Interfacial Tension Of Systems Research Articles

Interfacial tension in water/n-decane/naphthenic acid systems predicted by a combined COSMO-RS theory and pendant drop experimental study

The interfacial tension of systems containing water, n-decane, and model naphthenic acids were investigated using a predictive model based on COSMO-RS theory and experimental pendant drop measurements. Five naphthenic acid homologues that are considered to be representative of surfactants inherent to crude oil were dissolved in n-decane at equal concentrations. The interfacial tensions of the five systems at an acid concentration of 1.66 mol% relative to n-decane were experimentally determined to be 27–30 mN/m. The interfacial tensions of the five different acid-decane phases against water were also predicted using density functional theory (DFT) calculations and COSMO-RS theory. The accuracy of the predictions was very good as confirmed through pendant drop measurements of the interfacial tension. The mean-absolute-deviation between experimental and predicted values was 2.6 mN/m thus demonstrating the high predictive power of COSMO-RS theory for calculating the interfacial tension at oil–water interfaces in the presence of surface-active compounds.

Saponin-rich extract from Glycyrrhiza glabra plant, a safe matter for low interfacial tension oil/water extraction

Interfacial tension (IFT) plays an important role in the processes like extraction and emulsification, and that low level IFT is usually preferred for better hydrodynamic performance of unit operations. The present study explores the effect of a saponin-rich extract from Glycyrrhiza glabra plant on the IFT of conventional n-hexane/water system. FTIR, HPLC and LC/MS analysis indicates a 31.39% glycyrrhizic acid as the main saponin, as well as flavonoid and phenolic compounds. The system IFT was decreased to 79.5% under the apparent CMC of about 0.20 wt%. Comparison of the obtained results with the previously reported results with extract products from other plants and with respect to much lower used dosage (less than 1:50) indicates the high preference of the product. More IFT reduction could still be achieved with temperature (within 293.2–313.2 K) and pH (within 5.5–8.5). Further, NaCl and CaCl2 salts caused more IFT reduction due to salting-out effect and in the order of Hofmeister series; however, by strengthening the salting-in effect, IFT raised in the presence of Na2SO4. The obtained data at different temperatures were nicely reproduced with a correlation based on Szyszkowski adsorption isotherm, and the corresponding parameters were obtained with reasonable variations. Consequently, the adsorption thermodynamic parameters were determined.

Interfacial mass transfer in ternary liquid-liquid systems

In this work, the interfacial mass transfer in two extraction systems, namely acetone-toluene-water (System I) and hexane-heptane-methanol (System II), was examined experimentally and theoretically. The interfacial mass transfer was experimentally examined by using a Nitsch-Cell. As theoretical approach the density gradient theory (DGT) in combination with the Koningveld-Kleintjens (KK) model was used. At first, the KK-model was used to model the liquid-liquid equilibrium of System I and System II. In combination of the KK-model with the DGT, the interfacial tension was modelled by fitting the influence parameter of the DGT. To estimate the required mutual mobility coefficients in each system, bulk diffusion coefficient coefficients were used. It was shown, that the DGT in combination with a thermodynamic model and experimental information of the bulk diffusion coefficients and the system's interfacial tension is able to model the interfacial mass transfer. Moreover, it can be stated that the DGT predicts a high enrichment of acetone in System I and this enrichment has an influence on the mass transfer.

Influence of Sulphur Impurities on the Interfacial Tension between Aluminium and Cryolite Alumina Melts

The interfacial tension (IFT) between aluminium and cryolite melts containing different salt additions (AlF3, NaF,Na2SO4) has been measured during electrolysis by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when a capillary, which is moved vertically down through the molten salt layer, passes through the metal/salt interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension is strongly dependent on the n(NaF)/n(AlF3) ratio. The addition of Na2SO4 decreases the IFT of the aluminium/electrolyte interface. We also found the different influence of the conditions of electrolysis on the IFT in systems with and without Na2SO4. In systems without Na2SO4 the IFT decreases with increasing current density, and in systems with Na2SO4 it increases.

Surface Tension and Interfacial Tension of Binary Organic Liquid Mixtures

The pendant drop method, combined with efficient temperature control of the measuring cell, allows high precision measurements of both surface tension and interfacial tension. The surface tensions and liquid densities of mixtures of cyclohexane + heptane, cyclohexane + propanone, and toluene + propanone have been determined at a normal pressure of 1 bar over the temperature range from 287 K to 317 K. The surface tension data could be parametrized with a cubic polynomial. Gibbs excess surface concentrations are derived from our experimental data, and the influence of activity coefficients is discussed. The high precision pendant drop apparatus allows accurate measurements of the interfacial tension in systems with liquid−liquid phase separation. In binary mixtures of heptane + N,N-dimethylformamide, heptane + N-methyl-2-pyrrolidone, and decane + N,N-dimethylformamide, the interfacial tension was measured over a wide temperature range close to the critical solution point. The densities of the corresponding ...

Measurement of Ultralow Interfacial Tension with Application to Surfactant-Enhanced Alkaline Systems

This paper discusses the dynamic interfacial tension (IFT) variation in a system containing an acidic oil in contact with an alkaline solution which may contain a preformed surfactant. A modified technique similar, in principle, to the sessile drop technique is used for monitoring the dynamic IFT which is in the ultralow range. The technique is then applied for measuring ultralow IFTs in systems consisting of acidic oils and alkaline solutions containing preformed surfactants. The effect of aqueous phase pH, surfactant concentration, and oil phase acid concentration on the dynamic IFT variation in these systems is determined by using this technique.

Interfacial tension in systems with a supercritical component at high pressures

AbstractInterfacial tension of the binary systems pelargonic acid/ethane, pelargonic acid/carbon dioxide, linoleic acid/ethane, and linoleic acid/carbon dioxide was measured at 313, 333, and 353 K and pressures ranging up to 250 bar, using the capillary rise and Du Nouy ring methods. Both these methods yield similar values. The surface excess of supercritical components is deduced from the measurement results with the aid of Gibbs adsorption equation. The surface excess concentration increases with increasing gas activity, runs through a pronounced maximum, later decreasing rapidly to very small values. Near the surface excess maximum, a falling film of fatty acids disintegrates into a mist of tiny droplets.

Mass transfer and dynamic liquid—liquid interfacial tension. II. Theory of the relation between change of interfacial tension and change of phase volume with time, in a stirred system

We have shown that, for a nonequilibrium, closed liquid-liquid multicomponent system, with agitation, at constant temperature and pressure, a quantitative relation exists, between the rate of change of interfacial tension (IFT) and mass transfer through the interface. The conditions in which there is an increase in γ with increase in drop volume, or decrease, or constancy, are developed. We have also shown that regimes in which γ increases, or decreases, may succeed each other. This conclusion is in agreement with observations. For systems that are relevant to surfactant flooding for enhanced oil recovery, it has been shown that the Gibbsian adsorption of adsorbable and transferrable components is small: ∑ 1 n θ 1 《 1 . This is in accord with the current theories of interfacial structure in such systems: that the low values of γ observed are due to the gentle concentration gradients in the interfacial region, and not to high surfactant adsorption. While the “gradient” mechanism is responsible for the low magnitudes of IFT in systems in which one phase is a microemulsion, an “adsorption” mechanism should be invoked to explain the time rate of change of IFT, and the change of IFT with phase volume.

Surface and interfacial tension in systems of α,ω-alkanediols with n-alkanes

The surface tensions of the α,ω-alkanediols which are liquids at room temperature, and their interfacial tensions against selected n-alkanes (from heptane to hexadecane), have been measured. The surface tensions of the equilibrated phases and several mutual solubilities have also been determined. The surface and interfacial tensions all exhibit a linear dependence on (molecular weight) − 1 2 . Similarities and differences between the present results and some earlier measurements on alkane/poly(ethylene glycol) systems are discussed; the importance of the ether oxygens of the poly(ethylene glycols) in influencing interfacial properties is made evident. Extrapolation of surface and interfacial tension data yields surprisingly accurate predictions of alkane/water interfacial tensions and the surface tension of water.

Behaviour of interfacial tension in systems involving hydroxyoxime extractants for copper—II. Dynamic measurements

Behaviour of interfacial tension in systems involving hydroxyoxime extractants for copper—II. Dynamic measurements

Behaviour of interfacial tension in systems involving hydroxyoxime extractants for copper

Interfacial tension data at 28°C for a number of the β-hydroxyoxime extractants for copper are reported. Variations of interfacial tension with the pH of the aqueous phase are explained in terms of the acid-base properties of the oximes, and the variation of interfacial tension with concentration of oxime is treated by the Gibbs method. Comments are made upon the validity of this application of the Gibbs approach.

Interfacial tension in systems: A binary solution of nonpolar organic compounds-water

Interfacial tension in systems: A binary solution of nonpolar organic compounds-water