Showing papers on "Gibbsite published in 1973"

Kinetics of Phosphate Adsorption and Desorption by Hematite and GIBBSITE1

Abstract: The phosphate adsorption by hematite and gibbsite conformed to the Freundlich equation. The rate of phosphate adsorption was rapid initially and decreased with prolonged reaction time. A two-constant rate equation was developed which successfully described the rate of phosphate adsorption. T

The Development of Crystalline Structure in Aluminium Hydroxide Polymorphs on Ageing

Abstract: Infrared absorption spectra of the precipitated solids separated from aluminium-hydroxide solutions below the pH of minimum solubility of Al(OH)3 demonstrate the slow ageing of polymeric Al complexes to gibbsite. On comparison with the spectra of natural gibbsites, shifts in absorption frequency during crystal growth are interpreted in terms of changes in hydrogen bonding as a consequence of deprotonation and stacking of aluminium hydroxide layers to form gibbsite. In alkaline solutions the bayerite polymorph precipitates and IR frequencies are compatible with protonation as aluminate ions associate with the bayerite crystal having a lower crystal energy than its low pH polymorph. The infrared spectrum of nordstrandite, which is probably the stable polymorph in alkaline solution, shows evidence of strongly polarized hydroxyl ions similar to gibbsite.

Sorption and desorption of copper by and from clay minerals

Abstract: The sorption of Cu by different clay minerals from dilute CuSO4 solutions was studied as a function of pH. It was found that Cu sorption increased with increasing the equilibrium pH. The low sorption at low pH values was attributed to the competition effect of H+ ions and the release of octahedral Mg, Fe and Al from the 2: 1 minerals in acid solutions. The higher sorption of copper at higher pH values was related to the absence of H+ ions and to the increase in the pH-dependent negative charge in kaolinite and gibbsite.

Process for the production of aluminum chlorohydroxides having a controlled chlorine content

Abstract: A process is described whereby aluminum chlorohydroxide having a controlled chlorine content is prepared by subjecting a mineral containing aluminum oxide or hydroxide (e.g. bayerite, gibbsite, diaspore, boehmite or alumina bayer) is subjected to a preliminary etching with hydrochloric acid at a temperature in the range from 110° to 150° C, the solution so obtained is neutralized with ammonia and the desired aluminum chlorohydroxide (e.g. Al2 (OH)5 Cl) is crystallized out.

Clay mineral composition of some volcanogenous soils in Indonesia and the Philippines

Abstract: Clay fractions of three Andosols and a Latosol occurring in Indonesia, and two Alluvial Soils derived from pyroclastic sediments in the Philippines were examined by means of chemical analyses, X-ray diffraction, differential thermal analysis, thermogravimetry, infrared absorption spectroscopy, and electron microscopy. The results are summarized as follows. Allophane is a dominant clay mineral of young volcanogenous soils occurring in the tropics. Small amounts of halloysite, gibbsite, and imogolite are also found in some of the young volcanogenous soils. Halloysite and imogolite are relatively abundant in the surface soil, while gibbsite is more abundant in the subsoil. In the clay fraction of the young volcanogenous soils in the tropics, α-cristobalite is often present, but quartz occurs rarely. Small amounts of feldspars are also present in the Philippine soils. 2 : 1-type minerals are found to a small extent in some of the sample soils. The above results agree well with the results for Japanes...

Thermal Dehydroxylation and Phase Transformation of Bayer's Alumina

Abstract: Thermal dehydroxylation of Bayer's alumina has been studied by DTA, thermogravimetry, microscopy and X-ray. Giving due consideration to the mechanisms suggested by previous workers and based on the experimental observations made in this study, it is suggested that aluminium tri-hydrate (gibbsite) breaks up in the first instance to mono and dihydrates which subsequently transform to α-alumina through a series of intermediate phases.

Mineralogy and Origin of the Rajahuan Bauxite Deposits, Uttar Pradesh, India

Abstract: Deposits of bauxite were discovered by the Directorate of Geology & Mining, U.P. on the bed rock of Upper Vindhyan sandstone at Rajahuan, district Banda, Uttar Pradesh in the year 1965. This paper deals with the mineralogical studies done on the laterite profile of Rajahuan with the help of X-ray diffraction method. A brief description of the members of the profile along with the development and distribution of chemical constituents and minerals is given. In the bauxite, gibbsite is the chief mineral with subordinate boehmite, sometimes with minor diaspore. Anatase is fairly high. On the basis of field and laboratory data it is concluded that the Rajahuan laterite profile represents an in-situ residuum formed in a regular weathering profile with the bauxite forming in the zone of aeration, which is underlain by cavernous laterite developed in the zone of fluctuation of water table, and the basal lithomarge formed within the zone of saturation. It is suggested that the parent rocks of this residuum were a sandstone-shale sequence.

Dissolved aluminium - contg solns -hydrolysed in presence of crystalline aluminium oxide

Abstract: Treatment of an acid or alkaline soln. contg. dissolved Al, esp. ind. effluents eg from etching processes, is effected by hydrolysis of Al present in hydrolysis reaction in the presence of a crystalline Al oxide, esp an ortho-Al-hydroxide, e.g. Al2O3.3H2O Gibbsite or Bayerite, having 0.5-500 (1-100) mu av. particle size and present in 1-5 (2-3) kg/kg Al concn. Pollution through colloidal Al(OH)3 is prevented and Al is recovered as non-colloidal aq. Al oxide, capable of pelletising and particle size agglomeration e.g. to 5-10 mm.

The Heterogeneous Reactions of Gibbsite Powders with Aqueous Hydroxide Solutions—Kinetics and Mechanism

Abstract: Gibbsite powders (overall surface area, A0 = 1 to 5 m/g) react with well-stirred aqueous sodium hydroxide solutions (0-5 to 4M) according to a four-thirds reaction order w.r.t. powder weight (i.e. second order in powder surface area). Rate constants (in excess alkali) vary linearly with the mean ionic activity ( a ± ) of the hydroxide solution: the rate constant Aw· (at a+ = lg ion/1) for Gibbsite Gi E (A0 = lm/g) is 0-40 g 1 ' 3 h\" at 65°C. Rate constants for the finer powders vary linearly as A0 ; the results indicate that Aclfo (the effective surface area) is about Q1A0. The energies of activation for the reactions at 35 to 65C vary from 22-1 to 20-8 kcal mol 1 . The rate-determining step for the dissolution appears to be a bimolecular reaction between hydroxyl ions adsorbed on the powder crystal surface and adjacent reactive defect Al-OH sites.