The modeling of the behavior of expanded beds using Richardson-Zaki correlation in combination with the modified Stokes expression developed by Chae et al. [1] was successfully applied to the cases of small expanded beds (1 cm in column diameter) containing two different polydisperse particles used for ion-exchange operations, Chelating excellose (70-210 μm in diameter, 1.21 g/cm3 in density) and Streamline DEAE (100-300 μm in diameter, 1.20 g/cm3 in density). Empirical parameters determined for the modeling of the expansion of these small-beds (1 cm diameter) were found to have values similar to those for the case of larger expanded beds (2.5 cm in diameter) containing the same particles. This indicates that the modeling method can be utilized for the scale-up purposes of the expanded beds with various feed solutions.