Takumi Kinugasa

Estimation for size of reverse micelles formed by AOT and SDEHP based on viscosity measurement

Abstract The size of reverse micelles formed by Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) single and AOT-sodium di(2-ethylhexyl) phosphate (SDEHP) mixed surfactants useful in protein separation and enzyme reaction, was estimated from viscosity measurement of surfactant/isooctane solution. Reversed micellar solution was prepared by injection method. At molar ratio of water to surfactant, W O , lower than 2, no reverse micelles of AOT appeared to form in isooctane. AOT reverse micelle size as estimated in this study agrees with published results obtained by other techniques. AOT–SDEHP reverse micelle shape was noted to vary from sphere to ellipsoid and size to decrease with greater molar fraction of SDEHP.

Effects of ion species in aqueous phase on protein extraction into reversed micellar solution

We investigated the effect of cations on the protein extraction into AOT/isooctane reversed micellar solutions using alkaline and alkaline-earth metal ions. Cations greatly influenced the extraction ratio of protein in an order of K+<Rb+<Cs+<Na+<Li+ in monovalent ions and Ba2+<Sr2+<Ca2+ in divalent ones. Besides, the extraction ratio is totally higher in divalent ions than in monovalent ones. This effect of ions can be explained by classifying cations into water-structure forming and water-structure breaking ions. The effect of anions is less than that of cations and is in an order of SCN−<Br−<Cl−, consistent with that of lyotropic series. In addition, the extraction ratio is higher for proteins of higher hydrophobicity and it is supposed that the hydrophobicity and stability of the protein–surfactant complex are related to extraction efficiency.

Transport behavior of protein in bulk liquid membrane using reversed micelles

Abstract Transport of lysozyme through a liquid membrane of reversed micelles of aerosol-OT (AOT) was studied. The feed phase was aqueous KCl or NaCl solution of lysozyme, and the recovery phase was aqueous KCl or BaCl 2 solution, while the membrane is the solutions of AOT with or without contacting the feed solution. The cations in feed phase are transferred through the liquid membrane and this cation transfer affects that of lysozyme and the size of reversed micelles of the membrane phase. Following transfer mechanisms have been proposed for the three systems investigated: the system NaCl–KCl, for which formation of large aggregates in the membrane phase was observed, has a so flexible interface that the micelles could become unstabilized in the membrane phase. For KCl–BaCl 2 system, the divalent ion Ba 2+ is selectively and excessively adsorbed on the interface and the negatively charged lysozyme molecules may be re-extracted at the interface of the recovery side by the electrostatic interaction with the adsorbed Ba 2+ ions. Both sides of the interfaces of the system KCl–KCl have an adequate flexibility that extraction and back-extraction of lysozyme through the membrane are attainable, although the transfer rate is rather low.

Modeling and simulation of counterflow (W/O) emulsion spray columns for removal of phenol from dilute aqueous solutions

Abstract A simple model for permeation through liquid surfactant membranes in counterflow mode was developed, which is based on the shrinking core model. Mass transfer through the external aqueous boundary film and in (W/O) emulsion phase was examined on the basis of this model, including the effect of backmixing of the continuous aqueous phase in a spray column. From the simulation results for the steady-state axial profile of solute concentration in the column, it was found that the external film resistance is predominant in the membrane permeation as compared with the diffusional resistance in (W/O) drops. The applicability of the model was illustrated by simulating phenol extraction data in literature.

Forward and Backward Extraction of Methylene Blue by using AOT/Isooctane Reversed Micellar Solution

Organic dyes, which are contained in industrial effluents, should be removed to avoid health hazards and destruction of the ecosystem. In this study, the extraction of methylene blue from aqueous solution into AOT/isooctane reversed micellar solution was investigated. It was found that methylene blue was solubilized into the waterpool within reversed micelles by electrostatic interaction with AOT. The extraction ratio of methylene blue increased with an increase in AOT concentration and a decrease in salt concentration. The methylene blue extracted reversed micelles could be recovered into fresh salt solution with high concentration. It is considered that the main driving force of forward and backward extraction of methylene blue is electrostatic interaction between cationic dye, methylene blue, and anionic surfactant, AOT. The deterioration of the forward and backward extraction behavior by using AOT/isooctane reversed micellar solution reused was not observed.

An evaluation of effective diffusivity in (W/O) emulsion drops

Effective diffusivity in a (W/O) emulsion drop was examined in terms of the extraction of ammonia from the inner aqueous droplets phase to external aqueous solution of sulfuric acid in a spray column operation. The experimental values of the effective diffusivity were compared with the values calculated from a cubic model for the permeation taking account of the effect of the surfactant on the diffusion in membrane phase and the interfacial resistance. It was confirmed that the surfactant reduces significantly the diffusivity through the membrane solution and the surfactant layer at the oil-water interface has a significant resistance to the permeation across the liquid surfactant membrane.

Removal and Recovery of Acid Azo Dyes by Solvent Extraction using Cetyltrimethylammonium Chloride

Synthetic organic dyes contained in industrial effluents should be removed to avoid health hazards and destruction of the ecosystem. In this study, the extraction of acidic azo dyes to cetyltrimethylammonium chloride (CTAC)/1-hexanol/isooctane solution was investigated. It was found that acidic dyes were extracted to the organic solution by electrostatic interaction between sulfo group of dyes and CTAC. The extraction ratio of dyes increased with an increase in CTAC concentration and with a decrease in NaCl concentration, and generally was not affected by dye concentration and pH. The extraction of acidic dyes by CTAC was explained by ion-exchange mechanism and the extraction equilibrium constants were estimated from the experimental data. AR13 and AR27 extracted to CTAC organic solution were recovered into stripping solution of high NaCl concentration, and AO52 was recovered into that of low pH. There was no deterioration of the forward and backward extraction behavior by the reused CTAC organic solution.

Improvement of lysozyme recovery method from the precipitate of protein-anionic surfactant complexes

ABSTRACT A new protein separation process using a surfactant and a polar organic solvent consists of a precipitation step and a recovery step. In the precipitation step, a protein-surfactant complex is precipitated from an aqueous solution, when an ionic surfactant, sodium di(2-ethylhexyl) sulfosuccinate (AOT), is added to an aqueous solution, including protein (lysozyme). In the recovery step, the precipitate is dissolved in a polar organic solvent, such as acetone, and the protein is recovered as precipitates when a very small amount of salt solution was added to remove surfactants from the protein-surfactant complex. However, the details of the protein recovery step from precipitate have not been studied yet. In this study, the improvement of the protein recovery step was examined from the viewpoint of a recovery ratio of protein and a remaining ratio of surfactant. The optimum NaCl concentration in the feed for the protein recovery was in the range of 0.05–0.2 kmol/m3. As the NaCl concentration in the feed increased to more than 0.2 kmol/m3, the precipitation ratio decreased due to the electrostatic screening effect of NaCl. It was found that the addition of a very small amount of NaCl solution to acetone was unnecessary when NaCl was included in the feed lysozyme solution. On the other hand, as the NaCl concentration decreased to less than 0.05 kmol/m3, the precipitation ratio was decreased due to the low re-precipitation of protein by the addition of a small amount of NaCl solution in acetone. In the case of the feed containing no salt, the desired NaCl concentration added to acetone was in the range above 0.2 kmol/m3. In addition, the most suitable volume ratio of acetone to feed was found to be 0.2.