Showing papers on "Gibbsite published in 2010"
TL;DR: Characterization studies revealed the presence of boehmite, cancrinite, chantalite, hematite, gibbsite, anatase, rutile and quartz, found responsible for carbonation of red mud, which was reported to be an inexpensive and effective adsorbent.
144 citations
TL;DR: The Dajia Salento-type bauxite deposit in western Guangxi is hosted within the Quaternary ferrallitic soil profile, and it formed via breaking up, weathering and oxidizing of Permian Bauxite orebodies occurring as a semi-continuous layer in the upper permian as mentioned in this paper.
104 citations
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05 Oct 2010TL;DR: In this article, the authors present a collection of available data for the verification of Gibbsite structures and properties, including anion and cation sarsification on the surface of the site.
Abstract: FOREWORD. PREFACE. CHAPTER 1 - Aluminum Oxides and Hydroxides under Environmental Conditions. 1. INTRODUCTION. 1.1 Occurrence of Aluminum Oxides and Hydroxides in the Subsurface. 1.2 Occurrence of Aluminum Oxides and Hydroxides in Surface Water. 1.3 Use of Aluminum Hydroxide in Water Treatment. 1.4 Summary. CHAPTER - Formation and Properties of Gibbsite and closely-related minerals. 2. Formation and properties of Gibbsite and closely-related minerals. 2.1 Al Polymerization Models. 2.2 Formation of Gibbsite and Other Al-Hydroxides and Oxyhydroxides. 2.3 Aluminum Hydroxide Polymorphs: Structure and Nomenclature. 2.4 Gibbsite. 2.5 Bayerite. 2.6 Nordstrandite. 2.7 Doyleite. 2.8 Other forms of aluminum oxides and oxyhydroxides. 2.9 Other forms that manufactured under high temperature and pressure. CHAPTER 3 - Types of Available Data. 3.1 Gibbsite Structure Verification. 3.2 Physical-Chemical Properties. 3.3 Acid-Base Titration Data. 3.4 Cation and Anion Sorption Data. 3.5 Spectroscopic Data for Sorption on Gibbsite. 3.6 Proton Release/Uptake Data. 3.7 Electrokinetic Data. 3.8 Summary. CHAPTER 4 - Data Compilation and Treatment Methods. 4.1 Collection of data. 4.2 Assessment of Data Quality. 4.3 Compilation of Surface Properties. 4.4 Extraction of Equilibrium Sorption Constants. 4.5 Optimal Fit Simulations. 4.6 Presentation of Results. CHAPTER 5 - Surface Properties of Gibbsite. 5.1 Surface Area. 5.2 Site Density. 5.3 Point of Zero Charge. 5.4 Surface Acid-Base Chemistry. 5.5 Effects of Dissolution on Gibbsite Surface Acid-Base Chemistry. 5.6 Summary. CHAPTER 6 - Cation Sorption on Gibbsite. 6.1 Modeling Methodology and Reactions. 6.2 Available Spectroscopic Data and Use in Modeling. 6.3 Copper. 6.4 Lead. 6.5 Cobalt. 6.6 Cadmium. 6.7 Manganese. 6.8 Iron. 6.9 Calcium. 6.10 Zinc. 6.11 Mercury. 6.12 Uranium. 6.13 Thorium. CHAPTER 7 - Anion Sorption on Gibbsite. 7.1 Modeling Methodology and Reactions. 7.2 Available Spectroscopic Data and Use in Modeling. 7.3 Phosphate. 7.4 Arsenate. 7.5 Arsenite. 7.6 Molybdate. 7.7 Selenate. 7.8 Chromate. 7.9 Borate. 7.10 Sulfate. 7.11 Fluoride. 7.12 Silicate. CHAPTER 8 - Coherence and Extrapolation of Results. 8.1 Cation Sorption on Gibbsite. 8.2 Anion Sorption on Gibbsite. 8.3 Comparison of Gibbsite surface complexation constants with those of Goethite, Hydrous Ferric Oxide and Hydrous Manganese Oxide. 8.4 Summary. REFERENCES. APPENDIX A. Summary of Experimental Details.
100 citations
TL;DR: In this paper, the behavior of rare earth elements (REEs) and yttrium (Y) during chemical weathering processes has been investigated on a 4.05m thick terra rossa profile over dolomite on the Yunnan-Guizhou Plateau, China.
79 citations
TL;DR: In this article, the starting temperature of the dehydration reaction of γ-Al(OH) 3 was analyzed using non-isothermal thermoanalysis and the Kissinger equation, and it was concluded that the starting temperatures of the de-hydration reaction of ǫ-AlOOH rose with increasing heating rate of the system.
58 citations
TL;DR: In this article, the β -factor of each phase was calculated using the harmonic phonon dispersion curves obtained within density functional theory, and the resulting fractionation laws systematically overestimate measurements by 15 ǫ at low temperatures to 8 ð at ≈400 ǵ.
56 citations
TL;DR: In this paper, the specific signatures of α-Al 2 O 3 powders by a combination of X-ray diffraction (Rietveld analysis), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal analysis (TG-DTA) and cathodoluminescence (CL) were investigated.
54 citations
TL;DR: In this article, a mineralogical characterization through mineral quantification of Brazilian soils by X-ray diffraction data using the Rietveld Method is not common, and the results showed that quartz, gibbsite, rutile, hematite, goethite, kaolinite and halloysite were present in the clay and silt fractions of all horizons.
Abstract: The mineralogical characterization through mineral quantification of Brazilian soils by X-ray diffraction data using the Rietveld Method is not common. A mineralogical quantification of an Acric Ferralsol from the Ponta Grossa region, state of Parana, Brazil, was carried out using this Method with X-Ray Diffraction data to verify if this method was suitable for mineral quantification of a highly-weathered soil. The A, AB and B3 horizons were fractioned to separate the different particle sizes: clay, silt, fine sand (by Stokes Law) and coarse sand fractions (by sieving), with the procedure free of chemical treatments. X-ray Fluorescence, Inductively Coupled Plasma Atomic Emission Spectrometry, Infrared Spectroscopy and Mossbauer Spectroscopy were used in order to assist the mineral identification and quantification. The Rietveld Method enabled the quantification of the present minerals. In a general way, the quantitative mineralogical characterization by the Rietveld Method revealed that quartz, gibbsite, rutile, hematite, goethite, kaolinite and halloysite were present in the clay and silt fractions of all horizons. The silt fractions of the deeper horizons were different from the more superficial ones due to the presence of large amounts of quartz. The fine and the coarse sand fractions are constituted mainly by quartz. Therefore, a mineralogical quantification of the finer fraction (clay and silt) by the Rietveld Method was successful.
45 citations
TL;DR: In this paper, the authors provided insight into large-scale kaolinization of Variscan granitoids in the Iberian massif, based on an integrated study combining mineralogical, geochemical, and stable isotope data from the Nuevo Montecastelo kaolin deposit (NW Spain).
37 citations
01 Jan 2010
TL;DR: The oxic horizon is a strongly weathered subsurface horizon with a clay fraction dominated by low-activity clays and iron and aluminium oxides, and with silt and sand fractions mainly composed of quartz and including little or no weatherable minerals as mentioned in this paper.
Abstract: Publisher Summary This chapter discusses the oxic and related materials. The oxic horizon is a strongly weathered subsurface horizon with a clay fraction dominated by low-activity clays and iron and aluminium oxides, and with silt and sand fractions mainly composed of quartz and including little or no weatherable minerals. The oxic horizon essentially corresponds to the ferralic horizon of the World Reference Base for soil resources. Oxic and ferralic horizons are diagnostic horizons of Oxisols and Ferralsols, respectively. Micromorphological techniques have been often used in the study of oxic and related materials. Wide attention has been given to the study of the granular microstructure that is typical for these materials, but no consensus has been reached on its origin. Submicroscopic techniques were mainly used to study mineral weathering, mainly of quartz, and the formation of kaolinite, iron oxides, and gibbsite occurrences.
32 citations
TL;DR: In this article, the authors focused on the genesis and agricultural potential of the pre-Cambrian Bambui Group landscape, and two areas were selected in Curvelo, state of Minas Gerais, for a detailed study of physical, chemical and mineralogical properties of these soils, to deepen the understanding of the pedogenesis of this area.
Abstract: The widespread occurrence of Cambisols (shallow, dense and silty) and of clayey and very clayey Latosols is typical of pelitic rocks of the pre-Cambrian Bambui Group landscape, but few studies are focused on the genesis and agricultural potential of these soils. Two areas were selected in Curvelo, state of Minas Gerais, for a detailed study of physical, chemical and mineralogical properties of these soils, to deepen the understanding of the pedogenesis of this area. Soils classified as Haplic Cambisols (Inceptisols), Red-Yellow latosol (Xanthic Haplustox) and Red latosol (Rhodic Haplustox) were selected and sampled, and analyzed for the chemical, mineralogical and physical properties. The XRD data coupled with the calculated weathering index indicated a lower degree of weathering in the shallow Cambisols, with higher proportion of illite and kaolinite in the clay fraction, in comparison to the Latosols, where kaolinite, gibbsite and hydroxy-interlayered vermiculite (HIV) coexist. In this case, the occurrence of gibbsite is not a good indicator of severe weathering. In the shallow Cambisols, higher silt content combined with a face-to-face arrangement of clay particles (kaolinite/illite) may have resulted in poor structural organization, denseness, low water infiltration and soil sealing. In the clay fraction of Latosols, we observed the coexistence of kaolinite/illite and Fe/Al oxides, similarly to the Cambisols, but with much less illite and higher gibbsite contents, as inferred from the results of Ki of around 1.4. Although there are no remarkable physical and chemical differences among Latosols, the Rhodic Latosols displayed considerable magnetization in the sand fraction, where XRD confirmed the presence of magnetite, an uncommon fact in the supposedly magnetite-free pelitic lithologies of the Bambui Group, but reported in previous studies as well.
15 Dec 2010
TL;DR: Nanogibbsite was synthesized using a supersaturated Al(OH)(3) solution which was prepared by titration of AlCl(3) with NaOH at pH 4.6 and when subjected to heat treatment, gibbsite→alumina conversion occurred by two mechanisms.
Abstract: Nanogibbsite was synthesized using a supersaturated Al(OH)3 solution which was prepared by titration of AlCl3 with NaOH at pH 4.6. Excess chloride ions in the system were stripped off by dialyzing the Al(OH)3 suspension against distilled water. The dialysis step is critical for initiation of gibbsite crystallization or the Al(OH)3 suspension would remain amorphous. Chloride ions seem to mask the seeding sites and so retard the overall process of gibbsite formation. When subjected to heat treatment, gibbsite → alumina conversion occurred by two mechanisms. Nanogibbsite → α-alumina phase transition occurred forming χ- and κ-alumina polymorphs.
TL;DR: In this paper, geomicrobiological analysis makes it possible to verify that microorganisms have played a critical role during the formation of bauxite with the possibility already intimated in previous studies.
Abstract: Bauxite deposits are studied because of their economic value and because they play an important role in the study of paleoclimate and paleogeography of continents. They provide a rare record of the weathering and evolution of continental surfaces. Geomicrobiological analysis makes it possible to verify that microorganisms have played a critical role during the formation of bauxite with the possibility already intimated in previous studies. Ambient temperature, abundance of water, organic carbon and bioavailable iron and other metal substrates provide a suitable environment for microbes to inhabit. Thiobacillus, Leptospirilum, Thermophilic bacteria and Heterotrophs have been shown to be able to oxidize ferrous iron and to reduce sulfate-generating sulfuric acid, which can accelerate the weathering of aluminosilicates and precipitation of iron oxyhydroxides. Microorganisms referred to the genus Bacillus can mediate the release of alkaline metals. Although the dissimilatory iron-reducing and sulfate-reducing bacteria in bauxites have not yet been identified, some recorded authigenic carbonates and “bacteriopyrites” that appear to be unique in morphology and grain size might record microbial activity. Typical bauxite minerals such as gibbsite, kaolinite, covellite, galena, pyrite, zircon, calcium plagioclase, orthoclase, and albite have been investigated as part of an analysis of microbial mediation. The paleoecology of such bauxitic microorganisms inhabiting continental (sub) surfaces, revealed through geomicrobiological analysis, will add a further dimension to paleoclimatic and paleoenvironmental studies.
TL;DR: A nitrogen budget study of a highly fertilized coffee plantation growing on an Acrisol (Ultisol: Ustic Paleohumult) in Southern Costa Rica provided clear evidence of low nitrate (NO 3 − ) leaching to groundwater, in spite of a large annual rainfall and fairly high soil permeability.
TL;DR: The Joda-Barbil region of the Jamda-Koira valley is one of the most important sources of iron ores in India as mentioned in this paper, and the mineralogy, texture, and chemical composition of iron ore of the region have been analyzed to understand the presence of different types of goethite and their compositional variation with respect to Fe, Al2O3, SiO2, and P that are essential for upgrading the ores for iron and steel making.
Abstract: The Joda–Barbil region of the Jamda–Koira valley is one of the most important sources of iron ores in India. The mineralogy, texture, and chemical composition of iron ore of the region have been analyzed to understand the presence of different types of goethite and their compositional variation with respect to Fe, Al2O3, SiO2, and P that are essential for upgrading the ores for iron and steel making. The iron ore samples have been investigated by optical microscopy, EPMA, XRD, and TG-DTA. The optical microscopy studies have indicated three dominant textural types of goethite, such as (a) colloform-banded vitreous, (b) massive vitreous, and (c) earthy or ochreous goethite. The vitreous goethite is hard and crystalline, whereas ochreous goethite is clayey and consists of ultrafine crystallites often intimately admixed with kaolinite and gibbsite. EPMA studies indicated that (a) ochreous and colloform-banded goethite contain more alumina compared to massive vitreous goethite and (b) colloform-banded goethite...
TL;DR: In this article, a physically consistent model for leaching was obtained by considering fractal geometry of the shrinking gibbsite particles and residual aluminium concentration, which showed perfect agreement with the data.
TL;DR: In this paper, an attempt was made to directly synthesize a Bronsted-type catalyst based on the hydrocalumite-like structure by controlled hydrolysis of calcium and aluminium alkoxides.
TL;DR: In this article, the states of chromium in both promoted and unpromoted alumina-chromium catalysts with various chromium contents prepared with the use of a centrifugal thermal activation product of gibbsite were studied in detail.
Abstract: The states of chromium in both promoted and unpromoted alumina-chromium catalysts with various chromium contents prepared with the use of a centrifugal thermal activation product of gibbsite were studied in detail. The presence of five chromium species was found in the catalysts of this type: two Cr6+ and three Cr3+ species. The concentration of each particular chromium species depends on the total chromium content of the catalyst. Based on the experimental data, we hypothesized that highly disperse Cr3+ particles, the formation of which was completed at a chromium content of ∼7–9 wt %, are responsible for the catalytic activity of alumina-chromium samples in the reaction of isobutane dehydrogenation.
TL;DR: In this article, a pragmatic approach to measure precipitation ratios, determine product phase, morphology and particle size distribution, and assess the impacts and adjustment capability of main parameters such as seed, temperature, ethanol medium, and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.
TL;DR: In this article, a modified commercial (Setaram C80) calorimeter was used to measure the isobaric volumetric heat capacities of concentrated alkaline sodium aluminate solutions at ionic strengths from 1 to 6 mol kg-1, with up to 40 mol.
TL;DR: In this article, surface charge characteristics were investigated using a charge fingerprinting procedure for 90 samples from 32 profiles of highly weathered Oxisols and Ultisols derived from shale/limestone, basalt, granite, local alluvium, sedimentary, and metasedimentary rocks under tropical savanna and tropical monsoonal climates in Thailand.
Abstract: Surface charge characteristics were investigated using a charge fingerprinting procedure for 90 samples from 32 profiles of highly weathered Oxisols and Ultisols derived from shale/limestone, basalt, granite, local alluvium, sedimentary, and metasedimentary rocks under tropical savanna and tropical monsoonal climates in Thailand. The charge fingerprints of 5 whole soils, after removal of organic matter and of kaolin and ion oxides from these soils, were also measured to clarify factors contributing to the variable charge behaviour. Phosphate sorption was determined and related to charge properties. Kaolin was the dominant mineral of the clay fraction with moderate amounts of goethite and hematite. Gibbsite was present in Oxisols formed on limestone and basalt under more humid conditions. All soils exhibited variable charge behaviour but the magnitude and rate of change in variable charge with pH varied greatly between Oxisols and Ultisols. Oxisols had higher amounts of variable charge than Ultisols, reflecting the differences in amounts of clay and extractable Fe and Al. Oxisols formed on basalt and limestone under more humid conditions had high values of anion exchange capacity (AEC) due to the contributions of goethite, gibbsite, and boehmite. The relationships of base cation exchange capacity (CECB) and AEC with pH were linear. Rates of change with pH of both negative and positive variable charge (Ac, Aa) were closely related to CEC, specific surface area (SSA), pH(NaF), and various forms of extractable Fe, Al, and Mn. The charge fingerprints of soil after removal of organic matter indicated that organic matter exerted a strong influence on both the magnitude of negative charge and rate of change with pH. Kaolin had permanent and variable charge, with SSA and crystal size (MCD001) being highly predictive of the rate of change in variable negative charge with pH. Iron oxide concentrates exhibited strongly pH-dependent charge and the mean coherently diffracting length (MCD110) of hematite was highly predictive of both the magnitude and rate of change in variable positive charge with pH. Charge coefficients (Ac, Ba) had highly significant (P = 0.005) positive relationships with Langmuir and Freundlich phosphate sorption maximum coefficients (Xm, k), indicating that the surfaces of amorphous, poorly ordered, and crystalline Fe and Al oxides are prime sites for both P sorption and variable charge.
TL;DR: In this article, the degradation rate of pure boehmite in concentrated sodium hydroxide solutions was studied experimentally and modelled mathematically, under ambient pressure and at 60°C-85°C in the kinetic regime, and the changes in morphology of the solid phase were studied by particle size, porosity and surface area measurements as well as SEM imaging.
TL;DR: In this paper, a new synthesis method is described to produce aluminosilicate inorganic polymers by direct reaction of aluminium hydroxide with amorphous silica under alkaline conditions.
Abstract: A new synthesis method is described to produce aluminosilicate inorganic polymers by direct reaction of aluminium hydroxide with amorphous silica under alkaline conditions. XRD and 27Al and 29Si MAS NMR spectroscopy suggest that the reaction mechanism involves the dissolution of the aluminium hydroxide in the alkali. The best results are obtained with more reactive gibbsite of small particle size and X-ray amorphous ρ-alumina containing 5-fold coordinated Al, and with compositions in the previously reported optimum range (SiO2: Al2O3 = 3.0, M2O: SiO2 = 0.34, H2O: M2O = 9.4). Unreacted aluminium hydroxide occurs where there is insufficient silica for complete inorganic polymer formation but the reaction is less sensitive to variations in the K2O: Al2O3 and K2O: SiO2 ratios. Zeolite formation was not observed in any of the present samples. More complex alumina sources such as thermally activated hydrotalcite can also be used to form an inorganic polymer, but under the alkaline synthesis conditions the unused alumina reacts with the poorly crystalline MgO present to re-form hydrotalcite, presumably containing atmospheric carbonate as the interlayer anion. This synthesis method can also potentially be extended to hydroxides other than those of aluminium.
TL;DR: In this paper, a steady-state MSMPR (mixed-suspension mixed-product removal) crystallizer was used for the first time, and the expressions of the nucleation rate, growth rate and the agglomeration kernel of aluminium hydroxide were successfully regressed.
TL;DR: In this article, an in situ X-ray diffraction investigation of goethite-seeded Al(OH)3 precipitation from synthetic Bayer liquor at 343 K has been performed, where the presence of iron oxides and oxyhydroxides in the Bayer process has implications for alumina reversion, which causes significant process losses through unwanted gibbsite precipitation, and also relevant for the nucleation and growth of scale on mild steel process equipment.
Abstract: An in situ X-ray diffraction investigation of goethite-seeded Al(OH)3 precipitation from synthetic Bayer liquor at 343 K has been performed. The presence of iron oxides and oxyhydroxides in the Bayer process has implications for alumina reversion, which causes significant process losses through unwanted gibbsite precipitation, and is also relevant for the nucleation and growth of scale on mild steel process equipment. The gibbsite, bayerite and nordstrandite polymorphs of Al(OH)3 precipitated from the liquor; gibbsite appeared to precipitate first, with subsequent formation of bayerite and nordstrandite. A Rietveld-based approach to quantitative phase analysis was implemented for the determination of absolute phase abundances as a function of time, from which kinetic information for the formation of the Al(OH)3 phases was determined.
TL;DR: In this article, the most probable mechanism function and kinetic parameters of synthetic gibbsite dissolution in NaOH solution were studied using high-pressure differential scanning calorimetry (DSC) equipment with the heating rate of 10 K·min−1.
TL;DR: The crystallization process was found to be quite effective in obtaining alum and the effects on alum formation of various operating conditions, including the amount of potassium or ammonium hydroxide, temperature and seed alum dosage, were examined.
TL;DR: In this article, the formation of an Al(OH)3 (gibbsite) phase after magnetic stirring in water was detected by means of XRD on powdered samples and the Infra Red spectrum of magnetically stirred alumina outgassed at 150°C showed a band at ca. 3300 cm−1, ascribable to the hydroxide phase, which decomposes at higher temperature.
Abstract: This article reports the study of a transition nanometric alumina both as such and after prolonged magnetic stirring in bi-distilled water. Stirring was effective in inducing a significant reduction of starting particles agglomeration and modification of the surface properties of the material. The formation of an Al(OH)3 (gibbsite) phase after magnetic stirring in water was detected by means of XRD on powdered samples. Correspondingly, Infra Red spectrum of magnetically stirred alumina outgassed at 150 °C showed a band at ca. 3300 cm−1, ascribable to the hydroxide phase, which decomposes at higher temperature. Differential thermal analysis and thermogravimetry also showed a different thermal behaviour between the two materials, in that magnetically stirred alumina presents a broad endothermic peak at about 280 °C accompanied by an abrupt mass loss (ca. 0.5% of the initial weight), due to dehydration of the hydroxide phase.
TL;DR: In this article, the dissolution kinetics of pure gibbsite in concentrated sodium hydroxide solutions were studied under ambient pressure and at 60−85 °C, and the changes in morphology of the solid phase were studied by particle size, porosity, and surface area measurements as well as scanning electron microscopy.
Abstract: The dissolution kinetics of pure gibbsite in concentrated sodium hydroxide solutions was studied. The experiments were performed under ambient pressure and at 60−85 °C. The changes in morphology of the solid phase were studied during the reaction by particle size, porosity, and surface area measurements as well as scanning electron microscopy. Reaction rates were observed to be strongly dependent on temperature and hydroxide concentration. Several kinetic models, based on different representation of the surface area of gibbsite, were compared to the experimental data and a good correlation between a model incorporating rough/porous geometry and the experimental data was obtained.
TL;DR: Agarwal et al. as discussed by the authors determined the genesis of reddish Alfisols and black Mollisols formed on uplifted coral reefs in West Timor, Indonesia.