STUDIES OF THE HYDROUS NIOBIUM(V) OXIDE ION-EXCHANGER .6. RATE OF THEISOTOPIC EXCHANGE OF STRONTIUM IONS BETWEEN THE EXCHANGER IN THE SR-2-SOLUTION( FORM AND AQUEOUS)

The rate of the isotopic exchange of Sr2+ between hydrous niobium(V) o xide in the Sr2+ form and aqueous solution of strontium salts was dete rmined radiochemically. The exchange rate was controlled by the diffus ion of Sr2+ in the exchanger particles. The diffusion coefficients of Sr2+ and their activation energy changed with the pH in a solution equ ilibrated with exchangers. Under the conditions of constant pH, the di ffusion coefficients were constant up to a certain concentration of Sr 2+ (0.1 mol dm-3, pH 7.5), wherefrom they began to increase. The resul ts were considered in terms of the interaction between the ions and th e ion-exchange sites by comparing them with the Na+ isotopic exchange rate on this material.