Showing papers by "Takeshi Kataoka published in 1985"

Intraparticle mass transfer in bidispersed porous ion exchanger part II: Mutual ion exchange

Abstract: Intraparticle mass transfer of mutual ion exchange in MR-type resin was analyzed based on the assumption of parallel diffusion of counter ions in the solid phase and the macropore. Local equilibrium was also assumed between the concentration of counter ions in the solid phase and in the macropore, and the mass action law was applied. The Nernst-Planck equation was applied to the fluxes of ions diffusing through the solid phase and the macropore. The derived equations were solved numerically by using macropore and solid phase diffusivities obtained earlier by isotopic ion exchange. The theoretical lines agreed fairly well with the experimental uptake curves of R-H-NaCl, R-Na-HCl, R-Na-Zn(NO3)2, R-Zn-NaNO3 and R-H-ZnCl2 systems. The lower the concentration of bulk solution Co is, the smaller the effect of Co on the ion exchange rate becomes. The experimental uptake curves of Co ≤ 0.01 (mmole/cm3) were not affected by Co but agreed fairly well with the theoretical line for solid phase diffusion control. An approximate estimation method for obtaining the uptake curve was also proposed. This method gave fairly good approximation for equal valence ion exchange and for R-Na-Zn(NO3)2 systems. On a analyse le transfert de masse intraparticulaire dans l'echange d'ions dans une resine de type MR; dans l'hypothese d'une diffusion parallele des contre-ions dans la phase solide et dans les macropores. On a aussi suppose l'equilibre local entre la concentration des contre-ions dans la phase solide et dans les macropores, et on a applique la loi d'action de masse. On a aussi applique l'equation de Nernst-Planck aux flux des ions diffusant par la phase solide et par les macropores. On a resolu numeriquement les equations etablies, en employant les diffusivites en phase solide et dans les macropores obtenues anterieurement par echange isotopique d'ions. Les courbes theoriques ont assez bien concorde avec les courbes d'adsorption experimentale pour les systemes de R-H-NaCl, R-Na-HCl, R-Na-Zn(NO3)2, R-Zn-NaNO3 et R-H-ZnCl2. Plus la concentration globale de la solution Co etait faible, et plus l'effet de Co sur la vitesse de l'echange d'ions est faible. Les courbes d'absorption experimentale a Co s 0,01 mmole/cm3 ne sont pas affectees par Co, mais elles sont en assez bon accord avec la courbe theorique pour un phenomene controle par la diffusion en phase solide. On propose aussi une methode approchee d'evaluation pour obtenir la courbe d'absorption; cette methode fournit une assez bonne approximation, dans le cas des systemes d'echange d'ions de meme valence et pour R-Na-Zn(NO3)2.

Migration of two ions during electrolysis of glass waveguide

Abstract: 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.

Intraparticle mass transfer in thermally regenerable ion exchanger

Abstract: An intraparticle mass transfer model was developed for a thermally regenerable ion exchanger which is coagulated by weak acidic and basic microspheres. It was assumed that salt diffuses (hrough macropore and microspheres in the radial direction of a resin particle. Uptake curves were measured not only in [RaCOOH + RbN] + NaCl ) [RaCOONa + RbNHCl] system but also in [RaCOO22Na+ + RaN] + Na+ )[RaCOONa+ + RbN] + 22Na+ and [RaCOOH + RaN] + HCl ) [RaCOOH + RbNHCl] systems. Macropore diffusivity Dp.Na, tortuosity factor τp and diffusivity through weak acidic microspheres Da,Na were obtained from the isotopic ion exchange. The uptake curves of HC1 gave diffusivity through weak basic microspheres.Db,Hcl The experimental uptake and desorption curves of NaCl agreed fairly well with the theoretical values. Diffusions through both macropore and microspheres were significant. The diffusivity through microspheres Db,Nacl NaCI are smaller than Da,Na. and can be estimated by DbHcl approximately.