Effect of temperature on the phase-separation ability of KCl in aqueous two-phase systems composed of propanols: Determination of the critical temperature and extension of the results to other salts

The phase-forming ability of KCl in propanols has been investigated, aiming to assess its utility in aqueous two-phase extraction. Equilibrium data of the different equilibrium regions (SLLV, SLV, LLV, and LV) of aqueous two-phase systems (ATPSs) of water + KCl + 1-propanol and water + KCl + 2-propanol have been determined at the boiling temperatures of the mixtures and 101.3 kPa. In addition, the lowest critical solution temperature (LCST) for the water + KCl + 1-propanol system was measured to be 271.2 K, and the equilibrium behavior of the system in the vicinity of the LCST (at 268.1 and 273.1 K) was also determined. Finally, using various methods such as the effective excluded volume (EEV) theory, Setchenov-type equations, and the plait point of the liquid-liquid region, different salt and alcohol systems have been studied and classified according to their ability to produce ATPSs.We would like to thank the ‘‘Dirección General de Investigación Científica y Técnica” DGICYT, of Spain for the financial support under project CTQ2014-59496

Influence of the temperature on the equilibrium phase diagram of the ternary system water + ammonium chloride + 2-propanol at 101.3 kPa

The phase equilibrium of the water + NH4Cl + 2-propanol mixture, at a constant pressure of 101.3 kPa, has been determined isothermally at four temperatures, as well as at the boiling temperature. Transitions between the different regions of the isothermal equilibrium diagrams have been studied, and the lowest temperature at which the salt can split water + 2-propanol mixtures into two liquid phases, is found to be 310.1 K. As the temperature is increased from this critical value, the two-liquid-phase region expands until the boiling temperature is reached. Finally, the extended UNIQUAC model for electrolytes has been used to predict the equilibrium diagram of the system. Large discrepancies with the experimental results have been found, and it will, therefore, be necessary to review the parameters of the model based on the experimental data reported in this work.We would like to thank the DGICYT of Spain for the financial support of project CTQ2014-59496

CaSO4 solubility in water–ethanol mixtures in the presence of sodium chloride at 25 °C. Application to a reverse osmosis process

Nowadays, the most common way to desalinate seawater is by reverse osmosis. As the degree of conversion during this process increases more freshwater is recovered from the feedwater. As a result, the salt concentration in the feed increases up to a point where the solubility limit could be reached. Experimentally, it is known that adding an organic substance such as ethanol to salty water induces salt precipitation. This work investigated the solid–liquid equilibrium of the system water–ethanol–NaCl–CaSO4 at 25 °C. Results show that as the ethanol content is increased CaSO4 solubility decreases. On the other hand, brine from the reverse osmosis plant at the University of Alicante was treated with ethanol to precipitate calcium sulfate and produce brine containing less calcium and sulfate. The treated brine was analyzed and its calcium content was compared with the predicted value based on the experimental data. The results suggest that it is possible to use ethanol to precipitate the salts from brine in order to obtain a higher degree of conversion in a reverse osmosis process. The obvious limitation of the method is the cost of recovering the ethanol by separation

Equilibrium diagram of the water + K2SO4 or Na2SO4 + 1-propanol or 2-propanol systems at boiling conditions and 101.3 kPa

Thermodynamically consistent phase equilibrium data at 101.3 kPa and boiling conditions were determined for the ternary systems water + Na2SO4 + 1-propanol, water + Na2SO4 + 2-propanol, water + K2SO4 + 1-propanol and water + K2SO4 + 2-propanol. In contrast to the systems with Na2SO4, the salting-out effect of K2SO4 was not sufficient to split the miscible propanol + water mixture into two liquid phases. The UNIQUAC equation extended to electrolytes for the liquid phase activity coefficients was used to predict the phase equilibria of all the systems. The model reproduced the experimental results quite well, except for the ternary system water + K2SO4 + 1-propanol. In this case the model predicted liquid-liquid splitting into two liquid phases, when there is not.We would like to thank the DGICYT of Spain for the financial support of project CTQ2014-59496

Consistency of experimental data in SLLV equilibrium of ternary systems with electrolyte. Application to the water + NaCl + 2-propanol system at 101.3 kPa

The SLLV phase equilibria of the water + NaCl + 2-propanol mixture have been determined experimentally at 101.3 kPa by means of a modified recirculating still. The results obtained allow us to study the shape of the phase diagram of the system, to analyze the evolution with temperature of this equilibrium diagram and to show the differences with a similar system such as water + NaCl + 1-propanol. Moreover, the experimental data obtained have been compared with previously published data showing their important inconsistencies and presenting the rules that must be met by the experimental equilibrium data of water + non-volatile salt + organic solvent type systems in each one of the different SLLV, LLV and SLV equilibrium regions.The authors wish to thank the DGICYT of Spain for the financial support of project CTQ2014-59496

Liquid–Liquid, Vapor–Liquid, and Vapor–Liquid–Liquid Equilibrium Data for the Water–n-Butanol–Cyclohexane System at Atmospheric Pressure: Experimental Determination and Correlation

The temperature and the composition of the vapor–liquid–liquid equilibrium (VLLE) and the vapor–liquid equilibrium (VLE) of a ternary mixture of water–n-butanol–cyclohexane were measured at atmospheric pressure (101.32 kPa) in a modified dynamic recirculating still. As found in the literature, the experimental data obtained reveal a ternary azeotrope at 341.86 K with a mole fraction composition of 0.281, 0.034, and 0.685 water, n-butanol, and cyclohexane, respectively. The liquid–liquid equilibrium (LLE) compositions were measured at a constant temperature of 313.15 K and compared with data in the literature collected at other temperatures. Thermodynamic consistency of all the experimental data was demonstrated. The universal quasichemical (UNIQUAC) and the nonrandom two-liquid (NRTL) thermodynamic models were used to correlate the VLE and LLE data, while the original universal functional (UNIFAC) model was used to compare the predicted data.The authors thank the DGICYT of Spain for the financial support of project CTQ2009-13770

Isobaric vapour-liquid-liquid equilibrium and vapour-liquid equilibrium for the system water + ethanol + iso-octane at 101.3 kPa

Poster enviado a Equifase 2002, VI Iberoamerican Conference on Phase Equilibria for Process Design, Foz de Iguazú (Brazil), October 12th to 16th, 2002.Many studies have been carried out in the heterogeneous azeotropic distillation field either by experiment or by simulation. The development of all these studies requires the use of sets of isobaric vapour–liquid–liquid equilibrium (VLLE) data. However, the number of ternary systems with experimental VLLE data is very limited, since it is difficult to find a useful equipment to determine them. One of the most successful applications of the heterogeneous azeotropic distillation is the dehydration of ethanol to obtain absolute alcohol (Pham and Doherty, 1990) using an entrainer. Many different entrainers have been tried in order to improve this process. For example, the use of a hydrocarbon, such as 2,2,4-trimethylpentane (iso-octane), could be of considerable interest to the ethanol dehydration for use in gasohol production (Furzer, 1985)

Influence of the Temperature on the Liquid–Liquid–Solid Equilibria of the Water + Ethanol + 1-Undecanol Ternary System

Liquid–liquid (L–L), solid–liquid (S–L), and solid–liquid–liquid (S–L–L) equilibrium data for the water–ethanol–1-undecanol ternary system have been determined experimentally at (275.15, 278.15, 281.15, 288.15, and 298.15) K and atmospheric pressure. Different shapes of the equilibrium diagrams have been observed depending on the temperature. A region with three phases (S–L–L) is present in the temperature range between (275.15 and 281.15) K. Above 288.15 K, only a L–L region is observed.We thank the University of Alicante (Spain) for the financial support

Phase equilibria of the water + 1-butanol + toluene ternary system at 101.3 kPa

Isobaric vapour–liquid and vapour–liquid–liquid equilibrium data for the water + 1-butanol + toluene ternary system were measured at 101.3 kPa with a modified VLE 602 Fischer apparatus. In addition, the liquid–liquid equilibrium data at 313.15 K were measured and compared with data from other authors at different temperatures. The system exhibits a ternary heterogeneous azeotrope whose temperature and composition have been determined by interpolation. The thermodynamic consistency of the experimental vapour–liquid and vapour–liquid–liquid data was checked by means of the Wisniak’s Li/Wi consistency test. Moreover, the vapour–liquid and the liquid–liquid equilibrium correlation for the ternary system with NRTL and UNIQUAC models, together with the prediction made with the UNIFAC model, were studied and discussed.The authors thank the DGICYT of Spain for the financial support of project CTQ2009-13770

Equilibrium Diagrams of Water + NaCl or KCl + 2-Methyl 2-Propanol at the Boiling Temperature and 101.3 kPa

Experimental equilibrium data of the systems water + NaCl or KCl+ 2-methyl 2-propanol are determined experimentally at boiling conditions and 101.3 kPa. The results obtained permit a study of the shape and different regions of their equilibrium diagrams. A comparison with similar diagrams of other alcohols is made, demonstrating that the ability of NaCl and KCl to split the water + alcohol mixture into two liquid phases increases with temperature and that NaCl splits the alcohols from water in the following order: 2-methyl 2-propanol > 1-propanol > 2-propanol.DGICYT of Spain (project CTQ2014-59496)