Binodal Research Articles

New insight into 3-picoline—deuterium oxide (D2O) mixtures of limited miscibility with the lower critical consolute temperature

Coexistence curves in mixtures of limited miscibility with the lower critical consolute temperature (LCT), of 3-picoline with deuterium oxide (D2O), and D2O/H2O have been determined. They were tested with respect to the order parameter, the diameter of the binodal, and coordinates of the critical consolute point (critical temperature {T}_{mathrm{C}} and critical concentration {phi }_{mathrm{C}}). Studies were carried out using the innovative method based on the analysis of relative volumes occupied by coexisting phases, yielding high-resolution data. The clear violation of the Cailletet-Mathew law of rectilinear diameter for the LCT mixtures of limited miscibility is evidenced. For the order parameter, the new distortion-sensitive analysis method yielded the evidence for the model-value of the order parameter critical exponent beta =0.326pm 0.003, up to ca. 1 K from {T}_{mathrm{C}}. Finally, the simple & easy method for determining the critical concentration by testing relative volumes of coexisting phases (or alternatively fractional meniscus heights, h) is presented. The significance of the invariant value {h}_{mathrm{C}}=hleft({T}_{mathrm{C}},{phi }_{mathrm{C}}right)=1/2 is highlighted. The appearance of the milky & bluish critical opalescence is also shown.Graphical abstract

Liquid-liquid phase equilibria for the ternary (neopentyl glycol + sodium formate + water) system

ABSTRACT. Liquid–liquid equilibrium data and the phase diagrams were measured for the ternary (neopentyl glycol + sodium formate + water) system at various temperatures of 303.15, 313.15 and 323.15 K. The effect of temperature on the conjugate phase and the tie-line length of the investigated system have been studied. The results showed that the length of the tie-line increases and the two-phase area was slightly increased by decreasing temperature. The fitting parameters of the Pirdashti and Merchuk equations were obtained with the temperature dependence expressed in the linear form, respectively. Compared with the Pirdashti equation, the binodal curves were satisfactorily described using the Merchuk equation at T = (303.15, 313.15 and 323.15) K, and the critical points at different temperatures were estimated by extrapolation. Furthermore, the Hand, Othmer-Tobias and Bachman models were used for the correlation of the phase behavior of the studied system. According to the reported correlation coefficients values, it was found that the measured tie-line data have acceptable consistency and the better fitness was with Othmer-Tobias equation. 
 
 KEY WORDS: Liquid–liquid equilibrium, Neopentyl glycol, Phase diagram, Merchuk
 Bull. Chem. Soc. Ethiop. 2022, 36(4), 915-922. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i4.16

A Novel Ethanolic Two-Phase System Based on Deep Eutectic Solvents and Amphiphilic Copolymer for the Extraction of Neohesperidin and Naringin from the Pomelo Peel.

A novel ethanolic two-phase system (ETPS) composed of Pluronic®L-64 (PL 64) and deep eutectic solvents (DESs) was constructed for the separation of two similar flavonoids of naringin (Nar) and neohesperidin (Neo) from the pomelo peel. The selectivity (S) data showed that DES prepared from tetrabutylammonium bromide (N4444Br) and glycerol (Gly) had the optimal distribution efficiency for Nar and Neo standards. A binodal curve of N4444Br-Gly/PL 64/ethanol system fitted to the nonlinear Merchuk relationship showed that the biphasic region was narrow for ETPS. The influences of the mass ratio of DESs and PL 64, DES concentration, PL 64 concentration, molar ratio of DESs, temperature, phosphate buffer solution, and ethanolic pH were studied in single-factor experiments. Under the optimal conditions, the maximum extraction efficiency (ENar = 68.32%, ENeo = 86.09%), partition coefficient (KNar = 6.66, KNeo = 19.13), and S (2.88) were obtained in the DESs-rich (bottom) phase. N4444Br-Gly, Nar, and Neo with recovery yields of 78.12%, 66.61%, and 68.03%, respectively, had been recovered using D101 macroporous resin. This proposed ETPS is efficient and environmentally friendly and is expected to avail meaningful references for the separation of natural products with similar structures.

Experimental and Theoretical Studies on the Phase Behavior of Aqueous Solutions of Structurally Controlled Hyperbranched Poly(N-isopropylacrylamide)s

Structurally controlled hyperbranched poly(N-isopropylacrylamide)s (HB-PNIPAMs) having different branching densities were systematically synthesized, and their phase behavior, i.e., lower critical solution temperatures (LCSTs), in water was studied. The branching significantly affects LCSTs, and they decrease with an increase in the branching density. The origin of the experimental results was theoretically analyzed on the basis of the concept of cooperative hydration, which is the sequential formation of hydrogen bonds between polymer chains and water molecules. Assuming that the cooperativity of hydration does not propagate beyond the branching points, we calculate the spinodal curves, binodal curves, and critical points and construct the phase diagrams. The degrees of hydration of the subchains, branching points, and end groups are also calculated to examine their hydration effect on the phase behavior. In this investigation, we consider the following two situations: (i) only subchains can be hydrated, and (ii) every part of HB polymers, including branching points and end groups, can be hydrated. We compare the theory with the reported observations of the cloud points of structurally well-controlled HB-PNIPAMs in water. Qualitative agreement is obtained by using the same value of cooperativity as the study of aqueous solutions of linear PNIPAMs. We also show that the hydration behavior of the end groups and the branching points strongly influences the phase behavior and illustrate that the binodal temperature is determined by the balance between the effect of promoting hydration by their hydration and suppressing hydration due to the inhibition of cooperative hydration by the branching points.

To the possibility of experimental estimation of the diffusion spinodal position of binary mixture with LCST via pulsed heating method

In this paper, we present new data on non-stationary heating of a platinum wire probe, immersed in a binary partially-miscible liquid. A pressure value and a mass fraction of the a polymer in the mixture were the experimental parameters. The characteristic heating time was from 5 to 15 ms. The object of the research was the water/polypropylene glycol-425 (PPG-425) mixture having lower critical solution temperature (LCST). The position of the diffusion spinodal was estimated based on the obtained data on the liquid-liquid binodal in the framework of the Flory-Huggins approximation. An experimental technique to estimate the position of the spinodal of two-component mixtures with LCST on the scale of the mixture component ratio was developed. It was shown that the method of isobaric pulse heating can be used for this purpose. This representation is based on the threshold change in the heat transfer pattern when crossing the phase coexistence curve and the diffusion spinodal.

LBM study of ice nucleation induced by the collapse of cavitation bubbles

In this study, we extended the conventional lattice Boltzmann method (LBM) to numerically examine ice nucleation induced by the collapse of a cavitation bubble. Specifically, a pseudo-potential multi-relaxation-time lattice Boltzmann method (MRT-LBM) coupled with a thermal LBM and a criterion for pressure-dependent ice nucleation onset was developed to investigate the cavitation bubble dynamics including growth and collapse, and the subsequently induced ice nucleation. Using the present model, the water vapour-liquid coexistence curve was extended to temperatures lower than 42% of its critical point, excellently matching the Maxwell construction curve. Two practical application scenarios of ice nucleation were investigated: I, near a solid boundary and II, within a pressurised space. Effects of key system parameters including the stand-off distance (λ), differential pressure (Δp) and initial bubble size (R0) on the maximum collapse pressure (pmax) were examined. The results show that under the same conditions, a much higher pmax is generated in scenario II than that in scenario I, thus more readily initialises ice nucleation. After initialisation, part of the initially formed ice melts when the local temperature exceeds the ice melting temperature due to the rapid dissipation of pressure wave. To ensure the complete freezing of water, a large initial supercooling is required for scenario II.

The role of the second virial coefficient in the vapor-liquid phase coexistence of anisotropic square-well particles

We examine the role of the second virial coefficient in the vapor-liquid (VL) phase coexistence of anisotropic hard bodies with square-well attractions of variable range. According to the extended law of corresponding states, the parameters of hard body interactions and attractions can be built into the reduced density and the reduced second virial coefficients, respectively, which gives rise to the collapse of all VL binodals in the reduced second virial coefficient vs. reduced density plane. The second virial perturbation theory shows that the shape dependence appears as an extra parameter in the phase behavior of anisotropic particles, which does not make possible the perfect collapse of the VL binodals for varying shapes. Interestingly, the binodal curves go closely together and even cross each other in the liquid side allowing to define a quasi-master curve. The existence of an almost perfect master curve is confirmed by replica-exchange Monte Carlo simulations for oblate square-well ellipsoids with several shape anisotropies.

MD simulation estimation of saturation pressure and vapor-liquid equilibrium for binary blends of HFO-1234yf and HFO-1123

Saturation pressure and vapor-liquid equilibrium data of low GWP hydrofluoroolefin compound HFO-1234yf (2,3,3,3-tetrafluoropropene) and its binary blends with HFO-1123 (1,1,2-trifluoroethene) were estimated using molecular dynamics (MD) simulation with the aid of COMPASS force field from 214.15 K to 330.15 K. The maximum absolute deviations of present saturated vapor pressure data from published experimental results were 0.03% for HFO-1123 system and 0.017% for HFO-1234yf system. These models were used to estimate the saturated vapor pressure for six different mixtures of HFO-1234yf and HFO-1123. The saturated liquid and vapor densities, the vapor-liquid coexistence curve (VLCC), and the critical points of the blended refrigerants with various molecular mass fractions were predicted using MD simulations and Gibbs ensemble Monte Carlo (GEMC) simulations. The critical points of HFO-1234yf and HFO-1123 matched well with published data.

Liquid-liquid equilibrium data for ternary mixtures (water + isopropanol + 1-pentanol/1-hexanol/1-heptanol) at 298.15 K: Measurement, correlation and prediction

To recover isopropanol from its aqueous solution, alkanols (1-pentanol, 1-hexanol and 1-heptanol) were selected as the solvents to separate water and isopropanol. Liquid-liquid equilibrium data for water + isopropanol + 1-pentanol/1-hexanol/1-heptanol ternary systems were measured at 298.15 K under 101.3 kPa. The mass conservation of the experimental data was checked, and the reliability of the tie-lie data were evaluated by the Bachman, Hand and Othmer-Tobias equations. The extraction performance of the three solvents was assessed through the separation factor and partition coefficient, and compared with those for other reported solvents {esters, ketones, ethers, alkanes (or alkenes), ionic liquids and deep eutectic solvents}, indicating that 1-heptanol has better extraction performance for isopropanol compared with other two solvents. The NRTL and UNIQUAC models were used to correlate the data to obtain regression parameters. The mixed surface analysis based on Gibbs energy topology verified that the binary interaction parameters are consistent with the measured data. Furthermore, the LLE binodal curve for the researched ternary systems were predicted through the UNIFAC and COSMO-UNIFAC models.

Thermodynamic analysis of polymeric membrane formation by non-solvent induced phase separation in the presence of different nanoparticles

Thermodynamic phase diagrams are powerful tools for predicting the thermodynamic behavior and finally, the morphology of phase inversion membranes. Addition of nanoparticles into a polymeric membrane forming system significantly affects the system phase diagram. Using a lattice-based thermodynamic model, we study the phase diagram of polymeric membrane formation by non-solvent induced phase separation (NIPS) in the presence of three types of nanoparticles (spherical, rod-like or sheet-like). The concept of “nanoparticle-out effect” is introduced to justify the influence of nanoparticles on the binodal curves of the systems. Due to this effect, nanoparticles attract the solvent molecules and reduce the polymer solubility, thereby increasing the thermodynamic instability of the system and moving the binodal curves toward the polymer–solvent axis. This effect is found to be more pronounced for nanorods and nanosheets than for nanospheres. The effect is intensified with increasing the nanoparticles size faster for anisotropic nanosheet and nanorod than for isotropic nanospheres, which results from their different surface fraction values. The system thermodynamic instability gradually rises with decreasing the binary interaction parameters between nanorods or nanosheets and other components while it is nearly unchanged by varying the interaction parameters for nanospheres, which is consistent with their smaller surface fraction value. The accuracy of the phase diagram predictions is demonstrated by comparison with published experimental data on related systems. This thermodynamic description along with the governing kinetic features of membrane forming systems containing nanoparticles could be applied for fabricating polymeric membranes with the desired morphology and function.

Simulation of Binodal and Spinodal Curves of Phase State Diagrams for Binary Polymer Systems.

A new approach is proposed for simulating binodal and spinodal curves of phase diagrams for binary polymer systems. It is shown that the Flory–Huggins theory makes it possible to predict phase behavior in a wide range of temperatures and concentrations based on limited data on the components’ solubility. The approbation data of the technique are presented in the example of PS–PB and PS–PMMA systems, for which generalized phase diagrams are constructed.

Preparation of highly selective PSf/ZnO/PEG400 tight ultrafiltration membrane for dyes removal

AbstractTight ultrafiltration (UF) has increasingly been developed to overcome the low selectivity of conventional UF membranes towards soluble contaminants. In this work, a tight structure of polysulfone‐based (PSf) UF membrane was prepared by blending PSf with polyethylene glycol (PEG400), ZnO nanoparticle (ZnO‐Np), and acetone (Ac) in dimethylacetamide (DMAc). The influences of Ac/DMAc ratio (1: 15 to 1:25) and PEG400 concentration (0–25 wt%) on the binodal curve of the polymer solution, characteristics, and performances of the UF membrane were studied. The membrane performances were investigated by observing the permeate flux and dye rejection during real textile wastewater treatment. The binodal curves are close to the polymer line, which means that rapid demixing occurred after the casted solution was immersed in the coagulation bath. Based on FTIR analysis, PEG400 and ZnO‐Np were partially entrapped in the UF membrane structure. Over 90% of color removal at a permeate flux of 72 L.m−2.h−1 could be achieved when the Ac/DMAC ratio was 1:12. The tight‐UF membrane removed TDS and Naphthol AS by 74.5% and 92.8%, respectively. Since the experimental result showed a high contaminants removal, the tight‐UF could be used as clean technology to produce clean water for water reuse purposes at low energy requirements.

Microfluidics approach for determination of the equilibrium phase composition in multicomponent biphasic liquid systems

Based on the fundamentals of microfluidics, a novel approach for the determination of liquid-liquid equilibria (LLE) of ternary systems was proposed. The system studied here consists of the compounds water, acetone, and toluene. This method was realized in a microfluidic set-up that consists of a microchannel, a camera for the determination of the position of the phase interface, and a micro density meter for measuring the densities of the conjugated phases at the outlet of the microchip. To determine the equilibrium phase compositions, an optimization problem was defined that minimized the difference between the experimentally determined and calculated ratio of the volumetric flow rates of the conjugated phases. The developed procedure uses information on the position of the phase interface in the microchannel and the phase densities, and requires previous knowledge of the binodal curve, which as shown in our previous work (Hübner and Minceva, 2019) can be also determined using the same set-up. The obtained equilibrium phase compositions were in good agreement with literature data. Eventually, once the procedure is automatized to reduce the required measuring time and achieve full user independency, the proposed approach poses a cheap and fast alternative to conventional methods for measuring LLE.

Prediction and programming of microemulsion phase behavior simulation

In the process of microemulsion flooding, microemulsion phase state may be affected by the adsorption of core and the distribution of oil and water, and the upper phase, the middle phase or the lower phase microemulsion will appear. Accurate description of microemulsion phase state and quantitative discrimination of equilibrium phase composition are of great theoretical value and research significance for the design of microemulsion flooding system and improving the recovery efficiency of microemulsion. Therefore, in this paper, microemulsion phase model is deeply studied. Aiming at the difficulty of solving the existing Hand model and the unknown parameters of the improved HLD-NAC model, we introduce the binodal curve range parameter D and the asymmetric migration degree parameter B, and establish a new phase behavior description method of the binodal curve, the two-phase plait point lines and the III-phase node line. Then the phase discrimination programming of microemulsion was carried out, and the change laws of phase number, phase type and mass fraction of equilibrium phases of any microemulsion system under different salinity were revealed. The results show that the simulation results of microemulsions accord with the salinity scanning law, and can accurately identify the complex microemulsion phase states.

Rhyolite-perlite transition zone in the acid volcanoes of the Eastern Rhodopes Paleogene volcanic area (SE Bulgaria)

In the siliceous volcanoes, the transition between rhyolites and perlite is carried out through a zone with the following morphology: i) rhyolite balls (spheruloids with spherulitic or felsitic texture) among the perlites; ii) alternation of subparallel perlite and rhyolite bands with felsitic texture; iii) a combination of the above two morphologies – rhyolite bands with spheruloids adhering to them; iv) alternation of finger-like wedge-shaped perlite and rhyolite wedges. The rhyolite spheruloids have Na composition (they are composed of tridymite and Na-K feldspar), while the perlites including them, as well as all rhyolites in the Eastern Rhodopes, are potassic. This chemistry, as well as many morphological features, show their immiscibility origin, which has been recently proven also experimentally (Kotel’nikov et al., 2016, 2019). Complex spheruloids are also observed, which consist of two types of spheruloids with different distribu¬tion of alkalis in them: small, in which Na>K and large spheruloids, which include small ones and in which potassium predominates. It is assumed that they are a product of a two-step immiscibility – in the first step large drops and matrix are formed, and in the second the large drops decompose into small drops (enriched with Na) and a new matrix (enriched with potassium), which is the building element of the large drops. The drops crystallize as spherulites, while the matrix solidifies as perlite. The spheruloids are products of nucleation and growth mechanism, i.e. they are formed in the fields between the binodal and spinodal curves. The other type of transition – the alternation of perlite and rhyolite bands is assumed to be formed by the spinodal decomposition, i.e. in the field limited by the spinodal curves.

Triple points and novel phase transitions of dyonic AdS black holes with quasitopological electromagnetism

Quasitopological electromagnetism has an important influence on the strong gravity of dyonic black holes. For example, three photon spheres, with one being stable, are found, and we wish to test them with the observed black hole shadow. We are primarily concerned with the thermodynamics and phase transition for a dyonic anti--de Sitter (AdS) black hole when quasitopological electromagnetism is included. Unlike in a black hole solution without quasitopological electromagnetism, we observe a triple point phase structure by varying the coupling parameters. Of particular interest, for certain parameter values, two separate coexistence curves are present, which is an additional novel phase structure that is absent in a black hole solution without quasitopological electromagnetism. The critical exponents share the same values as mean field theory. These results uncover the intriguing properties of dyonic AdS black holes with quasitopological electromagnetism from a thermodynamic point of view.

Simultaneously measurements of vapor-pressure, saturated liquid density, single-phase PVT properties, and thermal -pressure coefficient of methyl decanoate at high- temperatures and high-pressures

The vapor-pressure (PS), saturated liquid density (ρS), single-phase (PVT) properties, and thermal-pressure coefficient, γV=(∂P/∂T)V, of one of the biofuel components (methyl decanoate) have been measured in the present work. The measurements were made over a temperature range from (292 to 464) K and at pressures up to 21 MPa. The measurements were performed using a high-temperature, high-pressure, nearly constant-volume adiabatic piezo-calorimeter along 16 liquid and vapor isochores between (152 and 834) kg·m − 3. Most measurements were focused in the immediate vicinity of the liquid-gas coexistence curve (single- and two-phase regions) to accurately determine the phase transition properties (PS,ρS, TS,γVS). Temperatures at the liquid-gas phase transition curve, TS(ρ), for each measured density (isochore) were determined using the isochoric P-T break- point and abrupt behavior of the thermal-pressure coefficient techniques, γV−T curve behavior. The expanded uncertainty of the pressure (P), density (ρ), and thermal –pressure coefficient (γV) measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be (0.05 to 0.50)% (depending on pressure range), 0.16%, and (0.12 to 1.5)% (depending on temperature and pressure), respectively. The measured pressures and temperature derivatives,(∂P/∂T)V, have been used to calculate internal pressure (or energy-volume coefficient), enthalpy and entropy of vaporization, and heat capacity changes.

Temperature Effect on the Phase Equilibrium of Polyethylene Glycol 2000 + Trilithium Citrate + Water Aqueous Two-Phase Systems at T = 288.15, 298.15, 308.15, and 318.15 K

Binodal and tie-line mass fractions for ternary polyethylene glycol 2000 + trilithium citrate + water aqueous two-phase systems (ATPSs) were reported at T = 288.15, 298.15, 308.15, and 318.15 K experimentally and modeled thermodynamically. It was found that the extent of the two-phase area of the liquid–liquid equilibrium region was increased as the temperature increased. Also, binodal curves were properly modeled with two nonlinear models, and both models have been successful in fitting the binodal data. Furthermore, the osmotic virial, modified nonrandom two-liquid (m-NRTL), and electrolyte-Wilson models have successfully been implemented in the modeling of the tie-line mass fractions. The quality of fitting with the electrolyte-Wilson and specially m-NRTL models is good, and the uncertainty of the modeled data is in the range of the uncertainty of the experimental data. Also, the salting-out coefficient (ks) of a Setschenow-type equation was applied as a quantitative measure of the salting-out ability. The results of the present work introduce a green and environmentally friendly ATPS for liquid–liquid extraction and purification purposes, which can be used in the separation and purification of drugs, biomaterials, and foods.

On the force scheme influence on pseudopotential method coexistence curve

Pseudopotential method has been drawing attention in simulating multiphase flows by adding an interparticle force to lattice Boltzmann method (LBM). However, implementing a known force field effect into evolution of particle distribution function is still an active field of interest, specially when higher order terms play significant role in resulting macroscopic equations. A considerable number of forcing schemes has already been proposed, and although many have shown their differences up to second order analysis, there is still some debate about high order terms. In this work, a study taking into account third order forcing terms is carried out, in order to better identify the reasons for existing distinct coexistence curves when the same interparticle force is employed through distinct forcing schemes. Third order terms related to spatial interparticle force gradients are taken into account, and a theoretical analysis is carried out in order to study gas–liquid coexistence curves. It is shown that this curve can be characterized by a single parameter, Γ, dependent on employed relaxation time and forcing scheme, which allows the current analysis to be used for other schemes as well. Flat interface simulations are carried out in order to study the behavior of gas–liquid coexistence curve. A good agreement between the numerical and theoretical results validates the presented approach. Static droplet simulations were carried out, where surface tension behavior also respect the expected trend of higher values for lower Γ. Maximum spurious velocities of renowned forcing schemes from literature were also studied, without a clear correlation with Γ parameter.

Kinetics of a phase transition for a Kerr-AdS black hole on the free-energy landscape

By treating the order parameter as a stochastic thermal fluctuating variable for small-large black hole phase transition, we investigate the kinetic process of phase transition for the Kerr-AdS (anti--de Sitter) black holes on free energy landscape. We find that the extremal points of the off shell Gibbs free energy correspond to physical black holes. For small-large black hole phase transition, the off shell Gibbs free energy exhibits a double well behavior with the same depth. Contrary to previous research for the kinetics of phase transition for the Kerr-Newman-AdS family black holes on a free energy landscape, we find that there is a lower bound for the order parameter and the lower bound corresponds to extremal black holes. In particular, the off shell Gibbs free energy is zero instead of divergent as previous work suggested for vanishing black hole horizon radius, which corresponds to the Gibbs free energy of a thermal AdS space. The investigation for the evolution of the probability distribution for the phase transition indicates that the initial stable small (large) black hole tends to switch to stable large (small) black hole. Increasing the temperature along the coexistence curve, the switching process becomes faster and the probability distribution reaches the final stationary Boltzmann distribution at a shorter time. The distribution of the first passage time indicates the time scale of the small-large black hole phase transition, and the peak of the distribution becomes sharper and shifts to the left with the increase of temperature along the coexistence curve. This suggests that a considerable first passage process occurs at a shorter time for higher temperature. The investigation of the kinetics of phase transition might provide us new insight into the underlying microscopic interactions.