Modeling cesium ion exchange on fixed-bed columns of crystalline silicotitanate granules

A mathematical model is presented to simulate Cs exchange in fixed-bed colu mns of a novel crystalline silicotitanate (CST) material, UOP IONSIV IE-911 . A local equilibrium is assumed between the macropores and the solid cryst als for the particle material balance. Axial dispersed flow and film mass-t ransfer resistance are incorporated into the column model. Cs equilibrium i sotherms and diffusion coefficients were measured experimentally, and dispe rsion and film mass-transfer coefficients were estimated from correlations. Cs exchange column experiments were conducted in 5-5.7 M Na solutions and simulated using the proposed model. Best-fit diffusion coefficients from co lumn simulations were compared with previously reported batch values of Gu et al. and Huckman. Cs diffusion coefficients for the column were between 2 .5 and 5.0 x 10(-11) m(2)/s for 5-5.7 M Na solutions. The effect of the iso therm shape on the Cs diffusion coefficient was investigated. The proposed model provides good fits to experimental data and may be utilized in design ing commercial-scale units.