Showing papers on "Gibbsite published in 1987"
TL;DR: In this paper, a new internally consistent set of log K sp values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams, which is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size.
141 citations
TL;DR: In this paper, the surface charge ( sigma 0)-pH data of a synthetic pure crystalline gibbsite suspension were analyzed with a recently proposed one-step charging model for proton adsorption (one-pK model).
Abstract: Titration curves of a synthetic pure crystalline gibbsite suspension have been made at three NaCl levels. The synthesized gibbsite is characterized by TEM, TGA and X-ray diffraction. The overall BET surface area and the surface area of the edges of the hexagonal crystals are determined. The surface structure of gibbsite is discussed. The surface charge ( sigma 0)-pH data are analysed with a recently proposed one-step charging model for proton adsorption (one-pK model). Analysis of the data suggests that the singly coordinated surface hydroxyls are probably the dominant reactive surface group. Considering these groups as reactive only the titration data could be fitted well with the one-pK model if it is extended with pair formation. Only two adjustable parameters are needed, the Stern layer capacitance and the pair formation constant. Analysis of titration data of aluminium oxides, as presented in recent literature, showed that all sigma 0-pH curves could be described rather well with one and the same set of two parameters, the capacitance of the Stern layer and the pair formation constant. The difference in proton adsorption behaviour between different aluminium (hydr)oxides is mainly caused by differences in the site distribution and the site densities of the aluminium (hydr)oxides involved. The results suggest that pair formation should be taken into account. (Abstract retrieved from CAB Abstracts by CABI’s permission)
78 citations
67 citations
TL;DR: In this article, a two-component soil water flow model was used in conjunction with an equilibrium speciation model WATEQF to study aluminum mobility in soils of a forested watershed, White Oak Run, in the Shenandoah National Park, Virginia.
Abstract: A two-component soil water flow model was used in conjunction with an equilibrium speciation model WATEQF to study aluminum mobility in soils of a forested watershed, White Oak Run, in the Shenandoah National Park, Virginia. Soil solution samples, taken from the O, E, B, C1, and C2 horizons, were collected from zero-tension lysimeters designed to collect faster gravitational macropore flow and tension lysimeters designed to collect slower capillary micropore flow. Dissolved aluminum was fractionated into acid-soluble, inorganic monomeric, and organic monomeric aluminum. Soil water aluminum concentrations decreased with depth indicating that the deep soil is a sink for aluminum. All waters contained significant concentrations of acid-soluble aluminum and exhibited a negative correlation between pH and the inorganic monomeric aluminum concentrations. Water in the shallow soil showed distinctly different chemical compositions for the two flow types, while C horizon micropore and macropore waters were more similar. Because of its shorter residence time, water flowing in deep soil macropores underwent less extensive neutralization and immobilization of aqueous aluminum than micropore water. The O horizon macropore waters were undersaturated for all hydroxide, silicate, and sulfate mineral phases considered. The C horizon samples from both flow types were near equilibrium with respect to kaolinite and synthetic gibbsite, indicating that mineral solubility controls water chemistry in the deep soil, while organic substances are the key control in the shallow macropore waters.
58 citations
TL;DR: In this paper, the concentration of alkali metals, alkaline earths and halogens were monitored in an Australian weathering profile and in Brazilian soils and bauxite, and the materials analysed are considered to represent a range of chemical weathering histories, which are distinguished with respect to their degree of leaching by the dominant aluminosilicate assemblages.
49 citations
TL;DR: In this article, the difference of aluminum hydroxide solubility between acidic and alkaline medium is still observed, and it is shown that the difference in the minimum of aluminum trifluoride is related to the formation of a new solid phase: bayerite.
49 citations
TL;DR: In this article, the results indicated that the Ae (E) horizon solutions were of low pH and contained mainly organically bound Fe and Al, while the H4SiO4 was supersaturated with respect to likely occurring crystalline and amorphous aluminosilicates [kaolinite, halloysite, allophane (Al:Si=l) and imogolite].
Abstract: SUMMARY
Thirty-one soil solutions were extracted by immiscible displacement with CCl4 under high speed centrifugation from sub-horizons of three podzolic soils from north-eastern Ontario, Canada. The solutions were analysed for major cations and anions and a speciation of dissolved Fe and Al was attempted to distinguish ‘free’, ‘organically bound’ and ‘inorganically bound’ species. Results indicated that the Ae (E) horizon solutions were of low pH and contained mainly organically bound Fe and Al. With depth, pHs increased, ionic strengths decreased and the relative proportion of inorganically bound Fe and Al increased. Although application of phase diagrams permitted only a semi-quantitative interpretation of the data, all horizon solutions, with the exception of some Ae solutions, appeared supersaturated with respect to likely occurring crystalline and amorphous aluminosilicates [kaolinite, halloysite, allophane (Al:Si=l) and imogolite]. Of the phases considered, reactions involving imogolite-allophane, gibbsite-halloysite, gibbsite-allophane and gibbsite-imogolite all appeared reasonable in controlling the content of Al3+ and H4SiO4 in solution, although the presence of gibbsite and imogolite could not be definitely confirmed in these soils.
37 citations
TL;DR: In this article, the solubility of kaolinite and alumina is investigated and the contribution of surfactant precipitation with dissolved mineral species is determined, and aluminum was observed to occur in significant amounts under certain pH conditions.
36 citations
33 citations
TL;DR: The Mt. Saddleback bauxite is derived from a mafic volcanic (greenstone) parent material and has high Fe and low silica contents compared with other bauxites in the region as discussed by the authors.
21 citations
TL;DR: In this article, an attempt is made to reveal a geochemical compatibility with paleoenvironment to understand the genesis of bauxite deposits that are derived from two different parent rocks.
TL;DR: In this paper, the authors studied five profiles around the Longonot and Susua volcanoes in Kenya and found that all profiles have some resemblance to Andepts, but there were clear-cut differences in clay contents and mineral composition as well as pH between profiles 1 through 4 and profile 5, which occur under semi-arid to subhumid and under humid climatic conditions, respectively.
TL;DR: In this paper, the authors studied the clay mineralogy of 59 Alfic and Ultic Haplaquod pedons with respect to distributional relationships involving horizons, chemical parameters, and geomorphic surfaces.
Abstract: The clay mineralogy of 59 Alfic and Ultic Haplaquod pedons was studied with respect to distributional relationships involving horizons, chemical parameters, and geomorphic surfaces. Relative estimates of clay-sized minerals were based on x-ray diffraction (XRD) peak height ratios after calibration with standards and normalization. Mineralogical differences based on horizon, base status, or elevational groupings were tested statistically. Quartz dominated the clay fractions of upper, sandier horizons for all pedons. Kaolinite, smectite, and gibbsite were usually more abundant in deeper, finer textured horizons. Hydroxy-interlayered minerals, relative to other phyllosilicates, were significantly concentrated (p 30 m) geomorphic surfaces: (i) were virtually depleted of bases, (ii) contained little or no smectite, and (iii) were dominated by kaolinite in lower horizons. Soils on younger (>30 m) surfaces contained significantly (p = 0.0054) more smectite than older surfaces on the average, and differences were even greater when only ultic subgroups were considered. The mineralogical-chemical-geomorphic relationships collectively support the concept that smectite stability decreases with the loss of bases which has occurred most thoroughly on the oldest surfaces.
TL;DR: Apatites occurring in lateritic residues derived from high-grade metamorphic rocks from Sri Lanka are hydroxy-apatite as indicated by EPMA and XRD.
TL;DR: In this article, detailed micromorphological observations and associated electron probe microanalyses are used to examine the proposition that kaolinite and gibbsite in the B horizon of a humus iron podzol could arise by transformation of allophanic deposits.
Abstract: SUMMARY
Detailed micromorphological observations and associated electron probe microanalyses are used to examine the proposition that kaolinite and gibbsite in the B horizon of a humus iron podzol could arise by transformation of allophanic deposits. The B horizon of this podzol is highly complex. In the upper B horizon, this complexity is due to alternating episodes of the influx of organic matter and the deposition of allophanic material; evidence for the separate deposition of allophane and organic matter is presented. Material within the B horizon that has gibbsiporphyric fabric appears to have arisen by crystallization of gibbsite from aluminium-rich gels deposited before the main influx of allophanic material; there is no convincing evidence that allophanic material has transformed to kaolinite or gibbsite.
TL;DR: Laterite profiles developed over gabbro, granophyre of the Ezhimala Complex are discussed in this article, where the principal mineral assemblages of the laterites are kaolinite, gibbsite, goethite, hematite and quartz with minor amounts of zircon.
TL;DR: In this article, a detailed study of the ancient weathering profile comprising the laterite-bauxite duricrust has been conducted and the conditions favouring bauxitisation back in early Eocene times is discussed.
TL;DR: In this article, an analytical electron microscopy was used to characterize leached layers formed on a synthetic basalt glass after 300 days in deionized water, sodium chloride solutions, or sodium chloride solution containing magnesium chloride.
Abstract: Analytical electron microscopy was used to characterize leached layers formed on a synthetic basalt glass after 300 days in deionized water, sodium chloride solutions, or sodium chloride solutions containing magnesium chloride. Ultramicrotomed cross-sections show that the leached layers consist of a mixture of amorphous and crystalline phases whose composition and microstructure are sensitive to solution chemistry. In general, Na, Ca and Mg are selectively leached in all solutions, leaving behind surface alteration products which are rich in Fe, Ti, and Al. In deionized water and the NaCl solution, gibbsite (Al(OH)/sub 3/) is a major phase; in the Mg-containing solution, Si and Al are retained as smectite clays. Results are compared to the alteration of natural basalt glasses in marine environments, particularly as they relate to the use of basalt glass alteration as a means of verifying the long-term leaching behavior of nuclear waste form borosilicate glasses. 32 refs., 4 figs., 4 tabs.
TL;DR: In this article, suspensions of Al(OH)3gel, gibbsite, or alumina were loaded with up to 5'μ mol of Cu, Pb, Cd, or Zn ions prior to being extracted for 24'h with one of fifteen different chemical solutions.
Abstract: In soil/sediment analysis, subdivision of trace metal content into different categories is usually based on selective extraction schemes. To assess the disposition of metal ions bound to aluminum hydrous oxides in such schemes, suspensions of Al(OH)3gel, gibbsite, or alumina were loaded with up to 5 μ mol of Cu, Pb, Cd, or Zn ions prior to being extracted for 24 h with one of fifteen different chemical solutions. The percentage of sorbed ion retrieved varied along the reagent sequence: NaCl, CaCl2 < MgCl2, NH4NO3 < CH3COONH4, Na citrate, Na4P2O7 < EDTA, DTPA < CH3COOH, H2C2O4, HCl, HNO3. In each system, the recovery value varied with the initial surface loading (a function of sorption pH) and reflected changes in metal species form, e.g., bonded M2+, (MOH+), M(OH)2. With low loading levels up to 40% was displaced by salt solutions; with 1 to 2 μ mol sorbed, as little as 10% was displaced by acids or complex formers but this increased to ~90% with higher loadings. The relationship between sorption pH, amou...
TL;DR: Lateritic soils near Calicut, Kerala, contain halloysite of intermediate hydration, kaolinite, goethite, gibbsite and quartz as mentioned in this paper, which is responsible for relatively high plasticity and cation-exchange capacity.
Patent•
04 Feb 1987
TL;DR: In this article, the authors proposed a method to produce the titled product useful as a filler, containing no aluminum hydroxide of boehmite type without causing whitening, opacifying, etc.
Abstract: PURPOSE: To make it possible to produce the titled product useful as a filler, containing no aluminum hydroxide of boehmite type without causing whitening, opacifying, etc., by subjecting aluminum hydroxide of gibbsite type to hydrothermal treatment in a specific temperature range. CONSTITUTION: Aluminum hydroxide of gibbsite type is subjected to hydrothermal treatment at 50W200°C, namely heated in water or steam. In the operation, when the hydrothermal treatment is lower than 50°C, the effect of improvement in heat resistance is low and the aimed heat-resistant aluminum hydroxide is not obtained. On the other hand, the temperature is higher than 200°C, change from gibbsite structure to boehmite structure readily occurs and problems of opacifying arouse. Loss in heat energy also increases. COPYRIGHT: (C)1988,JPO&Japio
Patent•
10 Feb 1987
TL;DR: In this article, a process for the production of crystalline boehmite of fine particle size and enhanced specific surface area is described. But this process requires the use of a large amount of caustic aluminate liquid.
Abstract: The present invention provides a process for the production of crystalline boehmite of fine particle size and enhanced specific surface area. Coarse gibbsite particles, obtained from the Bayer Process, are lightly calcined and the non-boehmite-containing material is removed by dissolution in caustic aluminate liquors of appropriate composition.
01 Jan 1987
TL;DR: In this paper, the influence of stress relaxation arising on intercalation of lithium salts into gibbsite on the reactivity of the host has been studied and it is shown that stresses due to the misfit between the host and the product lead to disordering of aluminium hydroxide layers in the region situated directly ahead of the interface.
TL;DR: In this paper, thermogravimetry was used to study the chlorination reactions of gibbsite and its partially dehydrated products with phosgene with the objective of obtaining information on the degree of dehydration.
Journal Article•
TL;DR: In this paper, the Paduvan laterite profile is characterized by relatively strong depletion of soda and potash and enrichment of ferrides, and the latent profile is dominated by gibbsite with kaolinite compared to goethite-hematite in the ferruginous laterite horizons.
Abstract: The different litho-units of the weathering profile of Paduvan Plateau show clear gradation contacts and contain relics of nearly all the minerals which are native to the underlying granitic gneiss. Mineralogically, the latent profile is dominated by gibbsite with kaolinite compared to lithomarge and goethite-hematite in the ferruginous laterite horizons. There is evidence of development of gibbsite both by the direct alteration of feldspar of the precursor rock and by the desilication of kaolinite. Four stages of transformation represented by altered gneiss, lithomarge, laterite and aluminous laterite bauxite are maintained in the weathering profile. As compared with the basalt derived laterite profiles, the Paduvari occurrence is characterised by relatively strong depletion of soda and potash and enrichment of ferrides. The field, petrographic mineralogical and geochemical data provide enough evidence of formation of Paduvan laterite profile by the in-situ chemical weathering of the underlying granitic gneiss and the aluminous laterite-bauxite by the 'in-situ chemical reworking' of laterite.
TL;DR: In this article, the chemistry of the solution as a function of time was monitored, as well as the chemistry properties of the nepheline surfaces, which indicated that precipitation kinetics favour the formation of bauxite deposits in tropical regions (i.e. T ⩾25°C), but not in temperate regions.
TL;DR: In this article, the authors used thermogravimetry for the quantitative determination of halloysite, kaolinite and gibbsite in ∼10 mg altered feldspar grains from lateritic saprolite materials.
Abstract: Thermogravimetry is a fast, accurate and highly sensitive method for the quantitative determination of halloysite, kaolinite and gibbsite in ∼10 mg altered feldspar grains from lateritic saprolite materials. A wide range in composition occurs between grains, and is evidence of the existence of various geochemical microenvironments within lateritic saprolite. Variations in dehydroxylation temperature of gibbsite and halloysite/kaolinite between the altered feldspar grains are an analytical artefact. The dehydroxylation temperature of gibbsite and halloysite/kaolinite increased from 242 °C to 302 °C and 454 °C to 491 °C respectively with the increase in the concentration of these minerals in the altered feldspar grains.
Journal Article•
TL;DR: Al-interlayered montmorillonite has been synthesized at room temperature and l00oC for 2 weeks and showed a basal spacing of 13 A after heating at 6@oC as mentioned in this paper.
Abstract: Al-interlayered montmorillonite, gibbsite and boehmite have been synthesized at room temperature and l00oC. The Al-interlaygred montmorillonite, which shows a basal spacing of 13 A after heating at 6@oC, is the most stable at room temperature for 2 weeks. Over a longer period, gibbs- ite at room temperature or'boehmite at l@oC grows from the Al-interlayered montmorillonite, The hexagonal plates of gibbsite and the latlr of boehmite are usually associated with, andgrow on, films of the montmorillonite. Gibbsite and boehmite develop well in the X and Y directions, but have a limited thickness. At room temperature, tle SiO2,/Al2O3 ratio of the film ranges from 0.9 to 1.25, which is close to that of dioctahedral chlorite and different from that of the film at 1@"C (range from 1.8 to 2.7).. The gibbsite and boehmite have a SiO2/Al2O3 ratio of 0.19 and 0.56, respectively, which suggests that they grew on the surface of the Al-interlayered montmorillonite films. The pH, CEC, and surface area changed witl agkrg, which suggests that Al-interlayered montmorillonite is zufficiently ' unstable to peel off the Al-interlayer after longer periods at room temperature and l@oc.