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Water equilibrium

Larissa Braun, Martin Uhlig, Regine von Klitzing, Richard A Campbell
This review addresses the advances made with specular neutron reflectometry in studies of aqueous mixtures of polymers and surfactants at fluid interfaces during the last decade (or so). The increase in neutron flux due to improvements in instrumentation has led to routine measurements at the air/water interface that are faster and involve samples with lower isotopic contrast than in previous experiments. One can now resolve the surface excess of a single deuterated component on the second time scale and the composition of a mixture on the minute time scale, and information about adsorption processes and dynamic rheology can also be accessed...
July 12, 2017: Advances in Colloid and Interface Science
Soodamani Periyasamy, Venkatrajan Gopalakannan, Natrayasamy Viswanathan
The present study was focused on Cr(VI) removal using eco-friendly materials like cellulose (Cel), hydrotalcite (HT), hydroxyapatite (HAp) and their composite forms. The cellulose/hydrotalcite (CelHT) and cellulose/hydroxyapatite (CelHAp) composites were synthesized by dispersing HT and HAp individually in cellulose polymeric matrix. To enhance the Cr(VI) sorption capacity (SC) and easy separation, cellulose supported magnetic composites namely iron-oxide coated cellulose/hydrotalcite (Fe3O4@CelHT) and cellulose/hydroxyapatite (Fe3O4@CelHAp) were synthesized by in situ fabrication method...
October 15, 2017: Carbohydrate Polymers
Frank-Dieter Kopinke, Anett Georgi, Ulf Roland
Diffusive isotope fractionation of organic compounds in aqueous solution was investigated by means of liquid-liquid and liquid-gas partitioning experiments under kinetic control. The two-film model was used to describe phase-transfer kinetics. It assumes the diffusion of solutes across a stagnant water boundary layer as the rate-controlling step. For all investigated solutes (benzene-D0 and -D6, toluene-D0, -D5, and -D8, cyclohexane-D0 and -D12), there was no significant observable fractionation effect between nondeuterated and perdeuterated isotopologues, resulting in a ratio of diffusion coefficients Dlight: Dheavy=1...
August 15, 2017: Science of the Total Environment
Cheng Li, Stevin S Pramana, Na Ni, John A Kilner, Stephen J Skinner
Acceptor doped LaNbO4 is a promising electrolyte material for proton conducting fuel cell (PCFC) applications. As charge transfer processes govern device performance, the outermost surface of acceptor doped LaNbO4 will play an important role in determining the overall cell performance. However, the surface composition is poorly characterized, and the understanding of its impact on the proton exchange process is rudimentary. In this work, the surface chemistry of 1 at% Sr doped LaNbO4 (La0.99Sr0.01NbO4-d, denoted as LSNO) proton conductor is characterized using LEIS and SIMS...
August 18, 2017: ACS Applied Materials & Interfaces
Andrej Skerencak-Frech, Michael Trumm, Daniel R Fröhlich, Petra J Panak
The complexation of Cm(III) with malonate is studied by time-resolved laser fluorescence spectroscopy (TRLFS) in the temperature range from 25 to 90 °C. Three complexes ([Cm(Mal)n](3-2n), n = 1, 2, 3) are identified and their molar fractions are determined as a function of the ligand concentration, the ionic strength, and the temperature. A general shift of the chemical equilibrium toward higher complexes with increasing temperature is observed, with the [CmMal3](3-) complex forming only at T > 40 °C. The conditional stability constants (log K'n(T)) are calculated and extrapolated to Im = 0 with the specific ion interaction theory (SIT)...
August 18, 2017: Inorganic Chemistry
Mohamed Shaban, Mohamed E M Hassouna, Fadya M Nasief, Mostafa R AbuKhadra
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...
August 17, 2017: Environmental Science and Pollution Research International
Pankaj Kumar Pandey, Priyanka Kaushik, Kamla Rawat, V K Aswal, H B Bohidar
Zein, a predominantly hydrophobic protein, was sustained as a stable dispersion in ethanol-water (80 : 20, % (v/v)) binary solvent at room temperature (25 °C). Addition of aqueous dsDNA solution (1% (w/v)) to the above dispersion prepared with the protein concentration of Czein = 0.01-0.5% (w/v) caused a concomitant change in ethanol content from 14-35% (v/v), which in turn generated zein nanoparticles in situ of size 80-120 nm increasing with water content. The subsequent associative interaction between DNA (polyanion; 2000 bps) and the positively charged zein nanoparticles, (at pH = 4) was driven by Coulombic forces, and by the solvent hydrophobicity due to the ethanol content of the binary solvent...
August 18, 2017: Soft Matter
Robinson W Flaig, Thomas M Osborn Popp, Alejandro M Fracaroli, Eugene A Kapustin, Markus J Kalmutzki, Rashid M Altamimi, Farhad Fathieh, Jeffrey A Reimer, Omar M Yaghi
The use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material which can uptake CO2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents which uptake CO2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. The equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new finding that has impact on control of the chemistry of CO2 capture in MOF materials and one that highlights the importance of geometric constraints and the mediating role of water within the pores of MOFs...
August 17, 2017: Journal of the American Chemical Society
Dayong Chen, Zhiwei Sun, Thomas P Russell, Lihua Jin
The co-assembly kinetics of graphene oxide (GO) nanosheets and diblock copolymers at the water/toluene interface is probed by tracking the dynamic interfacial tension using pendant drop tensiometry. The diblock copolymer significantly enhances the surfactancy of the GO nanosheets at the interface. It is found that diblock copolymers rapidly adsorb to the water/toluene interface and enhance the adsorption affinity of GO nanosheets to the interface. The continuous adsorption of GO at the interface leads to a random loose packing state, at which the adsorbed GO and diblock copolymers start to form an elastic film...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
S Ursula Salmon, Matthew R Hipsey, Geoffrey W Wake, Gregory N Ivey, Carolyn E Oldham
Assessment of water quality evolution in the thousands of existing and future mine pit lakes worldwide requires new numerical tools that integrate geochemical, hydrological, and biological processes. A coupled model was used to test alternative hypothesized controls on water quality in a pit lake over ∼8 years. The evolution of pH, Al, and Fe were closely linked; field observations were reproduced with generic solubility equilibrium controls on Fe(III) and Al and a commonly reported acceleration of the abiotic Fe(II) oxidation rate by 2-3 orders of magnitude...
August 16, 2017: Environmental Science & Technology
Norio Kitadai, Kumiko Nishiuchi, Akari Nishii, Keisuke Fukushi
It has long been suggested that mineral surfaces played a crucial role in the abiotic polymerization of amino acids that preceded the origin of life. Nevertheless, it remains unclear where the prebiotic process took place on the primitive Earth, because the amino acid-mineral interaction and its dependence on environmental conditions have yet to be understood adequately. Here we examined experimentally the adsorption of L-lysine (Lys) and its dimer (LysLys) on amorphous silica over a wide range of pH, ionic strength, adsorbate concentration, and the solid/water ratio, and determined the reaction stoichiometries and the equilibrium constants based on the extended triple-layer model (ETLM)...
August 15, 2017: Origins of Life and Evolution of the Biosphere
Amir Haji-Akbari, Pablo G Debenedetti
Surface freezing is a phenomenon in which crystallization is enhanced at a vapor-liquid interface. In some systems, such as n-alkanes, this enhancement is dramatic and results in the formation of a crystalline layer at the free interface even at temperatures slightly above the equilibrium bulk freezing temperature. There are, however, systems in which the enhancement is purely kinetic and only involves faster nucleation at or near the interface. The first, thermodynamic, type of surface freezing is easier to confirm in experiments, requiring only the verification of the existence of crystalline order at the interface...
August 14, 2017: Journal of Chemical Physics
Yoshiharu Suzuki
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...
August 14, 2017: Journal of Chemical Physics
Elena A Golysheva, Georgiy Yu Shevelev, Sergei A Dzuba
In glassy substances and biological media, dynamical transitions are observed in neutron scattering that manifests itself as deviations of the translational mean-squared displacement, 〈x(2)〉, of hydrogen atoms from harmonic dynamics. In biological media, the deviation occurs at two temperature intervals, at ∼100-150 K and at ∼170-230 K, and it is attributed to the motion of methyl groups in the former case and to the transition from harmonic to anharmonic or diffusive motions in the latter case. In this work, electron spin echo (ESE) spectroscopy-a pulsed version of electron paramagnetic resonance-is applied to study the spin relaxation of nitroxide spin probes and labels introduced in molecular glass former o-terphenyl and in protein lysozyme...
August 14, 2017: Journal of Chemical Physics
Pedro A Inostroza, Riccardo Massei, Romy Wild, Martin Krauss, Werner Brack
Emerging pollutants are ubiquitous in the aquatic system and may pose risks to aquatic ecosystems. The quantification and prediction of environmental partitioning of these chemicals in aquatic systems between water, sediment and biota is an important step in the comprehensive assessment of their sources and final fates in the environment. In this multi-compartment field study, we applied equilibrium partitioning theory and chemical activity estimates to investigate the predictability of concentrations in Gammarus pulex as a model invertebrate from water and sediment in a typical small central European river...
August 12, 2017: Environmental Pollution
PeiYing Zhu, DaPeng Li, Yong Huang, Yong Li
Phosphorus (P) adsorpted by sediments, when covered by and mixed with ignited sediments from Meiliang Bay in Tai Lake, was analyzed in the laboratory. Potassium dihydrogen phosphate (KH2PO4) was added to the parallel experimental units to simulate periodic external P input. Based on the Langmuir model, the sediments after ignition had a greater Smax (maximum P adsorption), a lower equilibrium phosphorus concentration at zero adsorption (EPC0), and a lower degree of phosphorus saturation in comparison with sediments without ignition...
August 15, 2017: Environmental Science and Pollution Research International
Zh А Baigazinov, S N Lukashenko, S S Karatayev, А V Panitski, А S Mamyrbayeva, S А Baigazy, T Ye Kozhakhanov, L F Subbotina
Following a continuous intake of tritium (T) by laying hens' over a 55 day period, an increase of НТО concentration both in eggs and meat was observed over the first 2 weeks for intakes via inhalation and ingestion of water and grass meal. After this time, equilibrium of the T in these products occurred. It was found that when the intake of HTO is from water, air and grass meal, the ratio of its activity concentration in muscular tissue to that in eggs does not exceed 1, 4, and 6 respectively. The ratio of ОBТ concentration to that of НТО in the meat of hens (ОBТ/HTO) when intakes were from water, air and grass meal were 0...
August 11, 2017: Journal of Environmental Radioactivity
A V Borges, F Darchambeau, T Lambert, S Bouillon, C Morana, S Brouyère, V Hakoun, A Jurado, H-C Tseng, J-P Descy, F A E Roland
We report a data-set of CO2, CH4, and N2O concentrations in the surface waters of the Meuse river network in Belgium, obtained during four surveys covering 50 stations (summer 2013 and late winter 2013, 2014 and 2015), from yearly cycles in four rivers of variable size and catchment land cover, and from 111 groundwater samples. Surface waters of the Meuse river network were over-saturated in CO2, CH4, N2O with respect to atmospheric equilibrium, acting as sources of these greenhouse gases to the atmosphere, although the dissolved gases also showed marked seasonal and spatial variations...
August 11, 2017: Science of the Total Environment
Marek Cigáň, Miroslav Horváth, Juraj Filo, Klaudia Jakusová, Jana Donovalová, Vladimír Garaj, Anton Gáplovský
The water sensing properties of two efficient two-component fluorescent "turn-on" chemo-sensors based on the 7-dialkylaminocoumarin oxime acid-base equilibrium were investigated. Interestingly, although simple frontier orbital analysis predicts an intramolecular photoinduced electron transfer quenching pathway in conjugated oximates, TD-DFT (Time-dependent density functional theory) quantum chemical calculations support non-radiative dark S₁ excited state deactivation as a fluorescence quenching mechanism...
August 12, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Gong Yan, Su Philipp Oliver
In this paper, a high performance adsorbent (hydrous manganese oxides onto acylamino and hydroxyl functionalized hydrogel) containing manganese oxide was prepared by the cross-linking polymer; the novel composite adsorbent has an excellent adsorption for Hg(II) removal. The adsorbent was characterized by scanning electron microscopy and Fourier transform infrared analysis, the hydrogel adsorbent had a typical three-dimensional network structure, and manganese oxides particles were dispersed into the channel and pores structure...
August 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
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