General Description
White odorless crystalline powder. Water insoluble. Properties (both physical and chemical) vary according to the method of preparation; different methods give different crystalline modifications. The variety formed at very high temperature is quite inert chemically.
Reactivity Profile
ALUMINUM OXIDE(1344-28-1) is chemically amphoteric (behaves as a weak acid in the presence of base and as a weak base in the presence of acid). May act catalytically. May cause the exothermic polymerization of ethylene oxide. May cause the vigorous polymerization of vinyl chloride [MCA SD-75, 1970]. The degree of subdivision of the ALUMINUM OXIDE(1344-28-1) may affect the vigor of such reactions.
Air & Water Reactions
Insoluble in water.
Hazard
Toxic by inhalation of dust. Confirmed car-
cinogen.
Potential Exposure
Most hazardous exposures to aluminum occur in smelting and refining processes. Aluminum is mostly produced by electrolysis of Al2O3 dissolved in molten cryolite (Na3AlF6). Aluminum is alloyed with copper, zinc, silicon, magnesium, manganese, and nickel; special additives may include chromium, lead, bismuth, titanium, zirconium, and vanadium. Aluminum and its alloys can be extruded or processed in rolling mills, wire works, forges, or foundries; and are used in the shipbuilding, electrical, building, aircraft, automobile, light engineering, and jewelry industries. Aluminum foil is widely used in packaging. Powdered aluminum is used in the paints and pyrotechnic industries. Alumina, emery, and corundum has been used for abrasives, refractories, and catalysts; and in the past in the first firing of china and pottery.
First aid
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.
Shipping
UN1309 Aluminum powder, coated, Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN1383 Pyrophoric metals, n.o.s. or Pyrophoric alloys, n.o.s., Hazard Class: 4.2; Labels: 4.2-Spontaneously combustible material, Technical Name Required. UN1396 Aluminum powder, uncoated, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material. NA9260 (North America) Aluminum, molten, Hazard class: 9; Labels: 9-Miscellaneous hazardous material.
Incompatibilities
Aluminum powder forms an explosive mixture with air and is a strong reducing agent that reacts violently with oxidizers, strong bases; strong acids; somehalogenated hydrocarbons; nitrates, sulfates, metal oxides and many other substances. Keep away from combustible materials.
Chemical Properties
Aluminum is a combustible, light, silverywhite, soft, ductile, malleable, amphoteric metal.Vary according to the method of preparation. White powder, balls, or lumps of various mesh.Insoluble in water, dif- ficultly soluble in mineral acids and strong alkali. Noncombustible.
Chemical Properties
Aluminum oxide occurs as a white crystalline powder. Aluminum
oxide occurs as two crystalline forms: α-aluminum oxide is
composed of colorless hexagonal crystals, and γ-aluminum oxide
is composed of minute colorless cubic crystals that are transformed
to the α-form at high temperatures.
Waste Disposal
Consult with environmental regulatory agencies for guidance on acceptable disposalpractices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal of Aluminum Oxide-Disposal in a sanitary landfill. Mixing of industrial process wastes and municipal wastes at such sites is not encouraged however. Aluminum powder may be recovered and sold as scrap. Recycling and recovery is a viable option to disposal for aluminum metal and aluminum fluoride (A-57).
Occurrence
Occurs in nature in abundance; the principal forms are bauxites and laterites. The mineral corundum is used to produce precious gems, such as ruby and sapphire. Activated aluminas are used extensively as adsorbents because of their affinity for water and other polar molecules; and as catalysts because of their large surface area and appropriate pore sturcture. As adsorbents, they are used for drying gases and liquids; and in adsorption chromatography. Catalytic properties may be attributed to the presence of surface active sites (primarily OH- , O2- , and Al3+ ions). Such catalytic applications include sulfur recovery from H2S (Clauss catalysis); dehydration of alcohols, isomerization of olefins; and as a catalyst support in petroleum refining.
Characteristics
Aluminum Oxide (Alumina) is the most widely used oxide, chiefly because it is plentiful, relatively low in cost, and equal to or better than most oxides in mechanical properties. Density can be varied over a wide range, as can purity — down to about 90% alumina — to meet specific application requirements. Alumina ceramics are the hardest, strongest, and stiffest of the oxides. They are also outstanding in electrical resistivity, dielectric strength, are resistant to a wide variety of chemicals, and are unaffected by air, water vapor, and sulfurous atmospheres. However, with a melting point of only 2039°C, they are relatively low in refractoriness, and at 1371°C retain only about 10% of room-temperature strength. In addition to its wide use as electrical insulators and its chemical and aerospace applications, the high hardness and close dimensional tolerance capability of alumina make this ceramic suitable for such abrasion-resistant parts as textile guides, pump plungers, chute linings, discharge orifices, dies, and bearings.
Production Methods
The Bayer process begins by grinding the bauxite and mixing it with sodium hydroxide in a digester. The sodium hydroxide dissolves aluminum oxide components to produce aluminum hydroxide compounds. For gibbsite, the reaction is: Al(OH)3 + NaOH → Al(OH)4- + Na+. Insoluble impurities such as silicates, titanium oxides, and iron oxides are removed from the solution while sodium hydroxide is recovered and recycled. Reaction conditions are then modified so that aluminum trihydroxide (Al(OH)3) precipitates out. The reaction can be represented as the reverse of the previous reaction: Al(OH)4- + Na+ → Al(OH)3 + NaOH. Aluminum trihydroxide is calcined to drive off water to produce alumina:
Al(OH)3 Al2O3 + 3H2O.
Health Hazard
The aluminas are considered to
be nuisance dusts; their role in fibrogenic lung
disease remains unclear.
Assessment of the toxicity of aluminas has
been complicated by the chemical and physical
variants of the compounds and inconsistencies
in the nomenclature used to describe them.1
The group of compounds referred to as aluminas
is composed of various structural forms of
aluminum oxide, trihydroxide, and oxyhydroxide.
2 As these aluminas are heated, dehydration
occurs, producing a variety of transitional
forms; temperatures between 200 and 500°C
result in low-temperature-range transitional aluminas characterized by increased catalytic
activity and larger surface area.(Transitional
aluminas include c, h, and g forms, which,
taken together, were formerly termed “g.”)
Flammability and Explosibility
Notclassified
Pharmaceutical Applications
Aluminum oxide is used mainly in tablet formulations.It is used
for decoloring powders and is particularly widely used in antibiotic
formulations. It is also used in suppositories, pessaries, and urethral
inserts. Hydrated aluminum oxide is used in
mordant dyeing to make lake pigments, in cosmetics, and
therapeutically as an antacid.
Industrial uses
Fused aluminum oxide was the second synthetic abrasive to be developed. Synthetic aluminum oxide (alumina) is made as a white powder and can be somewhat harder than corundum (natural alumina) because of its purity. However, corundum has a Mohs hardness of approximately 9 (on a scale of 1 to 10. Alumina can be processed with different properties by slight alteration of the reactants in the manufacturing process. Several grain sizes of alumina are available, and alumina has largely replaced emery for several abrasive uses. Aluminum oxide is widely used to make bonded abrasives, coated abrasives, and air-propelled grit abrasives for dental applications.
Sintered aluminum oxide is used to make white stones, which are popular for adjusting dental enamel and finishing metal alloys, resin-based composites, and ceramic materials.
Pink and ruby variations of aluminum oxide abrasives are made by adding chromium compounds to the original melt. These variations are sold in a vitreous-bonded form as noncontaminating mounted stones for the preparation of metal– ceramic alloys to receive porcelain. Remnants of these abrasives and other debris should be removed from the surface of metals used for metal–ceramic bonding so as not to prevent optimal bonding of porcelain to the metal alloy. A review by Yamamoto (see Selected Reading) suggests that carbide burs are the most effective instruments for finishing this type of alloy because they do not contaminate the metal surface with entrapped abrasive particles.
storage
Aluminum oxide should be stored in a well-closed container in a
cool, dry, place. It is very hygroscopic.
Purification Methods
Stir the oxide with hot 2M HNO3, either on a steam bath for 12hours (changing the acid every hour) or three times for 30minutes, then wash it with hot distilled water until the washings have pH 4, and follow by three washings with hot MeOH. The product is dried at 270o [Angyal & Young J Am Chem Soc 81 5251 1959]. For the preparation of alumina for chromatography see Chapter 1. [For , and Al2O3 see Becher in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 822-823 1963 and Wagner in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1662 1965.]
Regulatory Status
Included in the FDA Inactive Ingredients Database (oral tablets and
topical sponge). Included in nonparenteral medicines licensed in the
UK.
;