- —zeolitic /zee'euh lit"ik/, adj./zee"euh luyt'/, n. Mineral.any of a group of hydrated silicates of aluminum with alkali metals, commonly occurring as secondary minerals in cavities in basic volcanic rocks: used for their molecular sieve properties because they undergo dehydration with little or no change in crystal structure.[1770-80; < Gk ze(în) to boil + -O- + -LITE]
* * *Any member of a family of hydrated aluminosilicate minerals that have a framework structure enclosing interconnected cavities occupied by large metal cations (positively charged ions)generally sodium, potassium, magnesium, calcium, and bariumand water molecules.The ease of movement of ions and water within the framework allows reversible dehydration and cation exchange, properties that are exploited in water softeners and molecular sieves for pollution control, among other uses.
* * *▪ mineralany member of a family of hydrated aluminosilicate minerals that contain alkali and alkaline-earth metals. The zeolites are noted for their lability toward ion-exchange and reversible dehydration. They have a framework structure that encloses interconnected cavities occupied by large metal cations (positively charged ions) and water molecules.The essential structural feature of a zeolite is a three-dimensional tetrahedral framework in which each oxygen atom is shared by two tetrahedra. If all tetrahedra contained silicon the framework would be neutral; substitution of aluminum for silicon creates a charge imbalance and requires other metal ions to be present in relatively large cavities of the framework. In naturally occurring zeolites these metal ions are typically mono- or di-valent ions such as sodium, potassium, magnesium, calcium, and barium. Zeolites are similar to feldspar minerals except that cavities are larger in zeolites and water is generally present. Structurally, zeolites are classified by the types of structural units that compose the framework, such as rings or polyhedra types. The cavities formed by the framework units have diameters ranging from about 2 to 8 angstroms, which permits relatively easy movement of ions between cavities.This ease of movement of ions and water within the framework allows reversible dehydration and cation exchange, properties which vary considerably with chemical and structural differences. Dehydration character varies with the way water is bound in the structure. For those zeolites in which water is tightly bound, dehydration occurs at relatively high temperatures; by contrast, in certain zeolites with large cavities, some of the water can be released at low temperatures. The rate of ion exchange depends on the size and connections between cavities. Some ions are excluded because of specific structural properties.Zeolite properties are exploited through commercial production of zeolites with particular structural and chemical features. Some commercial uses include separation of hydrocarbons, such as in petroleum refining; drying of gases and liquids; and pollution control by selective molecular adsorption.Natural zeolites occur in mafic volcanic rocks as cavity fillings, probably as a result of deposition by fluids or vapours. In sedimentary rocks zeolites occur as alteration products of volcanic glass and serve as cementing material in detrital rocks; they also are found in chemical sedimentary rocks of marine origin. Extensive deposits of zeolites occur in all oceans. Metamorphic rocks contain a sequence of zeolite minerals useful for assigning relative metamorphic grade; these minerals form at the expense of feldspars and volcanic glass.
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Zeolite — e o*lite, n. [Gr. ? to boil + lite: cf. F. z[ e]olithe.] (Min.) A term now used to designate any one of a family of minerals, hydrous silicates of alumina, with lime, soda, potash, or rarely baryta. Here are included natrolite, stilbite,… … The Collaborative International Dictionary of English
zeolite — [zē′ə līt΄] n. [Swed zeolit < Gr zein, to boil (see YEAST): from its swelling up when heated] 1. any of a large group of natural hydrous aluminum silicates of sodium, calcium, potassium, barium, etc., chiefly found in cavities in igneous rocks … English World dictionary
Zeolite — Zeolites (Greek, zein , to boil ; lithos , a stone ) are hydrated aluminosilicate minerals and have a micro porous structure. The term was originally coined in the 18th century by a Swedish mineralogist named Axel Fredrik Cronstedt who observed,… … Wikipedia
zéolite — zéolithe ou zéolite [ zeɔlit ] n. f. • 1783, 1756; du gr. zeô, zein « bouillonner » et lithe ♦ Minér. Silicate naturel hydraté dont les gisements se rencontrent surtout dans les cavités des laves basiques. Zéolithes artificielles. ● zéolite ou… … Encyclopédie Universelle
Zeolite — Zéolithe Zéolithe … Wikipédia en Français
zeolite — Any of a large family of crystalline metal oxide materials characterized by the presence of extensive regular interconnected pore systems. Most are based on mixtures of aluminum and silicon oxides, while others have phosphorous and other elements … Petroleum refining glossary
zeolite — noun Etymology: Swedish zeolit, from Greek zein to boil + o + Swedish lit lite, from French lite more at yeast Date: circa 1777 any of various hydrous silicates that are analogous in composition to the feldspars, occur as secondary minerals in… … New Collegiate Dictionary
zeolite — an ammonia removing, ion exchange resin used in freshwater aquaria. It also can act biologically and mechanically. Does not last long and must be regenerated by soaking in a strong salt solution for a day. Particularly useful for temporary… … Dictionary of ichthyology
zeolite — noun Any of several minerals, aluminosilicates of sodium, potassium, calcium or magnesium, that have a porous structure; they are used in water softeners and in ion exchange chromatography … Wiktionary
zeolite — A naturally occurring hydrated sodium aluminum silicate, Na2O Al2O3 (SiO2)x (H2O)x, used for softening of hard water by exchanging its Na+ for the Ca2+ of the water; thus z. is an ion exchanger. Some synthetic ion exchangers are termed synthetic… … Medical dictionary