Aluminum Digest

The metal may he analyzed hy atomic absorption or emission spectrophotometry (at trace levels). Other techniques include X-ray diffraction, neutron activation analysis, and various colorimetric methods. Aluminum digested with nitric acid reacts with pyrocatechol violet or Eriochrome cyanide R dye to form a colored complex, the absorbance of which may be measured by a spectrophotometer at 535 nm. 

Allain P, Gauchard F, Krari N. 1996. Enhancement of aluminum digestive absorption by fluoride in rats. Res Commun Mol Pathol Pharmacol 91 225-231. 

Aluminum Digest Rohm and Haas Reporter Amber-hi-Lites Scientific Apparatus and Methods Lubrication Vancoram Review Chlorination Topics Wallerstein Laboratories Communications Taste and Odor Control Journal... 

In 1990, appioximately 66,000 metric tons of alumina trihydiate [12252-70-9] AI2O2 3H20, the most widely used flame retardant, was used to inhibit the flammabihty of plastics processed at low temperatures. Alumina trihydrate is manufactured from either bauxite ore or recovered aluminum by either the Bayer or sinter processes (25). In the Bayer process, the bauxite ore is digested in a caustic solution, then filtered to remove siUcate, titanate, and iron impurities. The alumina trihydrate is recovered from the filtered solution by precipitation. In the sinter process the aluminum is leached from the ore using a solution of soda and lime from which pure alumina trihydrate is recovered (see Aluminum compounds). 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

A.lkaline Solutions. The most important example of alkaline leach is the digestion of hydrated alumina from bauxite by a sodium hydroxide solution at 160-170°C, ie, the Bayer process (see Aluminumand aluminum alloys). 

Commercial grades of sodium aluminate are obtained by digestion of aluminum tnhydroxide in aqueous caustic at atmospheric pressure and near the boiling temperature (7). Digestion of the aluminum hydroxy oxide in aqueous sodium hycboxide [1310-73-2] requbes pressures of up to 1.38 MPa (13.6 atm) and temperatures of about 200°C. Dry sodium aluminate is obtained by evaporation of water. Several processes for the production of sodium aluminate are known that do not reqube the addition of water. In one process, bauxite reacts with molten sodium hycboxide at approximately 400°C (8) in... 

Purification. Alumina, AI2O3, is produced by the Bayer process (1,9) (see Aluminum COMPOUNDS) which involves digestion foUowed by precipitation and calcination. High purity magnesia is extracted from natural brines and seawater by precipitation and calcination (1,9). 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

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. 

At the alumina plant, the bauxite ore is further crushed to the correct particle size for efficient extraction of the alumina through digestion by hot sodium hydroxide liquor. After removal of "red mud" (the insoluble part of the bauxite) and fine solids from the process liquor, aluminum trihydrate crystals are precipitated and calcined in rotary kilns or fluidized bed calciners to produce alumina (AljOj). Some alumina processes include a liquor purification step. 

The dry tosylhydrazone (20 g, 45.5 mmol) is dissolved in 750 ml of 1,2-dimethoxyethane (freshly distilled from lithium aluminum hydride) in a flame-dried 1 liter round bottom flask fitted with a 240 ml addition funnel, a drierite tube and a magnetic stirrer. A 2.05 M ether solution of methyllithium (130 ml, Alfa Inorganics, Inc.—Caution to avoid the mineral oil impurity the methyllithium solution is decanted from a cold solution which contains a precipitate) is placed in the dropping funnel and added over a 60 min period. The temperature of the reaction mixture increases to ca. 35° during the addition however, no cooling precautions are required. The highly colored reaction mixture is stirred for 7 hr and then poured into 1.5 liters of ice water. The flocculent precipitate is digested for 12 hr at room temperature to speed the filtration. After filtration the filter cake is washed with 500 ml water and dried under vacuum at 50° for several hr. The androsta-5,16-dien-3l5-ol is obtained in ca. 70% yield after recrystallization from methanol mp 138-139°. 

There are problems as well in the absorption of certain drugs in the presence of specific food components. L-Dopa absorption may be inhibited in the presence of certain amino acids formed from the digestion of proteins [43], The absorption of tetracycline is reduced by calcium salts present in dairy foods and by several other cations, including magnesium and aluminum [115-117], which are often present in antacid preparations. In addition, iron and zinc have been shown to reduce tetracycline absorption [118], Figure 17 illustrates several of these interactions. These cations react with tetracycline to form a water-in-soluble and nonabsorbable complex. Obviously, these offending materials should not be co-administered with tetracycline antibiotics. 

Bayer A process for making pure alumina hydrate from bauxite, used principally as a raw material for the manufacture of aluminum metal. The ore is digested with hot sodium hydroxide solution, yielding a solution of sodium aluminate. Insoluble impurities are separated off in the form of red mud and the solution is then nucleated with alumina hydrate from a previous batch, causing alumina trihydrate to precipitate ... 

Bretsznajder A process for extracting aluminum from clays and a variety of aluminous wastes by continuous digestion with concentrated sulfuric acid in an autoclave. Developed in Poland in the 1980s but not yet commercialized. 

The product was digested with warm water, which dissolved the sodium aluminate and left the other materials as an insoluble residue. Passage of carbon dioxide through the clarified liquor precipitated aluminum as hydroxide ... 

Nuvalon A development of the Aloton process for extracting aluminum from clay. As in the Aloton process, clay is first heated with ammonium hydrogen sulfate. In the Nuvalon version, the product from this reaction is digested under pressure with 30 percent nitric acid, producing a solution of basic aluminum nitrate. Iron is removed by hydrolysis or by cooling. 

Aluminum is a metal which exists abundantly and widely in the earth and is commonly used in food packaging, antiperspirants, antiacid in digestion remedies, cosmetics and in beverages industries [2]. Aluminum sulfate is the most common aluminum-based coagulant used in purify water in many countries and it is found in most drinking water. WHO guidelines set its permissible level in drinking water at 200 ppb [3]. Upper levels can lead to serious problems such as Alzeheimer s disease. So, optimized preconcentration methods are required for the determination of trace amounts aluminum. 

In addition, a dealumlnated mordenlte was prepared by leaching HM-10 with 0.4 mol dm HCl solution at 323 K for 30 hr. After washing with distilled water, this was treated In a sodium acetate solution at 353 K for 20 hr for the Ion-exchange. The resulting composition of aluminum was measured by Inductively coupled plasma (ICP) emission spectroscopy after digestion In HF. 

CS028 Lancaster, L. A. and B. Rajadurai. An automated procedure for the determination of aluminum in soil and plant digest. J Sci Food Agr 1974 25 381. 

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