Mixed Solvent Media Research Articles

Pitzer and Pitzer–Simonson–Clegg Modeling Approaches: Ternary HCl + 2-Propanol + Water Electrolyte System

Despite its success for modeling electrolyte thermodynamics in aqueous media, the use of the Pitzer approach for the investigation of electrolytes in nonaqueous or in mixed solvent media is still very limited. Further, a review of the literature reveals that there are no more than a few research groups who have used the exact form of the Pitzer–Simonson–Clegg (PSC) ion-interaction approach for the investigation of electrolytes in mixed solvent systems. As a continuation of our previous studies, the present investigation reports modeling of HCl in the 2-propanol + water mixed solvent system with the Pitzer, PSC and an extended form of the PSC ion-interaction approaches using the experimental potentiometric data from a cell containing pH glass membrane and Ag/AgCl electrodes. The electrochemical measurements were performed over the HCl molality range from 0.01 to 4.5 mol⋅kg−1 in mixed 2-propanol (x%)+water (100−x%) solvents, with different solvent percent mass fractions (x%=10,20,30,40 and 50%) at 298.15±0.05 K.

Mn-Substituted [Zn1−xMnxSe](DETA)0.5 (x = 0−0.3) Inorganic−Organic Hybrid Nanobelts: Synthesis, Electron Paramagnetic Resonance Spectroscopy, and Their Temperature- and Pressure-Dependent Optical Properties

Mn-substituted 1D [Zn1−xMnxSe](DETA)0.5(DETA = diethylenetriamine, x = 0−0.3) inorganic−organic hybrid nanobelts have been synthesized by a solvothermal reaction in a mixed solvent media. Strong Mn2+ internal transition (4T1 → 6A1) emission peaks at 585 nm (2.12 eV) are detected at room temperature photoluminescence (PL) spectra, and the highest emission intensity is obtained when the nominal Mn content x = 0.15. Temperature- and pressure-dependent photoluminescent properties as well as the electron paramagnetic resonance (EPR) spectra of [Zn1−xMnxSe](DETA)0.5 nanobelts have been studied for the first time. Temperature-dependent PL spectra show that the lower the temperature, the higher the intensity of the emission intensity. Under high pressure, a large red shift of Mn2+-related orange luminescence is observed and luminescent intensity is greatly decreased as the pressure increases to 10.5 GPa. Pressure dependence of the Mn2+ PL integrated intensity and energy have the same kink point at 2.54 GPa, which...

Pitzer and Pitzer–Simonson–Clegg modeling approaches: Ternary HCl + 1-propanol + water electrolyte system

A survey of literature reveals that the use of Pitzer approach for modeling electrolyte in nonaqueous or in mixed solvent media is still very scarce. Moreover, only two research groups have used the exact and complete form of the more refined Pitzer–Simonson–Clegg (PSC) ion-interaction approach for the investigation of electrolyte in mixed solvent systems. The present investigation describes the results obtained by the use of Pitzer, PSC as well as an extended PSC ion-interaction approaches for modeling the non-ideal behavior of the ternary HCl + water + 1-propanol systems. These modeling purposes were achieved based on the experimental potentiometric data of a galvanic cell containing a pH glass membrane and Ag/AgCl electrodes. The measurements were performed over the HCl electrolyte molality ranging from 0.01 up to 4.5 mol kg −1 in the ternary HCl + 1-propanol ( x%) + water (100 − x%) system with different alcohol percent mass fractions ( x% = 10, 20, 30, 40 and 50%), at 298.15 ± 0.05 K.

New Blue‐Light‐Emitting Ultralong [Cd(L)(TeO3)] (L=polyamine) Organic–Inorganic Hybrid Nanofibre Bundles: Their Thermal Stability and Acidic Sensitivity

A new type of blue-light-emitting ultralong [Cd(L)(TeO(3))] (L = ethylenediamine, diethylenetriamine) nanofibre bundle has been synthesised under reflux in a mixed solvent media. Inorganic Cd(TeO(3)) layers are assumed to exist in the structures and are connected by the organic amine molecules through the coordination between nitrogen atoms and cadmium ions. The composition and formulae of these hybrid materials, based on the proposed structures, have been identified through element analysis (EA), thermal gravity analysis (TGA) and energy dispersive spectra (EDS). The thermal stabilities and optical properties of these nanofibre bundles have been investigated. Thermal decomposition of [Cd(en)(TeO(3))] (en = ethylenediamine) and [Cd(DETA)(TeO(3))] (DETA = diethylenetriamine) at 450 degrees C allowed the formation of a mixture of CdTe and Cd(TeO(3)) phases, and a pure CdTe phase, respectively. In addition, this new kind of hybrid bundle, which demonstrates blue emission, was found to be sensitive to acids, and the emission intensity is strongly dependent on the acidity of the solutions, implying that these hybrid nanofibre bundles could be potentially applied as acid sensors.

Polymer-mediated mesoscale mineralization

Polymer-controlled mineralization in aqueous solution or in a mixed solvent media, as well as its combination with the interface of air-water can lead to the formation of minerals with unique structures and morphologies, which sheds light on the possibility to mimic the detailed structures of the natural minerals.

Rank deficiency in spectrophotometric study of acid dissociation equilibria in mixed solvent media

A methanol/water mixture, although considered a binary system, does not conform to solute distribution theory. Moreover, similar shortcomings are encountered in studies concerning acid-base reactions in mixtures of these two components. We demonstrate that in mixtures of methanol/water and an acid-base dye as indicator, three components exist for each of the protonated and deprotonated forms. In contrast, analysis of spectrophotometric data obtained from pH-metric titration of the dye in mixtures of methanol/water, shows no more than one component for each form of the dye. This can only be interpreted as a rank deficiency in the acquired data. We used matrix augmentation strategy for eliminating rank deficiency and constructing the corresponding full rank data matrices. In addition, concentration and spectral profiles of the components were obtained using multivariate curve resolution-alternating least squares.

Electrical Conductances of Tetrabutylammonium Bromide, Sodium Tetraphenylborate, and Sodium Bromide in Ethylene Glycol (1) + Water (2) Mixtures at (298.15, 303.15, 308.15, and 318.15) K

The electrical conductances of solutions of tetrabutylammonium bromide (Bu4NBr), sodium tetraphenylborate (NaBPh4), and sodium bromide (NaBr) in ethylene glycol (EG) (1) + water (2) mixed solvent media containing 0.10, 0.20, and 0.30 mass fractions of EG (w1) have been reported at (298.15, 303.15, 308.15, and 318.15) K. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA), and the association diameter (R). The ionic contributions to the limiting molar conductances have been estimated using tetrabutylammonium tetraphenylborate (Bu4NBPh4) as the “reference electrolyte”. All of these three electrolytes are found to exist as free ions in the present solvent mixtures within the temperature range from (298.15 to 318.15) K. Although the association constants of the electrolytes do not vary significantly as a function of temperature, the limiting molar conductances of the electrolytes as well as the single-ion conductivity values increase appreciably with temperature.

Thermodynamic and Interfacial Adsorption Studies on the Micellar Solutions of Alkyltrimethylammonium Bromides in Ethylene Glycol (1) + Water (2) Mixed Solvent Media

Micellization behavior of three alkyltrimethylammonium bromides, viz., hexadecyl-, tetradecyl-, and dodecyltrimethylammonium bromide (CTAB, TTAB, and DTAB, respectively) in ethylene glycol (EG) (1)...

Dynamic Nuclear Polarization in Suspensions Consisting of Pure and Mixed Chlorobenzene and Pyridine and Asphaltene Extracted from Asphalt Cement with Penetration Grad 60

The Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in pure and mixed chlorobenzene and pyridine at a low magnetic field of 1.44 mT and in four different temperatures (− 10, 7, 23, and 38°C). The asphaltene was extracted from asphalt cement with penetration grad 60. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the suspending fluid medium and the unpaired electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. For all suspending fluid media used in this work, the dipole-dipole interaction is predominant due to the negative signal enhancements. In all temperatures, the dipolar part is the smallest (− 9.17) for pure pyridine solvent medium at − 10°C and the highest (− 38.2) for pure chlorobenzene solvent medium at 38°C and between these two limits for mixed solvent media at all temperatures.

Thermodynamic properties of solutions of sodium di-hydrogen phosphate in (1-propanol + water) mixed-solvent media over the temperature range of (283.15 to 303.15) K

The apparent molar volume and apparent molar isentropic compressibility of solutions of sodium di-hydrogen phosphate (NaH 2PO 4) in (1-propanol + water) mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported over the range of temperature (283.15 to 303.15) K at 5 K intervals. The results were fitted to a Redlich–Mayer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution were also calculated at the working temperature. The results show a positive transfer volume of NaH 2PO 4 from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of NaH 2PO 4 in aqueous 1-propanol solutions is negative and it increases with increasing the concentration of NaH 2PO 4, 1-propanol, and temperature. Electrical conductivity and refractive index of the solutions are also studied at T = 298.15 K. The effects of the electrolyte concentration and relative permittivity of the medium on the molar conductivity were also investigated.

Electrical conductances of tetrabutylammonium bromide and tetrapentylammonium bromide in 2-ethoxyethanol + water mixtures at 308.15, 313.15, 318.15 and 323.15 K

The electrical conductances of the solutions of tetrabutylammonium bromide (Bu4NBr), and tetrapentylammonium bromide (Pen4NBr) in 2-ethoxyethanol (1) + water (2) mixed solvent media containing 0.25, 50 and 0.75 mass fractions of 2-ethoxyethanol (w 1) have been reported at 308.15, 313.15, 318.15 and 323.15 K. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ0), the association constant (K A) and the association diameter (R). These two electrolytes are found to exist essentially as free ions in the solvent mixtures with w 1 = 0.25 and 0.50 over the entire temperature range; however, slight ionic association was observed in the mixed solvent medium richest in 2-ethoxyethanol. The electrostatic ion–solvent interaction is found to be very weak for the tetraalkylammonium ions in the aqueous 2-ethoxyethanol mixtures investigated.

A chelating resin as a probe for the copper(II) distribution in grape wines

Presented hereafter is the pilot-study of the applicability of resin titration (RT) to mixed solvents in regard to the studies of metal distribution in wines – a beverage that has attracted great attention and that has been extensively studied in the recent years. The RT method of studying the distribution of species is based on the determination of the concentration of metal ions sorbed on the iminodiacetic resin Chelex 100 at different V/ w (solution volume/mass of resin). The total metal ion present in the considered solution and the free metal ion are estimated from the titration curves. The method, already applied for water solutions, was tested here in mixed solvent media, at the pH around 3, with known amounts of copper(II) and ligands with different complexing properties. Satisfactory results have been obtained and commented critically. In the application of the RT method, the protonation and the exchange reactions of copper(II) with the considered sorbent were investigated in 12% ethanol, in KCl 0.1 and 1.0 M solutions, according to a well established procedure. Finally, a white grape wine (Riesling) from a winery in Oltrepò Pavese was analyzed with RTs. In the sample obtained before processing the wine, 50% of the total Cu(II) (∼18 μM) was combined with ligands with log α M equal to 3.3; in the final product, the total Cu(II) was 4 μM, almost totally complexed. According to these findings, the ligands accountable for the copper complexation were not the major components in the wine, as they formed considerably weaker complexes.

Dielectric constant dependence of formation constants: complexation of dioxovanadium(V) with cysteine

The complexation of dioxovanadium(V) with L-cysteine was investigated in mixed solvent systems of methanol + water and dioxane + water at 25°C and 0.1 mol dm−3 ionic media, using a combination of potentiometric and spectrophotometric techniques. Sodium perchlorate solution was used to maintain the ionic strength. The compositions of the formed complexes were determined, and it was shown that dioxovanadium(V), VO, forms two mononuclear species with the ligand. The stability constants of the complexes formed are given in the above mixed solvent media and interpreted. Linear relationships are observed when plotted log β versus 1/D, where β and D represent formation and dielectric constants, respectively. The results are discussed in terms of the effect on mole fraction of the solvent both for protonation and complexation of cysteine. An attempt has been made to ascertain the nature of the correction factor in determining the pH in the mixed solvent solutions and the effect of increasing organic solvent on log β is also considered.

Synthesis and characterization of two new coordination supramolecular structures from a versatile unsymmetric 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) ligand

Two new inorganic–organic coordination networks based on a versatile and unsymmetric building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and inorganic Co II and Cd II salts have been synthesized in mixed solvent media and structurally characterized by single-crystal X-ray diffraction analysis. Crystal Hpot ( 1) was obtained from methanol solution. Reaction of Co(NO 3) 2 · 6H 2O with Hpot afforded a neutral two-dimensional (2-D) porous coordination polymer {[Co(pot) 2] · 6H 2O} n ( 2) with a (4,4) network, which shows a 3-D supramolecular network through O–H⋯O weak interactions. While substituting the transition metal ions used in 2 with Cd(NO 3) 2 · 6H 2O, a neutral 2-D coordination polymer [Cd 2(pot) 4] n ( 3) with a (6,3) network which further extended to a 3-D supramolecular structure through versatile hydrogen bonds C–H⋯X (X = O, N and S) was obtained. It is remarkable that the building block “pot” anion exhibits versatile coordination modes in complexes 2 and 3. These results indicate that the versatile nature of this rigid unsymmetric ligand, together with the coordination preferences of the metal centers, plays a critical role in construction of novel coordination polymers. The properties of gas absorption, magnetism and luminescence of 2 and 3 have been investigated and discussed in detail.

Electrical Conductances of Tetrabutylammonium Bromide, Sodium Tetraphenylborate, and Sodium Bromide in Methanol (1) + Water (2) Mixtures at (298.15, 308.15, and 318.15) K

The electrical conductances of the solutions of tetrabutylammonium bromide (Bu4NBr), sodium tetraphenylborate (NaBPh4), and sodium bromide (NaBr) in methanol (1) + water (2) mixed solvent media containing 0.10, 0.20, and 0.30 volume fractions of methanol have been reported at (298.15, 308.15, and 318.15) K. The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA), and the association diameter (R). The ionic contributions to the limiting molar conductance have been estimated using tetrabutylammonium tetraphenylborate (Bu4NBPh4) as the “reference electrolyte”. All of these three electrolytes are found to exist as free ions in the present solvent mixtures within the temperature range (298.15 to 318.15) K. Besides the relative permittivity and the viscosity of the media, specific interactions of the ions with the solvent media have been found to play a profound influence on their mobilities. Although the association constants of the electrolytes do not vary significantly as a function of temperature, the limiting molar conductances of the electrolytes as well as the single-ion conductivity values increase appreciably with temperature.

Conductometric and Surface Tension Studies on the Micellization of Some Cationic Surfactants in Water-Organic Solvent Mixed Media

Micellar behaviour of Cetyl Trimethyl Ammonium Bromide (CTAB) and Tetradecyl Trimethyl Ammonium Bromide (TTAB) in water-organic solvent mixed media has been studied by means of conductivity and surface tension measurement at 303.15 K. The organic solvents chosen for the study are (a) Ethylene Glycol (EG) and its homologues, Mono Methyl (MME) and Mono Ethyl (MEE) Ethylene glycols, (b) cyclic ethers, Tetrahydrofuran (THF) and 1,4-Dioxane, and (c) Ethanolamine (EA), Diethanolamine (DEA) and Triethanolamine (TEA). It was observed that the presence of EG and MME, and the cyclic ethers generally led to an increase in critical micelle concentration (cmc) of the surfactants except for MEE. However, the presence of ethanolamines forced the surfactant monomers to micellize at lower surfactant concentrations decreasing the cmc of the surfactant. From the conductance and surface tension data, the degree of counter ion binding, b and the surface excess concentration, G max for all the systems have been evaluated. The results have been discussed in terms of breaking or making of the water structure and solvation of the hydrophobic tail of the surfactants by the hydrophobic (hydrocarbon) part of the organic solvents.

Electrical Conductances of Tetraethylammonium Bromide and Tetrapropylammonium Bromide in 2-Ethoxyethanol (1) + Water (2) Mixtures at (308.15, 313.15, 318.15, and 323.15) K

The electrical conductances of the solutions of tetraethylammonium bromide (Et4NBr) and tetrapropylammonium bromide (Pr4NBr) in 2-ethoxyethanol (1) + water (2) mixed solvent media containing 0.25, 50, and 0.75 mass fractions of 2-ethoxyethanol (w1) have been reported at (308.15, 313.15, 318.15, and 323.15) K. The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA), and the association diameter (R). These two electrolytes are found to exist essentially as free ions in the solvent mixtures with w1 = 0.25 and 50 over the entire temperature range; however, slight ionic association was observed in the mixed solvent medium richest in 2-ethoxyethanol. The electrostatic ion−solvent interaction is found to be very weak for the tetraalkylammonium ions in the aqueous 2-ethoxyethanol mixtures investigated.

Solvent sorption measurements in polymeric membranes with ATR-IR spectroscopy

Long-term stability and performance of polymeric membranes in solvent and mixed solvent media can be reduced due to sorption and swelling of the membrane matrix. For this reason quantification of sorption and swelling is of major importance for the development of future applications of membrane processes in solvent and mixed solvent media. In this work a method is discussed, based on attenuated total reflectance infrared spectroscopy (ATR-IR), to establish sorption and sorption selectivity of a cellulose acetate (CA) membrane in water/methanol and water/ethanol mixtures. By analysis of specific peaks from the ATR-IR spectra of the solvents, the preferential sorption of water in CA membranes can be quantified. In the presence of methanol, the selectivity for water ranges from 2.5 to 3.5 between 52 and 90% of methanol. For ethanol, the selectivity for water ranges from about 1 (30% ethanol) to 2 (90% ethanol). From the work it follows that ATR-IR provides an easy and non-destructive method to study the sorption behavior of the polymeric membrane separation layer.

Bioelectrocatalysis of Plant Peroxidases Immobilized on Graphite in Aqueous and Mixed Solvent Media

AbstractThe bioelectrocatalytic function of two plant peroxidases, horseradish peroxidase (HRP) and a newly purified royal palm tree‐leaf peroxidase (RPTP), was studied on graphite electrodes in aqueous buffer solutions, over the pH range 7.0–3.0, and in aqueous buffer solutions, at pH 6.0, containing different amounts of a polar organic cosolvent, i.e., ethanol and acetonitrile. The kinetics of direct and of mediated (using catechol as mediator) reduction of H2O2 at the HRP‐ and RPTP‐modified graphite electrodes were analyzed amperometrically at −50 mV(vs. Ag|AgCl|0.1 M KCl) in a flow‐through wall‐jet electrochemical system. Values of the apparent rate constant of the heterogeneous electron transfer between the enzyme and graphite, ks, the rate constant for enzymatic reduction of H2O2, k1, and the rate constant of mediated reduction of H2O2, k3, were determined using the modified Koutecky‐Levich approach. Analysis of the variation of the rate constants and the response of the peroxidase‐modified electrodes to H2O2 with pH and content of the organic cosolvent demonstrated that maximal peroxidase bioelectrocatalytic activity occurred at pH 5.0–6.0 and at concentrations of ethanol of 10–20% v/v. At a lower pH, higher concentrations of ethanol, and in aqueous solutions of acetonitrile, the bioelectrocatalytic activity of the peroxidase‐modified electrodes drastically decreased. However, contrary to the data for homogeneous catalysis, both peroxidases were bioelectrocatalytically active even in 95% organic co‐solvents, thus demonstrating a stabilizing effect of the enzyme immobilization on the bioelectrocatalytic performance of the peroxidases. RPTP immobilized on graphite demonstrated lower overall activity but a higher pH‐ and organic cosolvent‐stability than HRP.

Effects of Concentration, Relative Permittivity, and Temperature on the Solution Behavior of Sodium Carboxymethylcellulose As Probed by Electrical Conductivity

Precise measurements on the electrical conductivity of solutions of sodium salt of carboxymethylcellulose in acetonitrile/water mixed-solvent media containing 10, 20, and 40 vol % of acetonitrile are reported as a function of temperature. The degree of substitution of carboxymethylcellulose used was 0.70, and the concentrations were varied from approximately 1 x 10(-4) to approximately 1 x 10(-2) equiv L(-1). The results showed a decrease in the equivalent conductivity with increasing polyelectrolyte concentration. The applicability of Manning's theory for salt-free polyelectrolyte solutions was examined, and a major discrepancy against the theory was observed. The calculated values of the equivalent conductivity deduced on the basis of this theory were found to be higher than the experimental ones. Possible reasons for this discrepancy have been discussed. The fractions of uncondensed counterions were evaluated, and these were found to depend on the polyelectrolyte concentration. The effects of the temperature and relative permittivity of the medium on the equivalent conductivity as well as on the fraction of uncondensed counterions were also investigated.