Investigation into the kinetics of ion-exchange processes accompanied by complex formation

A theoretical and experimental study of the diffusion processes in complex-formation in ion exchangers has been made. The study is based on diffusion-type equations expressing the laws of material balance for the counterions and a co-ion. These equations are complemented by the conditions of electroneutrality and absence of any electric current. In particular, the approximate solutions of the equations suggest that during the initial stages of particle conversion, the degree of conversion depends on the input concentration and is proportional to √(t), the effective diffusion being controlled by the individual diffusion coefficients for the counterions. The exact solution of the problem, for varying relations between the individual diffusion coefficient has been obtained numerically by using computers. The principles thus found have been verified experimentally for the MeM exchange in a carboxylic cation exchanger and for MeMe exchange in a complex formation vinylpyridine cation exchanger, respectively. The experimental data agree with the theoretical deductions.