The term molecular sieve refers to a particular property of these materials, i.e., the ability to selectively sort molecules based primarily on a size exclusion process. Although there are a wide range of possible structures a commonality is that they are formed by the linking of the corner oxygen atoms of AlO 4 and SiO 4 tetrahedra to form covalent network structures. The value of x is between 0 and 1 and y is the number of water molecules in the formula unit. yH 2O where M is either a metal ion or H +.Zeolites are the aluminosilicate members of the family of microporous solids known as ' molecular sieves', and mainly consist of silicon, aluminum, oxygen, and have the general formula M xAl xSi 1−xO 2 For this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, quartz, or other zeolites. Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater. Cation exchanged zeolites possess different acidity and catalyse different reactions. An example of the mineral formula of a zeolite is: Na 2Al 2Si 3O 10♲H 2O, the formula for natrolite. Some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution. Zeolites have a porous structure that can accommodate a wide variety of cations, such as Na +, K +, Ca 2+, Mg 2+ and others. Sodium is present as an extra-framework cation (in green). Microscopic structure of a zeolite ( mordenite) framework, assembled from SiO 4 tetrahedra. Every new zeolite structure that is obtained is examined by the International Zeolite Association Structure Commission and receives a three letter designation. As of December 2018, 253 unique zeolite frameworks have been identified, and over 40 naturally occurring zeolite frameworks are known.

Zeolites occur naturally but are also produced industrially on a large scale. The classic reference for the field has been Breck's book Zeolite Molecular Sieves: Structure, Chemistry, And Use. Based on this, he called the material zeolite, from the Greek ζέω (zéō), meaning 'to boil' and λίθος (líthos), meaning 'stone'. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that rapidly heating a material, believed to have been stilbite, produced large amounts of steam from water that had been adsorbed by the material.

Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts.

Set up ion discover dj