Wang Zi-hao

Estimation of fluid-fluid interfacial tensions of multicomponent mixtures

Abstract For estimating the gas-liquid interfacial tension (surface tension) of multicomponent liquid mixtures, an equation has been developed from thermodynamics with the local composition concept proposed by Wilson. The equation has been successfully tested for correlating data for a large number of binary systems. With the binary parameters obtained from binary data, the equation has been satisfactorily used to predict the surface tension of ternary and quaternary systems. For estimating liquid-liquid interfacial tension, an equation relating interfacial tension to the equilibrium compositions of the liquid phases has been developed from an interfacial layer model. Using the empirical constant determined by fitting the experimental data to the equation reduced for binary systems, the proposed equation gave satisfactory results for a large number of ternary systems.

A surface tension model for liquid mixtures based on the Wilson equation

A new surface tension equation based on the thermodynamic definition of surface tension and the expression of Gibbs free energy is proposed, which is different from existing ones with respect to theoretical background and formulation. By using the Wilson equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived for liquid mixtures. The feasibility of the equation has been tested in terms of correlation for 124 binary systems and by prediction for 16 multicomponent systems at ambient temperatures with overall average absolute relative deviation (AAD) of 0.54 and 1.36%, respectively. The model parameters obtained by correlating binary surface tension at one temperature can be used to predict surface tension at other temperatures with good accuracy. It is shown that the new equation is simple in terms of calculation, accurate in correlation and prediction and is applicable to large variety of systems.

The entrainment swelling of emulsion during lactic acid extraction by LSMs

Abstract Studies on the entrainment swelling of emulsion during batch extraction of lactic acid using a liquid surfactant membrane (LSM) system are reported. The concept of effective concentration of surfactant in membrane phase has been proposed, considering the high adsorption density of the surfactant at the droplet interfaces in the LSM system. The swelling caused by emulsification during the initial dispersion process was investigated. The swelling ratio was measured by a density method. A model for estimating the “emulsification” swelling ratio, F se , has been proposed, based on a mechanism of swelling due to the entrainment of water resulting from the interfacial turbulence and emulsification in the initial dispersion process.

Development of a new reversed micelle liquid emulsion membrane for protein extraction

A new type of liquid emulsion membrane containing reversed micelles for protein extraction is introduced. A three-step extraction mechanism is proposed including solubilization, transportation, and release of the protein. The surfactants Span80 and sodium di(2-ethylhexyl)sulfosuccinate (AOT) are used to stabilize the membrane phase and to build up the reversed micelles, respectively. alpha-Chymotrypsin was used as the model protein. The condition in the internal phase inhibits the solubilization process of the already extracted protein back into reversed micelles. Concerning the solubilization, we studied the influence of the AOT concentration in the membrane phase and the ionic strength in the external phase. The extraction rate increases with higher AOT concentration and decreases with higher ionic strength. Using NaCl in the external phase led to better extraction results than using KCl. Maximum extraction results of 98% into the membrane phase and 65% into the internal phase were obtained. This condition retained 60% of the enzymes activity. The concentration of KCl in the internal phase does not affect the solubilization rate but the release into the internal phase. By this way the ionic strength in the internal phase is used as the driving force for the protein release. The solubilization process is much faster than the diffusion and the releasing process, as found by variation of the extraction time. The influence of the operating conditions on the membrane swelling is also discussed.