Showing papers on "Goethite published in 1993"
TL;DR: In this article, the authors described the preparation and characterisation of silica sand (cristobalite) with well defined iron oxides (e.g., goethite, hematite) on cristobalite as well as quartz surfaces.
196 citations
TL;DR: In this paper, the photolytic reduction of amorphous iron hydroxide [am-Fe(OH)_3], lepidocrocite (γ-FeOOH), goethite (α-FeOH), hematite, and natural iron-containing aerosol particles in the presence of formaldehyde, formate, acetate, oxalate, and butyrate has been investigated.
Abstract: The photolytic reduction of amorphous iron hydroxide [am-Fe(OH)_3], lepidocrocite (γ-FeOOH), goethite (α-FeOOH), hematite (α-Fe_2O_3), and natural iron-containing aerosol particles in the presence of formaldehyde, formate, acetate, oxalate, and butyrate has been investigated. Important parameters in the photoreduction experiments are the pH, wavelength of the irradiating light, nature of the electron donor, characteristics of the iron phase. The present results show that the fastest rates of photoreduction of Fe(III) to Fe(II) are achieved with am-Fe(OH)_3 as the electron acceptor and formate as the electron donor. Maximum rates of photoreduction were observed at 330 nm with a continuous decrease to 405 nm. Natural iron-containing aerosol particles show photochemical behavior similar to am-Fe(OH)_3 and γ-FeOOH. These results suggest that a significant fraction of the reactive atmospheric iron in urban aerosol could be present as am-Fe-
(OH)_3 and γ-FeOOH. Ambient iron-containing aerosol particles with oxalate as the electron donor resulted in a significant photochemical production of H_2O_2.
185 citations
TL;DR: In this paper, the treatment of silica sand contaminated with pentachlorophenol (PCP) using the standard Fenton's reagent procedure, sequential addition of iron (II) and H 2 O 2, and a goethite (α-FeOOH)-H 2 O O 2 system was investigated.
Abstract: The treatment of silica sand contaminated with pentachlorophenol (PCP) using the standard Fenton's reagent procedure, sequential addition of iron (II) and H 2 O 2 , and a goethite (α-FeOOH)-H 2 O 2 system was investigated. The standard Fenton's procedure oxidized 10 mg/L soluble PCP, but was ineffective in degrading 10 mg/kg or 250 mg/kg particulate and sorbed PCP in silica sand. Sequential addition of excess reagents (480 mg/L iron (II) and 7% H 2 O 2 ) degraded particulate and sorbed PCP, but with high stoichiometric H 2 O 2 requirements. The most efficient system for PCP degradation was the H 2 O 2 -goethite system
121 citations
TL;DR: In this article, the adsorption on goethite and hematite was measured as a function of pH (5-9), Cl (super -) (0, 1M, 4M), temperature (25 degrees C, 50 degrees C), and redox state (air, Fe (super + 2) -goethite).
Abstract: A variety of evidence suggests that the fluids forming stratiform and red-bed copper deposits derived their Cu, Ag, and other metals from adjacent red sandstones and shales. Copper and Ag are soluble in moderately concentrated chloride brines at intermediate oxidation states, but published data suggest that Cu is strongly adsorbed on goethite and hematite at pH near 7 and temperatures of 0 degrees to 100 degrees C. Also, Pb, Zn, Co, and Ni are soluble in chloride brines, but are only present in some red-bed Cu deposits. To examine variability in relative adsorption of 0.5 mg/l Ag, Co, Cu, Ni, Pb, and Zn, adsorption on goethite (195 m 2 /l) has been measured as a function of pH (5-9), Cl (super -) (0, 1M, 4M,), temperature (25 degrees C, 50 degrees C), and redox state (air, Fe (super +2) -goethite). Under oxidized conditions at 25 degrees C and 1M Cl, the order of decreasing adsorption is Cu-Pb-Zn-Co-Ni-Ag, with Cu and Pb almost completely adsorbed at pH values greater than 6. However, in 1M Cl at 25 degrees C with Eh buffered by Fe (super +2) -goethite, the order of decreasing adsorption is Pb-Zn-Co-Ni-Cu(-Ag?), and less than 50 percent of the Cu is adsorbed at pH 7. An exploratory experiment with 3M NaCl + 1M Na 2 SO 4 at 25 degrees C with about 4,000 m 2 /g of hematite as adsorbent and 75 mg/l Cu, Ag, Zn, Pb, and Co and 40 mg/l Fe (super +2) was conducted to approximate conditions in a red-bed pore fluid during diagenesis. An appreciable fraction of the Cu and Ag remained in solution at pH 7, but Pb, Zn, and Co were completely adsorbed. Based on this data, the observed range of metal associations (Cu, Cu-Ag, Cu-Co, Cu-Zn-Ag, etc.) in red-bed and stratiform copper deposits seems explainable by variations among districts in pH, Eh, temperature, major element content of pore fluid, and Fe oxide character of the diagenetic environment. Similar adsorption phenomena may account for varying metal ratios in other low-temperature ore deposits and in noneconomic metal enrichments.
117 citations
TL;DR: In this paper, the James-Healy model for adsorption of hydrolyzed species, with the use of a single adjustable parameter, ΔGchem, for each cation, correctly predicted both the direction and magnitude of the temperature dependence of the pH range for adaption, but failed to account for its concentration dependence.
107 citations
TL;DR: In this article, P sorption in 12 samples of soils of a typical hydrosequence of the Cerrado region (Brazil) was predicted by means of combining data on: (1) the amount and properties of gibbsite, goethite, hematite and kaolinite, and (2) the P-sorption characteristics of these minerals, according to existing data in the literature.
102 citations
TL;DR: In this article, the adsorption of lead and zinc onto goethite was studied as a function of pH, total dissolved metal concentration, surface area, and ionic strength.
Abstract: The adsorption of lead(II) and zinc(II) onto goethite was studied as a function of pH, total dissolved metal concentration, surface area of goethite, and ionic strength. The results for zinc and lead were compared with those for copper reported earlier. The adsorption edge of lead ranges from pH 4 to 7, similar to that of copper, but the adsorption edge of zinc is displaced by 1.5 pH units toward higher pH. A fourfold increase in goethite surface area had a significant effect on the adsorption edge of lead, but a tenfold increase in the ionic strength of the medium did not affect the adsorption edge of lead and zinc. At neutral pH, 50 percent of the zinc was still available for transport and reactions in aqueous solution, whereas almost 100 percent of the lead and copper were bound to the goethite surface. The distribution coefficients increase sharply with the increase in pH and ranged from 60 to 30,000 ml/g in 2.5 pH units for lead and from 60 to 3000 ml/g in 1.5 pH units for zinc, depending on the goethite surface area and metal concentration. Distribution coefficients were used to calculate the number of protons released per mole of metal adsorbed during the adsorption process, with the average number of protons released per mole of lead and zinc adsorbed estimated to be 0.97±0.07 and 1.32±0.06, respectively. Proton coefficients of copper, lead, and zinc were correlated to their ionic radii and apparent equilibrium binding constant. Although the adsorption behavior of copper and lead were similar and both have the same charge, the drop in pH per mole of metal adsorbed is more in copper than in lead.
98 citations
TL;DR: In this paper, the effect of sulfate on the adsorption of cadmium onto goethite has been studied, and it was shown that increasing the ionic strength of the metal-sulfate solutions caused a decrease both in heavy metal and in sulfate adsorptions.
Abstract: Complexing ligands may alter the adsorption behaviour of heavy metals compared to a ligand free system, either by changes in solution speciation, or by interactions at the adsorbing mineral surface. In this paper the effect of sulfate on the adsorption of cadmium onto goethite has been studied. Adsorption experiments under defined conditions revealed the following effects: Cadmium adsorption from sulfate containing solutions by goethite was higher than from pure NaNO3-solutions. Simultaneously sulfate adsorption increased, indicating synergic effects. Increasing the ionic strength of the metal-sulfate solutions caused a decrease both in heavy metal and in sulfate adsorption. Model calculations on simultaneous adsorption of cadmium and sulfate lead to the following conclusions: 1.) Sulfate adsorption reduces the surface potential so that the surface becomes more attractive to heavy metals. 2.) In addition, new, so called ternary surface complexes (SOCd+-SO4
2−) between reactive surface sites, heavy metals and sulfate-anions must be assumed in order to get agreement between observed and calculated effects.
89 citations
TL;DR: The iron oxide hydroxide minerals goethite and akaganéite were likely constituents of the sediments present in, for instance, geothermal regions of the primitive earth and may have adsorbed organics and catalyzed the condensation processes which led to the origins of life.
Abstract: The iron oxide hydroxide minerals goethite and akaganeite were likely constituents of the sediments present in, for instance, geothermal regions of the primitive earth. They may have adsorbed organics and catalyzed the condensation processes which led to the origins of life. The binding to and reactions of nucleotides and oligonucleotides with these minerals was investigated. The adsorption of adenosine, 5′-AMP, 3′-AMP, 5′-UMP, and 5′-CMP to these minerals was studied. Adenosine did not bind to goethite and akaganeite. The adsorption isotherms for the binding of the nucleotides revealed that they all had close to the same affinity for the mineral. Binding to goethite was about four times stronger than to akagan eite. There was little difference in the adsorption of each nucleotide suggesting the binding was between the negative charge on the phosphate group and the positive charges on the mineral surface. The absence of binding of adenosine is consistent with this explanation. Binding decreases as the pH increases due to the titration of the positive (acidic) centers on the minerals. Two times as many moles of polynucleotides were bound to these minerals as compared to the mononucleotides. Watson-Crick hydrogen bonding of adenosine and 5′-AMP to poly(U) complexes with goethite and akaganeite was observed. There was no interaction of uridine with the poly(U)-goethite complex as expected if Watson-Crick hydrogen bonding is taking place. Neither goethite nor akaganeite catalyzed the oligomerization of the phosphorimidazolide of adenosine (ImpA). The template directed synthesis of oligomers of 5′-GMP on the poly(C) bound to goethite was observed. Higher molecular weight oligomers were observed when the poly (C) was bound to goethite than was found in the absence of the mineral.
65 citations
59 citations
TL;DR: In this article, the levels of Fed, Ald, and Alo of the soils were, as a whole, positively correlated with the clay content, respectively, and they were associated with the exchangeable Al level.
Abstract: Thirty five Typic Paleudults and Typic Hapludults under a Lowland Dipterocarp Forest were characterized for clay minerals, free oxides, cation exchange capacity, and exchangeable bases. Kaolinite was predominant in the soil clays followed by quartz, vermiculite and gibbsite and an accessory amount of illite, partially-interlayered-vermiculite (PIV) and goethite in most soils. Goethite formation appeared to take place concomitantly with the weathering of illite into PIV. Lepidocrocite was found only in the soils of the middle to lower slopes. The magnitude of lepidocrocite formation under hydromorphic conditions was associated with the exchangeable Al level. Cristobalite and hematite were found only in the “red” soils, which may have been subjected to some thermal influences associated with coal combustion. The levels of Fed, Ald, and Alo of the soils were, as a whole, positively correlated with the clay content, respectively. Goethite was considered to be a possible source of crystalline Fe oxide...
TL;DR: In this article, the authors investigated the auto-decomposition of iron(II) nitrate in solution and found that the particle size of the precipitates increased significantly with increasing temperature, above 140°C.
TL;DR: In this paper, the effect of temperature on B adsorption by soils and soil minerals is investigated as a function of solution pH (3, 12), and reaction temperature (10, 25, and 40|MoC) after 2 h of reaction time.
Abstract: Information on the effect of temperature on B adsorption by soils and soil minerals is scant. These data are needed to understand B availability. Boron adsorption on goethite, gibbsite, kaolinite, montmorillonite, calcite, and two arid zone soils was investigated as a function of solution pH (3–12) and reaction temperature (10, 25, and 40|MoC) after 2 h of reaction time. Boron adsorption on all materials increased from pH 3 to 7, exhibited a peak at pH 7.5 to 10, and decreased from pH 10.5 to 12. Temperature dependence measured as the increase of the B adsorption maximum at 10|MoC compared with 40|MoC on reference minerals increased in the order: calcite (3|X%)
TL;DR: The carbon isotope geochemistry of the oolitic Neda Formation ironstone at occurrences in Wisconsin and Iowa is consistent with goethite formation in a Late Ordovician subaerial weathering environment as discussed by the authors.
TL;DR: A significant gold deposit in laterite is under development in the Carajas region of Brazil, where gold and electrum are found within iron oxide-hydroxide nodules in the ferruginous zone where gold orebodies have been delineated as discussed by the authors.
Abstract: A significant gold deposit in laterite is under development in the Carajas region of Brazil. The lateritic profile of the Igarape Bahia deposit, Carajas, can be divided into six horizons: basal unweathered rocks followed by saprolite, a pallid zone, a mottled zone, a ferruginous zone, and topsoil. Native gold and electrum are found within iron oxide-hydroxide nodules in the ferruginous zone where gold orebodies have been delineated. Most of the gold grains are less than 10 mu in size. There are three morphologicial types: (1) rounded grains in voids, associated with colloform goethite and needlelike goethite; (2) irregularly shaped grains filling shrinkage cracks in amorphous goethite; and (3) subidiomorphic crystals associated with amorphous goethite or needlelike goethite. The morphological features and occurrences of the gold suggest that it has been mobilized and reprecipitated during lateritization.In the ferruginous zone, gold grains from the upper part contain more silver than those from the lower part, i.e., the fineness of gold increases downward in the profile. Quartz veinlets and sulfides in bedrock suggest that the primary rocks were enriched in gold. In the first weathering stage thiosulfate ions from weathering of sulfides are hypothesized to transport both gold and silver into the saprolite and mottled zones where secondary electrum and silver-rich gold were formed. In the second stage, gold and silver were remobilized and incorporated into the ferruginous zone as the weathering proceeded and the erosion surface was lowered. In the third stage, after uplift and incision of the landscape, chloride leaching separated silver from gold grains to purify the electrum. The survival of electrum in the upper part of the ferruginous zone can be attributed to lower chloride concentrations in near-surface ground water and to enrichment of organic matter which can lower the redox potential and increase the stability of native silver. Some silver was then adsorbed by manganese oxide minerals in the lower part of the ferruginous zone.
TL;DR: In this article, the initial kinetics of sulphurous acid leaching of well characterised synthetic pure goethite and goethites containing cobalt in sorption and co-precipitation modes have been studied.
TL;DR: In this paper, it was shown that at constant light flux and constant solution light absorption, the number of lattice sites that are bonded by the organic acid, the rate of acid readsorption to the surface during photolysis, the conformation and structure of organic acid; the degree of oxidation of the organic acids; the presence or absence of an α-hydroxy group on the acid, and the number and conformation of the di-acid chain.
Abstract: Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe 2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an α-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe 2+ to solution where it becomes available for further reaction.
TL;DR: Barium ferrite fine particles were prepared from aqueous suspensions containing goethite (α-FeOOH) and barium hydroxide by a hydrothermal method as discussed by the authors.
Abstract: Barium ferrite fine particles were prepared from aqueous suspensions containing goethite (α-FeOOH) and barium hydroxide by a hydrothermal method. Barium ferrite particles of thin hexagonal plate shape could be produced from commercially available goethite with an Fe: Ba molar ratio of 7.2, whereas barium ferrite particles could be produced from synthesized goethite with a molar ratio of unity. The effects on the size of hexagonal platelike particles of such reaction conditions as temperature, stirring speed and alkali concentration were investigated. Particles of 0.6 to 0.8 μm mean size were prepared under the reaction conditions covered here.
TL;DR: In this article, the industrial product is mainly composed of amorphous β-FeOOH instead of goethite as previously considered in the name ''goethite processe''.
Abstract: Iron compounds obtained as by-products in the removal of iron from acid leach liquors in the electrolytic zinc industry exhibit high catalytic activity in the hydroprocessing of coal. They were analyzed and compared to model compounds prepared on the laboratory scale. The industrial product is mainly composed of amorphous β-FeOOH instead of goethite as previously considered in the name «goethite processe. Correlatively with catalytic activity, high reactivity toward H 2 S was demonstrated
TL;DR: In this article, an Avrami-Erofeyev-type relation was found to describe the thermal conversion of alpha oxihydroxide to the alpha iron oxide, and a possible nucleation mechanism was also discussed.
TL;DR: In this article, the properties of the solid phases formed by the hydrolysis of Fe3+ ions in NH4Fe(SO4)2 solutions at 90 or 120°C were investigated using X-ray diffraction, 57Fe Mossbauer spectroscopy, and Fourier transform IR Spectroscopy.
TL;DR: Fluoride ion interaction with synthetically prepared goethite has been investigated over a range of pH values (4–9) and F− concentrations (10−3−10−5 M).
Abstract: Fluoride ion interaction with synthetically prepared goethite has been investigated over a range of pH values (4–9) and F− concentrations (10−3−10−5 M). The amount of F− retained by goethite suspensions was found to be a function of pH, media ionic strength, F− concentration, and goethite concentration. The lowest ionic strength (0.001 M KNO3) gave the highest adsorption medium. Uptake was minimal at pH >7 and increased with decreasing pH. Thermodynamic properties for fluoride adsorption at 298 K and 323 K were investigated. The isosteric heat of adsorption (δH
r) was calculated and the heterogeneity and homogeneity of the surface examined for goethite. In view of the importance of fluoride in dental health, the interaction of fluoride on goethite in the physical environment has important implications on dental epidemiology.
01 Jan 1993
TL;DR: Aqueous speciation and surface complexation to goethite (α-FeOOH), of divalent mercury, lead and cadmium, was described in this paper.
Abstract: Aqueous speciation and surface complexation to goethite (α-FeOOH), of divalent mercury, lead and cadmium
04 Apr 1993-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, fresh and naturally weathered coal samples from the same seam as well as the former one submitted to artificial oxidation treatments were studied by Mossbauer spectroscopy to examine the effect of coal oxidation conditions on the transformations of iron minerals.
Abstract: Fresh and naturally weathered coal samples from the same seam as well as the former one submitted to artificial oxidation treatments were studied by Mossbauer spectroscopy to examine the effect of coal oxidation conditions on the transformations of iron minerals. It was found that illite, pyrite and siderite are converted into jarosite and goethite in a natural environment, whereas only a small fraction of Fe2+ from pyrite was oxidized to Fe3+ under laboratory conditions, even after heating in air to 468 K. It is concluded that artificial oxidation experiments hardly reproduce the conditions met by coal when submitted to natural weathering.
TL;DR: In this paper, the degradation of aniline into various products has been investigated in aqueous suspensions of goethite in 0.001 M NaNO3 over a range of laboratory conditions.
Abstract: Kinetic aspects of the degradation of aniline into various products has been investigated in aqueous suspensions of goethite in 0.001 M NaNO3 over a range of laboratory conditions. A ligand promoted dissolution model was used to define the fate of aniline in a mineral surface mediated reaction system. At a given [H+] concentration the reaction rate was found to be dependent on both aniline and goethite concentrations.
TL;DR: In this article, the application of ultra-high intensity grinding (UHIG) on a mixture of BaCO 3 with iron oxide-hydroxides (lepidocrocite or goethite) led to the formation of highly reactive mixtures which were able to react at 700-800°C under formation of hexagonal barium ferrite BaFe 12 O 19.
TL;DR: In this article, the authors investigated the kinetics of the reaction of goethite (a-FeOOH(s)) and barium hydroxide (Ba(OH)2) in an alkaline solution to produce BaO-6Fe2O3 by the hydrothermal method.
Abstract: The kinetics of the reaction of goethite (a-FeOOH(s)) and barium hydroxide (Ba(OH)2) in an alkaline solution to produce BaO-6Fe2O3 by the hydrothermal method was investigated in the present study. The reaction was carried out in a batch closed reactor under high temperature and high pressure. The effects of α-FeOOH(s), Ba(OH)2 and NaOH concentrations in the feed and the temperature on the reaction rate were examined. It was found that the reaction rate was highly dependent upon the concentration of Fe(OH)4(aq) (i.e., the dissolved a-FeOOH(s)) and Ba(OH)2. A kinetic model, based on the homogeneous phase reaction, was built to describe the dissolution of a-FeOOH(s) and the precipitation of the dissolved α-FeOOH(s) (or Fe(OH)4 (aq)) and Ba(OH)2 in sequence to produce the desired product, BaO.6Fe2O3. The reaction rate at 280°C is expressed as function of Fe(OH)4 (aq) and Ba2+ concentration.
04 Apr 1993-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, X-ray diffraction studies were carried out on Salem, Tamil Nadu (India) bauxite and the analysis showed the dominant presence of Al-substituted goethite and hematite.
Abstract: 57Fe Mossbauer and X-ray diffraction studies are carried out on the Salem, Tamil Nadu (India) bauxite. The analysis shows the dominant presence of Al-substituted goethite and hematite. The Al-substitution in hematite is about 15 mole%. Very small quantities of magnetite and ilmenite are also detected. Thermal and NaOH treatments have established these findings. Furthermore, our studies confirm that HCl leaching is quite effective for the iron oxide removal.