Cloud Point Method Research Articles

Three-liquid-phase behavior in the quaternary systems of water + phosphoric acid + diisopropyl ether + tributyl phosphate/methyl isobutyl ketone at 298.2 K

The three-liquid-phase formation in the ternary system of water + phosphoric acid + diisopropyl ether (DIPE) makes the phosphoric acid extraction only effective for acid mass fractions above 0.69. To avoid the undesirable formation of the third phase and enhance acid extraction, particularly at low concentrations, two phase modifiers, methyl isobutyl ketone (MIBK) and tributyl phosphate (TBP), were systematically studied. In order to quantify the synergetic effect of the mixed solvents of DIPE+TBP and DIPE+MIBK, the liquid–liquid equilibria for the quaternary systems of H2O+H3PO4 + DIPE+TBP and H2O+H3PO4 + DIPE+MIBK were fully established for different DIPE/phase modifier (TBP or MIBK) mass ratios (90/10, 70/30, 50/50, and 20/80) at 298.2 K under atmospheric pressure using the cloud point and Othmer graphical method. Othmer-Tobias and Hand correlations were used to fit the tie-line data and assess its consistency. In addition, the behavior of the three-phase zone was also studied as a function of the phase modifiers content. Separation factor (S) and acid distribution (D2) were used to identify the most effective solvent with the potential to enhance phosphoric acid extraction from aqueous solutions.

Unraveling the thermodynamic and clouding interactions of non-ionic micelles of polyethylene glycol tert-octylphenyl ether in water-ethanolamine mixtures: Effect of temperature and composition

The amines are potentially used as co-surfactants in an emulsion. The formation of mixed–micelle in the mixture of non-ionic surfactant polyethylene glycol tert-octyl phenyl ether (TX-114) in the water-ethanolamine mixed solvent system has been studied by the cloud point method at variable concentrations. In absence of any added compound, CP shows concentration-dependent variation. The values of CP in an aqueous medium are found to increase by enhancing their concentration range. The CP values of 1 % TX-114 solutions were found to either remain steady at lower concentrations and elevated at higher concentrations in the presence of secondary and tertiary ethanolamine. The CP decreases with an increasing number of ethanolic groups, while CP increases with alkyl branching. The ethanolamine's amines show CP variation by insinuating between the head part with proton rich amine groups at the micelle layer. The outcomes are examined within the light of a specific additive's capacity to evacuate water from the head gathering of the surfactant micelles. The stability of mixed micelle system has also been evaluated by foam ability and foam stability data.

Study of quaternary liquid-liquid equilibria for systems (water/ methanol/ cyclohexanol+ toluene): Experimental and modelling

The experimental liquid-liquid equilibrium (LLE) data for the extraction of methanol from aqueous solution using mixed solvents (toluene + cyclohexanol) at 291.15 K and atmospheric pressure at the ratios (0, 0.25, 0.4, 0.6, 0.8, 1) was studied. The values of the solvent ratio 0 and 1 led us to study the liquid-liquid equilibrium of the ternary systems (water/methanol/cyclohexanol) and (water/methanol/toluene). The compositions of the coexisting phases were determined by the cloud point method. The tie line data for ternary and quaternary systems were correlated by NRTL model. The Othmer-Tobias and Hand correlations were also tested, to verify the reliability of the experimental tie lines data. The separation factor and the distribution coefficient were calculated from the experimental data to evaluate the effect of using mixed solvents. It was found that the ratio M = 0.4 is the best suited for the liquid-liquid extraction of methanol from water.

Temperature dependence of liquid–liquid equilibria in nonaqueous two–phase systems based on formamide

The cloud–point method was used to determine temperatures located on the binodal surface for several nonaqueous two-phase systems containing formamide, and: {1–pentanol + NaBr} or {1–pentanol + NaNO3}, or {1–butanol + NaNO3}, or {1–butanol + D–sorbitol}, or {acetonitrile + D–fructose}. For comparison purposes, the measurements were made in the water + acetonitrile + D-fructose system. The measured temperatures ranged from about 0 to 90 °C. The experimental data were described by the NRTL model as well as through several empirical equations with the parameters depending on temperature. Finally, the paper discusses the advantages and disadvantages of individual solutions.

Cloud point method applied to the extraction and preconcentration of thiabendazole pesticide from whole grape juice samples and amperometric detection by HPLC.

A cloud point method was developed and applied for the first time to extract and preconcentrate thiabendazole (TBZ) from commercial whole grape juice samples, with determination by high performance liquid chromatography coupled to electrochemical detection (HPLC/EC), using a cathodically pretreated boron-doped diamond electrode (BDD). The best conditions for extraction and preconcentration of TBZ by cloud point extraction (CPE) were performed at pH 6.0, by adding 1 mL of the surfactant Tergitol TMN-6 at 10% (mass-to-mass ratio), without heating (at 27 °C) and ultrasonic stirring time of (20 kHz) for 60 min. The HPLC/EC determination was duly validated in a C8 column, in mobile phase with a 69 : 31 ratio (V/V) of phosphate buffer (pH 7.0):ACN, at a flow rate of 1.2 mL min-1 and electrochemical detection with BDD electrode by applying 1.40 V × Ag/AgCl (3.0 mol L-1). Under these conditions, the procedure showed a preconcentration factor (FC) of 21.7, and limits of detection (LOD) and quantification (LOQ) of 6.64 × 10-9 mol L-1 (or 1.33 μg L-1) and 1.66 × 10-8 mol L-1 (or 3.34 μg L-1), respectively. The method provided a percent recovery of 81% to 98%, with a coefficient of variation between 3% and 15%.

Higher alcohols as cosolvents of mixtures of ethanol and soybean oil: Solubility and physical properties of ternary systems

Mixtures of soybean oil (SO) and ethanol (EtOH) are of interest for several applications, such as the addition of the mixtures to diesel, the production of ethyl esters (ethyl biodiesel) from SO and the extraction of vegetable oils with a renewable solvent. However, the solubility between the components of this mixture is limited, which may hinder the possible applications. Thus, the present study aimed to determine the solubility of mixtures composed of SO and EtOH with the addition of cosolvents, n-butanol (nBut) and isoamyl alcohol (IAA), which are higher alcohols present in fusel oil, a coproduct of the production of EtOH. The physical properties of the ternary mixtures were also determined, which are necessary data for proposing the use of these renewable inputs. The regions of phase separation for the systems were determined using the cloud point method at constant temperature (25, 40 and 55 °C). The physical properties, density (ρ, kg·m−3) and dynamic viscosity (η, mPa·s) were experimentally determined for the binary (EtOH + nBut and EtOH + IAA, temperatures from 20.0 to 70.0 ± 0.1 °C) and ternary (SO + EtOH + nBut and SO + EtOH + IAA, 25.0, 40.0 and 55.0 ± 0.1 °C) mixtures. The experimental ρ data were described mathematically by the simple mixing rule (SMR) and the Jouyban-Acree (JA) model. For the description of η, the modified Kay rule (MKR), the Kendall and Monroe (KM) model, the Grunberg-Nissan (GN) model and the JA model were considered. Regarding the binary mixtures, the SMR and the GN model showed the lowest average relative deviation (ARD) values, 0 to 0.31% for ρ and 0.21 to 5% for η. For the ternary systems, the JA model best described the behavior of both physical properties (ARD from 0.02 to 4.51% for ρ and from 0.85 to 7.14% for η). Both cosolvents enabled the reduction of the immiscibility region, with similar performance in the evaluated temperature range.

Liquid–liquid phase separation in binary mixtures of quaternary alkylammonium chlorides with carboxylic acids

We reported the phase separation measurements of mixtures obtained from choline, tetramethylammonium and tetraethylammonium chlorides with methacrylic (MAA), butyric (BA) and isobutyric (IBA) acids as solvents. Liquid-liquid equilibrium (LLE) experiments were performed under atmospheric pressure in a temperature range of 287–403 K using cloud-point method and the data were correlated with the Non-Random Two Liquid (NRTL) solution model. The density, the viscosity, the Kamlet-Taft and the solvent polarity (ET(30)) parameters were measured for coexisting liquid phases. The applicability of the obtained binary biphasic system in extraction process, particularly purification of MAA from a phenolic inhibitor, was demonstrated.

Extractive desulfurization of thiophene by tetraethylene glycol at T = 298.15 to 313.15 K and liquid–liquid phase equilibrium study

ABSTRACT This study provides the complete liquid–liquid equilibrium (LLE) data including the solubility curves and tie-lines for heptane + thiophene + tetraethylene glycol and cyclohexane + thiophene + tetraethylene glycol ternary mixtures at 298.15–313.15 K under a pressure of 83.4 ± 1 kPa. The experimental data were obtained by the cloud point method. Type 1 phase behavior is observed for the systems. The observed behavior was interpreted based on the type and nature of the interactions between the components. The capability of tetraethylene glycol in extractive desulfurization of thiophene from liquid fuel is evaluated by determining the solute distribution coefficient and selectivity. The high values of the selectivity show that tetraethylene glycol is a good candidate for this purpose. The investigation of the effect of temperature on the area of the biphasic region and distribution ratios shows that the extraction process can be performed at room temperature. The experimental data were successfully correlated with the NRTL model. The reliability of the correlation results was checked by using a Graphical User Interface (GUI) for the representation of Gibbs energy of mixing (GM). The root mean square deviation (RMSD), a measure of the precision of the correlations, ranges from 0.0022 to 0.0040.

Liquid-liquid equilibria of the ternary systems water + C1 – C3 alcohols + dimethyl adipate at 298.15 K and atmospheric pressure: Experimental data and modeling

The aim of this study was to examine the possibility of using a green organic solvent, dimethyl adipate (DMA), as a separation agent in the extraction of different alcohols from aqueous solutions. For that purpose, the liquid–liquid equilibria (LLE) of four ternary systems were analytically determined at 298.15 K and atmospheric pressure using stirred and thermo-regulated cells: {water + methanol + dimethyl adipate (DMA)}, {water + ethanol + DMA}, {water + 1-propanol + DMA}, {water + 2-propanol + DMA}. Phase diagrams for these four ternary systems were obtained by determining a binodal curve and tie-lines data using a visual cloud-point method, but also gas chromatography. Distribution coefficients and separation factors were calculated for the immiscibility region. Hand and Othmer-Tobias correlations were used to examine the reliability of the tie-line data. In addition, the experimental ternary LLE data were correlated with the UNIversal QUAsiChemical (UNIQUAC) activity coefficient models. The obtained results showed that DMA is a suitable candidate for the extraction of methanol, ethanol, 1-propanol, and 2-propanol from water. With some alcohols, this potential is more noticeable than with others. The potential of DMA as a separation agent is increasing in the following sequence: methanol < ethanol < 2-propanol < 1-propanol, and that also could be noticed from the selectivity values that also increase in this sequence. The UNIQUAC model proved as successful in correlating the LLE data.

Performance of Organic Salts as Salting-Out Media on Recovering Nicotine from Water

Three degradable organic salts, sodium formate (NaCHO2), sodium succinate (Na2C4H4O4), and sodium citrate (Na3C6H5O7), were evaluated for the extraction of nicotine from aqueous solutions by forming two-phase systems. The detailed phase diagrams, including the binodal curves and tie-lines, were experimentally determined at 298.15 K and atmospheric pressure by the cloud point method. The three empirical equations including Merchuk, Pirdashti, and Hu models gave a perfect correlation of the experimental binodal data, and the reliability of liquid–liquid equilibrium data was evaluated using the Othmer–Tobias and Bancroft equations. It could be found that all adopted organic salts promoted the expansion of two-phase regions and had a high partition yield for nicotine extraction from water. The relative tendency of the anions to form aqueous two-phase systems being C6H5O73– > C4H4O42– > CHO2– was consistent with their valence order, which could be explained by the Gibbs hydration free-energy theory. Furthermore, the salting-out ability of salt anions was also in accordance with the parameter order (Na3C6H5O7 > Na2C4H4O4 > NaCHO2) of the calculated effective excluded volume. Increasing the temperature from 298.15 to 318.15 K and the pH value from 8.0 to 11.0 at 298.15 K was conducive to the two-phase formation of the ternary nicotine + Na3C6H5O7 + water system to increase the distribution coefficients and recovery percentages of nicotine. Computational thermodynamics of cloud point indicated that the more negative Gibbs free energy with temperature promoted the desolvation of nicotine to migrate preferentially to the top phase. It was concluded that degradable organic salts would be effective for nicotine extraction at an industrial scale.

Simultaneous extraction and enrichment of sunset yellow dye in an aqueous two-phase system

Sunset Yellow (SSY) is a neutral dye commonly used in the textile, cosmetic, pharmaceutical and food industries. This is found in the effluent streams of these industries. In this study, the extraction of this dye is analyzed using a polymer-salt aqueous two-phase system (ATPS). Classical extraction processes are based on contacting an organic phase with an aqueous phase. Our focus is on developing a green process where the use of an organic solvent is avoided. Polyethylene glycol of molecular weights 600 and 6000 are chosen as two candidates for the polymer phase and sodium sulfate as the salt phase. The propensity of the dye to selectively transfer into the polymer-rich phase is exploited to study the extraction process. The binodal curves are experimentally obtained using the cloud point method. The composition of salt and polymer was chosen so as to ensure that the volume of the polymer-rich phase is relatively low in the two-phase system. This choice results in obtaining a high concentration of the dye in the polymer-rich phase from a dilute solution of dye in the salt-rich phase. This is a spontaneous energy-efficient process which avoids the use of any other energy-intensive processes such as evaporation. The dye extraction is studied experimentally in batch mode where 75% extraction occurs in 2 h when the mass transfer is only by diffusion. To accelerate the process a milli channel is used under stratified flow conditions where the length scales are decreased, and 77% extraction is achieved in around 3 min. ATPS is characterized by low interfacial tension and obtaining slug flows in a microchannel is a challenge. We show that by using a milli channel we can lower the capillary number and obtain slug flow at higher flow rates. The internal circulations present in the slugs help in an accelerated mass transfer and 85% extraction is achieved in the PEG6000-salt system in 3 min.

Measurement and Correlation of the Liquid-Liquid Equilibria of Tertiary-Butyl Alcohol – Water – Benzene System at 30°C and 1 Atmosphere Pressure

The Liquid-Liquid equilibria of Tertiary-Butyl Alcohol – Water – Benzene System were measured experimentally at 30°C and 1atm pressure. The experimental binodal curve compositions were obtained using the cloud point method. The compositions of the two equilibrium phases were analysed using Agilent 7820A series Gas Chromatograph. The consistency of the experimental data was determined using the Hand, Othmer-Tobias and Bachman- Brown correlation equations while the plate point was determined using the Treybal’s method. The effectiveness of the solvent in the extraction was determined by calculating the distribution coefficients and separation factors. The experimental tie-line data were correlated with the Universal Quasi-Chemical (UNIQUAC) and Non-Random Two Liquid (NRTL) activity coefficient models. Also, the deviation between the experimental and calculated equilibrium compositions were calculated using the root mean squared deviation equation. The UNIQUAC predicted data gave a closer resemblance to the experimental.

Novel method for determination of Vitamins E and C by Cloud-point extraction

A new, simple, fast and accurate spectrophotometric method has been found for the determination of vitamin E and C in their complexes by cloud point method. The Beer-Lambert Law was complied with for a range of concentrations ranging from 5-50 µg.ml-1 for vitamin E and 5-40 µg.ml-1 for vitamin C, and the value of the correlation coefficient R2: 9987 and 9997, and the value of the molar absorption coefficient Ԑ: 24421.25 and 10760.93, Sandel's sensitivity was 0.0176 μg.cm-2 and 0.0164 μg.cm-2 for vitamins E and C, respectively, while the detection limit was 0.0008 and 0.0009, and the quantitative limit was 0.0026 and 0.0030 for vitamins E and C, respectively. The method has been successfully applied for the determination of vitamin E and C in their pure forms and pharmaceutical preparations.

Fish-shaped diagram of liquid–liquid equilibria for the mixtures water + n-alkane + n-alkyl polyglycol ether

The aim of this work is to determine the fish-shaped diagram of liquid–liquid equilibria (LLE) of ternary mixtures of water + n-alkane + n-alkyl polyglycol ether (CiEj) using a cloud point method with laser scattering technique. n-Octane and n-dodecane were selected as the n-alkanes, and 2-butoxyethanol (C4E1) and 2-(2-hexyloxyethoxy)ethanol (C6E2) were selected as the n-alkyl polyglycol ethers. In the measurements of the ternary mixtures, the CiEj free basis mass fraction “α” of n-alkane was changed from 0.1 to 0.9. The experimental fish-shaped diagrams were evaluated by comparing the experimental cloud point data with the fish-shaped diagrams as well as the phase boundaries of tie-line and tie-triangle data in the mixtures of water + n-octane + C4E1 and water + n-dodecane + C6E2 reported in the literature. X-points where the fish body and fish tail intersect were determined from the experimental cloud points, as well as the upper and lower critical point temperature of the fish-body. Changes in the phase diagram and X-points with different n-alkanes, CiEj, and the value of α were analyzed using the experimental data. The LLE data of the mixture of water + C6E2, as one of the binary components of the ternary mixture, was also measured.

Liquid – liquid equilibria in binary and ternary systems of phenol + hydrocarbons (n–dodecane or n–hexadecane) and water + phenol + hydrocarbons (n–dodecane or n–hexadecane) at temperatures between 298K and 353K

This study reports liquid–liquid equilibrium (LLE) and liquid–liquid–liquid equilibrium (LLLE) data for binary (phenol + n-dodecane, or n-hexadecane) and ternary (water + phenol + n-dodecane, or n-hexadecane) systems measured under atmospheric pressure. The compositions of coexisting phases were determined with analytical and cloud point methods at temperatures 298 K – 353 K. The Non–Random Two–Liquid (NRTL) excess Gibbs energy model was employed to correlate the measured systems. The binary interaction parameters were regressed using analytical LLE and cloud point data. In addition, the parameters were also calculated using the binary LLE data combined with the isothermal vapor–liquid data from the literature applying the NRTL–RK (Redlich–Kwong) property method. The average absolute deviations in liquid mole fraction obtained with the NRTL model (using six adjusted parameters) for the LLE and VLE experimental data were 0.006 and 0.014 respectively. The phase equilibria of binary phenol + hydrocarbon (n-dodecane or n-hexadecane) systems were modeled at the temperature range of 313 K – 573 K.

Front Cover: Application of a synthetic ligand in rapidly synergistic cloud point method for separation and preconcentration trace amounts of copper of water samples

DOI: 10.1002/sscp.202100029 The cover picture shows the use of the rapidly synergistic cloud point extraction method. The selection of a suitable ligand (here 4-BPDC) can lead to a low detection limit and good sensitivity in the UV/Vis spectrophotometry technique, which it is an advantage in addition to ease of operation, use of inexpensive materials and the easy access of this method for the determination of trace amounts of copper in water samples.

Application of a synthetic ligand in rapidly synergistic cloud point method for separation and preconcentration trace amounts of copper of water samples

AbstractIn this study, a rapidly synergistic cloud point extraction method was used to separate and pre‐concentrate small amounts of copper ions. Synthetic ligand 4‐benzylpyridine dithiocarbamate as a complexing agent, non‐ionic surfactant (Triton X‐100) as an extractant, and octanol as a synergic reagent were used. Parameters affecting copper ion extraction such as pH, ligand concentration, octanol volume, type of diluent solvent, stirring speed and time, surfactant concentration, and the effect of ionic strength were investigated. Ultraviolet‐visible spectrophotometry was used to measure the absorption of copper complex. Under optimal conditions, limit of detection, preconcentration factor, and relative standard deviation for copper were 1.4 × 10–3 μg /mL, 10 and 2.1, respectively. Also, the relative extraction efficiency of copper extraction in real samples was greater than 97%.

Thermally induced phase separation in semicrystalline polymer solutions: How does the porous structure actually arise?

Thermally-induced phase separation in semicrystalline polymer – solvent systems is revisited to analyze the formation of membrane precursors beyond the existing concepts. It is argued that the phase diagrams of such systems should include a commonly overlooked curve describing the solubility of a low-molar-mass liquid in the amorphous regions of a semicrystalline polymer. To illustrate our approach, the binary mixtures of isotactic polypropylene with dioctyl phthalate (good solvent), dibutyl phthalate (poor solvent), and their ternary mixtures are considered. Quasi-equilibrium phase diagrams are constructed using an original optical method and analyzed in terms of phenomenological thermodynamics, including the previously poorly studied region below the polymer crystallization temperature. The proposed scenario of morphology development during the cooling of pre-homogenized mixtures is illustrated with the data of optical and scanning electron microscopy, small-angle X-ray scattering, differential scanning calorimetry, and cloud point methods. It is found that cooling down and subsequent solvent extraction generally lead to the formation of capillary-porous bodies with large (micron-sized) pores formed via the liquid-liquid phase separation and small (submicron-sized) pores appeared due to the microphase separation of amorphous polymer regions under strain imposed by the presence of crystallites. The composition range most suitable for the formation of filtration membrane precursors extends between the polymer mass fraction values corresponding to the upper critical solution point and “monotectic” point, in which the solubility curve meets the curve of complete polymer amorphization.

Measurement, Correlation and Prediction of LLE Data for the Ternary System Water + Lactic Acid + Diethyl Ether at 293.2 K

In this study, tie-line points and solubility data were experimentally measured for the ternary mixture (water + lactic acid + diethyl ether) at T = 293.2 K and atmospheric pressure. UNIFAC calculations predicted that lactic acid and diethyl ether do not form an azeotrope. The mass fractions of organic and aqueous layers were determined by acid-base and the Karl Fisher titrations. Cloud point method verified that the LLE behavior of the studied system is Type-1. The reliability of the tie-line points was demonstrated by the Othmer–Tobias and Hand plots. Thermodynamic correlation of tie-line data was done by NRTL model and the obtained binary interaction parameters were tested after validation. The experimental and correlated data had very good accordance (rmsd = 0.88 %). Extraction quality of diethyl ether was investigated using the calculation of distribution coefficients and separation factors over the immiscibility area. Separation factors decreased from 1.93 to 1.13 when aqueous mass fraction of lactic acid increased from 0.070 to 0.305. However, distribution coefficient increased from 0.07 to 0.12 in the same region. The study shows that the extraction of lactic acid is possible in all investigated feeds at 293.2 K.

Pressure drop particle precipitation from a quasi-incompressible, ternary and liquid mixture

We found a quasi-incompressible and liquid mixture of ibuprofen, water and acetone, that enables the crystallization of ibuprofen particles by decreasing the pressure from 15MPa to ambient pressure (~0.1MPa). We measured the solubility of ibuprofen in the mixture as a function of the acetone/water-ratio for pressures of 0.1MPa, 5.5MPa and 15MPa and at 308K using the cloud point method. Based on the solubilities, binodal compositions of the ternary system were modelled using the NRTL-SAC model. The solubility of the drug in the mixture increases with increasing pressure at constant acetone/water-ratio. This pressure sensitive solubility can be exploited for the crystallization of ibuprofen particles via a pressure-drop approach. A pressure-drop from 15MPa to ambient pressure ~0.1MPa can result in a supersaturation of up to 1.43.