Natural zeolites as cation exchangers for environmental protection

This study describes the state-of-the-art with regard to the use of natural zeolites in the protection of the environment. The review is made up of four main sections. The first introduces the possible cation exchange procedures that can be operated at an industrial level, together with the principles on which they are based. The second deals with removal of NH4+ from municipal and industrial wastewater, reporting operational results from the main industrial-scale plants, together with the most significant and recent laboratory data. The third points out the possibilities for use of natural zeolites for removal of heavy metals from water after laboratory experiments. The fourth shows how chemical and structural features make zeolites a very powerful tool for the decontamination of waters containing radionuclides.