scispace - formally typeset


About: Gibbsite is a(n) research topic. Over the lifetime, 1995 publication(s) have been published within this topic receiving 48355 citation(s). The topic is also known as: hydrargillite & zirlite. more

More filters

Journal ArticleDOI
Abstract: At the solid/solution interface of metal (hydr)oxides various types of O(H) and OH(H) groups are present, which differ in the number of coordinating metal ions. The σ 0 -pH curves of metal (hydr)oxides are strongly determined by the composition and the relative extent of the various crystal planes of (hydr)oxides. The charging behavior is discussed for gibbsite (Al(OH) 3 ), goethite (FeOOH), hematite (Fe 2 O 3 ), rutile (TiO 2 ), and silica (SiO 2 ). New experimental σ 0 -pH data for goethite and gibbsite are presented. Several important (hydr)oxides exhibit crystal faces which do not develop surface charge over a relatively wide pH range. An uncharged crystal face may be due to the presence of surface groups which are not reactive (inert) in the pH range under consideration, like the 001 face of gibbsite and the 0001 face of hematite, or caused by the presence of two types of interacting charged surface groups of which the charge of one type is fully compensated by the other like at the 100 face of goethite. The charging behavior of silica and the 001 face of gibbsite is determined by one type of reactive surface group with a large Δ p K for the consecutive protonation steps. The crystal structure imposes the presence of uncharged surface groups and this results in a quite different shape of σ 0 -pH curves for gibbsite and silica in comparison with the commonly observed σ 0 -pH curves of metal (hydr)oxides. The MUltiSIte Complexation (MUSIC) model as developed by T. Hiemstra, W. H. Van Riemsdijk, and G. H. Bolt, ( J. Colloid Interface Sci. 132 (1989)) leads to a rather good prediction of σ 0 -pH curves for various metal (hydr)oxides using predicted affinity constants for the various types of surface groups and Stern layer capacitance values and pair formation constants estimated from the literature. more

714 citations

Journal ArticleDOI
Darrell Kirk Nordstrom1Institutions (1)
Abstract: While gibbsite and kaolinite solubilities usually regulate aluminum concentrations in natural waters, the presence of sulfate can dramatically alter these solubilities under acidic conditions, where other, less soluble minerals can control the aqueous geochemistry of aluminum. The likely candidates include alunogen, Al 2 (SO 4 ) 3 · 17H 2 O, alunite, KAl 3 (SO 4 ) 2 (OH) 6 , jurbanite, Al(SO 4 )(OH) · 5H 2 O, and basaluminite, Al 4 (SO 4 )(OH) 10 · 5H 2 O. An examination of literature values shows that the log K sp = −85.4 for alunite and log K sp = −117.7 for basaluminite. In this report the log K sp = −7.0 is estimated for alunogen and log K sp = −17.8 is estimated for jurbanite. The solubility and stability relations among these four minerals and gibbsite are plotted as a function of pH and sulfate activity at 298 K. Alunogen is stable only at pH values too low for any natural waters ( pH up to the range of 3–5 depending on sulfate activity. Alunite is stable at higher pH values than jurbanite, up to 4–7 depending on sulfate activity. Above these pH limits gibbsite is the most stable phase. Basaluminite, although kinetically favored to precipitate, is metastable for all values of pH and sulfate activity. These equilibrium calculations predict that both sulfate and aluminum can be immobilized in acid waters by the precipitation of aluminum hydroxysulfate minerals. Considerable evidence supports the conclusion that the formation of insoluble aluminum hydroxy-sulfate minerals may be the cause of sulfate retention in soils and sediments, as suggested by Adams and Rawajfih (1977), instead of adsorption. more

410 citations

Journal ArticleDOI
Abstract: Sorption and desorption of AsO 4 on or from different soil components may have a dominant role in regulating As mobility in soils. The objectives of this work were to provide information on the factors that influence the competitive sorption of AsO 4 and PO 4 in soil. We studied the competitive sorption of PO 4 and AsO 4 on selected phyllosilicates, metal oxides, synthetic organo-mineral complexes, and soil samples as affected by pH (4.0-8.0), ligands concentration, surface coverage of the oxyanions on the samples and the residence time. We found that Mn, Fe, and Ti oxides and phyllosilicates particularly rich in Fe (nontronite, ferruginous smectites) were more effective in sorbing AsO 4 than PO 4 . In fact, by adding AsO 4 and PO 4 as a mixture (AsO 4 /PO 4 molar ratio of 1) more AsO 4 , than PO 4 was usually sorbed on birnessite, pyrolusite, goethite, nontronite, and ferruginous smectite, but more PO 4 than AsO 4 was sorbed on noncrystalline Al precipitation products, gibbsite, boehmite, allophane, and kaolinite. For example, at pH 5.0 the sorbed AsO 4 /sorbed PO 4 molar ratio (rf) was 1.81 for bimessite, 1.05 for nontronite, but was only 0.45 for kaolinite and 0.14 for allophane. For montmorillonite, illite, and vermiculite the rf values were slightly <1. For soil samples, particularly rich in kaolinite, halloysite, allophane, and containing relatively large amounts of organic C, the rf values were usually much <1. For all the samples, the rf values increased by decreasing the pH and with the residence time of the oxyanions. The sorption of AsO 4 (or PO 4 ) on goethite and gibbsite decreased by increasing the initial PO 4 /AsO 4 (or ASO 4 / PO 4 molar ratio) up to 2.0. However, PO 4 inhibited AsO 4 sorption more on gibbsite than on goethite, whereas AsO 4 prevented PO 4 sorption more on goethite than on gibbsite. The data reported in this paper suggest that the mobility, the bioavailability, and the toxicity of As in soil environments may be greatly affected by the nature of soil components, pH, presence of anions (PO 4 ), and residence time. more

373 citations

Journal ArticleDOI
15 Apr 2006-
TL;DR: The chemical compositions based on the XPS survey scans were in good agreement with the expected composition and a distinction could be made between boehmite and pseudoboehmitebased on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudobOEhmite. more

Abstract: Synthetic corundum (Al2O3), gibbsite (Al(OH)3), bayerite (Al(OH)3), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution Al2p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the O1s high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite. more

332 citations

Journal ArticleDOI
Abstract: Solubility curves were determined for a synthetic gibbsite and a natural gibbsite (Minas Gerais, Brazil) from pH 4 to 9, in 0.2% gibbsite suspensions in 0.01 M NaNO3 that were buffered by low concentrations of non-complexing buffer agents. Equilibrium solubility was approached from oversaturation (in suspensions spiked with Al(NO3)3 solution), and also from undersaturation in some synthetic gibbsite suspensions. Mononuclear Al ion concentrations and pH values were periodically determined. Within 1 month or less, data from over-and undersaturated suspensions of synthetic gibbsite converged to describe an equilibrium solubility curve. A downward shift of the solubility curve, beginning at pH 6.7, indicates that a phase more stable than gibbsite controls Al solubility in alkaline systems. Extrapolation of the initial portion of the high-pH side of the synthetic gibbsite solubility curve provides the first unified equilibrium experimental model of Al ion speciation in waters from pH 4 to 9. The significant mononuclear ion species at equilibrium with gibbsite are Al3+, AlOH2+, Al(OH)+2 and Al(OH)−4, and their ion activity products are ∗K50 = 1.29 × 108, ∗Ks1 = 1.33 × 103, ∗Ks2 = 9.49 × 10−3 and ∗Ks4 = 8.94 × 10−15. The calculated standard Gibbs free energies of formation (ΔG°f) for the synthetic gibbsite and the A1OH2+, Al(OH)+2 and Al(OH)−4 ions are −276.0, −166.9, −216.5 and −313.5 kcal mol−1, respectively. These ΔG°f values are based on the recently revised ΔG°f value for Al3+ (−117.0 ± 0.3 kcal mol−1) and carry the same uncertainty. The ΔG°f of the natural gibbsite is −275.1 ± 0.4 kcal mol−, which suggests that a range of ΔG°f values can exist even for relatively simple natural minerals. more

317 citations

Network Information
Related Topics (5)

4K papers, 166.8K citations

90% related
Clay minerals

10.1K papers, 271.8K citations

89% related

8.5K papers, 224.5K citations

88% related

7.9K papers, 219.2K citations

87% related

825 papers, 31.9K citations

86% related
No. of papers in the topic in previous years

Top Attributes

Show by:

Topic's top 5 most impactful authors

Robert Gilkes

18 papers, 374 citations

Kevin M. Rosso

14 papers, 170 citations

Xin Zhang

10 papers, 122 citations

Donald L. Sparks

9 papers, 948 citations

Jonas Addai-Mensah

8 papers, 169 citations