Structure Of Jarosite Research Articles

Different fates of Sb(III) and Sb(V) during the formation of jarosite mediated by Acidithiobacillus ferrooxidans

Secondary iron-sulfate minerals such as jarosite, which are easily formed in acid mine drainage, play an important role in controlling metal mobility. In this work, the typical iron-oxidizing bacterium Acidithiobacillus ferrooxidans ATCC 23270 was selected to synthesize jarosite in the presence of antimony ions, during which the solution behavior, synthetic product composition, and bacterial metabolism were studied. The results show that in the presence of Sb(V), Fe2+ was rapidly oxidized to Fe3+ by A. ferrooxidans and Sb(V) had no obvious effect on the biooxidation of Fe2+ under the current experimental conditions. The presence of Sb(III) inhibited bacterial growth and Fe2+ oxidation. For the group with Sb(III), products with amorphous phases were formed 72 hr later, which were mainly ferrous sulfate and pentavalent antimony oxide, and the amorphous precursor was finally transformed into a more stable crystal phase. For the group with Sb(V), the morphology and structure of jarosite were changed in comparison with those without Sb. The biomineralization process was accompanied by the removal of 94% Sb(V) to form jarosite containing the Fe-Sb-O complex. Comparative transcriptome analysis shows differential effects of Sb(III) and Sb(V) on bacterial metabolism. The expression levels of functional genes related to cell components were much more downregulated for the group with Sb(III) but much more regulated for that with Sb(V). Notably, cytochrome c and nitrogen fixation-relevant genes for the A.f_Fe2+_Sb(III) group were enhanced significantly, indicating their role in Sb(III) resistance. This study is of great value for the development of antimony pollution control and remediation technology.

Jarosites: Formation, Structure, Reactivity and Environmental

Jarosite, beudantite and alunite are members of the alunite supergroup. Minerals like those have been detected in different environments on Earth. These jarosite-type compounds are common in acid rock drainage environments and acid sulfate soils, resulting from the weathering of sulfide ores; they are also present in bioleaching systems because they are found in cultures of iron-oxidizing microorganisms. Jarosite is also generated in hydrometallurgical circuits, mainly in zinc hydrometallurgy. These minerals can be used to immobilize different elements such as arsenic and lead, among others. Jarosite and alunite have also been detected on the surface of Mars; the presence of jarosite and alunite and other sulfates provides evidence for the existence of water on Mars. In this work, an exhaustive review of the natural formation, synthesis, structure, thermodynamics, and reactivity of jarosite, beudantite and alunite are included. The capacity of jarosites for the immobilization of the elements, such as lead and arsenic, and information about studies related to jarosite formation on Mars are also included.

Synthesis of iron sand into yellow nano-pigment using sol-gel method

The organic pigment was synthesized from iron sand, and alum used sol-gel method. Iron sand was soluted on chloride acid to made FeClx. The chelating agent was used oxalic acid to form metal organic as iron oxalic (FeC2O4). Adjustment of pH about 2 has done by NH4OH titration with precursor volume ratio variation. The gel was formed with PEG addition on 150°C heating temperature for 8 hours. The gel was washed with distilled water to eliminate salts residue. The gel was heated on temperature 200°C for 5 hours then yellow pigment is formed. XRD characterization showed that the yellow pigment has a structure of Jarosite. The color of pigment was analyzed using CIE Lab and identified that the yellow color composition is dominant on 1:1 volume ratio of precursor NH4OH. The color and magnetic properties of the pigment were changed by heating treatment.

Kinetic Analysis of the Decomposition of the KFe3(SO4)2-x(CrO4)x(OH)6Jarosite Solid Solution in Ca(OH)2Medium

The decomposition of the solid solution of potassium jarosite with chromium(VI) in Ca(OH)2 media was studied in the present work. According to experimental results, the incorporation of CrO42- into the crystal structure of jarosite resulted in a solid solution with the following approximate formula: [K0.86(H3O)0.14]Fe2.67[(SO4)1.23(CrO4)0.77][(OH)5.01(H2O)0.99]. The experimental data describe a reaction based on the shrinking core model with chemical control for spherical particles. A reaction order of n = 0.67 and an activation energy (Ea) of 63.75 kJ mol-1 were obtained in the induction period (tind). The progressive conversion period is characterized by the diffusion of K+, SO42- and CrO42- ions into the solution. In this stage, n = 1.99 with respect to OH-, and Ea = 51.56 kJ mol-1. The CrO42- diffusion is slower compared to that of sulfate, a slight amount of chromate is adsorbed in the layer of the solid residue consisting on Fe(OH)3. Finally, the equations that satisfactorily describe the reaction process were established from the data obtained.

Location of hydrogen atoms in hydronium jarosite

Various models for the crystal structure of hydronium jarosite were determined from Rietveld refinements against neutron powder diffraction patterns collected at ambient temperature and also single-crystal X-ray diffraction data. The possibility of a lower symmetry space group for hydronium jarosite that has been suggested by the literature was investigated. It was found the space group is best described as \(R\bar{3}m\), the same for other jarosite minerals. The hydronium oxygen atom was found to occupy the \(\overline{3} m\) site (3a Wyckoff site). Inadequately refined hydronium bond angles and bond distances without the use of restraints are due to thermal motion and disorder of the hydronium hydrogen atoms across numerous orientations. However, the acquired data do not permit a precise determination of these orientations; the main feature up/down disorder of hydronium is clear. Thus, the highest symmetry model with the least disorder necessary to explain all data was chosen: The hydronium hydrogen atoms were modeled to occupy an m (18 h Wyckoff site) with 50 % fractional occupancy, leading to disorder across two orientations. A rigid body description of the hydronium ion rotated by 60° with H–O–H bond angles of 112° and O–H distances of 0.96 Å was optimal. This rigid body refinement suggests that hydrogen bonds between hydronium hydrogen atoms and basal sulfate oxygen atoms are not predominant. Instead, hydrogen bonds are formed between hydronium hydrogen atoms and hydroxyl oxygen atoms. The structure of hydronium alunite is expected to be similar given that alunite supergroup minerals are isostructural.

The crystal structure and vibrational spectroscopy of jarosite and alunite minerals

The alunite supergroup of minerals is a large hydroxy-sulfate mineral group, which has seen renewed interest following their discovery on Mars. Numerous reviews exist concerning nomenclature, formation, and natural occurrence of this mineral group. Sulfate minerals in general are widely studied and their vibrational spectra are well characterized. However, no specific review concerning alunite and jarosite spectroscopy and crystal structure has been forthcoming. This review focuses on the controversial aspects of the crystal structure and vibrational spectroscopy of jarosite and alunite minerals. Inconsistencies regarding band assignments especially in the 1000-400 cm-1 region plague these two mineral groups and result in different band assignments among the various spectroscopic studies. There are significant crystallographic and magnetic structure ambiguities with regards to ammonium and hydronium end-members, namely, the geometry these two ions assume in the structure and the fact that hydronium jarosite is a spin glass. It was also found that the synthetic causes for the super cell in plumbojarosite, minamiite, huangite, and walthierite are not known.

Behaviour of the Alkaline Earth Elements (Beryllium to Radium) During the Precipitation of Jarosite-Type Compounds

The behaviour of the alkaline earth elements (beryllium, magnesium, calcium, strontium, barium and radium) during the precipitation of jarosite-type compounds was investigated over the range of conditions likely to be encountered in hydrometallurgical processes. Negligible amounts (< 0.05 wt%) of beryllium were incorporated in the structure of either potassium jarosite or sodium jarosite; this was a consequence of the small size of the divalent beryllium ion. In contrast, limited magnesium incorporation seemed to occur in the jarosite structure. Up to 0.20 wt% Mg was incorporated in sodium jarosite and up to 0.38 wt% Mg was detected in potassium jarosite; in both species, the amount increased as the magnesium concentration of the synthesis solution increased. Increasing temperatures, ferric ion concentrations and solution pH had only a minor effect on the extent of magnesium incorporation in the jarosite precipitates. In contrast, increasing concentrations of CuSO4 or ZnSO4 significantly reduced the level of Mg incorporation. Regardless of the calcium concentration of the solution, the calcium contents of the well-washed hydronium jarosite, sodium jarosite, potassium jarosite and lead jarosite precipitates were consistently less than 0.05 wt%Ca. The addition of soluble salts of strontiumand bariumto sulphate processing solutions resulted in the extensive precipitation of SrSO4 and BaSO4. However, electron microprobe analyses detected trace amounts of these elements in the potassium jarosite precipitates, suggesting a modest degree of Sr and Ba solid solubility. Picogram quantities of radium are soluble in sulphate media and 60-90% of the dissolved Ra precipitated with the jarosite-type compounds. However, it is not clear whether the radium was incorporated in the structure of the jarosite or whether it was adsorbed on the jarosite particles.

Factors Affecting the Precipitation of Potassium Jarosite in Sulfate and Chloride Media

The factors affecting the precipitation of potassium jarosite in both sulfate and chloride media were systematically investigated for the range of conditions likely to be encountered in hydrometallurgical practice. In sulfate solutions at 97 °C, the amount of precipitate increases with increasing retention times up to 10 hours, with increasing temperatures to approximately 100 °C, and with increasing ferric-ion concentrations. Despite the variations in the amount of precipitate, the composition remains nearly constant and is characteristic of that of potassium jarosite. The presence of potassium jarosite seed accelerates the rate of precipitation and results in near-maximum amounts of precipitate after just a few hours of reaction. The presence of ferrous sulfate has a negligible effect on both the product yield and composition. The amount of precipitate decreases with increasing acid concentrations, but the composition of the precipitates remains nearly constant, even for acid concentrations as high as 1.0 M H2SO4. Both the amount and composition of the precipitates vary as the K2SO4 concentration increases; in the presence of excess ferric ions, nearly complete K precipitation occurs. Small amounts of Cu2+, Zn2+, and Pb2+ are incorporated in the structure of potassium jarosite, and the amount increases with increasing concentrations of the divalent metal ions. Potassium jarosite is readily formed in chloride media at 140 °C, provided that an independent source of sulfate ions is available. A minimum K concentration is required in order to avoid the formation of hematite; at higher K concentrations, however, the product composition becomes nearly constant and reflects that of potassium jarosite. Both the product yield and composition are independent of the chloride concentration, added as LiCl, and the ferrous ion concentration, added as FeCl2. Although increasing concentrations of HCl result in a near-linear decrease in the amount of precipitate, the composition is independent of the HCl concentration and is characteristic of that of potassium jarosite. Increasing temperatures to 200 °C result in an increase in the product yield, but have no significant effect on the composition of the potassium jarosite precipitates.

Jarosite inclusion of fluoride and its potential significance to bioleaching of sulphide minerals

Incorporation of fluoride ions into the structure of jarosite, a common precipitate in bioleaching, was studied. Crystalline jarosite was synthesized in the presence of various concentrations of fluoride ions and characterized by spectroscopic- and chemical analysis. The results showed that substantial amounts of fluoride were sorbed to jarosite, increasing with pH and fluoride concentration. FTIR, XRD and Mössbauer analysis supported a structural incorporation of the fluoride. Due to the size similarity between fluoride and hydroxide ions, a probable mechanism is an exchange of hydroxide ions and fluoride ions within the jarosite, giving the composition KFe 3(SO 4) 2(OH) 6 − x F x (s). For the maximum concentration of fluoride used during synthesis, 200 mM, about 25% of the hydroxide ions were exchanged for fluoride ions. The mass of jarosite precipitated shown to be highly dependent on the fluoride concentration, with approximately half the yield using 200 mM potassium fluoride compared to in the absence of fluoride ions. To test the influence on toxicity of the incorporation of fluoride in jarosite, a bioleaching study was performed at 65 °C. A suspension of pyrite concentrate with 4% solid content (w/v) in the modified 9 K medium was bioleached under additions of potassium fluoride. The results indicated a higher tolerance for fluoride ions, as compared to earlier reported studies on fluoride toxicity during bioleaching.

Dissolution of jarosite [KFe 3(SO 4) 2(OH) 6] at pH 2 and 8: Insights from batch experiments and computational modelling

Jarosite [KFe 3(SO 4) 2(OH) 6] is a mineral that is common in acidic, sulphate-rich environments, such as acid sulphate soils derived from pyrite-bearing sediments, weathering zones of sulphide ore deposits and acid mine or acid rock drainage (ARD/AMD) sites. The structure of jarosite is based on linear tetrahedral–octahedral–tetrahedral (T–O–T) sheets, made up from slightly distorted FeO 6 octahedra and SO 4 tetrahedra. Batch dissolution experiments carried out on synthetic jarosite at pH 2, to mimic environments affected by ARD/AMD, and at pH 8, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH) 2), suggest first order dissolution kinetics. Both dissolution reactions are incongruent, as revealed by non-ideal dissolution of the parent solids and, in the case of the pH 8 dissolution, because a secondary goethite precipitate forms on the surface of the dissolving jarosite grains. The pH 2 dissolution yields only aqueous K, Fe, and SO 4. Aqueous, residual solid, and computational modelling of the jarosite structure and surfaces using the GULP and MARVIN codes, respectively, show for the first time that there is selective dissolution of the A- and T-sites, which contain K and SO 4, respectively, relative to Fe, which is located deep within the T–O–T jarosite structure. These results have implications for the chemistry of ARD/AMD waters, and for understanding reaction pathways of ARD/AMD mineral dissolution.

Surfactant mediated nanoparticle assembly of catalytic mesoporous crystalline iron oxide materials

The first examples of a new mesoporous form of crystalline β-FeOOH (akaganeite) were prepared by the surfactant-assisted method of nanoparticle assembly using FeCl 3 as the precursor and a surfactant of either cationic cetylpyridinium or anionic dodecylsulfonate or nonionic Brij 56 as a hierarchical structure mediator. TEM images indicated the presence of a scaffold-like structure formed through the aggregation and intergrowth of rod-like akaganeite nanoparticles. The synthesized mesoporous akaganeite has a unimodal and very narrow pore size distribution with high surface area, which can be converted to mesostructured α-Fe 2O 3 (hematite) after degassing at 300 °C. Bimodal pore size distributions could be obtained by increasing the synthetic temperature from 40 to 80 °C. Mesoporous iron oxides with bicrystalline structure of akaganeite and hydronium jarosite were prepared when using dodecylsulfonate surfactant at 80 °C. The surfactants were believed to play an important role in the formation of the hierarchical scaffold-like mesostructure.

Structure and magnetism of hydronium jarosite, a model Kagomé antiferromagnet

We have determined the structure of a synthetic sample of the mineral hydronium jarosite by powder neutron diffraction, locating all the hydrogen atoms. Octahedrally coordinated Fe3+ ions are linked through their vertices to produce Kagome layers of moments with a coverage of ca. 95 ± 4%, depending on the synthesis conditions. Magnetic susceptibility measurements indicate strong coupling of these moments, with Curie–Weiss constant of –1200 K, but there is no evidence for long-range magnetic order in neutron powder diffraction patterns taken down to 1.5 K. Instead, we observe an anomaly in the magnetic susceptibility at 17.2 K which is a characteristic of spin-glass freezing and similar to experimental work and theory for other Kagome antiferromagnets.

Preparing particulate magnetites with pigment properties from suspensions of basic iron(III) sulphates with the structure of jarosite

The transformation of a suspension of hydronium jarosite, H3O+Fe3(SO4)2(OH)6, into Fe3O4 (magnetite) of pigment quality is described. The process consists in the neutralization of the hydronium jarosite suspension in FeSO4 aqueous solutions with NH3 and subsequent thermal treatment of this mixture at controlled pH and temperature.

Preparation and structure of porous jarosite

A porous jarosite (KFe 3(SO 4) 2(OH) 6) with high specific surface area (150 m 2/g), which is much larger than that of usual synthetic and mineral jarosites (less than 1 m 2/g), was synthesized by adding K 2SO 4 of an amount of saturation to aqueous Fe 2(SO 4) 3 solutions under boiling at pH 1.8-2.1 and by washing the precipitates with a large amount of water over 3 liters/g. The structure and formation mechanism of the porous jarosite were discussed with reference to chemical composition, SEM and TEM images, and N 2 adsorption. The t-plot and pore-size distribution curve for N 2 adsorption isotherm indicated the existence of slitlike pores of <1.1, 1.5, and 2.5 nm in width. The interstices between lamellar crystals seem to be formed by release of water-soluble materials and colloidal hydrous iron oxide during washing of the precipitates.