Ion exchange kinetics of cesium for various reaction designs using crystalline silicotitanate, UOP IONSIV IE-911

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Title: Ion exchange kinetics of cesium for various reaction designs using crystalline silicotitanate, UOP IONSIV IE-911
Author: Kim, Sung Hyun
Abstract: Through collaborative efforts at Texas A &M University and Sandia National Laboratories , a crystalline silicotitanate (CST ) , which shows extremely high selectivity for radioactive cesium removal in highly concentrated sodium solutions , was synthesized . The effect of hydrogen peroxide on a CST under cesium ion exchange conditions has been investigated . The experimental results with hydrogen peroxide showed that the distribution coefficient of cesium decreased and the tetragonal phase , the major component of CST , slowly dissolved at hydrogen peroxide concentrations greater than 1 M . A simple and novel experimental apparatus for a single -layer ion exchange column was developed to generate experimental data for estimation of the intraparticle effective diffusivity . A mathematical model is presented for estimation of effective diffusivities for a single -layer column of CST granules . The intraparticle effective diffusivity for Cs was estimated as a parameter in the analytical solution . By using the least square method , the effective diffusivities of 1 .56 ? 0 .14 x 10 -11 m2 /s and 0 .68 ? 0 .09x 10 -11 m2 /s , respectively , were obtained . The difference in the two values was due to the different viscosities of the solutions . A good fit of the experimental data was obtained which supports the use of the homogeneous model for this system . A counter -current ion exchange (CCIX ) process was designed to treat nuclear waste at the Savannah River Site . A numerical method based on the orthogonal collocation method was used to simulate the concentration profile of cesium in the CCIX loaded with CST granules . To maximize cesium loading onto the CST and minimize the volume of CST , two design cases of a moving bed , where the fresh CST is pulsed into the column at certain periods or at certain concentration of cesium , were investigated . Simulation results showed that cesium removal behavior in the pilot -scale test of CCIX experiment , where the column length is 22 ft and the CST is pulsed 1 ft in every 24 hours , was well predicted by using the values of the effective diffusivities of 1 .0 to 6 .0 ? 10 -11 m2 /s .
URI: http : / /hdl .handle .net /1969 .1 /282
Date: 2004-09-30

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Ion exchange kinetics of cesium for various reaction designs using crystalline silicotitanate, UOP IONSIV IE-911. Available electronically from http : / /hdl .handle .net /1969 .1 /282 .

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