Zeolites and their Applications Helen M. Lang West Virginia University Zeolite Mineralogy gy • Zeolites are framework silicates, with a completely linked framework of tetrahedra tetrahedra, each consisting of 4 O2surrounding a cation (usually Si4+ or Al3+) • The framework contains open cavities in the form of channels and cages • Channels and cages are occupied by H2O molecules and extra-framework extra framework cations (K+, Na+, Ca+ and others) that are commonly exchangeable • Channels are large enough to allow passage of guest species • In the hydrated phases, dehydration occurs at temperatures mostly below 400oC and is largely reversible (Gunter, 2001) Lower hardness and density than other h fframeworkk silicates ili • • • • • Mineral Quartz Feldspars Feldspathoids Zeolites H 7 6 5-6 3.5-5.5 G . 2 65 2.65 2.54-2.75 2.15-2.5 2.0-2.4 “Boiling Boiling stone” stone • Many zeolites fuse readily with marked intumescence (a swelling up which results when water is expelled during heating) • Zeolite comes from two Greek words meaning to boil and stone Zeolites’ common properties Zeolites • High degree of hydration • Low density and large void volume when hydrated y • Stability of the crystal structure when dehydrated • Cation exchange properties • Uniform molecular-sized channels in dehydrated c ysta s crystals • Ability to absorb gasses and vapors • Catalytic properties Klein, 2002 Sample Zeolite Formulas Mineral Name General Formula Analcime Na16[Al16Si32O96]·16H2O Chabazite (Ca0.5,Na,K)4[Al4Si8O24]·12H2O Clinoptilolite p ((Na,K) , )6[[Al6Si30O72]]·20H2O Erionite K2(Na,Ca0.5)8[Al10Si26O72]·28H2O Heulandite (Na K)Ca4[Al9Si27O72]]·24H (Na,K)Ca 24H2O Laumontite Ca4[Al8Si16O48]·18H2O M li Mesolite N 16Ca Na C 16[Al48Si72O240]·64H ] 64H2O Scolecite Ca8[Al16Si24O80]·24H2O Stilbite NaCa4[Al9Si27O72]·30H2O Some characteristic Cages of Zeolites From Armbruster & Gunter, 2001, Crystal Structures of Natural Zeolites, RIMG, v. 45 Schematic Representation of Chabazite Chabazite Movie – Jillian Banfield Molecular Sieve Properties Schematic illustration of how a zeolite sieve separates p a straight-chain g hydrocarbon (octane) from a branching-chain hydrocarbon (isooctane). Structure of Heulandite-Clinoptilolite Ten-membered and 8membered tetrahedral rings form channels parallel to the c-axis c-axis. Small green spheres represent Na, larger light blue spheres represent K, small yellow spheres represent Ca, large blue spheres represent H2O molecules. From Armbruster & Gunter, 2001 C 2001, Crystal t l St Structures t off Natural Zeolites, RIMG, v. 45 (Na,K,Ca0.5)7[Al7Si29O72].22H2O Two major occurrences of Zeolites • As well-crystallized well crystallized minerals found in cavities and veins in basic igneous rocks, coarse large variety of crystal forms and coarse, habits, beautiful crystals • As large deposits of fine fine-grained grained zeolites that are the diagenetic alteration products of volcanic tuffs and volcanic glass glass, recently discovered in western U.S., Cuba, Turkey Tanzania and elsewhere Turkey, Zeolite Crystals Heulandite - (Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O from Idaho Zeolite Crystals Scolecite – CaAl2Si3O10·3H 3H2O Scolecite on Stilbite CaAl2Si3O10·3H2O – NaCa4[Al9Si27O72]·30H2O Mesolite – Na2Ca2Al6Si9O30·8H2O Zeolite Crystals Analcime - Na16[Al16Si32O96]·16H2O Isometric, trapezohedron form common Zeolite Crystals Stilbite (Isle of Skye) Laumontite (India) Pretty minerals associated with zeolites Apophyllite – KCa4(Si4O10)2F-8H2O is a sheet silicate commonly assoc. with zeolites Cavansite – Ca(VO)(Si4O10)-4H2O is a sheet silicate commonly assoc. with zeolites Properties of Zeolites Table from Mumpton, 1999, La roca magica CEC smectite clays 0.8 to 1.5 meq/g Uses of Zeolites • Ammonium ion removal in waste stream treatment, sewage treatment, pet litter and aquaculture • Odor control • Heavy H metal t l iion removall ffrom nuclear, l mine, and industrial wastes • Agricultural use, such as soil conditioner and animal feed supplement Klein, 2002 Uses of Zeolites • See La roca magica: Uses of natural zeolites in agriculture and industry • FREDERICK A A. MUMPTON • Proc. Natl. Acad. Sci. USA Vol. 96, pp. 3463–3470, March 1999 Colloquium Paper Construction Applications • Dimension stone – altered tuff has for millennia been cut into blocks and used as g stone ((low density, y high g p porosity, y a building homogeneity, low cost) • “Pozzolanic” cement ((pozzolan, pozzolanic = a siliceous-aluminous material that will, in finely divided form and in the presence of moisture, react with CaOH to form a cement (Webster)) • Popped into low density pellets for use in light-weight aggregates Mumpton 1999 Dimension Stone Castel Nuovo (Naples, Italy) constructed of tuffo giallo napolitano (Mumpton 1999) [the Neapolitan Yellow Tuff (12ka): eruption of Vesuvius and caldera collapse] Waste and Wastewater Treatment • Municipal Wastewater • Drinking water Zeolite –filled, water-purification tanks - Denver, CO Mumpton 1999 Agricultural Applications • • • • Animal nutrition and food additive Agronomy and Horticulture A Aquaculture lt Animal-waste Treatment Mumpton 1999 “Zeoponics” Zeoponics • It’s It s a new kind of growth medium developed by NASA for space travel • Its name is from zeolite and hydroponic • It’s a growth medium with nutrients • It’s a nutrient delivery system • It’s an additive that makes other growth g media more effective in growing plants “Zeoponics” • See http://www.zeoponix.com/ • As a result of a Small Business Innovative Research contract with NASA, ZeoponiX, a small company in Louisville CO Louisville, CO, manufactures ZeoProTM, a combination of a nutrient-charged zeolite and slowly dissolving substances that contain phosphorous and other nutrients • Zeoponics p is expected p to be applied pp on the International Space Station and in future missions to extra-terrestrial bodies, such as Mars and the Moon ZeoPro is manufactured from a naturall source off clinoptilolite li il li Ca10(PO4)6(OH)2 Apatite Structure and Formula OH-, F-, Cl- Ca+2 Ca+2 Ca+2 PO43- Ca5(PO4)3(OH,F,Cl) Clinoptilolite Structure Adsorption and Catalysis Mumpton 1999 Nuclear Waste and Fallout Mumpton 1999 Other Applications • Consumer Products • Medical Applications Mumpton 1999 Structure of Heulandite-Clinoptilolite Ten-membered and 8membered tetrahedral rings form channels parallel to the c-axis c-axis. Small green spheres represent Na, larger light blue spheres represent K, small yellow spheres represent Ca, large blue spheres represent H2O molecules. (Na,K,Ca0.5)7[Al7Si29O72].22H2O Sample Zeolite Formulas Mineral Name General Formula Analcime Na16[Al16Si32O96]·16H2O Chabazite (Ca0.5,Na,K)4[Al4Si8O24]·12H2O Clinoptilolite (Na,K)6[Al6Si30O72]·20H2O Erionite K2(Na,Ca0.5)8[Al10Si26O72]·28H2O Heulandite (Na K)Ca4[Al9Si27O72]·24H2O (Na,K)Ca Laumontite Ca4[Al8Si16O48]·18H2O Mesolite Na16Ca16[Al48Si72O240]·64H2O Scolecite Ca8[[Al16Si24O80]]·24H2O Stilbite NaCa4[Al9Si27O72]·30H2O