Showing papers on "Goethite published in 1979"
TL;DR: In this paper, the authors established that mycorrhiza increased the availability of phosphate at a level of about 0.5-2 μm P (60-70% coverage of the goethite surface).
Abstract: Pot trials using phosphated-goethite (bridging complex) as the source of P for ryegrass were established. No P was readily available to ryegrass until the surface was >40% covered with phosphate ions. Availability increased as the P level in solution increased up to 2 μM. Maximum availability was attained when the initial concentration of P in solution was 2 μM which occurred at about 75% coverage on geothite. Mycorrhiza increased the availability of phosphate at a level of about 0.5–2 μM P (60–70% coverage of the goethite surface).
133 citations
TL;DR: The reaction products and the accompanying sulfur isotope fractionations during the reaction of H 2 S with goethite in aqueous media at 22-24°C for periods from 0.5 hr to 65 days were studied as mentioned in this paper.
131 citations
TL;DR: In this article, chemical data for 56 elements in soils from three regions of Brazil (Bahia, Amazon, Goias) indicate that intense chemical weathering leads to a product soil essentially in the system, SiO2Al2O3Fe2O 3H2O. The major minerals of the leached soils are quartz, kaolinite, gibbsite, goethite and hematite.
123 citations
TL;DR: In this article, it was shown that on exposure of goethite to deuterium oxide vapour, the latter underwent rapid isotopic exchange to give the corresponding surface deuteroxyl groups.
Abstract: Infrared spectra of goethite (α-FeOOH) exhibited bands which have been assigned to OH stretching vibrations of bulk or surface hydroxyl groups. On exposure of goethite to deuterium oxide vapour the latter underwent rapid isotopic exchange to give the corresponding surface deuteroxyl groups. The conversion of bulk hydroxyl groups to bulk deuteroxyl groups by contact between deuterium oxide vapour and goethite was comparatively slow. Analogous conclusions were drawn from spectra of deuterated goethite (α-FeOOD) before and after treatment with water vapour. The decomposition of geothite to haematite (α-Fe2O3) by heat treatment in vacuo or in an oxygen atmosphere has been briefly investigated.
94 citations
TL;DR: In this article, Ferrihydrite was transformed to goethite and/or hematite at various temperatures, (OH), and IAl, and a straight line was obtained for all preparations independent of (OH).
Abstract: Ferrihydrite was transformed to goethite and/or hematite at various temperatures, (OH), and IAl). Increasing temperature and (AI) favored hematite, increasing (OH) favored goethite. A given (AI) induces hematite more effectively at lower (OH). AI substitution in goethites increased linearly with log(All, but was independent of temperature. At a givea (All, substitution increased with decreasing (OH). In a plot of AI/Fe in the goethite against (AI)/(Fe(OH)C) in solution a straight line was obtained for all preparations independent of (OH).
89 citations
TL;DR: Biotite in deeply weathered granitic rocks in southwestern Australia has altered to exfoliated grains composed of biotite, mixed-layer clay minerals, kaolinite, vermiculite, gibbsite, goethite, and hematite as discussed by the authors.
Abstract: Biotite in deeply weathered granitic rocks in southwestern Australia has altered to exfoliated grains composed of biotite, mixed-layer clay minerals, kaolinite, vermiculite, gibbsite, goethite, and hematite. Discrete vermiculite and vermiculite-dominant mixed-layer clay minerals are not major weathering products. Oxidation of octahedral iron in biotite is associated with ejection of octahedral cations, loss of interlayer K, and a contraction of the b-dimension of the biotite sheet. Si, Mg, Ca, Mn, K, and Na are lost from biotite during weathering, and Ti, Al, Ni, and Cr are retained. Fe and water have been added to the grains during weathering. Much Fe occurs as aggregates of microcystalline, aluminum-rich goethite particles on flake surfaces and within etchpits, with smaller amounts occurring as hexagonal arrangements of lath-shaped crystals of goethite on flake surfaces.
76 citations
TL;DR: Aluminium substituted goethites (Fe, AI) OOH were synthesized from Fe(III), A1 systems (ferrihydrites) in M KOH at room temperature as discussed by the authors.
Abstract: Aluminium substituted goethites (Fe, AI) OOH were synthesized from Fe(III), A1 systems (ferrihydrites) in M KOH at room temperature. A linear correlation existed between degree of AI substitution and log(A1) in solution. Incorporation of up to 12 mole ~ AI was obtained. The rate of conversion of ferrihydrite to goethite decreased as (A1) increased. The goethite consisted of thin elongated plates approximately 0.1/zm long with serrated edges and reduced growth in the crystallographic X-direction. The presence of salts and the nature of the starting material either an Al-ferrihydrite or a ferrihydrite in aluminate solution did not influence the degree of substitution, but only the rate of formation of the goethite.
58 citations
TL;DR: In this article, it was shown that the satellites observed in the diffraction pattern of the dehydrated single crystal of the mineral goethite are better interpreted in terms of small angle scattering by a "texture" of the dehydration product hematite.
49 citations
TL;DR: The presence of Al-bearing goethites has been unequivocally established in Venezuelan laterite sediments by means of infrared spectroscopy (IR), chemical dissolution, and X-ray powder diffraction (XRD) methods as discussed by the authors.
Abstract: The presence of Al-bearing goethites has been unequivocally established in Venezuelan laterite sediments by means of infrared spectroscopy (IR), chemical dissolution, and X-ray powder diffraction (XRD) methods. The composition of these samples ranges from (Fe0.agA10,11)O(OH) to (Fe0.r~A10.24)O(OH). The data of dissolution experiments using a modified dithionite (CDB) treatment suggest a parallel behavior between Fe and A1; the gradual dissolution of A1 is associated with the destruction of the Al-containing goethite. The interpretation of the CDB dissolution results for SiO~/Fe2Oz is different; silica was only slight- ly extracted from phases other than goethite. Substitution of Fe a§ by AP + in these goethites was represented on the XRD patterns by a lowering of the (110) and (111) reflections corresponding to a reduction in size of the unit cell of goethite. IR spectroscopy showed the formation of such solid solutions by a shift of the 405 cm -1 absorption band, assigned to v (Fe-O) in synthetic goethite, to >460 cm -~ in the spectrum of AI- bearing natural goethite. Moreover, this spectrum shows a shift of the 3140 cm -~ absorption, due to v (OH), to higher frequencies, indicating a H-bond weakening in (FexA1c~_~)O(OH) compared to FeO(Ot-I).
46 citations
TL;DR: In this article, the reversibility of the adsorption of phosphate on goethite was measured by diluting suspensions of goetheite on which phosphate was adsorbed with large volumes of phosphate-free solution at the same ionic strength.
Abstract: Summary
The reversibility of the adsorption of phosphate on goethite was measured by diluting suspensions of goethite on which phosphate was adsorbed with large volumes of phosphate-free solution at the same ionic strength. The effect on the reversibility of various adsorption and desorption conditions was studied, particularly pH, temperature, ionic strength and time of reaction.
The apparent irreversibility of the adsorption reaction seems to be due to a slow adsorption reaction of part of the phosphate after a very rapid initial adsorption, with a similar behaviour when the phosphate is desorbed. When the total adsorption plus desorption time is long enough, both adsorption and desorption points tend to lie on a single curve which corresponds to the isotherm calculated according to the Stern double-layer theory.
46 citations
TL;DR: The surface charge density/pH function of goethite is shown to be very similar to the surface charge densities/surface potential functions reported for mercury as mentioned in this paper, and this finding differs from all other reports and they attribute the difference to the experimental method.
TL;DR: In this article, single grain X-ray and electron diffraction patterns of weathered biotite flakes exhibit groupings of 001 and hk reflections of Biotite, vermiculite, mixed-layer clay minerals, and kaolinite indicating that the secondary minerals are in parallel crystallographic orientation to the parent biotites.
Abstract: Single grain X-ray and electron diffraction patterns of weathered biotite flakes exhibit groupings of 001 and hk reflections of biotite, vermiculite, mixed-layer clay minerals, and kaolinite indicating that the secondary minerals are in parallel crystallographic orientation to the parent biotite. Asterism of biotite reflections is enhanced by weathering. Gibbsite crystals developed in parallel basal orientation to biotite flakes. Most goethite in weathered biotite occurs as aggregates of randomly oriented crystals in cleavages and on grain surfaces. Some goethite is present on micaceous fragments as 0.05-μm size, lathlike crystals in a hexagonal arrangement with their (100) face resting on the (001) biotite face. Selected area electron diffraction patterns of aggregates of lathlike goethite crystals contain 0kl, 1l, and 2l reflections due to undulation of the aggregates and the extreme thinness of the crystals. These patterns indicate that the close packed anion layers in goethite coincide with the brucite-like layer of the micaceous minerals.
TL;DR: In this article, the authors examined several soils in detail by electron microscope and microprobe to assess the nature of clay size particles and microaggregates and determined their morphology, analytical composition, identity and association between particles.
Abstract: Several soils were examined in detail by electron microscope and microprobe to assess the nature of clay size particles and microaggregates. Morphology, analytical composition, identity and association between particles were determined. Of the mineral oxides, pellets of goethite and hematite about 1 µm in size were most distinctive. They were found in all the soils examined except one. They contained both aluminium and silicon, sometimes in fairly constant proportions, but the presence of adhering fine material made it difficult to assess the extent to which these elements were part of the iron oxide structure. Discrete gibbsite particles of micron size were rarely encountered, although some soils contained appreciable quantities of it in much smaller form. At least a few rutile or anatase particles were found in all soils, while they were common in some. They also were usually contaminated by surface deposits, in contrast to ilmenite and quartz grains which were always relatively clean and were often isolated from other particles. The ratios of ironltitanium in ilmenites were well defined but different from soil to soil. Uncontaminated clay mineral particles were rare. Most had substantial deposits of fine-grained material upon their surfaces, much of it < 200 A in diameter. The most easily detected components of these surface deposits were goethite and hematite, and often they were dominant. Finely divided clay minerals were usually present as well, together in some soils with gibbsite and occasionally with titanium oxides. In one soil where coarser (1 µm) host particles were not readily available to carry it, the fine-grained material formed microaggregates consisting of kaolin, gibbsite and hematite, all of comparable size. Soils containing both kaolin and illite were composed mainly of compact microaggregates of the two clay minerals, which had the appearance of single particles. These results demonstrate the close association frequently existing between micron and submicron soil particles and between submicron particles themselves. The structural units of soil particles were often much smaller than generally supposed.
TL;DR: In this article, a laboratory study of gossan formation has been made by anodically weathering supergene Ni ores in a circulating flow tank specially devised to simulate natural processes.
TL;DR: In this paper, it was shown that on exposure of goethite to deuterium oxide vapour, the latter underwent rapid isotopic exchange to give the corresponding surface deuteroxyl groups.
Abstract: Infrared spectra of goethite (α-FeOOH) exhibited bands which have been assigned to OH stretching vibrations of bulk or surface hydroxyl groups. On exposure of goethite to deuterium oxide vapour the latter underwent rapid isotopic exchange to give the corresponding surface deuteroxyl groups. The conversion of bulk hydroxyl groups to bulk deuteroxyl groups by contact between deuterium oxide vapour and goethite was comparatively slow. Analogous conclusions were drawn from spectra of deuterated goethite (α-FeOOD) before and after treatment with water vapour. The decomposition of geothite to haematite (α-Fe2O3) by heat treatment in vacuo or in an oxygen atmosphere has been briefly investigated.
TL;DR: The alteration of the limestone into parent material is described and discussed in this article, where chemical and mineralogical analyses of the solid materials and the chemical analyses of interstitial waters permit the following conclusions about the parent materials: decalcification and desilication have occurred; low-ordered tridymite has been formed by replacement of the carbonates which, together with plagioclases and magnesite (Mg-calcite), have subsequently been transformed into smectite and kaolinite.
Patent•
20 Sep 1979
TL;DR: An alkali hydroxide is added to an aqueous solution of ferrous salt to form a precipitate and a part of the solution is separated to control a ratio of an anion to a ferrous component to less than 1 as mentioned in this paper.
Abstract: An alkali hydroxide is added to an aqueous solution of ferrous salt to form a precipitate and a part of the solution is separated to control a ratio of an anion to a ferrous component to less than 1 and the ferrous component is oxidized to acicular goethite by bubbling air through the supernatant and precipitate.
Journal Article•
TL;DR: Montmorillonite/dioctahedral-vermiculite interstratified mineral and mica minerals are dominant in two Low-Humic Gley soils and a Ground-Water Laterite soils, respectively, although kaolin minerals are predominant in many lowland soils.
Abstract: The outline of the mineral composition in the clay fraction of some typical soils occurring in the Brazilian Amazon region is as follows: In the soils with oxic B horizon, Yellow Latosols, Red-Yellow Latosols and "Latosols Roxo" Soil, kaolinite is predominant, goethite and haematite are found in general, an gibbsite is frequently detected. A small amount or trace of mica minerals occur in several lateritic soils. The presence of the other 2:1-type clay minerals is rare in the lateritic soils. In Red-Yellow Podzolic soils, kaolinite is also predominant, and iron-oxide minerals are always identified. Considerable amount of gibbsite and small amounts of mica minerals and dioctaliedral vermiculite are present in some of these solis. In fite so-called "Terra Roxa Estruturada" soils, kaolin minerals are dominant, but considerable amounts of iron-oxide minerals are found in the clay fraction, so that haematite is especially rich. Metahalloysite is a dominant clay mineral in a "Terra Roxa Estruturada" Soil. A small amount of dioctahedral vermiculite is present in the other soils. The clay mineral composition of the low land soils is a little complicated. Montmorillonite/dioctahedral-vermiculite interstratified mineral and mica minerals are dominant in two Low-Humic Gley soils and a Ground-Water Laterite soils, respectively, although kaolin minerals are predominant in many lowland soils. Small amounts of 2:1-type clay minerals are frequently detected in the other lowland soils. Quartz exists in the clay fraction of all the soil samples.
TL;DR: In this paper, the results of experiments are presented in which Ni, Co, Cu, Co and Fe(II) ions in agar gel are allowed to diffuse under the influence of oxygen and metal concentration gradients and to interact with the surfaces of goethite, serpentine, magnesite and talc.
Patent•
09 Oct 1979
TL;DR: In this paper, the ratio of anion such as sulfate ion or the like to ferrous ion in an aq. soln is regulated to a predetermined pH and temp. to considerably shorten the reaction time.
Abstract: PURPOSE:To produce needle-like goethite of a small particle size by regulating the ratio of anion such as sulfate ion or the like to ferrous ion in an aq. soln. of ferrous sulfate or the like to below 1 and oxidizing the regulated soln. at a predetermined pH and temp. to considerably shorten the reaction time. CONSTITUTION:FeSO4 7H2O is adjusted to pH>=11 with a alkali such as NaOH, and the ratio of sulfate ion to ferrous ion is regulated to below 1. The regulated FeSO4 7H2O is then oxidized by blowing air or the like. The resulting needle-like goethite is small in particle size, and gamma-Fe2O3 made of the goethite is also small in particle size and exhibits more superior magnetic characteristics than those of a conventional product.
Patent•
05 Oct 1979
TL;DR: In this article, an improved process for accelerating the digestion process in the Bayer alumina process is provided which promotes both the goethite-hematite conversion and a more perfect and quick dissolution of the diaspore.
Abstract: An improved process for accelerating the digestion process in the Bayer alumina process is provided which promotes both the goethite-hematite conversion and a more perfect and quick dissolution of the diaspore. The above is achieved by carrying out the digestion in the process of 5-20% by weight calculated on the dry weight of the bauxite of a novel hydrogarnet catalyst.
Journal Article•
TL;DR: The series of aluminium oxo minerals such as gibbsite, boehmite, and corundum as well as iron minerals lepidocrocite, goethite, and hematite dissolve in acetylacetone with decreasing extraction rate as the mineral density increases as mentioned in this paper.
Abstract: The series of aluminium oxo minerals such as gibbsite, boehmite,
diaspore, and corundum as well as iron minerals lepidocrocite,
goethite, and hematite dissolve in acetylacetone with decreasing
extraction rate as the mineral density increases along each series
listed above. The observed inverse dependence of the digestion rate
on the mineral density for each series studied and the mechanism
of digestion have been discussed.