Tetrahydrofuran Water Mixtures Research Articles

Integrated effect of bulk cations on nano-confined reactivity of clay-intercalated subnanoscale zero-valent iron in water-tetrahydrofuran mixtures

Smectite clay-intercalated subnanoscale zero-valent iron (CSZVI) exhibits superior reactivity toward contaminants due to the small iron clusters (∼0.5 nm) under nano-confinement, which however is significantly influenced by the solution chemistry e.g., various cations, of polluted soil and water. This work was undertaken to elucidate the mechanisms of solution chemistry effects on dehalogenation ability of CSZVI in water-tetrahydrofuran solution using decabromodiphenyl ether as a model contaminant. By combined spectroscopic characterization and molecular dynamics simulation, it was revealed that bulk cations, i.e., Na+, K+, Mg2+ and Ca2+ collectively affected the interlayer distance, water content and Brønsted acidity of CSZVI and thus its degradation efficiency. Although causing inter-particle aggregation, Mg2+ induced optimal nano-confined interlayers at concentration of 20 mM, exhibiting a superior debromination efficiency with rate constant 9.84 times larger than that by the common nano-sized ZVI. Conversely, K+ rendered the interlayers less reactive, but protected CSZVI from corrosion loss with higher electron utilization efficiency, which was 1.7 times higher than CSZVI in presence of Mg2+. The findings provide new strategies to manipulate the reactivity of nano-confined CSZVI for effective wastewater and contaminated soil remediation.

Mechanisms of separation between tetrahydrofuran and water using hydroxystearic acid

Tetrahydrofuran (THF) is fully miscible in water, and it interacts with it via hydrogen (H) bonds. We discover that the fatty acid hydroxystearic acid (HSA) separates THF from water because it preferentially H-bonds water and increases the proportion of single H-bond donors (SD) relative to double H-bond donors (DD). This change in the coordination of water molecules from DD to SD leads to phase separation between THF and water. We previously established this separation mechanism using sugars and surfactants and other water miscible solvents. Here, we use attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) to prove that this mechanism is also responsible for THF–water separation using HSA, thereby demonstrating the universality of the proposed separation mechanism. Using synchrotron small-angle x-ray scattering, we show how HSA self-assembles into reverse micelles in THF–water mixtures and determine their persistence length and periodicity using a modified Landau model. Reverse micelles host water in their interior and swell upon increasing the water content, as shown by light scattering. They then turn into droplets detectable using optical or confocal microscopy. When THF–water emulsions separate, they yield water-rich and THF-rich free phases. ATR-FTIR reveals that the top phase of THF–water mixtures separated by HSA is THF-rich. Moreover, when Cu2+ ions are in solution, HSA causes their migration into the THF-rich phase, enabling the simultaneous separation of THF and Cu2+ cations from water. This study demonstrates the potential for engineering the water structure to aid in the separation of water-miscible solvents from water with important implications for water treatment.

Hydrogen bonding and surface tension properties of aqueous solutions of tetrahydrofuran

Significant changes observed in the tetrahydrofuran—water mixtures of different molar ratios have been determined the extent of intermolecular association via quantitative Raman experiment. The hydrogen bonding changes with the addition of tetrahydrofuran. The changes of surface tension are analyzed with hydrogen bonding in the mixtures. The result shows that the strengthening of hydrogen bonding between tetrahydrofuran and water contributes to weak the surface tension in the solutions. The correlation between surface tension and mole fractions of tetrahydrofuran is non-linear. This study provides an experimental basis for enriching the hydrogen bonding theory of multivariate aqueous solution systems.

Zero-Discharge Process for Recycling of Tetrahydrofuran–Water Mixtures

The sustainable design of separation and polymer synthesis processes is of great importance. Therefore, an energy-efficient process for the purification of tetrahydrofuran (THF)–water (H2O) solvent mixtures from an upstream polymer synthesis process in pilot scale was developed with the aim to obtain high purity separation products. The advantages and limitations of a hybrid process in the pilot scale were studied utilizing an Aspen Plus Dynamics® simulation at different pressures to prove the feasibility and energy efficiency. For the rough separation of the two components, distillation was chosen as the first process step. In this way, a separation of a water stream of sufficient quality for further precipitations after polymer synthesis could be achieved. In order to overcome the limitations of the distillation process posed by the azeotropic point of the mixture, a vapor permeation is used, which takes advantage of the heat of evaporation already used in the distillation column. For the purpose of achieving the required low water contents, an adsorption column is installed downstream for final THF purification. This leads to a novel hybrid separation process that is energy efficient and thus allows also the use of the solvents again for upstream polymer synthesis achieving the high purity requirements in a closed-loop process.

Experimental Design Optimization of Supramolecular Dispersive Liquid–Liquid Microextraction of Nickel and its Spectrophotometric Determination

A supramolecular dispersive liquid−liquid microextraction method based on the solidification of the floating organic drop (SM-DLLME-SFOD) combined with spectrophotometry was developed for the separation, preconcentration, and determination of trace amounts of nickel from aqueous samples. The method is based on the extraction of the hydrophobic complex of nickel with α-furildioxime in the coacervates made up of undecanol reverse micelles in a water-tetrahydrofuran mixture. The parameters affecting the extraction of nickel were screened by fractional factorial design with central points. Effective experimental parameters were optimized using central composite design. Under the optimized conditions, the calibration graph was linear for nickel in the concentration range of 3–85 µg/L with a determination coefficient of 0.9992. The limit of detection and the enhancement factor of the method were 0.4 µg/L and 147, respectively. The method was successfully applied to the determination of nickel in water and vegetable samples.

Influence of Electronic Environment on the Radiative Efficiency of 9-Phenyl-9H-carbazole-Based ortho-Carboranyl Luminophores.

The photophysical properties of closo-ortho-carboranyl-based donor–acceptor dyads are known to be affected by the electronic environment of the carborane cage but the influence of the electronic environment of the donor moiety remains unclear. Herein, four 9-phenyl-9H-carbazole-based closo-ortho-carboranyl compounds (1F, 2P, 3M, and 4T), in which an o-carborane cage was appended at the C3-position of a 9-phenyl-9H-carbazole moiety bearing various functional groups, were synthesized and fully characterized using multinuclear nuclear magnetic resonance spectroscopy and elemental analysis. Furthermore, the solid-state molecular structures of 1F and 4T were determined by X-ray diffraction crystallography. For all the compounds, the lowest-energy absorption band exhibited a tail extending to 350 nm, attributable to the spin-allowed π–π* transition of the 9-phenyl-9H-carbazole moiety and weak intramolecular charge transfer (ICT) between the o-carborane and the carbazole group. These compounds showed intense yellowish emission (λem = ~540 nm) in rigid states (in tetrahydrofuran (THF) at 77 K and in films), whereas considerably weak emission was observed in THF at 298 K. Theoretical calculations on the first excited states (S1) of the compounds suggested that the strong emission bands can be assigned to the ICT transition involving the o-carborane. Furthermore, photoluminescence experiments in THF‒water mixtures demonstrated that aggregation-induced emission was responsible for the emission in rigid states. Intriguingly, the quantum yields and radiative decay constants in the film state were gradually enhanced with the increasing electron-donating ability of the substituent on the 9-phenyl group (‒F for 1F < ‒H for 2P < ‒CH3 for 3M < ‒C(CH3)3 for 4T). These features indicate that the ICT-based radiative decay process in rigid states is affected by the electronic environment of the 9-phenyl-9H-carbazole group. Consequently, the efficient ICT-based radiative decay of o-carboranyl compounds can be achieved by appending the o-carborane cage with electron-rich aromatic systems.

Comparison of extractive distillation flowsheets for methanol–tetrahydrofuran–water mixtures

Objectives. Synthesis and comparative analysis of the extractive distillation flowsheets for aqueous mixtures of solvents utilized in pharmaceutical industries using the example of a methanol−tetrahydrofuran−water system with various compositions. The ternary system contains two minimally boiling azeotropes that exist in a vapor–liquid phase equilibrium. To evaluate the selective effect of glycerol, the phase equilibria of the methanol–tetrahydrofuran–water and methanol–tetrahydrofuran–water–glycerol systems at 101.32 kPa were studied.Methods. The calculations were carried out in the Aspen Plus V.9.0 software package. The vapor–liquid equilibria were simulated using the non-random two-liquid (NRTL) equation with the binary interaction parameters of the software package database. To account for the non-ideal behavior of the vapor phase, the Redlich–Kwong equation of state was used. The calculations of the extractive distillation schemes were carried out at 101.32 kPa.Results. The conceptual flowsheets of extractive distillation are proposed. The flowsheets consist of three (schemes I–III) or four (scheme IV) distillation columns operating at atmospheric pressure. In schemes I and II, the extractive distillation of the mixtures is carried out with tetrahydrofuran isolation occurring in the distillate stream. Further separation in the schemes differs in the order of glycerol isolation: in the third column for scheme I (traditional extractive distillation complex) or in the second column for scheme II (two-column extractive distillation complex + methanol/water separation column). Sсheme III caters to the complete dehydration of the basic ternary mixtures, followed by the extractive distillation of the azeotropic methanol–tetrahydrofuran system, also with glycerol. Sсheme IV includes a preconcentration column (for the partial removal of water) and a traditional extractive distillation complex.Conclusions. According to the criterion of least energy consumption for separation (the total load of the reboilers of distillation columns), sсheme I (a traditional complex of extractive distillation) is recommended. Additionally, the energy expended for the separation of the basic equimolar mixture using glycerol as the extractive agent was compared with that expended using another selective agent: 1,2-ethanediol. Glycerol is an effective extractive agent because it reduces energy consumption, in comparison with 1,2-ethanediol, by more than 5%.

Integration of Interdigitated Electrodes in Split-Ring Resonator for Detecting Liquid Mixtures

A microwave microfluidic sensor for detecting binary liquid mixtures with a dielectric method at RF/microwave frequencies is presented in this article. The sensor is based on a split-ring resonator (SRR) that is implemented in a microstrip transmission line, with interdigitated electrodes (IDEs) being integrated into the ring for liquid detection. Based on the equivalent circuit of the IDE-SRR device and with a series of finite element simulations, the detection theory is developed, and the device design optimization is investigated. The validation measurements on water-isopropanol liquid mixtures with various concentrations show that the proposed IDE-SRR sensor has higher sensitivity than the previous standard SRR sensor. The IDE-SRR sensor is then used to detect two binary liquids, i.e., water-methanol mixtures and water-tetrahydrofuran mixtures. The measured effective permittivity results of the binary mixtures at RF/microwave frequency range are compared with the existing mixing models for binary dielectric mixtures at zero frequency.

Complexation of a Conjugated Polyelectrolyte and Impact on Optoelectronic Properties.

Electrostatic assembly of conjugated polyelectrolytes, which combine a π-conjugated polymer backbone with pendant ionic groups, offer an opportunity for tuning materials properties and a new route for formulating concentrated inks for printable electronics. Complex coacervation, a liquid-liquid phase separation upon complexation of oppositely charged polyelectrolytes in solution, is used to form dense suspensions of π-conjugated material. A model system of a cationic conjugated polyelectrolyte poly(3-[6'-{N-butylimidazolium}hexyl]thiophene) bromide and sodium poly(styrenesulfonate) dissolved in tetrahydrofuran-water mixtures was used to investigate this complexation behavior of conjugated polyelectrolytes in terms of electrostatic strength, solvent quality, and polymer concentration. The balance of electrostatic interaction between the oppositely charged polyelectrolytes together with their charge compensating counterions and solvent quality for the hydrophobic π-conjugated backbone leads to a rich phase diagram of soluble complexes, precipitates, and complex coacervates. The conjugated polyelectrolyte in the polyelectrolyte complexes has an increased π-conjugation length and enhanced emissivity, with ideal chain configurations due to the reduction of kink sites and torsional disorder. The advantageous photophysical properties in the dense liquid phases makes the scheme attractive for the large-scale processing of optoelectronic devices, chemical sensors, and bioelectronics components.

Determination of vanadium species in water, vegetables, and fruit samples using supramolecular solvent microextraction combined with electrothermal atomic absorption spectrometry

A simple supramolecular solvent microextraction followed by solidification of floating coacervates has been developed for the preconcentration and speciation of vanadium prior to its determination by electrothermal atomic absorption spectroscopy. The speciation is based on the extraction of the hydrophobic complex of V(V) with N-benzoyl-N-phenylhydroxylamine in the coacervates of decanoic acid reverse micelles in the water–tetrahydrofuran mixture. Total vanadium was determined after oxidation of V(IV) to V(V) by hydrogen peroxide. The concentration of V(IV) was calculated from the difference in the amounts of total vanadium and V(V). Under the optimized conditions, the linear range and the enhancement factor of 5.0–1400.0 ng L−1 (with a determination coefficient of 0.9998) and 147 were achieved, respectively. A detection limit (based on 3Sb/m) of 1.2 ng L−1 and a relative standard deviation of 4.2% (at 100.0 ng L−1 for six replicates) were obtained. The method was successfully applied to the determination of vanadium species in water and total vanadium in vegetable and fruit samples.

Coil-Globule Collapse of Polystyrene Chains in Tetrahydrofuran-Water Mixtures.

We study the coil and globule states of a single polymer chain in solution by performing molecular dynamics simulations with a united atom model. Specifically, we characterize the structural properties of atactic polystyrene chains with N = 20-150 monomers in tetrahydrofuran-water mixtures at varying mixing ratios. We find that the hydrophobic polymers form rather open coils when the mole fraction of water, XW, is roughly below 0.25, whereas the chains collapse into globules when XW ≳ 0.75. We confirm the theoretically expected scaling laws for the radius of gyration, Rg, in these regimes, i.e., Rg ∝ N3/5 and Rg ∝ N1/3 for good and poor solvent conditions, respectively. For poor solvent conditions with XW = 0.75, we find a sizable fraction of residual tetrahydrofuran trapped inside the collapsed polymer chains with an excess amount located at the globule surface, acting as a protective layer between the hydrophobic polystyrene and the surrounding water-rich mixture. These findings have important implications for nanoparticle fabrication techniques where solvent exchange is exploited to drive polymer aggregation, since residual solvent can significantly influence the physical properties of the precipitated nanoparticles.

Supramolecular dispersive liquid–liquid microextraction-based solidification of floating organic drops combined with electrothermal atomic absorption spectrometry for determination of chromium species

ABSTRACTA simple, sensitive and reliable method has been developed for separation and preconcentration of chromium (VI) from aqueous samples before determination by electrothermal atomic absorption spectrometry. The method is based on the extraction of the hydrophobic complex of chromium (VI) with ammonium pyrrolidine dithiocarbamate in the coacervates made up of decanoic acid reverse micelles in the water–tetrahydrofuran mixture. Parameters affecting the extraction efficiency of the analyte were studied and optimised. Under the optimum conditions, the linear range, enhancement factor, the limit of detection and limit of quantification were found to be 0.008–0.4 µg L−1, 127, and 1.8 ng L−1 and 6.0 ng L−1, of Cr(VI), respectively. The relative standard deviation at the concentration level of 0.1 µg L−1 Cr(VI) (n = 6) was 4.2%. Total chromium was determined after the oxidation of Cr(III) to Cr(VI) with permanganate in acidic medium. The method was successfully applied to the determination of chromium species in water and human serum samples.

Correlated Diffusivities, Solubilities, and Hydrophobic Interactions in Ternary Polydimethylsiloxane–Water–Tetrahydrofuran Mixtures

Bulk thermodynamic and kinetic properties of mixtures are generally composition dependent, often in complicated ways, especially for partially miscible and multicomponent systems. Combined 1H chemical shift, 1H diffusion NMR, and surface forces analyses establish the compositional dependences of water solubility and self-diffusion in ternary polymeric polydimethylsiloxane–water–tetrahydrofuran (THF) mixtures. The addition of THF significantly increases the solubility of water, while decreasing its diffusivity, in hydrophobic polydimethylsiloxane. Minimum values for the self-diffusivities of both water and THF coincide with a minimum in the hydrophobic adhesion energy between silicone polymer thin films near the same binary composition of 0.20 mole fraction THF. Such interrelated diffusivities, solubilities, and hydrophobic interactions are analyzed with respect to hydrogen bonding among the constituent species to account for the bulk physical properties of technologically important mixtures of silicone po...

Enhanced Emission of Polyethyleneimine-Coated Copper Nanoclusters and Their Solvent Effect

The solvent-dependent properties of polyethyleneimine (PEI)-capped Cu nanoclusters are discussed in this study. The PEI-encapsulated Cu nanoclusters were dispersed in 12 polar organic solvents, and in water and alcohols, the nanoclusters display similar properties and could be stable in the dark. Moreover, Cu nanoclusters exhibit a blue shift of the emission peak in tetrahydrofuran (THF) and 1,4-dioxane, and the absorption spectra change dramatically. Furthermore, in THF the fluorescence intensity increases significantly over time. Besides, the absorption spectra also display a significant change in acetonitrile, dimethyl sulfoxide, and ethylene glycol monomethyl ether, while the emission bands show no obvious shift. In acetonitrile, THF, and 1,4-dioxane, the solvents look milky under bright light, and the fluorescence colors look more blue under a UV lamp. The solvent effect on the fluorescence and absorption spectra of the PEI-capped Cu nanoclusters in water–THF mixtures at different solvent ratios is d...

Unperturbed dimensions and interaction parameters of poly(vinyl alcohol)s in water–acetone and water–tetrahydrofuran mixtures

The intrinsic viscosities [η] of poly(vinyl alcohol)s (PVAs, which are biocompatible polymers)—with different (high, medium, and low) molecular weights were measured at 293–303 K in water (good solvent)–acetone (ACE, poor solvent) and water–tetrahydrofuran (THF, poor solvent) mixtures. The results observed, particularly the values of the Huggins constant (KH), indicated that the solvency of each PVA varied as a function of solvent composition (ΦACE/ΦTHF) and temperature. The unperturbed dimensions (Kθ) of the PVAs under nontheta conditions in a variety of water–acetone and water–tetrahydrofuran solutions were also calculated using various equations. The values of Kθ obtained via three different equations, i.e., those of Burchard–Stockmayer–Fixman (BSF), Berry, and Inagaki–Suzuki–Kurata (ISK), agreed well except for a few solvent compositions. The molecular extension factor (αn) and actual end-to-end distance (αnKθ) of each PVA were also computed.

Thermodynamic Functions of Solvation of Hydrocarbons, Noble Gases, and Hard Spheres in Tetrahydrofuran-Water Mixtures.

Thermodynamic solvation properties of mixtures of water with tetrahydrofuran at 298 K are studied. The Gibbs free energies and enthalpies of solvation of n-octane and toluene are determined experimentally. For molecular dynamics simulations of the binary solvent, we have modified a TraPPE-UA model for tetrahydrofuran and combined it with the SPC/E potential for water. The excess thermodynamic functions of neon, xenon, and hard spheres with two different radii are calculated using the particle insertion method. Simulated and real systems share the same characteristic trends for the thermodynamic functions. A maximum is present on dependencies of the enthalpy of solvation from the composition of solvent at 70-90 mol % water, making it higher than in both of the cosolvents. It is caused by a high enthalpy of cavity formation in the mixtures rich with water due to solvent reorganization around the cavity, which is shown by calculation of the enthalpy of solvation of hard spheres. Addition of relatively small amounts of tetrahydrofuran to water effectively suppresses the hydrophobic effect, leading to a quick increase of both the entropy and enthalpy of cavity formation and solvation of low polar molecules.

Crystallization-induced red emission of a facilely synthesized biodegradable indigo derivative.

We report a new class of crystallization-induced red-emitting luminogen based on a synthetic biodegradable indigo derivative, Indigoid-B. This compound, upon an ultrasonic treatment, formed well-defined microcrystals that showed striking crystallization-induced emission (CIE) in mixed solvents of tetrahydrofuran-water.

Micellar Dispersive Liquid–Liquid Microextraction for Preconcentration of Cu(I) in Environmental Samples

Micelle-based dispersive liquid–liquid microextraction was used for preconcentration of trace amounts of copper prior to its determination by flame atomic absorption spectrometry. The copper ions were micro-extracted using coacervates, composed of reverse micelles of decanoic acid, and were dispersed in tetrahydrofuran–water mixtures. The method involves the partitioning of the metal chelates, produced from the reaction of Cu(I) and bisoxazoline in acidic medium, and the combination of dispersive liquid–liquid microextraction with coacervation-based microextraction. It combines the advantages of dispersive liquid–liquid microextraction with those based on coacervation and reverse micelles. All of the critical parameters affecting the analytical performance were studied. Under the optimum conditions, the enhancement factor was determined to be 30.0. The detection limit and precision were determined to be 1.6 μg/L and 3.2 % (n = 6, 200 μg/L), respectively. The accuracy of the developed method was evaluated by analyzing a certified reference material and was applied for analysis of water and vegetable samples, successfully.

How Do Liquid Mixtures Solubilize Insoluble Gelators? Self-Assembly Properties of Pyrenyl-Linker-Glucono Gelators in Tetrahydrofuran–Water Mixtures

The self-assembly behavior of a series of glucono-appended 1-pyrenesulfonyl derivatives containing α,ω-diaminoalkane spacers (Pn, where n, the number of methylene units separating the amino groups, is 2, 3, 4, 6, 7, and 8) in v:v tetrahydrofuran (THF):water mixtures is examined at room temperature. The Pn at 2 w/v % concentrations do not dissolve in either THF or water at room temperature. However, the Pn can be dissolved in some THF:water mixtures, and they form gels spontaneously in other compositions without dissolving completely. The self-assembly of the Pn in the liquid mixtures has been investigated using a variety of techniques. The particle sizes of the Pn in their solutions/sols, critical gelation concentrations, microstructures, thermal and mechanical stabilities of the gels, and molecular packing modes of Pn molecules in their gel networks are found to be very dependent on the composition of the liquid mixtures. Correlations between the self-assembly behavior of the Pn and the polarity of the liquid mixtures, as probed by E(T)(30) and Hansen solubility parameters, yield both qualitative and quantitative insights into why self-assembly of the Pn can or cannot be achieved in different liquid compositions. As revealed by UV-vis and fluorescence spectroscopy studies, π-π stacking of the pyrenyl groups occurs as part of the aggregation process. Correlations between the rheological properties of the gels and the Hansen solubility parameters of the Pn and the solvent mixtures indicate that hydrogen-bonding interactions are a major contributor to the mechanical stability. Overall, the results of this study offer a new strategy to investigate the balance between dissolution and aggregation of molecular gelators. To the best of our knowledge, this is the first example of the spontaneous formation of molecular gels without heating by placing gelators in mixtures of liquids in which they are insoluble in the neat components.

Supramolecular dispersive liquid–liquid microextraction based solidification of floating organic drops for speciation and spectrophotometric determination of chromium in real samples

A novel, sensitive and inexpensive supramolecular dispersive liquid–liquid microextraction method based on the solidification of floating organic drops (SM-DLLME-SFO) has been proposed for the speciation and preconcentration of trace quantities of chromium as a precursor to its determination by UV-Vis spectrophotometery for the first time. The chromium ions are micro-extracted with coacervates composed of reverse micelles formed using decanoic acid and dispersed in tetrahydrofuran–water mixtures. THF plays a double role, as a dispersing solvent and also in the self-assembly of decanoic acid. The method involves the partitioning of the metal chelates, produced from the reaction of Cr(VI) with diphenylcarbazide and sodium dodecyl sulfate in an acidic medium and a combination of SM-DLLME with the solidification of floating organic drops. It combines the advantages of dispersive liquid–liquid microextraction with those based on coacervation and reverse micelles and solidification. All the critical parameters affecting the analytical performance were studied. Under the optimum conditions, the enhancement factor was 50. The detection limit and precision (RSD) were 0.23 μg L−1 and 3.8% (n = 6), respectively. The accuracy of the developed method was evaluated by analyzing a certified reference material and applied successfully to the analysis of several water samples.