Zeolites

Zeolites are three-dimensional crystalline solids containing aluminium, silicon and oxygen arranged in a regular three-dimensional framework. They are hydrated sodium aluminosilicates of general formula Na₂O.Al₂O₃.x(SiO₂).yH₂O (x = 2 to 10; y = 2 to 6).

Zeolites have a porous structure in which monovalent sodium ions and water molecules are held only loosely; the silicon and aluminium atoms, however, are tetrahedrally coordinated to each other through shared oxygen atoms, forming a genuinely rigid framework. Although zeolites resemble clay minerals in composition, they differ sharply in their crystalline structure. Viewed as a whole, a zeolite crystal looks like a honeycomb, built from a network of interconnected tunnels and cages: water molecules can move freely in and out through these pores while the surrounding zeolite framework itself stays completely rigid. Because the pore/channel sizes across the crystal are nearly uniform, a zeolite can act as a **mol …