Kurion's ISM works using the fundamental principles of Ion-Exchange.
There are two basic mechanisms that guide ion exchange: The Donnan Potential and Size Exclusion Principle
The Donnan Potential is as an equilibrium reaction whereby the ions in the compound move into and out of the structure of the compound for a very short amount of time. When the ions are in the water, they leave a charge deficiency or potential on the surface and in the pores of the compound. This potential attracts other ions of like charges, drawing these ions into the structure This can be seen in the first video below.
The Size Exclusion Principle describes the process in which one ion is preferred over another because of size. Pores have a defined size and shape that allow certain ions in and others out. Since certain ions (Na+, K+) are smaller than others (Cs+), the ions react differently in porous compounds. The ion that fits better in the pores (fills up most of the volume without strain) is typically preferred. Kurion's ISM's are specific for Cesium for this reason. This principle can be viewed in the second video below