Aluminum retention

Interactions of Metal Salts with the Formation. Interactions of metal salts with the formation and distribution of the retained aluminum in a porous medium may significantly affect the location and strength of gels. This interaction was demonstrated with polyacrylamide-aluminum citrate gels [1514]. Solutions were displaced in silica sand. The major findings of this study are that as the aluminum-to-citrate ratio increases, the aluminum retention increases. Furthermore, the amount of aluminum retained by silica sand increases as the displacing rate decreases. The process is reversible, but the aluminum release rate is considerably slower than the retention rate. The amount of aluminum released is influenced by the type and the pH level of the flowing solution. The citrate ions are retained by silica sand primarily as a part of the aluminum citrate complex. Iron, cations, and some divalent cations cannot be used in the brine environment. 

Several animal studies have examined potential age-related differences in the distribution, neurotoxicity, skeletal toxicity, and interactions of aluminum. However, conflicting results have been found and the database is not adequate to assess whether these differences are due to the animal species tested, the aluminum compound used, or the route of exposure. Additionally, there are no studies on the influence of immature renal function on aluminum retention in the body and no studies on the long-term effects of aluminum exposure on skeletal maturation or neurotoxicity. Multiple species studies examining a wide range of effects in immature, mature, and older animals would be useful in assessing the children s susceptibility to the toxicity of aluminum. 

Ecelbarger CA, MacNeil GG, Greger JL. 1994b. Aluminum retention by aged rats fed aluminum and treated with desferrioxamine. Toxicol Lett 73 249-257. 

Gomez M, Sanchez DJ, Llobet JM, et al. 1997a. The effect of age on aluminum retention in rats. Toxicology 116 1-8. 

Sakhaee K, Wabner CL, Zerwekh JE, et al. 1993. Calcium citrate without aluminum antacids does not cause aluminum retention in patients with functioning kidneys. Bone Mineral 20 87-97. 

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). 

The amount of herbicide sorbed by a given soil is influenced by properties of both the soil and the herbicide. Important properties related to the soil s retention abiHty include clay mineralogy, organic matter content, soil pH, and iron and aluminum oxide content. These properties, in turn, affect the... 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

Cross-linked polyester composites have a relatively low coefficient of thermal conductivity that can provide beneficial property retention in thick laminates at high temperatures as well as remove the need for secondary insulation. The coefficient of thermal expansion of glass-reinforced composites is similar to aluminum but higher than most common metals. 

Replacement of an unactivated lone chlonne with hydrogen is also accom-phshed in good yield with lithium aluminum hydride. Chlorofluoronorcaranes are selectively dechlormated to give hydro derivatives, largely with retention of configuration The related monodeutcronorcaranes are prepared with lithium aluminum deutende [27] (equations 20a and 20b). 

Modification of the ketonic side chain is also consistent with retention of analgesic activity. Thus, reduction of methadone with lithium aluminum hydride affords the alcohol, 128 (apparently as a single diastereomer). Acetylation gives acetyl-methadol (129). ... 

Table VI. Effect of Air and Aluminum on SO2 Retention of Wines Stored in Double-Enameled Aluminum Cans0...

Analysis and purification of the product solution is best accomplished by gas chromatography. The submitters used a 500 cm. by 0.6 cm. aluminum or polyethylene column packed with 21% oxydipropionitrile on Chromosorb P with column, injector and detector operated at 25° and a flow rate of 50 ml./minute. Under these conditions the retention times of bicyclopentene and cyclopentadiene were 3 and 5 minutes, respectively, beyond that of the coinjected air. Since bioyclo-pentene is extremely labile with respect to acid catalysis any contact with water, hydroxylic solvents, and nonprotic acids should be avoided (Note 11). Bicyclopentene stored at —78° in anhydrous tetrahydro-furan is stable indefinitely. 

The stereochemistry of the first step was ascertained by an X-ray analysis [8] of an isolated oxazaphospholidine 3 (R = Ph). The overall sequence from oxi-rane to aziridine takes place with an excellent retention of chiral integrity. As the stereochemistry of the oxirane esters is determined by the chiral inductor during the Sharpless epoxidation, both enantiomers of aziridine esters can be readily obtained by choosing the desired antipodal tartrate inductor during the epoxidation reaction. It is relevant to note that the required starting allylic alcohols are conveniently prepared by chain elongation of propargyl alcohol as a C3 synthon followed by an appropriate reduction of the triple bond, e. g., with lithium aluminum hydride [6b]. 

Another fairly important stationary phase in straight phase PLC is aluminum oxide. Comparable with silica gel also in the case of aluminum oxides, hydroxyl groups at the surface of this adsorbent are responsible for the selective retention of sample molecules. The relevant physical parameters for the characterization of aluminum oxides suitable for straight phase PLC are the following ... 

Solutions that contain sodium citrate/citric acid (Shohl s solution and Bicitra) provide 1 mEq/L (1 mmol/L) each of sodium and bicarbonate. Polycitra is a sodium/potassium citrate solution that provides 2 mEq/L (2 mmol/L) of bicarbonate, but contains 1 mEq/L (1 mmol/L) each of sodium and potassium, which can promote hyperkalemia in patients with severe CKD. The citrate portion of these preparations is metabolized in the liver to bicarbonate, while the citric acid portion is metabolized to C02 and water, increasing tolerability compared to sodium bicarbonate. Sodium retention is also decreased with these preparations. However, these products are liquid preparations, which may not be palatable to some patients. Citrate can also promote aluminum toxicity by augmenting aluminum absorption in the GI tract. 

Goulet, R.R., Lalonde, J.D., Munger, C., Dupuis, S., Dumont-Frenette, G., Premont, S., and Campbell, P.G.C., Phytoremediation of effluents from aluminum smelters A study of A1 retention in mesocosms containing aquatic plants, Water Research, 39, 2291-2300, 2005. 

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