Aluminas aluminum hydroxides

Tonerde-hydrat, n. hydrate of alumina (aluminum hydroxide). -kali, n. potassium aluminate. -lack, m. alumina lake. -metaU, n. aluminum, -natron, n. sodium aluminate. -prMparat, n. alumina preparation, tonerderelch, a, rich in alumina, aluminous. Tonerde-galz, n. aluminum salt, -stein, m, alumina brick, -sulfat, n, sulfate of alumina... 

Pulmonary fibrosis is the most commonly reported respiratory effect observed in workers exposed to fine aluminum dust (pyropowder), alumina (aluminum hydroxide), or bauxite. However, conflicting reports are available on the fibrogenic potential of aluminum. In some of the cases, the fibrosis was attributed to concomitant exposure to other chemicals. For example, pulmonary fibrosis has been observed in a number of bauxite workers (Devuyst et al. 1986 Gaffuri et al. 1985 Jephcott 1948 Musk et al. 1980 Riddell 1948 Shaver 1948) in these workers, it is very likely that there was simultaneous exposure to silica and that the latter was the causative agent rather than the aluminum. Some of the earliest cases of pulmonary fibrosis were reported in German munition workers exposed to pyropowder. 

Alumina Aluminum hydroxide Attapulgite Carbon, activated Magnesium phosphate tri basic... 

Alumina Aluminum hydroxide Aluminum silicate Aminotrimethylene phosphonic acid Asbestos... 

Alumina Aluminum hydroxide Attapulgite Bone black Coke... 

Alumina Aluminum hydroxide Calcium oxide Calcium sulfite Gallic acid Magnesium chloride Magnesium oxide PEG-90M PEG-160M Potassium alum dodecahydrate... 

For poly(cyanoaryl ether)s, suitable nucleating agents are alumina, aluminum hydroxide, aluminum powder, titanium dioxide and calcium fluoride. In contrast, kaolin, talc, mica, silica, calcium carbonate, a metal salt of an aliphatic acid, etc., which are frequently used for poly(ester)s, exhibit no effective action upon the crystallization of a polyfcyanoaryl ether) (13). 

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

The aluminum containing compound having the largest worldwide market, estimated to be over 30 x 10 t in 1990, is metal grade alumina. Second, is aluminum hydroxide. In 1990 the market for Al(OH)2 should approach or exceed 3.5 million metric tons which is equivalent to 2.3 million tons on an alumina basis. The spHt between additive and feedstock appHcations for Al(OH)2 (16) is roughly 50 50. Additive appHcations include those as flame retardants (qv) in products such as carpets, and to enhance the properties of paper (qv), plastic, polymer, and mbber products. Significant quantities are also used in pharmaceuticals (qv), cosmetics (qv), adhesives (qv), poHshes (qv), dentifrices (qv), and glass (qv). 

Aluminum sulfate has largely replaced alums for the major appHcations as a sizing agent in the paper industry and as a coagulant to clarify municipal and industrial water suppHes. In terms of worldwide production, it ranks third behind alumina and aluminum hydroxide, with markets in excess of 3 x 10 t/yr (19). 

The activated aluminas comprise a senes of nonequilibrium forms of partially hydroxylated aluminum oxide [1344-28-1], AI2O2. The chemical composition can be represented by Al20 2 ranges from about 0 to 0.8. They are porous soHds made by thermal treatment of aluminum hydroxide... 

The large majority of activated alumina products are derived from activation of aluminum hydroxide, rehydrated alumina, or pseudoboehmite gel. Other commerical methods to produce specialty activated aluminas are roasting of aluminum chloride [7446-70-0], AIQ calcination of precursors such as ammonium alum [7784-25-0], AlH2NOgS2. Processing is tailored to optimize one or more of the product properties such as surface area, purity, pore size distribution, particle size, shape, or strength. 

Rehydration Bonded Alumina. Rehydration bonded aluminas are agglomerates of activated alumina, which derive their strength from the rehydration bonding mechanism. Because more processing steps are involved in the manufacture, they are generally more expensive than activated aluminum hydroxides. On the other hand, rehydration bonded aluminas can be produced in a wider range of particle shape, surface area, and pore size distribution. 

The term alumina hydrates or hydrated aluminas is used in industry and commerce to designate aluminum hydroxides. These compounds are tme hydroxides and do not contain water of hydration. Several forms are known a general classification is shown in Figure 1. The most weU-defined crystalline forms ate the trihydroxides, Al(OH) gibbsite [14762-49-3], bayerite [20257-20-9], and nordstrandite [13840-05-6], In addition, two aluminum oxide—hydroxides, AIO(OH), boelimite [1318-23-6] and diaspote [14457-84-2], have been clearly defined. The existence of several other forms of aluminum hydroxides have been claimed. However, there is controversy as to whether they ate truly new phases or stmctures having distorted lattices containing adsorbed or intedameUar water and impurities. 

Low Soda Hydroxide. Tlie Na20 content of nomial Bayer hydroxide is around 0.2—0.4%, 0.1% of wliich can be removed by thorough wasliing. Tlie remaining soda is trapped within the hydroxide crystal. Experience shows that the occluded soda content is reduced when cry staUization is carried out under low aluniina-supersaturation conditions and at relatively higher temperatures (80—95°C). Soda contents as low as 0.05% Na20 can be obtained by tliis procedure. However, these conditions also reduce hydroxide ield and thus increase the production cost. Low soda aluminum hydroxide is generally employed in the production of aluminas for the ceramics industries. 

Bayer aluminum hydroxides in most grades are sold by all major U.S. alumina producers. Other firms offering aluminum hydroxide fillers probably operate reprocessing faciHties to grind or otherwise treat hydroxide obtained from the primary producers. Countries exporting small amounts to the United States are Japan, Germany, Canada, and the UK. 

Alumina—A white, odorless, tasteless, amorphous powder consisting essentially of aluminum hydroxide, AI2O2 xH20 (see Aluminum compounds, ALUMINUM oxide). 

The small (10 -lm) coating particles are typically aluminum oxide [1344-28-1/, Al O. These particles can have BET surface areas of 100 to 300 m /g. The thermal and physical properties of alumina crystalline phases vary according to the starting phase (aluminum hydroxide or hydrate) and thermal treatment (see ALUMINUM COMPOUNDS, ALUMINUM OXIDE). 

Alumina (AfOf. Alumina is produced by calcining either bauxite or aluminum hydroxide in rotary Idlns at temperatures from 1250 to 1600 K. In obtaining the highest-purity alumina, the bauxite is digested with alkah to remove impurities the resultant aluminum hydroxide [AlgfOH) ], of approximately 200-mesh size, is then calcined in rotaiy Idlns at 1350 K. 

The results of development work on processes indicate that the two main methods of preventing the duplex microstructure from forming appear to be fast-firing, or increasing the amount of / "-alumina at low temperatures. Based on these results, Duncan et al. [20] and Zyl et al. [21] have described production processes starting from aluminum oxy-hydroxides or aluminum hydroxides as precursors for the synthesis of the solid electrolyte "-alumina. Duncan et al. described an alumina precursor which substitutes in part or wholly for or-alumina in an established... 

Aluminum Oxide (Alumina, oAlumina, Corundum, Alandum). A1203, mw 101.96, v hard white cryst powd, mp 2045°, bp 2980°, d 3.965g/cc. Insol in w, v si sol in aq alkaline solns. Found in nature as a mineral such as bauxite. Lab prepn is by heating aluminum hydroxide to above 1100°. 

Aluminum is the most abundant metallic element in the Earth s crust and, after oxygen and silicon, the third most abundant element (see Fig. 14.1). However, the aluminum content in most minerals is low, and the commercial source of aluminum, bauxite, is a hydrated, impure oxide, Al203-xH20, where x can range from 1 to 3. Bauxite ore, which is red from the iron oxides that it contains (Fig. 14.23), is processed to obtain alumina, A1203, in the Bayer process. In this process, the ore is first treated with aqueous sodium hydroxide, which dissolves the amphoteric alumina as the aluminate ion, Al(OH)4 (aq). Carbon dioxide is then bubbled through the solution to remove OH ions as HCO and to convert some of the aluminate ions into aluminum hydroxide, which precipitates. The aluminum hydroxide is removed and dehydrated to the oxide by heating to 1200°C. 

In the flowsheet of alumina production by the Bayer process, aluminum is precipitated from an aqueous solution as aluminum hydroxide. The hydroxide is dried in rotary furnaces. In recent times, fluidized-bed reactors have been deployed which yield practically nonhygroscopic alumina. The dissociation of aluminum hydroxide occurs in steps,... 

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