Solvation phenomena and revision of solid–liquid equilibria in aqueous solutions of two precursors of mixed oxides, the hydrates of cobalt and nickel nitrates

The hydrates of cobalt and nickel nitrates are highly relevant as precursors for the preparation of mixed ceramics. In order to verify the numerous bibliographical data, systematic solubility measurements in aqueous medium under atmospheric pressure and a critical evaluation have been undertaken. By taking solvation phenomena into account, it has proved possible to correlate all the phenomena observed, to obtain equations representative of the liquidus curves, and to refine and extrapolate the experimental curves. The whole stable and metastable coordinates of the invariant transformations in both binary systems have been calculated or more accurately determined.     

Modelling of high-pressure phase equilibria using the Sako–Wu–Prausnitz equation of state: II. Vapour–liquid equilibria and liquid–liquid equilibria in polyolefin systems

Phase equilibria in binary and ternary polyolefin systems are calculated using the cubic equation of state proposed by Sako–Wu–Prausnitz (SWP). Calculations were done for high-pressure phase equilibria in ethylene/polyethylene (LDPE) systems and for liquid–liquid equilibria (LLE) in systems containing either high-density polyethylene or poly(ethylene-co-propylene). The calculations for the copolymer/solvent systems are compared with those using the SAFT EOS. The two equations of state can describe UCST, LCST as well as U-LCST behaviour with similar accuracy. Whereas, the binary interaction parameter is temperature-independent for SAFT, it is found to be a function of temperature for the SWP model. Moreover, the influence of an inert gas on the LCST of the polyethylene/hexane system is investigated using the SWP EOS. The polydispersity of the different polyethylenes is considered in the phase equilibrium calculations using pseudocomponents chosen by the moments of the experimental molecular weight distributions.     

Measurement and correlation of solid–liquid equilibria of Irganox 1010 with n-hexane

Solid–liquid equilibria (SLE) for the binary mixtures of Irganox 1010 with n-hexane have been measured using a method in which an excess amount of solute was equilibrated with the alkane solution. The liquid concentrations of the Irganox 1010 in the saturated solution were analyzed by UV spectrometry. Activity coefficients for Irganox 1010 have been calculated by means of the Wilson, NRTL and UNIQUAC models and with them were correlated solubility data that were compared with the experimental ones. The best correlation of the solubility data has been obtained by the Wilson model, by which the average root-mean-square deviation of temperature for the system is 0.33 K.     

Modeling of three-phase vapor–liquid–liquid equilibria for a natural-gas system rich in nitrogen with the SRK and PC-SAFT EoS

In this work, we present the modeling of three-phase vapor–liquid–liquid equilibria for a mixture of natural gas (Hogback gas) containing high concentrations in nitrogen (51.8 mol%) with the SRK and PC-SAFT equations of state. The interest of studying this mixture is due to the experimental evidence of the occurrence of multiple equilibrium liquid phases for this mixture over certain ranges of temperature and pressure. The calculation of the multiphase equilibria was carried out by using an efficient numerical procedure based on the minimization of the system Gibbs energy and thermodynamic stability tests to find the most stable state of the system. The results of the calculated vapor–liquid–liquid equilibria (VLLE) show that the PC-SAFT equation of state predicts satisfactorily the phase behavior that experimentally exhibits this mixture, whereas the SRK equation of state predicts a three-phase region wider than the experimentally observed. The two-phase boundary for this mixture was also calculated through flash calculations, and the results showed that this mixture does not present any gas-liquid critical point.     

Phase equilibria involving solid solutions in the Li–Mn–O system

Phase equilibria involving LiMn₂O_4-, Li₂MnO_3-, LiMnO_2-, Mn₃O_4-, and MnO-base solid solutions were studied with varied temperature and partial oxygen pressure. The \({P_{{o_2}}}\)–T and x–y projections of the P–T–x–y phase diagram of the Li–Mn?O system were constructed, as well as the key x–y isotherms of the Li₂O–MnO–MnO₂ quasi-ternary system. In some experiments, the authors’ hydride lithiation method was employed to prepare lithium-rich homogeneous three-component nonstoichiometric phases.     

Molecular simulation of protein adsorption and conformation at gas-liquid,liquid–liquid and solid–liquid interfaces

The adsorption of proteins at surfaces and interfaces is important in a wide range of industries. Understanding and controlling the conformation of adsorbed proteins at surfaces is critical to stability and function in many technological applications including foods and biomedical testing kits or sensors. Studying adsorbed protein conformation is difficult experimentally and so over the past few decades researchers have turned to computer simulation methods to give information at the atomic level on this important area. In this review we summarize some of the significant simulation work over the past four years at both fluid (liquid–liquid and gas–liquid interfaces) and solid–liquid interfaces. Of particular significance is the work on surfactant proteins such as fungal hydrophobins, ranspumin-2 from the túngara frog and the bacteria protein BslA. These have evolved unique structures impart very high surface-active properties to the molecules. A highlight is the elucidation of the clam-shell unhinging mechanism of ranspumin-2 adsorption to the gas–liquid interface that is responsible for its adsorption to and stabilization of the air bubbles in túngara frog foam nests.     

Phase equilibria in a polyethylene–polystyrene system

The method of optical interferometry is used to study the interaction of PE with PS in situ. On the basis of the obtained data, phase diagrams of the PE–PS system are constructed for a number of molecular masses of the components. For PE and PS oligomers, the UCMT values are determined. Pair parameters for the interaction of homopolymers are calculated, and their dependences on temperature and molecular mass are considered. The quantitative analysis of the behavior of high-molecular-mass fractions of PE and PS at high temperatures is carried out, and the regions of a partial compatibility of the components are predicted.     

Liquid–liquid equilibria in ternary systems of linear and cross-linked water-soluble polymers

In this study, ternary liquid–liquid equilibrium data of structurally similar linear and cross-linked polymers have been measured in order to elucidate the significance of mixing and elastic effects in sorption of binary liquid mixtures by cross-linked polymers. Dextran, sodium poly(styrene sulfonate), and sodium poly(acrylate) were used as the linear analogues for Sephadex gels and for strong and weak cation exchange resins. Cloud-point and co-existence curves were measured in water/ethanol and water/2-propanol mixtures at 283–343 K and the results were correlated by using a generalized Flory–Huggins model. The mixing parameters of the linear polymers were used to simulate the sorption data in the cross-linked materials and the effect of cross-links was accounted for by a non-ideal elastic model. Good agreement between the simulated and experimental values is obtained, when the chemical heterogeneity and the incomplete functionalization of the cross-linked materials are taken into account. The influence of temperature on the sorption equilibria in cross-linked polymers is also discussed on the basis of the temperature dependence of the cloud-point data.     

Modeling of liquid–liquid equilibrium of polyethylene glycol-salt aqueous two-phase systems—the effect of partial dissociation of the salt

The modified NRTL model proposed in the previous paper [Y.-T., Wu, D.-Q. Lin, Z.-Q. Zhu, L.-H. Mei, Fluid Phase Equilibria 124 (1996) 67–79.] is further extended to include the effect of partial dissociation of salts in polyethylene glycol (PEG)–salt aqueous two-phase systems (ATPS), and is used to calculate the liquid–liquid equilibrium phase diagrams such as PEG–(NH₄)₂SO₄ and PEG–MgSO₄ ATPS. The phase diagrams of PEG–uni-bivalent salt ATPS can be correctly represented in the cases of both complete dissociation and partial dissociation of the salt, while those of PEG–MgSO₄ ATPS can only be described in the case of partial dissociation of the salt. The analysis shows that the salts may have different existing states in the ATPS. The effect of partial dissociation of the salts on the phase diagrams should be considered, especially for systems such as PEG–MgSO₄ ATPS.     

Dynamic properties of the polyethylene glycol molecules on the oscillating solid–liquid interface

The dynamic properties of polyethylene glycol (PEG) molecules on the solid–liquid interface oscillating at MHz were investigated using the quartz crystal microbalance (QCM). The number-average molecular weights (M_n) of the PEG molecules were systematically varied over 4 orders of magnitude. This study makes it clear that the series-resonant frequency shift, ΔF, of the QCM against the square root of the density–viscosity product of the PEG solution is linear and has the intercept. Moreover, systematical analysis reveals that the ΔF slope rapidly decreases with M_n and that the ΔF intercept becomes constant above 4.0 × 10³ g mol⁻¹. As a result, those reveal that the resonant length of the PEG molecule moving with the oscillating plate of 9 MHz is 54.2 Å. We also find that the behaviors of ΔF due to M_n are mainly caused by the length of the PEG molecule.     

Automated apparatus for the rapid determination of liquid–liquid and solid–liquid phase transitions

An automated apparatus developed for the determination of liquid–liquid and solid–liquid equilibrium temperatures with a resolution of 1 mK and a traceable accuracy of 0.01 K is described. The amount of light transmitted through six sample cells placed in a computer controlled thermostat is recorded at heating or cooling rates from 0.075 to 15 K h⁻¹. The construction does not require expensive optic equipment like lasers, glass fibre optics or photomultipliers, but is based on light emitting diodes (LED) as light sources and light dependent resistors (LDR) or photodiodes as detectors. As shown by the discussed examples, the instrument has a wide range of possible applications from the investigation of simple one-component and binary systems to the study of the complicated phase behavior of surfactant solutions.     

Soft-SAFT modeling of vapor–liquid equilibria of nitriles and their mixtures

Nitriles are strong polar compounds showing a highly non-ideal behavior, which makes them challenging systems from a modeling point of view; in spite of this, accurate predictions for the vapor–liquid equilibria of these systems are needed, as some of them, like acetonitrile (CH₃CN) and propionitrile (C₂H₅CN), play an important role as organic solvents in several industrial processes. This work deals with the calculation of the vapor–liquid equilibria (VLE) of nitriles and their mixtures by using the crossover soft-SAFT Equation of State (EoS). Both polar and associating interactions are taken into account in a single association term in the crossover soft-SAFT equation, while the crossover term allows for accurate calculations both far from and close to the critical point. Molecular parameters for acetonitrile, propionitrile and n-butyronitrile (C₃H₇CN) are regressed from experimental data. Their transferability is tested by the calculation of the VLE of heavier linear nitriles, namely, valeronitrile (C₄H₉CN) and hexanonitrile (C₅H₁₁CN), not included in the fitting procedure. Crossover soft-SAFT results are in excellent agreement with experimental data for the whole range of thermodynamic conditions investigated, proving the robustness of the approach. Parameters transferability has also been used to describe the isomers n-butyronitrile and i-butyronitrile. Finally, the nitriles soft-SAFT model is further tested in VLE calculation of mixtures with benzene, carbon tetrachloride and carbon dioxide, which proved to be satisfactory as well.     

Binary,ternary and quaternary liquid–liquid equilibria in 1-butanol,oleic acid,water and n-heptane mixtures

This work reports on liquid–liquid equilibria in the system 1-butanol, oleic acid, water and n-heptane used for biphasic, lipase catalysed esterifications. The literature was studied on the mutual solubility in binary systems of water and each of the organic components. Experimental results were obtained on the composition of the coexisting phases of a series of ternary and quaternary mixtures of the components at 301, 308 and 313 K. The data were correlated successfully with the UNIQUAC model that was extended with ternary interaction parameters.     

Vapour—liquid equilibria of dilute solutions of phenols in cyclohexane. Self-association of ortho-substituted phenols

Vapour—liquid equilibria of dilute solutions of ortho-substituted phenols in cyclohexane have been studied. The isopiestic apparatus and the operational procedure have been described. Eight mono- and di-substituted ortho-alkylphenols have been studied at 298.15 K using this technique; o-ethyl- and o-chlorophenol solutions have been studied at 298.15 and 323.15 K using the bubble-point method. The values of dimerization and polymerization constants are given. The practical osmotic coefficient of the solutions of diphenyl in cyclohexane at 298.15 K (serving as reference in isopiestic measurements) has been determined bythe bubble-point method, and the results represented by a polynomial.     

Characterization of adsorption processes in analytical liquid–solid chromatography

This review discusses nonlinear chromatographic methods of importance for proper characterization of the adsorption processes in analytical chromatographic systems, with focus on reversed-phase liquid chromatography. Linear methods such as the linear solvation energy relationship (LSER) method and the Snyder–Dolan hydrophobic-subtraction model will also be reviewed briefly. The nonlinear methods for adsorption isotherm determination and the tools for further treatment of the nonlinear adsorption data will be extensively treated in a way suitable for the general chromatographer. Applications of the various methods will be given and the outcome and conclusions will be discussed. Special emphasis will be placed on discussing the possibilities of combining linear and nonlinear methods in order to obtain a deeper and more complete investigation of the interactions in the actual phase system.     

Predicting vapor–liquid equilibria of fatty systems

In the present work, a group contribution method is proposed for the estimation of the vapor pressure of fatty compounds. For the major components involved in the vegetable oil industry, such as fatty acids, esters and alcohols, triacylglycerols (TAGs) and partial acylglycerols, the optimized parameters are reported. The method is shown to be accurate when it is used together with the UNIFAC model for estimating vapor–liquid equilibria (VLE) of binary and multicomponent fatty mixtures comprised in industrial processes such as stripping of hexane, deodorization and physical refining. The results achieved show that the group contribution approach is a valuable tool for the design of distillation and stripping units since it permits to take into account all the complexity of the mixtures involved. This is particularly important for the evaluation of the loss of distillative neutral oil that occurs during the processing of edible oils.The combination of the vapor pressure model suggested in the present work with the UNIFAC equation gives results similar to those already reported in the literature for fatty acid mixtures and oil–hexane mixtures. However, it is a better tool for predicting vapor–liquid equilibria of a large range of fatty systems, also involving unsaturated compounds, fatty esters and acylglycerols, not contemplated by other methodologies. The approach suggested in this work generates more realistic results concerning vapor–liquid equilibria of systems encountered in the edible oil industry.     

Simultaneous determination of sulfonamides and metabolites in manure samples by one-step ultrasound/microwave-assisted solid–liquid–solid dispersive extraction and liquid chromatography–mass spectrometry

An in-line matrix cleanup method was used for the simultaneous extraction of 15 sulfonamides and two metabolites from manure samples. The ultrasound/microwave-assisted extraction (UMAE) combined with solid–liquid–solid dispersive extraction (SLSDE) procedure provides a simple sample preparation approach for the processing of manure samples, in which the extraction and cleanup are integrated into one step. Ultrasonic irradiation power, extraction temperature, extraction time, and extraction solvent, which could influence the UMAE efficiency, were investigated. C₁₈ was used as the adsorbent to reduce the effects of interfering components during the extraction procedure. The extracts were concentrated, and the analytes were analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) without any further cleanup. The isotopically labeled compounds sulfamethoxazole-d ₄, sulfamethazine-d ₄, sulfamonomethoxine-d ₄, and sulfadimethoxine-d ₆ were selected as internal standards to minimize the matrix effect in this method. The recoveries of the antibiotics tested ranged from 71 to 118 % at the three spiking levels examined (20, 200, and 500 μg?·?kg^-1). The limits of detections were 1.2–3.6 μg?·?kg^-1 and the limits of quantification were 4.0–12.3 μg?·?kg^-1 for the sulfonamides and their metabolites. The applicability of the method was demonstrated by analyzing 30 commercial manure samples. The results indicated that UMAE–SLSDE combined with LC–MS/MS is a simple, rapid, and environmentally friendly method for the analysis of sulfonamides and their metabolites in manure, and it could provide the basis for a risk assessment of the antibiotics in agricultural environments.     

Subsolidus equilibria and kinetics of decomposition of solid solutions in the HfO2(ZrO2MgO systems

The subsolidus equilibrium diagram in the HfO₂MgO system has been constructed and contains a eutectoid point similar to the ZrO₂MgO system. A comparative study of the stabilities of solid solutions of MgO in HfO₂ and in ZrO₂ has been made. The difference in phase stability of the solid solutions in the temperature range 1300 to 1450°C is due to the difference of eutectoid temperatures in the two systems. The mechanism and kinetics of decomposition of the HfO₂MgO solid solutions have been studied. The decomposition process of solid solutions in this system and in the ZrO₂MgO system is a particular case of the wide-spread type of eutectoid decomposition which is governed by the laws of eutectoid equilibria. The decomposition of the cubic solid solutions in both systems proceeds in two steps.     

Studies on morphology of polyaniline films formed at liquid–liquid and solid–liquid interfaces at 25 and 5 °C,respectively, and effect of doping

It is well accepted that the morphology of the nanomaterials has great effect on the properties and hence their applications. Therefore, morphology of materials has become a focus of research in the scientific world. The present study shows that interfacial polymerization and subsequent self-assembly provides a control over the morphology, nanorod/nanosheet, of polyaniline (PANI) films synthesized by liquid–liquid interface reaction technique and solid–liquid interface reaction technique. The synthesized PANI films and its particulate structure are characterized by using various spectroscopic techniques such as UV–visible, ATR-IR, Raman and XPS. The study confirmed the formation, the structure, the size and shape of particles and morphology of PANI by using analytical techniques namely, SAED, SEM and TEM. An important observation is that doping with HCl significantly improves the nanorod formation at the interface. The doped PANI electrode exhibits a higher area with rectangular shape in CV cycle and better cycle stability when compared with the performance of undoped PANI films. We believe that the results of these studies can give valuable leads to manoeuvre formation of PANI films with desired morphology for various applications.