Abstract: To gain an understanding of the transport and thermodynamic behavior of the highly non-ideal mixture methanol + cyclohexane, three complementary approaches, i.e. experiment, molecular simulation and predictive equations, are employed. The temperature and composition dependence of different diffusion coefficients is studied around the miscibility gap at ambient pressure. On the one hand Fick diffusion coefficients are measured experimentally by interferometric probing and on the other hand Maxwell–Stefan diffusion coefficients and intradiffusion coefficients are sampled by equilibrium molecular dynamics simulation at five temperatures below the upper critical temperature of ∼319 K. The spinodal curve is determined from extrapolation of the experimental Fick diffusion coefficient data and compared to predictions from excess Gibbs energy models. It is found that these models are not capable to correctly describe the activity coefficients over the whole composition range of the studied mixture. Thus, different parameter sets for a modified Wilson model are used for calculations of the thermodynamic factor, which is needed to transform Maxwell–Stefan into Fick diffusion coefficients and vice versa. Further, predictive equations for the Maxwell–Stefan diffusion coefficient, which are based on intradiffusion coefficients, are compared to simulation results. Using different approaches provides a clearer understanding of the relations between kinetic and thermodynamic properties contributing to the diffusion behavior of partially miscible mixtures.

Abstract: The interaction behavior and the process of mixed micellization for binary mixtures of an amino sulfonate amphoteric surfactant sodium 3-(N-dodecyl ethylenediamino)-2-hydropropyl sulfonate (C12AS) and a cationic surfactant octadecyltrimethylammonium bromide (OTAB) in aqueous solution of NaCl (0.250 M) at 313.15 K were investigated using both the tensiometry and the UV–vis spectrometry using pyrene as a probe. The mixed critical micelle concentration (cmc) of the C12AS/OTAB mixtures were determined by two techniques. Based on regular solution theory, pseudophase separation model, Clint’s model, Rosen’s model, and Rubingh’s model, some parameters (including the ideal mixed cmc, the compositions in mixed micelle, the interaction parameters between two surfactants, the activity coefficients in mixed micelle, some thermodynamic parameters, etc.) were evaluated and calculated. The deviation of mixed cmc from its ideal value indicates a nonideal mixing between two surfactants. In comparison with those in aqueous...

Abstract: Coal tar is a byproduct of low temperature coal carbonization. The separation of the compounds has great significance since its main component is the mixture of phenols and hydrocarbons. In this paper, the separation of specific phenolic compounds from model coal tar (phenols + hexane) was studied. The solvent was screened by empirical analysis, the universal quasichemical functional group activity coefficient (UNIFAC), and conductor-like screening model COSMO-SAC (segment activity coefficient). COSMO-SAC was used to calculate the capacity, selectivity, and performance index of solvents. Finally, the monoethanolamine (MEA) was selected as the solvent to extract the phenols. The liquid–liquid equilibrium for the ternary mixture of phenols + hexane + MEA was measured at 303.15 K and 323.15 K under atmospheric pressure, and the results showed that MEA provided a high distribution coefficient, efficiency, and selectivity for phenols. Meanwhile, the extraction process of phenols was simulated based on the nonr...

Abstract: The effect of interactions between organic solvents or water on the interfacial and bulk properties of 1-benzyl-3-methylimidazolium dicyanamide, [BzMIM][DCA] and 1-benzyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [BzMIM][NTf2] were determined via measurement of activity coefficients γ∞13 at infinite dilution for 64 solutes. The data were obtained using the gas–liquid chromatography technique. Measurements were undertaken at six temperatures, in 10 K intervals, in the range of 318.15 to 368.15 K. The solutes studied included both non-polar and polar compounds, such as alkanes, alkenes, and alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters. Density, ρ, and viscosity η, measurements for a range of temperatures, T for the chosen ionic liquids (ILs), [BzMIM][DCA] and [BzMIM][NTf2] were also undertaken at pressure, p = 101 kPa. The gas–liquid partition coefficients, KL at infinite dilution, and the fundamental thermodynamic functions, partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements. The values of selectivity and capacity for three separation cases, viz. hexane/hex-1-ene, cyclohexane/cyclohexene, and ethylbenzene/styrene were calculated from γ∞13 values and compared to literature for imidazolium-based or dicyanamide-based, or bis{(trifluoromethyl)sulfonyl}imide-based ionic liquids (ILs). The results from the study indicate that [BzMIM][DCA] has large selectivity values for all three of the separation cases studied.

Abstract: The isobaric vapor–liquid equilibrium (VLE) data for the systems (thioglycolic acid + water), (thioglycolic acid + butyl acetate), (thioglycolic acid + butyl formate), and (thioglycolic acid + isobutyl acetate) were measured at P = 101.3 kPa by using a vapor recirculating type (modified Rose) equilibrium still. The thermodynamic consistency test of the experimental data for the four binary systems were confirmed by the method of Van Ness. The experimental VLE data were correlated by the three activity coefficient models of Wilson, nonrandom two-liquid (NRTL), and universal quasi-chemical (UNIQUAC). The results show that all the calculated data by the Wilson, NRTL, and UNIQUAC models are in good agreement with the measured VLE data. Meanwhile, the binary interaction parameters of the three models for the binary systems were regressed.

Abstract: The application of a commonly used computer algorithm based on the group-additivity method for the calculation of the liquid viscosity coefficient at 293.15 K and the activity coefficient at infinite dilution in water at 298.15 K of organic molecules is presented. The method is based on the complete breakdown of the molecules into their constituting atoms, further subdividing them by their immediate neighborhood. A fast Gauss–Seidel fitting method using experimental data from literature is applied for the calculation of the atom groups’ contributions. Plausibility tests have been carried out on each of the calculations using a ten-fold cross-validation procedure which confirms the excellent predictive quality of the method. The goodness of fit (Q2) and the standard deviation (σ) of the cross-validation calculations for the viscosity coefficient, expressed as log(η), was 0.9728 and 0.11, respectively, for 413 test molecules, and for the activity coefficient log(γ)∞ the corresponding values were 0.9736 and 0.31, respectively, for 621 test compounds. The present approach has proven its versatility in that it enabled the simultaneous evaluation of the liquid viscosity of normal organic compounds as well as of ionic liquids.

Abstract: Liquid–liquid equilibria (LLE) experimental data for the systems of vinyl acetate + acetic acid/ethanol + water were determined at temperatures of 298.15 and 308.15 K and pressure of 101.3 KPa. The reliability of the LLE experimental data was validated by the Bachman and Hand equations. The LLE data of the two systems were fitted by the activity coefficient models of nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC), which the calculated values were in agreement with the experimental tie-line data. Meanwhile, the parameters of the two equations were also determined. Moreover, the distribution coefficients and selectivity values for the two systems were obtained from the ternary LLE data.

Abstract: In this paper, an adsorption removal mechanism of heavy metal ions (Pb, Cu, Cd, Zn, and Ni) by lignin is investigated by molecular and quantum chemical modeling. First, the lowest energy sites of lignin for heavy metal ions were investigated using a Metropolis Monte Carlo search and simulated annealing. Then, equilibrium adsorption capacities of lignin for heavy metal ions were calculated with conductor-like screening models with a segmented activity coefficients, together with generalized gradient approximation and Volsko–Wilk–Nusair density functional functional theory. These calculations followed the local pseudo-thermodynamic equilibrium at the interface of lignin and ion-containing effluent. Several kinetic Monte Carlo simulations were performed to analyze the surface kinetics of ion adsorption. The affinity of lignin for metal ions follows the order: Pb > Cu > Cd > Zn > Ni which is in agreement with experimental observations. The stability of ions follows the order: Pb > Cd > Zn > Ni > Cu, indicating that the adsorption affinity does not demand the same order of stability on ions. In addition, it was found that while the adsorption of heavy metal ions on the lignin is accessible, the adsorbed heavy metal ions, however, are less stable than the adsorbed water molecules. As such, the used lignin must be replaced by fresh lignin in a cyclic manner. While lignin provides desirable adsorption performance for single ion removal, it failed in processing of practical heavy metal ion solutions expected in environmental issues.

Abstract: The combinatorial explosion of empirical parameters in tens of thousands presents a tremendous challenge for extended Debye-Huckel models to calculate activity coefficients of aqueous mixtures of most important salts in chemistry. The explosion of parameters originates from the phenomenological extension of the Debye-Huckel theory that does not take steric and correlation effects of ions and water into account. In contrast, the Poisson-Fermi theory developed in recent years treats ions and water molecules as nonuniform hard spheres of any size with interstitial voids and includes ion-water and ion-ion correlations. We present a Poisson-Fermi model and numerical methods for calculating the individual or mean activity coefficient of electrolyte solutions with any arbitrary number of ionic species in a large range of salt concentrations and temperatures. For each activity-concentration curve, we show that the Poisson-Fermi model requires only three unchanging parameters at most to well fit the corresponding experimental data. The three parameters are associated with the Born radius of the solvation energy of an ion in electrolyte solution that changes with salt concentrations in a highly nonlinear manner.

Abstract: In the many developments of electrolyte equations of state presented over the past decades, several different properties have been in focus. A property that has not been widely used as a fitting property is salt solubility. This work presents a new parametrization of the eCPA equation of state with salt specific parameters. The focus is on accurate description of the salt solubility, and low deviation correlations are obtained for all salts investigated. The inclusion of the solubility data in the parametrization has, compared to parameters only parametrized to osmotic coefficients and activity coefficients, not significantly affected the deviations of the osmotic coefficients and activity coefficients. The average deviations of the activity coefficient does increase slightly and it was found that the increase in deviations was almost entirely due to reduced accuracy at high temperature and high molality. The model is, furthermore, compared to the activity coefficient model, Extended UNIQUAC. It is shown ...

Abstract: Liquid–liquid equilibria (LLE) data for dimethyl carbonate (DMC) + 2-methyl-1-propanol + water and DMC + 2-methyl-2-propanol + water systems were accurately determined using jacketed equilibrium cell under atmospheric pressure at 303.15 and 313.15 K. The experimental data were found to be consistent with Bachman–Brown correlation. The data were correlated well using the nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) activity coefficient models with a root-mean-square deviation (RMSD) between the experimental and calculated phase compositions of 0.004 and 0.002 for the DMC + 2-methyl-1-propanol + water system and 0.003 and 0.005 for the DMC + 2-methyl-2-propanol + water system, respectively. The effect of temperature to phase boundary was observed as well.

Abstract: The COSMO-RS methodology was used to perform a screening of ionic liquids as the most effective media for extraction of methylxanthines from natural sources. The computational methodology was validated based on the values of experimentally obtained extraction yields of caffeine from guarana seeds. A linear dependence between the extraction yields and computed thermodynamic activity coefficients of caffeine was found. A total of 23 cations and 38 anions commonly used in ionic liquids were used in the studies comprising a total of 874 ionic liquids. It was found that the ionic liquid based on the 1-dodecyl-3-methylimidazolium cation and tetraphenyl borate anion was responsible for the best extraction efficiency equal to 10.1 wt%, which is more than 50% higher than the best experimentally studied ionic liquid. Furthermore, the effectiveness of recyclability of methylxanthines from the aqueous solutions of ionic liquids was modeled. It was found that the partition coefficient values of caffeine are a good qualitative measure of re-extraction efficiency of the solvents. Since ionic liquids with high extraction efficiency have a strong affinity towards aqueous solutions, while those with high recyclability towards the organic phase it is indispensable to take both these steps into account when modeling the extraction process.

Abstract: The solvation properties of protic ionic liquids such as alkylammonium salts are still virtually uncharacterized. Both electrostatic interactions between charged particles and hydrogen bond networks in a solvent are known to hinder the solubility of apolar species. Protic ionic liquids can be a priori expected to dissolve hydrocarbons worse than aprotic ionic liquids which do not form hydrogen bonds between the ions. We measured the limiting activity coefficients of several alkanes and alkylbenzenes in propylammonium and butylammonium nitrates at 298 K. Surprisingly, we observed the tendency of higher solubility than for the same compounds in aprotic ionic liquids with a similar molar volume. The calculations of the excess Gibbs free energies using test particle insertions into the snapshots of molecular dynamics trajectories reproduced lower values in protic rather than in aprotic ionic liquids for both methane molecules and hard sphere solutes. This can be explained by the favorable solvation of apolar species in the apolar domain of nanostructured PILs. For the first time, we point out at the essential difference between the solvation properties of two types of ionic liquids and prove that it arises from the cavity formation term.