Kinetics of ion-exchange

Abstract

The rates of exchange of a binary ion-exchange system have been computed by a method described in part 1 ¹ using an inter-diffusion coefficient D_AB which contains an activity correction term of a different form from that used in part 1. This correction term is of a Kielland type and various positive and negative values for the Kielland coefficient have been investigated. Using radioactive tracers the rates of self-diffusion and ion-exchange of the Na⁺/K⁺+ chabazite system have been measured by a new continuous flow technique. This exchange was believed to be of a Kielland type and the experimental rates were compared with the above theoretical rates. The non-ideality of this system is discussed in the light of these comparisons.

The self-diffusion coefficient of Ca²⁺ in Ca-chabazite has been measured by an area-independent method, using radioactive calcium tracer, and used to reduce the uncertainty of the results of the continuous flow measurements due to their area dependence.