Laboratory‐Scale Column Testing Using Crystalline Silicotitanate (IONSIV™ IE‐911) for Removing Cesium from Acidic Tank Waste Simulant. 2: Determination of Cesium Exchange Capacity and Effective Mass Transfer Coefficient from a 500‐cm3 Column Experiment*

Abstract

A semi‐scale column test was performed using a commercial form of crystalline silicotitanate (CST) for removing radio‐cesium from a surrogate acidic tank solution, which represents liquid waste stored at the Idaho National Engineering and Environmental Laboratory (INEEL). The engineered form of CST ion exchanger, known as IONSIV™ IE‐911 (UOP, Mt. Laurel, NJ, USA), was tested in a 500‐cm3 column to obtain a cesium breakthrough curve. The cesium exchange capacity of this column matched the one obtained from previous testing with a 15‐cm3 column. A numerical algorithm using implicit finite difference approximations was developed to solve the governing mass transport equations for the CST columns. An effective mass transfer coefficient was derived from solving these equations for previously reported 15 cm3 tests. The effective mass transfer coefficient was then used to predict the cesium breakthrough curve for the 500‐cm3 column and compared to the experimental data reported in this paper. The calculated breakthrough curve showed excellent agreement with the data from the 500‐cm3 column even though the interstitial velocity was a factor of two greater. Thus, this approach should provide a reasonable method for scale up to larger columns for treating actual tank waste. Work performed for the U.S. Department of Energy under Contract No. DE‐AC07‐99ID13727.