Showing papers on "Gibbsite published in 1975"
TL;DR: In this article, the authors showed that the fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration.
Abstract: Freshly prepared Fe and Al hydrous oxide gels and the amorphous product of heating gibbsite selectively adsorbed traces of Ca and Sr from solutions containing a large excess (∼1M) of NaNO3. The fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration. Significant Ca and Sr adsorption occurred on the Fe and Al gels, and heated gibbsite, at pH values below the points of zero charge (8.1, 9.4, and 8.3±0.1, respectively), indicating specific adsorption. The pH (± 0.10) at which 50% of the Ca was adsorbed (pH50) occurred at pH 7.15 for the Fe gel (0.093M Fe), 8.35 for the Al gel (0.093M Al), and 6.70 for the heated gibbsite (0.181M Al); for Sr, the pH50 values were 7.10, 9.00, and 6.45, respectively. For the Fe gel and heated gibbsite, an empirical model based on the law of mass action described the pH dependence of adsorption reasonably well and suggested that for each Ca or Sr fraction adsorbed, approximately one proton was released. Failure of the Al gel to fit this model may have resulted from its rapid aging.
180 citations
TL;DR: In this article, the incomplete transformation of a boehmite AlO(OH) into a gibbsite AlO (OH)3 during its thermal decomposition is explained with the help of a model involving both a diffusion of hydroxyls either along the "structural channels" of the microcrystal or along the cleavage planes and a desorption of water.
86 citations
01 Jan 1975
TL;DR: In this paper, the aluminum-quercetin ratio was found to be about 10/sup +12.5 after 155 days aging and 481 days aging in a repeated experiment and their solubility corresponded to that found by Hem, Roberson, Lind, and Plzer (1973) for similar aluminosilicate precipitated in the absence of organic solutes.
Abstract: Concentrations of organic matter in the general range of 1-10 milligrams per litre organic carbon are common in natural water, and many naturally occurring organic compounds form aluminum complexes. The aluminum concentrations in near-neutral pH solutions may be 10-100 times higher than the values predicted from solubility data if formation of such organic complexes is ignored. The processes of polymerization of aluminum hydroxide and precipitation of gibbsite are inhibited by the presence of the organic flavone compound quercetin in concentrations as low as 10-5.3 mole per litre. Quercetin forms a complex, with a probable molar ratio of 1.2 aluminum to quercetin, that has a formation constant (beta-2) of about 10/sup +12/. A complex with a higher aluminum-quercetin ratio also was observed, but this material tends to evolve into a compound of low solubility that removes aluminum from solution. In the presence of both dissolved aluminum and aqueous silica, low concentrations of quercetin improved the yield of crystallized kaolinite and halloysite. Small amounts of well-shaped kaolinite and halloysite crystals were identified by electron microscopy in solutions with pH's in the range 6.5-8.5 after 155 days aging in one experiment and 481 days aging in a repeated experiment. The precipitates had aluminum-siliconmore » ratios near 1, and their solubility corresponded to that found by Hem, Roberson, Lind, and Plzer (1973) for similar aluminosilicate precipitated in the absence of organic solutes. The improved yield of crystalline material obtained in the presence of quercetin probably is the result of the influence of the organic compound on the aluminum hydroxide polymerization process. Natural water containing color imparted by organic material tends to be higher in aluminum than would be predicted by pH, silica concentrations, and solubility data for inorganic aluminum species.« less
79 citations
67 citations
TL;DR: In this article, the adsorption characteristics of ortho-phosphate on hydrous γ-Al 2 0 3 from dilute aqueous solution at constant ionic strength (10 −1 M NaCl) is reported.
57 citations
TL;DR: In this article, the adsorption isotherm of a neutral polymer, poly(vinyl alcohol), on the hydrated aluminium oxide gibbsite has been measured, and much higher adorption densities were obtained than have been observed with other colloidal systems.
Abstract: The adsorption isotherm of a neutral polymer, poly(vinyl alcohol), on the hydrated aluminium oxide gibbsite has been measured. Much higher adsorption densities were obtained than have been observed with other colloidal systems. Surface charge measurements indicate that no change either in the isoelectric point or the capacitance of the electrical double layer occurs as a result of the adsorption of the polymer. A large reduction however is observed in the value of the electrophoretic mobility of the gibbsite in the presence of poly(vinyl alcohol). This is attributed to a displacement of the plane of shear by the adsorbed polymer.
53 citations
TL;DR: Li-bearing tosudite has the regularly interstratified structure of montmorillonite and diocta- hedral chlorite in which Li is present in a gibbsite sheet.
Abstract: Lithium-bearing tosudite was found from a brittle clayey part of the Tooho "roseki" deposit, Aichi Prefecture, Japan. The chemical composition of the Li bearing tosudite was estimated as SiO2 41-60%, A120~ 36.40%, Fe203 1.82%, MgO 0.29%, CaO 0.38%, Li20 1.04%, Na20 0-14%, K20 0.38%, H20 + 11'12% and H20- 6.87% from the chemical composition of a specimen with associated impuri- ties. The Li-bearing tosudite has the regularly interstratified structure of montmorillonite and diocta- hedral chlorite in which Li is present in a gibbsite sheet as shown in the structural formula of interlayer cations Ko.t6, Nao.o9, Cao.i3 + 9"60 H20; gibbsite sheet Lil-36, Mgo.14, Feo.45, A13.59 (OH)12.oo; silicate layer A18.oo (Si13.6o, A12.4o) 040.00 (OH) 8-00. The 29-48 A reflection series of the Li-bearing tosudite moves to 31.3 ,~ after ethylene glycol treatment and to 23.3 A on heating to 500~ for 1 hr.
30 citations
TL;DR: In this article, a thermodynamic model that predicts several mineral transformations that can occur in soils is presented. But the model does not consider the effect of pH on the stability of primary and secondary soil minerals.
Abstract: Numerous workers have examined the weathering products of soil minerals and have proposed empirical weathering sequences. The present paper outlines the development of a thermodynamic model that predicts in a systematic way several mineral transformations that can occur in soils. According to this model, the stability of primary minerals increases in the order: Na-glass, K-glass, pyroxene, analcime, anorthite, low albite, muscovite, microcline, and quartz. The stability of secondary clay minerals depends on soluble silica. At pH 6 with high silica (≃ 10⁻³M) the order of increasing stability is: chlorite, halloysite, gibbsite, illite, dickite, beidellite, kaolinite, and montmorillonite; at low silica (≃ 10⁻⁵M) the order is: chlorite, halloysite, illite, beidellite, montmorillonite, dickite, kaolinite, and gibbsite. The stability of both primary and secondary minerals increases with pH. The observed weathering of volcanic ash agrees well with the predictions of this model. The model makes use of important thermodynamic data accumulated for soil minerals and helps to pinpoint deficiencies in these data. The need to examine the kinetics of mineral transformations in soils in greater detail also becomes obvious from this model.
19 citations
TL;DR: In this article, Montmorillonite clay samples were coated with 16 m-equiv/g of clay or iron plus aluminum as hydrous oxides and aged 1 yr, in suspensions of pH 6 or 8.
Abstract: Montmorillonite clay samples were coated with 16 m-equiv/g of clay or iron plus aluminum as hydrous oxides and aged 1 yr, in suspensions of pH 6 or 8. The magnesium exchange capacity (MgEC) decreased linearly with the amount of non-crystalline aluminum hydrous oxide associated with the clay. Eight to 16 m-equiv of iron per g of clay reduced the MgEC by 20 m-equiv/100g at pH 6, but did not affect the MgEC at pH 8. The quantity of non-crystalline aluminum associated with the clay depended on the suspension pH and aging time, and was unaffected by the coprecipitation of 8–16 m-equiv of iron hydrous oxide/g clay. The crystalline form of aluminum hydrous oxide depended on the suspension pH and was shown by X-ray diffraction to be gibbsite at pH 6 and bayerite at pH 8. Gibbsite and bayerite formed rapidly with a rate dependent on the suspension pH when excess non-crystalline aluminum hydrous oxides were present. The quantity of non-crystalline aluminum hydrous oxides remaining after one year in suspensions of iron hydrous oxides and montmorillonite varied from 2·3 m-equiv/g of montmorillonite at pH 8-4·0 m-equiv/g of montmorillonite at pH 6. Differential thermal analysis and MgEC measurements indicated some regular organization of the iron hydrous oxides, however, crystalline iron minerals were not detected by X-ray diffraction.
18 citations
TL;DR: In this paper, a contrasting occurrence of clay minerals was found within a soil profile which was derived from volcanic materials in the suburbs of Fukuoka-city, Northern Kyushu.
Abstract: A contrasting occurrence of clay minerals was found within a soil profile which was derived from volcanic materials in the suburbs of Fukuoka-city, Northern Kyushu. The soil profile is located on an isolated terrace, and the morphological characteristics of the soil correspond exactly to Andosols, so-called Kuroboku soils or Humic Allophane soils. The clay fraction of upper horizons of the soil consists largely of alumina-rich gel-like materials, gibbsite, and layer silicates such as chlorite and chloritevermiculite intergrades, while that of lower horizons is composed of allophane and gibbsite or halloysite. There was no positive indication of allophane in the upper horizons. Corresponding with the clay mineralogical composition, quartz is abundant in the fine sand fraction of the upper horizons, while the mineral is very scarce or none in the lower horizons, suggesting a close relation between the petrological nature of parent volcanic materials and the mineralogical composition of weathering p...
18 citations
TL;DR: In this article, the authors determined the mineralogical composition of six highly weathered soils of the Central Plateau of Brazil and showed that the sand content (predominantly quartz) was not related to the relative amounts of gibbsite and kaolinite in the clay ( < 2 #m) fractions.
Abstract: Determination of the mineralogical composition of six highly weathered soils of the Central Plateau of Brazil showed that the sand content (predominantly quartz) was not related to the relative amounts of gibbsite and kaolinite in the clay ( < 2 #m) fractions. The latter is in agreement with kinetic considerations of the involved mineral species, but in disagreement with thermodynamic considerations. However, that dissolution of quartz has been operative in these soils is indicated by an excellent relationship (r 2 = 0.96) between the amount of sand-size quartz and the reactive SiOe content of the clay fractions.
01 Jan 1975
TL;DR: Aqueous aluminum solutions containing 4.5 x 10/sup -4/ molar aluminum in 0.01 molar NaClO/sub 4/ were partly neutralized with NaOH to give OH:AL mole ratios from 1.40 to 2.76.
Abstract: Aqueous aluminum solutions containing 4.5 x 10/sup -4/ molar aluminum in 0.01 molar NaClO/sub 4/ were partly neutralized with NaOH to give OH:AL mole ratios from 1.40 to 2.76. Measured amounts of montmorillonite, kaolinite, volcanic ash, or feldspathic sand were added to provide an area of inert surface. Reactions that occurred during 100 days of aging were compared with those in similar solutions without added surfaces, studied in earlier work. Adsorption of monomeric species Al(H/sub 2/O)/sub 6//sup +3/, AlOH(H/sub 2/O)/sub 5//sup +2/, and Al(OH/sub 2/)(H/sub 2/O)/sub 4//sup +/ on the added surfaces follows a cation exchange mass law equilibrium model, and adsorption is essentially complete in 1 hour. Only minor changes in monomeric aluminum species occurred after that. Rapid adsorption of polynuclear aluminum hydroxide species also occurs and follows the pattern of the Langmuir adsorption isotherm. In the absence of surfaces, the polynuclear ions slowly increase in size and become microcrystalline gibbsite during aging. Electron micrographs showed microcrystalline gibbsite was present on surfaces after aging only 2 days. However, the analytical data suggest this material must have been adsorbed after it had already attained a near-crystalline state. Adsorbed polynuclear aluminum hydroxide species were not extensively converted to microcrystalline gibbsite duringmore » 100 days of aging.« less
Patent•
22 May 1975
TL;DR: In the production of alumina by the Bayer process from bauxite containing gibbsite and boehmite and having an iron content below 5% (calculated as Fe2O3) the extraction of bohemite is improved by introducing lime during, preferably at the beginning of, the digestion stage which is carried out at a temperature of 225-270°C.
Abstract: A B S T R A C T In the production of alumina by the Bayer process from bauxite containing gibbsite and boehmite and having an iron content below 5% (calculated as Fe2O3) the extraction of boehmite is improved by introducing lime during, preferably at the beginning of, the digestion stage which is carried out at a temperature of 225-270°C.