Takeshi Kataoka

Adsorption of acid dye on cross-linked chitosan fibers : equilibria

Two different cross-linked chitosan fibers (ChF-A and ChF-B) were developed for use as adsorbents or ion exchangers for the recovery of dyestuffs. The concentration of amino group in the adsorbent phase was 3 to 5 times larger than that of the commercial weak-base ion exchangers and decreased with increasing degree of cros-linking. For pH = 6.9, the experimental equilibrium isotherms for adsorption of Acid Orange II (acid dye) were correlated by the BET equation for a finite number of layers. The maximum amounts of the dye adsorbed on ChF (original non-cross-linked chitosan fiber), ChF-A, and ChF-B were about 10,6, and 3.2 mol/kg, respectively, for initial liquid-phase concentration of the dye C0 = 1 mol/m3 and 298 K. These values are much larger than the corresponding values for activated carbon fiber.The amount of the dye adsorbed increased wiyh increased in C0 and decreased with increasing temperature. The presence of an inorganic salt also increased the amount of the dye adsorbed. For pH ⩽ 4, the selectivity of adsorption of the dye was extremely high and the isotherm was almost rectangular. The saturation capacities of the dye on ChF-A and ChF-B in pH ⩽ 4 were 4.8 and 3.5 mol/kg, respectively, almost the same as the concentrations of the amino group in the solid phase of ChF-A and ChF-B, respectively.

Phenol permeation through liquid surfactant membrane — permeation model and effective diffusivity☆

Abstract A mass transfer model for the permeation of phenol through liquid surfactant membranes is proposed. The model takes account of the internal mass transfer in (W/O) emulsion drop, i.e., the diffusion in the emulsion phase and that through the peripheral thin oil layer, the external mass transfer around the drop, and both the phase and chemical equilibria. According to the model, all parameters required for a computer simulation for the permeation rate of phenol can be estimated from diameters of emulsion drops and internal water droplets. The model satisfactorily predicts the experimental results for the batch permeation of phenol measured under various conditions.

Mass transfer characterization in forward and back extractions of lysozyme by AOT-isooctane reverse micelles across a flat liquid-liquid interface

Abstract The mass transfer rates in lysozyme extraction between an aqueous KCl solution and an bis(2-ethyl)sodium sulfosuccinate (AOT)-isooctane reversed micellar solution were investigated using a stirred cell with a flat liquid-liquid interface. The forward extraction rates from 0.1 kmol m−3 KCl solution of pH 6.5 to a reversed micellar phase are controlled by the diffusion in the aqueous film and the solubilization at the interface. The solubilizing rate constant, kfs, increases from 3.57 × 10−5 to 1.43 × 10−4 m s−1 in proportion to AOT concentration of 0.05 to 0.2 kmol m−3. For the back extraction of lysozyme from the reversed micellar phase to an aqueous solution of higher KCl concentration, the rate-determining step is the release process at the interface. The releasing rate constant, kbd, decreases with an increase of AOT concentration and is also two orders smaller than the kfs values. The back extraction rates are therefore very slow compared to the forward extraction rates.

Batch permeation of metal ions using liquid surfactant membranes

Abstract A mass transfer model, which was proposed for the permeation of phenol through liquid surfactant membranes, has been extended to the permeation of metal ions. Experiments on batch permeation and concentration of copper ion by LIX64N and zinc ion by di-2-ethylhexyl phosphoric acid were carried out under various conditions. The results obtained by using either Span 80 or ECA4360J as surfactant were satisfactorily simulated by the model. It was found that the permeation rate of zinc ion was greatly retarded by the use of ECA4360J.

Development of a Continuous Electric Coalescer of W/O Emulsions in Liquid Surfactant Membrane Process

Abstract The development of an efficient, continuous demulsification apparatus is needed in the industrial separation process utilizing the liquid surfactant membrane technique. A test apparatus for continuous demulsification was constructed in which a pulsed dc high potential is applied to W/O emulsions flowing between parallel copper electrodes of a perforated plate. Efficient demulsification was achieved by an operation in which the demulsified oil phase was absent between the emulsion and the upper electrode. When the feed rate of emulsion was adjusted to be equal to the demulsification rate, the latter value was proportional to the square root of the applied potential and independent of the distance between the electrodes.

Adsorption of BSA on cross-linked chitosan: The equilibrium isotherm

Abstract In order to make the large-scale chromatographic separation of proteins more economical the authors have considered the possibility of using a new adsorbent, a cross-linked chitosan (Chitopearl 3510). Equilibrium isotherms of bovin serum albumin (BSA) have been obtained. When no inorganic electrolytes except for a buffer coexisted in the solution, the isotherm was affected by pH considerably. When NACl coexisted in the solution, the isotherm was little affected not only by the concentration of NACl but also by the pH of the solution. BSA can be recovered from solutions with high concentrations of NaCl such as 1 mol dm −3 . The equilibrium data were correlated by the Langmuir equation except when no inorganic electrolytes were in the solution, in which case the selectivity was higher and the saturated capacity larger.

Surface diffusion of direct dyes in porous cellulose membranes

Abstract Adsorption of C.I. Direct Yellow 12 and C.I. Direct Blue 15 from aqueous solution onto cellulose membranes was carried out in an ultrafiltration-type cell. The dyeing process was analysed on the basis of the parallel transport mechanisms of surface and pore diffusion using Langmuir and Freundlich isotherms. The equilibrium isotherm was represented by Langmuir-type adsorption more accurately than Freundlich-type adsorption when the solution concentration of the dye was less than 0.3 mol m −3 . The differences between the theoretical concentration profiles obtained on the assumption of surface diffusion control for the Langmuir and Freundlich isotherms was negligibly small. In contrast there is a difference between the theoretical concentration profiles of pore diffusion control for Langmuir and Freundlich isotherms. The experimental uptake curves and the concentration profiles showed better agreement with the theory for surface diffusion control than for pore diffusion control. The concentration of NACl influenced the equilibrium isotherm but had little effect on the surface d

Kinetics in a chelate ion exchanger—II. Experimental

Equilibrium and kinetic data on a chelate ion exchanger are presented and discussed in relation to the theory derived in Part I. Two typical ion exchangers, which show extremely high selectivity for Cu2+ and Hg2+, are used. The experimental systems are R-Na/CuCl2, R-Na/CoCl2 and R-Na/Cr(NO3)3. Reaction rate constants, intraparticle self-diffusivity of Na+, equilibrium constants and the concentration of electrolyte in the resin phase which is in equilibrium with the bulk solution concentration are presented. When the particle radius is larger than 10−4 m, the theoretical model for diffusion control with chelate complex formation provides a good representation of the uptake curve of Cu2+. The uptake curves of Co2+ and Cr3+, for which the exchangers do not show such high selectivity, are correlated well by the usual Nernst-Planck model for ion exchange, since for these ions the chelate complex is very much weaker.

Kinetics in a chelate ion exchanger—I. Theoretical analysis

Abstract A kinetic model for sorption of metallic ions by a chelate ion exchanger is proposed in which the resistances of intraparticle diffusion and chelate complex formation reaction are both included. The Nernst-Planck equation is applied to the flux of ions in the resin particle. Analytical solutions are given for the limiting cases of diffusion control and reaction control, and numerical solutions are presented for the general case in which both resistances are significant. The analytical solution for diffusion control, which is based on the shrinking core model, gives the fractional exchange as a function of the diffusivities and valencies of the counter-ions. Uptake curves are calculated from the theoretical equations to show how the kinetics are influenced by the equilibrium constant, the diffusivity ratio of the counter-ions, the rate constant for the chelate complex formation reaction and the ionic valencies. The range in which the analytical solutions can be considered as an acceptable approximation is given.

Migration of two ions during electrolysis of glass waveguide

The entire fabrication process of an optical waveguide with a gradient index profile in planar soda‐lime glass substrate was analyzed by using the Nernst–Planck equation for the fluxes of ion species in the glass by considering the effect of an electric current. The derived equations were solved numerically and the effect of the diffusivity ratio of ions and the electric current on the concentration profile of the impurity were discussed. A method for the fabrication of the waveguide was presented and some conditions for getting a parabolic concentration profile of the impurity were presented for Ag–soda‐lime glass substrate system.