10th day

ZEOLITES

The zeolite group of minerals, aluminosilicates, contains over 40 naturally occurring varieties and hundreds of varieties that are manufactured zeolite frameworks. Zeolites are useful due to their ability to act as molecular sieves. Natural zeolites form from low temperature metamorphism of igneous rocks under aqueous conditions. They are commonly found on the seafloor where mid-ocean ridge basalts, MORBs, are altered as seawater flows through fractures in the upper portions of the oceanic crust.

Molecular sieves are important because of their ability to selectively sort molecules based on size. The composition of the zeolite determines the size of the pore or cage, and its sorting function depends on the “ring size” or opening size of the pores. Zeolites are typically crushed, milled or pelletized for industrial use as molecular sieves.

Zeolites are used in commercial and domestic water purification and softening. The same properties that make zeolites great molecular sieves make then useful as sorbents. They are used in both gaseous and fluid based applications. Manufactured zeolites are used as catalysts in the petroleum industry. Zeolites are even used in clumping cat litters. By far their largest use is in laundry and dishwashing detergents, where they are used to trap calcium and magnesium allowing the detergent to work more effectively.