Liquid-liquid Equilibrium Phase Diagrams Research Articles

Customizable cholinium-based aqueous biphasic systems as ecofriendly extraction platform for removal of pesticide from wastewaters

This study explores the use of a series of cholinium ionic liquids (ILs) or salts in combination with polypropylene glycol 400 to form aqueous biphasic systems (ABS) for extracting various polarity pesticides (dicamba, clomazone, pyraclostrobin, and deltamethrin) from water. We assessed five cholinium-based salting-out agents ([Ch][DHP], [Ch]Cl, [Ch][Ac], [Ch][Lac], and [Ch][Nic]), chosen for their structural diversity and unique properties, such as high salting-out potential and different ability to undergo specific interactions. Liquid-liquid equilibrium phase diagrams were established, and partition experiments were conducted to evaluate extraction efficiency. Different partition patterns were obtained for studied pesticides, with [Ch][DHP] demonstrating the highest efficiency exceeding 90 % for each target pesticide due to its strong salting-out ability. On the other hand, more diverse partition trends due to specific interactions were obtained for low-melting cholinium-ILs ABS. The effect of pH and temperature on the partitioning behavior in [Ch][Ac]-based ABS highlighted the cholinium ILs extraction system's customizable nature. Focusing on [Ch]Cl for its eco-friendly aspects, widespread availability and excellent extraction performance, we optimized parameters for the removal of pesticides from real samples, applying the technology to spiked agricultural wastewater with an extraction efficiency of over 99 %. Our findings demonstrate the potential of cholinium-based IL-ABS in reducing environmental pollution through efficient pesticide extraction.

A comparative study on liquid phase equilibria of aqueous mixtures of two structurally close carboxylic acids with sec-amyl alcohols at 298.2 K

This research reports the results of measurements on liquid-liquid equilibrium (LLE) for the four ternary systems of (water + butyric or 3-methylbutyric acids + sec-amyl alcohol) and (water + butyric or 3-methylbutyric acids + sec-isoamyl alcohol) at 298.2 K and 0.1 MPa. According to the measured solubility and tie-line data, the related phase diagrams for the studied systems were plotted. Due to the strong structural similarity of the studied system's constituents, the influence of the chemical structures of the acids and the solvents on the LLE behavior was comparatively studied. The ternary systems display two forms of LLE phase diagrams. The aqueous systems of butyric acid and the two structural isomers (sec-amyl alcohol and sec-isoamyl alcohol) exhibit type-1 phase behavior of LLE, whereas the type-2 behavior was observed for the systems containing the branched chain carboxylic acid (3-methylbutyric acid). The activity coefficients models of UNIQUAC and NRTL fit the measured tie line-data. According to the measured LLE data, the values of the models' binary interaction parameters were optimized using MATLAB Fminsearch function. Based on the experimental data, the mass distribution coefficients and selectivity were evaluated and systematically compared for the studied systems. Finally, reliability of the obtained NRTL parameters was checked using topological analysis connected to the Gibbs tangent plane test.

Liquid-liquid equilibrium for methyl butyl ketone + o-, m-, p-cresol + water ternary systems and COSMO-SAC predictions

The liquid–liquid equilibrium (LLE) data for the three ternary systems, methyl butyl ketone (MBK) + o-, m-, p-cresol + water, were measured at 333.2 K and 353.2 K under 101 kPa in this work. Distribution coefficient and selectivity for cresols were calculated from the experimental tie-line data to evaluate the performance of MBK extracting cresols from the aqueous solution. The experimental tie-line data were correlated by the NRTL and UNIQUAC activity coefficient models, and both models showed good agreement with the experimental data. The COSMO-SAC model (conductor-like screening model for segment activity coefficient) was employed to predict LLE phase diagrams for the studied systems with root mean square deviations less than 3%.

Liquid–liquid equilibrium data and correlation for quaternary systems of acetic acid + water + methyl acetate + p-xylene at 313.2 K

The experimental liquid–liquid equilibrium (LLE) data of the quaternary (acetic acid+water+p-xylene+methyl acetate) system was investigated at 313.2K and atmospheric pressure. This research is aimed to examine the potential of the mixture of methyl acetate and p-xylene, which available as the remaining substances in terephthalic acid production, to be prospective extracting solvent for the acetic acid dehydration. LLE phase diagrams at different ratio of p-xylene to methyl acetate were presented for this quaternary system. The results showed that an enlargement of the LLE two-phase region occurred with increasing p-xylene to methyl acetate mass ratio in the initial solvent phase. The distribution coefficient and selectivity for the extraction of acetic acid were also obtained to evaluate the capability of solvent. LLE data were sufficiently correlated by Othmer-Tobias and Bachman equations. The experimental results were used to obtain binary interaction parameters as correlated by the non-random two liquid (NRTL) and universal quasi-chemical theory (UNIQUAC) equation models. The root mean square deviations (RMSD) values as low as 0.0119 and 0.0128 were calculated for NRTL and UNIQUAC, respectively; indicating excellent results for both models were suitable for the determination of LLE data of this quaternary system.

Thermodynamics and separation process for quaternary acrylic systems

Vapor‐liquid equilibrium (VLE) and liquid‐liquid equilibrium (LLE) data of binary and ternary acrylic systems were systematically measured. Subsequently, VLLE phase diagrams of binary systems, tridimensional VLE phase diagrams of methyl acrylate (MA)‐methanol (Me)‐H2O ternary system, and quaternary LLE phase diagrams of MA‐Me‐H2O‐methyl acetate (MeOAc) system were constructed. These diagrams clearly demonstrated the effects of temperature on phase equilibrium. The experimental data was fitted by the NRTL and UNIQUAC models, and the best‐fitted parameters were used to predict interaction properties of ternary and quaternary mixture. Therefore, the phase equilibrium data were provided as reference for the design of acrylic systems rectification or extraction process. Residue curve was mapped out for MA‐Me‐H2O system through Aspen plus software. Finally, using thermodynamics and residue curve as theoretical basis, two novel separation processes were proposed and applied to the quaternary acrylic systems. © 2015 American Institute of Chemical Engineers AIChE J, 62: 228–240, 2016

Liquid–liquid equilibrium data for ternary aqueous mixtures containing 1-pentanol and 2-methyl-1-propanol at (298.15, 323.15, and 348.15) K

Liquid–liquid equilibrium (LLE) tie-line data of ternary aqueous mixtures containing 1-pentanol and 2-methyl-1-propanol were reported separately at T=(298.15, 323.15 and 348.15)K under normal pressure in this article. Meanwhile, a type II LLE phase diagram for the investigated system at each constant temperature was given and the effect of temperature on LLE phase behavior was discussed. The well-known Othmer–Tobias, Bachman and Hand correlations were used to test the reliability of the experimental data. In addition, both the NRTL (α=0.2) and UNIQUAC models were applied to correlate the measured data to obtain the binary interaction parameters between each pair of components valid for the range of temperature studied. All of the root-mean-square deviation (RMSD) between the measured and calculated data was less than 0.0056. The results of this study can be used to design and optimize the liquid–liquid separation process of aqueous solution containing 2-methyl-1-propanol and 1-pentanol.

Measurement and correlation of liquid–liquid equilibrium data for 2-methyl-1-propanol + 2-propanol + water at several temperatures

Liquid–liquid equilibrium (LLE) tie-line data for 2-methyl-1-propanol+2-propanol+water were determined experimentally under atmospheric pressure over the temperature range of (298.15–348.15)K, respectively. A type 1 LLE phase diagram for the ternary system studied was got and the influence of temperature on the phase diagrams was reported, too. The Othmer–Tobias and Bachman correlations were applied to check the accuracy of the LLE data reported. Moreover, the experimental data got were regressed with the NRTL (α=0.2) and UNIQUAC activity coefficient models, meanwhile, the binary interaction parameters between each pair of components in the studied system were obtained. The root-mean-square deviation (RMSD) between the measured and calculated data was less than 0.0032. The results can be used to design and optimize the separation process of aqueous solution containing 2-propanol and 2-methyl-1-propanol.

Solubility of Aliphatic Hydrocarbons in Piperidinium Ionic Liquids: Measurements and Modeling in Terms of Perturbed-Chain Statistical Associating Fluid Theory and Nonrandom Hydrogen-Bonding Theory

Ionic liquids (ILs) reveal many unique properties which make them very interesting for applications in modern "green" technologies. For that reason, detailed knowledge about correlations between the ions' structure, their combinations, and the bulk properties is of great importance. That knowledge can be accessed by reliable measurements and modeling of systems with ILs in terms of various theoretical approaches. In this paper we report new experimental results on liquid-liquid equilibrium (LLE) measurements of 10 binary systems composed of piperidinium ILs [namely, 1-propyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide and 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide] and aliphatic hydrocarbons (n-hexane, n-heptane, n-octane, cyclohexane, and cycloheptane). Moreover, new results on liquid density of pure 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide are presented. Upper critical solution temperature type of phase behavior for all studied systems was observed. Decrease of solubility of n-alkane with an increase of its alkyl chain length and increase of solubility when changing linear into cyclic structure of hydrocarbon were detected. LLE modeling of investigated systems was performed in terms of two modern theories, namely, perturbed-chain statistical associating fluid theory (PC-SAFT) and nonrandom hydrogen-bonding theory (NRHB). Pure fluid parameters of the models were obtained from fitting of experimental liquid density and solubility parameter data at ambient pressure and tested against high pressure densities. Then literature values of activity coefficients of n-alkanes and cycloalkanes at infinitely diluted mixtures with ILs were used to optimize binary interaction parameters of the models. Finally, the LLE phase diagrams were calculated with average absolute relative deviations of 4.1% and 3.4% of the IL mole fraction for PC-SAFT and NRHB, respectively. The PC-SAFT and NRHB models were both able to capture phase behavior in a qualitative manner. Both models predict the order in which solubility of hydrocarbon in the IL increases, including the effects of chain length of n-alkane as well as chain length of alkyl substituent in piperidinium cation. Moreover, predicted solubility of cycloalkanes is also higher than that of respective n-alkanes. Our results suggest that the presented approach of PC-SAFT and NRHB modeling can be successfully applied to cross-associating systems as well. In summary, we have shown that relatively good results can be obtained for such complex systems by using quite simple molecular models and combining rules. To the best of our knowledge, this is the very first paper in which such equation-of-state modeling has been adopted for systems with ILs.

Liquid−Liquid Equilibria for the Quaternary Systems of Water + Dimethyl Sulfoxide + 1-Pentanol + NaBr or + KBr

The effect of sodium bromide and potassium bromide on the liquid−liquid equilibrium (LLE) of the water + dimethyl sulfoxide + 1-pentanol system has been investigated at temperatures from (283.15 to 323.15) K under atmospheric pressure. The experimental results of the two quaternary systems (salt-containing) and the original ternary system (salt-free) show that the salt effect could be evaluated. The influence of sodium bromide is slightly more significant than that of potassium bromide. The compositions of the conjugated phases were correlated with the three-contribution electrolyte-NRTL model. In general, the model reproduces reasonably the LLE phase diagrams.

Phase equilibria of (water + levunilic acid + alcohol) ternary systems

Liquid–liquid equilibrium (LLE) data of the solubility (binodal) curves and tie-line end compositions were examined for mixtures of {(water (1) + levunilic acid (2) + isoamyl alcohol or hexanol or decanol (3)} at 298.15 K and 101.3 ± 0.7 kPa. A type-1 LLE phase diagram was obtained for this ternary system. The relative mutual solubility of levunilic acid is higher in the water layers than in the isoamyl alcohol or hexanol or decanol layers. The reliability of the experimental tie-line data was confirmed by using the Othmer–Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents. Furthermore, LSER model equation has been obtained to calculate distribution coefficients ( d 2) and separation factors ( s) with R 1 2 = 0.963 and R 2 2 = 0.844 .

Salting effect on the liquid–liquid equilibria for the ternary system water + N-methyl-2-pyrrolidone + 1-pentanol

Liquid–liquid equilibrium (LLE) data have been measured for one ternary system of water + N-methyl-2-pyrrolidone + 1-pentanol, and three quaternary systems of water + N-methyl-2-pyrrolidone + 1-pentanol + sodium chloride, +potassium chloride, or +potassium acetate at temperatures 283.15 and 323.15 K under atmospheric pressure. The liquid-phase splitting for ternary system of water + N-methyl-2-pyrrolidone + 1-pentanol can be enhanced by adding the same percentage of salts (sodium chloride, potassium chloride, or potassium acetate) and the influence follows the order of sodium chloride > potassium chloride > potassium acetate. The experimental data were also compared with the values calculated by the Electrolyte-NRTL model. In general, the model reproduces reasonably for the LLE phase diagrams.

(Liquid + liquid) equilibria of (water + propionic acid + 2-ethyl-1-hexanol): Experimental data and correlation

(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + 2-ethyl-1-hexanol) were determined at atmospheric pressure over the temperature range of (298.15 to 308.15) K. A type-1 LLE phase diagram was obtained for this ternary system. The LLE data were correlated fairly well with UNIQUAC model, indicating the reliability of the UNIQUAC equation for this ternary system. The average root mean square deviation between the observed and calculated mole fractions was 1.57%. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvent.

Visualization of High-Dimensional Liquid−Liquid Equilibrium Phase Diagrams

Liquid−liquid extraction is usually used along with other separation processes for the recovery of pure components. It is desirable that the liquid−liquid equilibrium (LLE) phase behavior, which is the thermodynamic basis for liquid−liquid extraction, be represented in a phase diagram. This is because the visualization of process limitations has a crucial role in the construction of feasible separation schemes for achieving the overall separation objective. However, because most applications involve multicomponent mixtures, visualization of the LLE phase diagram in its entirety becomes difficult or even impossible. Therefore, a visualization approach to represent high-dimensional LLE phase diagrams based on projections and cuts to reduce dimensionality is proposed. In such an approach, the liquid−liquid immiscibility regions are represented as a collection of projected tie lines. By superimposing the resulting diagram with any other map of process boundaries in composition space, such as a solid−liquid eq...