Pretreatment of natural zeolites covers a wide range of modification techniques leading in several products to a variety of applications. A very common pretreatment type is used for producing modified zeolites for use in ion exchange applications and in particular for the removal of cations from aqueous solutions. In these cases, pretreatment aims to remove certain ions from the structure of the material and locate more easily removable ones, prior to any ion exchange application. Practically, the result of any pretreatment operation is the increase of the content in a single cation, what is called homoionic form. The final homoionic or near homoionic state of the zeolites improves the effective exchange capacity and performance in ion exchange applications.
Keywords: Pretreatment, inorganic salts, modification, ion exchange capacity, homoionic zeolite, chemical treatment, physical treatment, modified zeolites, effective capacity, breakthrough capacity, maximum exchange level.