Zeolite in translation from Greek - “boiling stone”. Natural zeolite refers to stable aluminum silicates with hull organization of crystal lattice, having laminar structure.
Zeolites are the group of minerals of volcanic-sedimentary origin, tectosilicate of aluminum of alkaline and earth metals. Nowadays more than 40 nature zeolites structural types are known, more diffused are clinoptilolite, limonite, flokite, chabazite.
Sufficient technical strength of clinoptilolite, resistance to the effect of high temperatures, corrosive medium and ionizing emission, selectivity for cations of alkaline, earth, less-common, sparse, and some heavy metals, absorptive capacity and sieving effect – all that stipulates wide utilization of mineral.
Zeolite as mineral has extremely wide sphere of application in industry and agriculture economy. They are utilized in construction, petrochemistry, as gas and medium dehumidifier for industrial and potable water purification, etc.
The common point for all of minerals of zeolite group is three-dimensional aluminium silicon onoxygen hull, forming cavity and cannel systems where alkaline, earth cations and water molecules are located. Cations and water molecules are poorly connected with hull and can be partially or completely substituted (removed) via ion exchange and dehydration, and reversible, without breaking the zeolite hull. Zeolite devoid of the water is microporous crystal sponge, hole volume of which corresponds to 50% of zeolite hull. Such “sponge” with inlet diameter from 0,3 to 1nm (depends of zeolite type) is high-activity adsorbent.
Inlet diameter has strictly determined sizes. Due to this so –called molecular-screen selection occurs during sorption of molecules from gas to liquid.
Zeolite properties permit divide molecular blends even in cases when the difference in molecules’ sizes is 10-20 pm.
Ion-exchange properties of zeolite are defined by properties of chemical affinity between ions and crystal structure of zeolite. However the correspondence of sizes of inlet and zeolite hull and substitution ion is necessary, as well as it is necessary during molecule adsorption.
By using ion-exchange in zeolites, it becomes possible to emit ions, which extraction in other conditions usually presents difficulties.
Ion-screen effect permits adsorption from gas and liquid systems to nitrogen vapor, CO2, SO2, H2S, CI2, NH3. Established properties of zeolite to adsorb radioactive cesium ions from solutions, extract NH4+ from wastewater and basins, extract ions Cu, Pb, Zn, Cd, Ba, Co, Ag and other metals from industrial wastewater, purify natural gases. Zeolites absorption capacity is 30 times higher than ion-exchange tar absorption is.