Alcohol-water Binary Mixtures Research Articles

Hydrogen bond structure and associated dynamics in micro-heterogeneous and in phase separated alcohol-water binary mixtures: A THz spectroscopic investigation

Despite being a simple and widely studied solution, a correlation between the structure and dynamics of the hydrogen bond (HBond) network in alcohol-water binary mixtures remains highly debatable. The present work combined Terahertz time domain spectroscopy (TTDS) and Terahertz-Fourier transform infrared (THz-FTIR) spectroscopy covering a wide frequency window of 0.3–18 THz, which probes most of the intermolecular roto-vibrational modes of water, to extract an extensive idea on such aspect of the binary mixtures. This study demonstrates a unified picture of the solute concentration-dependent HBond network structure and its associated dynamics in alcohol-water binary mixtures considering micro- and macro-scale (for partially water-soluble alcohols) phases present inside the systems. The work extensively took into account both the factors of hydrophobic chain length and macroscopic self-aggregation of alcohols to present a comprehensive view of HBonded intermolecular networks in binary mixtures. We found a balance between the local homo-molecular and cross-molecular solvation which leads to a micro/macro scale self-aggregation for various alcohol-water mixtures.

Complex formation and microheterogeneity in water–alcohol binary mixtures investigated by solvatochromic study

Complex formation and microheterogeneity in water–alcohol binary mixtures investigated by solvatochromic study

Facile on-site quality monitoring of alcohol based hand sanitizers by phase separation and color development with butyl acetate-crystal violet mixture

Amidst the unprecedented demand for alcohol based hand sanitizers in the wake of the continuing onslaught of COVID-19 pandemic, a simple and rapid method for identifying spurious or non-conforming products is the need of the hour. Accordingly, a visual colorimetric method for the detection of methanol based hand sanitizers and also for the semi-quantitative determination of ethanol or propanol in ethanol or propanol based products is developed. Methanol based sanitizers pose a serious threat to human health while ethanol or propanol based sanitizers containing <60% (v/v) alcohol are poor disinfectants. Taking cognizance of the fact that alcohol and water account for >95% volume of sanitizers, the method utilizes the alcohol dependent miscibility of alcohol-water binary mixtures in n-butyl acetate for analysis. The phase separations in the alcohol:water:n-butyl acetate ternary mixtures are quantitatively identified through colour contrast developed by the addition of crystal violet. The method has been applied to several commercially available liquid and also gel type sanitizers. It works well for colorless as well as coloured sanitizers. It is simple and can be used for selecting the right kind of hand sanitizers.

On the Correlation between Pair Hydrophobicity and Mixing Enthalpies in Water-Alcohol Binary Mixtures.

In this article, we have explored the extent of pair hydrophobicity in water-alcohol binary mixtures upon varying the chain length of the alcohol at several compositions. We have measured the pair hydrophobicity in water-methanol, water-propanol, and water-butanol mixtures. The pair hydrophobicity is measured by the depth of the first minimum (contact minimum) in the potential of mean force profile between a pair of neopentanes. In the case of water-methanol mixtures, the pair hydrophobicity is highest at xMeOH = 0.25, whereas in water-propanol mixtures, it is highest at xPrOH = 0.07, and in water-butanol mixture pair, hydrophobicity is highest at even lower alcohol concentration (xBuOH = 0.03). This indicates that as we increase the chain length of alcohol, the composition at which pair hydrophobicity is highest shifts toward a lower alcohol composition of the binary mixture. We have shown that the composition dependence of pair hydrophobicity echoes the trend observed in the calculated composition dependence of the enthalpy of mixing of the alcohol-water binary mixtures. The association pattern of the hydrophobic part of the alcohol also shows a change in trend around similar alcohol compositions. The hydrogen bond pattern around the alcohol rather than water exhibits a change in trend around those compositions. These results will improve our understanding of the composition-dependent phenomena of biomolecular processes in aqueous binary mixtures.

Co-Nonsolvency Transition of Poly(N-isopropylacrylamide) Brushes in a Series of Binary Mixtures

Co-nonsolvency occurs if a mixture of two good solvents causes the collapse or demixing of polymers into a polymer-rich phase in a certain range of compositions of these two solvents. In this work, we systematically study the co-nonsolvency behavior of poly(N-isopropylacrylamide) brushes of different grafting densities in a series of alcohol–water binary mixtures with increasing hydrophobic parts ranging from methanol to 1-butanol by using ellipsometry. We report a strong collapse transition by increasing the alcohol concentration in the water-rich phase, which is enhanced for longer-chain alcohols. The analysis of the thermodynamic properties of the alcohol–water series displays that an increasing demixing tendency between alcohol and water is correlated with an enhancement of the collapse transition of the brush. The increase of grafting density weakens the transition behavior but does not shift the solvent composition point of maximum brush collapse, which is in agreement with the predictions of a rece...

Virtual Sensor Using Neural Networks in Batch Distillation of Fermented Beverages

The main purpose of controlling the distillation process is to maintain the composition of the products in an intended specification in order to optimize operating costs and meet market requirements. Line analyzers and laboratory analysis are generally used for composition information. However, such alternatives are expensive, do not provide information in real time and are not always feasible or available. In this context, soft sensors emerge as a cheaper alternative. The aim of this work is to develop a soft sensor to infer online the ethanol content in the products of a batch distillation process of watermelon wine, based on temperature measurements. The developed model consists in a multilayer perceptron artificial neural network with one hidden layer. The Levenberg-Marquardt algorithm was used to optimize the weights. In order to train and validating the ANN, real distillation data of water-alcohol binary mixtures with initial compositions similar to the watermelon wine used. The simulation was also validated with real data of wine distillations. The RMSE was applied in the performance evaluation of the model and its result was 0.029 in mass fraction, showing the feasibility of its use as a soft sensor.

Polarization induced control of optical trap potentials in binary liquids

We illustrate control of a polarized laser optical trapping potential landscape through the nonideal mixing of binary liquids. The inherent trapping potential asymmetry (ITPA) present in the trapping region results from the asymmetric intensity distribution in focal volume due to the high numerical aperture objective lens. Experimentally, we show that this ITPA effect can be modified and/or removed by the use of binary liquid mixtures. From our femtosecond optical tweezers experiments, we determine the topograph of the trapping potential base on the fluctuation-dissipation theorem. Additionally, the Brownian motion of the trapped bead is sensitive to the frictional force (FF) of the surroundings that is exerted by clusters of water and alcohol binary mixture through extended hydrogen bonding. Thus, using these two effects, ITPA and FF of the medium, we have shown that one can indeed modify the effective trapping potential landscape. Water-alcohol binary mixtures display a nonlinear dependence on the microrheological properties of the solvent composition as a result of rigid cluster formation. Volumetrically, at about 30% methanol in water binary mixture, the trapping asymmetry is minimal. In this particular binary mixture composition, the hydrophobic part of the methanol molecule is surrounded by ‘cages’ of water molecules. Enhanced H-bonding network of water molecules results in higher viscosity, which contributes to the higher frictional force. Increased viscosity decreases the degree of anisotropy due to hindered dipolar rotation. However, at higher methanol concentrations, the methanol molecules are no longer contained within the water cages and are free to move, which decrease their overall bulk viscosity. Thus, for pure solvents, experimentally measured anisotropy matches quite well with the theoretical prediction, but this fails in case of the binary mixtures due to the increased frictional force exerted by binary mixtures that result from the formation of cage-like structures.

Temperature-Dependent Segregation in Alcohol-Water Binary Mixtures Is Driven by Water Clustering.

Previous neutron scattering work, combined with computer simulated structure analysis, has established that binary mixtures of methanol and water partially segregate into water-rich and alcohol-rich components. It has furthermore been noted that, between methanol mole fractions of 0.27 and 0.54, both components, water and methanol, simultaneously form percolating clusters. This partial segregation is enhanced with decreasing temperature. The mole fraction of 0.27 also corresponds to the point of maximum excess entropy for ethanol-water mixtures. Here, we study the degree of molecular segregation in aqueous ethanol solutions at a mole fraction of 0.27 and compare it with that in methanol-water solutions at the same concentration. Structural information is extracted for these solutions using neutron diffraction coupled with empirical potential structure refinement. We show that ethanol, like methanol, bi-percolates at this concentration and that, in a similar manner to methanol, alcohol segregation, as measured by the proximity of neighboring methyl sidechains, is increased upon cooling the solution. Water clustering is found to be significantly enhanced in both alcohol solutions compared to the water clustering that occurs for random, hard sphere-like, mixing with no hydrogen bonds between molecules. Alcohol clustering via the hydrophobic groups is, on the other hand, only slightly sensitive to the water hydrogen bond network. These results support the idea that it is the water clustering that drives the partial segregation of the two components, and hence the observed excess entropy of mixing.

Effect of Microheterogeneity of Different Aqueous Binary Mixtures on the Proton Transfer Dynamics of [2,2'-Bipyridyl]-3,3'-diol: A Femtosecond Fluorescence Upconversion Study.

In this article, we have investigated the excited-state intramolecular double proton transfer dynamics of [2,2′-bipyridyl]-3,3′-diol, BP(OH)2, in three alcohol–water binary mixtures, namely, ethanol (EtOH)–water, n-propanol (PrOH)–water, tert-butyl alcohol (TBA)–water, and dimethyl sulfoxide (DMSO)–water utilizing the femtosecond fluorescence upconversion technique. We have found that in alcohol–water binary mixtures the proton transfer (PT) pathway of BP(OH)2 is sequential and the anomalous slowdown in PT dynamics is observed in mole fraction (χ) ranges χEtOH = 0.04–0.07, χEtOH = 0.23–0.28, χPrOH = 0.17–0.30, χTBA = 0.12–0.21, and χTBA = 0.40–0.46. Our study sheds light on the involvement of water network in the PT dynamics. Reduction in water accessibility due to the involvement of water molecules in cluster formation results in hindered PT dynamics, and this retardation is more for the TBA–water binary mixture compared to that for the other two mixtures. Additionally, we have found two anomalous regions for the DMSO–water binary mixture in ranges χDMSO = 0.12–0.16 and χDMSO = 0.26–0.34. However, most interestingly, beyond χDMSO = 0.40, we do not find any growth component in the femtosecond fluorescence upconversion trace, which may be due to the change in the PT mechanism from a sequential water-mediated pathway to a concerted intramolecular pathway.

Miniaturized Temperature-Controlled Planar Chromatography (Micro-TLC) as a Versatile Technique for Fast Screening of Micropollutants and Biomarkers Derived from Surface Water Ecosystems and During Technological Processes of Wastewater Treatment.

There is increasing interest in the development of simple analytical systems enabling the fast screening of target components in complex samples. A number of newly invented protocols are based on quasi separation techniques involving microfluidic paper-based analytical devices and/or micro total analysis systems. Under such conditions, the quantification of target components can be performed mainly due to selective detection. The main goal of this paper is to demonstrate that miniaturized planar chromatography has the capability to work as an efficient separation and quantification tool for the analysis of multiple targets within complex environmental samples isolated and concentrated using an optimized SPE method. In particular, we analyzed various samples collected from surface water ecosystems (lakes, rivers, and the Baltic Sea of Middle Pomerania in the northern part of Poland) in different seasons, as well as samples collected during key wastewater technological processes (originating from the "Jamno" wastewater treatment plant in Koszalin, Poland). We documented that the multiple detection of chromatographic spots on RP-18W microplates-under visible light, fluorescence, and fluorescence quenching conditions, and using the visualization reagent phosphomolybdic acid-enables fast and robust sample classification. The presented data reveal that the proposed micro-TLC system is useful, inexpensive, and can be considered as a complementary method for the fast control of treated sewage water discharged by a municipal wastewater treatment plant, particularly for the detection of low-molecular mass micropollutants with polarity ranging from estetrol to progesterone, as well as chlorophyll-related dyes. Due to the low consumption of mobile phases composed of water-alcohol binary mixtures (less than 1 mL/run for the simultaneous separation of up to nine samples), this method can be considered an environmentally friendly and green chemistry analytical tool. The described analytical protocol can be complementary to those involving classical column chromatography (HPLC) or various planar microfluidic devices.

Clay-Alcohol-Water Dispersions: Anomalous Viscosity Changes Due to Network Formation of Clay Nanosheets Induced by Alcohol Clustering.

Clay-alcohol-water ternary dispersions were compared with alcohol-water binary mixtures in terms of viscosity and optical absorbance. Aqueous clay dispersions to which lower alcohols (ethanol, 1-propanol, 2-propanol, and tert-butanol) were added exhibited significant viscosity anomalies (maxima) when the alcohol content was 30-55 wt %, as well as optical absorbance anomalies (maxima). The maximum viscosity (ηmax) depended strongly on the clay content and varied between 300 and 8000 mPa·s, making it remarkably high compared with the viscosity anomalies (2 mPa·s) observed in alcohol-water binary mixtures. The alcohol content at ηmax decreased as the hydrophobicity of the alcohol increased. The ternary dispersions with viscosity anomalies exhibited thixotropic behaviors. The effects of other hydrophilic solvents (glycols) and other kinds of clays were also clarified. Based on these findings and the average particle size changes, the viscosity anomalies in the ternary dispersions were explained by alcohol-clustering-induced network formation of the clay nanosheets. It was estimated that 0.9, 1.7, and 2.5 H2O molecules per alcohol molecule were required to stabilize the ethanol, 2-propanol, and tert-butanol, respectively, in the clay-alcohol-water dispersions.

Picosecond Solvation and Rotational Dynamics: An Attempt to Reinvestigate the Mystery of Alcohol-Water Binary Mixtures.

In this article, we have investigated the anomalous behavior of two alcohol-water (tert-butyl alcohol (TBA)-water and ethanol-water) binary mixtures using femtosecond fluorescence upconversion technique. Recently, Gupta and Patey (Gupta, R.; Patey, G. N. J. Chem. Phys. 2012, 137, 034509(1)-034509(12)) have used four force fields to simulate TBA-water binary mixtures. Surprisingly, two of them do not identify any aggregation of TBA molecules. We have calculated average solvation time of Coumarin 480 (C480) using two different methods. Our results indicate slowdown in solvation time in the mole fraction ranges XT = 0.09-0.15, XT = 0.40-0.46 and XE = 0.06-0.08, XE = 0.20-0.25 for TBA-water and ethanol-water binary mixtures, respectively. Additionally, we have detected another anomalous region at XT ∼ 0.03. Slow solvation responses in the ranges XT = 0.40-0.46 and XE = 0.20-0.25 are probably due to the higher shear viscosity of the medium. However, XT = 0.09-0.15 and XE = 0.06-0.08 are the manifestation of aggregation induced structural transition of alcohol molecules. Hindered rotation of C480 in the ranges XT = 0.04-0.09 and XE = 0.03-0.07 corroborates our solvation dynamics results. From temperature dependent anisotropy measurements, we have shown that aggregation of alcohol molecules increases with increase in temperature.

Micellisation thermodynamics of sodium lauroylsarcosinate in water–alcohol binary mixtures

Aggregation of sodium lauroylsarcosinate (SLS) in aqueous solutions of methanol, ethanol, propanol and ethylene glycol at 288–313 K has been determined from conductivity measurement in the range 0–20% v/v of additives. The precise values of the critical micelle concentration (CMC) and the degree of counter-ion dissociation of micelles were obtained at each temperature by fitting the specific conductivity-surfactant concentration curve to the integrated form of the Boltzmann-sigmoid equation. The CMC was found to increase with increase in additive concentrations in the case of methanol and ethylene glycol, while it decreases with increase in ethanol and propanol concentration. The equilibrium model of micelle formation was applied to obtain the thermodynamic parameters of micellisation. The Gibbs free energies were observed to vary only slightly with temperature and additive concentrations. Enthalpy–entropy compensation was observed for all the systems with a constant compensation temperature of ≈300 K and negative compensation enthalpy.

Molecular clustering inherent in the liquid state: Effect of relativity in intermolecular interaction energy

In alcohol–water binary mixtures, microheterogeneous clustering creates a non-ideal mixture. This molecular clustering in the binary mixture is controlled by relativity in the intermolecular interaction energies. This relativity-controlled clustering is inherent to the liquid state, irrespective of whether the solution is aqueous or non-aqueous. The vapor–liquid equilibrium for alcohol–water binary mixtures which represents non-ideality is correlated to relativity-controlled clustering. This paper was reviewed on the basis of our reported results, and presented at the 2012 EMLG/JMLG Annual Meeting in Eger.

High-temperature vapour–liquid equilibrium for the water–alcohol systems and modeling with SAFT-VR: 1. Water–ethanol

Linear alcohols represent an important alternative source of energy. The design of industrial processing equipment of these alcohols needs accurate vapour–liquid equilibrium (VLE) measurements of binary mixtures with water at high temperatures.A flow apparatus was built to carry out vapour–liquid equilibrium at high temperatures for water–alcohol binary mixtures in the temperature range of 363–443K and pressures up to 1.7MPa. Experimental VLE data are presented for water–ethanol system for temperatures between 363.3 and 423.7K, and pressures up to 1MPa and compared with available literature data. Its performance was found to be commensurate with the design parameters and the required accuracy.The statistical associating fluid theory for potentials of variable range (SAFT-VR) was used to correlate the data. The phase equilibria for this system are accurately described with this approach, especially considering that the parameters were obtained for a shorter region of the phase diagram.

Temperature-controlled micro-TLC: A versatile green chemistry and fast analytical tool for separation and preliminary screening of steroids fraction from biological and environmental samples

This paper is a continuation of our previous research focusing on development of micro-TLC methodology under temperature-controlled conditions. The main goal of present paper is to demonstrate separation and detection capability of micro-TLC technique involving simple analytical protocols without multi-steps sample pre-purification. One of the advantages of planar chromatography over its column counterpart is that each TLC run can be performed using non-previously used stationary phase. Therefore, it is possible to fractionate or separate complex samples characterized by heavy biological matrix loading. In present studies components of interest, mainly steroids, were isolated from biological samples like fish bile using single pre-treatment steps involving direct organic liquid extraction and/or deproteinization by freeze-drying method. Low-molecular mass compounds with polarity ranging from estetrol to progesterone derived from the environmental samples (lake water, untreated and treated sewage waters) were concentrated using optimized solid-phase extraction (SPE). Specific bands patterns for samples derived from surface water of the Middle Pomerania in northern part of Poland can be easily observed on obtained micro-TLC chromatograms. This approach can be useful as simple and non-expensive complementary method for fast control and screening of treated sewage water discharged by the municipal wastewater treatment plants. Moreover, our experimental results show the potential of micro-TLC as an efficient tool for retention measurements of a wide range of steroids under reversed-phase (RP) chromatographic conditions. These data can be used for further optimalization of SPE or HPLC systems working under RP conditions. Furthermore, we also demonstrated that micro-TLC based analytical approach can be applied as an effective method for the internal standard (IS) substance search. Generally, described methodology can be applied for fast fractionation or screening of the whole range of target substances as well as chemo-taxonomic studies and fingerprinting of complex mixtures, which are present in biological or environmental samples. Due to low consumption of eluent (usually 0.3–1 mL/run) mainly composed of water–alcohol binary mixtures, this method can be considered as environmentally friendly and green chemistry focused analytical tool, supplementary to analytical protocols involving column chromatography or planar micro-fluidic devices.

Azeotropy of alcohol–water mixtures from the viewpoint of cluster-level structures

We showed that there is a close relation between evaporation properties and cluster-level structures in alcohol–water binary mixtures, on the basis of the mass spectrometric analyses of clusters generated through fragmentation of liquid droplets. The azeotropy for alcohol (ethanol, 1-propanol or 1-butanol)–water mixtures is caused by the change of the evaporation properties attributed to the cluster-level structures in the mixtures. When the hydrogen-bonding network of water molecules is stable at the cluster level in the water-rich mixtures, the alcohol molecules included in the water-rich clusters are evaporated primarily. On the other hand, when the alcohol self-association clusters are formed with an increase of the alcohol concentration in the mixtures, evaporation of the water existing around the alcohol self-association clusters is increased.

Kinetics of malachite green fading in alcohol–water binary mixtures

AbstractThe rate constant of alkaline fading of malachite green (MG+) was studied in alcohol–water binary mixtures. This reaction was studied under pseudo‐first‐order conditions at 283–303 K. It was observed that the reaction rate constants were increased in the presence of different weight percentages of methanol, ethanol, 1‐propanol, 2‐propanol, ethylene glycol, 1,2‐propanediol, and glycerol (up to 19.3%). In aqueous glycerol solutions higher than 19.3%, the rate constant of reaction slightly decreases, which is due to high viscosity values of solvent mixtures. The fundamental rate constants of MG+ fading in these solutions were obtained by using the SESMORTAC model. Owing to the charged character of activated complex, with an increase in the weight percentage of the used cosolvents or temperature, k2 values change according to the trend of hydroxide ion nucleophilic parameter values. Also, using MG+ solvatochromism, a simple test, called MAGUS, is introduced for measuring the glycerol concentration in its aqueous solutions. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 508–518, 2010

Super alcohol-absorbent gels of sulfonic acid-contained poly(acrylic acid)

Alcohol-specific superabsorbing gels (super-alcogels) based on non-neutralized acrylic acid (AA, 60–94 mol%) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) were prepared via solution polymerization in water. Polyethylene glycol dimethacrylate and potassium persulfate were used as crosslinker and initiator, respectively. Characterization of samples was performed using FTIR, 1H-NMR and thermomechanical analyses. Glass transition temperature and modulus of dried samples were found to be directly changed with their AA content. The gels exhibited enormous ability for absorbing and retaining a variety of mono- and poly-hydric alcohols. For example, in lieu of one gram of a typical sample composing 25 mol% AMPS, its absorption capacity was measured to be 53.0 g methanol, 42.1 g ethanol, 12.1 g n-propanol, 3.4 g iso-propanol, 41.2 g ethylene glycol, 20.7 g propylene glycol, 37.8 g 1,3-propanediol and 32.9 g glycerol. The absorbencies were superior to those of a known commercial poly(AA) sample, Carbopol. The alcohol absorbency was improved with increase of AMPS incorporated. It was recognized to be dependant on the alcohol characteristics such as H-bonding ability, OH/C ratio, electronic features (e.g. dielectric constant), steric hindrance of the neighboring groups of the solvent OH group, as well as the solvent viscosity. Normal phase transitions were observed in the gel swelling behavior in the alcohol-water binary mixtures. Rheological measurements of the water-swollen gel showed that more AMPS content resulted in gels with inferior storage modulus. All the empirical observations were discussed based on the related physicochemical principles.

Adsorption of triton X-100 on silica gel: effects of temperature and alcohols

Abstract Adsorption of Triton X-100 (TX-100) on silica gel has been studied as a function of temperature (308–328 K) and composition for mixtures of water with ethanol or t-butanol. The adsorption capacity of silica gel for TX-100 decreases with increase in alcohol content. Adsorption isotherms of TX-100 on silica gel are four-region and were analyzed using the ARIAN (adsorption isotherm regional analysis) model. Data in regions 2, 3 and 4 were fitted to the Temkin, bilayer and reverse desorption isotherms, respectively. The results show that adsorption of TX-100 on silica gel in water and alcohol-water binary mixtures occurs mainly through formation of monolayer surface aggregates or low bilayer coverage.