Binary Solutions Of Water Research Articles

Exploring the dynamic changes in hydrogen bond structure of water and heavy water under external perturbation of DMF

The Raman spectra of DMF-water/heavy water binary solutions at different volume ratios are measured to investigate the hydrogen bond structure between N, N-dimethylformamide (DMF) and water/heavy water. It was observed that when VDMF below 40 %, DMF reinforces the hydrogen bond among water molecules through the substitution of a small amount of water molecules within the tetrahedral structure. However, a similar enhancement phenomenon is not observed in heavy water. When VDMF is less than 60 %, the hydrogen bonds among DMF and heavy water molecules affect the symmetry of OD covalent bond. Furthermore, as VDMF exceeds 40 %/60 %, the tetrahedral structures of water and heavy water are gradually replaced by DMF·3H2O/3D2O, DMF·2H2O/2D2O, and DMF·H2O/D2O clusters. The transition point of hydrogen bond structure in DMF- aqueous solution moved to VDMF = 15 % under the influence of under the influence of dynamic high pressure caused by pulsed laser beam. This study provides valuable insights into the microstructure of water/heavy water clusters.

Refractive Index Measurements of Ethanol–Water Binary Liquid Solutions Using a Graded-Index Fiber Tip Sensor

Refractive Index Measurements of Ethanol–Water Binary Liquid Solutions Using a Graded-Index Fiber Tip Sensor

Reaction of decabromodiphenyl ether with organo-modified clay-templated zero-valent iron in water-tetrahydrofuran solution: Nano- to micrometric scale effects

Smectite clay-templated nanoscale zero-valent iron (CZVI) was modified with tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA) to achieve organoclay-templated ZVI (OCZVI). The reactivity of various OCZVIs was evaluated on the basis of degradation of decabromodiphenyl ether (DBDE) in tetrahydrofuran (THF)-water binary solution. Characterization of OCZVI interlayer at nanometric scale indicated that the clay particles had the domains with three basal spacings in the THF/water solution. In the 50 % THF solution TMPA modification promoted the formation of the domains with a basal spacing at 1.56 nm, which could promote the degradation of DBDE. At the micrometric scale, in the 90 % THF solution TMA and TMPA modification tended to enhance the aggregation of OCZVI particles, while the HDTMA modification reduced the aggregation, and high percentage of modification yielded viscous gel structures. The relatively rapid sedimentation processes in 90 % THF solution (compared to that in 50 % THF solution) and formation gel structures could reduce the access of DBDE to the interlayer reactive nZVIs, and lead to the significant reduction in reaction rate. These results provide important insights to the organo-modification on clays which could alter their orientations and dispersion in organic-water binary solution to achieve the desired reactivity on confined clay surfaces.

Hydrogen bonding network dynamics of 1,2-propanediol-water binary solutions by Raman spectroscopy and stimulated Raman scattering

Raman spectroscopy and stimulated Raman scattering (SRS) were used to investigate the hydrogen bonding (HB) network in 1,2-propanediol (1,2-PD)-water binary solutions. Abnormal changes in hydrogen bonds (HBs) were detected when V1,2-PD (volume fraction of the1,2-PD) was 0.4. In the case of Raman spectroscopy, the HB strength of water is weakened and then strengthened with the increase of 1,2-PD volume fraction. In the case of SRS, two new peaks at 3283 cm−1 and 3319 cm−1 were appeared, which demonstrated the appearance of ice-like structures near the methyl group and the weakening of HBs. Based on these phenomena, the HB structure of this binary system underwent a transition from H2O-H2O to H2O-1,2-PD when the V1,2-PD was 0.4 as V1,2-PD increased. This work serves as a reference value for the study of HB networks in alcohol-water binary solutions.

Ultrasonic Studies of Substituted Aryl Bisthiourea in Binary Solution at 298K Temperature

The ultrasonic velocity (u), density (ρ) and viscosity (η) have been measured for substituted aryl Bisthiourea in binary solution at 298K temperature by using ultrasonic interferometric technique. The observed experimental data have been used to study molecular interactions in different percent composition of 1,4 dioxane and water binary solution for different parameters such as adiabatic compressibility, apparent molar volume, apparent molar compressibility, relative association, acoustic impedance , free length, and relaxation time.

Raman spectra and structure of hydrogen‐bonded water oligomers in tetrahydrofuran–H2O binary solutions

AbstractRaman spectra of hydrogen‐bonded water oligomers have been resolved from concentration‐dependent Raman spectra of tetrahydrofuran (THF)–water binary solutions with the use of multivariate curve resolution with alternating least‐squares (MCR‐ALS) analysis, assisted by hypothetical addition multivariate analysis with numerical differentiation (HAMAND) procedure. A total of 38 Raman spectra acquired in the broad spectral range of 700–3810 cm−1were analyzed in a multistep procedure to explain the spectral variations in terms of four components: pure THF, Spectra A, Spectra B, and Spectra C. A four‐component MCR‐ALS analysis was performed with initial guesses by HAMAND analysis to refine the spectral components and determine their concentration dependence. Of the MCR‐ALS resolved three spectra, A was identified as THF(H2O), B as THF(H2O)2with two hydrogens attached to THF, and C as THF(H2O)nhaving two or more linearly hydrogen‐bonded oligomers of water (n = 2–4). Observed spectral changes of the OH stretch vibrations of water and those of the C–C/C–O stretches of THF were well reproduced by quantum chemical calculations. Formation of hydrogen‐bonded water oligomers in THF–water complexes has thus been revealed. The present study provides a new insight into the basics of hydrogen bonding formation in aqueous systems. It also provides experimental methodology for extracting concentration‐dependent minor spectral components contained in complex condensed‐phase Raman spectra.

Determination of temperature-dependent Fermi resonance in acetonitrile-water binary solution by two-dimensional correlation Raman spectroscopy.

Acetonitrile (AN), as an organic solvent, has a wide range of applications. The C≡N stretching vibration mode (ν2) and the combination mode (ν3 + ν4) are coupled by Fermi resonance (FR). In this work, the phase transition and the interaction mechanism of the 60% AN-water binary solution (AN-Water) were analyzed by calculating FR parameters and two-dimensional correlation Raman spectroscopy (2DCRS). The change in the ν2 band and the base bands ν3 and ν4 caused energy transfer by anharmonic interaction, which led to a change in FR parameters. With a reduced temperature, the energy transfer was caused by microheterogeneity and the energy transfer effect (293-273K), the phase separation (263-233K), and the phase transition of AN (223-173K). The 2DCRS and Gaussian deconvolution provided more information on FR, which revealed the interaction mechanism of the Fermi doublet. The polarity and binding modes of molecules provided a new perspective for analyzing the transmission of electrons and ions in the electrolyte at different temperatures.

Investigation of hydrogen bonding in aqueous acetone mixtures by Raman spectroscopy

AbstractThe Raman spectra of aqueous acetone solution with various concentrations were measured at room temperature and atmospheric pressure. We find that the peak at ~3400 cm−1 showed a significant blue shift at Va (Va represents the volume fraction of acetone) >0.2, whereas the peak at 197 cm−1 exhibited red shift under the same conditions. The results indicate that the cage structure of water is destroyed and a large number of water molecules form acetone–water complex with acetone molecules. Moreover, the acetone–water complex from the acetone–(water)2 structure gradually changed to acetone–water at Va > 0.6. In addition, the Raman spectra of methyl groups were also studied, which illustrates that the methyl group of acetone forms a hydrophobic hydrated structure. Finally, the phase transition process of acetone–water complex in methanol–water binary solution was discussed.

Study of hydrogen bonding interactions in ethylene glycol-water binary solutions by Raman spectroscopy

EG (ethylene glycol) is a good model system for the study of the fundamental hydrogen bonds in aqueous solutions. Using Raman spectroscopy, we have investigated the EG volume fraction induced variation in the hydrogen bonding interactions and conformations of EG-H2O (water) binary solutions. New hydrogen bonding networks is evidenced by the appearance of remarkable changes in Raman spectra and the full width at half maximum (FWHM) when the mixing volume ratio is 0.5. The H-bond in water molecules firstly strengthened and then weakened with the increasing concentration of EG. Meanwhile, the dominant association structure also changed from H2O-H2O to EG-H2O in binary solutions in this process. We provide a simple but effective method for studying EG-H2O binary solutions. It also has exciting potential prospects and can be easily extended to other mixing situations.

Real-Time Observation of Solvation Dynamics of Electron in Actinide Extraction Binary Solutions of Water and n-Tributyl Phosphate.

The excess electron in solution is a highly reactive radical involved in various radiation-induced reactions. Its solvation state critically determines the subsequent pathway and rate of transfer. For instance, water plays a dominating role in the electron-induced dealkylation of n-tributyl phosphate in actinide extraction processing. However, the underlying electron solvation processes in such systems are lacking. Herein, we directly observed the solvation dynamics of electrons in H-bonded water and n-tributyl phosphate (TBP) binary solutions with a mole fraction of water (Xw) varying from 0.05 to 0.51 under ambient conditions. Following the evolution of the absorption spectrum of trapped electrons (not fully solvated) with picosecond resolution, we show that electrons statistically distributed would undergo preferential solvation within water molecules extracted in TBP. We determine the time scale of excess electron full solvation from the deconvoluted transient absorption-kinetical data. The process of solvent reorganization accelerates by increasing the water molar fraction, and the rate of this process is 2 orders of magnitude slower compared to bulk water. We assigned the solvation process to hydrogen network reorientation induced by a negative charge of the excess electron that strongly depends on the local water environment. Our findings suggest that water significantly stabilizes the electron in a deeper potential than the pure TBP case. In its new state, the electron is likely to inhibit the dealkylation of extractants in actinide separation.

Numerical investigations on flow boiling heat transfer of ammonia water binary solution (NH3/H2O) in a horizontal microchannel

The flow boiling heat transfer characteristics of NH3/H2O mixture in a 2D single horizontal microchannel (0.4 mm width × 6 mm length) were investigated by Computational Fluid Dynamics (CFD) method. The multiphase VOF model and modified phase change Lee method were adopted to address the non-isothermal phase change process of the flowing zeotropic NH3/H2O mixture, while the variations of the binary mixture thermophysical properties were also taken into account. The effects of mass flux (46~552 kg/(m2∙K)), inlet NH3 concentration (0-35% by mole) and heating wall temperature (20.5~70 ∘C) on the overall and local flow boiling heat transfer performance have been comparatively evaluated under constant heating wall temperatures. According to the numerical results, the heat dissipation rate of NH3/H2O mixture flow boiling could reach up to 1.41 MW/m2 at a mass flux of 552 kg/(m2∙s), which was 2.05 times of water single-phase flow cooling under a same constant heating wall temperature of 50 ∘C. It was also revealed that, for NH3/H2O mixture flow boiling in the microchannel, there was a threshold of inlet NH3 concentration to maintain a certain level of heat dissipation rate at a given mass flow rate and further increasing the inlet NH3 concentration would no longer benefit the heat dissipation process. Furthermore, there were no local dry-outs found throughout the whole microchannel length under all the simulation conditions in this study, which could be attributed to the unique flow boiling behaviors of zeotropic NH3/H2O mixture. Therefore, it should be noticed that NH3/H2O mixture, under certain conditions, could be a good alternative coolant for preventing local dry-outs and maintaining a certain functional temperature of electronic components.

Three stages of hydrogen bonding network in DMF-water binary solution

Three stages of hydrogen bonding (HB) network in N, N-dimethylformamide (DMF)-water binary solution were investigated by Raman spectroscopy with different mixing ratios at room temperature and atmospheric pressure. The results show that the addition of DMF strengthens the HB network of water when the volume fraction of DMF (VDMF) is less than 0.4. However, the tetrahedral structure of water is destroyed when VDMF reaches 0.4, and water molecules and DMF molecules form two DMF-water complexes, namely DMF·3H2O and DMF·2H2O. While VDMF reaches 0.8, the DMF-water complex is transformed into DMF·H2O structure due to the instability of DMF·nH2O (n = 2, 3). In addition, the newly formed HB C=O···H-C, rather than the weak HB C-H···O, leads to the red shift of C–H stretching vibration mode.

Hydrogen bonding effect on Raman modes of Formic acid-water binary solutions

Raman spectroscopy in combination with density functional theory (DFT) calculation was used to investigate the interaction between water and Formic acid. Raman spectra of formic acid (FA)-water binary solutions with different concentrations had been obtained at room temperature and ambient pressure. Gaussian deconvolution analysis was used for explaining the effect of FA on the OH stretching band. The frequencies of symmetric and asymmetric OH stretching mode changed significantly when the volume fraction of FA is 0.2 and 0.8 respectively, which attributed to the hydrogen bonding (HB) structure of water was affected, leading to FA-water structure undergo two phase transitions. Besides, the Raman frequencies of CO and CH stretching mode of FA also reverse at both two concentrations, which represent the main species of FA molecules were transformed. These results about the transition of FA-water structure and formic-formic acid structure were analyzed theoretically through Raman spectra and compared with the concrete details from density functional theory (B3LYP) calculations with 6-311++G(d, p) level.

The joint effect of surface polarity and concentration on the structure and dynamics of acetonitrile solution: a molecular dynamics simulation study.

The interfacial properties of the acetonitrile (ACN)-water-silica interface have great implications in both liquid chromatography and heterogeneous catalysis. We have performed molecular dynamics (MD) simulations of ACN and water binary solutions to give a comprehensive study of the collective effect of silica surface polarity and ACN concentration on interfacial structures and dynamics by tuning both surface charges and ACN concentration. MD simulation results indicate that many properties in the liquid-solid interface region undergo a monotonic change as the silica surface is tuned from polar to apolar due to the weakening of hydrogen bonding, while their dependence on ACN concentration is presumably governed by the preferential adsorption of water at the silica surface over ACN. However, at apolar surfaces, the interfacial structures of both water and ACN behave like the liquid-vapor interface, and this resemblance leads to an enrichment of ACN at the interface as well as accelerated dynamics, which is very different from that in the bulk solution. The organization of ACN molecules at both polar and apolar surfaces can be attributed to the amphiphilic nature of ACN, by which the micro-heterogeneity domain formed can persist both in the bulk and at the liquid-solid interface. Moreover, extending diffusion analysis to the second layer of the interface shows that the interfacial transport pathways at polar surfaces are likely very different from that of apolar surfaces. These simulation results give a full spectrum description of the ACN/water liquid-solid interface at the microscopic level and will be helpful for explaining related spectroscopic experiments and understanding the microscopic mechanisms of separation protocols in current chromatography applications.

Solubility and Activity Coefficients of Atmospheric Surfactants in Aqueous Solution Evaluated Using COSMOtherm.

Fatty acids (CH3(CH2)n-2COOH) and their salts are an important class of atmospheric surfactants. Here, we use COSMOtherm to predict solubility and activity coefficients for C2-C12 fatty acids with even number of carbon atoms and their sodium salts in binary water solutions and also in ternary water-inorganic salt solutions. COSMOtherm is a continuum solvent model implementation which can calculate properties of complex systems using quantum chemistry and thermodynamics. Calculated solubility values of the organic acids in pure water are in good agreement with reported experimental values. The comparison of the COSMOtherm-derived Setschenow constants for ternary solutions comprising NaCl with the corresponding experimental values from the literature shows that COSMOtherm overpredicts the salting out effect in all cases except for the solutions of acetic acid. The calculated activity and mean activity coefficients of fatty acids and fatty acid sodium salts, respectively, show deviation of the systems from ideal solution. The computed mean activity coefficients of the fatty acid salts in binary systems are in better agreement with experimentally derived values for the organic salts with longer aliphatic chain (C8-C10). The deviation of the solutions from ideality could lead to biased estimations of cloud condensation nuclei number concentrations if not considered in Köhler calculations and cloud microphysics.

Options for refractive index and viscosity matching to study variable density flows

Variable density flows are often studied by mixing two miscible aqueous solutions of different densities. To perform optical diagnostics in such environments, the refractive index of the fluids must be matched, which can be achieved by carefully choosing the two solutes and the concentration of the solutions. To separate the effects of buoyancy forces and viscosity variations, it is desirable to match the viscosity of the two solutions in addition to their refractive index. In this manuscript, several pairs of index matched fluids are compared in terms of viscosity matching, monetary cost, and practical use. Two fluid pairs are studied in detail, with two aqueous solutions (binary solutions of water and a salt or alcohol) mixed into a ternary solution. In each case: an aqueous solution of isopropanol mixed with an aqueous solution of sodium chloride (NaCl) and an aqueous solution of glycerol mixed with an aqueous solution of sodium sulfate ( $$\hbox {Na}_2\hbox {SO}_4$$ ). The first fluid pair allows reaching high-density differences at low cost, but brings a large difference in dynamic viscosity. The second allows matching dynamic viscosity and refractive index simultaneously, at reasonable cost. For each of these four solutes, the density, kinematic viscosity, and refractive index are measured versus concentration and temperature, as well as wavelength for the refractive index. To investigate non-linear effects when two index-matched, binary solutions are mixed, the ternary solutions formed are also analyzed. Results show that density and refractive index follow a linear variation with concentration. However, the viscosity of the isopropanol and NaCl pair deviates from the linear law and has to be considered. Empirical correlations and their coefficients are given to create index-matched fluids at a chosen temperature and wavelength. Finally, the effectiveness of the refractive index matching is illustrated with particle image velocimetry measurements performed for a buoyant jet in a linearly stratified environment. The creation of the index-matched solutions and linear stratification in a large-scale experimental facility are detailed, as well as the practical challenges to obtain precise refractive index matching.

Density, Viscosity, Refractive Index, and Excess Properties of Binary and Ternary Solutions of Poly(ethylene glycol), Water, and Dipotassium Tartrate at 298.15 K and Atmospheric Pressure

The refractive index (nD) and density (ρ) values of the poly(ethylene glycol) (PEG) 1500 + dipotassium tartrate + water ternary system and physical properties of PEG 1500 + water and dipotassium tartrate + water binary solutions have been measured at 298.15 K and atmospheric pressure. Moreover, the refractive index deviation (ΔnD), viscosity deviation (Δη), apparent specific volume (Vφ), excess molar volume (VE), and excess Gibbs energy of activation for viscous flow (ΔG‡E) were calculated from the experimental measurements to analyze the behavior of the binary solutions and the refractive index deviation (ΔnD) and excess molar volume (VE) of the ternary solution. These results were fitted to Redlich–Kister polynomial and Cibulka Equations to estimate the interaction parameters. Adjustments were made to the refractive index and density to obtain a third-order polynomial expansion model and a second-order equation, respectively. The intermolecular interactions between the mixing components were demonstrate...

Molecular Dynamics Studies on Liquid/Vapor Interface Properties and Structures of 1-Ethyl-3-methylimidazolium Dimethylphosphate-Water.

1-Ethyl-3-methylimidazolium dimethylphosphate ([Emim][Dmp])-water binary solution is one of the promising new working-pairs for absorption heat pump and absorption chillers, which are widely used to recover industrial waste heat. In the absorption process, the mass and heat transfer at the interface greatly depend on interface microscopic structure. Therefore, in order to understand the absorption process, it is very important to study the interface microscopic structure. The liquid-vapor interface properties, as well as the orientation of [Emim]+, [Dmp]-, water at the interface and its aqueous solution with different water mole fraction, were studied using classical all-atom force field by molecular dynamic simulations. The simulated bulk mass density fitted by hyperbolic tangent function for each system was in good agreement with the experiment data, with the relative deviation between simulated and experimental value within 2%. The simulated results indicate that anion is always distributed at the outmost layer of the interface, followed by cation and water molecule. In [Emim][Dmp], the tilt angle of imidazolium rings to the surface normal is in the range of 0° < θ < 12°; for most cation, their ethyl and methyl tilted toward gas phase and bulk, respectively, but for a few cation, their ethyl and the methyl take the opposite orientation. For anion, one methyl prefers to turn toward gas phase and another methyl (PC vector from P atom to C atom) lie nearly parallel to the surface, while one PO vector (from P atom to O atom) turns toward liquid bulk and another PO vector is nearly parallel to the surface. In aqueous solution of [Emim][Dmp], the tilt angle of the imidazolium ring to the surface normal becomes larger (0° < θ < 37°) at the interface, but almost all ethyl intend to tilt toward gas phase and the methyl tilt toward liquid bulk compared with pure [Emim][Dmp]. Two methyl in anion prefer to turn toward gas phase and its two PO vectors toward liquid bulk. This orientation indicates that pure [Emim][Dmp] absorb water in gas phase more easily than [Emim][Dmp]+H2O system does. Water molecules are distributed in the inner layer of the interface with two OH vectors (from O atom to H atom) tilting toward external surface.

Modification of silica–alkyl phase by cationic surfactant and silica precursor

A new sandwich-type (silica–organic silica) composite in the form of spherical beads or irregular particles was prepared by condensation of tetraethyl orthosilicate on hydrophobic Eurospher-100 C18 and LiChrosorb RP-18 particles. The silica–alkyl composites were characterised by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, nitrogen adsorption porosimetry, X-ray diffraction and thermogravimetric analysis, combined with mass spectrometry. Experimental data indicate that the long hydrocarbon chains of the initial material combined with silica, producing a sandwich-type composite. Additionally, in the surface phase, small microcrystallites of silica, exhibiting very regular pore shape and uniform pore size, were produced. The obtained hybrid material shows some unique features. The advantage of the applied synthesis route is that it gave a new organic–inorganic material which is completely wettable by water and displays the ability to absorb hydrophobic components from a binary aqueous solution. The surface properties were examined by adsorption from binary water solutions. As a model organic adsorbate, metronidazole was chosen.

Orientation and Structure of Acetonitrile in Water at the Liquid–Vapor Interface: A Molecular Dynamics Simulation Study

We report molecular dynamics simulations of acetonitrile–water binary solutions at concentrations of 0.032–0.59 mole fraction. We find that at low bulk concentration acetonitrile has an enhanced population near the liquid/vapor interface. The surface-bound acetonitrile molecules exhibit anisotropic orientations and lie nearly flat along the solution surface with their terminal methyl groups directed toward the vapor. Upon increasing the bulk concentration, the formation of acetonitrile domains is promoted by interactions between hydrophobic methyl moieties. Dipole–dipole interactions facilitate a pseudonematic, antiparallel pairing of near-neighbor molecules both in the bulk solution and near the liquid/vapor interface. Near the interface the preferred orientation of acetonitrile flattens further to accommodate antiparallel pairing of neighboring molecules such that the methyl group remains above the solution. This study paints a surprisingly complex picture of a binary organic–water solution that manifests behavior similar to liquid crystals through preferred orientations and pseudonematic antiparallel pairing.