Showing papers on "Goethite published in 1981"

Dissolution of Iron Oxides and Oxyhydroxides in Hydrochloric and Perchloric Acids

Abstract: The dissolution of synthetic magnetite, maghemite, hematite, goethite, lepidocrocite, and ak- aganeite was faster in HCI than in HCIO4. In the presence of H § the C1- ion increased the dissolution rate, but the 004- ion had no effect, suggesting that the formation of Fe-Cl surface complexes assists dissolution. The effect of temperature on the initial dissolution rate can be described by the Arrhenius equation, with dissolution rates in the order: lepidocrocite > magnetite > akaganeite > maghemite > hematite > goe- thite. Activation energies and frequency factors for these minerals are 20.0, 19.0, 16.0, 20.3, 20.9, 22.5 kcal/ mole and 5.8  1011, 1.8  101~ 7.4  10 7, 5.1  101~ 2.1  101~ 3.0 x 1011 g Fe dissolved/mZ/hr, re- spectively. The complete dissolution of magnetite, maghemite, hematite, and goethite is well described by the cube-root law, whereas that of lepidocrocite is not.

Sorption of inorganic phosphate by iron‐ and aluminium‐ containing components

Abstract: Summary The amounts of inorganic P sorbed by a range of Fe- and Al- containing components varied appreciably and decreased in the order allophane > fresh Al gel > Fe gel pseudoboehmite > aged Al gel > dried Fe gel > Fe-coated kaolinite > haematite > goethite > akaganeite > gibbsite = ground kaolinite > dispersed kaolinite. Al gel sorbed 30 to 70 times more P than gibbsite, and Fe gel sorbed approximately 10 times more P than its crystalline analogues (haematite, goethite. and akaganeite). Despite large differences in the extent of P sorption, the form of the isotherm was essentially the same for each sorbent. The ability of freshly-prepared Al gel suspensions to sorb P decreased with ageing, a property not shown by Fe gel. Drying of Fe gel at 80°C, however, caused an approximately 4-fold decrease in P sorption. Precipitation of Fe gel (2% Fe) on the surface of kaolinite increased P sorption by a factor of 10. The occurrence of Fe gel as a coating apparently presents more sorption sites to solution per unit weight of Fe gel than Fe gel alone. A linear relationship (r= 0.98) was obtained between the amount OH− sorbed per unit increase in pH value (‘hydroxyl buffering’) and the overall P sorption maximum for each sorbent. Hydroxyl buffering provided a better index of P sorption potential than specific surface area. Except for the crystalline Fe sorbents, isotherms obtained by plotting fractional sorption saturation against final solution P concentration for the sorbents were essentially coincident with those for several contrasting soils. For crystalline Fe components a lower relative amount of weaker sorption, as opposed to chemisorption, of the overall sorption maximum was obtained. Differences in the extent of P sorption. however, appear to be primarily related to the number of functional M-OH groups presented at the solid-solution interface.

Synthesis and Properties of Poorly Crystalline Hydrated Aluminous Goethites

Abstract: Al-substituted goethites were prepared by rapid oxidation of mixed FeCl2-AlCl3 solutions at pH 6.8 in the presence of CO2 at 25°C. A combination of Al substitution and adsorption of CO2 reduced crystal size (except for an increase at small additions of Al) and produced unusual thin, porous particles. Product goethites had surface areas up to 283 m2/g and unit-cell expansions induced by hydration. Substitution of Al for Fe reduced the 111 spacing and increased infrared OH-bending vibrational frequencies. Al substitution split the goethite dehydroxylation endotherm during differential thermal analysis into a doublet and increased the temperature of all reactions. Both cold and hot alkali solutions dissolved Al from the goethite structure. After drying the product in vacuo at 110°C. X-ray powder diffraction data indicated minimal deviation from Vegard’s law for the goethite-diaspore solid solution up to about 30 mole % Al substitution. Goethite prepared in the presence of 40 mole % Al had a 111 spacing of 2.403 A corresponding to 36 mole % structural Al if Vegard’s law was obeyed. Rapid oxidation of mixed FeCl2-AlCl3 solutions appears to be conducive to a higher degree of Al substitution in goethite than alkaline aging of hydroxy-Fe(III)-Al coprecipitates.

Material balance associated with phosphate sorption by amorphous clays, silica-alumina gel and synthetic goethite

Abstract: The material balance of all the chemical species associated with the phosphate sorption reaction by two amorphous clays, silica-alumina gel and synthetic goethite was investigated adjusting the initial pH to 4.0, 5.0, 6.0, and 7.0. Phosphate sorption was found to decrease with increasing initial pH. During phosphate sorption, the equilibrium pH rose, adsorption of Cl- decreased to a state of negative adsorption, adsorption of Na+ increased markedly, silicate was released, and Al in the solution was precipitated. With increasing initial pH, the amount of apparent released OH- increased, the amount of Na+ adsorption increased, and the amount of released silicate decreased. The overall relationship of the material balance is explained in terms of the charge balance associated with phosphate sorption.

Reactions of nucleic acid bases with inorganic soil constituents

Abstract: The adsorption at pH's 4, 6 and 8 of adenine, guanine, cytosine, thymine and uracil on clays (montmorillonite, illite and kaolinite), Fe- and Al-oxides (goethite, hematite and gibbsite), a soil, and on a laboratory-prepared fulvic acid-montmorillonite complex was investigated. Portions of the clays and soil were saturated with H+, Fe3+ and Ca2+. Quantitatively, the extent of adsorption of nucleic acid bases by the clays was proportional to their exchange capacities, but the nature of the dominant cation had only minor effects. By contrast, the adsorption was strongly affected by pH, tending to decrease with increase in pH. Adsorption on goethite and gibbsite was lower than that on clays, while adsorption of nucleic acid bases on soils was slightly lower than that on oxides. The fulvic acid-montmorillonite complex adsorbed substantial, although smaller amounts of purines and pyrimidines, than did montmorillonite alone. The main adsorption mechanism at pH 4 appeared to be cation exchange whereas at pH 8 complex formation between the nucleic acid bases and cations on inorganic surfaces seemed to occur. The results of this and earlier work show that both inorganic and organic soil constituents adsorb nucleic acid bases. Which adsorption reaction predominates will depend on the clay and organic matter content and on the pH.

Manufacture of ferromagnetic ironncobalt alloy powder

Abstract: PURPOSE:To manufacture ferromagnetic iron-cobalt alloy powder, by using a compound material made by sticking fine Co(OH)3 on the surface of needlelike goethite particles prepared from a soln. of ferrous salt. CONSTITUTION:To a soln. of ferrous salt is added an aqueous alkali soln. in an amount >=4OH /Fe mol ratio to prepard ferrous hydroxide, which is allowed to contact with a gas contg. oxygen in order to convert the ferrous salt completely into goethite crystals. Subsequently, cobaltous ions in an amount <=50%Co/(Fe+Co)mol ratio are added to the reaction system, and the system is allowed to contact with oxygen-contg. gas at <=60 deg.C temp. Hereby, cobaltic hydroxyde sticks to the surface of goethite crystals to form a compound material of goethite and cobaltic salt. The compound material is converted into compound oxide by heating. Ferromagnetic iron-cobalt alloy powder is prepared by reducing the oxide compound with hydrogen.

Variations in gossan geochemistry at the Perseverance nickel sulfide deposit, Western Australia; a descriptive and experimental study

Abstract: Two gossans developed from separate ore shoots at the Perseverance nickel sulfide deposit are notable for their different textures and compositions. The gossan developed from matrix sulfides in serpentinized ultramafic rock has high Ni and Cu contents and exhibits good retention of sulfide textures. The second gossan, developed from massive sulfides enclosed in metasedimentary rock, has high Cu but low Ni contents, and sulfide textures have been obliterated.Gossan-forming processes were simulated in electrochemical reaction cells using electrodes of sulfide ore assemblages, both with and without gangue minerals. Results of these experiments, together with results from studies of the adsorption of Ni and Cu onto goethite, were used to develop a model for the chemical processes involved in the weathering of sulfide ore to gossan. This model explains the different characteristics of the gossans in the two shoots. In the first gossan, the pH has apparently been buffered at a value in excess of 7 by carbonates and mafic gangue minerals, resulting in greater retention of Ni than in the second gossan, which lacks appreciable amounts of carbonates and mafic minerals. Cu, however, is catalytically involved in the goethite-forming process and is adsorbed onto goethite at a lower pH than is Ni, with the result that the Cu content is high in both gossans. Retention of sulfide pseudomorphs in the first gossan is attributed to silicification which, in turn, appears to be related to the low Al content of the ore from which the gossan was developed.

Preparation of goethite

Abstract: PURPOSE: To obtain needle-like goethite having uniform particle size distribution especially useful as a raw material for a magnetic material, by feeding intermittently an oxidizing gas to a hydroxide prepared by the reaction between an aqueous solution of a ferrous salt and an alkali aqueous solution in a circulating path while the hydroxide is circulated CONSTITUTION: A suspension of a hydroxide obtained by reacting an aqueous solution of a ferrous salt (eg, ferrous sulfate) with an aqueous solution of an alkali (eg, NaOH) is circulated while being partially taken out An oxidizing gas (eg, O 2 , air) is intermittently fed to the circulating path of the suspension, so that the hydroxide is oxidized into goethite The feed time of the oxidizing gas is made ≤1/4 of the feed stopping time, and the feed time in the feed-stop cycle is made usually ≤20min The oxidation ratio of the above-mentioned one cycle is made ≤10% While, the formation of the hydroxide and its oxidation is carried out at 20W80°C, the prepared goethite is in needle-like form and has a uniform particle size distribution, α-iron powder obtained by reducing and oxidizing it conventionally is useful as a raw material for a magnetic material COPYRIGHT: (C)1983,JPO&Japio

Manufacture of iron oxide hydrate

Abstract: PURPOSE:To enable high quality goethite useful as starting material for pigment and ferrite to be inexpensively mass-produced in a relatively short time by aging an alkali suspension contg. ferric salt followed by heat treatment under atmospheric pressure. CONSTITUTION:An aqueous soln. contg. FeCl3 or other ferric salt as a principal component is mixed with alkali to prepare an alkaline suspension. The amount of the alkali added is a slight excess such as about 1-10% excess over the amount required for neutralization. NaOH is typically used at the alkali, yet KOH or Ca (OH)2 may be used. The ferric salt-contg. alkali suspension assuming a reddish brown color is aged at 20-70 deg.C for 3-20hr with gentle stirring, heated to a temp. from 70 deg.C to the boiling state, and heat treated for 5-10hr, whereby it is rapidly converted into goethite assuming a yellow color. The precipitate is then separated by filtration, washed, and dried to obtain goethite powder tof fine needlelike crystal.

Influence of clay minerals and iron oxides on selected properties of two lateritic soils

Abstract: Mineralogical studies of two representative samples of lateritic red soil-one from Calicut-Kerala, and the other from Rajahmundry-Andhra Pradesh, revealed varying proportions of halloysite, kaolinite, goethite, gibbsite, quartz and colloidal iron oxide. Chemical removal of free iron oxide resulted in important changes in soil properties. X-ray peaks of clay minerals became sharper, the clay size fraction increased and the skempton activity decreased in the soils free of iron oxides. The cation exchange capacity (cec) was found to decrease in the more acidic, halloysite rich calicut soil whereas the cec of the Rajahmundry soil showed a significant increase simultaneously with increase in clay content after iron removal. (Author/TRRL)

Electrochemical reduction of goethite in the solid state : a topotactic process yielding an oriented-texture iron powder

Abstract: X-ray diffraction, transmission electron microscopy examinations and selected area electron diffraction patterns were used to investigate the crystallographic parameters and morphologies of the starting Goethite and of the iron resulting from its electrochemical reduction, in a 50 % NaOH-H2 O mixture, at 363 KIt was shown that the iron crystallites exhibit essentially the same morphology and particle size as α-FeOOH Furthermore, the metal crystals stay in a definite orientation in relation to the Goethite ones This electrochemical process leads to a metal powder presenting a well-defined and reproducible texture

Preparation of black iron oxide

Abstract: PURPOSE:To provide high-quality black iron oxide having a narrow size distribution by a method wherein an aqueous solution contg. divalent iron salts is maintained at a specified pH in the presence of alkali and is brought into contact with O2-contg. gas in the presence of seed magnetite at a specific temperature so that byproduction of goethite is prevented. CONSTITUTION:An aqueous solution contg. divalent iron salt (preferably ferrous sulfate heptahydrate) is strictly maintained at pH in the range of 6-7 within the variation of + or -0.2 in the presence of alkali such as ammonia. The solution is then brought into contact with oxygen-contg. gas in the presence of fine magnetite seed at a temperature of 40-100 deg.C. The process provides, with good reproducibility, high-quality, uniform black iron oxide having a narrow size distribution suitable for pigment and magnetic material, while eliminating byproduct such as goethite.

Preparation of needlelike coethite

Abstract: PURPOSE:To provide needlelike goethite suitable for preparing finely divided magnetic powder having remarkably improved saturation magnetization, by adding a bivalent metallic ion to a ferrous salt solution, oxidizing the solution under basic conditions, treating the formed needlelike goethite with a surfactant, and drying the resultant goethite. CONSTITUTION:A bivalent metallic ion, e.g. Ni , as a sulfate is added to a ferrous salt solution, e.g. ferrous sulfate, and adjusted to a pH>=11 with an alkali, e.g. NaOH. The alkaline solution is then mixed with an oxidizing agent, e.g. NaClO3, and oxidized at a temperature of preferably 80 deg.C or below. The formed precipitate (needlelike goethite) is filtered, washed with water to give washing water of pH<=8, and adjusted to a pH of about 3 with a small amount of a mineral acid. The needlelike goethite of adjusted pH is mixed with preferably 1-10wt% an anionic surfactant, and the mixture is agitated, filtered and separated to give the aimed needlelike goethite.

Preparation of hydrous ferric hydroxide powder

Abstract: PURPOSE:To prepare acicular goethite powder having sharp particle size distribution and free of branching, even by the direct hydrothermal treatment, by mixing ferrous or ferric hydroxide precipitate with aged ferric hydroxide precipitate, and subjecting the mixture to the hydrothermal treatment. CONSTITUTION:Precipitate of ferrous hydroxide or ferric hydroxide is mixed with aged precipitate of ferric hydroxide obtained by aging ferric hydroxide precipitate at room temperature - 70 deg.C for 5-30hr, and the mixture is subjected to the hydrothermal reaction at 100-250 deg.C. The amount of the aged precipitate is >=1/4 equivalent based on the precipitate to be treated hydrothermally. When precipitate of ferrous hydroxide is used as the starting material, it is necessary to carry out the reaction in the presence of an oxidizing agent such as NaClO3, NaNO3, etc. The aged ferric hydroxide precipitate acts as a seed to promote the conversion to goethite, and gives branch-free acicular goethite particles having sharp particle size distribution suitable as a raw material for the preparation of magnetic powder for magnetic recording use.

Mfg. acicular goethite of small particle size - by adding zinc salt and alkali to ferrous soln., precipitating ferrous hydroxide, adding chlorate and oxidising

Abstract: Mfr. of acicular goethite, comprises adding zinc salt and alkali to aq. ferrous salt soln. to adjust the soln. to above pH 11, pptn. of ferrous hydroxide, adjusting proportion of anion to ferrous ion to below 1, adding sodium chlorate or potassium chlorate, and carrying out oxidn. reaction at below 80 deg.C. The process reduces reaction time and gives acicular goethite having small particle size. In an example, to 1.0L of water there were dissolved 167 g of FeSO4.7H2O and 0.86g of ZnSO4.7H2O, and 168g. of NaOH and water added such that total volume becomes 1.5L. The soln. was allowed to stand for 6h. to form ppte. of ferrous hydroxide. 750mL of supernatant liquid was removed, by which proportion of anion to ferrous ion was adjusted to below 1. Next, to this, there were added 12.3 g of potassium chlorate and 0.37g of sodium silicate soln. and added water such that total vol. becomes 1.5L. The soln. was allowed to react at 50 deg. C for 8 h. The ppte. so produced had the structure of acicular goethite. The magnetic properties of the alloy obtd. by reduction of the acicular goethite (alpha-Fe(O)OH) at 400 deg.C were as follows: Hc:1450 Oe; sigma s:130 emu/g; sigma r/sigma s:0.56. (4oo).

Structural investigations of polycrystalline diaspore samples by x-ray powder diffraction Note: sample #4 Locality: from Nezsa, Hungary, associated with kaolinite, anatase and goethite

Abstract: Diaspore (α-AlOOH) samples of different origin have been investigated by means of X-ray powder diffraction. Film and diffractometer data, evaluated by common least squares and least squares profile-fitting refinement methods, respectively resulted in the same values of structural parameters. The structural invariability of natural diaspores can be concluded from the results.

Electrochemical reduction of goethite in the solid state: a topotactic process yielding an oriented-texture iron powder

Abstract: X-ray diffraction, transmission electron microscopy examinations and selected area electron diffraction patterns were used to investigate the crystallographic parameters and morphologies of the starting Goethite and of the iron resulting from its electrochemical reduction, in a 50 % NaOH-H2 O mixture, at 363 K.It was shown that the iron crystallites exhibit essentially the same morphology and particle size as α-FeOOH. Furthermore, the metal crystals stay in a definite orientation in relation to the Goethite ones. This electrochemical process leads to a metal powder presenting a well-defined and reproducible texture.

Water treatment of goethite

Abstract: PURPOSE:To carry out the precipitation and the recovery of a goethite fine powder in good efficiency by a method wherein a goethite particle and water are stirred and, thereafter, a recovery member having plural shelves is immersed in the resulting suspension and withdrawn upwardly. CONSTITUTION:In a washing work of the goethite particle, the geethite 3 and water are put in a container 1 and stirred therewithin. Thereafter, the recovery member having plural shelf plates 9 is immersed in said container 1 and withdrawn upwardly. Then, the goethite powder 3 floated in water is sedimented by the own weight gravity and precipitated on the shelf plates 9. Thereby, the water treatment of the goethite particle is carried in good workability within a short time and a magnetic powder with good magnetic characteristics can be obtained.