CS-EXCHANGE KINETICS IN COMPLEX ELECTROLYTE-SOLUTIONS USING HYDROUS CRYSTALLINE SILICOTITANATES( ION)

TAM-5 is a hydrous crystalline sodium silicotitanate inorganic ion exc hanger with a high selectivity for Cs+. The kinetics of Cs+-Na+ ion ex change using TAM-5 in multicomponent electrolyte solutions were determ ined using batch experiments. For the powder, which is composed of cry stals, a single-phase, homogeneous model fit the data best. For the gr anules, which were prepared from the powder, a two-phase, heterogeneou s model resulted in an excellent fit of the data. Macropore and crysta l diffusivities were determined by fitting the model to experimental d ata collected on the powder and the granules. Intracrystalline diffusi vities were concentration dependent and were on the order of 10(-19) m (2)/s. Macropore diffusivities were on the order of 10(-10) m(2)/s. Re sistance to diffusion in the macropores was not significant for granul es with diameters less than 15 mu m. A two-phase, homogeneous model, w here liquid within the pores is in equilibrium with the solid, was als o evaluated for the granules. Surprisingly, for the granules, an excel lent fit of the data was obtained; however, the effective macropore di ffusivity was 1.1 x 10(-11) m(2)/s, an order of magnitude smaller than the macropore diffusivity found using the two-phase, heterogeneous mo del.