Magnesium aluminate hydroxide

Magnesium aluminate spinels can be prepared(5-8) by various methods such as i) thermal co-condensation of oxides, ii) co-precipitation of hydroxides, and iii) co-gel formation. The results obtained from each of these procedures are briefly discussed below. 

Magnesium aluminate, the preferred support of one catalyst supplier, has a larger specific surface area. But this material must be calcined to a higher temperature during manufacture of the support particles to ensure it contains no free magnesium oxide, which would be hydrated to hydroxide at temperatures below 300 °C. This chemical change results in a volume increase, which would destroy the structure and impair the mechanical stability of the catalyst. 

Carbonato(2-))hexadecahydroxybis(aluminium)hexa-magnesium. (Carbonato(2-))hexadecahydroxybis(aluminium)hexa-magnesium Aluminate (Ai(OH)63-), (OC-6-11)-, magnesium carbonate hydroxide (2 6 1 4) EINECS 234-319-3 Magnesium, (carbonato 2-... 

Other effective antacids, which are used separately or with aluminum hydroxide or magnesium trisilicate, include dihydroxyaluminum amino-acetate, hydrated magnesium aluminate, dihydroxyaluminum sodium carbonate, and others. Each of these compounds has been demonstrated to be as useful as antacids but has not been so popular as calcium carbonate or aluminum hydroxide. 

To improve magnesium reduction, which also improves siHca reduction in cold process softening, sodium aluminate may be used. The sodium aluminate provides hydroxyl ion (OH ) needed for improved magnesium reduction, without increasing calcium hardness in the treated water. In addition, the hydrolysis of sodium aluminate results in the formation of aluminum hydroxide, which aids in floe formation, sludge blanket conditioning, and siHca reduction. 

A large number of electrolytic treatments of magnesium, anodic or a.c., have been developed, in which adherent white or grey films consisting of fluoride, oxide, hydroxide, aluminate or basic carbonate are deposited from alkaline solutions containing caustic alkali, alkali carbonates, phosphates, pyrophosphates, cyanides, aluminates, oxalates, silicates, borates, etc. Some films are thin, and some are relatively thick. All are more or less absorbent and act as good bases for paint, though none contributes appreciable inhibition. All can, however, absorb chromates with consequent improvement of protective efficiency. 

The coagulant sodium aluminate (NaA102) is strongly caustic (contributing hydroxide alkalinity to the BW) and reacts with calcium and magnesium salts and any silica present to form a zeolite sludge of calcium-magnesium-aluminum silcate. 

In this method, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, or sodium aluminate can be fed to the spent fixer for precipitation of silver ions as insoluble silver hydroxide precipitates. Figure 7 indicates that the residual silver concentration in the hydroxide precipitation treated effluent can be about 1 mg/L at pH 12 [19]. 

The removal of other species requires the addition of sodium aluminate (Na2Al204). Reduction in the concentration magnesium is only about 10%. The addition of sodium aluminate also helps with the reduction in silica, as the magnesium precipitate, magnesium hydroxide, adsorbs silica. More complete removal requires the addition of soda ash (Na2C03) and warmer temperatures, as shown in Table 8.10. 

Electrolytes which do not afford ionic complexes with common hexitols and reducing sugars are aqueous solutions of lead acetate, copper sulfate, zinc sulfate, ferrous ammonium sulfate, calcium chloride, potassium dichromate, ferric chloride (pH 3), aluminum sulfate, magnesium sulfate, sodium sulfate, potassium antimonyl tartrate, sodium arsenate or arsenic acid, sodium phosphate, and hydrochloric acid. It is not certain whether sodium aluminate (in 0.1 N sodium hydroxide) affords ionic complexes with carbohydrates, as aqueous alkali, alone, permits their migration during electrophoresis. 

Typical values for mjn are 0.5 to 2.5. Commercially used bases include sodium hydroxide, potassium hydroxide, calcium hydroxide (lime), magnesium hydroxide, sodium carbonate, sodium aluminate, calcium carbonate, or various mixtures. For certain applications, PAC can be made from waste grades of aluminum chloride [7446-70-0] such as spent catalyst solutions from Friedel-Crafts synthesis (see Friedel-Crafts REACTION). 

Fluoride can be precipitated by lime as the calcium salt. At pH 10, the residual level is in the range 10 to 20 mg/1 (as F) [28.2]. The precipitate should be removed by adsorption on magnesium hydroxide, calcium phosphate, or activated alumina, but not on aluminium hydroxide, as alum and aluminate form a soluble complex with fluoride. 

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