Aluminium hydroxide

About: Aluminium hydroxide is a research topic. Over the lifetime, 2043 publications have been published within this topic receiving 22032 citations. The topic is also known as: Al(OH)3 & Amphojel.

The characterisation of aluminium hydroxide gels by nitrogen adsorption

Abstract: Aluminium hydroxide gels with a range of textures have been prepared by the hydrolysis of aluminium s- butoxide with water, aqueous ethanol and aqueous glycerol. Crystallisation was permitted to take place to varying extents by ageing of precipitates in their mother liquors at room temperature. Adsorption isotherms on the outgassed gels were of Types II and IV of the Brunauer classification. An examination of the data by plotting reduced isotherms (V/Vmversus P/Po) revealed the existence of reversible capillary condensation on some of the hydroxides, although the isotherms were of Type II. The Lippens de Boer t method has been found useful in locating the onset of capillary condensation in an adsorption isotherm, but the t-plot can be misleading with samples that have a spread of pore dimensions extending into both the micro- and transitional-pore regions. This situation appears to arise in pseudoboehmites aged for extended periods so that cementation is extensive. The principal factors influencing the texture of the gels appear to be the extent of crystallisation and the amount of inter-particle cementation. Thus amorphous material prepared in water was found to be porous whereas that precipitated in glycerol, which apparently protects the surface of the primary particles, was non-porous (or macro-porous). Transitional pore systems with the best definition were obtained with pseudoboehmites, especially with those formed by ageing in aqueous ethanol. In water, the ready conversion of pseudoboehmite to low-area, non-porous, bayerite is a complicating factor.

Sorption of chromium(VI) and chromium(III) on aluminium hydroxide

Abstract: Factors that influence the sorption of Cr(VI) and Cr(III) on aluminium hydroxide were investigated. The sorption of chromates decreases as the pH of the suspension increases. The mechanism of CrO 4 2− sorption was interpreted in terms of reactions between chromates and −OH and/or H2O groups at the hydroxide/liquid interface. It has been shown that chromates are more tightly sorbed on aluminium hydroxide compared to other anions, e.g. chlorides. On the other hand, specifically absorbed anions, such as molybdates, compete strongly with chromates for the sorption sites. The sorption of chromium(III) increases with the pH of the suspension. Also, the sorption of chromium(III) is suppressed in the presence of citrate ions. The best conditions for the fixation of Cr(VI) and Cr(III) by aluminium hydroxide are presented.

Effect of aluminium hydroxide on serum ionised calcium, immunoreactive parathyroid hormone, and aluminium in chronic renal failure.

Abstract: According to the Bricker-Slatopolsky theory, secretion of parathyroid hormone (PTH) is switched on in chronic renal failure by hypocalcaemia due to phosphate retention. In an attempt to reverse this process 20 patients in preterminal renal failure (plasma creatinine 569 +/- 195 mumol/l) were given aluminium hydroxide, 3.8 g daily. They were studied for four weeks and all measurements were made at the start and weekly, except measurements of serum aluminium concentration, which were made at the start and at the end of the fourth week. Mean serum phosphate fell from 1.89 to 1.47 mmol/l (5.9 to 4.6 mg/100), mean serum calcium rose from 2.07 to 2.24 mmol/l (8.3 to 9.0 mg/100 ml), and serum ionised calcium rose from 1.07 to 1.20 mmol/l (4.3 to 4.8 mg/100 ml), but serum immunoreactive PTH did not fall. Thirteen patients had initial serum immunoreactive PTH concentrations at or near to normal and 11 were taking beta-blockers but even in those with neither explanation, PTH concentrations did not fall. Serum aluminium concentrations rose from 0.4 to 1.02 mumol/l (10.9 to 27.4 microgram/l). Aluminium hydroxide corrects serum phosphate, total calcium, and ionised calcium at the price of a rise in serum aluminium concentration; in this study it did not affect serum immunoreactive PTH. The Bricker-Slatopolsky theory still needs verification in studies of patients with chronic renal failure.

Probing the formation process of aluminium hydroxide nanoparticles prepared by laser ablation with 27Al NMR spectroscopy

Abstract: The 27Al MAS NMR spectra of amorphous alumina exhibit three resonances resulting from aluminium in four-, five-, and six-coordination, whereas samples containing crystalline particles of bayerite, gibbsite, and boehmite show only a single resonance associated with six-coordinate aluminium.