Aluminum hydroxide
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| __ Al 3+ __ O 2− __ H + | ||||||||||||||||||||||
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| Surname | Aluminum hydroxide | |||||||||||||||||||||
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| Ratio formula | Al (OH) 3 | |||||||||||||||||||||
| Brief description |
white odorless solid |
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| properties | ||||||||||||||||||||||
| Molar mass | 78.00 g mol −1 | |||||||||||||||||||||
| Physical state |
firmly |
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| density |
2.42 g cm −3 |
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| Melting point |
150–220 ° C ( release of crystal water) |
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| solubility |
almost insoluble in water (1.5 mg l −1 ) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||||||||
The aluminum hydroxide , molecular formula Al (OH) 3 , is a naturally in the form of various minerals occurring chemical compound from the group of hydroxides . Aluminum hydroxide is differentiated according to its appearance and has an amphoteric character.
Modifications
From Aluminiumorthohydroxid Al (OH) 3 three are modifications known:
- monoclinic , γ-Al (OH) 3 : known as mineral gibbsite (hydrargillite)
- hexagonal , α-Al (OH) 3 : Known as the mineral bayerite
- triklin : Known as the mineral north strandite
There is also the lower water content aluminum metahydroxide ( aluminum oxide hydroxide ) AlO (OH), of which the following variations exist:
- Orthorhombic , α-AlO (OH): Known as the mineral diaspore
- orthorhombic , γ-AlO (OH): Known as the mineral boehmite
Occurrence
The aluminum hydroxide modifications gibbsite and bayerite occur naturally as components of bauxite .
synthesis
By precipitating aluminum hydroxide with ammonia in an aqueous aluminum salt solution, an amorphous and voluminous form called aluminum oxide hydrate is obtained , which slowly changes over time via bayerite and boehmite into the thermodynamically stable hydrargillite. By heating hydrargillite to 300 ° C, partial dehydration to crystallized boehmite is effected. Diaspore is represented by heating boehmite in aqueous sodium hydroxide solution under pressure (50 MPa) to 380 ° C.
Is carbon dioxide in a sodium aluminate solution introduced, is formed at 80 ° C, crystalline α-Al (OH) 3 . At a lower temperature, bayerite would initially be formed, which gradually converts to α-Al (OH) 3 .
On a large scale, aluminum hydroxide is produced from bauxite by digestion with sodium hydroxide using the Bayer process . The largest manufacturer in Germany was VAW . Today, aluminum hydroxide is only produced on a large scale in Germany by Aluminum Oxid Stade GmbH.
If the various aluminum hydroxide forms are dehydrated (calcined) by vigorous heating, aluminum oxide Al 2 O 3 is obtained .
Responsiveness
Under the action of bases , aluminum hydroxide is converted into aluminates :
![{\ mathrm {Al (OH) _ {3} + OH ^ {-} \ longrightarrow [Al (OH) _ {4}] ^ {-}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/0c7af9a5e107093811a0db1265cd34155f655299)
In acids it reacts to the corresponding aluminum salt solutions.
The rate of reaction depends on the modification involved, so the solubility in acids is much greater in the case of an amorphous structure than in the case of a crystalline form.
Use in industry
Aluminum hydroxide appears as bayerite and hydrargillite as intermediate products in the production of aluminum using the Bayer process and is obtained there as a by-product ("moisture hydrate") and used as a raw material for the production of various aluminum compounds in industry, e.g. B. Preparation of sodium aluminate solution or polyaluminum chloride .
Aluminum hydroxide (hydrargillite, also called ATH from aluminum trihydrate) is the world's most important mineral flame retardant . It is particularly characterized by its environmental friendliness (halogen-free) and efficiency as a smoke gas suppressant.
Application and effects in the human body
personal hygiene
Aluminum hydroxide should not be confused with aluminum salts such as aluminum chloride , which in antiperspirants closes sweat glands. Sunscreens and toothpastes contain aluminum hydroxide. In sun creams, aluminum hydroxide is used to coat the mineral sun protection filter titanium dioxide.
Sexual Practice in Africa
Aluminum hydroxide stones or powder are used for a sexual practice that is common in southern Africa . By inserting it into the vagina, the vaginal mucous membrane is dried out, which is supposed to increase the man's pleasure (see also dry sex ). The practice has been linked to increased HIV transmission.
Medical applications
For dialysis patients
In medicine, aluminum hydroxide is used as a phosphate binder in dialysis patients . Long-term use showed cerebral toxicity ( dementia ) as well as bone toxicity , which is why use of a maximum of four weeks is recommended.
Neutralization of stomach acid in heartburn
Aluminum hydroxide is also used for antacids . An antacid (plural antacids ) is a medicine used to neutralize stomach acid . The antacid is a weak base or the salt of a weak acid , so its mechanism of action can be explained, among other things, by the buffering of gastric acid. The area of application for antacids is the symptomatic treatment of diseases in which gastric acid is to be bound. These include heartburn , acid regurgitation, and acid-induced stomach pain. Most of the time, however, antacids are used as over -the- counter self-medication for reflux esophagitis (inflammation of the esophagus).
Depot carrier in subcutaneous immunotherapy
For a desensitization - especially with subcutaneous immunotherapy - aluminum hydroxide is usually used as a depot carrier. As a result, the allergens are continuously released over a longer period of time.
Effect enhancers in vaccines
Aluminum hydroxide has been used as an adjuvant (auxiliary substance) for inactivated vaccines (i.e. those that do not contain any pathogens capable of reproducing) since 1926 until today . It is present as oxyhydroxide (AlOOH), since crystalline Al (OH) 3 with its small surface (approx. 20 to 50 m 2 / g) is a poor absorbent - in contrast to the oxyhydroxide (approx. 500 m 2 / g) . Aluminum oxyhydroxide is a stoichiometric compound, its surface consists of Al-OH and Al-O-Al groups. It is structurally similar to boehmite and has an isoelectric point of 9 to 11. At a pH of 7.4, its surface is therefore positively charged.
Since the 1980s, it has replaced calcium phosphates used analogously in DTP and polio vaccines . In the dosage used, it should be non-toxic, but it causes a local tissue irritation and thus causes a Th2 reaction , which the vaccine alone does not achieve to a sufficient extent. So far there are few alternatives for aluminum hydroxide that are approved, work equally well and have no disadvantages. Aluminum hydroxide has proven itself as an enhancer so that a so-called basic immunization (three doses of the same inactivated vaccine within one year) provides years of protection (e.g. against TBE 3–5 years) to decades (e.g. against hepatitis A) granted. The relatively small amount of the killed pathogen used for a vaccination cannot stimulate the immune system as strongly as an infection with the reproducing pathogen. If, for safety reasons, vaccination is only carried out with killed pathogens or with parts of these pathogens, such an “inactivated vaccination” must be repeated several times until enough antibodies are formed for reliable protection. The aluminum hydroxide helps to reduce the number of individual vaccinations required for protection.
The average amount of aluminum (compounds) in vaccines is 125 to 850 µg per dose. In the EU, the maximum value allowed for a vaccination is 1250 µg per dose.
Risks
Looking for the cause of mysterious diseases ( english Gulf War illness ) many US troops to the Iraq war in 1991 has been tested in animal studies that used aluminum hydroxide adjuvant. A significant loss of 35% of the motor neurons in the spinal cord was found. At the same time, an unusual frequency of astrocytes was observed , their number increased by 350%. The authors of this work confirmed their own results two years later, whereby aluminum was discovered in the cytoplasm of the motor neurons by staining tests. In some neurons abnormal hyper was phosphorylation of tau protein found what also as a pathological hallmark for various neural diseases such as Alzheimer's disease and frontotemporal dementia is known.
In 2009, neuroscientists claimed that aluminum hydroxide in vaccines can cause side effects. The symptoms of the disease have been called macrophagic myofasciitis (MMF). A study examined patients mainly from France who suffered from this local muscle inflammation and postulated a connection to vaccinations with the additive aluminum hydroxide. A clear causal relationship between vaccines containing aluminum hydroxide and MMF could not be proven.
In November 2015, the German Paul Ehrlich Institute established that clinical studies and the spontaneous recording of side effects in Germany did not provide any evidence of aluminum-related toxicity after vaccinations. It found that the systemic exposure from the aluminum-containing vaccinations recommended in Germany in the first two years of life is in the range of tolerable intake through food. In addition, the contribution of vaccinations to the estimated lifelong net accumulation of aluminum in the organism is small compared to the continuous intake of aluminum from other sources and can be classified as justifiable in view of the benefits of vaccinations. There are no scientific analyzes that show that children or adults are at risk from vaccinations with aluminum-containing adjuvants.
Vaccines with aluminum salts as adjuvant (e.g. aluminum hydroxide or aluminum phosphate) have been used in vaccines for over 90 years. Despite the long observation period, the risk-benefit ratio is extremely positive; the dose administered even in infants or small children is far below the minimum risk limit. Adjuvants containing aluminum are not suspected of being carcinogenic or teratogenic . The safe limit concentration of Al-containing substances is 2 mg / kg per day, which means that the amount in vaccines is far below this limit, even if in that case they do not have to pass through the gastrointestinal tract as a natural barrier.
Serious side effects related to vaccinations have occurred. However, these occurred in people with certain underlying diseases (such as kidney dysfunction or immunodeficiency ) or with an above-average intake of substances containing aluminum. Common side effects sometimes include allergic reactions, but the most common are mild and short-lived: pain, itching, and redness at the injection site.
It is also discussed in the technical literature to substitute the aluminum-containing adjuvants contained in vaccines with calcium phosphates.
Individual evidence
- ↑ Entry on ALUMINUM HYDROXIDE in the CosIng database of the EU Commission, accessed on February 12, 2020.
- ↑ a b c d e f g h Entry on aluminum hydroxide in the GESTIS substance database of the IFA , accessed on December 19, 2019(JavaScript required) .
- ↑ Hank Hyena in Salon : “Dry sex” worsens AIDS numbers in southern Africa
- ^ Myron Essex: AIDS in Africa. Springer Science & Business Media, 2002, ISBN 0-306-46699-6 , p. 658 ( limited preview in Google book search).
- ↑ Bernard Bauschert: Background to the AIDS epidemic in Africa: Ndiri kutsvaga sauti - I'm looking for salt . In: Deutsches Ärzteblatt . tape 95 , no. 22 . Deutscher Ärzte-Verlag, May 29, 1998, p. A-1370 / B-1145 / C-1070 ( aerzteblatt.de ).
- ↑ Erika Jensen-Jarolim: Aluminum in Allergies and Allergen immunotherapy . In: The World Allergy Organization Journal . tape 8 , no. 1 , February 28, 2015, doi : 10.1186 / s40413-015-0060-5 , PMID 25780491 , PMC 4348159 (free full text).
- ^ Glenny AT, Pope CG, Waddington H, Wallace V. The antigenic value of toxoid precipitated by potassium alum. receptors control activation of adaptive immune responses. J Pathol Bacteriol 1926; 29: 38-45.
- ↑ WAVM : Impflexikon: Contents of vaccines. Scientific Academy for Preventive Medicine , 8010 Graz, accessed on July 26, 2012 (WAVM administers the free vaccination campaigns for children on behalf of the health department of the Styrian state government).
- ^ Stanley A. Plotkin et al .: Plotkin's Vaccines . 7th edition. Elsevier, 2017, ISBN 978-0-323-35761-6 , pp. 63 ( elsevier.com ).
- ↑ Armando A Paneque-Quevedo: Inorganic compounds as vaccine adjuvants . Ed .: Biotecnología Aplicada. tape 30 , no. 4 , 2013, ISSN 1027-2852 , p. 250–256 (English, sld.cu ).
- ^ A b Jean-Daniel Masson et al .: Calcium phosphate: a substitute for aluminum adjuvants? In: Expert Review of Vaccines . tape 16 , no. 3 , March 4, 2017, p. 289-299 , doi : 10.1080 / 14760584.2017.1244484 , PMID 27690701 .
- ↑ Nikolai Petrovsky, Julio César Aguilar: Vaccine adjuvants: Current state and future trends . In: Immunology and Cell Biology . tape 82 , no. 5 , September 28, 2004, p. 488-496 , doi : 10.1111 / j.0818-9641.2004.01272.x .
- ^ A b c Sabrina Fernandez: Aluminum in Vaccines: Addressing Parents' Concerns . In: Pediatric Annals . tape 45 , no. 7 , July 15, 2016, p. e231 – e233 , doi : 10.3928 / 00904481-20160606-01 ( healio.com ).
- ↑ a b c d Aleksandra Gołoś, Anna Lutyńska: Aluminum-adjuvanted vaccines - a review of the current state of knowledge . In: Przeglad Epidemiologiczny . tape 69 , no. 4 , 2015, p. 731-734, 871-874 , PMID 27139352 .
- ↑ MS Petrik et al .: Aluminum adjuvant linked to Gulf War illness induces motor neuron death in mice . In: Department of Ophthalmology and Program in Neuroscience, University of British Columbia (Ed.): Neuromolecular Med. Volume 9 , no. 1 . Vancouver, British Columbia, Canada 2007, p. 83-100 , PMID 17114826 .
- ↑ CA Shaw, MS Petrik: Aluminum hydroxide injections lead to motor deficits and motor neuron degeneration . In: Departments of Ophthalmology and Visual Sciences, University of British Columbia (Ed.): J Inorg Biochem. tape 103 , no. 11 . Vancouver, British Columbia, Canada November 2009, p. 1555–1562 , doi : 10.1016 / j.jinorgbio.2009.05.019 , PMID 19740540 , PMC 2819810 (free full text) - (Epub 2009 Aug 20).
- ↑ Frank L. Heppner, Hans-Hilmar Goebel, Rieke HE Alten: Vaccination safety today: Macrophage myofasciitis . In: Deutsches Ärzteblatt . tape 106 , no. 14 . Deutscher Ärzte-Verlag, April 3, 2009, p. 248 , doi : 10.3238 / arztebl.2009.0248a ( aerzteblatt.de ).
- ↑ Maurice Pich, Arno Köster, Andreas Klement: Vaccination safety today: Long-term vaccine side effects and pharmacovigilance . In: Deutsches Ärzteblatt . tape 106 , no. 14 . Deutscher Ärzte-Verlag, April 3, 2009, p. 248–249 , doi : 10.3238 / arztebl.2009.0248b ( aerzteblatt.de ).
- ↑ What is meant here is the postulated syndrome, not the local inflammatory changes
- ↑ Bulletin on drug safety - Bulletin on drug safety, issue 3 (PDF) BfArM, September 2015, p. 8 , accessed on April 1, 2020 .
- ↑ RK Gherardi et al .: Macrophagic myofasciitis lesions assess long-term persistence of vaccine-derived aluminum hydroxide in muscle . In: Brain . tape 124 , no. 9 . Universite Paris XII, France September 2001, p. 1821-1831 , PMID 11522584 .
- ^ Stanley A. Plotkin et al .: Plotkin's Vaccines . 7th edition. Elsevier, 2017, ISBN 978-0-323-35761-6 , pp. 66 ( elsevier.com ).
- ↑ Safety assessment of aluminum in vaccines. of the Paul Ehrlich Institute , November 3, 2015.
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology. 7th, completely revised and updated edition. Springer, Berlin et al. 2005, ISBN 3-540-23812-3 .
- Rakesh Bastola et al .: Vaccine adjuvants: smart components to boost the immune system . In: Archives of Pharmacal Research . tape 40 , no. 11 , November 2017, p. 1238-1248 , doi : 10.1007 / s12272-017-0969-z , PMID 29027637 .
- Nikolai Petrovsky: Comparative Safety of Vaccine Adjuvants: A Summary of Current Evidence and Future Needs . In: Drug Safety . tape 38 , no. 11 , November 2015, p. 1059-1074 , doi : 10.1007 / s40264-015-0350-4 , PMID 26446142 .
- Calvin C. Willhite et al .: Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts . In: Critical reviews in toxicology . tape 44 , Suppl 4, October 2014, p. 1–80 , doi : 10.3109 / 10408444.2014.934439 , PMID 25233067 , PMC 4997813 (free full text).
