Showing papers on "Goethite published in 1970"

Reduction of iron oxide minerals by a marine Bacillus

Abstract: Bacillus 29, previously isolated from a ferromanganese nodule, and a derivative strain,Bacillus 29A, were examined for their iron-solubilizing ability when reducing limonite, goethite and hematite with glucose.Bacillus 29A was the more active of the two cultures. It solubilized larger amounts of iron from limonite and goethite than from hematite. Several lines of evidence indicated that the mechanism by whichBacillus 29A carried out iron solubilization from limonite involved enzymatic reduction of the ferric iron in the mineral. Phenosafranin enhanced the reduction of the iron oxides by growing cultures, but anaerobiosis did not.

The mineralogy of tropical weathering illustrated by some west malaysian soils

Abstract: Summary The mineralogy of the processes leading to the formation of soils by the tropical weathering and leaching of rocks is reviewed, and illustrated by the results of an investigation into the formation, mineralogy and plasticity properties of some soils formed on basalt, granite, shale and sandstone in west Malaysia. It is shown that hydrolysis followed by differential solution can account for the formation of the samples studied. Kaolinite was always present and generally the dominant clay mineral, although it gave place to gibbsite under severe weathering, and illite was also present in some of the less weathered soils on granite and shale. Quartz was prominent in soils on granite and sedimentary rocks, which are rich in this mineral. Iron oxide generally occurred, usually as goethite in the soils but as hematite in the nodules which were generally present in the soils selected for study, although gibbsite (hydrated aluminium oxide) was the main constituent of the nodules in one case. The observed mineralogical composition and clay content of the soils are consistent with the range of plasticity properties observed. The activity of some soils was reduced by the presence of gibbsite or goethite in the clay-sized fraction.

A re-examination of the stability of goethite on Mars

Abstract: Goethite stability on Mars, considering dehydration-rehydration cycle and time average atmospheric water vapor content

Iron Alkoxide Obtained by Reacting Iron Oxides with Glycerol

Abstract: Goethite, lepidocrocite and hematite were reacted with glycerol and reaction products were studied at various steps of the reaction. After a treatment of 16 hr at 245°C the final form of the reaction product, a deep green soft solid, was obtained whatever the starting material. According to hydrolysis and chemical analysis, the reaction product can be identified as iron alkoxide. Hydrolysis of the solid by boiling water yielded glycerol and a strongly magnetic material characterized by a spinel structure like maghemite and magnetite.

Micromorphology of some tropical alluvial clay soils

Abstract: Summary The micromorphological properties of some marine and estuarine tropical clays from Holocene coastal plain soils of Surinam and Thailand have been explained against the background of sedimentation and initial soil formation. During geogenesis stratified sediments are formed, above which are sediments with slightly disturbed stratification, with or without matric faecal pellets. Pedogenesis during the sedimentation phase included development of channels in the sediment, formation of channel neostrians, biological homogenization, possibly pyrite accumulation, and partial oxidation and precipitation of iron as ferric hydroxide. During the brackish water phase pyrite accumulates in various amounts, mass illuviation may occur, part of the iron may oxidize and precipitate and part of the pyrite may be oxidized. During and after the swamp phase further oxidation and precipitation of iron as ferric hydroxide occurs, ferric hydroxide crystallizes into goethite. Pyrite becomes oxidized, resulting in the formation of jarosite, gypsum, silica, and ferric hydroxide.

Alpine podzol soils on the ben lawers massif perthshire

Abstract: Summary Characteristics of the soils include well-defined horizons, very low pH values and base saturation percentages, and a slight but general increase in the silt-plusclay content down the profile. X-ray diffraction shows that the soil clays are rich in mica and chlorite with subsidiary amounts of kaolinite, goethite, and lepidocrocite. The general distribution of the clay minerals in the profiles studied suggests that the weathering of chlorite leads to the formation of kaolinite in the A horizons and to the accumulation of crystalline iron-oxide minerals in the B horizons. The presence of kaolinite, taken in conjunction with recent clay mineral studies of Scandinavian and Canadian podzols, indicates that the Ben Lawers soils may pre-date the last glacial period.

Extraction of alumina from ores

Abstract: Alumina in increased yeild is recovered from aluminiferous ores containing titanium and also iron in goethite phase by subjecting the ores to a wet caustic digestion step at temperatures in excess of about 280 DEG C in admixture with a calcium compound added in an amount at least sufficient to convert substantially all of the titanium to a calcium-titanium compound for a time sufficient to accomplish the conversion of goethite to hematite followed by conventional alumina recovery steps.

Spectral Studies of Materials Possibly Present on the Martian Surface

Abstract: : Comparing the reflectance spectra of synthetic mixtures with the observed spectrum of Mars has been continued to develop mixtures congruous with the Martian soil so that limits may be set on its composition. Mixtures containing various amounts of the iron oxides goethite and hematite precipitated on finely ground quartz and kaolin show the features of the Martian spectrum after the addition of dark materials such as magnetite or hornblende. The effect of temperature, particle size and iron oxide content on the spectra of the mixture components was examined. At low temperatures (-190C) spectral features are detectable. A synthetic material of particle size less than 37 microns is required to give a proper match to the Martian spectrum. The spectra of mixtures containing in the vicinity of 10% iron oxides do not seem to be highly sensitive to the total iron oxide content. (Author)

Reductive dissolution of goethite and pyrolusite in alkaline solution

Abstract: The s e l e c t i v e d i s s o l u t i o n of p y r o l u s i t e (MnC^) i n presence of goethite (FeO.OH) i n aqueous ammoniacal ammonium carbamate s o l u t i o n has been investigated; various reducing agents were studied, i n p a r t i c u l a r sodium s u l f i t e (Na^SO^) and hydrazine hydrate (N^H^.H^O). Sodium s u l f i t e was found to be an unsatisfactory reducing agent for both goethite and p y r o l u s i t e , f or the leaching rate decreased s t e a d i l y with time to an impractical l e v e l because of the l i m i t e d s o l u b i l i t y of the reactions products. Hydrazine hydrate was an e f f e c t i v e reducing agent for p y r o l u s i t e even at low temperature, whereas goethite required much higher temperatures f o r any appreciable d i s s o l u t i o n . A one hour leach at 35°C dissolved 90 per cent of the p y r o l u s i t e but only 0.1 per cent of the goethite. Additions of ammonium phosphate had no e f f e c t on the rates, there being no phosphate detected i n the leach l i q u o r . An a c t i v a t i o n energy of 17.0 K cal/mole was found for the d i s s o l u t i o n of p y r o l u s i t e with hydrazine. A r e a c t i o n mechanism f o r the leaching of p y r o l u s i t e with hydrazine was proposed i n which a reduction reaction on the surface of the mineral was the rate-determining step. I t was possible to recover manganese from s o l u t i o n with oxygen as an amorphous Mn0„ p r e c i p i t a t e .