New polymer electrolyte membranes for low temperature fuel cells

Partially fluorinated proton exchange materials were synthesised by pre-irradiation grafting of styrene into poly(vinylidene fluoride) films with subsequent sulfonation. The grafted and sulfonated membranes, PVDF-g-PSSA membranes, have been studied with respect to water uptake, ion and water clustering, ion conductivity and water diffusion coefficients. Water associates with the membranes in three different ways: bound non-freezable water, freezable bound water and freezable free water. The proton conductivity of the membrane is strongly dependent on the hydration, it decreases more rapidly than the water self diffusion with decreasing water content. Ion clusters with a Bragg distance of 25 Å form the conducting channels in the membranes.     

Antioxidant activity and inhibition of key enzymes linked to type-2 diabetes and hypertension by Azadirachta indica-yogurt

Azadirachta indica is widely used in traditional medicine to treat diabetes and hypertension. In the present study A. indica-yogurt was prepared and refrigerated up to 28 days. pH of A. indica-yogurt was lower whereas total titratable acid (TTA) was higher than plain-yogurt during storage. The total phenolic content (TPC) and antioxidant capacity increased during storage. A. indica-yogurt had highest TPC (74.9 ± 5.1 μgGAE/ml; p < 0.05) on day 28 and DPPH inhibition (53.1 ± 5.0%; p < 0.05) on day 14 compared to plain-yogurt (29.6 ± 1.1 μgGAE/ml and 35.9 ± 5.2%, respectively). The OPA values increased between day 7 and 21 of storage but reduced on the 4th week of storage with values for A. indica-yogurt being higher (p < 0.05) than plain-yogurts. Maximum inhibition of α-amylase (47.4 ± 5.8%), α-glucosidase (15.2 ± 2.5%) and angiotensin-1 converting enzyme (ACE, 48.4 ± 7.2%) by plain-yogurt water extract occurred on day 7, 14 and 0, respectively. A. indica-yogurt water extract increased the inhibition to maximal values for α-glucosidase and ACE on day 14 of storage (15.9 ± 10.1% and 79.70 ± 11.2%, respectively) and for α-amylase on day 21 of storage (54.8 ± 3.2%). A. indica-yogurt has higher TPC, antioxidant activities and enzymes inhibitory effects than plain-yogurt. Thus A. indica-yogurt may have the potential to serve as enhanced functional yogurt with anti-diabetic and anti-hypertension activities.     

Investigation on the interaction between C16TAB and NaCMC in semidilute aqueous solution based on rheological measurement

The rheological behavior of unentangled and entangled semidilute solution of anionic polyelectrolyte sodium carboxymethyl cellulose (NaCMC) containing cationic surfactant cetyltrimethylammonium bromide (C₁₆TAB) was investigated. The results reveal that the rheological properties of these semidilute NaCMC solutions depend on the amount of C₁₆TAB added. In the unentangled semidilute NaCMC solution (0.5 g/L), the viscosity decreases with the increase of C₁₆TAB amount in the low surfactant concentration region (below the critical aggregation concentration, CAC). However, in high surfactant concentrations (above CAC), the viscosity decreases sharply with the increase in C₁₆TAB amount. It is found that viscosity change of NaCMC solution could be described using Colby’s model when surfactant concentrations are between CAC and saturated concentration (C_s), suggesting that no inter-polymer interaction exists between C₁₆TAB and NaCMC in the unentangled semidilute solution. However, for the entangled semidilute NaCMC solution (5 g/L), the addition of C₁₆TAB leads to an increase in viscosity. Meanwhile, the solution exhibits an enhanced shear thinning behavior due to adding more C₁₆TAB than 1 mM. The viscosity increase is ascribed to the physical cross linking of surfactant micelles with NaCMC chains. Furthermore, it is suggested that the enhanced shear thinning behavior results from weak interaction between NaCMC chains and C₁₆TAB micelles.     

Enthalpies of solution of dl-α-alanyl-dl-α-asparagine in aqueous alcohols at 298.15 K

The enthalpies of solution of dl-α-alanyl-dl-α-asparagine (AlaAsn) were measured in aqueous methanol, ethanol, 1-propanol and 2-propanol with an alcohol mole-fraction content x₂ (from 0 to 0.4) at 298.15 K. The experimental results were used to calculate the enthalpies of transfer of AlaAsn from water to these mixtures as well as the enthalpy coefficients of pair-wise interactions (h_xy) between AlaAsn and alcohol molecules in water, according to the McMillan–Mayer's model. The h_xy values were found to be positive and increasing in a series methanol < ethanol < 1-propanol < 2-propanol.     

Phase equilibrium properties of binary aqueous solutions containing ethanediamine, 1,2-diaminopropane, 1,3-diaminopropane,or 1,4-diaminobutane at several temperatures

The vapour pressures of {ethanediamine (EDA) + water}, {1,2-diaminopropane (1,2-DAP) + water}, {1,3-diaminopropane (1,3-DAP) + water} or {1,4-diaminobutane (1,4-DAB) + water} binary mixtures, and of pure EDA, 1,2-DAP, 1,3-DAP, 1,4-DAB, and water components were measured by means of two static devices at temperatures between (293 and 363) K. The data were correlated with the Antoine equation. From these data, the excess Gibbs function (G^E) was calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker’s method. The {ethanediamine (EDA) + water}, and {1,2-diaminopropane (1,2-DAP) + water} binary systems show negative azeotropic behaviour. The aqueous solutions of EDA, 1,2-DAP, or 1,3-DAP exhibit negative deviations in G^E for all investigated temperatures over the whole composition range whereas the (1,4-DAB + water) binary mixture shows negative G^E for temperatures (293.15 < T/K < 353.15) and a sinusoidal shape for G^E at T = 363.15 K.     

All-vanadium redox photoelectrochemical cell: An approach to store solar energy

A highly-efficient all-vanadium photoelectrochemical storage cell has been demonstrated in this work. This storage cell takes advantage of fast electrochemical kinetics of vanadium redox couples of VO₂⁺/VO^2 + and V^3 +/V^2 +, and appears as a promising alternative to photoproduction of hydrogen from water. Continuous photocharging for 25 h revealed a VO^2 + conversion rate of 0.0042 μmol/h and Faradaic efficiency of 95% without external voltage bias. The incident photon-to-current efficiency (IPCE) at 350 nm light was calculated to be ~ 12%.     

A BET model of the thermodynamics of aqueous multicomponent solutions at extreme concentration

The statistical mechanical basis of the use of Brunauer-Emmett-Teller isotherms to represent activities and other thermodynamic properties in extremely concentrated solutions was established by Ally and Braunstein (J. Chem. Thermodynamics1998, 30, 49–58) for a two-salt, single-solvent, mixture. Based upon the work of these authors, we have derived equations for solute and solvent activities in liquid mixtures containing a single solvent and indefinite number of solutes. New terms have been added to the model equations to express the effects of ternary ion interactions on the salt adsorption parameters. Solution composition is defined on the basis of salts, rather than ions, as components. As examples, the model is used to represent water activities in concentrated (lithium nitrate  +  potassium nitrate  +  water) and (lithium ion  +  sodium ion  +  chloride ion  +  nitrate ion  +  water) mixtures, and salt solubilities in (calcium chloride  +  calcium nitrate  +  water) mixtures.     

Radiation decontamination of poultry viscera

Application of gamma radiation for decontamination of poultry viscera was examined. Exposure to a dose of 20 kGy rendered the viscera sterile (<1 CFU/10 g tissue), while 5 and 10 kGy reduced the total bacterial count by 4 and 6 log₁₀ cycles, respectively, eliminating the coliforms to <1 CFU/g of tissue. Analysis of organoleptic and biochemical parameters [proximate composition, total volatile basic nitrogen (TVBN), lipid peroxidation (TBARS value), and levels of TCA soluble peptides and proteolytic enzyme] showed that gamma irradiation (20 kGy) followed by storage at 4 °C for 62 days induced no significant change (except lipid peroxidation) in the acceptability of poultry viscera. However, storage at ambient temperature (26 °C) produced enhanced levels of TVBN and TCA soluble products accompanied by higher drip loss. Activities of proteolytic enzymes, except acid protease, did not show any significant change during post-irradiation storage at either temperature.     

Investigation of sodium 4-nitrotoluene-2-sulfonate solubility in aqueous organic solutions

The solubility of sodium 4-nitrotoluene-2-sulfonate (NTSNa) in binary solvent mixtures (methanol + water), (ethanol + water), and (2-methoxyethanol + water) was investigated over the temperature range from (288 to 344) K. The mole fraction of water in solvent mixtures ranged from 0 to 0.8. The solubility data are described by the electrolyte non-random two-liquid (E-NRTL) model. The E-NRTL binary interaction parameters are expressed as a function of temperature, and were obtained from the experimental data. The root-mean-square deviations of solubility temperature varied from (0.20 to 1.35) K.     

Experimental measurement and modelling of solubility of inosine-5′-monophosphate disodium in pure and mixed solvents

The solubility of biological chemicals in solvents provide important fundamental data and is generally considered as an essential factor in the design of crystallization processes. The equilibrium solubility data of inosine-5′-monophosphate disodium (5′-IMPNa₂) in water, methanol, ethanol, acetone, as well as in the solvent mixtures (methanol + water, ethanol + water, acetone + water), were measured by an isothermal method at temperatures ranging from (293.15 to 313.15) K. The measured data in pure and mixed solvents were then modelled using the modified Apelblat equation, van’t Hoff equation, λh equation, ideal model and the Wilson model. The modified Apelblat equation showed the best modelling results, and it was therefore used to predict the mixing Gibbs free energies, enthalpies, and entropies of 5′-IMPNa₂in pure and binary solvents. The positive values of the calculated partial molar Gibbs free energies indicated the variations in the solubility trends of 5′-IMPNa₂. Water and ethanol (in the binary mixture with water) were found to be the most effective solvent and anti-solvent, respectively.     

Interfacial tensions of binary mixtures of ethanol with octane,decane, dodecane,and tetradecane

This contribution is devoted to the experimental characterization of interfacial tensions of a representative group of binary mixtures pertaining to the (ethanol + linear hydrocarbon) series (i.e. octane, decane, dodecane, and tetradecane). Experimental measurements were isothermically performed using a maximum differential bubble pressure technique, which was applied over the whole mole fraction range and over the temperature range 298.15 K < T/K < 318.15 K.Experimental results show that the interfacial tensions of (ethanol + octane or decane) negatively deviate from the linear behavior and that sharp minimum points on concentration, or aneotropes, are observed for each isotherm. The interfacial tensions of (ethanol + dodecane or tetradecane), in turn, are characterized by combined deviations from the linear behavior, and inflecting behavior observed on concentration for each isotherm. The experimental evidence also shows that these latter mixtures are close to exhibit aneotropy.For the case of (ethanol + octane or decane) mixtures, aneotropy was clearly induced by the similarity of the interfacial tension values of the constituents. The inflecting behavior of the interfacial tensions of (ethanol + dodecane or tetradecane), in turn, was observed in the vicinity of the coordinates of the critical point of these mixtures, thus pointing to the fact that the quasi-aneotropic singularity that affects these mixtures was provoked by the proximity of an immiscibility gap of the liquid phase.Finally, the experimental data of interfacial tensions were smoothed with the Scott–Myers expansion, from which it is possible to conclude that the observed aneotropic concentrations weakly depend on temperature for all the analyzed mixtures.     

Investigation of the isothermal (vapour + liquid) equilibria of aqueous 2-amino-2-methyl-1-propanol (AMP), N-benzylethanolamine,or 3-dimethylamino-1-propanol solutions at several temperatures

The vapour pressures of (2-amino-2-methyl-1-propanol (AMP) + water), (N-benzylethanolamine + water), or (3-dimethylamino-1-propanol + water) binary mixtures, and of pure AMP and 3-dimethylamino-1-propanol components were measured by means of two static devices at temperatures between 283 K and 363 K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (G^E) were calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker’s method. The {2-amino-2-methyl-1-propanol (AMP) + water} binary mixture exhibits negative deviations in G^E (at T < 353.15 K) and a sinusoidal shape for G^E for the higher temperatures over the whole composition range. For the aqueous N-benzylethanolamine solution, a S shape is observed for the G^E for all investigated temperatures over the whole composition range. The (3-dimethylamino-1-propanol + water) binary mixture exhibits negative deviations in G^E (at T < 293.15 K), positive deviations in G^E (for 293.15 K < T < 353.15 K) and a sinusoidal shape for G^E for the higher temperatures over the whole composition range.     

Phase equilibrium properties of binary aqueous solutions of benzylamine, 1,2-bis(2-aminoethoxy)ethane,or 2-[2-(dimethylamino)ethoxy]ethanol

The vapour pressures of (benzylamine + water), {1,2-bis(2-aminoethoxy)ethane + water}, or {2-[2-(dimethylamino)ethoxy]ethanol + water} binary mixtures, and pure 2-[2-(dimethylamino)ethoxy]ethanol component were measured by means of two static devices at temperatures between (283.15 and 363.15 (or 323.15)) K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (G^E) were calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker’s method. The (benzylamine + water) binary mixture exhibits positive deviations in G^E for (303.15 < T/K < 323.15) and a sinusoidal shape in G^E for T > 323.15 K over the whole composition range. The aqueous 1,2-bis(2-aminoethoxy)ethane or {2-[2-(dimethylamino)ethoxy]ethanol + water} solutions exhibit negative deviations in G^E for all investigated temperatures over the whole composition range.     

Excess Gibbs energies and excess molar volumes for binary mixtures: (2-pyrrolidone + water), (2-pyrrolidone + methanol), and (2-pyrrolidone + ethanol) at the temperature 313.15 K

Total vapour pressures and excess molar volumes, measured at the temperature 313.15 K, are reported for three binary mixtures (2-pyrrolidone + water), (2-pyrrolidone + methanol) and (2-pyrrolidone + ethanol). The results are compared with previously obtained data for binary mixtures (amide + A), where amide=N-methylformamide, N,N-dimethylformamide and N-methylacetamide, and A= water, methanol, and ethanol.     

Exploring the interfacial neutral pH region of Pt(111) electrodes

The interfacial properties of Pt(111) single crystal electrodes have been investigated in the pH range 3 < pH < 5 in order to obtain information about the acidity of electrosorbed water. Proper experimental conditions are defined to avoid local pH changes while maintaining the absence of specifically adsorbed anions and preserving the cleanliness of the solution. For this purpose, buffer solutions resulting from mixtures of NaF and HClO₄ are used. Total charge curves are obtained at different pHs from the integration of the voltammetric currents in combination with CO charge displacement experiments. Analysis of the composition of the interphase as a function of the pH provides information for the understanding of the notion of interfacial pH.     

Comparative antioxidant activity,proteolysis and in vitro α-amylase and α-glucosidase inhibition of Allium sativum-yogurts made from cow and camel milk

The presence of extract of plant with medicinal properties during milk fermentation could enhance the therapeutical values of yogurt. In the present study, the effects of Allium sativum on the changes in post-acidification, total phenolic content (TPC), proteolysis by o-phthaldialdehyde (OPA) assay, antioxidant activity by (1,1-diphenyl-2-picrylhydrazyl radical (DPPH) inhibition) and capacity to inhibit in vitro α-amylase and α-glucosidase activities in cow or camel milk yogurt (MY) during 21 day refrigerated storage were investigated. The presence of A. sativum enhanced more pH reduction for camel-MY than for cow-MY compared to their respective controls during storage. The reverse was true for total titratable acid. TPC in camel-MY was higher (p < 0.05) than that in cow-MY. The presence of A. sativum in cow- and camel-MYs elevated (p < 0.05) the TPC, but these changed little during storage. Antioxidant activities (18–38% DPPH inhibition) were not different in both types of yogurts, either in the absence or in the presence of A. sativum. However, camel-MY had an increase (p < 0.05) in antioxidant activities (49–65%) during 7–21 days of storage. OPA values on day 0 was higher for camel-MY (368.2 ± 14.8 mg/g) than for cow-MY (80.1 ± 3.2 mg/g). The presence of A. sativum increased OPA values more for cow-MY than for camel-MY (3.0- and 1.3-folds, respectively). Higher inhibition (p < 0.05) of α-amylase by camel-MY compared to cow-MY occurred whereas α-glucosidase inhibition by cow-MY reduced (p < 0.05) as a result of refrigeration greater than 7 days. In general, the addition of A. sativum caused more antioxidant activities, proteolysis and enzymes (α-amylase and α-glucosidase) inhibition in camel-MY than in cow-MY.     

Thermodynamic study of (anthracene + phenanthrene) solid state mixtures

Polycyclic aromatic hydrocarbons (PAH) are common components of many materials, such as petroleum and various types of tars. They are generally present in mixtures, occurring both naturally and as byproducts of fuel processing operations. It is important to understand the thermodynamic properties of such mixtures in order to understand better and predict their behavior (i.e., fate and transport) in the environment and in industrial operations. To characterize better the thermodynamic behavior of PAH mixtures, the phase behavior of a binary (anthracene + phenanthrene) system was studied by differential scanning calorimetry, X-ray diffraction, and the Knudsen effusion technique. Mixtures of (anthracene + phenanthrene) exhibit non-ideal mixture behavior. They form a lower-melting, phenanthrene-rich phase with an initial melting temperature of 372 K (identical to the melting temperature of pure phenanthrene) and a vapor pressure of roughly lnP/Pa = −2.38. The phenanthrene-rich phase coexists with an anthracene-rich phase when the mole fraction of phenanthrene (x_P) in the mixture is less than or equal to 0.80. Mixtures initially at x_P = 0.90 consist entirely of the phenanthrene-rich phase and sublime at nearly constant vapor pressure and composition, consistent with azeotrope-like behavior. Quasi-azeotropy was also observed for very high-content anthracene mixtures (2.5 < x_P < 5) indicating that anthracene may accommodate very low levels of phenanthrene in its crystal structure.     

Stability and performance of porous silica–zirconia composite membranes for pervaporation of aqueous organic solutions

Porous silica–zirconia membranes were fabricated by the sol–gel techniques to study their stability against water and the pervaporation performance of aqueous solutions of organic solvents. Zirconia (10–70 mol%) was added to silica to obtain silica–zirconia composite membranes by firing at 400–500 °C for pervaporation tests with organic solvent/water mixtures, such as iso-propyl alcohol (IPA)/water and tetrahydrofuran (THF)/water mixtures at their normal boiling points.The membrane coatings have been done effectively by the hot-coating methods proposed previously. Boiling water treatments introduced in the coating processes have made the membranes quite stable even in the high water concentration region of aqueous organic solutions at their normal boiling points. Zirconia contents larger than about 40 mol% have made the silica–zirconia membranes quite stable. The membranes of zirconia contents less than about 30 mol% were found not stable in a dilute aqueous solution of IPA. The membranes fabricated by the conventional dip-coating methods with slow drying were not stable against water because of the probable segregation of silica and/or silica-rich phases during drying.The membranes fired at lower temperature (400 °C) gave a higher water flux of around 500 mol m⁻² h⁻¹ (9 kg m⁻² h⁻¹) with a separation factor larger than 1500 at 10 wt.% of water in the boiling feed of IPA/water mixture, for example.     

Thermodynamic properties of binary mixtures containing hydrofluoroether

Excess molar enthalpy and excess molar volume at T =  298.15 K are reported for binary mixtures of (nonafluorobutylmethylether  +  butylmethylether, or nonane, or heptane, or pentane, or 1-propanol, or 2-propoxyethanol). Excess molar enthalpies of the mixture of (nonafluorobutylmethylether  +  1-pentanol) also are reported at T =  298.15 K. The results of excess molar enthalpy are endothermic and the results of excess molar volume are positive in the whole concentration for all the mixtures. The phase separation is found in the range of 0.15  < x <  0.92 for the 1-pentanol system. The results are explained by means of the destruction of the dipolar interactions and hydrogen bonds in the component liquids, the difference of the dispersion interaction, and the formation of the intermolecular hydrogen bonds between unlike molecules.     

Calorimetric investigations of hydrogen bonding in binary mixtures containing pyridine and its methyl-substituted derivatives. II. The dilute solutions of methanol and 2-methyl-2-propanol

Enthalpies of solution of methanol and 2-methyl-2-propanol (tert-butanol) in pyridine and its methyl derivatives were investigated in the range of mole fractions of alcohol x⩽0.02 at temperature 298.15 K by a titration calorimeter. Dissolution of methanol is an exothermic process, with heat effects very close to those for water reported in part I of this study. The negative enthalpy of solution increases in the following order: pyridine < 3-methylpyridine < 4-methylpyridine < 2-methylpyridine < 2,6-dimethylpyridine < 2,4,6-trimethylpyridine. Positive enthalpies of solution of 2-methyl-2-propanol increase as follows: 2-methylpyridine < 2,4,6-trimethylpyridine < 4-methylpyridine < 2,6-dimethylpyridine < 3-methylpyridine < pyridine. The propensity of pyridine derivatives to hydrogen bonding is enhanced by the ortho effect. Methyl groups are probably too small to prevent the nitrogen atom in the pyridine ring from hydrogen bonding. However, spacious hydrocarbon group in 2-methyl-2-propanol molecule makes the bonding difficult for 2,6-dimethylpyridine and 2,4,6-trimethylpyridine, thus the number of O–H⋯N bonds is smaller than that in the solutions of methanol or water. The two latter seem to be very close to each other.