Katsuyuki Kubota

A convenient experimental method for measurement of zeta-potentials generating on the bubble suspended in aqueous surfactant solutions

Abstract A convenient experimental method is described for measurement of the electrophoretic mobilities or the zeta-potentials of very small air bubbles in surfactant solutions. Air was dissolved into the single-distilled water at a constant pressure of 0.5 MPa. When the pressure was balanced with atmospheric pressure suspensions consisting of very small bubbles were obtained. The three surfactants: sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and cetylpyridinum chloride were dissolved into the suspensions. The suspensions were poured into the conventional microelectrophoresis cell, and the velocities of the bubbles were measured at the so-called “stationary level”, and the zeta-potentials were determined. The experimental curves as a function of the concentrations of the surfactants were compared with those obtained from the method based on the Dorn effect reported previously. The agreement was satisfactory in general trends. Using the experimental potentials and the simple electrical double-layer theory, the surface excesses were calculated and compared with those predicted from the Gibbs adsorption equation combined with the experimental surface tensions. Both adsorption densities or the surface excesses conformed each other in general trends, suggesting the above simple theoretical considerations were confirmed experimentally. Using the two different kinds of potential measured, the distances between the slipping planes were also calculated.

A theoretical model for the estimation of the effective thermal conductivity of a packed bed of fine particles

Abstract On the basis of a number of earlier studies, we have proposed a convenient and simple model formula for predicting the effective thermal conductivity o

Adsorption Characteristics of Propylene on Molecular Sieve 4A

Abstract Instead of the previous conventional experimental techniques for the measurement of the adsorption isotherm on a gas-solid system, a technically simple and convenient method is presented. Studies on the adsorption of propylene gas on molecular sieve 4A pellets were carried out. The amount of heat generated during the course of the adsorption and the effective diffusion coefficient of propylene gas was estimated and measured, respectively. By plotting the diffusion coefficient in the form of the Arrhenius correlation, the adsorption energy was evaluated. As a result, the magnitude of the energy was found to be reasonable in the light of that reported by other investigators, and further the correlation did not depend on the pellet sizes, suggesting that micropore diffusion was predominant to mass transfer limiting processes within the pellet.

Optical measurement of slurry concentration profile in a concurrent-flow gas-slurry column

An optical technique is described which allows the measurement of steady-state slurry concentration profile in a slender concurrent-flow gas-slurry bubble column. The optically measured profile is compared with that predicted by a previously reported semiempirical dispersion model. Qualitative agreement is observed between them, and the reliability of the technique is supported by additional experimental data.