Zeolite group

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The zeolite group is a species-rich family of water-containing structural silicates that contain up to 40 percent of the dry weight of water that is given off when heated. In moist air, the water can be absorbed again without destroying the structure of the mineral. From a chemical point of view, these minerals belong to the zeolite group .

The current definition of the CNMNC of the IMA is somewhat more general and also includes the phosphate minerals pahasapait and Weinebeneit as well as the framework silicate leucite :

A zeolite mineral is a crystalline substance whose structure is characterized by a framework of corner-linked tetrahedra . Each tetrahedron is made up of four oxygen atoms that surround a cation. The framework can be interrupted by OH and F groups, which occupy the tetrahedron tips but are not shared with neighboring tetrahedra. The framework contains open cavities in the form of channels and cages. These are usually occupied by H 2 O molecules and other cations, which are often exchangeable. The channels are large enough to allow guest molecules to pass through. In the water-containing phases, dehydration usually occurs at temperatures below about 400 ° C and is largely reversible.

Zeolites are usually colorless or white, but can also be colored yellow, brown or pink due to foreign admixtures. The line color is white. The crystal systems can be monoclinic , orthorhombic or cubic . Their Mohs hardness is between 3.5 and 5.5 and their density in the range from 2.0 to 2.5 g / cm³.

Etymology and history

The history of the scientific discovery of zeolites began in 1756 with the first description of a zeolite by the Swedish mineralogist Baron Axel Fredrick von Cronstedt . He described the characteristic behavior of the minerals of this group when heated in front of the soldering pipe , a lively effervescence (boiling) due to the release of bound water. He then coined the name zeolite - "boiling stone", derived from the Greek ζέω zéō for "boiling" and λίθος lithos for "stone".

The discovery of the numerous minerals of the zeolite group began in the 19th century and a European network of naturalists and collectors emerged in the names of the zeolite minerals and their discoverers, who were already working together at that time across all national and linguistic borders.

Louis Augustin Guillaume Bosc started with the first description of Chabazite in 1792 , followed by Jean-Claude Delamétherie , who described the zeolites Andréolite (1795) and Zéolithe nacrée ("pearlescent zeolite", 1797). Both were examined again by René-Just Haüy in 1801, described in more detail and renamed, Andréolite in Harmotom and Zéolithe nacrée in Stilbit . Haüy once again described analcime in the same year . Martin Heinrich Klaproth discovered in 1803 the natrolite and 1808 named Haüy to him seven years earlier as "zeolites efflorescente" described zeolite into laumontite , in recognition of the work of Gillet de Laumont , who had already collected 1,785 mineral samples. Adolph Ferdinand Gehlen and Johann Nepomuk Fuchs expanded the group of zeolites to include scolezite (1813) and mesolite (published in 1816, 1 year after Gehlen's death). In 1817 Karl Caesar von Leonhard added the Gismondin , which he named after the Italian mineralogist Carlo Giuseppe Gismondi . Gismondi, the first curator of the Mineralogical Museum of La Sapienza University in Rome, which had been founded a few years earlier , had previously described the zeolite zeagonite , which however turned out to be a mixture of phillipsite and gismondine. Conversely, it happened to Leonhard himself when Johann Reinhard Blum named the zeolite leonhardite after him in 1843 . Leonhardite then turned out to be partially drained, opaque laumontite and is today an obsolete synonym for laumontite.

Henry James Brooke , a trained lawyer who worked as a businessman and devoted his spare time to mineralogy and crystallography, identified thomsonite (named after the professor of chemistry at Glasgow University Thomas Thomson ) and heulandite , named in honor of the British collector and mineral merchant Henry , in 1820 Hay land . Two years later he still described Brewsterite , which he named after Sir David Brewster . Brewster, professor of physics at the University of St Andrews and also active in mineralogy, discovered the zeolite gmelinite in 1825 , named after the Tübingen chemist and mineralogist Christian Gottlob Gmelin and Lévyn . With the appointment of these Lévyn honored his French colleague Armand Lévy , of the zeolites in the same year Phillipsit and Herschelit (now Chabasit described Na). Also in 1825 described Wilhelm von Haidinger still the Edingtonit he after his Scottish explorer James Edington named. This was followed by Epistilbit ( Gustav Rose 1826), Faujasite ( Augustin Alexis Damour 1842), Pollucite ( August Breithaupt 1846) and Mordenite ( Henry How 1864). 1890 saw Pierre Joseph Ferdinand Gonnard the offretite and was 1896 by Antoine Lacroix honored that he discovered the zeolite Gonnardite named after him.

Numerous other zeolites were described in the 20th century, including ferrierite ( Richard Percival Devereux Graham 1918), wairakite (A. Steiner 1955), bikitaite (CS Hurlbut 1957) and cowlesite (Wise and Tschernich 1975). Tschernich was also involved in the discovery of the boggsite in 1990 , named after the collectors Robert Maxwell Boggs and his son Russel Calvin Boggs. The latter reciprocated in 1992 by naming the Tschernichit described by him and Howard, Smith and Klein .

classification

One of the first subdivisions divides the zeolite family into three groups according to their symmetry:

  • Fiber zeolites: mainly pseudotetragonal
  • Leaf zeolites: pseudo-hexagonal
  • Cube zeolites: cubic or pseudocubic

The names of these groups are based on the oldest names for zeolites, but do not always correlate with the actual morphology of the crystals. There are no sharp boundaries between these groups.

Strunz

In Strunz's system of minerals (10th edition), the zeolite family forms a separate division in the class of silicates (9), the structural silicates with zeolitic water (9th G). This department is divided into the following groups based on characteristic structural elements:

9.GA: Zeolites with T 5 O 10 units: fibrous zeolites

  • 9.GA.05: Natrolith group
  • 9.GA.10: Thomsonite group
  • 9.GA.15: Edingtonite group

9.GB: Chains of simply linked rings of 4

  • 9.GB.05 Analcime group
  • 9.GB.10 Laumontite Group
  • 9.GB.15 Yugawaralith group
  • 9.GB.20 Roggianite group
  • 9.GB.25 Goosecreekit Group
  • 9.GB.30 Montesommait group
  • 9.GB.35 Parthéit group

9.GC: chains of double-linked rings of 4

  • 9.GC.05 Gismondin Group
  • 9.GC.10 Phillipsite Group
  • 9.GC.15 Merlinoit Group
  • 9.GC.20 Mazzit group
  • 9.GC.25 pearlialite group
  • 9.GC.30 Boggsit group
  • 9.GC.35 Paulingite group

9.GD: chains of 6 rings - tabular zeolites

  • 9.GD.05 Gmelinit group
  • 9.GD.10 Chabazite group
  • 9.GD.15 Lévyn group
  • 9.GD.20 Erionite group
  • 9.GD.25 Offrétit group
  • 9.GD.30 Faujasite group
  • 9.GD.35 Mordenite group
  • 9.GD.40 Dachiardite group
  • 9.GD.45 Epistilbit group
  • 9.GD.50 ferrierite group
  • 9.GD.55 Bikitait group

9th GE: chains of T 10 O 20 tetrahedron units

  • 9.GE.05 Heulandit group
  • 9.GE.10 Stilbit group
  • 9.GE.15 Stellerit Group
  • 9.GE.20 Brewsterite Group

9.GF: Other rare zeolites

  • 9.GF.05 Terranovait Group
  • 9.GF.10 Gottardiit group
  • 9.GF.15 Lovdarit group
  • 9.GF.20 Gaultit group
  • 9.GF.30 Tschernichit group
  • 9.GF.35 Mutinaite group
  • 9.GF.40 Tschörtnerit Group
  • 9.GF.50 Thornasite group
  • 9.GF.55 Direnzoite

9.GG: unclassified zeolites

  • 9.GG.05 Cowlesit Group
  • 9.GG.10 Mountainit
  • Alflarsenite

Liebau

Liebau proposed a subdivision of porous tectosilicates based on 2 criteria:

  1. Cations of the TO 2 framework:
  2. Interchangeability of guest molecules in channels:

This results in the following groups:

1) Porosils: SiO 2 framework structures

  1. Clathrasils: SiO 2 framework structures that do not allow exchange of guest molecules
  2. Zeosils: SiO 2 framework structures that allow guest molecules to be exchanged

2) Porolite: aluminosilicate frameworks

  1. Clathralite: aluminosilicate framework structures that do not allow guest molecules to be exchanged
  2. Zeolites: aluminosilicate framework structures that allow guest molecules to be exchanged

IZA (International Zeolite Association) - Structure Commission

The structure commission of the IZA arranges the zeolites in groups with the same construction plan of the aluminosilicate framework. Currently (January 2018) 235 such structure types have been described, many of which, however, were only found in synthetic zeolites. For each structure type they introduce a 3-letter abbreviation that results from the name of the type mineral. Structure types in which framework-disrupting anions such as (OH) groups occur are identified by a preceding '-'.

Construction of the channel system in the scaffolding structures

What all zeolites have in common is a system of open channels in the aluminosilicate framework through which guest molecules can be absorbed into the structure and released again. After these channels have been linked with one another, the zeolites are divided into three groups.

Zeolites with a one-dimensional system of channels. The channels are not connected to each other.

  • CAN (cancrinite-type): The minerals of the cancrinite-type ( cancrinite , Davyne , Mikrosommit , Tiptopit ) have channels of 8-rings (8 SiO 4 tetrahedra form a ring), which would be large enough for Zeolite behavior. However, they are not counted among the zeolites, since the channels contain large volatile anions (CO 3 , SO 4 ) that prevent the passage of guest molecules.

Zeolites with a two-dimensional channel system. The channels are interconnected to form a layered system.

Zeolites with a three-dimensional channel system.

Unclassified

Education and Locations

Zeolites are found worldwide in intermediate to basic volcanics. Almost without exception, they are secondary, i.e. H. in the transformation of pyroclastic sediments in a water-rich environment at temperatures below 400 ° C and pressures below 4 to 5 kbar. They often fill cavities with fibrous, needle-like or leaf-shaped crystals. Primary formations are known only for analcime . Analcime also crystallizes directly from basaltic melts in deep magma chambers at temperatures around 600 ° C and pressures around 5–13 kbar. Zeolites are lead minerals of low-grade metamorphism from intermediate to basic rocks. The pressure-temperature range of the beginning metamorphosis is called zeolite facies after the appearance of zeolites .

The zeolite formation is essentially controlled by the following factors:

Composition:

Zeolites are formed when volcanites react with aqueous solutions. The ratio of dissolved Si to Al and the pH of the solution are the main factors controlling which zeolites crystallize. In solutions with a high Si / Al ratio, crystallization begins with quartz , with decreasing Si / Al ratio and Ca concentrations followed by mordenite , heulandite , stilbit , mesolite , thomsonite , chabazite and finally calcite . This applies to closed systems in which the solution no longer reacts with the surrounding rock. In open systems, such as those that prevail when meteoric water flows through pyroclastic rocks, Si-rich heulandite or erionite form at high pH values ​​and Si / Al ratios . Low pH values ​​and Si / Al ratios favor the formation of phillipsite .

Temperature:

Zeolite formation starts at temperatures as low as 4 ° C. With increasing temperatures, e.g. B. with increasing metamorphosis, different zeolites are formed. For basaltic compositions, a sequence from stilbit (from 4 ° C to 180 ° C) via laumontite (from 150 ° C to 300 ° C) to wairakite (from 250 ° C to 400 ° C) is common. Wairakite decomposes from 350 ° C to anorthite , quartz and water. In rocks with a basaltic composition, this reaction, together with the breakdown of phrenite, marks the transition from the zeolite facies to the green schist facies.

In Na-rich environments, analcime reacts at approx. 200 ° C with free SiO 2 (quartz) to form albite and H 2 O. This reaction is one of the reactions that mark the transition from diagenesis to metamorphosis.

Pressure:

The pressure has no significant influence on which zeolites are formed. Because of their porous structure, however, zeolites are only stable overall at low pressures (P <3 - 5 kbar). In basaltic rocks, the decomposition of zeolites with increasing pressure marks the transition from the zeolite facies to the phrenite pump line facies. Important reactions of this facies border are:

In sodium-rich rocks, analcime is converted into jadeite when the pressure increases:

Occurrences are known from almost all volcanic areas on earth, for example from the Deccan area of India, from Iceland , the Vulkaneifel or the Azores .

Crystal structure

Zeolites are structurally characterized by an ordered, microporous framework structure. The primary building blocks of this framework are TO 4 tetrahedra . The T-cations are surrounded by four oxygen anions (O 2− ) in such a way that the centers of the oxygen lie on the corners of a tetrahedron with the cation in the middle. The TO 4 tetrahedra are connected to one another via the 4 oxygen atoms at the tetrahedron corners to form a framework. Mainly Si 4+ and Al 3+ are incorporated in the T position , less often P 5+ .

These primary structural units can be linked to form a large number of different framework structures. Zeolite structures always have open cavities (channels) and often also closed cages in which substances can be adsorbed . Since only molecules can pass through the pores that have a smaller kinetic diameter than the pore openings of the zeolite structure, zeolites can be used as sieves for molecules. In nature, water is usually adsorbed in the channels, which can be removed by heating without changing the zeolite structure.

Frameworks that are made up exclusively of Si 4+ O 4 tetrahedra are electrically neutral. In all natural zeolites, part of the silicon is replaced by aluminum ions (Al 3+ ) and the aluminosilicate frameworks have negative ( anionic ) framework charges. The charge balance takes place through the incorporation of cations such as B. Na + , K + , Ca 2+ or Mg 2+ in the pore spaces of the zeolites. In water-containing zeolite, these cations are often surrounded by a hydration shell , as in aqueous solutions , and are easily exchangeable.

To describe the diverse structures of the aluminosilicate frameworks and to illustrate their structural relationships, various sets of assemblies are used from which the frameworks can be imagined. All of these assemblies are hypothetical, not physically existing units. Unlike z. B. in the case of the silicate groups of the groups , ring or chain silicates , these assemblies cannot be chemically crystallized, e.g. B. based on the type and strength of the bonds in the crystal. They serve to describe and illustrate common features of the complex structures.

Secondary building units (SBUs)

The secondary building blocks are a set of finite aluminosilicate groups and include e.g. B. (Al, Si) O 4 tetrahedral rings of various sizes (3, 4, 6, 8, 12), double rings (4-4, 6-6, 8-8) and various other assemblies of up to 10 (Al, Si) O 4 tetrahedra, but not unlimited chains or layers. The structural units are chosen so that each zeolite framework structure can be built up from only one of these structural units. The construction of a framework structure from a secondary structural unit does not necessarily take place with crystallographic symmetry operations (translation, rotation, inversion, ...). Many types of scaffolding can be constructed from various secondary building units. So z. B. the framework structure of the Chabazite type (CHA) can be built up exclusively from six rings (6) or double six rings (6-6) or four rings (4) or a roof-shaped assembly (4-2). On the pages of the Structural Commission of the IZA you can find pictures of all secondary building units.

Periodic building units (PerBUs)

The structure commission of the IZA currently uses a scheme for the construction of zeolite framework structures that is based on periodic, structurally invariant building units, the periodic building units (PerBU). Every TO 4 framework of a zeolite structure type can be built from a periodic assembly using simple symmetry operations (translation, mirroring, inversion).

The periodic units either consist of a limited number of TO 4 tetrahedra (0-dimensional) or are unlimited in 1 or 2 dimensions.

Composite building units (CBU)

The periodic units can in turn be composed of smaller, mostly finite units or chains by using simple symmetry operations. The CBU is named with three lower case letters, which result from the abbreviation of the structure type for which this structural unit is characteristic. Only for rings does the name derive from the number of rings. The pages of the IZA Structural Committee contain images of the most important “composite building units”.

  • Double rings : double quad rings (d4r), double six rings (d6r), double eight rings (d8r)
  • Cages : cavities enclosed by TO 4 tetrahedra, in which additional molecules can be enclosed but not exchanged. The TO 4 rings that form the openings (side surfaces) of the cages consist of a maximum of 6 TO 4 tetrahedra. An important representative is z. B. the sodalite cage (sod).
  • Caverns : cavities enclosed by TO 4 tetrahedra in which further molecules can be stored and exchanged. Some of the TO 4 rings that form the openings (side surfaces) of the cages consist of more than 6 TO 4 tetrahedra.
  • Chains : CBUs unlimited in one dimension, e.g. B. Zigzag chains (double zigzag chain dzc), crankshaft chains (double crankshaft chain dcc), sawtooth chains (double sawtooth chain dsc), narsarsukite chain (narsarsukite chain nsc)

There can be several options for a PerBU to build it up from different CBUs. In the appendix to the scheme for the construction of zeolite framework structures of the IZA there are illustrations with examples of how the PerBU of the various structure types can be assembled from CBUs.

Structural families

By using simple symmetry operations such as translation, rotation or mirroring, different structure types can be built up from a periodic structural unit (PerBU). All structure types that can be built from a PerBU are combined into a family. A structure type represents a completely ordered type of connection of PerBUs. Different connections of a PerBU can appear mixed in a crystal and create disordered framework structures.

These structural families are less suitable for a taxonomic classification of zeolites, since the assignment of zeolites to these groups is not always clear. Some structure types can be built up from different periodic units and the synthetic zeolites of the structure type AEI can e.g. B: be assigned to the AEI / CHA family and the AEI / SAV family. The value of the structure families lies in the description of order and disorder phenomena in the framework structures.

Of the numerous structural families, few are important for natural zeolites.

Family of fibrous zeolites : The one-dimensional PerBU of this family consists of a CBU made up of 5 tetrahedra linked to form chains. These chains can be linked together in different ways and build the structure types

  • NAT (natrolite type),
  • THO (Thomsonite type) and
  • EDI (Edingtonite type).

ABC-6 family : The two-dimensional PerBU of this family consists of a hexagonal arrangement of unlinked, flat rings of 6. The six-member rings of consecutive PerBU are connected by four-member rings to form a frame. The structure types result from the sequence of differently oriented PerBUs

  • CAN (Cancrinit type),
  • SOD (sodalite type),
  • LOS (Losod type),
  • LIO (Liottite type),
  • AFG (Afghanit type),
  • FRA (Franzinite type),
  • OFF (offretit type),
  • ERI (erionite type),
  • EAB (TMA-E type),
  • LEV (Lévyn type),
  • SAT (STA-2 type),
  • GME (gmelinite type),
  • CHA (chabazite type),
  • AFX (SAPO-56 type) and
  • AFT (ALPO-52 type).

Lovdarit family : The two-dimensional PerBU of this family results from the connection of a CBU made up of 9 TO 4 tetrahedra (two rings of 4 that are connected via a further TO 4 tetrahedron). The structure types result from different stacking of these PerBU

  • LOV (Lovdarit type)
  • VSV (VPI-7 type)
  • RSN.

use

Due to their large internal surface, zeolites are suitable for a variety of technical applications.

See also: Zeolites (group of substances) #use

See also

literature

  • A. F Cronstedt: Om en obekant bärg art, som kallas Zeolites . In: Akad. Handl. Stockholm . tape 18 , 1756, pp. 120-123 (Swedish, English translation: On an Unknown Mineral-Species called Zeolites ).
  • Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer, Berlin / Heidelberg 2009, ISBN 978-3-540-23812-6 .
  • Anthony F. Masters, Thomas Maschmeyer: Zeolites - From curiosity to cornerstone . In: Microporous and Mesoporous Materials . tape 142 , no. 2–3 , June 2011, pp. 423-438 , doi : 10.1016 / j.micromeso.2010.12.026 (English, history of zeolites).
  • Douglas S. Coombs et al .: Recommended Nomenclature for Zeolite Minerals: Report of the Subcommittee on Zeolites of the International Mineralogical Association, Commision on new Minerals and Mineral Name . In: The Canadian Minaralogiste . tape 35 , 1997, pp. 1571–1606 (English, minsocam.org [PDF; 3.5 MB ]).
  • Scott M. Auerbach, Kathleen A. Carrado and Prabir K. Dutt: Handbook of Zeolite Science & Technology . 2003 (English, download page for the individual chapters ).
  • Rudi W. Tschernich: Zeolites of the World . Geoscience Press Inc., Phoenix / Arizona 1992 (English, mindat.org [PDF; 237.0 MB ] Monograph on zeolites with a focus on the formation and distribution of zeolite minerals).
  • Frank S. Spear: Metamorphic Phase Equilibria and Pressure-Temperature-Time-Path . Mineralogical Association of America, Washington DC 1993.
  • Reinhard Fischer, Ekkehard Tillmanns: Zeolites . In: The Geosciences . tape 8 (1) , 1990, pp. 13–18 , doi : 10.2312 / geosciences . 1990.8.13 .

Web links

Commons : Zeolite  - collection of images, videos and audio files
Wiktionary: Siedestein  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c Recommended nomenclature of zeolites minerals
  2. ↑ Cronstedt 1756.
  3. ^ Jean-Claude Delamétherie: Thèorie de la Terre, T1 & 2
  4. ↑ MUSEO di MINERALOGIA UNIVERSITÀ di ROMA ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on euromin.w3sites.net @1@ 2Template: Webachiv / IABot / euromin.w3sites.net
  5. ^ Gismondin on mindat.org
  6. ^ Leonhardit on mindat.org
  7. ↑ a b Tschernich 1992: Zeolithes of the World, p. 9.
  8. ^ Klockmann: Textbook of Mineralogy, p. 789.
  9. ↑ Mineral class 9.G ninth after Strunz Edition
  10. ↑ Nickel-Strunz Silicates Classification (Version 10)
  11. ↑ Nickel-Strunz Classification - Tektosilicates 10th edition
  12. ↑ Handbook of Zeolite Science & Technology (PDF; 494 kB), Table 1
  13. ^ F. Liebau, H. Gies, RP Gunawardane, B. Marler: Classification of tectosilicates and systematic nomenclature of clathrate type tectosilicates: a proposal. In: Zeolites. 6, 1986, pp. 373-377.
  14. ^ Homepage of the IZA Structure Commission
  15. ^ Database of Zeolite Structures - Zeolite Framework Types
  16. ↑ Ch. Baerlocher, LB McCusker, DH Olsen: Atlas of Zeolithe Framework Types. 6th edition. 2007, pp. 3–11 ( limited preview in Google Book Search).
  17. ↑ a b Tschernich 1992: Zeolithes of the World, pp. 10-26.
  18. ↑ a b Spear 1993, pp. 393-394.
  19. ↑ a b c Spear 1993, pp. 399-403.
  20. ↑ Spear 1993, pp. 397-399.
  21. ^ Database of Zeolite Structures - Secondary Building Units
  22. ↑ a b c IZA Structure Commission: Schemes for Building Zeolite Framework Models. (PDF; 2.4 MB)
  23. ^ Database of Zeolite Structures - Composite Building Units
  24. ↑ Schemes for Building Zeolite Framework Models (PDF; 2.4 MB)
  25. ^ Database of Zeolite Structures - Framework Type AEI
  26. ^ Structural Commission of the IZA: The Fibrous Zeolite Family (PDF; 126 kB)
  27. ^ Structural Commission of the IZA: The ABC-6 Family (PDF; 467 kB)
  28. ^ Structural Commission of the IZA: The Lovdarite Family (PDF; 133 kB)