Difference between revisions of "Aluminium hydroxide"
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Latest revision as of 15:49, 27 September 2010
| Aluminium hydroxide | |
|---|---|
| File:Gibbsite-crystal-3D-balls.png | |
| File:Hydroxid hlinitý.PNG | |
| Aluminium hydroxide | |
| Other names Aluminium(III) hydroxide, Hydrated alumina | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 21645-51-2 
|
| ChemSpider | 8351587 |
| RTECS number | BD0940000 |
| SMILES | Script error: No such module "collapsible list". |
| InChI | Script error: No such module "collapsible list". |
| InChI key | WNROFYMDJYEPJX-DFZHHIFOAJ |
| style="background: #F8EABA; text-align: center;" colspan="2" | Properties | |
| Molecular formula | Al(OH)3 |
| Molar mass | 78.00 g/mol |
| Appearance | White amorphous powder |
| Density | 2.42 g/cm³, solid |
| Melting point |
300 °C, 573 K, 572 °F |
| Solubility in water | 0.0001 g/100 mL (20 °C) |
| Solubility | soluble in acids, alkalis, HCl, H2SO4 |
| Acidity (pKa) | >7 |
| style="background: #F8EABA; text-align: center;" colspan="2" | Hazards | |
| MSDS | External MSDS |
| EU classification | Irritant (I) Xi |
| R-phrases | R36 R37 R38 |
| S-phrases | S26 S36 |
| NFPA 704 | |
| Flash point | Non-flammable |
| style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds | |
| Other anions | None |
| Related compounds | Sodium oxide, aluminium oxide hydroxide |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Aluminium hydroxide, Al(OH)3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide, Al2O3, differing only by loss of water. These compounds together are the major components of the aluminium ore bauxite. Freshly precipitated aluminium hydroxide forms gels, which is the basis for application of aluminium salts as flocculants in water purification. This gel crystallizes with time. Aluminium hydroxide gels can be dehydrated (e.g., with the utility of water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminium hydroxide powder, which is readily soluble in acids. Aluminium hydroxide powder which has been heated to an elevated temperature under carefully controlled conditions is known as activated alumina and is used as a desiccant, an adsorbent, in gas purification, as a Claus catalyst support, water purification, and an adsorbent for the catalyst during the manufacture of polyethylene by the Sclairtech process.
Contents
Chemistry
Gibbsite has a typical metal hydroxide structure with hydrogen bonds. It is built up of double layers of hydroxyl groups with aluminium ions occupying two-thirds of the octahedral holes between the two layers.[1]
Aluminium hydroxide is amphoteric. It dissolves in acid, forming Al(H2O)63+ (hexaaquaaluminate) or its hydrolysis products. It also dissolves in strong alkali, forming Al(OH)4- (tetrahydroxoaluminate).
Production
Virtually all the aluminium hydroxide used commercially is manufactured by the Bayer process which involves dissolving bauxite in sodium hydroxide as the first step. It is marketed as Alu-Tabs.
Uses
Annual production is some 100 million tonnes, over 90% of which is converted to aluminium oxide (alumina) which is used in the manufacture of aluminium metal.
The major other uses of aluminium hydroxide is as a feedstock for the manufacture of other aluminium compounds: specialty calcined aluminas, aluminium sulfate, polyaluminium chloride, aluminium chloride, zeolites, sodium aluminate, activated alumina, aluminium nitrate.
Use as a fire retardant
Aluminium hydroxide also finds use as a fire retardant filler for polymer applications in a similar way to magnesium hydroxide and hydromagnesite. It decomposes at about 180 °C, absorbing a considerable amount of heat in the process and giving off water vapour. In addition to behaving as a fire retardant, it is very effective as a smoke suppressant in a wide range of polymers, most especially in polyesters, acrylics, ethylene vinyl acetate, epoxies, PVC, rubber.
Pharmacology
Pharmacologically, this compound is used as an antacid under names such as Alu-Cap, Aludrox or Pepsamar. The hydroxide reacts with excess acid in the stomach, reducing its acidity.[2] This decrease of acidity of the contents of the stomach may in turn help to relieve the symptoms of ulcers, heartburn or dyspepsia. It can also cause constipation and is therefore often used with magnesium hydroxide or magnesium carbonate, which have counterbalancing laxative effects. This compound is also used to control phosphate (phosphorus) levels in the blood of people suffering from kidney failure.
Aluminium hydroxide is included as an adjuvant in some vaccines (e.g., Alhydrogel, Anthrax Vaccine), since it appears to contribute to induction of a good antibody (Th2) response. Its pharmacological action is not known. However, it has little capacity to stimulate cellular (Th1) immune responses, important for protection against many pathogens.[3]
Because the brain lesions found in Alzheimer's disease sometimes contain traces of aluminium, there is concern that consumption of excess aluminium compounds may cause or contribute to the development of this and other neurodegenerative diseases.[4][5] However, multiple epidemiological studies have found no connection between exposure to aluminium and neurological disorders.[6][7][8]
In addition, elevated aluminium levels in blood, resulting from kidney dialysis with well water containing high aluminium, may result in dementia that is similar to but probably different from that of Alzheimer's disease.[9]. However, this hypothesis is controversial.
In 2007, tests with mice of the anthrax vaccine using aluminium hydroxide adjuvant were reported as resulting in adverse neuropathy symptoms.[10]
References
- ↑ A. F. Wells, Structural Inorganic Chemistry, 4th. edition 1975, Oxford University Press.
- ↑ Galbraith, A; Bullock, S; Manias, E. Hunt, B. & Richards, A. (1999). Fundamentals of pharmacology: a text for nurses and health professionals. Harlow: Pearson. p. 482.
- ↑ Petrovsky N, Aguilar JC. (2004). "Vaccine adjuvants: current state and future trends". Immunol Cell Biol. 82 (5): 488–96. doi:10.1111/j.0818-9641.2004.01272.x. PMID 15479434.
- ↑ Perl DP, Moalem S (2006). "Aluminum and Alzheimer's disease, a personal perspective after 25 years". J. Alzheimers Dis. 9 (3 Suppl): 291–300. PMID 17004365.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Rondeau V (2002). "A review of epidemiologic studies on aluminum and silica in relation to Alzheimer's disease and associated disorders". Rev Environ Health. 17 (2): 107–21. PMID 12222737.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
- ↑ Carpenter DO (2001). "Effects of metals on the nervous system of humans and animals". Int J Occup Med Environ Health. 14 (3): 209–18. PMID 11764847.
- ↑ Petrik MS, Wong MC, Tabata RC, Garry RF, Shaw CA. (2007). "Aluminum adjuvant linked to Gulf War illness induces motor neuron death in mice". Neuromolecular Med. 9 (9): 83–100. doi:10.1385/NMM:9:1:83.
External links
ar:هيدروكسيد الألومنيومca:Hidròxid d'alumini cs:Hydroxid hlinitý de:Aluminiumhydroxid es:Hidróxido de aluminio fa:آلومینیم هیدروکسید fr:Hydroxyde d'aluminium gl:Hidróxido de aluminio it:Idrossido di alluminio lv:Alumīnija hidroksīdi hu:Alumínium-hidroxid nl:Aluminiumhydroxide ja:水酸化アルミニウム pl:Wodorotlenek glinu pt:Hidróxido de alumínio ro:Hidroxid de aluminiu ru:Гидроксид алюминия sk:Hydroxid hlinitý sr:Алуминијум хидроксид fi:Alumiinihydroksidi sv:Aluminiumhydroxid th:อะลูมิเนียมไฮดรอกไซด์ uk:Гідроксид алюмінію zh:氢氧化铝
