Struvite
| Struvite | |
|---|---|
 |
|
| General and classification | |
| other names | |
| chemical formula | (NH 4 ) Mg [PO 4 ] • 6H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.CH.40 ( 8th edition : VII / C.23) 01/40/01/01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal; mm 2 |
| Space group | Pmn 2 1 (No. 31) |
| Lattice parameters | a = 6.95 Å ; b = 6.14 Å; c = 11.22 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {011}, {100}, {001}, {101}, { 1 01}, {102} |
| Twinning | after {001} |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 1.711; calculated: 1.706 |
| Cleavage | good after {001}, indistinct after {010} |
| Break ; Tenacity | shell-like to uneven |
| colour | colorless, white, yellowish to brownish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.495 n β = 1.496 n γ = 1.504 |
| Birefringence | δ = 0.009 |
| Optical character | biaxial positive |
| Axis angle | 2V = measured: 37 °; calculated: 40 ° |
Struvite is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical formula (NH 4 ) Mg [PO 4 ] · 6H 2 O. It therefore consists of equal parts of ammonium , magnesium and phosphate and six parts bound crystal water and is therefore chemically a water-containing ammonium magnesium phosphate .
Struvite crystallizes in the orthorhombic crystal system and develops mostly colorless and transparent, hemimorphic crystals with an isometric, wedge-shaped or short-prismatic to tabular habit up to about three centimeters in size. Struvite can also appear white due to crystal defects or multiple twinning , and it can take on a brown color due to foreign admixtures.
Etymology and history
Struvite was first found in 1846 during archaeological excavations under the church of St. Nikolai in Hamburg and described by Georg Ludwig Ulex , who named the mineral after the naturalist and diplomat Heinrich von Struve (1772-1851).
Type material of the mineral is among other things in the Mineralogical Museum of the University of Hamburg .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , struvite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where it belonged together with Dittmarit , Hannayit , Mundrabillait , Niahit , Schertelit , Stercorit , Struvit-K and Swaknoit formed the unnamed group VII / C.23 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also classifies struvite in the category of “water-containing phosphates without foreign anions”. However, this is further subdivided according to the size of the cations involved and the ratio of the anion complex RO 4 to H 2 O. The mineral is therefore classified according to its composition in the sub-section “With large and medium-sized cations; RO 4 : H 2 O <1: 1 “, where together with Hazenite and Struvite-K it forms the unnamed group 8.CH.40 .
The systematics of minerals according to Dana also assigns struvite to the class of "phosphates, arsenates and vanadates" and there into the department of "water-containing phosphates etc.". There he is together with Hazenit and Struvit-K in the "struvite group" named after him with the system no. 01/40/01 sorted into the subsection " Phosphates containing water, etc., with A 2+ B 2+ (XO 4 ) × x (H 2 O) ".
Crystal structure
Struvite crystallizes isostructurally with struvite (K) in the orthorhombic crystal system in the space group Pmn 2 1 (space group no. 31) with the lattice parameters a = 6.95 Å ; b = 6.14 Å; c = 11.22 Å and 2 formula units per unit cell .
properties
Ammonium magnesium phosphate is one of the particularly poorly soluble compounds of ammonium and magnesium. In the long, coffin-shaped crystal form of struvite, this compound is so characteristic that it is used to detect magnesium in the classic analytical separation process .
In warm and dry air, the crystal surfaces of struvite turn white over time due to the loss of crystal water ( dehydration ).
Struvite is pyroelectric and piezoelectric , so it can build up electrical voltage through interval-like changes in heat and deformations.
Education and Locations
In nature, struvite usually forms in peaty soil mixed with cattle manure or bird or bat droppings in surface deposits or in cave floors. There it occurs in paragenesis with newberyite , hannayite , brushite and stercorite, among others .
Worldwide, struvite has so far (as of 2010) been found at around 45 sites, for example in some regions of Victoria and Tasmania in Australia; in the Gcwihaba cave near Maun in Botswana; in some regions of the Canadian provinces of Yukon , Québec , Newfoundland and Labrador ; near Aalborg in Denmark; in the Falkland Islands ; in Germany in addition to its type locality St. Nikolai (Hamburg) also near Bad Homburg vor der Höhe (Hesse) and Lüneburg (Lower Saxony); near Trepča in Kosovo; in the Malaysian state of Sarawak ; on Ichaboe Island in Namibia; in Amsterdam , the Netherlands ; on Réunion in the Indian Ocean; at Saldanha Beach on Hoedjes Island in the Western Cape of South Africa; in the US regions of Colorado , California, and Maine, and in the state of Miranda, Venezuela .
Furthermore, struvite can also form during wastewater treatment and liquid manure processing. In some places, concentrations of ammonium, magnesium and phosphate are so high that the saturation concentration of struvite is exceeded. Then layers of struvite form, which can impair the operation of sewage or slurry treatment plants.
Biological importance
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In medicine, struvite is known as a material for kidney and urinary stones . About eleven percent of kidney stones in humans are "struvite stones" and are the most common type of kidney stones in children (about 93%). They form in alkaline urine. The alkalization is caused by bacteria - above all Proteus mirabilis - mostly as a result of pyelonephritis ( inflammation of the kidney pelvis ) due to an ascending urinary tract infection . The starting material is urea , which is broken down into ammonia by the bacterial enzyme urease .
Domestic cats are particularly often affected by struvite stones. With them struvite crystals occur due to the high pH value and the high ammonium concentration even without infections.
Synthetic production and use
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Synthetically produced struvite could in the future be of great importance as a substitute phosphate fertilizer for agriculture , since it is estimated that the global phosphorus reserves will be exhausted in around 50-100 years (see also peak phosphorus ). In addition to reducing consumption, various scientific institutions and companies are therefore also trying to develop a process for the recovery of phosphates.
For example, the Fraunhofer Institute for Interfacial Engineering and Bioprocess Engineering has succeeded in extracting phosphorus and nitrogen from process and waste water using an electrochemical method . As a result, NH 4 + and PO 4 3− are precipitated as struvite (in this context also called MAP, for magnesium ammonium phosphate) with the help of a magnesium electrode. In contrast to other attempts to precipitate struvite purely chemically by adding magnesium and increasing the wastewater pH value with caustic soda, the Fraunhofer Institute's patent-pending process does not require any chemical additives. The struvite crystals obtained can then be used as a direct, high-quality and slowly releasing nutrients fertilizer.
See also
literature
- GL Ulex : About the crystals found in the foundation of the Nicolaikirche. In: Communications from the negotiations of the Natural Science Society in Hamburg, from 1856 , publisher: Heroldsche Buchhandlung, Hamburg, pp. 79-88.
- GL Ulex: struvite. In: Öfversigt af Kongliga Vetenskaps-Akademiens Förhandlingar. 1847, pp. 32–33 ( PDF 158 kB ; Swedish).
- GL Ulex: About struveit. In: New yearbook for mineralogy, geognosy, geology and petrefacts customer. 1851, pp. 51-59 ( PDF 570 kB ).
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 645 .
- Max Maurer: Treatment of urine - pure flexibility . In: Eawag News . 63d, March 2007, p. 14–16 ( PDF 1.6 MB ).
Web links
- Mineral Atlas: Struvite (Wiki)
- Database-of-Raman-spectroscopy - Struvite
- American-Mineralogist-Crystal-Structure-Database - Struvite
Individual evidence
- ↑ Webmineral - Struvite (English)
- ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 487 .
- ↑ a b c d Struvite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.2 kB )
- ↑ a b c d e f Mindat - Struvite (English)
- ↑ Georg Ludwig Ulex : About struvite . In: Annals of Chemistry and Pharmacy . tape 66 , 1848, pp. 41-44 ( digitized version ).
- ↑ Type material catalog of the University of Hamburg - struvite .
- ↑ Berthold Koletzko : Pediatric and Adolescent Medicine . 13th edition. Springer Medicine, Heidelberg 2007, ISBN 978-3-540-48632-9 , p. 478 f .
- ↑ A. Hesse: Urinary stone types. The origin of the names . In: Animal Stone Letter . tape 13 , no. 7 (1) , 2013, pp. 2 ( harnsteinanalysezentrum-bonn.de [PDF; 1.9 MB ]).
- ↑ Electrochemical process for the recovery of phosphorus. Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, accessed on January 5, 2018 .