II) in the aqueous solutions were studied. The results indicate that the adsorption of nickel onto the sand adsorbent greatly increases the pH range of 2-4 and slightly increases with temperature from 25 to 40 °C. The maximum removal efficiency and ion retention in per unit mass of the adsorbent were 100% and 5.78 mg/g, respectively, under the specified experimental conditions. The adsorption can be described by the pseudo-second-order kinetic model and the Freundlich adsorption model. The adsorbed nickel (4.24 mg/g) together with the spent adsorbent were successfully employed to prepare a brown glass, suggesting a new way to reutilize the recovered nickel from wastewater and to avoid secondary pollution caused by the used adsorbents.

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

    PubMed

    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.

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

    PubMed

    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.

  16. Neptunium interaction with uranium dioxide in aqueous solution

    NASA Astrophysics Data System (ADS)

    Batuk, O. N.; Kalmykov, St. N.; Petrov, V. G.; Zakharova, E. V.; Teterin, Yu. A.; Teterin, A. Yu.; Shapovalov, V. I.; Haire, M. J.

    2007-05-01

    Neptunium, Np(V) and Np(IV), sorption onto uranium dioxide surface was studied at various values of pH. Sorption was studied in two sets of experiments with different redox conditions that correspond to either Np(V) (Set 1) or Np(IV) (Set 2) in solution. In Set 1 the reduction of Np(V) was established when low pH solution covered a UO2 surface. When the pH increased, the sorption of neptunium is decreased. At pH > 5.5 neptunium sequestration from solution is governed by Np(V) sorption onto UO2.25. In Set 2 (the more anoxic conditions) complete neptunium sorption is established at pH > 2: it is present in the tetravalent form over the whole pH range. The proposed mechanisms of neptunium sorption was suggested by using pH sorption edges of Th(IV) as an analog to Np(IV) onto UO2 and Np(V) onto ThO2. The UO2 surface was characterized by X-ray photoelectron spectroscopy (XPS) after equilibration with aqueous solutions at different pH values.

  17. Polymerization of Pu(IV) in aqueous nitric acid solutions

    SciTech Connect

    Toth, L.M.; Friedman, H.A.; Osborne, M.M.

    1980-10-01

    The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO{sub 2}(NO{sub 3}){sub 2} concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50{sup 0}C and with 0.05 M Pu in nitric acid solutions that vary in acidity from 0.07 to 0.4 M. An induction period usually precedes the polymer growth stage during which time nucleation of primary hydrolysis products occurs. Uranyl nitrate retards the polymerization reaction by approximately 35% in spite of the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation, expressed as d(percent polymer)/dt, has been shown to depend on the total plutonium concentration in reactions where the Pu(IV) concentration remained constant; and it is therefore suggested that the polymer reaction rate is not first order with respect to the concentration of plutonium as was previously thought. It has been shown further that accurate acid determinations on stock reagents are essential in order to obtain reliable polymerization experiments. Satisfactory procedures for these analyses did not exist, so appropriate modifications to the iodate precipitation methods were developed. The most ideal plutonium reagent material has been shown to be crystalline Pu(IV) nitrate because it can be added directly to acid solutions without the occurrence of unintentional hydrolysis reactions.

  18. Peculiarities of state diagrams of aqueous solutions of cryoprotective agents.

    PubMed

    Osetsky, Alexander I

    2009-10-01

    The phase transitions in aqueous solutions of glycerol and PEO-1500 within the temperature range of +30 to -150 degrees C have been studied using the methods of thermoplastic analysis and volumetric scanning tensodilatometry. We present the revealed phenomenon of cluster cyrystallization of these solutions as well as principles of describing this phenomenon using state diagrams, containing the intervals of concentration corresponding to the existence of amorphous and cryocolloid fractions. We note that for the cryocolloid fraction, a low temperature association of molecules of cryoprotective agents leads the formation of ice nanocrystals either close to or directly inside the aggregations. These fractions exist in cooled cryoprotective solutions near the vitrification temperatures of the liquid phase and may contribute to the initiation of damaging events in cryopreserved biological systems. Our data may be helpful in explaining the peculiarities observed during crystallization of cryoprotective solutions and may further contribute to a broader understanding of the principles of protection and protocol optimization of biological materials at temperatures approaching vitrification.

  19. Crystallization in solid solution-aqueous solution systems: Thermodynamic and kinetic approaches

    SciTech Connect

    Shtukenberg, A. G. Punin, Yu. O.; Azimov, P. Ya.

    2010-03-15

    A new phenomenological approach is proposed to describe the crystallization kinetics in solid solution-aqueous solution binary systems. The phase diagrams, equilibria, and quasie-quilibria are considered within this approach. The crystallization kinetics near the true equilibrium and the crystallization features at large deviations from equilibrium are discussed on this basis. Special attention is paid to possible interactions in a solution with a seed crystal placed in it. In particular, the interactions leading to the seed's crystal growth or dissolution and to a possible exchange or metasomatic reactions are considered. In addition, the effect of the generated mismatch stress on the crystal growth rate and composition is analyzed.

  20. Aromatic oligomers that form hetero duplexes in aqueous solution.

    PubMed

    Gabriel, Gregory J; Iverson, Brent L

    2002-12-25

    The electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (Ndi) and electron-rich 1,5-dialkoxynaphthalene (Dan) have been shown to complex strongly with each other in water due to the hydrophobic effect as modulated through the electrostatic complementarity of the stacked dimer. Previously, oligomers of alternating Ndi and Dan units, termed aedamers, were the first foldamers to employ intramolecular aromatic stacking to effect the formation of secondary structure of nonnatural chains in aqueous solution. Described here is the use of this aromatic-aromatic (or pi-pi) interaction, this time in an intermolecular format, to demonstrate the self-assembly of stable hetero duplexes from a set of molecular strands (1a-4a) and (1b-4b) incorporating Ndi and Dan units, respectively. A 1-to-1 binding stoichiometry was determined from NMR and isothermal titration calorimetry (ITC) investigations, and these experiments indicated that association is enthalpically favored with the tetra-Ndi (4a) and tetra-Dan (4b) strands forming hetero duplexes (4a:4b) with a stability constant of 350 000 M-1 at T = 318 K. Polyacrylamide gel electrophoresis (PAGE) also illustrated the strong interaction between 4a and 4b and support a 1-to-1 binding mode even when one component is in slight excess. Overall, this system is the first to utilize complementary aromatic units to drive discrete self-assembly in aqueous solution. This new approach for designing assemblies is encouraging for future development of duplex systems with highly programmable modes of binding in solution or on surfaces.

  1. Coupled jump rotational dynamics in aqueous nitrate solutions.

    PubMed

    Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman

    2016-12-21

    A nitrate ion (NO3(-)) with its trigonal planar geometry and charges distributed among nitrogen and oxygen atoms can couple to the extensive hydrogen bond network of water to give rise to unique dynamical characteristics. We carry out detailed atomistic simulations and theoretical analyses to investigate these aspects and report certain interesting findings. We find that the nitrate ions in aqueous potassium nitrate solution exhibit large amplitude rotational jump motions that are coupled to the hydrogen bond rearrangement dynamics of the surrounding water molecules. The jump motion of nitrate ions bears certain similarities to the Laage-Hynes mechanism of rotational jump motions of tagged water molecules in neat liquid water. We perform a detailed atomic-level investigation of hydrogen bond rearrangement dynamics of water in aqueous KNO3 solution to unearth two distinct mechanisms of hydrogen bond exchange that are instrumental to promote these jump motions of nitrate ions. As observed in an earlier study by Xie et al., in the first mechanism, after breaking a hydrogen bond with nitrate ion, water forms a new hydrogen bond with a water molecule, whereas the second mechanism involves just a switching of hydrogen bond between the two oxygen atoms of the same nitrate ion (W. J. Xie et al., J. Chem. Phys. 143, 224504 (2015)). The magnitude as well as nature of the reorientational jump of nitrate ion for the two mechanisms is different. In the first mechanism, nitrate ion predominantly undergoes out-of-plane rotation, while in the second mechanism, in-plane reorientation of NO3(-) is favourable. These have been deduced by computing the torque on the nitrate ion during the hydrogen bond switching event. We have defined and computed the time correlation function for coupled reorientational jump of nitrate and water and obtained the associated relaxation time which is also different for the two mechanisms. These results provide insight into the relation between the

  2. Coupled jump rotational dynamics in aqueous nitrate solutions

    NASA Astrophysics Data System (ADS)

    Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman

    2016-12-01

    A nitrate ion (NO3-) with its trigonal planar geometry and charges distributed among nitrogen and oxygen atoms can couple to the extensive hydrogen bond network of water to give rise to unique dynamical characteristics. We carry out detailed atomistic simulations and theoretical analyses to investigate these aspects and report certain interesting findings. We find that the nitrate ions in aqueous potassium nitrate solution exhibit large amplitude rotational jump motions that are coupled to the hydrogen bond rearrangement dynamics of the surrounding water molecules. The jump motion of nitrate ions bears certain similarities to the Laage-Hynes mechanism of rotational jump motions of tagged water molecules in neat liquid water. We perform a detailed atomic-level investigation of hydrogen bond rearrangement dynamics of water in aqueous KNO3 solution to unearth two distinct mechanisms of hydrogen bond exchange that are instrumental to promote these jump motions of nitrate ions. As observed in an earlier study by Xie et al., in the first mechanism, after breaking a hydrogen bond with nitrate ion, water forms a new hydrogen bond with a water molecule, whereas the second mechanism involves just a switching of hydrogen bond between the two oxygen atoms of the same nitrate ion (W. J. Xie et al., J. Chem. Phys. 143, 224504 (2015)). The magnitude as well as nature of the reorientational jump of nitrate ion for the two mechanisms is different. In the first mechanism, nitrate ion predominantly undergoes out-of-plane rotation, while in the second mechanism, in-plane reorientation of NO3- is favourable. These have been deduced by computing the torque on the nitrate ion during the hydrogen bond switching event. We have defined and computed the time correlation function for coupled reorientational jump of nitrate and water and obtained the associated relaxation time which is also different for the two mechanisms. These results provide insight into the relation between the coupled

  3. Novel Superdielectric Materials: Aqueous Salt Solution Saturated Fabric

    PubMed Central

    Phillips, Jonathan

    2016-01-01

    The dielectric constants of nylon fabrics saturated with aqueous NaCl solutions, Fabric-Superdielectric Materials (F-SDM), were measured to be >105 even at the shortest discharge times (>0.001 s) for which reliable data could be obtained using the constant current method, thus demonstrating the existence of a third class of SDM. Hence, the present results support the general theoretical SDM hypothesis, which is also supported by earlier experimental work with powder and anodized foil matrices: Any material composed of liquid containing dissolved, mobile ions, confined in an electrically insulating matrix, will have a very high dielectric constant. Five capacitors, each composed of a different number of layers of salt solution saturated nylon fabric, were studied, using a galvanostat operated in constant current mode. Capacitance, dielectric constant, energy density and power density as a function of discharge time, for discharge times from ~100 s to nearly 0.001 s were recorded. The roll-off rate of the first three parameters was found to be nearly identical for all five capacitors tested. The power density increased in all cases with decreasing discharge time, but again the observed frequency response was nearly identical for all five capacitors. Operational limitations found for F-SDM are the same as those for other aqueous solution SDM, particularly a low maximum operating voltage (~2.3 V), and dielectric “constants” that are a function of voltage, decreasing for voltages higher than ~0.8 V. Extrapolations of the present data set suggest F-SDM could be the key to inexpensive, high energy density (>75 J/cm3) capacitors. PMID:28774037

  4. Isothermal and nonisothermal decomposition of famotidine in aqueous solution.

    PubMed

    Junnarkar, G H; Stavchansky, S

    1995-04-01

    The kinetics of hydrolysis of famotidine in aqueous solution was studied by isothermal and nonisothermal method over the pH range of 1.71 to 10.0. Nonisothermal kinetics was studied with the purpose of determining its use in the establishment of the expiration date of pharmaceutical preparations, particularly drugs in solutions and for assessment of stability characteristics of pharmaceutical formulations during the development stage. A comparison of isothermal (55, 70 and 85 degrees C) and nonisothermal kinetics was performed. Aqueous solutions of famotidine were buffered at pH 1.71, 2.24, 2.66, 4.0, 8.5, 9.0 and 10.0 were used. In the nonisothermal studies, the temperature rate of the reaction was continuously varied throughout the experiment. The energies of activation were found to be in close agreement for isothermal and nonisothermal studies, indicating that nonisothermal studies may save considerable amount of time in the early stages of drug development and stability testing. Logk-pH profiles were constructed for 55, 70 and 85 degrees C from the first-order rate constants obtained from isothermal studies at pH values ranging from 1.71 to 10.00. The pH-rate profile indicated that famotidine undergoes specific acid catalysis in the acidic region and general base catalysis in the alkaline region. Hydrolysis in the acidic and alkaline media resulted in the formation of four and five degradation products, respectively. A possible degradation pathway for the acidic and alkaline hydrolysis was discussed.

  5. Mercury(II) Penicillamine Complex Formation in Alkaline Aqueous Solution

    SciTech Connect

    Leung, B.O.; Jalilehvand, F.; Mah, V.

    2009-06-01

    The complex formation between mercury(II) and penicillamine (H{sub 2}Pen = 3,3'-dimethyl cysteine) in alkaline aqueous solutions (pH {approx}2) has been investigated with extended X-ray absorption fine structure (EXAFS) and {sup 199}Hg NMR spectroscopy. By varying the penicillamine concentration (C{sub H{sub 2}Pen} = 0.2--1.25 M) in {approx}0.1 M Hg(II) solutions, two coexisting major species [Hg(Pen){sub 2}]{sup 2-} and [Hg(Pen){sub 3}]{sub 4-} were characterized with mean Hg-S bond distances 2.34(2) and 2.44(2) {angstrom}, respectively. The [Hg(Pen){sub 2}]{sup 2-} complex with two deprotonated penicillamine ligands forms an almost linear S-Hg-S entity with two weak chelating Hg-N interactions at the mean Hg-N distance 2.52(2) {angstrom}. The same type of coordination is also found for the corresponding [Hg(Cys){sub 2}]{sup 2-} complex in alkaline aqueous solution with the mean bond distances Hg-S 2.34(2) {angstrom} and Hg-N 2.56(2) {angstrom}. The relative amounts of the [Hg(Pen){sub 2}]{sup 2-} and [Hg(Pen){sub 3}]{sup 4-} complexes were estimated by fitting linear combinations of the EXAFS oscillations to the experimental spectra. Also their {sup 199}Hg NMR chemical shifts were used to evaluate the complex formation, showing that the [Hg(Pen){sub 3}]{sup 4-} complex dominates already at moderate excess of the free ligand ([Pen{sup 2-}] > {approx} 0.1 M).

  6. Molecular dynamics simulation of biomembranes in aqueous solution

    NASA Astrophysics Data System (ADS)

    Bostick, David Lee

    In recent years, the developments in classical molecular dynamics simulation have allowed for an atomistic depiction of mesoscopic biological systems. With the awareness of such developments, the natural strive of the scientific community has been to increase the size of such simulated systems [70]. Nonetheless, the subtleties in the properties of biomembranes require an unusually thoughtful approach [70, 203]. In this work, a hierarchical approach is taken, with respect to system complexity, in the classical molecular dynamics simulation of biomembrane systems in aqueous solution. A progression of simulation studies is presented that begins with the analysis of the interfacial properties of neat bilayers composed of zwitterionic (phosphatidylcholine) lipids in both pure water and in electrolyte. We move on to study mixed bilayers containing zwitterionic (phosphatidylcholine) and acidic (phosphatidylserine) lipids with counterions immersed in electrolyte. Yet another layer of complexity is added to the problem by studying hydrated bilayers containing phosphatidylcholine lipids and cholesterol. Finally, we address the semipermeable nature of biomembranes by studying two membrane-channel systems. We start with a simple model membrane-channel consisting of a six-helix alamethicin bundle embedded in a hydrated phosphatidylcholine bilayer. The knowledge gained from this study is then carried over to the simulation of a large membrane-embedded prokaryotic ClC Cl-/H + antiporter, utilizing a free-energetic analysis to reveal the role of protons in the Cl- transport mechanism. Throughout the progression, methods are developed and used in the analysis of interfacial aqueous solution structure, ion-membrane binding, lipid structural properties, inter-lipid hydrogen bonded complexation, and electrostatics at the membrane interface. The developments reveal the layered nature of water near the rugged, molecularscale aqueous solution/membrane interface and its electrostatic

  7. Infrared spectroscopy of aqueous ionic salt solutions at low concentrations

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Gessinger, Véronique; van Driessche, Caroline; Larouche, Pascal; Chapados, Camille

    2007-05-01

    The analysis by infrared spectroscopy of aqueous solutions of the binary inorganic salts NaI and NaCl and the ternary salts CaCl2 and BaCl2 at concentrations from 1000to2mM was carried out to complement a previous study done at higher concentrations on nine binary salts (alkali halides) and one ternary salt (MgCl2) [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 2664 (2001)]. These salts are completely ionized in aqueous solutions, forming monoatomic species that do not absorb IR but that perturb the surrounding water, modifying its spectrum. The factor analysis of the spectra revealed that all these salt solutions were composed of two water types: pure water and salt solvated water. The authors obtained pure salt solvated water spectra for all the salts using an extrapolation technique. The water types obtained are constant for the binary and ternary salts down to 2mM. For the binary salts, we determine that 5.0 and 4.0 water molecules are solvated to the Na +-Cl- and Na+-I- ion pairs, respectively. These numbers are the same as that obtained at higher concentrations. For the new ternary salts, we find that 6.0 and 8.0 water molecules are solvated to Ca++-(Cl-)2 and Ba++-(Cl-)2 ion pairs, respectively. These numbers are higher than the four water molecules solvated to Mg++-(Cl-)2 ion pairs determined previously, but show a progression that follows their atomic numbers. These results constitute new experimental results on "simple" systems whose molecular organization is still a matter of debate. The IR method that probes the system at the molecular level is a method different than the macroscopic ones that give the activity coefficients. The IR gives direct observation at the molecular level of the strong ion-water interactions that are often neglected and its water structure not considered in macroscopic methods. The present results and their analysis together with those obtained by other methods will facilitate the determination of the organization of these

  8. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

    2004-11-01

    Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight. copyright 2004 Elsevier Ltd.

  9. Osmotic potential calculations of inorganic and organic aqueous solutions over wide solute concentration levels and temperatures

    SciTech Connect

    Cochrane, T. T.; Cochrane, T. A.

    2016-01-15

    Purpose: To demonstrate that the authors’ new “aqueous solution vs pure water” equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures. Methods: The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of “free” water molecules per unit volume of solution, “N{sub f},” and (c) the “t” factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate N{sub f} was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors’ equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures. Results: The provisional equations formulated to calculate N{sub f}, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of N{sub f

  10. Chemical metallization of KMPR photoresist polymer in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zeb, Gul; Duong, Xuan Truong; Vu, Ngoc Pi; Phan, Quang The; Nguyen, Duc Tuong; Ly, Viet Anh; Salimy, Siamak; Le, Xuan Tuan

    2017-06-01

    While conventional methods for preparing thin films of metals and metallic alloys on insulating substrates in the field of microelectromechanical systems (MEMS) include vapor deposition techniques, we demonstrate here that electroless deposition can be considered as an alternate efficient approach to metallize the surface of insulating substrates, such as KMPR epoxy photoresist polymer. In comparison with the physical and chemical vapor deposition methods, which are well-established for metallization of photoresist polymers, our electroless nickel plating requires only immersing the substrates into aqueous solutions in open air at low temperatures. Thin films of nickel alloy have been deposited electrolessly on KMPR surface, through a cost-effective and environmental chromium-free process, mediated through direct grafting of amine palladium complexes in aqueous medium. This covalent organic coating provides excellent adhesion between KMPR and the nickel film and allows better control of the palladium catalyst content. Covalent grafting and characterization of the deposited nickel film have been carried out by means of Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy techniques.

  11. DNA dynamics in aqueous solution: opening the double helix

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Ross, W. S.; Tinoco, I. Jr; MacElroy, R. D. (Principal Investigator)

    1990-01-01

    The opening of a DNA base pair is a simple reaction that is a prerequisite for replication, transcription, and other vital biological functions. Understanding the molecular mechanisms of biological reactions is crucial for predicting and, ultimately, controlling them. Realistic computer simulations of the reactions can provide the needed understanding. To model even the simplest reaction in aqueous solution requires hundreds of hours of supercomputing time. We have used molecular dynamics techniques to simulate fraying of the ends of a six base pair double strand of DNA, [TCGCGA]2, where the four bases of DNA are denoted by T (thymine), C (cytosine), G (guanine), and A (adenine), and to estimate the free energy barrier to this process. The calculations, in which the DNA was surrounded by 2,594 water molecules, required 50 hours of CRAY-2 CPU time for every simulated 100 picoseconds. A free energy barrier to fraying, which is mainly characterized by the movement of adenine away from thymine into aqueous environment, was estimated to be 4 kcal/mol. Another fraying pathway, which leads to stacking between terminal adenine and thymine, was also observed. These detailed pictures of the motions and energetics of DNA base pair opening in water are a first step toward understanding how DNA will interact with any molecule.

  12. Strong adhesion and cohesion of chitosan in aqueous solutions

    PubMed Central

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N.; Hwang, Dong Soo

    2014-01-01

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0–8.5), achieving a maximum value at pH 3.0 after a contact time of 1 hr (Wad ~6.4 mJ/m2). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~8.5 mJ/m2) between the films was measured with increasing contact times up to 1 hr at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan based load-bearing materials. PMID:24138057

  13. Colloidal Stability of Graphene Oxide Nanosheets in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    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.

  14. Strong adhesion and cohesion of chitosan in aqueous solutions.

    PubMed

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N; Hwang, Dong Soo

    2013-11-19

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0-8.5), achieving a maximum value at pH 3.0 after a contact time of 1 h (Wad ~ 6.4 mJ/m(2)). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~ 8.5 mJ/m(2)) between the films was measured with increasing contact times up to 1 h at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan-based load-bearing materials.

  15. DNA dynamics in aqueous solution: opening the double helix

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Ross, W. S.; Tinoco, I. Jr; MacElroy, R. D. (Principal Investigator)

    1990-01-01

    The opening of a DNA base pair is a simple reaction that is a prerequisite for replication, transcription, and other vital biological functions. Understanding the molecular mechanisms of biological reactions is crucial for predicting and, ultimately, controlling them. Realistic computer simulations of the reactions can provide the needed understanding. To model even the simplest reaction in aqueous solution requires hundreds of hours of supercomputing time. We have used molecular dynamics techniques to simulate fraying of the ends of a six base pair double strand of DNA, [TCGCGA]2, where the four bases of DNA are denoted by T (thymine), C (cytosine), G (guanine), and A (adenine), and to estimate the free energy barrier to this process. The calculations, in which the DNA was surrounded by 2,594 water molecules, required 50 hours of CRAY-2 CPU time for every simulated 100 picoseconds. A free energy barrier to fraying, which is mainly characterized by the movement of adenine away from thymine into aqueous environment, was estimated to be 4 kcal/mol. Another fraying pathway, which leads to stacking between terminal adenine and thymine, was also observed. These detailed pictures of the motions and energetics of DNA base pair opening in water are a first step toward understanding how DNA will interact with any molecule.

  16. Standard enthalpies of formation for glycyl-tyrosine and products of its dissociation in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Kochergina, L. A.; Badelin, V. G.; Krutova, O. N.; Volkov, A. V.; Damrina, K. V.

    2015-07-01

    The enthalpies of solution of crystalline glycyl-tyrosine in water and potassium hydroxide aqueous solutions are determined at 298.15 K by means of direct calorimetry. Standard enthalpies of formation for dipeptide and its products of dissociation in an aqueous solution are calculated.

  17. The chemistry of drying an aqueous solution of salts.

    PubMed

    Takenaka, Norimichi; Takayama, Kayoko; Ojiro, Naofumi; Shimazaki, Wataru; Ohira, Kingo; Soda, Hiroyuki; Suzue, Takahiko; Sadanaga, Yasuhiro; Bandow, Hiroshi; Maeda, Yasuaki

    2009-11-05

    The fate of salts in drying aqueous solution was investigated. In the drying of acidic solutions, weak acid ions and chloride ions combine with protons and evaporate, depending on the proton concentration. In the drying of alkaline solutions, weak acid ions evaporate or remain as salts depending on the ratio of the concentrations of excess nonvolatile cations (the difference between concentrations of nonvolatile cation and nonvolatile anion) to volatile anions defined as DeltaCA. Under neutral and alkaline conditions, the fate of nitrite depends not only on DeltaCA but also on the drying speed. Nitrite is converted to N2, which is formed by reacting nitrite with ammonium (denitrification), NO and NO2, HONO and salts. In urban areas, nitrite and ammonium can appear in high concentrations in dew. HONO in the atmosphere affects the ozone concentration, but dew formation decreases the concentration of HONO. If chemical denitrification occurs, nitrogen species will decrease in the environment, and as a result, the ozone concentration could decrease. Ozone levels show an ozone depression when dew formed, and a Box model simulation showed an ozone depression by decreasing HONO levels.

  18. Molecular Dynamics Simulation Studies of Caffeine Aggregation in Aqueous Solution

    PubMed Central

    Tavagnacco, Letizia; Schnupf, Udo; Mason, Philip E.; Saboungi, Marie-Louise; Cesàro, Attilio; Brady, John W.

    2011-01-01

    Molecular dynamics simulations were carried out on a system of eight independent caffeine molecules in a periodic box of water at 300 K, representing a solution near the solubility limit for caffeine at room temperature, using a newly-developed CHARMM-type force field for caffeine in water. Simulations were also conducted for single caffeine molecules in water using two different water models (TIP3P and TIP4P). Water was found to structure in a complex fashion around the planar caffeine molecules, which was not sensitive to the water model used. As expected, extensive aggregation of the caffeine molecules was observed, with the molecules stacking their flat faces against one another like coins, with their methylene groups staggered to avoid steric clashes. A dynamic equilibrum was observed between large n-mers, including stacks with all eight solute molecules, and smaller clusters, with the calculated osmotic coefficient being in acceptable agreement with the experimental value. The insensitivity of the results to water model and the congruence with experimental thermodynamic data suggest that the observed stacking interactions are a realistic representation of the actual association mechanism in aqueous caffeine solutions. PMID:21812485

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

    PubMed

    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.

  20. Neutron dosimetry using aqueous solutions of lithium acetate

    SciTech Connect

    Rakovan, Lance John

    1996-01-01

    A thermal neutron dosimetry system using the 6Li(n,α)3H reaction and liquid scintillation counting of tritium was developed. Lithium acetate was chosen to supply the 6Li in the aqueous dosimetry solutions. Neutron irradiations were completed using The Ohio State University Research Reactor. After two sets of samples were irradiated, variables in the system such as the mass of lithium acetate in the solutions and the counting window of the liquid scintillation counter used to analyze the sample were chosen. The system was evaluated by completing two sets of 23 minute irradiations with the reactor at 500 kW, 50 kW, 5 kW, and one irradiation at 500 W. The samples irradiated at 500 W were below the threshold of the system, and could not be used. Prompt analysis was essential due to loss of detectable emissions in the dosimetry solutions over time. The thermal neutron fluences calculated with the data from the samples were compared to the fluences determined from gold wire irradiations. The fluence values differed at most by 6%. The fluence values calculated from the samples were consistently less than those determined from the gold wires.

  1. Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles

    NASA Astrophysics Data System (ADS)

    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.

  2. Multi-basin dynamics of a protein in aqueous solution

    SciTech Connect

    Garcia, A.E.

    1994-10-01

    A molecular dynamics simulation of crambin in aqueous solution shows that motions are characteristic of non-linear systems. The authors describe typical non-linear excitations, such as intermittency, for various representations of the protein dynamics and structure. The protein backbone dihedral angles show fast correlated transitions from one minimum well to another. Each transition is followed by small overdamped oscillations. Equal-time cross correlations of all ({phi},{psi}) angles show that correlations are extended along the backbone chain. An analysis based on a generalized least squares fitting of the protein fluctuations along vectors show that a small set of molecule optimal dynamic coordinates (MODC) describe most of the protein fluctuations. In addition, the MODC describe a trajectory where the protein conformation jumps from one minimum well to another. An extension of the MODC describing 2- and 3-dimensional cuts of the protein configurational space clearly shows a trajectory around multiple basins of attraction.

  3. Aggregation behavior of bile salts in aqueous solution.

    PubMed

    Coello, A; Meijide, F; Núñez, E R; Tato, J V

    1996-01-01

    Freezing point depression, delta T/k, and pNa are measured and analyzed for aqueous solutions of trihydroxy (NaTC) and dihydroxy (NaDC and NaTDC) bile salts. The results show the existence of break points in the plot of delta T/k vs molality at 0.018, 0.013, and 0.007 m, respectively, in good agreement with previous published critical micelle concentration values. Above the break point bile salts form aggregates with average aggregation numbers of 2.59 +/- 0.12 (NaTC), 5.82 +/- 0.04 (NaDC), and 5.42 +/- 0.47 (NaTDC). Fractions of bound counterions are also deduced, being close to 0.3 for the three bile salts studied. This indicates that only one counterion is bound for every three monomers in the aggregate. The different structural models published for the bile salt aggregates are discussed.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

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

    2015-12-16

    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.

  6. Acid gas absorption in aqueous solutions of mixed amines

    SciTech Connect

    Rinker, E.B.; Ashour, S.S.; Sandall, O.C.

    1996-12-31

    A mass transfer model has been developed to describe the rate of absorption (or desorption) of H{sub 2}S and CO{sub 2} in aqueous blends of a tertiary and a secondary or a primary amine. The model is based on penetration theory, and all significant chemical reactions are incorporated in the model. The reactions are taken to be reversible, with reactions involving only a proton transfer considered to be at equilibrium. The particular amines studied in this research were methyldiethanolamine (MDEA), a tertiary amine, and diethanolamine (DEA), a secondary amine. Key physicochemical data needed in the model, such as diffusion coefficients, kinetic rate constants, and gas solubilities, were measured. Experimental absorption rates of CO{sub 2} and H{sub 2}S were measured in a model gas-liquid contacting device and were compared with model predictions. Experiments were carried out for single amine solutions (both MDEA and DEA) and for amine blends.

  7. γ-Irradiation of malic acid in aqueous solutions

    NASA Astrophysics Data System (ADS)

    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.

  8. Irradiation stability of folic Acid in powder and aqueous solution.

    PubMed

    Araújo, Michel M; Marchioni, Eric; Bergaentzle, Martine; Zhao, Minjie; Kuntz, Florent; Hahn, Emeline; Villavicencio, Anna Lucia C H

    2011-02-23

    This study attempts to examine the folic acid stability after irradiation treatment, under different physical states, pH values, and atmosphere conditions. Aqueous folic acid samples, folic acid in powder, and wheat flour fortified with folic acid were irradiated by an electron beam (E-beam) between 0 (control) and 10.0 kGy. It was realized that the physical state of folic acid plays an important role on its stability toward E-beam processing, being largely unstable in solution, no matter the pH and atmosphere conditions assayed. Otherwise, folic acid in powder showed huge irradiation stability, even when mixed in a dry food matrix, such as fortified wheat flour samples.

  9. Removal of lead from aqueous solutions by Penicillium biomass

    SciTech Connect

    Hui Niu; Xue Shu Xu; Jian Hua Wang . Dept. of Chemical Engineering); Volesky, B. . 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].

  10. Hydrothermal Dehydration of Aqueous Fructose Solutions in a Closed System

    SciTech Connect

    Yao, Chunhua; Shin, Yongsoon; Wang, Li Q.; Windisch, Charles F.; Samuels, William D.; Arey, Bruce W.; Wang, Chong M.; Risen Jr., William M.; Exarhos, Gregory J.

    2007-10-25

    The synthesis of materials with targeted size and shape has attracted much attention. Specifically, colloidal spheres with targeted and uniform sizes have opened the door for a variety of applications associated with drug delivery, and manipulation of light (photonic band-gap crystals). Surface modification is a key to realizing many of these applications owing to the inherent inert surface.The remarkable transformation of carbohydrate molecules including sugars to homogeneous carbon spheres is found to readily occur by a dehydration mechanism and subsequent sequestering in aqueous solutions that are heated at 160-180oC in a pressurized vessel. Under such conditions, these molecules actually dehydrate even though they are dissolved in water. Size-tunable metal and metal oxides with uniform shells have also been prepared by using carbon spheres as templates.

  11. Ionizing radiation induced degradation of monuron in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Kovács, Krisztina; He, Shijun; Míle, Viktória; Földes, Tamás; Pápai, Imre; Takács, Erzsébet; Wojnárovits, László

    2016-07-01

    The decomposition of monuron was investigated in dilute aqueous solutions using pulse radiolysis and γ-radiolysis in order to identify the intermediates and final products. The main reaction takes place between monuron and the hydroxyl radicals yielding hydroxycyclohexadienyl type radicals with a second order rate constant of (7.4±0.2)×109 mol-1 dm3 s-1. In •OH reactions, the aminyl and phenoxyl radicals may also form. Dechlorination was observed in both hydroxyl radical and hydrated electron reactions. The •OH induced dechlorination reactions are suggested to occur through OH substitution or phenoxyl radical formation. The rate of oxidation is very high in the presence of dissolved oxygen. Some of the results are also supported by quantum chemical calculations.

  12. Protein thermal stabilization in aqueous solutions of osmolytes.

    PubMed

    Bruździak, Piotr; Panuszko, Aneta; Jourdan, Muriel; Stangret, Janusz

    2016-01-01

    Proteins' thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared with FTIR hydration studies' results. Selected osmolytes increased lysozyme's thermal stability in the following order: Gly>NMG>TMAO≈DMG>TMG. Theoretical calculations (DFT) showed clearly that osmolytes' amino group protons and water molecules interacting with them played a distinctive role in protein thermal stabilization. The results brought us a step closer to the exact mechanism of protein stabilization by osmolytes.

  13. Hydrate-based heavy metal separation from aqueous solution

    PubMed Central

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

    2016-01-01

    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. PMID:26887357

  14. Infrared spectrophotometric analysis of acidified aqueous sodium oleate solutions

    NASA Astrophysics Data System (ADS)

    Drzymala, Jan; Kielkowska, M. M.

    Infrared spectroscopy was applied to the analysis of 10 -3 M aqueous sodium oleate solutions titrated with 0.2 M HCl. From characteristic absorption bands of sodium oleate at 1560 cm -1 and oleic acid at 1710 cm -1 the degree of oleate ion neutralization in the titrated system at varying pH was calculated.It was found that the pH-metric titration curve of oleate ions differs considerably from the theoretical curve calculated for the reaction Ol -aq + H + = HOl liq, taking the solubility product of oleic acid equal to 12.5. Most likely aggregates of oleate ons (micelles) are formed during titration and account for the deviation of the titration curves from theory.

  15. Photoreduction of methyl viologen in aqueous neutral solution without additives

    NASA Astrophysics Data System (ADS)

    Ebbesen, T. W.; Levey, G.; Patterson, L. K.

    1982-08-01

    The direct photoreduction of methyl viologen (paraquat) in aqueous solution to the reducd species radical cation MV(2+)Cl(-)2 was examined to study its effectiveness as a herbicide and in solar photochemical energy conversion devices. Dissolved crystalline cations were found to vary in absorption spectrum with added Cl(-), and excitation with a nitrogen laser at 377 nm indicated the presence of a transient species absorbing below 400 nm. The oxidation of Cl ions by a photolysis-excited state of the MV(2+) is shown to have a quantum yield of 0.2 at 337 nm, using anthracene as a reference. A parallel pathway to normal toxic oxidation of the substance on plants is suggested, involving the photoproduction of the radical Cl(2-), which reacts with thymine, uracil, guanine, histidine, thyrosine, tryptophan, cysteine, and ascorbic acid. The observed properties are suggested to be useful in the photoreduction and oxidation of water.

  16. Paracetamol degradation in aqueous solution by non-thermal plasma

    NASA Astrophysics Data System (ADS)

    Baloul, Yasmine; Aubry, Olivier; Rabat, Hervé; Colas, Cyril; Maunit, Benoît; Hong, Dunpin

    2017-08-01

    This study deals with paracetamol degradation in water using a non-thermal plasma (NTP) created by a dielectric barrier discharge (DBD). The effects of the NTP operating conditions on the degradation were studied, showing that the treatment efficiency of the process was highly dependent on the electrical parameters and working gas composition in the reactor containing the aqueous solution. A conversion rate higher than 99% was reached with an energy yield of 12 g/kWh. High resolution mass spectrometry (HRMS) measurements showed that the main species produced in water during the process were nitrogen compounds, carboxylic acids and aromatic compounds. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

  17. Seeded batch crystallization of ammonium aluminum sulfate from aqueous solution

    NASA Astrophysics Data System (ADS)

    Kubota, Noriaki; Onosawa, Masahiro

    2009-10-01

    Seed crystals of ammonium aluminum sulfate ((NH 4)Al(SO 4) 2··12H 2O) were grown in aqueous solution by cooling. The temperature of a crystallizer was lowered with no control by circulating cooling water through the jacket. It fell in an exponential manner. The effects of seed amount and size on the product crystal size distribution were examined. The product crystals obtained were of narrow and uni-modal size distribution with suppressed secondary nucleation if seed crystals were loaded more than a critical value. The critical value was determined and well compared with previously reported values for other material systems. This crystallization technique does not need any prior knowledge of the kinetics of crystal growth and nucleation. It is simple and robust, and can be easily applied to an existing crystallizer without installing any additional control systems.

  18. Synergistic adsorption of phenol from aqueous solution onto polymeric adsorbents.

    PubMed

    Ming, Zhang W; Long, Chen J; Cai, Pan B; Xing, Zhang Q; Zhang, B

    2006-02-06

    Adsorption of phenol from aqueous solution onto a nonpolar adsorbent, aminated adsorbent and weak base adsorbent (Amberlite XAD4, NDA103 and Amberlite IRA96C, respectively) at temperatures from 293 to 313K was studied for the weak interactions between the phenol molecules and the polymeric adsorbents. Isotherms of Langmuir and Freundlich equation with characteristic parameters for different adsorbents were well fitted to the batch equilibrium adsorption data. The adsorption capacity on NDA103 driven by hydrogen bonding and van der Waals interaction together is higher than that on IRA96C driven by hydrogen bonding interaction only and on XAD4 driven by van der Waals interaction only. For evaluating synergistic adsorption for phenol-water systems onto polymeric adsorbents, the adsorption capacity is normalized to the amounts of specific surface area and amino groups of adsorbents. The synergistic effect with other weak interactions would contribute more to the adsorption as acting simultaneously than that of acting individually.

  19. Pervaporation separation of aqueous alcohol solution through asymmetric polycarbonate membrane

    SciTech Connect

    Lee, K.R.; Liu, M.J.; Lai, J.Y. )

    1994-01-01

    In the present work the separation of aqueous alcohol mixtures through wet-phase inversion prepared polycarbonate membranes was studied by using the pervaporation process. The formation of asymmetric pervaporation membranes was discussed in terms of the presence of a nonsolvent in the casting solution, the polycarbonate concentration, and the kinds of coagulation media. The effects of feed composition, swelling degree, and the size of the alcohols on the pervaporation performances were investigated. The rate of liquid-liquid demixing increases with a decreasing number of carbon atoms of the alcohol coagulation medium. The permeation rate of the pervaporation process for the nonsolvent-added membrane was much higher than that of the membrane without nonsolvent additive. In binary alcohol mixtures, the permselectivities of small-sized alcohols through the asymmetric membrane are decided by two factors: preferential solubility of larger-sized alcohol and predominant diffusivity of small-sized alcohol. 19 refs., 8 figs., 6 tabs.

  20. Diffusion-viscosity decoupling in supercooled glycerol aqueous solutions.

    PubMed

    Trejo González, José A; Longinotti, M Paula; Corti, Horacio R

    2015-01-08

    The diffusion of ferrocene methanol in supercooled glycerol-water mixtures has been measured over a wide viscosity range, which allowed analyzing the composition dependence of the Stokes-Einstein breakdown (diffusion-viscosity decoupling). The observed decoupling exhibits a common behavior for all studied compositions (glycerol mass fractions between 0.7 and 0.9), determined by the reduced temperature (T/Tg) of the mixtures. This result differs from that reported previously for the diffusion of glycerol in its aqueous solutions, where the reduced temperature for the decoupling decreases with increasing water content. We conclude that the contradictory results are only apparent, and they can be explained by the use of inconsistent extrapolated values of the viscosity of the glycerol-water mixtures in the supercooled region.

  1. Radiation-induced degradation of 4-chloroaniline in aqueous solution

    NASA Astrophysics Data System (ADS)

    Sánchez, M.; Wolfger, H.; Getoff, N.

    2002-12-01

    The radiation-induced decomposition of 4-chloroaniline (4-ClA) was studied under steady-state conditions using aqueous solutions saturated with air, pure oxygen, N 2O, argon and argon in the presence of t-Butanol. Using HPLC-method, the initial G-values of the substrate degradation as well as of a number of radiolytic products were determined. The formation of aminophenols, chlorophenols, aniline and phenol in addition to chloride, ammonia, formaldehyde and mixture of aldehydes as well as carboxylic acids was studied as a function of absorbed dose. Based on the experimental data, probable reaction mechanisms for the degradation of 4-ClA by γ-rays and the formation of the identified products are presented.

  2. Effect of solute nature on the polyamorphic transition in glassy polyol aqueous solutions

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiharu

    2017-08-01

    I examined the polyamorphic behavior of glassy dilute aqueous solutions of polyols (ethylene glycol, glycerol, meso-erythritol, xylitol, and D-sorbitol) under pressure at low temperatures. Although the volume change of the glassy aqueous solution varied continuously against pressure, the rate of the volume change appeared to vary discontinuously at the onset pressure of the gradual polyamorphic transition. It is thought that low-density liquid-like solvent water and high-density liquid-like solvent water coexist during the transition. Moreover, the existence of a solute induces the shift of polyamorphic transition to the lower-pressure side. The effect of a solute on the polyamorphic transition becomes larger in the order ethylene glycol, glycerol, meso-erythritol, xylitol, and D-sorbitol. Therefore, the solute can become a variable controlling the polyamorphic state of liquid water. This experimental result suggests that the metastable-equilibrium phase boundary between the low-density and the high-density amorphs for pure water is likely to be located at 0.22-0.23 GPa at about 150 K, which is slightly larger than the previously estimated pressure. Moreover, the solute-nature dependence on the polyamorphic transition seems to connect to that on the homogeneous nucleation temperature of polyol aqueous solution at ambient pressure. The region in which a low-density liquid appears coincides with the region in which the nucleus of ice Ih appears, suggesting that the formation of a low-density liquid is a precursory phenomenon of the nucleation of ice Ih.

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

    PubMed

    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.

  4. Supercharging Protein Complexes from Aqueous Solution Disrupts their Native Conformations

    NASA Astrophysics Data System (ADS)

    Sterling, Harry J.; Kintzer, Alexander F.; Feld, Geoffrey K.; Cassou, Catherine A.; Krantz, Bryan A.; Williams, Evan R.

    2012-02-01

    The effects of aqueous solution supercharging on the solution- and gas-phase structures of two protein complexes were investigated using traveling-wave ion mobility-mass spectrometry (TWIMS-MS). Low initial concentrations of m-nitrobenzyl alcohol ( m-NBA) in the electrospray ionization (ESI) solution can effectively increase the charge of concanavalin A dimers and tetramers, but at higher m-NBA concentrations, the increases in charge are accompanied by solution-phase dissociation of the dimers and up to a ~22% increase in the collision cross section (CCS) of the tetramers. With just 0.8% m-NBA added to the ESI solution of a ~630 kDa anthrax toxin octamer complex, the average charge is increased by only ~4% compared with the "native" complex, but it is sufficiently destabilized so that extensive gas-phase fragmentation occurs in the relatively high pressure regions of the TWIMS device. Anthrax toxin complexes exist in either a prechannel or a transmembrane channel state. With m-NBA, the prechannel state of the complex has the same CCS/charge ratio in the gas phase as the transmembrane channel state of the same complex formed without m-NBA, yet undergoes extensive dissociation, indicating that destabilization from supercharging occurs in the ESI droplet prior to ion formation and is not a result of Coulombic destabilization in the gas phase as a result of higher charging. These results demonstrate that the supercharging of large protein complexes is the result of conformational changes induced by the reagents in the ESI droplets, where enrichment of the supercharging reagent during droplet evaporation occurs.

  5. Adhesion of bacteria to pyrophyllite clay in aqueous solution.

    PubMed

    Kang, Jin-Kyu; Lee, Chang-Gu; Park, Jeong-Ann; Kim, Song-Bae; Choi, Nag-Choul; Park, Seong-Jik

    2013-01-01

    The aim of this study was to investigate the adhesion of bacteria (Escherichia coli) to pyrophyllite clay using batch and flow-through column experiments. Batch results demonstrated that pyrophyllite was effective in removing bacteria (94.5 +/- 2.0%) from aqueous solution (1 mM NaCl solution; pyrophyllite dose of 1 g/ml). At solution pH 7.1, negatively-charged bacteria could be removed due to their adhesion to positively-charged surfaces of pyrophyllite (point of zero charge = 9.2). Column results showed that pyrophyllite (per cent removal of 94.1 +/- 2.3%) was far more effective in bacterial adhesion than quartz sand (53.6 +/- 5.3%) under the given experimental conditions (flow rate of 0.3 ml/min; solution of 1 mM NaCl + 0.1 mM NaHCO3). Bacterial removal in pyrophyllite columns increased from 90 to 100% with decreasing flow rate from 0.6 to 0.15 ml/min due to increasing contact time between bacteria and filter materials. In addition, bacterial removal remained relatively constant at 94-97% even though NaHCO3 concentration increased from 0.1 to 10 mM (flow rate of 0.3 ml/min). This could be related to the fact that pyrophyllite remained positively-charged even though the solution conditions changed. This study demonstrates that pyrophyllite could be used as adsorptive filter materials in the removal of bacteria.

  6. Supercharging Protein Complexes from Aqueous Solution Disrupts their Native Conformations

    PubMed Central

    Sterling, Harry J.; Kintzer, Alexander F.; Feld, Geoffrey K.; Cassou, Catherine A.; Krantz, Bryan A.; Williams, Evan R.

    2011-01-01

    The effects of aqueous solution supercharging on the solution- and gas-phase structures of two protein complexes were investigated using traveling-wave ion mobility-mass spectrometry (TWIMS-MS). Low initial concentrations of m-nitrobenzyl alcohol (m-NBA) in the electrospray ionization (ESI) solution can effectively increase the charge of concanavalin A dimers and tetramers, but at higher m-NBA concentrations, the increases in charge are accompanied by solution-phase dissociation of the dimers and up to a ~22% increase in the collision cross section (CCS) of the tetramers. With just 0.8% m-NBA added to the ESI solution of a ~630 kDa anthrax toxin octamer complex, the average charge is increased by only ~4% compared to the “native” complex, but it is sufficiently destabilized so that extensive gas-phase fragmentation occurs in the relatively high pressure regions of the TWIMS device. Anthrax toxin complexes exist in either a pre-channel or a transmembrane channel state. With m-NBA, the prechannel state of the complex has the same CCS/charge ratio in the gas phase as the transmembrane channel state of the same complex formed without m-NBA, yet undergoes extensive dissociation, indicating that destabilization from supercharging occurs in the ESI droplet prior to ion formation and is not a result of coulombic destabilization in the gas phase as a result of higher charging. These results demonstrate that the supercharging of large protein complexes is the result of conformational changes induced by the reagents in the ESI droplets where enrichment of the supercharging reagent during droplet evaporation occurs. PMID:22161509

  7. Thermodynamic quantities of surface formation of aqueous electrolyte solutions VII. Aqueous solution of alkali metal nitrates LiNO3, NaNO3, and KNO3.

    PubMed

    Matubayasi, Norihiro; Yoshikawa, Ryuji

    2007-11-15

    To compare the effect of nitrate anions on the surface tension increments of aqueous solutions with that of halide anions, the surface tension of aqueous solutions of lithium nitrate, sodium nitrate, and potassium nitrate was measured as a function of temperature and concentration. It is shown that the surface tension of aqueous alkali metal nitrate solutions is determined primarily by the kinds of anions, since the surface tension increments of these nitrates were of the same magnitude. The importance of the electrical double layer at the surface is discussed in relation to these surface tension increments.

  8. Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution

    DTIC Science & Technology

    1990-03-01

    IIC FILE COPY Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution Susan Taylor and Louise Parker March...Engineers Cold Regions Research & Engineering Laboratory Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution...14 iii Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution SUSAN TAYLOR AND LOUISE

  9. Adsorption of phenolic compounds by organoclays: implications for the removal of organic pollutants from aqueous media.

    PubMed

    Park, Yuri; Ayoko, Godwin A; Kurdi, Róbert; Horváth, Erzsébet; Kristóf, Janos; Frost, Ray L

    2013-09-15

    Montmorillonite (MMT) was converted to organoclays by intercalation of cationic surfactants into its interlayer space. Two types of organoclays were prepared from different surfactants (DDTMA and DDDMA) at different surfactant loadings, and the structural changes in the clays investigated using various techniques. The arrangements of surfactant molecules in the interlayer space was visually aided by molecular mechanical calculation (MM calculation), and the adsorption capacities of MMT and the organoclays for the removal of p-chlorophenol (PCP) and p-nitrophenol (PNP) from aqueous solutions were tested under different conditions. Two adsorption isotherm models (Langmuir and Freundlich isotherms) were used to determine the best fit model and the Freundlich isotherm was found to provide better fit for both PCP and PNP. Due to its hydrophobic properties, the adsorption is more favourable for PNP than PCP. Overall, the adsorption capacity of the organoclays was significantly improved by intercalation with large surfactant molecules as well as highly loaded surfactants as the intercalation with large surfactant molecules created the partitioning phase, which strongly attracted large amounts of organic pollutants. Possible mechanisms and the implications of the results for the use of these organoclays as adsorbents for the removal of phenols from the environment are discussed.

  10. Catalytic destruction of hazardous organics in aqueous solutions

    SciTech Connect

    Baker, E.G.; Sealock, L.J. Jr.

    1988-04-01

    Pacific Northwest Laboratory (PNL) is developing a process for destroying hazardous organics and chlorinated organics in aqueous solutions. The process is targeted at liquid waste streams that are difficult and costly to treat with conventional or developing technologies. Examples of these waste streams include contaminated groundwater and surface water and industrial wastewater. Aqueous solutions are treated with a transition metal catalyst at 300/degree/C to 460/degree/C and 2000 to 5000 psig pressure to convert the wastes to innocuous gases. During proof-of-principle tests conducted in a 1-L batch reactor, destruction of over 99/percent/ (in most cases approaching 99.9/percent/) of the organic material was achieved. Hexone (methyl is isobutyl ketone, MIBK), p-cresol, hexane, benzene, and naphthalene were used as model waste materials. The only major product with all of the organic compounds was a gas containing 50/percent/ to 75/percent/ methane, 25/percent/ to 45/percent/ carbon dioxide, and 0/percent) to 5/percent/ hydrogen. Reduced nickel was the only effective catalyst and that the optimal operating conditions for destroying nonchlorinated organics were 350/degree/C to 400/degree/C, 2000 to 4000 psig, and 30/endash/ to 60/endash/min residence time. These tests also indicated that catalyst deactivation or fouling would not be a problem at these conditions. Chlorobenzene and trichloroethylene (TEC), were also tested. Destruction of both compounds was 99/percent/ or greater, but the products were different from those obtained from hydrocarbons. With TCE, the major product was carbon dioxide; with chlorobenzene the major product identified was benzene. In the tests with the chlorinated hydrocarbons, the chlorine was converted to HC1 and the reduced nickel was converted to nickel hydroxide, which may be detrimental to long-term catalyst activity. (15 refs., 8 figs., 6 tabs).

  11. Spontaneous insertion of lipopolysaccharide into lipid membranes from aqueous solution.

    PubMed

    Alam, Jahangir Md; Yamazaki, Masahito

    2011-02-01

    Lipopolysaccharide (LPS), one of the main components of outer membranes of Gram-negative bacteria, consists of a hydrophobic lipid (lipid A) with six hydrocarbon chains and a large hydrophilic polysaccharide chain. LPS plays endotoxic roles and can stimulate macrophages and B cells. To elucidate the mechanism of the interaction of LPS with various cell membranes, it is important to investigate the interaction of wild type LPS in a buffer with lipid membranes. In this report we investigated the interaction of low concentrations of LPS in a buffer with giant unilamellar vesicles (GUVs) of dioleoylphosphatidylcholine (DOPC) membrane in the liquid-crystalline (L(α)) phase and sphingomyelin (SM)/cholesterol(chol) (molar ration; 6/4) membrane in the liquid-ordered (lo) phase. We found that low concentrations (less than critical micelle concentration) of LPS in aqueous solution induced the shape changes such as the transformation from a prolate to a two-spheres-connected by a very narrow neck in the DOPC-GUVs and also in the SM/chol (6/4)-GUVs above their threshold concentrations. The analysis of the shape changes of the GUVs indicates that the monomers of LPS can insert spontaneously into the external monolayer of the lipid membranes of these GUVs from the aqueous solution. Moreover, higher concentrations of LPS induced the vesicle fission of SM/chol(6/4)-GUVs above its higher threshold concentration. The vesicle fission of GUVs is similar to those induced by single long chain amphiphiles such as lysophosphatidylcholine. On the basis of these results, we discuss the interaction of wild type LPS with lipid membranes and cell membranes. These results suggest that LPS molecules can insert spontaneously into the external monolayer of the plasma membranes composed of the L(α) phase-membrane and the microdomain in the lo phase. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  12. Removal of zirconium from aqueous solution by modified clinoptilolite.

    PubMed

    Faghihian, H; Kabiri-Tadi, M

    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(-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 degrees C and equilibration time of 24h 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(2)>0.998) with rate constant of 1.60x10(-1), 1.96x10(-1), 2.45x10(-1) and 2.02x10(-1)g mmol(-1)min(-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.

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

    PubMed

    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.

  14. A method for calculating the acid-base equilibria in aqueous and nonaqueous electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Tanganov, B. B.; Alekseeva, I. A.

    2017-06-01

    Concentrations of particles in acid-base equilibria in aqueous and nonaqueous solutions of electrolytes are calculated on the basis of logarithmic charts, activity coefficients, and equilibrium constants.

  15. Solubility of carbon dioxide in aqueous solutions of 2-amino-2-methyl-1,3-propanediol

    SciTech Connect

    Baek, J.I.; Yoon, J.H.

    1998-07-01

    The equilibrium solubility of carbon dioxide in aqueous solutions of 2-amino-2-methyl-1,3-propanediol (AMPD) has been measured at (30, 40, and 60) C and the partial pressure of carbon dioxide ranging from (0.5 to 3065) kPa. The concentrations of the aqueous solutions were (10 and 30) mass % AMPD. The tendency of the solubility of carbon dioxide in 30 mass % AMPD aqueous solution at 40 C was found to be similar to that in 30 mass % N-methyldiethanolamine aqueous solution.

  16. Thermodynamics of Water and Aqueous Solutions under Mantle Conditions

    NASA Astrophysics Data System (ADS)

    Brown, J. M.; Vance, S.; Bollengier, O.; Shaw, G. H.; Abramson, E.

    2014-12-01

    Interactions between aqueous solutions and rocks extending from the surface and through the deep mantle control the state and evolution of Earth. The accurate representation of the fluid chemical energy as a function of pressure, temperature and composition over a wide range of conditions is prerequisite in understanding phase equilibria and solubilities in multicomponent systems. End-member thermodynamic properties of water (densities, specific heats, sound speeds, and more) have been extensively explored in a regime below about 100 MPa and an available complex formulation for the Helmholtz free energy (IAPWS-95) accurately represents these data and a smaller number of measurements extending to 1 GPa. However, this parameterization systematically misfits higher pressure data and is not easily adjusted to provide a better description. To address these points, we developed a flexible framework for the acquisition and description of Gibbs' free energy of water and aqueous solutions. Through use of local basis functions, the thermodynamic state surface can be adjusted to account for improved experimental constraints or for results in new regimes of pressure and temperature. Based on our experimental work on pure water, MgSO4(aq), Na2SO4(aq), and ammonia-water mixtures, new insights are provided on the volumetric behavior of fluids at high pressure. For the ionic solutions, where the partial molar volume at infinite dilution, Vo, is dominated by electrostriction at low pressure, the initial pressure derivative of Vo is large. At high pressure, where Vo is more related to the "size" of the ions, it is only weakly pressure dependent. The non-ideal behavior of these ionic solutions over an extended range of pressures and temperatures is successfully described using a standard three-term parameterization representing solvent (Debye-Hückel), solvent-ion, and ion-ion interactions. The solvent-ion and ion-ion interaction parameters show less dependence on pressure and

  17. Method for removing trace pollutants from aqueous solutions

    DOEpatents

    Silver, Gary L.

    1986-01-01

    A method of substantially removing a trace metallic contaminant from a liquid containing the same comprises, adding an oxidizing agent to a liquid containing a trace amount of a metallic contaminant of a concentration of up to about 10.sup.-1 ppm, the oxidizing agent being one which oxidizes the contaminant to form an oxidized product which is insoluble in the liquid and precipitates therefrom, and the conditions of the addition being selected to ensure that the precipitation of the oxidized product is homogeneous, and separating the homogeneously precipitated product from the liquid.

  18. Removal of methylene blue from aqueous solutions by chemically modified bamboo.

    PubMed

    Guo, Jian-Zhong; Li, Bing; Liu, Li; Lv, Kangle

    2014-09-01

    Chemically modified bamboo (CMB) was utilized for removing methylene blue (MB) from aqueous media in the present study. The adsorbent was characterized by Fourier transform infrared (FTIR) spectra and elemental analysis, which confirms that carboxyl groups and diethylenetriamine were successfully introduced into the surface of bamboo. The effects of initial MB concentration (100-900mgL(-1)), contact time (15-315min), the pH of the solution (3-10), temperature (298-318K), adsorbent dosage (0.4-2.6gL(-1)) and salt concentration on the adsorption efficiency of CMB towards MB were investigated. It was found that the adsorption of MB in CMB fits Langmuir mode well, and the maximum adsorption capacity of CMB achieved 606mgg(-1) at 298K, which is much higher than those obtained from previously investigated bioadsorbents. The adsorption kinetics can be described by pseudo-second-order kinetic model, and the adsorption of MB on CMB was an exothermic process. The results of the present study suggest that CMB is an effective biosorbent for removal of organic pollutants from aqueous solutions.

  19. Viscosities of cetylpyridinium bromide solutions (aqueous and aqueous KBr) in the presence of alcohols and amines

    SciTech Connect

    David, S.L.; Kumar, S.; Kabir-ud-Din

    1997-01-01

    Among the large number of additives, alcohols hold a special place, being by far the most common cosurfactants which are added to surfactant-oil combinations to generate microemulsions. Though the studies using amines as cosurfactant in microemulsions are few, it has been proved that they are also potential candidates for such formulations. The effect of organic additives (aliphatic/aromatic amines or alcohols) on the viscosities of aqueous and 0.1 M KBr solutions of 0.05 or 0.1 M cetylpyridinium bromide have been measured under Newtonian flow conditions. The viscosity changed dramatically in the presence of KBr. This is explained by the favorable conditions produced by the salt which assists the micellar growth by organic additives with a concomitant enhancement in viscosity. Reasons for the effectiveness of these additives are suggested. The causes of the viscosity decrease at higher concentrations of the additive are also explained.

  20. Free radical generation by ultrasound in aqueous and nonaqueous solutions.

    PubMed Central

    Riesz, P; Berdahl, D; Christman, C L

    1985-01-01

    The physical principles underlying the oscillatory behavior of minute gas bubbles in liquids exposed to ultrasound are reviewed. Results from mathematical analyses suggest that these oscillations sometimes become unstable leading to transient cavitation in which a bubble violently collapses during a single acoustic half-cycle producing high temperatures and pressures. The role that micronuclei, resonant bubble size, and rectified diffusion play in the initiation of transient cavitation is explained. Evidence to support these theoretical predictions is presented with particular emphasis on sonoluminescence which provides some non-chemical evidence for the formation of free radicals. Acoustic methods for conducting sonochemical investigations are discussed. In aqueous solutions transient cavitation initially generates hydrogen atoms and hydroxyl radicals which may recombine to form hydrogen and hydrogen peroxide or may react with solutes in the gas phase, at the gas-liquid boundary or in the bulk of the solution. The analogies and differences between sonochemistry and ionizing radiation chemistry are explored. The use of spin trapping and electron spin resonance to identify hydrogen atoms and hydroxyl radicals conclusively and to detect transient cavitation produced by continuous wave and by pulsed ultrasound is described in detail. The study of the chemical effects of cavitation in organic liquids is a relatively unexplored area which has recently become the subject of renewed interest. Examples of the decomposition of solvent and solute, of ultrasonically initiated free-radical polymerization and polymer degradation are presented. Spin trapping has been used to identify radicals in organic liquids, in polymer degradation and in the decomposition of organometallic compounds. PMID:3007091

  1. Photoinduced reactions between Pb3O4 and organic dyes in aqueous solution under visible light.

    PubMed

    Zhou, Yangen; Long, Jinlin; Gu, Quan; Lin, Huaxiang; Lin, Huan; Wang, Xuxu

    2012-12-03

    Pb(3)O(4) could react with organic dyes in aqueous solution under visible light irradiation, in which Pb(3)O(4) was transformed into Pb(3)(CO(3))(2)(OH)(2) along with oxidation of the organic dyes. Cu(2+) has considerable effect on the reaction. In the presence of Cu(2+), MO (20 ppm) and RhB (10(-5) mol L(-1)) were completely degraded under visible light within 6 and 20 min, respectively, while both Pb(3)O(4) and Cu(2+) keep almost stable during photodegradation. The mechanisms of the reactions with and without Cu(2+) ions were studied. The photochemical system of Pb(3)O(4) cooperating with Cu(2+) ions is probably used for the treatment of organic pollutants in water under visible light.

  2. Adsorption of silver nanoparticles from aqueous solution on copper-based metal organic frameworks (HKUST-1).

    PubMed

    Conde-González, J E; Peña-Méndez, E M; Rybáková, S; Pasán, J; Ruiz-Pérez, C; Havel, J

    2016-05-01

    Silver nanoparticles (AgNP) are emerging pollutants. The use of novel materials such as Cu-(benzene 1,3,5-tricarboxylate, BTC) Metal-Organic Framework (MOFs), for AgNP adsorption and their removal from aqueous solutions has been studied. The effect of different parameters was followed and isotherm model was suggested. MOFs adsorbed fast and efficiently AgNP in the range C0 < 10 mg L(-1), being Freundlich isotherm (R = 0.993) these data fitted to. Among studied parameters a remarkable effect of chloride on sorption was found, thus their possible interactions were considered. The high adsorption efficiency of AgNP was achieved and it was found to be very fast. The feasibility of adsorption on Cu-(BTC) was proved in spiked waters. The results showed the potential interest of new material as adsorbent for removing AgNP from environment.

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

    PubMed

    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

  4. Isotherm-Based Thermodynamic Model for Solute Activities of Asymmetric Electrolyte Aqueous Solutions.

    PubMed

    Nandy, Lucy; Dutcher, Cari S

    2017-08-04

    Adsorption isotherm-based statistical thermodynamic models can be used to determine solute concentration and solute and solvent activities in aqueous solutions. Recently, the number of adjustable parameters in the isotherm model of Dutcher et al. J. Phys. Chem. A/C 2011, 2012, 2013 were reduced for neutral solutes as well as symmetric 1:1 electrolytes by using a Coulombic model to describe the solute - solvent energy interactions (Ohm et al. J. Phys. Chem. A 2015, Nandy et al. J. Phys. Chem. A 2016). Here, the Coulombic treatment for symmetric electrolytes is extended to establish improved isotherm model equations for asymmetric 1-2 and 1-3 electrolyte systems. The Coulombic model developed here results in prediction of activities and other thermodynamic properties in multicomponent systems containing ions of arbitrary charge. The model is found to accurately calculate osmotic coefficient over the entire solute concentration range with two model parameters, related to intermolecular solute-solute and solute-solvent spacing. The inorganic salts and acids treated here are generally considered to be fully dissociated. However, there are certain weak acids that do not dissociate completely, such as the bisulfate ion. In this work, partial dissociation of the bisulfate ion from sulfuric acid is treated as a mixture, with an additional model parameter which accounts for dissociation ratio of the dissociated ions to non-dissociated ions.

  5. Characterization of Chitin and Chitosan Molecular Structure in Aqueous Solution

    SciTech Connect

    Franca, Eduardo D.; Lins, Roberto D.; Freitas, Luiz C.; Straatsma, t. P.

    2008-11-08

    Molecular dynamics simulations have been used to characterize the structure of chitin and chitosan fibers in aqueous solutions. Chitin fibers, whether isolated or in the form of a β-chitin nanoparticle, adopt the so-called 2-fold helix with Φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)•••O5(n+1) responsible for the 2-fold helical motif is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain HO3(n)•••O5(n+1) hydrogen bond, which is affect by the water exchange around the O3-HO3 hydroxyl group.

  6. Evaluation of heavy metal removal from aqueous solution onto scolecite.

    PubMed

    Bosso, S T; Enzweiler, J

    2002-11-01

    Scolecite is a zeolite associated to basalts of the Parana Continental Igneous Province (PCIP South America). The potential of scolecite as a new material for heavy metal removal (Pb2+ Cu2+, Zn2+, Ni2+, Co2+ and Cd2+) from aqueous solutions is evaluated. The experiments were carried out by immersion of 0.5 g of sample in solutions containing the metal ions, and kept under constant agitation for 24h, at ambient temperature. The meq of cations retained per mass of scolecite was evaluated as a function of: initial concentration (5-60 mg L(-1)), pH (4-6), liquid/solid ratio (200, 1000 and 2000) and particle size. The results indicated a great affinity of scolecite for Cu2+ with a retention value of 130 microeq g(-1) at pH 6, Ci = 30 mg L(-1) and liquid/solid ratio of 200. In the same conditions, the maximum retention measured for the other ions were 64 microeq g(-1) (Zn2+), 56 microeq g(-1) (Pb2+), 31 microeq g(-1) (Ni2+), 7.8 microeq g(-1) (Co2+) and 3.2 microeq g(-1) (Cd2+). These values increase substantially when the L/S ratio is increased. The affinity of copper and lead for scolecite is discussed based on their free ionic forms (i.e., their hydrated bivalent ions) and their hydrolysis products. The remaining ions are retained as free ions.

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

    PubMed

    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.

  8. Photocatalytic decomposition of cortisone acetate in aqueous solution.

    PubMed

    Romão, Joana Sobral; Hamdy, Mohamed S; Mul, Guido; Baltrusaitis, Jonas

    2015-01-23

    The photocatalytic decomposition of cortisone 21-acetate (CA), a model compound for the commonly used steroid, cortisone, was studied. CA was photocatalytically decomposed in a slurry reactor with the initial rates between 0.11 and 0.46 mg L(-1)min(-1) at 10 mg L(-1) concentration, using the following heterogeneous photocatalysts in decreasing order of their catalytic activity: ZnO>Evonik TiO2 P25>Hombikat TiO2>WO3. Due to the lack of ZnO stability in aqueous solutions, TiO2 P25 was chosen for further experiments. The decomposition reaction was found to be pseudo-first order and the rate constant decreased as a function of increasing initial CA concentration. Changing the initial pH of the CA solution did not affect the reaction rate significantly. The decomposition reaction in the presence of the oxidizing sacrificial agent sodium persulfate showed an observed decomposition rate constant of 0.004 min(-1), lower than that obtained for TiO2 P25 (0.040 min(-1)). The highest photocatalytic degradation rate constant was obtained combining both TiO2 P25 and S2O8(2-) (0.071 min(-1)) showing a synergistic effect. No reactive intermediates were detected using LC-MS showing fast photocatalytic decomposition kinetics of CA.

  9. Correlations for Adsorption of Oxygenates onto Zeolites from Aqueous Solutions

    SciTech Connect

    Mallon, Elizabeth E.; Babineau, Ian J.; Kranz, Joshua I.; Guefrachi, Yasmine; Siepmann, J. Ilja; Bhan, Aditya; Tsapatsis, Michael

    2011-10-06

    Henry’s constants (K{sub ads}) for adsorption of C₃ polyfunctional molecules onto zeolites from aqueous solutions at 278 K were obtained and compared with the octanol–water partition coefficients, K{sub ow}, which were calculated using the prevalent ClogP group contribution method. K{sub ads} increases linearly with K{sub ow} for these adsorbates on H–ZSM-5 (MFI), FAU, BEA, and ITQ-1 (MWW). K{sub ads} values for C₂–C₆ diol adsorption at 278 K are also linearly correlated with K{sub ow} regardless of interactions in the bulk phase as measured by the solution activity coefficient. Exceptions to the correlation established between K{sub ads} and K{sub ow} are the adsorption of 1,2,ω-triols with carbon number greater than three on H–ZSM-5 and adsorption of all oxygenates studied on FER, which we postulate to be due to the effect of changing adsorption configuration with adsorbate/zeolite structure which cannot be captured by K{sub ow} alone. These results enable the prediction of separation selectivities of biomass-derived compounds on zeolite adsorbents.

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

    PubMed

    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.

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

    PubMed

    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 k_{B}T (15 wt %), 2.73 ± 0.4 k_{B}T (20 wt %), and 3.05 ± 0.2 k_{B}T (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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Computational Modeling of Actinide Ions in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Atta-Fynn, Raymond

    2014-03-01

    Unraveling the chemical behavior of actinide species is difficult owing to the complex electronic structure of these species, the fact that many of these species can occur in multiple oxidation states, and the difficulties encountered in their experimental studies. First principles dynamical modeling, although computationally costly, allows us to gain rich insights into the behavior of actinide species. In this talk, we present results of the hydration shell structure and x-ray absorption spectra of aqueous actinides in different oxidation states including U(VI), U(V), U(IV), and Cm(III) using relativistic ab initiomolecular dynamics at 300 K. We also probed the thermodynamics of hydrolysis by calculating the first acidity constant for uranium in all three oxidation states (IV, V, and VI). We predicted, for the first time, that UO2+ is a weak acid in solution with a pKa value of 8.5. This result is particularly important since no thermodynamic data are available for hydrolyzed species of U(V). In our most recent work on concentrated Cm(III) solutions, we showed that counter-ions can strengthen or weaken the solvent structure itself rather than just the water coordination number. These new results are better explained in terms of the hydrogen bond lifetimes of the solvents.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  16. UV photolysis of perfluorooctanoic acid (PFOA) in dilute aqueous solution.

    PubMed

    Giri, R R; Ozaki, H; Morigaki, T; Taniguchi, S; Takanami, R

    2011-01-01

    Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm+254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system.

  17. Corrosion of metastable iron alloys in aqueous solutions

    NASA Astrophysics Data System (ADS)

    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.

  18. Study of phosphate removal from aqueous solution by zinc oxide.

    PubMed

    Luo, Zhen; Zhu, Suiyi; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Yang, Wu

    2015-09-01

    Zinc oxide (ZnO) was synthesized and used to investigate the mechanism of phosphate removal from aqueous solution. ZnO particles were characterized by X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy before and after adsorption. Batch experiments were carried out to investigate the kinetics, isotherms, effects of initial pH and co-existing anions. The adsorption process was rapid and equilibrium was almost reached within 150 min. The adsorption kinetics were described well by a pseudo-second-order equation, and the maximum phosphate adsorption capacity was 163.4 mg/g at 298 K and pH ∼6.2±0.1. Thermodynamic analysis indicated the phosphate adsorption onto ZnO was endothermic and spontaneous. The point of zero charge of ZnO was around 8.4 according to the pH-drift method. Phosphate adsorption capacity reduced with the increasing initial solution pH values. The ligand exchange and Lewis acid-base interaction dominated the adsorption process in the lower and the higher pH range, respectively. Nitrate, sulfate and chloride ions had a negligible effect on phosphate removal, while carbonate displayed significant inhibition behavior.

  19. Structure and phase behavior of aqueous methylcellulose solutions

    NASA Astrophysics Data System (ADS)

    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.

  20. Terahertz echoes reveal the inhomogeneity of aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Shalit, Andrey; Ahmed, Saima; Savolainen, Janne; Hamm, Peter

    2017-03-01

    The structural and dynamical properties of water are known to be affected by ion solvation. However, a consistent molecular picture that describes how and to what extent ions perturb the water structure is still missing. Here we apply 2D Raman-terahertz spectroscopy to investigate the impact of monatomic cations on the relaxation dynamics of the hydrogen-bond network in aqueous salt solutions. The inherent ability of multidimensional spectroscopy to deconvolute heterogeneous relaxation dynamics is used to reveal the correlation between the inhomogeneity of the collective intermolecular hydrogen-bond modes and the viscosity of a salt solution. Specifically, we demonstrate that the relaxation time along the echo direction t1 = t2 correlates with the capability of a given cation to 'structure' water. Moreover, we provide evidence that the echo originates from the water-water modes, and not the water-cation modes, which implies that cations can structure the hydrogen-bond network to a certain extent.

  1. Dye removal from aqueous solution by magnetic alginate beads crosslinked with epichlorohydrin.

    PubMed

    Rocher, Vincent; Bee, Agnès; Siaugue, Jean-Michel; Cabuil, Valérie

    2010-06-15

    Innovative magnetic alginate beads are used to remove organic pollutants from aqueous solution under different experimental conditions. These alginate beads (EpiMAB) are prepared by an extrusion technique and crosslinked with epichlorohydrin. They contain both magnetic nanoparticles and activated carbon (AC). With the addition of magnetic properties, the beads can be easily recovered or manipulated with an external magnetic field. Their capacity to adsorb pollutants is linked to encapsulated AC and to active sites coming from both magnetic nanoparticles and alginate. The efficiency of the beads as biosorbent for the removal of dyes is assessed using methyl orange (MO) and methylene blue (MB) as model molecules. The dye uptake is found to vary with the initial concentration and the charge of the adsorbed molecule. The Langmuir equation fits well the adsorption data with maximum adsorption capacities of 0.02 mmol/g for MO and 0.7 mmol/g for MB. Kinetics experiments are performed to evaluate the equilibrium time; the pseudo-second-order kinetic model adequately describes the experimental data. The influence of the pH of the solution on adsorption is also investigated and a comparison with alginate beads crosslinked by calcium ions is made.

  2. Mid-Infrared Sensing of Organic Pollutants in Aqueous Environments

    PubMed Central

    Pejcic, Bobby; Myers, Matthew; Ross, Andrew

    2009-01-01

    The development of chemical sensors for monitoring the levels of organic pollutants in the aquatic environment has received a great deal of attention in recent decades. In particular, the mid-infrared (MIR) sensor based on attenuated total reflectance (ATR) is a promising analytical tool that has been used to detect a variety of hydrocarbon compounds (i.e., aromatics, alkyl halides, phenols, etc.) dissolved in water. It has been shown that under certain conditions the MIR-ATR sensor is capable of achieving detection limits in the 10–100 ppb concentration range. Since the infrared spectral features of every single organic molecule are unique, the sensor is highly selective, making it possible to distinguish between many different analytes simultaneously. This review paper discusses some of the parameters (i.e., membrane type, film thickness, conditioning) that dictate MIR-ATR sensor response. The performance of various chemoselective membranes which are used in the fabrication of the sensor will be evaluated. Some of the challenges associated with long-term environmental monitoring are also discussed. PMID:22454582

  3. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

    1998-01-01

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution.

  4. Process for separating and recovering an anionic dye from an aqueous solution

    DOEpatents

    Rogers, R.; Horwitz, E.P.; Bond, A.H.

    1998-01-13

    A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution. 7 figs.

  5. Protein diffusiophoresis and salt osmotic diffusion in aqueous solutions.

    PubMed

    Annunziata, Onofrio; Buzatu, Daniela; Albright, John G

    2012-10-25

    Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism is known as cross-diffusion. We have investigated cross-diffusion in a ternary protein-salt-water system. Specifically, we measured the two cross-diffusion coefficients for the lysozyme-NaCl-water system at 25 °C and pH 4.5 as a function of protein and salt concentrations by Rayleigh interferometry. One cross-diffusion coefficient characterizes salt osmotic diffusion induced by a protein concentration gradient, and is related to protein-salt thermodynamic interactions as described by the theories of Donnan membrane equilibrium and protein preferential hydration. The other cross-diffusion coefficient characterizes protein diffusiophoresis induced by a salt concentration gradient, and is described as the difference between a preferential-interaction coefficient and a transport parameter. We first relate our experimental results to the protein net charge and the thermodynamic excess of water near the protein surface. We then extract the Stefan-Maxwell diffusion coefficient describing protein-salt interactions in water. We find that the value of this coefficient is negative, contrary to the friction interpretation of Stefan-Maxwell equations. This result is explained by considering protein hydration. Finally, protein diffusiophoresis is quantitatively examined by considering electrophoretic and hydration effects on protein migration and utilized to accurately estimate lysozyme electrophoretic mobility. To our knowledge, this is the first time that protein diffusiophoresis has been experimentally characterized and a protein-salt Stefan-Maxwell diffusion coefficient reported. This work represents a significant contribution for understanding and modeling the effect of concentration gradients in protein-salt aqueous systems relevant to diffusion-based mass-transfer technologies and transport in living systems.

  6. Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions.

    PubMed

    Ijagbemi, Christianah Olakitan; Baek, Mi-Hwa; Kim, Dong-Su

    2009-07-15

    Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH(PZC) and pH(PZNPC) to be 3.4+/-0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu(2+) and Ni(2+) uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu(2+) and Ni(2+) could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive Delta G degrees values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (Delta H degrees) for Ni(2+) and Cu(2+) were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of DeltaS degrees indicate low randomness at the solid/solution interface during the uptake of both Cu(2+) and Ni(2+) by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.

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

    PubMed

    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.

  8. Raman OD stretching spectral differences between aqueous and alcoholic tetraalkylammonium chloride solutions

    NASA Astrophysics Data System (ADS)

    Hidaka, Fumi; Kanno, Hitoshi

    2003-09-01

    Raman OD stretching spectra were measured for aqueous and alcoholic R 4NCl solutions in both liquid state at room temperature and glassy state at liquid nitrogen temperature (alcohol=methanol and ethanol, R=alkyl group: methyl, ethyl and n-propyl). Comparison of the spectra indicates that enhancement of the low frequency region is more pronounced for the glassy aqueous solution than the corresponding alcohol solution. It is suggested that hydrophobic hydration plays a role in the strengthening of hydrogen bonds around an apolar solute (group) at low temperatures in aqueous solution system.

  9. Advances in preparation of modified activated carbon and its applications in the removal of chromium (VI) from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Deng, Z. L.; Liang, M. N.; Li, H. H.; Zhu, Z. J.

    2016-08-01

    The wastewater in which Cr(VI) is not fully treated has drawn environment researchers’ attention increasingly, due to its environmental pollution and harms to human health. Thus a high efficiency of modified activated carbon (MAC) to remove Cr(VI) has become one of the hot topics among environmental material research. This paper introduces the modification methods from the physical structure features and chemical properties of the activated carbon (AC) surface. At the same time, it briefly analyses the chemical characteristics of Cr(VI) in aqueous solutions, and on the basis of the aforementioned introduces the modification methods of the surface chemical characteristics of AC, such as: oxidation modification, reduction modification, loaded metal modification, and microwave modification. Combining studies on removing Cr(VI) from aqueous solutions by MAC in recent years, this paper anticipates the new trends of preparing MAC and the points in absorption research, offering some suggestions for future studies.

  10. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (hydrocyanic acid, aqueous solution). 173.195 Section 173.195 Transportation Other Regulations Relating to... (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in... 3A480, 3A480X, 3AA480, or 3A1800 metal cylinders of not over 126 kg (278 pounds) water capacity (nominal...

  11. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... (hydrocyanic acid, aqueous solution). 173.195 Section 173.195 Transportation Other Regulations Relating to... (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in... 3A480, 3A480X, 3AA480, or 3A1800 metal cylinders of not over 126 kg (278 pounds) water capacity (nominal...

  12. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (hydrocyanic acid, aqueous solution). 173.195 Section 173.195 Transportation Other Regulations Relating to... (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in... 3A480, 3A480X, 3AA480, or 3A1800 metal cylinders of not over 126 kg (278 pounds) water capacity (nominal...

  13. Distribution coefficients of vitamin B2 in hydrophilic organic solvent-aqueous salt solution systems

    NASA Astrophysics Data System (ADS)

    Korenman, Ya. I.; Mokshina, N. Ya.; Zykov, A. V.

    2010-03-01

    Distribution coefficients of vitamin B2 in hydrophilic solvent ( n-butanol, isopropanol, acetone, ethyl acetate, and their mixtures)-aqueous salt (potassium chloride, sodium fluoride, and ammonium sulfate salting-out agents) solution systems were calculated. The synergic effect and optimum proportions of components in the solvent mixture for efficient extraction of vitamin B2 from aqueous solutions were established.

  14. Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution

    DTIC Science & Technology

    1990-03-01

    CRREL *) Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution Susan Taylor and Louise Parker March...Engineering Laboratory Surface Changes in Well Casing Pipe Exposed to High Concentrations of Organics in Aqueous Solution Susan Taylor and Louise Parker March...SS304 (2000x) ..................................................................................... 14 iii Surface Changes in Well Casing Pipe Exposed to

  15. Tested Demonstrations. Color, Solubility, and Complex Ion Equilibria of Nickel (II) Species in Aqueous Solution.

    ERIC Educational Resources Information Center

    Gilbert, George L., Ed.; And Others

    1980-01-01

    Presents three different procedures in which reagents are added in a specified order to a large beaker containing an aqueous solution of nickel sulfate. Complex ions of nickel (II) are prepared by using aqueous solutions of ammonia, ethylenediamine, dimethylglyoxime, and cyanide ion. (CS)

  16. Tested Demonstrations. Color, Solubility, and Complex Ion Equilibria of Nickel (II) Species in Aqueous Solution.

    ERIC Educational Resources Information Center

    Gilbert, George L., Ed.; And Others

    1980-01-01

    Presents three different procedures in which reagents are added in a specified order to a large beaker containing an aqueous solution of nickel sulfate. Complex ions of nickel (II) are prepared by using aqueous solutions of ammonia, ethylenediamine, dimethylglyoxime, and cyanide ion. (CS)

  17. Method for distributing an aqueous solution containing a peroxygen in clay

    SciTech Connect

    Norris, R.D.; Brown, R.A.; Richards, J.C.

    1988-05-31

    A process for distributing a peroxygen through particulate matter containing clay without swelling the clay is described comprising incorporating a compound selected from the group consisting of a salt of a perborate or a persulfate anion into water to form an aqueous solution absent a colloidal agent to impart a high viscosity, and introducing the aqueous solution into the particulate matter containing clay.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Absorption and recovery of n-hexane in aqueous solutions of fluorocarbon surfactants.

    PubMed

    Xiao, Xiao; Yan, Bo; Fu, Jiamo; Xiao, Xianming

    2015-11-01

    n-Hexane is widely used in industrial production as an organic solvent. As an industrial exhaust gas, the contribution of n-hexane to air pollution and damage to human health are attracting increasing attention. In the present study, aqueous solutions of two fluorocarbon surfactants (FSN100 and FSO100) were investigated for their properties of solubilization and dynamic absorption of n-hexane, as well as their capacity for regeneration and n-hexane recovery by thermal distillation. The results show that the two fluorocarbon surfactants enhance dissolution and absorption of n-hexane, and their effectiveness is closely related to their concentrations in solution. For low concentration solutions (0.01%-0.30%), the partition coefficient decreases dramatically and the saturation capacity increases significantly with increasing concentration, but the changes for both are more modest when the concentration is over 0.30%. The FSO100 solution presents a smaller partition coefficient and a greater saturation capacity than the FSN100 solution at the same concentration, indicating a stronger solubilization for n-hexane. Thermal distillation is a feasible method to recover n-hexane from these absorption solutions, and to regenerate them. With 90sec heating at 80-85°C, the recovery of n-hexane ranges between 81% and 85%, and the regenerated absorption solution maintains its original performance during reuse. This study provides basic information on two fluorocarbon surfactants for application in the treatment of industrial n-hexane waste gases. Copyright © 2015. Published by Elsevier B.V.

  20. Adsorption of naphthalene onto sonicated talc from aqueous solutions.

    PubMed

    Sener, Savaş; Ozyilmaz, Azat

    2010-06-01

    The adsorption behavior of naphthalene onto naturally hydrophobic talc from aqueous solution was investigated in this study. The natural talc was first pretreated by sonication to improve the surface characteristics and enhance the uptake capacity by increasing the specific surface area (SSA) of talc. The naphthalene uptake of talc was found as 276 mg g(-1) and increased to 359 mg g(-1) after the sonication. Adsorption studies also showed that the adsorption of naphthalene onto the sonicated talc was not affected by changes in pH suggesting that the main driving forces for naphthalene adsorption onto talc was hydrophobic bonding rather than electrostatic force. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. Adsorption process of naphthalene onto talc followed the pseudo-second-order rate expression for different initial naphthalene concentrations. The Langmuir and Freundlich isotherm models were used to model the isotherm data for their applicability. The Freundlich isotherm best fitted for the adsorption of naphthalene onto talc.

  1. Formation and reactivity of carboxyphenyl radicals in aqueous solution

    NASA Astrophysics Data System (ADS)

    Janković, Ivana A.; Josimović, Ljubica R.; Jovanović, Slobodan V.

    1998-03-01

    Carboxyphenyl radicals were generated in aqueous solutions by reacting the solvated electron with ortho-, meta- and para-chlorobenzoate. These radicals were found to add to chlorobenzoates and abstract hydrogen atoms from a H-atom donor. It was concluded that the rate constants for the addition of carboxyphenyl radicals to chlorobenzoate depend on steric hindrance, since ortho-carboxyphenyl radical adds to 2-chlorobenzoate [ kadd=(1.0±0.2)×10 6 dm 3 mol -1 s -1] an order of magnitude slower than para-carboxyphenyl radical to 4-chlorobenzoate [ kadd=(1.0±0.2)×10 7 dm 3 mol -1 s -1]. The products of these addition reactions were detected by GC-MS. All three carboxyphenyl radical isomers abstract a H-atom from 4-methoxybenzen thiol at the same rate [ kH-aps˜1×10 9 dm 3 mol -1 s -1], i.e. the position of the carboxylate group seems not to influence the rate of the H-abstraction reaction.

  2. Adsorption of dimethylamine from aqueous solution by manganese dioxide.

    PubMed

    Yang, L; Chen, Z; Zhang, D; Liu, Y; Han, Y; Shen, J

    2011-01-01

    Removal of precursors of N-nitrosodimethylamine (NDMA), such as the most direct precursor dimethylamine (DMA), might be an effective method to control NDMA formation during practical water treatment process. Adsorption of DMA onto manganese dioxide (MnO₂) from aqueous solution has been investigated using batch experiments in this study. Results indicate that DMA adsorption is initially rapid (in the first 5 h) and the adsorption process reaches a steady state after 15 h. The adsorption isotherms are well described by the Freundlich models. The desorption shows an irreversibility of DMA adsorption onto MnO₂. The effects of temperature, pH, ionic strength, humic acid, and the presence of other secondary aliphatic amines on adsorption processes are also examined. According to the experimental results, the amount of DMA adsorbed increases with an increase of temperature from 288 to 308 K, and with a decrease of ionic strength from 1 to 10 mM. The maximum adsorption appeared at pH 7.0. However, the amount of DMA adsorbed onto MnO₂ does not show obvious difference in the presence of humic acid. According to the results, it suggests that the adsorption is primarily brought about by electrostatic interaction between DMA and MnO₂ surface.

  3. Shape transformation mechanism of silver nanorods in aqueous solution.

    PubMed

    Damm, Cornelia; Segets, Doris; Yang, Guang; Vieweg, Benito F; Spiecker, Erdmann; Peukert, Wolfgang

    2011-01-03

    The spontaneous shape transformation of silver nanorods with an initial length of several hundred nanometers towards spherical particle shapes in aqueous solution is investigated by means of scanning electron microscopy, UV-vis absorption spectroscopy, anodic stripping voltammetry, and high-resolution transmission electron microscopy (HRTEM). The consolidation of the results reveals an increase in the particle number density with time. Moreover, HRTEM image analysis along the cross section of the rods evidences the presence of fivefold twinning defects which extend along the whole rod length. According to the analytical model of Monk et al. this kind of rod structure is only thermodynamically stable if the rod length is below a critical value at a given diameter. The rods investigated in the present work do not fulfill the stability criterion as they exceed the critical length. Thus, the rods decay into smaller "nanobuns" and defective as well as defect-free spheres. A mechanism based on findings from the literature, HRTEM image analysis of former rods, transition states, and the final particle structures is proposed. The defects along the surface are seen as starting points for the dissolution of material, which is reintegrated into the solid phase by homogeneous as well as heterogeneous nucleation and growth.

  4. The Interaction of Sorbitol with Caffeine in Aqueous Solution.

    PubMed

    Tavagnacco, Letizia; Brady, John W; Cesàro, Attilio

    2013-09-01

    Molecular dynamics simulations were carried out on a system of caffeine interacting with the sugar alcohol sorbitol. The system examined had a caffeine concentration 0.083 m and a sugar concentration 1.08 m. The trajectories of all molecules in the system were collected over a period of 80 ns and analyzed to determine whether there is any tendency for sorbitol to bind to caffeine, and if so, by what mechanism. The results show that the sorbitol molecules have an affinity for the caffeine molecules and that the binding occurred by the interaction of the aliphatic hydrophobic protons of the sugar with the caffeine face. This intermolecular association via face-to-face stacking, as suggested by simulation studies, is similar to that found for sucrose and for D-glucose, which overwhelmingly exists in the pyranose ring chair form in aqueous solution, as well as for caffeine-caffeine association. The sorbitol molecules, however, exist as relatively extended chains and are, therefore, topologically quite different from the sugars sucrose and glucose. The comparison of the average conformation of sorbitol molecules bound to caffeine with that of molecules in the free state shows a substantial similarity.

  5. Paraquat adsorption onto clays and organoclays from aqueous solution.

    PubMed

    Seki, Y; Yurdakoç, K

    2005-07-01

    Clays were compared with organoclays for the sorption of paraquat from aqueous solution. Sepiolite (S), bentonite (B), and illite (I) were used as clay samples. Organoclays were prepared by the modification of the clays with nonyl- and dodecylammonium chlorides, denoted as NS, DS, NB, DB, NI, and DI, respectively. Specific surface area and pore size distribution of the samples were determined by N2 adsorption-desorption at 77 K using the BET method. X-ray powder diffraction analysis of the samples was used to determine the effects of modifying agents on the layer structure of the clays. In the adsorption experiments, C(m) values increased from 0.038 mmol/g for DS to 0.223 mmol/g for NI. Kd0.3 values ranged from 0.177 for DS to 0.843 for NI. The adsorption data indicated that illite and NI are the most effective adsorbents among these clays and organoclay samples, respectively.

  6. Structure and dynamics of aqueous solution of uranyl ions

    SciTech Connect

    Chopra, Manish; Choudhury, Niharendu

    2014-04-24

    The present work describes a molecular dynamics simulation study of structure and dynamics of aqueous solution of uranyl ions in water. Structural properties of the system in terms of radial distribution functions and dynamical characteristics as obtained through velocity autocorrelation function and mean square displacements have been analyzed. The results for radial distribution functions show the oxygen of water to form the first solvation shell at 2.4 Å around the uranium atom, whereas the hydrogen atoms of water are distributed around the uranium atom with the major peak at around 3.0 Å. Analyses of transport behaviors of ions and water through MSD indicates that the diffusion of the uranyl ion is much less as compared to that of the water molecules. It is also observed that the dynamical behavior of water molecules gets modified due to the presence of uranyl ion. The effect of increase in concentration of uranyl ions on the structure and dynamics of water molecules is also studied.

  7. Products of hexachlorocyclopentadiene (C-56) in aqueous solution

    USGS Publications Warehouse

    Chou, S.-F.J.; Griffin, R.A.; Chou, I.-Ming; Larson, R.A.

    1987-01-01

    The photodegradation and degradation products of hexachlorocyclopentadiene (C-56) in aqueous solutions were studied in the laboratory. In each case, the half-life of C-56 was less than 4 min when exposed to sunlight. At least eight degradation products were positively or tentatively identified: 2,3,4,4,5-Pentachloro-2-cyclopentenone, hexachloro-2-cyclopentenone and hexachloro-3-cyclopentenone were the primary photodegradation products, and pentachlorocis-2,4-pentadienoic acid, Z- and E-pentachlorobutadiene and tetrachlorobutyne were the secondary degradation products. Dissociation of the primary photolysis products may proceed through corresponding pentadienoic acids to form smaller molecular weight compounds such as pentachlorobutadiene isomers and tetrachlorobutyne. In addition, dimerization of 2,3,4,4,5-pentachloro-2-cyclopentenone to form higher molecular weight compounds such as hexachloroindenone may present a minor route of degradation. The results also indicate that C-56 is highly photoreactive and suggest a possible pathway for the compound's transformation in the environment when exposed to sunlight. ?? 1987.

  8. Interactions of vanadates with carbohydrates in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Ribeiro, Ana C. F.; Valente, Artur J. M.; Lobo, Victor M. M.; Azevedo, Eduarda F. G.; Amado, Ana M.; da Costa, A. M. Amorim; Ramos, M. Luísa; Burrows, H. D.

    2004-10-01

    The interaction between the vanadate ion (VO 3-, i.e. vanadium (V)) and the carbohydrates sucrose, glucose and fructose has been studied in aqueous solutions (pH ≈6, 298.15 K) using measurements of diffusion coefficients, electrical conductivity, Raman and multinuclear NMR spectroscopy. With sucrose and glucose, indications of hydrolysis of the anion in the absence of the sugars came from a decrease in the diffusion coefficient with increasing concentration. Significant effects on the diffusion coefficients were observed in the presence of sucrose and glucose, suggesting interactions between the carbohydrates and vanadate ion. Support for this came from electrical conductivity measurements, where there were indications of formation of oligomeric species. These were found to depend on the carbohydrate used: confirmation of oligomer formation came from Raman spectroscopy, where it was possible to identify these species, and see their dependence on the particular carbohydrate used. Information on the interactions between the carbohydrates glucose or sucrose and vanadate came from 51V and 1H NMR spectroscopy, where the dominant species appeared to be a 2:2 complex with glucose, possessing trigonal bipyramidal centres, whereas with sucrose it is suggested that octahedral species are formed. Studies with fructose were complicated by competing oxidation of this carbohydrate and reduction of vanadium (V).

  9. Formation and reactivity of vinylperoxyl radicals in aqueous solutions

    SciTech Connect

    Khaikin, G.I.; Neta, P.

    1995-03-30

    Vinyl, carboxyvinyl and dicarboxyvinyl radicals were produced in irradiated aqueous solutions from acetylene and acetylenecarboxylic and acetylenedicarboxylic acid by addition of H atom to the triple bond or by reaction with e{sub aq}{sup -}, followed by protonation. Vinyl and phenylvinyl radicals were produced by reductive dehalogenation of vinyl bromide and {beta}-bromostyrene with e{sub aq}{sup -}. All these vinyl radicals react rapidly with oxygen to produce the corresponding vinylperoxyl radicals. Vinylperoxyl radicals exhibit optical absorptions in the UV ({lambda}{sub max} 250-290 nm) and in the visible range. The peaks in the visible range were at 440 nm for unsubstituted vinylperoxyl radical, between 480 and 520 nm for carboxylated vinylperoxyl, depending on pH and number of carboxyl groups, and at 540 and 690 nm for (2-phenylvinyl)peroxyl. These vinylperoxyl radicals oxidize organic reductants such as 2,2`azinobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, ascorbate, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) with rate constants between 4 x 10{sup 5} and 2 x 10{sup 9} L mol{sup -1} s{sup -1}, depending on the radical and the reductant. Vinylperoxyl radicals are more reactive than similarly substituted alkylperoxyl. 20 refs., 5 figs., 1 tab.

  10. Water concentration dependent photochemistry of ketoprofen in aqueous solutions.

    PubMed

    Li, Ming-De; Du, Yong; Chuang, Yung Ping; Xue, Jiadan; Phillips, David Lee

    2010-05-14

    Ketoprofen is an important photosensitive drug molecule that has received much attention for the study of its photochemistry in different solvents. In this paper, nanosecond time-resolved resonance Raman spectroscopy was utilized to investigate the photochemistry of ketoprofen in aqueous solutions with varying water concentrations. The rate constants and reaction mechanism of ketoprofen are strongly dependent on the concentration of the solvent. In neat acetonitrile and solvents with low concentrations of water (like water-acetonitrile or= 9 : 1, v/v), the triplet state ketoprofen is observed first and then undergoes a prompt decarboxylation process to form a triplet protonated biradical carbanion species. For solvents with moderate higher water concentrations (such as between 50% and 90% water by volume), the hydrogen abstraction and decarboxylation processes are two competitive pathways with different rate constants. The triplet state of ketoprofen will simultaneously produce a ketyl radical species and a triplet protonated biradical carbanion species with the amount of each species dependent on the water concentration.

  11. Destruction of amphetamine in aqueous solution using gamma irradiation

    NASA Astrophysics Data System (ADS)

    Alkhuraiji, Turki S.; Ajlouni, Abdul-Wali

    2017-10-01

    Amphetamine-type stimulants are among the most prevalent and widespread commonly abused drugs. Amphetamine and its derivatives were detected in aquatic environment. This study aimed to demonstrate experimentally the ability of γ-irradiation combined with persulfate anions (S2O82-) to degrade and mineralize the amphetamine in aqueous solution. An initial amphetamine concentration of 125 μM in distilled water was completely degraded by a γ-ray dose of 2.8 kGy. Generation of the sulfate radical (SO4•-) from the fast reaction of added S2O82- with hydrated electrons (eaq-; keaq-/S2O82- = 1.1×1010 M-1 s-1) improved the efficiency of amphetamine degradation and mineralization. A γ-ray dose of 0.667 and 0.350 kGy in the absence and presence of S2O82- anions degraded 90% of the amphetamine, respectively. For γ-ray/free O2 and γ-ray/S2O82- systems, 11.5 and 7 kGy was required for 50% amphetamine mineralization, respectively. Addition of HCO3- anions lowered the amphetamine degradation yield, whereas N2 gas, SO42-, and Cl- anions had a negligible effect.

  12. Observation of electron-transfer-mediated decay in aqueous solution

    NASA Astrophysics Data System (ADS)

    Unger, Isaak; Seidel, Robert; Thürmer, Stephan; Pohl, Marvin N.; Aziz, Emad F.; Cederbaum, Lorenz S.; Muchová, Eva; Slavíček, Petr; Winter, Bernd; Kryzhevoi, Nikolai V.

    2017-07-01

    Photoionization is at the heart of X-ray photoelectron spectroscopy (XPS), which gives access to important information on a sample's local chemical environment. Local and non-local electronic decay after photoionization—in which the refilling of core holes results in electron emission from either the initially ionized species or a neighbour, respectively—have been well studied. However, electron-transfer-mediated decay (ETMD), which involves the refilling of a core hole by an electron from a neighbouring species, has not yet been observed in condensed phase. Here we report the experimental observation of ETMD in an aqueous LiCl solution by detecting characteristic secondary low-energy electrons using liquid-microjet soft XPS. Experimental results are interpreted using molecular dynamics and high-level ab initio calculations. We show that both solvent molecules and counterions participate in the ETMD processes, and different ion associations have distinctive spectral fingerprints. Furthermore, ETMD spectra are sensitive to coordination numbers, ion-solvent distances and solvent arrangement.

  13. Tertiary structure of conotoxin GIIIA in aqueous solution.

    PubMed

    Lancelin, J M; Kohda, D; Tate, S; Yanagawa, Y; Abe, T; Satake, M; Inagaki, F

    1991-07-16

    The three-dimensional structure of conotoxin GIIIA, an important constituent of the venom from the marine hunting snail Conus geographus L., was determined in aqueous solution by two-dimensional proton nuclear magnetic resonance and simulated annealing based methods. On the basis of 162 assigned nuclear Overhauser effect (NOE) connectivities obtained at the medium field strength frequency of 400 MHz, 74 final distance constraints of sequential and tertiary ones were derived and used together with 18 torsion angle (phi, chi 1) constraints and 9 distance constraints derived from disulfide bridges. A total of 32 converged structures were obtained from 200 runs of calculations. The atomic root-mean-square (RMS) difference about the mean coordinate positions (excluding the terminal residues 1 and 22) is 0.8 A for backbone atoms (N, C alpha, C). Conotoxin GIIIA is characterized by a particular folding of the 22 amino acid peptidic chain, which is stabilized by three disulfide bridges arranged in cage at the center of a discoidal structure of approximately 20-A diameter. The seven cationic side chains of lysine and arginine residues project radially into the solvent and form potential sites of interaction with the skeletal muscle sodium channel for which the toxin is a strong inhibitor. The present results provide a molecular basis to elucidate the remarkable physiological properties of this neurotoxin.

  14. Catalysis by metallic nanoparticles in aqueous solution: model reactions.

    PubMed

    Hervés, Pablo; Pérez-Lorenzo, Moisés; Liz-Marzán, Luis M; Dzubiella, Joachim; Lu, Yan; Ballauff, Matthias

    2012-09-07

    Catalysis by metallic nanoparticles is certainly among the most intensely studied problems in modern nanoscience. However, reliable tests for catalytic performance of such nanoparticles are often poorly defined, which makes comparison and benchmarking rather difficult. We tackle in this tutorial review a subset of well-studied reactions that take place in aqueous phase and for which a comprehensive kinetic analysis is available. Two of these catalytic model reactions are under consideration here, namely the reduction of (i) p-nitrophenol and (ii) hexacyanoferrate (iii), both by borohydride ions. Both reactions take place at the surface of noble metal nanoparticles at room temperature and can be accurately monitored by UV-vis spectroscopy. Moreover, the total surface area of the nanoparticles in solution can be known with high precision and thus can be directly used for the kinetic analysis. Hence, these model reactions represent cases of heterogeneous catalysis that can be modelled with the accuracy typically available for homogeneous catalysis. Both model reactions allow us to discuss a number of important concepts and questions, namely the dependence of catalytic activity on the size of the nanoparticles, electrochemistry of nanoparticles, surface restructuring, the use of carrier systems and the role of diffusion control.

  15. Oil-induced aggregation of block copolymer in aqueous solution.

    PubMed

    Ma, Jun-He; Wang, Yun; Guo, Chen; Liu, Hui-zhou; Tang, Ya-lin; Bahadur, Pratap

    2007-09-27

    The oil-induced aggregation behavior of PEO-PPO-PEO Pluronic P84 [(EO)19(PO)39(EO)19] in aqueous solutions has been systematically investigated by 1H NMR spectroscopy, freeze-fracture transmission electron microscopy (FF-TEM), and dynamic light scattering (DLS). The critical micellization temperature (CMT) for P84 in the presence of oils decreases with increasing oil concentration. The effectiveness of various oils in decreasing the CMT of block copolymer follows the order m-xylene (C(8)H(10)) > toluene (C(7)H(8)) > benzene (C(6)H(6)) > n-octane (C(8)H(18)) > n-hexane (C(6)H(14)) approximately cyclohexane (C(6)H(12)). It was found that the amount of anhydrous PO methyl groups increases whereas the amount of hydrated PO methyl groups decreases upon the addition of oils. At low oil concentration, the oil molecules are entrapped by the micellar core, but as the oil concentration increases above a certain value, the micellar core swells significantly as a result of the penetrated oil molecules, and much larger aggregates are formed. Intermolecular rotating-frame nuclear Overhauser effect (ROE) measurements between P84 and benzene were performed at 10 and 40 degrees C. The specific interaction between benzene and the methyl groups of PPO was determined, and it was observed that the interaction site remained unchanged as the temperature was increased.

  16. Photo-induced reduction of flavin mononucleotide in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Song, S.-H.; Dick, B.; Penzkofer, A.

    2007-01-01

    The photo-induced reduction of flavin mononucleotide (FMN) in aqueous solutions is studied by absorption spectra measurement under aerobic and anaerobic conditions. Samples without exogenous reducing agent and with the exogenous reducing agents ethylene-diamine-tetraacetic acid (EDTA) and dithiothreitol (DTT) are investigated. Under anaerobic conditions the photo-induced reduction with and without reducing agents is irreversible. Under aerobic conditions the photo-reduction without added reducing agent is small compared to the photo-degradation, and the photo-reduction of FMN by the reducing agents is reversible (re-oxidation in the dark). During photo-excitation of FMN the dissolved oxygen is consumed by singlet oxygen formation and subsequent chemical reaction. After light switch-off slow re-oxidation (slow absorption recovery) occurs due to air in-diffusion from surface. EDTA degradation by FMN excitation leads to oxygen scavenging. The quantum efficiencies of photo-reduction under aerobic and anaerobic conditions are determined. The re-oxidation of reduced FMN under aerobic conditions and due to air injection is investigated.

  17. Hemibonding of hydroxyl radical and halide anion in aqueous solution.

    PubMed

    Yamaguchi, Makoto

    2011-12-29

    Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-ωPBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of σ-σ* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants.

  18. Nonlinear optical properties of sodium copper chlorophyllin in aqueous solution.

    PubMed

    Li, Jiangting; Peng, Yufeng; Han, Xueyun; Guo, Shaoshuai; Liang, Kunning; Zhang, Minggao

    2017-06-16

    Sodium copper chlorophyllin (SCC), as one of the derivatives of chlorophyll - with its inherent green features; good stability for heat, light, acids and alkalies; unique antimicrobial capability; and particular deodori zation performance - is widely applied in some fields such as the food industry, medicine and health care, daily cosmetic industry etc. SCC, as one of the metal porphyrins, has attracted much attention because of its unique electronic band structure and photon conversion performance. To promote the application of SCC in materials science; energy research and photonics, such as fast optical communications; and its use in nonlinear optical materials, solar photovoltaic cells, all-optical switches, optical limiters and saturable absorbers, great efforts should be dedicated to studying its nonlinear optical (NLO) properties. In this study, the absorption spectra and NLO properties of SCC in aqueous solution at different concentrations were measured. The Z-scan technique was used to determine NLO properties. The results indicated that the absorption spectra of SCC exhibit 2 characteristic absorption peaks located at the wavelengths 405 and 630 nm, and the values of the peaks increase with increasing SCC concentration. The results also showed that SCC exhibits reverse saturation absorption and negative nonlinear refraction (self-defocusing). It can be seen that SCC has good optical nonlinearity which will be convenient for applications in materials science, energy research and photonics.

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

    PubMed

    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 < ε(*) , however, ε dependence of their overall conformation is significantly differentiated from each other. PγDLGA tends to aggregate intramolecularly and/or intermolecularly with decreasing ε, but PγLGA still behaves as expanded random-coil. It is speculated that spatial arrangement of adjacent carboxyl groups along the backbone chain essentially affects the overall conformation of PγGA in acidic media.

  20. Electrochemical degradation of amaranth aqueous solution on ACF.

    PubMed

    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.

  1. Nitroimidazoles adsorption on activated carbon cloth from aqueous solution.

    PubMed

    Ocampo-Pérez, R; Orellana-Garcia, F; Sánchez-Polo, M; Rivera-Utrilla, J; Velo-Gala, I; López-Ramón, M V; Alvarez-Merino, M A

    2013-07-01

    The objective of this study was to analyze the equilibrium and adsorption kinetics of nitroimidazoles on activated carbon cloth (ACC), determining the main interactions responsible for the adsorption process and the diffusion mechanism of these compounds on this material. The influence of the different operational variables, such as ionic strength, pH, temperature, and type of water (ultrapure, surface, and waste), was also studied. The results obtained show that the ACC has a high capacity to adsorb nitroimidazoles in aqueous solution. Electrostatic interactions play an important role at pH<3, which favors the repulsive forces between dimetridazole or metronidazole and the ACC surface. The formation of hydrogen bonds and dispersive interactions play the predominant role at higher pH values. Modifications of the ACC with NH3, K2S2O8, and O3 demonstrated that its surface chemistry plays a predominant role in nitroimidazole adsorption on this material. The adsorption capacity of ACC is considerably high in surface waters and reduced in urban wastewater, due to the levels of alkalinity and dissolved organic matter present in the different types of water. Finally, the results of applying kinetic models revealed that the global adsorption rate of dimetridazole and metronidazole is controlled by intraparticle diffusion.

  2. Spreading of aqueous SDS solutions over nitrocellulose membranes.

    PubMed

    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.

  3. Glycine phases formed from frozen aqueous solutions: Revisited

    NASA Astrophysics Data System (ADS)

    Surovtsev, N. V.; Adichtchev, S. V.; Malinovsky, V. K.; Ogienko, A. G.; Drebushchak, V. A.; Manakov, A. Yu.; Ancharov, A. I.; Yunoshev, A. S.; Boldyreva, E. V.

    2012-08-01

    Glycine phases formed when aqueous solutions were frozen and subsequently heated under different conditions were studied by Raman scattering, x-ray diffraction, and differential scanning calorimetry (DSC) techniques. Crystallization of ice Ih was observed in all the cases. On cooling at the rates of 0.5 K/min and 5 K/min, glassy glycine was formed as an intermediate phase which lived about 1 min or less only, and then transformed into β-polymorph of glycine. Quench cooling of glycine solutions (15% w/w) in liquid nitrogen resulted in the formation of a mixture of crystalline water ice Ih and a glassy glycine, which could be preserved at cryogenic temperatures (80 K) for an indefinitely long time. This mixture remained also quite stable for some time after heating above the cryogenic temperature. Subsequent heating under various conditions resulted in the transformation of the glycine glass into an unknown crystalline phase (glycine "X-phase") at 209-216 K, which at 218-226 K transformed into β-polymorph of glycine. The "X-phase" was characterized by Raman spectroscopy; it could be obtained in noticeable amounts using a special preparation technique and tentatively characterized by x-ray powder diffraction (P2, a = 6.648 Å, b = 25.867 Å, c = 5.610 Å, β = 113.12°); the formation of "X-phase" from the glycine glassy phase and its transformation into β-polymorph were followed by DSC. Raman scattering technique with its power for unambiguous identification of the crystalline and glassy polymorphs without limitation on the crystallite size helped us to follow the phase transformations during quenching, heating, and annealing. The experimental findings are considered in relation to the problem of control of glycine polymorphism on crystallization.

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

    PubMed

    Elouear, Z; Bouzid, J; Boujelben, N; Feki, M; Jamoussi, F; Montiel, A

    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(2)); and, (b) qualified and quantified the interaction of Pb(2+), Cd(2+), Cu(2+) and Zn(2+) with these sorbents through batch experiments. Initial uptake of these metal ions increases with time up to 1h for (PR) and 2h for (APR), after then, it reaches equilibrium. The maximum sorption obtained for (PR) and (APR) is between pH 2 and 3 for Pb(2+) and 4 and 6 for Cd(2+), Cu(2+) and Zn(2+). The effect of temperature has been carried out at 10, 20 and 40 degrees 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 (DeltaH degrees), free energy (DeltaG degrees) and change in entropy (DeltaS degrees) were calculated. They show that sorption of Pb(2+), Cd(2+), Cu(2+) and Zn(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.

  5. Pulse radiolysis of butyl acrylate in aqueous solution

    NASA Astrophysics Data System (ADS)

    Kujawa, P.; Mohid, N.; Zaman, K.; Manshol, W.; Ulanski, P.; Rosiak, J. M.

    1998-10-01

    The pulse radiolysis of n-butyl acrylate (nBA) in aqueous solution was studied. The rate constant of the reaction of nBA with hydroxyl radicals was calculated as 1.5×10 10 dm 3 mol -1 s -1. The absorption spectrum of the OH ·-nBA adduct appeared to have a broad maximum at 300 nm. This spectrum was attributed to the α-carbon centred radicals. It decayed with the first-order rate constant k=1.5×10 4 s -1 (pH 10.8). The rate constant of the nBA reaction with hydrated electrons was determined as k=1.6×10 10 dm 3 mol -1 s -1. The spectrum of H ·-nBA adduct was similar to that recorded for OH · adduct. It decayed with first-order kinetics at k=1.0×10 4 s -1. Spectra of the electron adduct were characterised by the band with a maximum at 285 nm (pH 10.0) or at 280 nm (pH 4.0) with ɛ=10 500 dm 3 mol -1 cm -1. In acidic solution, radical anion formed upon addition of hydrated electrons to the nBA molecule, undergoes fast, reversible protonation. The decay of the reversibly protonated electron adduct was a second-order process at k=2.5×10 9 dm 3 mol -1 s -1. This reaction took place at the carbonyl oxygen. Slow, irreversible protonation of the electron adduct at high pH takes place at the β-carbon atom at k=2.9×10 4 s -1.

  6. Analysis of excess Gibbs energy of electrolyte solutions: a new model for aqueous solutions.

    PubMed

    Dougherty, Ralph C; Howard, Louis N

    2003-09-01

    This paper presents an analysis of the excess Gibbs free energy of aqueous electrolytes. The analysis of experimental data leads to the conclusion that the equilibrium state for dilute univalent electrolytes in water involves an intercalation of water and ionic liquid crystal domains. Excess free energy of the solution is determined by the Madelung energy of hydrated ion-pair liquid crystals, and the energy associated with a shift in the structural equilibrium of water. The data that point to such a model include: molecular orbital-molecular dynamics applied to electrolyte water systems; Raman spectra; infrared spectra; magnetic resonance spectra of ions; the apparent density of water; and the excess free energy of electrolytes in aqueous solutions. Molecular orbital-molecular dynamics calculations of relatively large water clusters containing a molecule of sodium iodide show that the solvent separated ion pair exists in a substantial potential well compared to other possible structures. Raman spectra of univalent electrolyte solutions as a function of concentration can be quantitatively modeled using only the spectra of pure water and electrolyte solution at the concentration of the solvent separated ion pair. The other observations are consistent with the structures proposed from the Raman spectral study. The new model provides a satisfactory account of the fact that the excess free energy of dilute (<0.2 mol/l) solutions is generally more negative than anticipated on the basis of Debye-Hückel theory, and that the equilibrium evidence points to the same functional behavior at very low concentrations as is seen at 0.05 mol/l. We present a testable hypothesis that the excess free energy, and other thermodynamic properties of the solutions do not follow the Debye-Hückel limiting law. The tests of this hypothesis must involve only equilibrium measurements at concentrations between 0.05 and 0.0005 mol/l. This hypothesis concerning the structure of aqueous

  7. Oxidative degradation of alternative gasoline oxygenates in aqueous solution by ultrasonic irradiation: mechanistic study.

    PubMed

    Kim, Duk Kyung; O'Shea, Kevin E; Cooper, William J

    2012-07-15

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

  8. Removal of uranium from aqueous solution by a low cost and high-efficient adsorbent

    NASA Astrophysics Data System (ADS)

    Liu, Yun-Hai; Wang, You-Qun; Zhang, Zhi-Bin; Cao, Xiao-Hong; Nie, Wen-Bin; Li, Qin; Hua, Rong

    2013-05-01

    In this study, a low-cost and high-efficient carbonaceous adsorbent (HTC-COOH) with carboxylic groups was developed for U(VI) removal from aqueous solution compared with the pristine hydrothermal carbon (HTC). The structure and chemical properties of resultant adsorbents were characterized by Scanning electron microscope (SEM), N2 adsorption-desorption, Fourier transform-infrared spectra (FT-IR) and acid-base titration. The key factors (solution pH, contact time, initial U(VI) concentrations and temperature) affected the adsorption of U(VI) on adsorbents were investigated using batch experiments. The adsorption of U(VI) on HTC and HTC-COOH was pH-dependent, and increased with temperature and initial ion concentration. The adsorption equilibrium of U(VI) on adsorbents was well defined by the Langmuir isothermal equation, and the monolayer adsorption capacity of HTC-COOH was found to be 205.8 mg/g. The kinetics of adsorption was very in accordance with the pseudo-second-order rate model. The adsorption processes of U(VI) on HTC and HTC-COOH were endothermic and spontaneous in nature according to the thermodynamics of adsorption. Furthermore, HTC-COOH could selectively adsorption of U(VI) in aqueous solution containing co-existing ions (Mg2+, Co2+, Ni2+, Zn2+ and Mn2+). From the results of the experiments, it is found that the HTC-COOH is a potential adsorbent for effective removal of U(VI) from polluted water.

  9. Remediation of methyl iodide in aqueous solution and soils amended with thiourea.

    PubMed

    Zheng, Wei; Papiernik, Sharon K; Guo, Mingxin; Yates, Scott R

    2004-02-15

    Methyl iodide (MeI) is considered a very promising fumigant alternative to methyl bromide (MeBr) for controlling soil-borne pests. Because atmospheric emission of highly volatile fumigants contributes to air pollution, feasible strategies to reduce emissions are urgently needed. In this study, thiourea (a nitrification inhibitor) was shown to accelerate the degradation of MeI in soil and water. In aqueous solution, the reaction between MeI and thiourea was independent of pH, although the rate of MeI hydrolysis increased in alkaline solution. Substantial increases in the rate of MeI dissipation were observed in thiourea-amended soils. Transformation of MeI by thiourea in aqueous solution was by a single chemical reaction process, while MeI degradation in thiourea-amended soil apparently involved a catalytic mechanism. The electron delocalization between the thiourea molecule and the surfaces of soil particles is energetically favorable and would increase the nucleophilic reactivity of the thiono group toward MeI, resulting in an enhancement of the dissipation rate. The soil half-life for MeI was reduced from >300 h for unamended soils to only a few hours in soil or sand amended with thiourea at a 2:1 molar ratio (thiourea:MeI). The MeI transformation rate in thiourea-amended soil increased with increasing soil temperature and decreasing soil moisture. Therefore, spraying thiourea on the soil surface to form a "reactive surface barrier" may be an effective and innovative strategy for controlling fumigant emissions to the atmosphere and for improving environmental protection.

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

    PubMed

    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.

  11. Reduction remediation of hexavalent chromium by bacterial flora in Cr(VI) aqueous solution.

    PubMed

    Wang, Qian; Xu, Xinhua; Zhao, Fanglin; Liu, Zhihao; Xu, Jinan

    2010-01-01

    Chromium(VI) is a priority pollutant in soils and wastewaters and reduction of Cr(VI) to Cr(III) is a solution to this problem. In this study a low-cost method was proposed to adapt indigenous bacteria and use them to reduce Cr(VI) in solutions. The experiment results show that Cr(VI) could be efficiently reduced by indigenous bacteria under anaerobic and pH-unadjusted conditions. After about 24 h the concentration of Cr(VI) could be reduced from 21.74 mg/L to below 0.5 mg/L. The observed Cr(VI) reduction rates were affected by temperature and pH. Cr(VI) in aqueous solutions could be reduced to Cr(III) completely and partly be incepted by the organisms. Cr(VI) reduction was enzyme-mediated. It was not an energy-conserving process but a detoxification reaction. This method could be used in an anaerobic reactor to treat low-concentration wastewater or industrial water as the last step.

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

    PubMed

    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.

  13. Graphene oxide/chitin nanofibril composite foams as column adsorbents for aqueous pollutants.

    PubMed

    Ma, Zhongshi; Liu, Dagang; Zhu, Yi; Li, Zehui; Li, Zhenxuan; Tian, Huafeng; Liu, Haiqing

    2016-06-25

    A novel graphene oxide/chitin nanofibrils (GO-CNF) composite foam as a column adsorbent was prepared for aqueous contaminant disposal. The structures, morphologies and properties of composite foams supported by nanofibrils were characterized. As a special case, the adsorption of methylene blue (MB) on GO-CNF was investigated regarding the static adsorption and column adsorption-desorption tests. Results from equilibrium adsorption isotherms indicated that the adsorption behavior was well-fitted to Langmuir model. The composite foams reinforced by CNF were dimensionally stable during the column adsorption process and could be reused after elution. The removal efficiency of MB was still nearly 90% after 3 cycles. Furthermore, other inorganic or organic pollutants adsorbed by composite foams were also explored. Therefore, this novel composite foam with remarkable properties such as dimensional stability, universal adsorbent for cationic pollutants, high adsorption capacity, and ease of regeneration was a desirable adsorbent in the future practical application of water pollutant treatment.

  14. Nucleate pool boiling heat transfer in aqueous surfactant solutions

    NASA Astrophysics Data System (ADS)

    Wasekar, Vivek Mahadeorao

    Saturated, nucleate pool boiling in aqueous surfactant solutions is investigated experimentally. Also, the role of Marangoni convection, driven both by temperature and surfactant concentration gradients at the vapor-liquid interface of a nucleating bubble is computationally explored. Experimental measurements of dynamic and equilibrium sigma using the maximum bubble pressure method indicate dynamic sigma to be higher than the corresponding equilibrium value, both at room and elevated temperatures. Also, nonionic surfactants (Triton X-100, Triton X-305) show larger sigma depression than anionic surfactants (SDS, SLES), and a normalized representation of their dynamic adsorption isotherms is shown to be helpful in generalizing the surfactant effectiveness to reduce surface tension. The dynamic sigma has a primary role in the modification of bubble dynamics and associated heat transfer, and is dictated by the adsorption kinetics of the surfactant molecules at boiling temperatures. In general, an enhancement in heat transfer is observed, which is characterized by an early incipience and an optimum boiling performance at or around the critical micelle concentration of the surfactant. The optimum performances, typically in the fully developed boiling regime ( q''w > 100 kW/m2), show a reverse trend with respect to surfactant molecular weights M, i.e., higher molecular weight additives promote lower enhancement. Normalized boiling performance using the respective solution's dynamic sigma correlates heat transfer coefficient by M-0.5 for anionics and M 0 for nonionics. This has been shown to be brought about by the surfactant concentration and its interfacial activity in a concentration sublayer around the growing vapor bubble, which governs the bubble growth behavior through the mechanism of dynamic sigma. The ionic nature of the surfactant influences the thickness and molecular makeup of the enveloping sublayer, thereby affecting the bubble dynamics and boiling heat

  15. Characterization of metal removal by os sepiae of Sepiella maindroni Rochebrune from aqueous solutions.

    PubMed

    Li, You-Zhi; Pan, Hong; Xu, Jian; Fan, Xian-Wei; Song, Xian-Chong; Zhang, Qian; Xu, Jin; Liu, Yang

    2010-07-15

    To develop low cost metal adsorbents with less secondary pollution, metal adsorption from the aqueous solutions by the raw os sepiae (ROS) and alkali (NaOH)-pretreated OS (APOS) of the cuttlefish (Sepiella maindroni Rochebrune) was characterized. The capacities of adsorption of ROS and APOS were estimated to be 299.26 mg Cu g(-1) and 299.58 mg Cu g(-1), respectively. Metal adsorption by OS was significantly improved by appropriately increasing initial pH in the solution but hardly affected by temperature change within a wide range of 15-45 degrees C. Cu adsorption of both ROS and APOS was well described neither by Langmuir model nor by Freundlich model. Metal adsorption by OS fell in the order of Fe > Cu approximately = Cd > Zn in the solution with mixed metals, but followed the sequence of Cd > Cu > Fe approximately = Zn in the solutions respectively, with a single metal of Fe, Cu, Cd and Zn. The changes in Ca amounts in OS and solutions in adsorption strongly correlated with removal efficiencies of the metals. Obvious shifts of stretching bands of numbers of groups in OS after and before adsorption and the pretreatment occurred. It was concluded: (1) that metal adsorption by OS involves ion exchange, which occurred mainly between Ca rather than K and Na that OS itself contains and metals that were added in the solution, (2) that metal adsorption-promoting effects by NaOH pretreatment likely involve deprotonation of surface groups in OS, exposure of more functional groups, and increase in specific surface areas and (3) that related mechanisms for adsorption also likely include surface complexation, electrostatic adsorption and even micro-deposition. The results also indicated that OS is a very promising absorbent for metal removal from electroplating wastewater. 2010 Elsevier B.V. All rights reserved.

  16. Adsorption of quinolone, tetracycline, and penicillin antibiotics from aqueous solution using activated carbons: Review.

    PubMed

    Ahmed, Muthanna J

    2017-03-01

    Antibiotics, an important type of pharmaceutical pollutant, have attracted many researchers to the study of their removal from aqueous solutions. Activated carbon (AC) has been widely used as highly effective adsorbent for antibiotics because of its large specific surface area, high porosity, and favorable pore size distribution. In this article, the adsorption performance of AC towards three major types of antibiotics such as tetracyclines, quinolones, and penicillins were reviewed. According to collected data, maximum adsorption capacities of 1340.8, 638.6, and 570.4mg/g were reported for tetracyclines, quinolones, and penicillins, respectively. The values of 1/n for Freundlich isotherm were less than unity, suggesting that the adsorption was nonlinear and favorable. Adsorption kinetics followed closely the pseudo-second-order model and analysis using the Weber-Morris model revealed that the intra-particle diffusion was not the only rate controlling step. AC adsorption demonstrated superior performance for all selected drugs, thus being efficient technology for treatment of these pollutants.

  17. Biosorption of formic and acetic acids from aqueous solution using activated carbon from shea butter seed shells

    NASA Astrophysics Data System (ADS)

    Adekola, Folahan A.; Oba, Ismaila A.

    2016-10-01

    The efficiency of prepared activated carbon from shea butter seed shells (SB-AC) for the adsorption of formic acid (FA) and acetic acid (AA) from aqueous solution was investigated. The effect of optimization parameters including initial concentration, agitation time, adsorbent dosage and temperature of adsorbate solution on the sorption capacity were studied. The SB-AC was characterized for the following parameters: bulk density, moisture content, ash content, pH, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The optimal conditions for the adsorption were established and the adsorption data for AA fitted Dubinin-Radushkevich (D-R) isotherm well, whereas FA followed Langmuir isotherm. The kinetic data were examined. It was found that pseudo-second-order kinetic model was found to adequately explain the sorption kinetic of AA and FA from aqueous solution. It was again found that intraparticle diffusion was found to explain the adsorption mechanism. Adsorption thermodynamic parameters were estimated and the negative values of ∆G showed that the adsorption process was feasible and spontaneous in nature, while the negative values of ∆H indicate that the adsorption process was exothermic. It is therefore established that SB-AC has good potential for the removal of AA and FA from aqueous solution. Hence, it should find application in the regular treatment of polluted water in aquaculture and fish breeding system.

  18. Methylene blue adsorption from aqueous solution by activated carbon: effect of acidic and alkaline solution treatments.

    PubMed

    Ijagbemi, Christianah O; Chun, Ji I; Han, Da H; Cho, Hye Y; O, Se J; Kim, Dong S

    2010-01-01

    The removal of Methylene Blue (MB) from aqueous solution using activated carbon (AC) has been investigated. Adsorption experiments were conducted and the maximum adsorption capacity was determined. The effect of experimental parameters such as pH, dye concentration and temperature were studied on the adsorption process. Equilibrium data were mathematically modeled using the Langmuir and Freundlich adsorption models to describe the equilibrium isotherms at different dye concentrations and temperature. Parameters of best-fit model were calculated and discussed. To understand the mechanism of adsorption, kinetic models were employed to follow the adsorption processes; the pseudo-first-order best described the adsorption of MB onto AC. It was found that pH plays a major role in the adsorption process; adsorption capacity was influenced by the physical and surface chemical properties of carbon and the pH of the solution. 99.0% MB removal was achieved at equilibrium.

  19. Sonochemical synthesis of Au-TiO2 nanoparticles for the sonophotocatalytic degradation of organic pollutants in aqueous environment.

    PubMed

    Anandan, Sambandam; Ashokkumar, Muthupandian

    2009-03-01

    Au-TiO2 photocatalysts were sonochemically prepared by three different procedures and their photocatalytic and sonophotocatalytic efficiencies were evaluated by studying the degradation of a representative organic pollutant, nonylphenol ethoxylate (NPE) surfactant in aqueous solutions. In the first procedure, Au-TiO2 nanoparticles were prepared by depositing sonochemically synthesized gold nanoparticles on Degussa P25 TiO2 by stirring in the absence of an ultrasonic field. In the second procedure, Au nanoparticles were sonochemically synthesized and simultaneously deposited on Degussa P25 TiO2 particles. In the third procedure, Au-TiO2 nanoparticles were sonochemically synthesized by the simultaneous irradiation of an aqueous solution containing AuCl4- and titanium tetraisopropoxide. The prepared nanoparticles were characterized by UV-vis spectroscopy and transmission electron microscopy (TEM). The catalytic activities of these nanomaterials were compared for the degradation of a polydisperse nonylphenol ethoxylate, Teric GN9 by photocatalysis and sonophotocatalysis under visible light/high frequency ultrasound irradiation. The catalysts did not show a synergetic effect towards the sonophotocatalytic degradation of Teric GN9. This might be due to the interference of the degradation products generated during the simultaneous irradiation by light and ultrasound.

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

    SciTech Connect

    Choi, Jun-Ho; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng; Kim, Heejae; Kim, Seongheun

    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