Aluminosilicates are a group of natural and synthetic silicates , the complex anions of which contain silicon and aluminum . Examples of complex anions: [AlSiO 4 ] - , [AlSi 4 O 10 ] - , [Al 2 Si 3 O 10 ] 2− . The cations are Na + , K + , Mg 2+ , Ca 2+ , and sometimes Ba 2+ and Li + .
Natural aluminosilicates are the most common minerals ; they account for up to 50% of the mass of the earth's crust . These include feldspars ( albite , orthoclase , anorthite ), clay minerals and mica .
Aluminosilicates are insoluble in water, decomposed by hydrofluoric acid , alkali melts and alkali metal carbonates . Some aluminosilicates slowly interact with CO 2 and water, weathering under natural conditions to form quartz and other minerals.
Natural aluminosilicates that do not contain a group (OH) and crystalline water are refractory, thermally stable compounds.
Synthetic aluminosilicates are obtained by hydrothermal synthesis by heating silicon oxides SiO 2 and aluminum Al 2 O 3 with metal oxides.
Application
Aluminosilicates on the earth's surface gradually erode with the formation of kaolinite - a raw material for the porcelain industry . Aluminosilicates are used as charge components in the production of glass , ceramics , and cements . Mica are used as electrical and thermal insulation materials. Nepheline is a raw material in the production of aluminum. Hydrated natural aluminosilicates ( zeolites ) and artificial permutites are used as ion exchangers (for example, for water purification), as adsorbents in chromatography , as well as in the purification, drying, and separation of gases.
Aluminosilicates are used in the food industry as food additives E554, E555, E556, E559.