Solute Distribution Coefficient Research Articles

Microstructure forming mechanism of inconel 625 alloy fabricated by laser/ultra-high (UHF) induction hybrid deposition method

To reveal the microstructure forming mechanism of laser/ultra-high frequency (UHF) induction deposition, this paper developed a microscopic phase-field (PF) model to numerically investigate dendrite growth during solidification. The macroscopic model of molten pool evolution is adopted to provide the solidification conditions for the microscopic PF model. The dendrite growth during laser deposition is simulated to evaluate the effect of UHF induction heat on the dendrite growth. Results show that because of the high temperature gradient and cooling rate, the PDAS of laser-UHF induction hybrid deposited layer is less than that of the laser deposited layer. The UHF induction heat also leads to a high flow velocity of the molten metal during laser-UHF induction hybrid deposition. The high flow velocity contributes to the decrease in PDAS by inhibiting the interdendritic enrichment of solute. During laser-UHF induction hybrid deposition, a higher solute gradient is present in the tip region of dendrite arm, leading to a faster dendrite growth rate. The UHF induction heat also increases the solute distribution coefficient during deposition, which further inhibits the element segregation. Under the action of UHF induction heat, a low interdendritic solute gradient and an evenly distributed solute can be obtained, thus helping increase interdendritic undercooling degrees and decreasing the PDAS. The simulated PDAS and solute distribution have good consistency with the experimental results. The spectral analysis of EDS line detection indicates that the laser-UHF induction hybrid deposited layer has a more refined microstructure and weaker element segregation than the laser deposited layer does.

The extraction of biofuel components from aqueous solution into various solvents using liquid-liquid extraction (LLE)

In this study, various solvents were evaluated for their efficacy in extracting biofuel components, such as acetone (ACT), n-butanol (nBuOH), ethanol (EtOH), and isobutanol (IBA) from aqueous solution at 37.5 °C and atmospheric pressure using liquid-liquid extraction (LLE). The extraction performance of solvents was evaluated by their solute distribution coefficients and selectivity. The experimental results are compared with theoretical prediction using ASPEN plus and the model shows an excellent fit. Among the solvents examined, 2,6-dimethyl-4-heptanol (DMHT) and 2-ethyl-1-hexanol (2E1H) are more effective solvents for the extraction of IBA and nBuOH from aqueous solution.

A green hydrophobic deep eutectic solvent for extraction of phenol from aqueous phase

Deep eutectic solvents (DESs), have been recognized as effective materials for the extraction of different compounds. In this study, the performance of a novel hydrophobic DES was evaluated for the extraction of phenol from aqueous solutions. Octanoic and dodecanoic fatty acid precursors with a definite molar ratio of 3:1, respectively, were used for the DES having a low melting point of 8.3 °C. The purity and stability of the product were confirmed via characterizing by FTIR, 1H and 13C NMR methods. The liquid–liquid equilibrium of the water + phenol + DES ternary system at different temperatures of 293.2, 298.2 and 308.2 K was accordingly studied through cloud point titration method and refractive index measurement. Interestingly, the important parameters of the solute distribution coefficient and the separation factor were, respectively, within the high levels of (6.8321–9.7787) and (895.76–2770.17), indicating the amazing capability of the DES. Reasonably, both of these parameters decreased with temperature. The NRTL and UNIQUAC thermodynamic models were employed to reproduce the obtained tie-lines and to determine the interaction parameters at each temperature. The low level root mean square deviations for the mentioned models were, respectively, within (0.0014–0.0027) and (0.0045–0.0063); confirming satisfactorily agreement with the experimental data.

On the molecular-based thermodynamics of dilute solutions along orthobaric conditions: Concise review of the fundamental microscopic constraints, rigorous formal results, and macroscopic modeling implications

We review the fundamentals underlying a rigorous and general molecular-based formalism for the microscopic interpretation of the solvation phenomena involving dilute solutes along the vapor–liquid envelope of a pure solvent up to its critical point. This approach bridges the path between the microstructure of the system, described in terms of correlation function integrals, and the macroscopic solvation properties resulting from the solute–solvent intermolecular interaction asymmetries. We focus on the solvation phenomena associated with the behavior of the Henry’s law constant, vapor–liquid solute distribution coefficient, and the corresponding Ostwald constant whose proper description in the compressible regime of a solvent becomes crucial to the determination of the solute’s Krichevskii parameter. Toward that end, we aim at the widespread use of linear orthobaric-density representations for the behavior of the thermodynamic quantities of infinitely dilute species in near-critical pure solvents. Then, we (i) confront their behavior against that from model systems for which we have full and accurate knowledge of the outcome, such as those for the solvation of an ideal gas solute in a real solvent, and that of a self-solvated species representing thermodynamically the Lewis-Randall solution ideality, (ii) identify the non-monotonic orthobaric-density slope of the vapor–liquid solute distribution coefficient involving the ideal gas solute in either light- or heavy-aqueous solutions, a condition that disallows the central hypothesis underpinning the conventional linear regression approach and the accuracy of the defining Krichevskii parameters, (iii) present a novel path leading to the calculation of the Krichevskii parameter of any solute according to a universal thermodynamic expression connecting rigorously the solute–solvent intermolecular asymmetry, as described by the Henry’s law constant of a solute at infinite dilution in a pure solvent, to the desired Krichevskii parameter, and (iv) establish a direct route leading to the accurate determination of the solvent effect on the Krichevskii parameter of a solute, based solely on the contrasting standard solvation Gibbs free energies of the solute at normal conditions and the corresponding Krichevskii parameters of an ideal gas solute in the desired pair of solvents. Finally, we discuss the assessment of the reliability of current modeling approximations, their internal consistency, and the conformity of limiting behaviors as fundamental constraints in the accurate description of solvation phenomena involving infinitely dilute solutions over wide ranges of state conditions and solute–solvent intermolecular interaction asymmetries.

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.

Investigation of dendrite growth, Nb segregation during laser IN718 deposition via volume of fluid-phase field modeling

In this work, a macro-micro VOF-PF (Volume of Fluid-Phase field) model is established to simulate the heat transfer, dendrite growth and Nb segregation during the laser IN718 deposition. According to calculated heat transfers, G increases, while Vp decreases, and the corresponding G×Vp decreases from top to bottom in the molten pool. The calculated the primary dendrite arm spacing (PDAS) using the PF model increases from top to bottom. Compared with other models, the calculated PDAS using the PF model considering the liquid-metal flow is closest to experiment measurements. During the dendrite growth, Nb is enriched in the interdendritic region, and finally is distributed in the droplet shape. The calculated actual solute distribution coefficient Cmin/Cmax decreases from 0.584 to 5.548 with the decrease of G×Vp, which follows the equilibrium solidification theory. According to dc/dy=G/ml, the liquidus slope ml is calculated as 0.05322wt.%/μm very close to the theoretical value 0.05394wt.%/μm. The simulated Nb concentrations in the matrix γ and Laves phases are 3.97wt.%, 13.3wt.% respectively, which are in good agreements with experimental 3.7wt.% and 13wt.%.

Distribution of florfenicol and norfloxacin in ice during water freezing process: Dual effects by fluorine substituents

Distribution in ice is regarded as one of important transport modes for pollutants in seasonal freeze-up waters in cold regions. However, the distribution characteristics and mechanisms of fluorinated antibiotics as emerging contaminants during the water freezing process remain unclear. Here, florfenicol and norfloxacin were selected as model fluorinated antibiotics to investigate their ice-water distribution. Effects of antibiotic molecular structure on the distribution were explored through comparative studies with their non-fluorinated structural analogs. Results showed that phase changes during the ice growth process redistributed the antibiotics, with antibiotic concentrations in water 3.0–6.4 times higher than those in ice. The solute-rich boundary layer with a concentration gradient was presented at the ice-water interface and controlled by constitutional supercooling during the freezing process. The ice-water distribution coefficient (KIW) values of antibiotics increased by 34.8%–38.0% with a doubling of the cooling area. The solute distribution coefficient (Kbs) values of antibiotics at −20 °C were 65.6%–70.3% higher than at −10 °C. The KIW and Kbs values of all antibiotics were negatively correlated with their water solubilities. The fluorine substituents influenced the binding energies between antibiotics and ice, resulting in a 1.1-fold increase in the binding energy of norfloxacin on the ice surface relative to its structural analog pipemidic acid. The results provide a new insight into the transport behaviors of fluorinated pharmaceuticals in ice-water systems.

A method of removal of nickel impurity from electrolytic magnesium

The Ni impurity existing in electrolytic Mg cannot be removed using the common settling method since there is a deep eutectic reaction between Ni and Mg. Thermodynamic calculations in this work indicate that the equilibrium solute distribution coefficients of Ni between solid and liquid Mg above the eutectic temperature are far less than 1. The directional solidification method was firstly employed in this work to remove the Ni impurity from the electrolytic Mg. The results show that the Ni impurity in the electrolytic Mg can be almost completely removed (<5 ppm) after the directional solidification process, which meets the requirement of high-purity Mg for Ni content tolerance and is therefore promising for the production of high-purity Mg.

Solute redistribution and mechanism of structure refinement of Mg-Al alloy during solidification under high pressure

The effect of high pressure on the composition and grain size of the Mg- x Al alloy was studied, and the mechanism of structure refinement from the viewpoint of solute redistribution was discussed. The results show that the amount of Al in the solid solution in the α-Mg matrix increased due to the higher solute distribution coefficient caused by high pressure. The Al content of the original alloy required for the initial eutectic transformation was increased from 5 wt% at atmospheric pressure to 9 wt% at 4 GPa, and the Al content at the eutectic point increased from 32.3 wt% at atmospheric pressure to 38.3 wt% at 4 GPa. Under high pressure, the large increase in the number of α-Mg crystals is related not only to the increase in nucleation rate and the inhibition of crystal growth caused by high pressure but also to the higher Al content, which enhances constitutional supercooling, further increasing the nucleation rate and inhibiting crystal growth. • Minimum Al content for eutectic transition at different pressures was found. • It is found that the eutectic structure is ultrafine fibrous under GPa pressure. • The Al solute content plays an important role in grain refinement of Mg-Al alloy.

Experimental study and thermodynamic modeling of phase equilibria of systems containing cyclohexane, alcohols (C4 and C5), and deep eutectic solvents

Liquid-liquid equilibrium (LLE) data were measured and comparatively analyzed for six ternary mixtures of (cyclohexane + alcohols + deep eutectic solvents) at T = 298.2 K and p = 101 kPa. In this work, three choline chloride-based deep eutectic solvents (ChCl-DESs) were prepared for the extraction of the two structurally similar primary alcohols (1-butanol and 3-methyl-1-butanol) from a hydrocarbon (cyclohexane). The chosen DESs were DES1 (ChCl-propylene glycol with molar ratio = 1:3), DES2 (ChCl-ethylene glycol with molar ratio = 1:2), and DES3 (ChCl-glycerol with molar ratio = 1:2). The quality of the tie-line compositions was checked using the Othmer-Tobias correlation equation. The NRTL model was successfully applied to fit the experimental equilibrium data. The model binary interaction parameters were optimized by the Particle Swarm Optimization (PSO) algorithm. The model validation confirms that all the calculated parameters are consistent with the experimental data. Evaluation of the capacities of the deep eutectic solvent was carried out via the calculation of solute distribution coefficients and selectivity from the LLE data. The influence of the chemical structure of the alcohol on the phase equilibria was investigated. The extraction ability of the studied deep eutectic solvents displays promising results. The highest solute distribution coefficients were determined for (cyclohexane + 1-butanol + DES1).

Porous hydrophobic-hydrophilic Janus membranes for nondispersive membrane solvent extraction

Porous membranes having a particular wetting characteristic, hydrophobic or hydrophilic, are used for nondispersive membrane solvent extraction (MSX) where two immiscible phases flow on two sides of the membrane. The aqueous-organic phase interface across which solvent extraction/back extraction occurs remains immobilized on one surface of the membrane. This process requires the pressure of the phase not present in membrane pores to be either equal to or higher than that of the phase present in membrane pores; the excess phase pressure should not exceed a breakthrough pressure. In countercurrent MSX with significant flow pressure drop in each phase, this often poses a problem. To overcome this problem, flat porous Janus membranes were developed using either a base polypropylene (PP) or polyvinylidene fluoride (PVDF) or polyamide (Nylon) membrane, one side of which is hydrophobic and the other being hydrophilic. Such membranes were characterized using the contact angle, liquid entry pressure (LEP) and the droplet breakthrough pressure from each side of the membrane along with characterizations via scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). Nondispersive solvent extractions were carried out successfully for two systems, octanol-phenol (solute)-water, toluene-acetone (solute)-water, with either flowing phase at a pressure higher than that of the other phase. The phenol extraction system had a high solute distribution coefficient whereas acetone prefers both phases almost identically. The potential practical utility of the MSX technique will be substantially enhanced via Janus MSX membranes.

Titrimetric Study of Solubility of Solute Benzoic Acid and Their Partition in Water and Benzene Solvents

The solubility and distribution coefficient (K) of solute in solvent is depends on temperature and solute-solvent interaction, where the solute is partitioned between two immiscible solvents phase and dissociated into ionic form. Here, we have reported the titrimetric study for solubility and partition or distribution coefficient of benzoic acid (solute) in aqueous water and in organic benzene which are using as solvents. The benzoic acid solubility (in g/100g of solvent) in water and in benzene solutions have determined by titrimetrically. There is partitioning and concentration of such acid in these solvent phase by shake-flask and acid-base titration method as well. The benzoic acid solubility and their distribution between water and benzene as in different pH buffer solutions have been analyzed at room temperature (25°C) in acidic, neutral and basic (pH 4.0, 7.0 and 9.0) medium, respectively.

Macrosegregation and channel segregation formation of faceted mushy zone in solidification of Sn–Ni hypereutectic alloy in a temperature gradient

Numerous investigations on the macrosegregation and channel segregation formation have been reported during eutectic solidification. However, the current analyses are focused on the non-faceted dendritic mushy zone while the faceted mushy zone during solidification has not been reported before. In this work, the macrosegretion and channel segregation formation are studied in directional solidification of Sn-15at.%Ni hypereutectic alloy where the solidified Ni3Sn4 phase exhibits faceted lath-type growth morphology. Similar to previous works on non-faceted mushy zone, more channels can be witnessed in the (Liquid + Ni3Sn4) mushy zone at lower growth velocities. More obvious macrosegregation can be formed in samples at lower growth velocities where the thermosolutal convection is more severe. However, distinct from previous reports, the effective solute distribution coefficient is not constant in the faceted mushy zone of this alloy. Besides, the experimental results demonstrates that the convection can reduce the interspacing of Ni3Sn4 phase during directional solidification. In addition, the thermosolutal convection has more significant influence on the interspacing of Ni3Sn4 phase than the solutal buildup at the tip of Ni3Sn4 phase.

Selective separation of α-tocopherol using eco-friendly choline chloride – Based deep eutectic solvents (DESs) via liquid-liquid extraction

In this work, the extraction of α-tocopherol was studied using some recently introduced novel, simple and green deep eutectic solvents (DESs). Liquid – liquid extraction measurements were conducted on ternary mixtures of {n-hexane + (α-, β-, γ-, δ-) tocopherol + DESs}. The recently studied DESs including (mono-, di- and tri-) ethylene glycol, (mono-, di- and tri-) ethanolamine, and sucrose in combination with ChCl for the first time were used for this extraction. The various parameters affected on extraction efficiency including kind of DESs, temperature (298.15–308.15 K) and extraction time (12, 24 and 48 h) were evaluated. The calculated selectivity (S) and solute distribution coefficient (β) showed good performance of the selected DESs for α-tocopherol. The non-random liquid equation (NTRL) was utilized to correlate measured experimental LLE results, prediction of activity coefficient at infinite dilution (γ∞) and capacity of solvent for solute (C∞). Moreover, higher selectivity, lower contamination of extracted α-tocopherol (with solvents) and immiscibility of eutectic solvents in vitamin E were other advantages of this extraction.

Effects of local nonequilibrium in rapid eutectic solidification—Part 2: Analysis of effects and comparison to experiment

The developed model of diffusion‐limited and diffusionless solidification of a eutectic alloy describes the relation “undercooling (ΔT)‐velocity (V)‐interlamellar spacing (λ)” for two cases. Namely, when the solidification front velocity V is smaller than the solute diffusion speed in bulk liquid VD, V &lt; VD, the model predicts a regime of eutectic solidification similarly to known classical models. If the solidification front velocity V is higher than the diffusion speed, V &gt; VD, the solidification is mainly controlled by kinetic and thermal undercoolings. New expressions for the solute distribution coefficient and slope of the liquidus lines are supplied. The influence of the model parameters on the growth kinetics during eutectic solidification is discussed. Model predictions are compared with experimental data for the solidification of an Fe–B alloy with eutectic composition. Computational results show that the model agrees well with experimental data especially for low and high undercoolings, extending the undercooling range that can be covered by sharp interface modeling.

ASPEN plus simulation of liquid\u2013liquid equilibria data for the extraction of aromatics from waste tyre pyrolysis gasoline using organic and deep eutectic solvents: a comparative study

Waste tyre pyrolysis gasoline (WTPG) contain significant amount of aromatics such as benzene, toluene and xylenes (BTX) and thus provide a good source for these value-added chemicals. Separation of aromatics from aliphatic media as obtained in WTPG and naphtha is done commercially by solvent extraction using volatile organic solvents such as sulfolane (SUF), dimethylformamide (DMF) and diethylene glycol (DEG). The high cost of this state-of-the art separation method and environmental consideration have necessitated search for non-volatile and green solvent such as deep eutectic solvent (DES). This study intends to conduct a comparative evaluation of the performance of five solvents (SUF, DMF, DEG, and two DESs) for the extraction of BTX from WTPG. The two DESs are choline chloride/ethylene glycol (DES1) and choline chloride/glycerol (DES2) in molar ratios 1:2. An ASPEN plus simulation was carried out to generate liquid–liquid equilibria (LLE) data for the pseudo-ternary systems {WTPG + BTX + solvent (SUF/DMF/DEG/DES)}. Performance evaluation was based on selectivity (S) and solute (BTX) distribution coefficient (D). The propriety of the simulation protocol was validated using literature data. The results revealed the following maximum values of selectivity and distribution coefficients for the solvents: DES2 (S = 378.283, D = 0.656); DES1 (S = 77.364, D = 1.423); SUF (S = 55.371, D = 0.756); DMF (S = 25.336, D = 0.786) and DEG (S = 17.531, D = 0.793). The DESs therefore performed better than the organic solvents and can suitably replace same in the extraction of BTX from waste tyre pyrolysis gasoline.

Entropic-Based Separation of Diastereomers: Size-Exclusion Chromatography with Online Viscometry and Refractometry Detection for Analysis of Blends of Mannose and Galactose Methyl-\u03b1-pyranosides at \u201cIdeal\u201d Size-Exclusion Conditions

The separation of carbohydrate diastereomers by an ideal size-exclusion mechanism, i.e., in the absence of enthalpic contributions to the separation, can be considered one of the grand challenges in chromatography: Can a difference in the location of a single axial hydroxy group on a pyranose ring (e.g., the axial OH being located on carbon 2 versus on carbon 4 of the ring) sufficiently affect the solution conformational entropy of a monosaccharide in a manner which allows for members of a diastereomeric pair to be separated from each other by size-exclusion chromatography (SEC)? Previous attempts at answering this question, for aqueous solutions, have been thwarted by the mutarotation of sugars in water. Here, the matter is addressed by employing the non-mutarotating methyl-α-pyranosides of d-mannose and d-galactose. We show for the first time, using SEC columns, the entropically driven separation of members of this diastereomeric pair, at a resolution of 1.2–1.3 and with only a 0.4–1% change in solute distribution coefficient over a 25 °C range, thereby demonstrating the ideality of the separation. It is also shown how the newest generation of online viscometer allows for improved sensitivity, thereby extending the range of this so-called molar-mass-sensitive detector into the monomeric regime. Detector multidimensionality is showcased via the synergism of online viscometry and refractometry, which combine to measure the intrinsic viscosity and viscometric radius of the sugars continually across the elution profiles of each diastereomer, methyl-α-d-mannopyranoside and methyl-α-d-galactopyranoside.

Rationalizing Al-Mg, Al-Mg-Si, and multicomponent aluminum alloy design with segregation susceptibility predictions

Macro-segregation is a type of unacceptable defects, which normally occurs for aluminum alloys and other nonferrous alloys. In this work, the macro-segregation susceptibility (MAS) of commercial 5xxx and 6xxx alloys and Al-Mg and Al-Mg-Si alloys have been investigated via a criterion based on the solidification curves from thermodynamic calculations. Equilibrium solute distribution coefficients, k, with different initial alloying concentrations and their relationships with the MAS are discussed. Of all commercial 5xxx and 6xxx aluminum alloys, the AA5754, AA5182, AA6181A and AA6016 alloys have shown less susceptible to macro-segregation than others. Of all Al-Mg and Al-Mg-Si alloys in this study, Al-Mg alloys with higher Mg, and Al-Mg-Si alloys with both higher Mg and Si have shown less susceptible to macro-segregation than other compositions. Finally, the role of mass transfer behavior in improving macro-segregation is discussed from the perspective of thermodynamic and kinetic calculations.

Measurement and Thermodynamic Modeling of Ternary (Liquid + Liquid) Equilibrium for Extraction of Phenols from Dodecane with 1,4-Butanediol at 303.15 and 323.15 K

The extraction process as a kind of energy-saving and environmental protection technology can be used to separate the phenols from the low-temperature coal tar. The liquid-liquid equilibrium (LLE) data of ternary systems dodecane + phenols + 1,4-butanediol were determined experimentally at 303.15 and 323.15 K under the 101.3 Kpa condition, where phenols refer to 4-ethylphenol and 2,5-xylenol. The solvent extraction capacity was assessed by the solute distribution coefficient and selectivity. Othmer-Tobias and Bachman equations were utilized to validate the correlation of the measured data, which the linear correlation (R2) ≥ 0.99. Experimental LLE data was correlated utilizing the NRTL and UNIQUAC thermodynamic models with all of the RMSD values below 0.007 meaning that each ternary system satisfactory agreement at temperatures studied.

Measurement and Thermodynamic Modeling of Ternary (Liquid + Liquid) Equilibrium for Extraction of Phenols from Alkane with Furfural

The extraction process as a kind of energy-saving and environmental protection technology can be used to separate phenols from low-temperature coal tar. The liquid–liquid equilibrium (LLE) data regarding ternary systems n-heptane + phenols + furfural were determined experimentally at 303.2, 323.2, and 343.2 K under the atmospheric pressure condition, where phenols refer to phenol, p-cresol, and 2,6-xylenol. The solvent extraction capacity was assessed by the solute distribution coefficient and selectivity. Othmer–Tobias and Bachman equations were utilized to validate the consistency of the measured data, which the linear correlation (R2) ≥ 0.99. Experimental LLE data were correlated utilizing the NRTL and UNIQUAC thermodynamic models with all of the RMSD and AARD values below 0.01, meaning that each ternary system is satisfactorily in agreement at temperatures studied and the NRTL model gives better agreement than the UNIQUAC model for ternary systems.