The pore sizes commercially available range from approximately 3 to approximately 8 . Some are stable in an alkaline environment, and some are stable in acidic media. They are also stable to ionizing radiation and can be used to adsorb radioactive cations. Zeolites can separate molecules based on size, shape, polarity, degree of unsaturation, among others. Zeolites can be regenerated using relatively easy methods such as heating to remove adsorbed materials, ion exchanging with sodium to remove cations, or pressure swing to remove adsorbed gases.
Zeolite modification implies an irreversible change, unlike ion exchange or adsorption.
There are a number of different ways that zeolites can be modified. The framework of the zeolite can be modified by synthesizing zeolites with metal cations other than aluminum and silicon in the framework. The framework of the zeolites can be modified by dealumination to increase the silica and increase the hydrophobic nature of the zeolite. There are many proprietary methods to modify zeolites that impart unique characteristics to them. Zeolites are available as powders or as formed products such as extrudates.