Surface tension prediction and thermodynamic analysis of the surface for binary solutions

The surface tensions of 100 aqueous and 200 non-aqueous binary solutions are correlated by Shereshefsky model and excellent results are obtained. The average percent deviations are about ∼1.8% for aqueous and ∼0.56% for non-aqueous binary solutions. The free energy change in the surface region is calculated and is used to obtain the excess number of molecular layers in the surface region. Furthermore, the model is used to derive an equation for the standard Gibbs energy of adsorption. Where experimental data is available for the standard Gibbs energy of adsorption, the agreement between the calculated and the experimental data is found to be very good.     

A comparison of surface tension data for aqueous dodecylammonium salt solutions

Literature data for natural solutions is compared and a wide spread of surface tension values is shown. A comparison of three techniques, capillary rise, drop weight and maximum bubble pressure failed to indicate that the technique alone was responsible. Repeating the determinations at pH 9.5 did indicate marked dependence on the technique employed. Wetting problems coupled with a pronounced time dependence of the surface tension were responsible. The bubble pressure method is shown to be the most suitable, being versatile enough to handle the dynamics. A comparison of critical micelle concentration (c.m.c.) data as a function of pH with the calculated solubility limit of dodecylamine as a function of pH revealed an interesting incompatibility; at pH greater than 9, the indicated c.m.c. was greater than the solubility limit.     

A molecular thermodynamic model for binary lattice polymer solutions

A molecular thermodynamic model for binary lattice polymer solutions with concise and accurate expressions for the Helmholtz energy of mixing and other thermodynamic properties is established. Computer simulation results are combined with the statistical mechanics to obtain the expressions. Yan et al.'s model for Ising lattice and the sticky-point model of Cumming, Zhou and Stell are incorporated in the derivation. Besides the nearest neighbor cavity correlation function obtained from the Ising lattice, the long range correlations beyond the close contact pairs are represented by a parameter λ, the linear chain-length dependence of which is obtained by fitting the simulated critical parameters of two systems with chain lengths of 4 and 200. The predicted critical temperatures and critical compositions, spinodals and coexistence curves as well as internal energies of mixing for systems with various chain lengths are in satisfactory agreement in comparison with the computer simulation results and experimental data indicating the superiority of the model over other theories. The model can serve as a basis to develop more efficient models for practical applications.     

Artificial neural network modeling for prediction of binary surface tension containing ionic liquid

In this study, a feed-forward multilayer perceptron neural network is applied to predict the surface tension of 32 binary ionic liquids (ILs)/non-ILs systems using melting point (Tm), molecular weight (Mw) and mole fraction of ILs as well as Tm and Mw of non-IL components. The data are divided into two different subsets, namely training and testing subsets, to obtain the optimum parameters of the used network and to evaluate the correlative capability of the trained network. The results of the test stage show excellent capability of the proposed network to predict/correlate the binary surface tension of ILs/non-ILs systems (AARD%: 0.93, MSE: 6.67 × 10^?7 and R²: 0.9950).     

A new model for the surface tension of binary and ternary liquid mixtures based on Peng- Robinson equation of state

Based on the surface chemical potential and Peng-Robinson equation of state,a newmodel is proposed to predict and correlate the surface tensions of binary and ternary liquid mix-tures.Using this method,the surface tensions of 73 binary and 8 ternary systems are calculatedwith average relative deviations 1.35% and 3.52% respectively.The proposed model is simple, re-liable and accurate.     

A revised surface tension model for macro-scale particle methods

A simple treatment for surface tension in immiscible fluids is proposed for macro-scale particle methods such as smoothed particle hydrodynamics (SPH) and macro-scale pseudo-particle modeling (MaPPM). By introducing a repulsion between the neighboring particles of different fluids, surface tension arises automatically, while simple equations of state are still possible for each phase. This treatment is validated by comparative simulations on the deformation of a square liquid drop in suspension using the volume of fluid (VOF) method. The relationship between surface tension and the repulsion intensity parameter in our model is obtained by the sessile drop method.     

双组分混合制冷工质沸腾换热理论研究

基于单组分工质池沸腾动态微液层预测模型,提出了预测双组分混合工质沸腾换热系数的理论模型。该模型认为沸腾换热的机理主要是由于在气泡的周期生长过程中所形成微液层的蒸发。模型中考虑了气泡生长过程中液体传质对传热的影响,给出了气泡生长过程中传热面上气液固接触的动态构造。利用本模型所得预测结果与实验结果能够较好地符合。     

Toward an intelligent approach for predicting surface tension of binary mixtures containing ionic liquids

Knowledge of the surface tension of ionic liquids (ILs) and their related mixtures is of central importance and enables engineers to efficiently design new processes dealing with these fluids on an industrial scale. It’s obvious that experimental determination of surface tension of every conceivable IL and its mixture with other compounds would be a herculean task. Besides, experimental measurements are intrinsically laborious and expensive; therefore, accurate prediction of the property using a reliable technique would be overwhelmingly favorable. To do so, a modeling method based on artificial neural network (ANN) trained by Bayesian regulation back propagation training algorithm (trainbr) has been proposed to predict surface tension of the binary ILs mixtures. A total set of 748 data points of binary surface tension of IL systems within temperature range of 283.1-348.15 K was used to train and test the applied network. The obtained results indicated that the predictive values and experimental data are quite matching, representing reliability of the used ANN model for such purpose. Also, compared with other methods, such as SVM, GA-SVM, GA-LSSVM, CSA-LSSVM, GMDH-PNN and ANN trained with trainlm algorithm the proposed model was better in terms of accuracy.     

Liquid-liquid equilibria for binary polymer solutions from modified double-lattice model

A new double-lattice model, which is capable of describing and predicting the equilibrium properties of binary polymer solutions, was proposed by modifying Hu's double-lattice model by introducing a new interaction parameter and simplifying the expression of the Helmholtz energy of mixing. Using the proposed model, we investigated phase behaviours of various binary polymer solutions. The modified double-lattice model successfully describes the phase behaviours of binary polymer solutions having an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST).     

Density and surface tension of molten alkali halides and their binary mxitures

The density and surface tension of molten alkali halides and their binary mixtures with common anions and cations are measured as a function of temperature and ionic composition. The equations are derived for their temperature dependences, with experimental error being given on a confidence level 0.95. The molar volume of the mixtures is found to deviate from additive quantities towards greater values, the deviation growing as the difference in the size of ions replacing each other increases. The relations of surface tension to molar volume of molten alkali halides were obtained. Their molar excess free surface energy, enthalpy and entropy in the surface monolayer are estimated from epxerimental data. The surface adsorption of ions in the mixtures is evaluated. It is shown to be governed by the difference in the size of ions substituting each other.     

烷基聚葡糖苷水溶液动态表面张力研究

采用最大泡压法研究了表面活性剂烷基聚葡糖苷（APG或CiGj）C8／10 G1.31和C12／14G1．43水溶液的动态表面张力（DST）;重点考察了胶束溶液中的DST曲线。将得到的13ST对时间的曲线,用Rosen模型进行处理,计算了DST的各项参数（n,ti、t^＊、tm、γm、γ0-γm、R1／2）。结果表明,随浓度增加,n、ti、t^＊、tm以及）γm减小,R1／2增大。当浓度大于cmc时,仍可用Rosen经验方程对数据进行处理,提出改进模型对胶束溶液中的动态吸附现象进行了解释。     

Prediction of the surface tension of binary systems based on the partial least squares method

To predict the surface tension of binary liquid systems, an empirical model is proposed using the partial least squares (PLS) based on the multivariate statistical analysis method. Required parameters for the PLS method to predict the surface tension of binary systems are composed of the thermophysical properties of only pure substances such as critical temperature, critical pressure, critical volume, molar volume, viscosity and vapor pressure for input data block (X) and the reported experimental surface tension data for output data block (Y). The data set for the experimental surface tension of binary liquid systems is divided into the training set for regression and the test set for predicting. An average relative error (%) results of regression and prediction indicate that the PLS method can be a useful tool for predicting the surface tension of liquid binary systems.     

Studies on surface tension and parachor of copper soap solutions in nonaqueous solvents

Colloid chemical behavior of copper soaps in nonaqueous solvents has been investigated from the surface tension results using Szyszkowski's empirical equation:γ=γ _o (1 + Xln Y) - X γ _o lnC. The parachors of the soap solutions in hydrocarbons are independent of the soap concentration. However, in alcohols these values increase with the increase of soap concentration. Hammic and Andrew's mixture law equation has been successfully applied to explain the behavior in alcoholic soap solutions.     

Development of corresponding states model for estimation of the surface tension of chemical compounds

The gene expression programming (GEP) strategy is applied for presenting two corresponding states models to represent/predict the surface tension of about 1,700 compounds (mostly organic) from 75 chemical families at various temperatures collected from the DIPPR 801 database. The models parameters include critical temperature or temperature/critical volume/acentric factor/critical pressure/reduced temperature/reduced normal boiling point temperature/molecular weight of the compounds. Around 1,300 surface tension data of 118 random compounds are used for developing the first model (a four‐parameter model) and about 20,000 data related to around 1,600 compounds are applied for checking its prediction capability. For the second one (a five‐parameter model), about 10,000 random data are applied for its development, and 11,000 data are used for testing its prediction ability. The statistical parameters including average absolute relative deviations of the results form dataset values (25 and 18% for the first and second models, respectively) demonstrate the accuracy of the presented models. © 2012 American Institute of Chemical Engineers AIChE J, 59: 613–621, 2013     

On the conditions for stability of falling films subject to surface tension disturbances; the condensation of binary vapors

Examination of available experimental information, including that on condensation of binary vapors, indicates that the Marangoni effect provides a consistent interpretation of falling film behavior, when surface tension disturbances are important. Criteria provided by the Marangoni effect are: d/db 0 for stability, where is surface tension and b film thickness, and d/db > 0 for instability; the latter is evidently a necessary but not sufficient condition. Methods are given for evaluating the sign of d/db in terms of the product of two factors, one characteristic of the system and one of the operation.     

Effect of surface tension gradient on gas hold-up enhancement in aqueous solutions of electrolytes

The effect of addition of electrolytes on gas hold-up of air/water system was investigated experimentally in a laboratory scale bubble column. The experiments were carried out with four electrolytes, namely, NaCl, MgSO₄·7H₂O, Na₂SO₄ and CaCl₂·2H₂O and the concentrations of the solutions were varied from 0 to 0.3 mol/l. Enhancement of gas hold-up was observed for all four electrolytes at concentrations less than 0.1 mol/l. With the increase in concentration, the gas hold-up showed two different trends; in Na₂SO₄ and CaCl₂·2H₂O solutions, gas hold-up formed a sharp peak after the enhancement and leveled off at a value somewhat higher than that in water, whereas in NaCl and MgSO₄·7H₂O solutions, gas hold-up leveled off immediately after the enhancement without forming any peak. Experiments were also conducted to measure the surface tensions of the solutions with special focus in the low concentration region. A strong relation between the gas hold-up enhancement and the change of surface tension with the addition of electrolyte was found. It was also observed that the concentration at which maximum value of C(dσ/dC)² i.e. (concentration × surface tension gradient with respect to concentration²) is obtained corresponds to the concentration at which maximum gas hold-up enhancement occurs.     

Phase behaviors of binary polymer solutions: The extended lattice fluid model

The generalized lattice–fluid (GLF) model is extended to predict phase behaviors of polymer/solvent systems. The GLF model gives some difficulties in describing liquid–liquid equilibria (LLE) of binary polymer solution systems due to general assumptions on its derivation. An extended lattice–fluid (ELF) model is proposed by introducing a new universal constant (C₀) and a model parameter (κ₁₁). The proposed model is then compared with experimental data for polymer/solvent systems and polymer1/polymer2 systems, which exhibit lower critical solution temperature (LCST) behaviors. Theoretical predictions and experimental results are in good agreement. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1143–1150, 1998     

The surface chemistry of water-reducible polymer solutions/dispersions 1. Surface tension behavior

Both static tension and dynamic surface tension of water-reducible (W/R) polymer solutions were carefully examined. It is shown that the cosolvent and its concentration are controlling factors in surface tension behavior for most concentration regions of W/R polymer solutions. This is true for both static and dynamic surface tensions. The polymer and its concentration have a much smaller effect on static surface tension than does the cosolvent. Much of the dynamic surface tension correlates with the bulk shear viscosity of W/R polymer solutions. The examination of cosolvent /water mixtures shows a critical solution concentration (CSC) for most cosolvents, analogous to the critical micelle concentration (CMC) in surfactant solutions. Both CSC and CMC originate from the same structural characteristics, i.e. molecules having a hydrophilic head and hydrophobic tail. Typically cosolvents have a less hydrophobic nature so values of CSC are higher than those typical of CMC for surfactants. This CSC plays a unique role in the surface tension of W/R polymer solutions. Above the CSC, constant surface tension is observed, while below the CSC a rapid increase in surface tension with decrease of cosolvent concentration occurs.