Helen M. Lang West Virginia University

Transcription

1 Zeolites and their Applications Helen M. Lang West Virginia University

2 Zeolite Mineralogy Zeolites are framework silicates, with a completely linked framework of tetrahedra, each consisting of 4 O 2- surrounding a cation (usually Si 4+ or Al 3+ ) The framework contains open cavities in the form of channels and cages Channels and cages are occupied by H 2 O molecules and 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 400 o C and is largely reversible (Gunter, 2001)

3 Lower hardness and density than other framework silicates Mineral H G. Quartz Feldspars Feldspathoids Zeolites

4 Boiling 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

5 Zeolites common properties High degree of hydration Low density and large void volume when hydrated Stability of the crystal structure when dehydrated Cation exchange properties Uniform molecular-sized channels in dehydrated crystals s Ability to absorb gasses and vapors Catalytic properties Klein, 2002

6 Sample Zeolite Formulas Mineral Name Analcime Chabazite General Formula Na 16 [Al 16 Si 32 O 96 ] 16H 2 O (Ca 0.5,Na,K) 4 [Al 4 Si 8 O 24 ] 12H 2 O Clinoptilolite (Na,K) 6 [Al 6Si 30O 72 ] 20H 2O Erionite Heulandite Laumontite K 2 (Na,Ca 0.5 ) 8 [Al 10 Si 26 O 72 ] 28H 2 O (Na,K)Ca 4 [Al 9 Si 27 O 72 ] 24H 2 O Ca 4 [Al 8 Si 16 O 48 ] 18H 2 O Mesolite Na 16 Ca 16 [Al 48 Si 72 O 240 ] 64H 2 O Scolecite Stilbite Ca 8 [Al 16 Si 24 O 80 ] 24H 2 O NaCa 4 [Al 9 Si 27 O 72 ] 30H 2 O

7 Some characteristic Cages of Zeolites From Armbruster & Gunter, 2001, Crystal Structures of Natural Zeolites, RIMG, v. 45

8 Schematic Representation of Chabazite Chabazite Movie Jillian Banfield

9 Molecular Sieve Properties Schematic illustration of how a zeolite sieve separates a straight-chain hydrocarbon (octane) from a branching-chain hydrocarbon (isooctane).

10 Structure of Heulandite-Clinoptilolite Ten-membered and 8- membered tetrahedral rings form channels parallel to the c-axis. Small green spheres represent Na, larger light blue spheres represent K, small yellow spheres represent Ca, large blue spheres represent H 2 O molecules. (Na,K,Ca 0.5 ) 7 [Al 7 Si 29 O 72 ]. 22H 2 O From Armbruster & Gunter, 2001, Crystal Structures t of Natural Zeolites, RIMG, v. 45

11 Two major occurrences of Zeolites As well-crystallized minerals found in cavities and veins in basic igneous rocks, coarse, large variety of crystal forms and habits, beautiful crystals As large deposits of fine-grained zeolites that are the diagenetic alteration products of volcanic tuffs and volcanic glass, recently discovered in western U.S., Cuba, Turkey, Tanzania and elsewhere

12 Zeolite Crystals Heulandite - (Ca,Na) 2-3 Al 3 (Al,Si) 2 Si 13 O 36 12H 2 O from Idaho

13 Zeolite Crystals Scolecite CaAl 2 Si 3 O 10 3H 2 O Scolecite on Stilbite CaAl 2 Si 3 O 10 3H 2 O NaCa 4 [Al 9 Si 27 O 72 ] 30H 2 O Mesolite Na 2 Ca 2 Al 6 Si 9 O 30 8H 2 O

14 Zeolite Crystals Analcime - Na 16 [Al 16 Si 32 O 96 ] 16H 2 O Isometric, trapezohedron form common

15 Zeolite Crystals Stilbite (Isle of Skye) Laumontite (India)

16 Pretty minerals associated with zeolites Apophyllite KCa 4 (Si 4 O 10 ) 2 F-8H 2 O is a sheet silicate commonly assoc. with zeolites Cavansite Ca(VO)(Si 4 O 10) -4H 2 O is a sheet silicate commonly assoc. with zeolites

17 Properties of Zeolites Table from Mumpton, 1999, La roca magica CEC smectite clays 0.8 to 1.5 meq/g

18 Uses of Zeolites Ammonium ion removal in waste stream treatment, sewage treatment, pet litter and aquaculture Odor control Heavy metal ion removal from nuclear, mine, and industrial wastes Agricultural use, such as soil conditioner and animal feed supplement Klein, 2002

19 Uses of Zeolites See La roca magica: Uses of natural zeolites in agriculture and industry FREDERICK A. MUMPTON Proc. Natl. Acad. Sci. USA Vol. 96, pp , March 1999 Colloquium Paper

20 Construction Applications Dimension stone altered tuff has for millennia been cut into blocks and used as a building stone (low density, high porosity, 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

21 Dimension Stone Castel Nuovo (Naples, Italy) constructed of tuffo giallo napolitano (Mumpton 1999) [the Neapolitan Yellow Tuff (12ka): eruption of Vesuvius and caldera collapse]

22 Waste and Wastewater Treatment Municipal Wastewater Drinking water Zeolite filled, water-purification tanks - Denver, CO Mumpton 1999

23 Agricultural Applications Animal nutrition and food additive Agronomy and Horticulture Aquaculture Animal-waste Treatment Mumpton 1999

24 Zeoponics 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 media more effective in growing plants

25 Zeoponics See As a result of a Small Business Innovative Research contract with NASA, ZeoponiX, a small company in Louisville, CO, manufactures ZeoPro TM, a combination of a nutrient-charged zeolite and slowly dissolving substances that contain phosphorous and other nutrients Zeoponics is expected to be applied on the International Space Station and in future missions to extra-terrestrial bodies, such as Mars and the Moon

26 ZeoPro is manufactured from a natural source of clinoptilolite il Ca 10 (PO 4 ) 6 (OH) 2

27 Apatite Structure and Formula OH -, F -, Cl - Ca +2 Ca +2 Ca +2 PO 4 3- Ca 5 (PO 4 ) 3 (OH,F,Cl)

28 Clinoptilolite Structure

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31 Adsorption and Catalysis Mumpton 1999

32 Nuclear Waste and Fallout Mumpton 1999

33 Other Applications Consumer Products Medical Applications Mumpton 1999

34 Structure of Heulandite-Clinoptilolite Ten-membered and 8- membered tetrahedral rings form channels parallel to the c-axis. Small green spheres represent Na, larger light blue spheres represent K, small yellow spheres represent Ca, large blue spheres represent H 2 O molecules. (Na,K,Ca 0.5 ) 7 [Al 7 Si 29 O 72 ]. 22H 2 O

35 Sample Zeolite Formulas Mineral Name Analcime Chabazite Clinoptilolite Erionite Heulandite Laumontite Mesolite Scolecite Stilbite General Formula Na 16 [Al 16 Si 32 O 96 ] 16H 2 O (Ca 0.5,Na,K) 4 [Al 4 Si 8 O 24 ] 12H 2 O (Na,K) 6 [Al 6 Si 30 O 72 ] 20H 2 O K 2 (Na,Ca 0.5 ) 8 [Al 10 Si 26 O 72 ] 28H 2 O (Na,K)Ca 4 [Al 9 Si 27 O 72 ] 24H 2 O Ca 4 [Al 8 Si 16 O 48 ] 18H 2 O Na 16 Ca 16 [Al 48 Si 72 O 240 ] 64H 2 O Ca 8 [Al 16 Si 24 O 80 ] 24H 2 O 8 [ ] 2 NaCa 4 [Al 9 Si 27 O 72 ] 30H 2 O