A review on characterization and application of fly ash zeolites

zeolites are aluminosiliceous minerals which are well-known for their porous crystal structures and chemical characteristics. Due to these capabilities, researchers have synthesized zeolites from substances containing alumina and silica, viz. kaolin, sediments, etc. In this context, fly ash has been perceived to be a prospective raw material for zeolitization since it can undergo geopolymerisation in an alkaline medium at specific conditions of temperature and pressure. Since several decades, naturally occurring zeolites have been used for animal husbandry and agri- and aqua-culture. Furthermore, due to their hollow cage-like structure, they are also being used as molecular sieves, ion-exchangers and catalysts. Moreover, their remarkable cation-exchange capacity, CEC, enables them to be used as an additive to fertilizers so as to increase the nutrient retention capacity of the soil thereby increasing the fertility of the land and boosting the crop yield. Being an agrarian nation, the Indian economy would be greatly affected by enhanced fertility of the land following a cost-effective manner of nutrient addition and retention, wherein fly ash based zeolites would play a very significant and crucial role. This is also due to the inherent nature of the zeolites, which makes them an excellent ‘sorbent’ which helps cleaning up of the polluted soils and water bodies. Also, the sorption characteristics of zeolites can also be employed for removal of ammonia from the waste water.This calls for development of appropriate process for large-scale industrial production of the ash based zeolites, exhibiting high CEC value, for their utilization in various walks of the society (viz., environmental clean-up activities) It is believed that opportunely synthesized zeolites could become a panacea for sustainable development.