Oxidation of isochemical FeS2 (marcasite-pyrite) by Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans

A research-grade mineral sample that contained marcasite and pyrite (FeS2) was subjected to the oxidation by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Oxidation of FeS2 by A. ferrooxidans produced acid, and the redox potential increased with sulfide dissolution and the oxidation of Fe2+. jarosite was detected in solids from spent cultures. Preferential oxidation of either mineral was not consistently observed across all treatments. Neither iron sulfide was oxidized by A. thiooxidans. (C) 2006 Elsevier Ltd. All rights reserved.

Oxidative dissolution of covellite by Thiobacillus ferrooxidans

Oxidation of research-grade covellite was investigated in respirometric and growth experiments with Thiobacillus ferrooxidans. Covellite was directly oxidized by T. ferrooxidans in respirometric experiments, but the pH of mineral salts medium increased to prohibitively high values because of high sulfide concentrations. In glycine-H 2SO 4 buffered medium the pH remained steady and the oxygen uptake activity of T. ferrooxidans was not inhibited. In cultures growing with covellite as the sole source of energy, the pH increased to about 4. Redox potential increased to 500-600 mV during bacterial oxidation of covellite in the presence and absence of additional Fe 2+, whereas it remained mostly at about 350 mV in abiotic control. Jarosite was a major solid-phase product in T. ferrooxidans cultures. The solubilization of copper from covellite in inoculated flasks was higher than that obtained in control flasks and was not enhanced in the presence of additional Fe 2+.The sample also contained bornite (Cu 5FeS 4) which released iron in solution under all experimental conditions. Accumulation of S 0 was apparent only in inoculated covellite samples. © 1997 Elsevier B.V. All rights reserved.

Oxidative dissolution of chalcopyrite by Thiobacillus ferrooxidans

The oxidative dissolution of research-grade chalcopyrite was characterized in respirometric and growth experiments with Thiobacillus ferrooxidans. In respirometric experiments with chalcopyrite, the pH of mineral salts medium increased to values that inhibited the oxygen uptake activity of T. ferrooxidans. In glycine-H 2SO 4 buffered medium the pH remained stable and oxygen uptake was not inhibited. In cultures growing with chalcopyrite as the sole source of energy, pH changes were only minor during the incubation. The redox potential values increased to about 600 mV during the bacterial oxidation of chalcopyrite in the presence and absence of additional Fe 2+, while they remained at about 350 mV in abiotic control flasks. Iron in chalcopyrite was solubilized and oxidized to Fe 3+ by T. ferrooxidans. In the abiotic controls, by comparison, less iron was solubilized and it remained as Fe 2+. Jarosite was a major solid- phase product in T. ferrooxidans cultures. The solub'flization of copper from chalcopyrite in inoculated flasks was enhanced in the presence of additional Fe 2+.Accumulation of S 0, reflecting partial oxidation of the S-entity of chalcopyrite, was apparent from the x-ray diffraction analysis of solid residues from the inoculated flasks as well the abiotic controls. © 1997 Elsevier B.V. All rights reserved.

Effect of Na-chloride on the bioleaching of a chalcopyrite concentrate in shake flasks and stirred tank bioreactors

Oxidative dissolution of chalcopyrite at ambient temperatures is generally slow and subject to passivation, posing a major challenge for developing bioleaching applications for this recalcitrant mineral. Chloride is known to enhance the chemical leaching of chalcopyrite, but much of this effect has been demonstrated at elevated temperatures. This study was undertaken to test whether 100-200 mM Na-chloride enhances the chemical and bacterial leaching of chalcopyrite in shake flasks and stirred tank bioreactor conditions at mesophilic temperatures. Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and abiotic controls were employed for the leaching experiments. Addition of Na-chloride to the bioleaching suspension inhibited the formation of secondary phases from chalcopyrite and decreased the Fe(III) precipitation. Neither elemental S nor secondary Cu-sulfides were detected in solid residues by X-ray diffraction. Chalcopyrite leaching was enhanced when the solution contained bacteria, ferrous iron and Na-chloride under low redox potential (< 450 mV) conditions. Scanning electron micrographs and energy-dispersive analysis of X-rays revealed the presence of precipitates that were identified as brushite and jarosites in solid residues. Minor amounts of gypsum may also have been present. Electrochemical analysis of solid residues was in concurrence of the differential effects between chemical controls, chloride ions, and bacteria. Electrochemical impedance spectroscopy was used to characterize interfacial changes on chalcopyrite surface caused by different bioleaching conditions. In abiotic controls, the impedance signal stabilized after 28 days, indicating the lack of changes on mineral surface thereafter, but with more resistive behavior than chalcopyrite itself. For bioleached samples, the signal suggested some capacitive response with time owing to the formation of less conductive precipitates. At Bode-phase angle plots (middle frequency), a new time constant was observed that was associated with the formation of jarosite, possibly also with minor amount or elemental S, although this intermediate could not be verified by XRD. Real impedance vs. frequency plots indicated that the bioleaching continued to modify the chalcopyrite/solution interface even after 42 days. © 2013 The Authors.

Estudos físico-químicos e de lixiviação de calcopirita (CuFeS.IND.2) por Acidithiobacillus ferrooxidans

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Mineralogia e geoquímica de sedimentos de manguezais da costa amazônica: o exemplo do estuário do rio Marapanim (Pará)

Os manguezais do estado do Pará representam importante segmento da costa norte brasileira sobre os quais pouco se conhece das características geológicas e as relações com área(s)-fonte. A pesquisa foi realizada no estuário do rio Marapanim, na costa paraense, para demonstrar a contribuição de sedimentos continentais para a formação dos sedimentos dos manguezais. Foram coletados sedimentos da Formação Barreiras e solos dela derivados (principais fontes terrígenas), e os sedimentos de manguezal. Nos sedimentos de manguezal foram realizadas análises granulométricas, determinação dos teores de carbono (C %) e medidas de pH, Eh e salinidade intersticial. A determinação mineralógica e a geoquímica multi-elementar foi feita nos sedimentos lamosos e nos sedimentos continentais adjacentes, para comparações. Os sedimentos de manguezal são sílticoargilosos (> 90 %), com teores de carbono entre 0,75 a 3,5 %. A mineralogia principal é composta por quartzo, goethita, hematita, caulinita, illita, além de zircão, turmalina, estaurolita e cianita como acessórios, assinatura mineralógica típica dos sedimentos da Formação Barreiras e dos solos. De ocorrência comum nesses manguezais, os minerais neoformados são: esmectita, feldspato potássico, pirita, halita, gipso e a jarosita. O enriquecimento em SiO₂, Al₂O₃, Fe₂O₃, e TiO₂ nos manguezais e os níveis crustais dos metais-traço refletem o clima tropical e a composição mineralógica da área-fonte, rica em quartzo e caulinita e a ausência de influência antrópica. A composição química associada à matéria orgânica, abundantes diatomáceas além de Fe, S e os aportes de Cl^-, Na⁺, K⁺, Ca⁺⁺ e Mg⁺⁺ da água do mar, identificam o ambiente deposicional e os minerais autigênicos. O padrão de fracionamento dos elementos-traço nos manguezais também corrobora a marcante contribuição da área-fonte continental. Esses sedimentos apresentam o predomínio dos Elementos Terras Rara Leves (ETRL) sobre os Elementos Terras Raras Pesados (ETRP) com elevadas razões de Th/Co; La/Th; La/Sc; La/Co e Zr/Sc e Th/ Sc e Ba/Co, elementos presentes nas rochas ígneas félsicas que originaram os sedimentos terrígenos.

Sulfate Mineral Paragenesis in Pennsylvanian Rocks and The Occurrence of Slavikite in Nebraska

The acid weathering of pyrite-bearing Pennsylvanian clastic sedimentary rocks in southeastern Nebraska locally produces the secondary sulfate minerals alunogen, copiapite, epsomite, felsobanyaite/basaluminite, gypsum, halotrichite, jarosite, rozenite, and slavikite. Of these mineral occurrences, four are first-time discoveries in the state or the surrounding region. Slavikite (NaMg2Fe5 (S04)7 (OH) 6• 33H20), which has been reported only once before in North America and from a handful of sites in Europe and South America, was found in abundance at an outcrop at Brownville, NE. The pH values in 1:1 solutions of deionized water of the studied minerals, excluding epsomite, range from 1.94 to 4.82. Therefore, segregations of secondary minerals in themselves are significant microenvironmental reservoirs of acid that can be mobilized during precipitation events. Because of its role in liberating and concentrating ions such as Al3+, Fe2+, Fe3+, Mg3+, and SO42-, acid rock weathering should be considered in local to regional assessments of surface-water and groundwater chemistry. Observations also suggest that rock weathering by the growth of sulfate salts is a potential factor in local hillslope development, one that has not previously been considered in the study area.

Weathering of Fe-bearing minerals under extraterrestrial conditions, investigated by Mössbauer spectroscopy

The weathering of Fe-bearing minerals under extraterrestrial conditions was investigated by Mössbauer (MB) spectroscopy to gain insights into the role of water on the planet Mars. The NASA Mars Exploration Rovers Spirit and Opportunity each carry a miniaturized Mössbauer spectrometer MIMOS II for the in situ investigation of Martian soils and rocks as part of their payload. The MER flight instruments had to be modified in order to work over the Martian diurnal temperature range (180 K – 290 K) and within the unique electronic environment of the rovers. The modification required special calibration procedures. The integration time necessary to obtain a good quality Mössbauer spectrum with the MIMOS II flight instruments was reduced by 30 % through the design of a new collimator. The in situ investigation of rocks along the rover Spirit's traverse in Gusev crater revealed weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills. Correlation plots of primary Fe-bearing minerals identified by MB spectroscopy such as olivine versus secondary Fe-bearing phases such as nanophase Fe oxides showed that olivine is the mineral which is primarily involved in weathering reactions. This argues for a reduced availability of water. Identification of the Fe-oxyhydroxide goethite in the Columbia Hills is unequivocal evidence for aqueous weathering processes in the Columbia Hills. Experiments in which mineral powders were exposed to components of the Martian atmosphere showed that interaction with the atmosphere alone, in the absence of liquid water, is sufficient to oxidize Martian surface materials. The fine-grained dust suspended in the Martian atmosphere may have been altered solely by gas-solid reactions. Fresh and altered specimens of Martian meteorites were investigated with MIMOS II. The study of Martian meteorites in the lab helped to identify in Bounce Rock the first rock on Mars which is similar in composition to basaltic shergottites, a subgroup of the Martian meteorites. The field of astrobiology includes the study of the origin, evolution and distribution of life in the universe. Water is a prerequisite for life. The MER Mössbauer spectrometers identified aqueous minerals such as jarosite and goethite. The identification of jarosite was crucial to evaluate the habitability of Opportunity's landing site at Meridiani Planum during the formation of the sedimentary outcrop rocks, because jarosite puts strong constrains on pH levels. The identification of olivine in rocks and soils on the Gusev crater plains provide evidence for the sparsity of water under current conditions on Mars. Ratios of Fe2+/Fe3+ were obtained with Mössbauer spectroscopy from basaltic glass samples which were exposed at a deep sea hydrothermal vent. The ratios were used as a measure of potential energy for use by a microbial community. Samples from Mars analogue field sites on Earth exhibiting morphological biosignatures were also investigated.

“Sweating meteorites”-Water-soluble salts and temperature variation in ordinary chondrites and soil from the hot desert of Oman

The common appearance of hygroscopic brine (“sweating”) on ordinary chondrites (OCs) from Oman during storage under room conditions initiated a study on the role of water-soluble salts on the weathering of OCs. Analyses of leachates from OCs and soils, combined with petrography of alteration features and a 11-month record of in situ meteorite and soil temperatures, are used to evaluate the role of salts in OC weathering. Main soluble ions in soils are Ca2+, SO42−, HCO3−, Na+, and Cl−, while OC leachates are dominated by Mg2+ (from meteoritic olivine), Ca2+ (from soil), Cl− (from soil), SO42− (from meteoritic troilite and soil), and iron (meteoritic). “Sweating meteorites” mainly contain Mg2+ and Cl−. The median Na/Cl mass ratio of leachates changes from 0.65 in soils to 0.07 in meteorites, indicating the precipitation of a Na-rich phase or loss of an efflorescent Na-salt. The total concentrations of water-soluble ions in bulk OCs ranges from 600 to 9000 μg g−1 (median 2500 μg g−1) as compared to 187–14140 μg g−1 in soils (median 1148 μg g−1). Soil salts dissolved by rain water are soaked up by meteorites by capillary forces. Daily heating (up to 66.3 °C) and cooling of the meteorites cause a pumping effect, resulting in a strong concentration of soluble ions in meteorites over time. The concentrations of water-soluble ions in meteorites, which are complex mixtures of ions from the soil and from oxidation and hydrolysis of meteoritic material, depend on the degree of weathering and are highest at W3. Input of soil contaminants generally dominates over the ions mobilized from meteorites. Silicate hydrolysis preferentially affects olivine and is enhanced by sulfide oxidation, producing local acidic conditions as evidenced by jarosite. Plagioclase weathering is negligible. After completion of troilite oxidation, the rate of chemical weathering slows down with continuing Ca-sulfate contamination.

(Table 7) Representative electron microprobe analyses for natroalunite and larger FeOx spheroids of experiment ADSU6

Acid-sulfate alteration of basalt by SO2-bearing volcanic vapors has been proposed as one possible origin for sulfate-rich deposits on Mars. To better define mineralogical signatures of acid-sulfate alteration, laboratory experiments were performed to investigate alteration pathways and geochemical processes during reaction of basalt with sulfuric acid. Pyroclastic cinders composed of phenocrysts including plagioclase, olivine, and augite embedded in glass were reacted with sulfuric acid at 145 °C for up to 137 days at a range of fluid : rock ratios. During the experiments, the phenocrysts reacted rapidly to form secondary products, while the glass was unreactive. Major products included amorphous silica, anhydrite, and Fe-rich natroalunite, along with minor iron oxides/oxyhydroxides (probably hematite) and trace levels of other sulfates. At the lowest fluid : rock ratio, hexahydrite and an unidentified Fe-silicate phase also occurred as major products. Reaction-path models indicated that formation of the products required both slow dissolution of glass and kinetic inhibitions to precipitation of a number of minerals including phyllosilicates and other aluminosilicates as well as Al- and Fe-oxides/oxyhydroxides. Similar models performed for Martian basalt compositions predict that the initial stages of acid-sulfate alteration of pyroclastic deposits on Mars should result in formation of amorphous silica, anhydrite, Fe-bearing natroalunite, and kieserite, along with relict basaltic glass. In addition, analysis of the experimental products indicates that Fe-bearing natroalunite produces a Mössbauer spectrum closely resembling that of jarosite, suggesting that it should be considered an alternative to the component in sulfate-rich bedrocks at Meridiani Planum that has previously been identified as jarosite.

Chemistry of acid production in black coal mine washery wastes

Column leaching tests on black coal mine washery wastes were performed, to determine the chemistry of acid generation. Coal mine coarse rejects and tailings were subjected to wet and dry cycle dissolution and subsequently column leached. The rates of iron sulphide oxidation and carbonate mineral dissolution were determined based on the drainage chemistry. The kinetic data from column leach experiments are used to predict the time required to deplete the acid producing and acid consuming minerals in the mine wastes. The acid production in the mine rejects was found to depend upon iron chemistry, carbonate chemistry, diffusion of oxygen, and permeability. The chemistry of the drainage from two different coal mines is compared. (c) 2005 Elsevier B.V. All rights reserved.

Brisbane Airport: An alluvial landscape veiled by marine sediments

At Brisbane Airport, the construction of a diversion channel for Kedron Brook exposed a former beach, low cliff and sand spit, which, with their associated sediments and acid sulfate soils, demonstrate a postglacial high sea-level 1.3 - 1.4 m above present mean sea-level. The beach appears to date from 4000 to 5000 y BP. It varies in level where it lies above soft ground; these variations, and sag depressions that follow buried streamlines, indicate sediment consolidation since withdrawal of the sea from the former shore. Most of the area consists of former estuarine deposits, mangrove and saline marshes, and stranded tidal flats on which acid sulfate soils are widely developed. The modern landforms mostly reproduce subsurface features, to the extent that the surface relief replicates the landscape transgressed by the sea 7000 years ago. A small rise of sea-level possibly to +0.65 m occurred about 2000-3000 years ago. Foredunes near the present shore that are related to a slightly lower level 1000 - 500 years ago (-0.25 m) are currently subject to wave erosion.

Bioleaching-an approach for synthesizing functionalized nanoformulations for agricultural use.

Her work focussed on myco-nano-mining for the reduction of waste as well as for overcoming plant nutrient deficiencies by synthesizing potential nanonutrients