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Sample records for pyrite

  1. Pyrite oxidation by thermophilic archaebacteria

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, L.; Olsson, G.; Holst, O.; Karlsson, H.T. (Lund Univ. (Sweden))

    1990-03-01

    Three species of thermophilic archaebacteria of the genera Sulfolobus (Sulfolobus acidocaldarius and S. solfataricus) and Acidianus (Acidianus brierleyi) were tested for their ability to oxidize pyrite and to grow autotropbically on pyrite, to explore their potential for use in coal desulfurization. Only A. brierleyi was able to oxidize and grow autotrophically on pyrite. Jarosite was formed during the pyrite oxidation, resulting in the precipitation of sulfate and iron. The medium composition affected the extent of jarosite formation.

  2. Pyrite oxidation by microbial consortia

    Science.gov (United States)

    Bostick, B. C.; Revill, K. L.; Doyle, C.; Kendelewicz, T.; Brown, G. E.; Spormann, A. M.; Fendorf, S.

    2003-12-01

    Acid mine drainage (AMD) is formed through pyrite oxidation, which produces acidity and releases toxic metals associated with pyrite and other sulfide minerals. Microbes accelerate pyrite oxidation markedly, thereby playing a major role in the production of AMD. Here, we probe pyrite oxidation by consortia of Thiobacillus ferrooxidans and thiooxidans using surface-sensitive photoelectron spectroscopy and X-ray absorption spectroscopy and compare them with surfaces oxidized through chemical and single species cultures. Microbial oxidation resulted in the formation of distinct oxidized surface species distributed non-uniformly over the pyrite surface; consortia produced a surface both more heterogeneous and more oxidized. In contrast, chemical oxidation proceeds without the build-up of passivating oxidation products. Surface morphology was not correlated with sites of nucleation or oxidation in any obvious manner. These results demonstrate that microbial oxidation occurs through a similar mechanism to chemical oxidation, but that the presence of complex microbial communities may impact the manner by which pyrite oxidation proceeds.

  3. Pyritization in the Gaojiashan Biota

    Institute of Scientific and Technical Information of China (English)

    CAI YaoPing; HUA Hong

    2007-01-01

    The Late Sinian (Ediacaran) Gaojiashan Biota was a soft-bodied fossil-Lagerst(a)tte dominated by substantial pyritized, three-dimensionally preserved tubular and conotubular fossils. Soft-tissue pyritization is extremely scarce in the fossil records, especially in the Precambrian, therefore it has very important and unique significance for the study of pyritization in the Gaojiashan Biota. Early pyritization played a pivotal role in the fossil preservation and two main factors ensured the successful pyritization of the fossils, namely rapid burial and permineralization. The former was controlled by secular storm deposition, and the latter was achieved by sufficient supply of available iron from sediments. SEM data of Conotubus demonstrate two types of preservation of the tubes (defined as type A and type B, respectively). In type A, pyritization took place relatively earlier and completely preserved both tube wall and coelom, but no detailed structure. While in type B, pyritization took place somewhat later and preserved the integrated tube wall, but partially the coelom. The size frequency distribution of the pyrite framboids suggests that pyritization took place in two different environments with entire different oxygen content.

  4. Pyrite oxidation by sulfolobus acidocaldarius

    Energy Technology Data Exchange (ETDEWEB)

    Tobita, M.; Yokozeki, M.; Nishikawa, N.; Kawakami, Y. (Institute of Research and Innovation, Kashiwa (Japan). Dept. of Biotechnology)

    1994-04-01

    Two strains of Sulfolobus acidocaldarius, a thermoacidophilic archaebacterium, were examined for their pyrite-oxidizing ability. S. acidocaldarius ATCC 33909 was shown to possess iron-oxidizing activity by ferrous sulfate oxidizing experiments, but S. acidocaldarius No. 7 did not have it. Pyrite-oxidizing rate of S. acidocaldarius ATCC 33909 was 1.6-fold higher than that of strain 7 though they had a similar level of self-oxidizing ability. These results show that the iron-oxidizing activity accelerates pyrite oxidation.

  5. Oxidation of pyrite: Consequences and significance

    Directory of Open Access Journals (Sweden)

    Dimitrijević Mile D.

    2002-01-01

    Full Text Available This paper presents the most important studies on the oxidation of pyrite particularly in aqueous solutions. The consequences of pyrite oxidation was examined, as well as its importance, from both the technical-technological and environmental points of view. The oxidation of pyrite was considered in two parts. The spontaneous oxidation of pyrite in nature was described in the first part, with this part comprising pyrite oxidation in deposits depots and mines. It is explained how way natural electrochemical processes lead to the decomposition of pyrite and other minerals associated with pyrite. The oxidation of pyrite occurring during technological processes such as grinding, flotation and leaching, was shown in the second part. Particular emphasis was placed on the oxidation of pyrite during leaching. This part includes the leaching of sulphide and oxide ores, the leaching of pyrite coal and the leaching of refractory gold-bearing ores (pressure oxidation, bacterial oxidation, oxidation by means of strong oxidants and the electrolysis of pyrite suspensions. Various mechanisms of pyrite oxidation and of the galvanic interaction of pyrite with other sulphide minerals are shown.

  6. Pyrite synthesis via polysulfide compounds

    Science.gov (United States)

    Luther, George W., III

    1991-10-01

    The reactions of Fe(II) and Fe(III) solutions with polysulfide solutions prepared from freshly synthesized Na 2S x ( x = 2, 4, 5) were studied at 25 and 100°C over the pH range 5.5 to 8. Direct and instantaneous pyrite formation was not observed in any reaction. High temperature reactions are nearly quantitative over periods of four hours with Fe(II) and polysulfide solutions. The rate of reaction at room temperature is comparable to that found by RICKARD (1975), and the observations reported here are in agreement with his mechanism of pyrite formation. Based on the polarographic results of these reactions and previous work, a refinement of the mechanism which includes dissolved iron sulfide complexes is proposed. Every reaction of equimolar amounts of polysulfide and Fe(II) gave the kinetic product "FeS" (an example of the Ostwald step rule). Polarographic results demonstrate that the "FeS" initially formed consists of (1) a complex of the form Fe(SH) + and (2) solid FeS. When excess polysulfide is present, a complex of form [Fe(SH) S x] - is present. This complex should readily allow for (1) the reduction of polysulfide by sulfide which produces S 22- in unprotonated form, and (2) the change of Fe(II) from high spin to low spin during the formation of pyrite. The reduction of polysulfide by sulfide was proposed by RICKARD (1975), but at the pH of the solutions studied herein, S 22- in solution should be protonated. The 22- ion is critical in the formation and structure of pyrite ( TOSSEL et al., 1981). The proposed complex allows for a cyclic intermediate which cleaves the reacting polysulfide to form S 22- unprotonated. As this process occurs, there is a change in the spin state of the Fe(II) from the high spin t 2g4e g2 to the low spin t 2g6 state which is an electron configuration exhibiting kinetic inertness. On change of the Fe(II) spin state, the complex irreversibly decomposes to form pyrite. The complex may be a cluster complex containing two or more

  7. Pyritized ooids from the Arabian Sea basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.; Rao, Ch.M.; Reddy, N.P.C.

    . Occurrence of pyrite at turbidite intervals suggests that pyritization in high organic carbon and H2S abundant environments was mainly controlled by the supply of reactive iron. From the distribution of pyrite in the core it is inferred that reactive iron...

  8. Bioflotation of pyrite with Thiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    Shaoxian Song; Yimin Zhang; Shouci Lu

    2004-01-01

    Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.

  9. Depressing effect of hydroxamic polyacrylamide on pyrite

    Institute of Scientific and Technical Information of China (English)

    张剑锋; 胡岳华; 王淀佐; 徐竞

    2004-01-01

    The performance of hydroxamic polyacrylamide(HPAM) in mineral flotation was tested on the samples of calcite, diaspore and pyrite. It is found that HPAM expresses intensive depression on pyrite and can be used as effective depressants for pyrite. The depression mechanism of HPAM to pyrite was investigated by the determination of contact angle, zeta potential, adsorptive capacity for collectors and infrared spectrum. A lower contact angle,more negative zeta potential, less xanthate adsorptive capacity, and the formation of chemical bonding were determined, which reveals that the strong chemical interactions exist between HPAM and pyrite surface. The group electronegativity of HPAM was calculated to explain the differences of interaction between reagent and minerals.

  10. Ultrasonic ash/pyrite liberation

    Energy Technology Data Exchange (ETDEWEB)

    Yungman, B.A.; Buban, K.S.; Stotts, W.F.

    1990-06-01

    The objective of this project was to develop a coal preparation concept which employed ultrasonics to precondition coal prior to conventional or advanced physical beneficiation processes such that ash and pyrite separation were enhanced with improved combustible recovery. Research activities involved a series of experiments that subjected three different test coals, Illinois No. 6, Pittsburgh No. 8, and Upper Freeport, ground to three different size fractions (28 mesh [times] 0, 200 mesh [times] 0, and 325 mesh [times] 0), to a fixed (20 kHz) frequency ultrasonic signal prior to processing by conventional and microbubble flotation. The samples were also processed by conventional and microbubble flotation without ultrasonic pretreatment to establish baseline conditions. Product ash, sulfur and combustible recovery data were determined for both beneficiation processes.

  11. Interaction between pyrite and cysteine

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-she; WANG Zhao-hui; LI Bang-mei; ZHANG Yan-hua

    2006-01-01

    The adsorption mechanism of cysteine on pyrite was studied by amounts adsorbed, FTIR and XRD measurements. The results obtained by adsorption experiment suggest that as the mass ratio of mineral to cysteine mp/mc is greater than 5, the amounts adsorbed on mineral is stable after adsorption for 15 min and cysteine adsorbing with mp/mc shows the same tendency. It can be inferred by its Langmuir-type adsorption isotherm that chemical interaction governs the entire adsorption process. The results from FTIR and XRD prove that the functional groups of cysteine appear with blue shift of their characteristic adsorption peak in FTIR spectrum; meanwhile, the lattice constant obviously decreases and the widening of crystal planes such as (210), (220) and (211) is found after cysteine adsorbing on mineral.

  12. Pyrite Stability Under Venus Surface Conditions

    Science.gov (United States)

    Kohler, E.; Craig, P.; Port, S.; Chevrier, V.; Johnson, N.

    2015-12-01

    Radar mapping of the surface of Venus shows areas of high reflectivity in the Venusian highlands, increasing to 0.35 ± 0.04 to 0.43 ± 0.05 in the highlands from the planetary average of 0.14 ± 0.03. Iron sulfides, specifically pyrite (FeS2), can explain the observed high reflectivity. However, several studies suggest that pyrite is not stable under Venusian conditions and is destroyed on geologic timescales. To test the stability of pyrite on the Venusian surface, pyrite was heated in the Venus simulation chamber at NASA Goddard Space Flight Center to average Venusian surface conditions, and separately to highland conditions under an atmosphere of pure CO2 and separately under an atmosphere of 96.5% CO2, 3.5% N2 and 150 ppm SO2. After each run, the samples were weighed and analyzed using X-Ray Diffraction (XRD) to identify possible phase changes and determine the stability of pyrite under Venusian surface conditions. Under a pure CO2 atmosphere, the Fe in pyrite oxidizes to form hematite which is more stable at higher temperatures corresponding to the Venusian lowlands. Magnetite is the primary iron oxide that forms at lower temperatures corresponding to the radar-bright highlands. Our experiments also showed that the presence of atmospheric SO2 inhibits the oxidation of pyrite, increasing its stability under Venusian conditions, especially those corresponding to the highlands. This indicates that the relatively high level of SO2 in the Venusian atmosphere is key to the stability of pyrite, making it a possible candidate for the bright radar signal in the Venusian highlands.

  13. THE DEPRESSION OF PYRITE FLOTATION BY THIOBACILLUS FERROOXIDANS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The experimental studies on the microbial flotation of a pure pyrite sample using Thiobacillus ferrooxidans was conducted in the laboratory. The results indicate that Thiobacillus ferrooaidans has strong depression effect on the flotation of pyrite. Thiobacillus f errooxidans can adsorb on the surface of pyrite in a very short time (a few min. ), changing the surface from hydrophobic into hydrophilic and making the pyrite particles to lose their floatability. Therefore, Thiobacillus ferrooxidans is an effective microbial depressant of pyrite. It has also been pointed out that the depression of pyrite by Thiobacillus ferrooxidans is caused by the adsorption of the microbial colloids, but not by the oxidation effect.

  14. Distribution of arsenic, selenium, and other trace elements in high pyrite Appalachian coals: evidence for multiple episodes of pyrite formation

    Science.gov (United States)

    Diehl, S.F.; Goldhaber, M.B.; Koenig, A.E.; Lowers, H.A.; Ruppert, L.F.

    2012-01-01

    Pennsylvanian coals in the Appalachian Basin host pyrite that is locally enriched in potentially toxic trace elements such as As, Se, Hg, Pb, and Ni. A comparison of pyrite-rich coals from northwestern Alabama, eastern Kentucky, and West Virginia reveals differences in concentrations and mode of occurrence of trace elements in pyrite. Pyrite occurs as framboids, dendrites, or in massive crystalline form in cell lumens or crosscutting veins. Metal concentrations in pyrite vary over all scales, from microscopic to mine to regional, because trace elements are inhomogeneously distributed in the different morphological forms of pyrite, and in the multiple generations of sulfide mineral precipitates. Early diagenetic framboidal pyrite is usually depleted in As, Se, and Hg, and enriched in Pb and Ni, compared to other pyrite forms. In dendritic pyrite, maps of As distribution show a chemical gradient from As-rich centers to As-poor distal branches, whereas Se concentrations are highest at the distal edges of the branches. Massive crystalline pyrite that fills veins is composed of several generations of sulfide minerals. Pyrite in late-stage veins commonly exhibits As-rich growth zones, indicating a probable epigenetic hydrothermal origin. Selenium is concentrated at the distal edges of veins. A positive correlation of As and Se in pyrite veins from Kentucky coals, and of As and Hg in pyrite-filled veins from Alabama coals, suggests coprecipitation of these elements from the same fluid. In the Kentucky coal samples (n = 18), As and Se contents in pyrite-filled veins average 4200 ppm and 200 ppm, respectively. In Alabama coal samples, As in pyrite-filled veins averages 2700 ppm (n = 34), whereas As in pyrite-filled cellular structures averages 6470 ppm (n = 35). In these same Alabama samples, Se averages 80 ppm in pyrite-filled veins, but was below the detection limit in cell structures. In samples of West Virginia massive pyrite, As averages 1700 ppm, and Se averages 270

  15. Catalytic activity of pyrite for coal liquefaction reaction; Tennen pyrite no shokubai seino ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, K.; Kozu, M.; Okada, T.; Kobayashi, M. [Nippon Coal Oil Co. Ltd., Tokyo (Japan)

    1996-10-28

    Since natural pyrite is easy to obtain and cheap as coal liquefaction catalyst, it is to be used for the 150 t/d scale NEDOL process bituminous coal liquefaction pilot plant. NEDO and NCOL have investigated the improvement of catalytic activity of pulverized natural pyrite for enhancing performance and economy of the NEDOL process. In this study, coal liquefaction tests were conducted using natural pyrite catalyst pulverized by dry-type bowl mill under nitrogen atmosphere. Mechanism of catalytic reaction of the natural pyrite was discussed from relations between properties of the catalyst and liquefaction product. The natural pyrite provided an activity to transfer gaseous hydrogen into the liquefaction product. It was considered that pulverized pyrite promotes the hydrogenation reaction of asphaltene because pulverization increases its contact rate with reactant and the amount of active points on its surface. It was inferred that catalytic activity of pyrite is affected greatly by the chemical state of Fe and S on its surface. 3 refs., 4 figs., 1 tab.

  16. Pyrite Oxidation Related to Pyritic Minesite Spoils and Its Controls:A Review

    Institute of Scientific and Technical Information of China (English)

    郑作平; H.H.GERKE; 等

    1998-01-01

    Pyrite oxidation is considered to be a main contribution to the acidification of minesite spoils and the generation of the Acid Mine Drainage(AMD) which has become the greatest threat to the ecological environment,In this paper,pyrite oxidation and its controls are reviewed with respect to the latest literature,conceptual Model and empirical rate law model with reference to indoor experiments are classified and presented to describe pyrite oxidation in heterogeneous minesite spoil piles.The influences of Thiobacillus(T) ferrooxidans on pyrite oxidation are simply summarized.In order to prevent the generation of the AMD,three approaches including the addition of alkali to minesite spoil,use of dry covers,and coating on the minesite spilk surface,are discussed.

  17. Nucleic acid interactions with pyrite surfaces

    Science.gov (United States)

    Mateo-Martí, E.; Briones, C.; Rogero, C.; Gomez-Navarro, C.; Methivier, Ch.; Pradier, C. M.; Martín-Gago, J. A.

    2008-09-01

    The study of the interaction of nucleic acid molecules with mineral surfaces is a field of growing interest in organic chemistry, origin of life, material science and biotechnology. We have characterized the adsorption of single-stranded peptide nucleic acid (ssPNA) on a natural pyrite surface, as well as the further adsorption of ssDNA on a PNA-modified pyrite surface. The characterization has been performed by means of reflection absorption infrared spectroscopy (RAIRS), atomic force microscopy (AFM) and X-ray photoemission spectroscopy (XPS) techniques. The N(1s) and S(2p) XPS core level peaks of PNA and PNA + DNA have been decomposed in curve-components that we have assigned to different chemical species. RAIRS spectra recorded for different concentrations show the presence of positive and negative adsorption bands, related to the semiconducting nature of the surface. The combination of the information gathered by these techniques confirms that PNA adsorbs on pyrite surface, interacting through nitrogen-containing groups of the nucleobases and the iron atoms of the surface, instead of the thiol group of the molecule. The strong PNA/pyrite interaction inhibits further hybridization of PNA with complementary ssDNA, contrary to the behavior reported on gold surfaces.

  18. Pyrite oxidation by Acidithiobacillus ferrooxidans bacteria

    Directory of Open Access Journals (Sweden)

    Savić Dragiša S.

    2005-01-01

    Full Text Available The kinetic model of pyrite particle dissolution by the action of bacteria Acidithiobacillus ferrooxidans in a shaken Erlenmeyer flask was presented. The model agreed well with the experimental data for the extracted iron and the number of cells in the liquid phase. The specific growth rate of the adsorbed cells was evaluated (μA = 1,6 d-1 by fitting the experimental data to the model curve. Also, the relevance of the two proposed mechanisms for the bacterial dissolution of sulphide (direct and indirect was discussed, indicating that the indirect one was dominant. The adsorption process of A. ferrooxidans to the pyrite surface was well correlated by a Langmuir type isotherm.

  19. The Adsorption of Cu Species onto Pyrite Surface and Its Effect on Pyrite Flotation

    Directory of Open Access Journals (Sweden)

    Bo Yang

    2016-01-01

    Full Text Available The adsorption of Cu species onto pyrite surface and its effect on flotation were investigated by using microflotation tests, first-principle calculations, and XPS surface analysis. The results indicated that the flotation of pyrite appears to be activated with CuSO4 only at alkaline pH, while being depressed at acidic and neutral pH. The adsorption of copper ions on pyrite surface was pH-dependent, and the adsorption magnitude of copper ions at alkaline pH is higher than that at acidic and neutral pH due to a strong interaction between O atom in Cu(OH2 and surface Fe atom except for the interaction between Cu atom and surface S atom. At acidic and neutral pH, there is only an interaction between Cu atom and surface S atom. The adsorption was relatively weak, and more copper ions in solution precipitated the collector and depressed the flotation of pyrite. XPS analysis confirmed that more copper ionic species (Cu(I and Cu(II are adsorbed on the pyrite surface at alkaline pH than that at acidic and neutral pH.

  20. Utilization of coal-derived pyrite by electrolysis

    Institute of Scientific and Technical Information of China (English)

    LI Deng-xin; M.Makino; GAO Jin-sheng; MENG Fan-l ing

    2001-01-01

    The utilization of coal-derived pyrite by electrolysis was studie d. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe 3+ and SO2-4, and the no pollutant is drained off. In this paper, the infl uence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increase s with the rise of potential, time, temperature, acidity and the concentration o f additive agent, but decreases with the rise of concentration of pyrite. At th e certain conditions (at the potential of 3.0 V, temperature of 298 K, time of 12 h , the concentration of MnSO4 of 6%, concentration of pyrite of 4%, and concent ra tion of acid of 10%), Cr is high to 93%. In the same time, the mechanism of elec trolysis of pyrite was provided. The electrolysis of pyrite is actually the r ecycle of Mn ion between anodic surface and pyrite. At last, the production of F eSO4*7H2O through electrolysis of pyrite was introduced.

  1. Utilization of coal-derived pyrite by electrolysis

    Institute of Scientific and Technical Information of China (English)

    李登新; M.Makinot; 高晋生; 孟繁玲

    2001-01-01

    The utilization of coal-derived pyrite by electrolysis was studied. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe3+ and SO2-4, and the no pollutant is drained off. In this paper, the influence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increases with the rise of potential, time, temperature, acidity and the concentration of additive agent, but decreases, with the rise of concentration of pyrite. At the certain conditions (at the potential of 3.0 V, temperature of 298 K, time of 12 h, the concentration of MnSO4 of 6%, concentration of pyrite of 4%, and concentration of acid of 10%), Cr is high to 93%. In the same time, the mechanism of electrolysis of pyrite was provided. The electrolysis of pyrite is actually the recycle of Mn ion between anodic surface and pyrite. At last, the production of FeSO4·7H2O through electrolysis of pyrite was introduced.

  2. Effects of pyrite on the spontaneous combustion of coal

    Institute of Scientific and Technical Information of China (English)

    Jun Deng; Xiaofeng Ma; Yutao Zhang; Yaqing Li; Wenwen Zhu

    2015-01-01

    Pyrite has a significant effect on the spontaneous combustion of coal. The presence of pyrite can change the propensity of coal towards spontaneous combustion. The influences of various pyrite contents on the parameters of spontaneous combustion, such as index gases, temperature and released heat etc., were investigated in this study. Coal samples with different pyrite contents (0%, 3%, 5%, 7%and 9%) were made by mixing coal and pyrite. The oxidation experiments under temperature-programmed condition were carried out to test the release rate of gaseous oxidation products at different temperatures. Differential scanning calorimeter (DSC) was employed to measure the intensity of heat release during coal oxidation for various pyrite contents. The results indicate that pyrite can nonlinearly accelerate the process of spontaneous combustion. The coal sample with a pyrite content of 5% has the largest CO release rate and oxygen adsorption as well. However, the coal sample with a pyrite content of 7% has the largest rate of heat flow according to the results from the DSC tests. Pyrite contents of 5%–7% in coal has the most significant effects on spontaneous combustion within the range of this study. The conclusions are conducive to the evaluation and control for the spontaneous combustion of coal.

  3. Interfacial interaction of bio-leaching of pyrite mineral

    Institute of Scientific and Technical Information of China (English)

    GU Guo-hua; WANG nui; SUO Jun; QIU Guan-zhou; HAO Ye

    2008-01-01

    Electrokinetic and contact angle measurements were used to discuss the interracial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobaeillus ferrooxidans were Gbtained by calculating according to formula of Young's equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobacillus ferrooxidans were also obtained based onpolar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but theextended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interracial interaction.

  4. Thermoacidophilic archaea for pyrite oxidation in coal desulphurization

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Liselotte

    1995-10-01

    The desulfurization of low-sulfur coals has been demonstrated with the thermoacidophilic archaeon Acidianus brierleyi. A. brierleyi facilitates the removal of inorganic sulfur from coal and oxidizes mineral pyrite. The results imply that the mechanism behind microbial coal desulfurization and pyrite oxidation is a combination of biotic and abiotic leaching of pyrite. The extent of sulfur removal is dependent on the type of coal and is closely related to he amount of pyritic sulfur in the coal. Studies have shown that neither ash content nor heating value were dramatically affected by the microbial treatment. The use of the archaea Sulfolobus acidocaldarius and Sulfolobus solfataricus, as well as the mesophilic bacteria Thiobacillus ferrooxidans and several Pseudomonas species, has also been studied for coal desulfurization and mineral pyrite oxidation. The archaea and Pseudomonas species did not grow autotrophically on mineral pyrite neither did they oxidize pyrite in coal. The oxidation rate was, however, 5-10 times less than with A. brierleyi on mineral pyrite. The rate of sulfur removal from coal was in the same range as for A. brierleyi which indicates that different reactions are rate limiting in coal depyritization than in mineral pyrite oxidation. 133 refs, 18 figs, 3 tabs

  5. Pyritic ash-flow tuff, Yucca Mountain, Nevada -- A discussion

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Larson, L.T.; Noble, D.C. [Univ. of Nevada, Reno, NV (United States)

    1994-12-31

    Textural and mineralogic evidence exists for at least one episode of widespread hydrothermal alteration of volcanic rocks deep in Yucca Mountain, Nevada. Despite this evidence, Castor et al. infer that most of the pyrite found in tuffs at Yucca Mountain was introduced as ejecta (lithic fragments) incorporated during the eruptions of the tuffs, rather than by in-situ hydrothermal activity. Their conclusions appear to be based on their observation that most of the pyrite resides in unaltered to variably altered and veined lithic fragments, whereas pyrite-bearing veins are absent in the tuff matrix, titanomagnetite and mafic phenocrysts in the matrix are generally not replaced by pyrite, and feldspar phenocrysts in the pyritic tuff matrix are generally unaltered. Castor et al. dismiss the much smaller quantities of pyrite disseminated in the tuff matrix, including relatively rare pyritized hornblende and biotite grains, as xenolithic as well. The pyritic tuffs belong to large-volume, subalkaline rhyolite ash-flow units (ca. > 150 to 250 km{sup 3} each). The interpretation of Castor et al. has broad implications for the temperature, fO{sub 2} and fS{sub 2} of major ash flow eruptions. Pyrite origin also bears on the nature of past fluid flow and water-rock reactions at Yucca Mountain, which in turn are important factors in assessing the potential for currently undiscovered mineral resources in the area of the proposed nuclear waste repository. We have studied core and cuttings from the same drill holes studied by Castor et al., as well as other drill holes. It is our contention that the inconsistent lateral and stratigraphic distribution of the pyrite, textural features of the pyrite, and phase stability considerations are incompatible with the {open_quotes}lithic{close_quotes} origin of Castor et al., and are more reasonably explained by in-situ formation from hydrothermal fluids containing low, but geochemically significant, concentrations of reduced sulfur.

  6. Pyrite Surface after Thiobacillus ferrooxidans Leaching at 30℃

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to investigate the effect of Thiobacillus ferrooxidans on the oxidation of pyrite, two parallel experiments, which employed H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans, were designed and carried out at 30℃. The initial pH of the two solutions was adjusted to 2.5 by dropwise addition of concentrated sulphuric acid. The surfaces of pyrite before exposure to leaching solutions and after exposure to the H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans were observed by scanning electron microscopy (SEM). There were a variety of erosion patterns by Thiobacillusferrooxidans on the bio-leached pyrite surfaces. A conclusion can be drawn that the oxidation of pyrite might have been caused by erosion of the surfaces.Attachment of the bacteria to pyrite surfaces resulted in erosion pits, leading to the oxidation of pyrite.It is possible that the direct mechanism plays the most important role in the oxidation of pyrite. The changes in iron ion concentrations of both the experimental solutions with time suggest that Thiobacillus ferrooxidans can enhance greatly the oxidation of pyrite.

  7. Selective separation of pyrite and chalcopyrite by biomodulation.

    Science.gov (United States)

    Chandraprabha, M N; Natarajan, K A; Modak, Jayant M

    2004-09-01

    Selective separation of pyrite from other associated ferrous sulphides at acidic and neutral pH has been a challenging problem. This paper discusses the utility of Acidithiobacillus ferrooxidans for the selective flotation of chalcopyrite from pyrite. Consequent to interaction with bacterial cells, pyrite remained depressed even in the presence of potassium isopropyl xanthate collector while chalcopyrite exhibited significant flotability. However, when the minerals were conditioned together, the selectivity achieved was poor due to the activation of pyrite surface by the copper ions in solution. The selectivity was improved when the sequence of conditioning with bacterial cells and collector was reversed, since the bacterial cells were able to depress collector interacted pyrite effectively, while having negligible effect on chalcopyrite. The observed behaviour is analysed and discussed in detail. The separation obtained was significant both at acidic and alkaline pH. This selectivity achieved was retained when the minerals were interacted with both bacterial cells and collector simultaneously.

  8. An improved pyrite pretreatment protocol for kinetic and isotopic studies

    Science.gov (United States)

    Mirzoyan, Natella; Kamyshny, Alexey; Halevy, Itay

    2014-05-01

    An improved pyrite pretreatment protocol for kinetic and isotopic studies Natella Mirzoyan1, Alexey Kamyshny Jr.2, Itay Halevy1 1Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, and the microbiological processes involved. Pretreatment of pyrite for removal of oxidation impurities to prevent experimental artifacts and inaccuracies is often practiced. While numerous pyrite-cleaning methods have been used in experiments, a common pyrite pretreatment method, often used to investigate pyrite chemistry by the isotopic fractionations associated with it, includes several rinses by HCl, acetone and deionized water. Elemental sulfur (S0) is a common product of incomplete pyrite oxidation. Removal of S0 is desirable to avoid experimental biases associated with its participation in pyrite transformations, but is more complicated than the removal of sulfate. Although rinsing with an organic solvent is in part aimed at removing S0, to the best of our knowledge, the extraction efficiency of S0 in existing protocols has not been assessed. We have developed and tested a new protocol for elemental sulfur removal from the surface of pyrite by ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S0 on untreated pyrite particle surfaces, of which only approximately 60% was removed by the commonly used pretreatment method. The new protocol described here was found to be more efficient at S0 removal than the commonly used method

  9. Greigite: a true intermediate on the polysulfide pathway to pyrite

    Directory of Open Access Journals (Sweden)

    Benning Liane G

    2007-03-01

    Full Text Available Abstract The formation of pyrite (FeS2 from iron monosulfide precursors in anoxic sediments has been suggested to proceed via mackinawite (FeS and greigite (Fe3S4. Despite decades of research, the mechanisms of pyrite formation are not sufficiently understood because solid and dissolved intermediates are oxygen-sensitive and poorly crystalline and therefore notoriously difficult to characterize and quantify. In this study, hydrothermal synchrotron-based energy dispersive X-ray diffraction (ED-XRD methods were used to investigate in situ and in real-time the transformation of mackinawite to greigite and pyrite via the polysulfide pathway. The rate of formation and disappearance of specific Bragg peaks during the reaction and the changes in morphology of the solid phases as observed with high resolution microscopy were used to derive kinetic parameters and to determine the mechanisms of the reaction from mackinawite to greigite and pyrite. The results clearly show that greigite is formed as an intermediate on the pathway from mackinawite to pyrite. The kinetics of the transformation of mackinawite to greigite and pyrite follow a zero-order rate law indicating a solid-state mechanism. The morphology of greigite and pyrite crystals formed under hydrothermal conditions supports this conclusion and furthermore implies growth of greigite and pyrite by oriented aggregation of nanoparticulate mackinawite and greigite, respectively. The activation enthalpies and entropies of the transformation of mackinawite to greigite, and of greigite to pyrite were determined from the temperature dependence of the rate constants according to the Eyring equation. Although the activation enthalpies are uncharacteristic of a solid-state mechanism, the activation entropies indicate a large increase of order in the transition state, commensurate with a solid-state mechanism.

  10. Pyrite surface characterization and control for advanced fine coal desulfurization technologies

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang-Huai.

    1991-01-01

    The objective of this project is to conduct extensive studies on the surface reactivity of pyrite by using electrochemical, surface analysis, potentiometric and calorimetric titration, and surface hydrophobicity characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The products as well as their structure, the mechanisms and the kinetics of the oxidation of coal-pyrite surfaces and their interaction with various chemical reagents will be systematically studied and compared with that of mineral-pyrite and synthetic pyrite to determine the correlation between the surface reactivity of pyrite and the bulk chemical properties of pyrite and impurities. The surface chemical studies and the studies of floatability of coal-pyrite and the effect of various parameters such as grinding media and environment, aging under different atmospheres, etc. on thereof, are directed at identifying the causes and possible solutions of the pyrite rejection problems in coal cleaning.

  11. The effect of quartz on the flotation of pyrite depressed by serpentine

    Directory of Open Access Journals (Sweden)

    Bo Feng

    2015-01-01

    Full Text Available The effect of quartz particles on the flotation of pyrite depressed by serpentine has been investigated through flotation tests, adsorption tests, zeta potential measurements and DLVO calculation. The results show that the presence of hydrophilic serpentine slimes on pyrite surface reduces collector adsorption and results in lower recovery of pyrite. The finer the serpentine slime is, the lower the pyrite recovery will be. Quartz particles do not interfere with pyrite flotation. However, the addition of quartz particles increases the adsorption of collector on pyrite surface and limits the detrimental effect of serpentine on pyrite flotation. The fine-grained quartz is more effective. Zeta potential measurements and DLVO calculation illustrate that the zeta potential of quartz is more negative than that of pyrite and the attraction force between serpentine and quartz is stronger than force between serpentine and pyrite, thus some serpentine slimes were transferred from pyrite surface to quartz in the process of attrition.

  12. Electrodeposition of dixanthogen(TETD) on pyrite surface

    Institute of Scientific and Technical Information of China (English)

    LI Wei-zhong; QIN Wen-qing; SUN Wei; QIU Guan-zhou

    2007-01-01

    The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements. Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion, and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface. The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09×10-6 cm2/s. Using the galvanostatic technique, the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as Ja=200 μA/cm2, β= 0.203 and J0=27.1 μA/cm2.

  13. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively. Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→ pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  14. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    WANG Lei; PAN YongXin; LI JinHua; QIN HuaFeng

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively.Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  15. Nannobacteria and the formation of framboidal pyrite: Textural evidence

    Indian Academy of Sciences (India)

    Robert L Folk

    2005-06-01

    Study of sedimentary pyrite in the form of framboids, euhedral crystals or metasomatic masses has revealed that their surfaces are commonly covered with spheroids of about 50 nm. This applies to all the examples studied, from modern to Proterozoic. These spheroids are interpreted as the pyritized corpses of nannobacterial cells; if correct, this indicates that precipitation of iron sulfide was performed by these dwarf forms of bacteria, often associated with decaying organic matter.

  16. Rapid method to determine proximate analysis and pyritic sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, M.W.; Hyman, M.

    1985-05-01

    The use of thermomagnetogravimetry has been proposed as an alternative to the ASTM methods for measuring the pyritic sulphur content of coal and for proximate analysis. This paper presents a comparison of the results of thermogravimetry for proximate analysis and thermomagnetometry for pyritic sulphur with ASTM values on the same samples. The thermomagnetogravimetric technique is quicker and easier than the ASTM methods, and of comparable accuracy.

  17. Enabling iron pyrite (FeS2) and related ternary pyrite compounds for high-performance solar energy applications

    Science.gov (United States)

    Caban Acevedo, Miguel

    The success of solar energy technologies depends not only on highly efficient solar-to-electrical energy conversion, charge storage or chemical fuel production, but also on dramatically reduced cost, to meet the future terawatt energy challenges we face. The enormous scale involved in the development of impactful solar energy technologies demand abundant and inexpensive materials, as well as energy-efficient and cost-effective processes. As a result, the investigation of semiconductor, catalyst and electrode materials made of earth-abundant and sustainable elements may prove to be of significant importance for the long-term adaptation of solar energy technologies on a larger scale. Among earth-abundant semiconductors, iron pyrite (cubic FeS2) has been considered the most promising solar energy absorber with the potential to achieve terawatt energy-scale deployment. Despite extensive synthetic progress and device efforts, the solar conversion efficiency of iron pyrite has remained below 3% since the 1990s, primarily due to a low open circuit voltage (V oc). The low photovoltage (Voc) of iron pyrite has puzzled scientists for decades and limited the development of cost-effective solar energy technologies based on this otherwise promising semiconductor. Here I report a comprehensive investigation of the syntheses and properties of iron pyrite materials, which reveals that the Voc of iron pyrite is limited by the ionization of a high density of intrinsic bulk defect states despite high density surface states and strong surface Fermi level pinning. Contrary to popular belief, bulk defects most-likely caused by intrinsic sulfur vacancies in iron pyrite must be controlled in order to enable this earth-abundant semiconductor for cost-effective and sustainable solar energy conversion. Lastly, the investigation of iron pyrite presented here lead to the discovery of ternary pyrite-type cobalt phosphosulfide (CoPS) as a highly-efficient earth-abundant catalyst material for

  18. Pyrite and pyritic mill tailing as a source of iron in a calcareous iron-deficient soil

    Energy Technology Data Exchange (ETDEWEB)

    Barrau, E.M.; Berg, W.A.

    1977-01-01

    Mill wastes from ore processing, particularly acid-forming pyrites, often pose disposal problems. This greenhouse study evaluated pyrite and a pyritic mill tailing as Fe sources on an Fe-deficient calcareous soil. Pyrite and tailing <0.1 mm in diameter were applied at rates of 45 and 135 metric ton/ha. Controls, 200 and 600 ppM Fe as Fe/sub 2/(SO/sub 4/)/sub 3/ and 5 and 15 ppM Fe as FeEDDHA, were used as standards. The treatments were seeded with sudangrass (Sorghum vulgare sudanense) and six successive crops were harvested. Sudangrass yields increased 160 to 200% with pyrite and tailing treatments; these yields were significantly greater than the control and were comparable to yields from the other Fe sources. The 5 ppM FeEDDHA treatment, however, increased yield for only the first two crops. Plant-available soil Fe measured by DTPA extraction increased with all Fe treatments, while the levels of DTPA-extractable Zn and Mn remained the same or increased slightly. DTPA-extractable Cu doubled with the high rate of pyrite addition. The concentration of Fe in the plants remained the same or increased slightly with the Fe treatments, while concentrations of Zn, Cu, and Mn all decreased.

  19. Geochemical characteristics of pyrite in Duolanasayi gold deposit, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    CHEN Guodong; XIAO Huiliang; WANG Henian; ZHOU Jiyuan

    2005-01-01

    The Duolanasayi gold deposit, 60 km NW of Habahe County, Xinjiang Uygur Autonomous Region, is a mid-large-scale gold deposit controlled by brittle-ductile shearing, and superimposed by albitite veins and late-stage magma hydrothermal solutions. There are four types of pyrite, which are contained in the light metamorphosed rocks (limestone, siltstone), altered-mineralized rocks (chlorite-schist, altered albite-granite, mineralized phyllite), quartz veins and carbonatite veinlets. The pyrite is the most common ore mineral. The Au-barren pyrite is present mainly in a simple form and gold-bearing pyrite is present mainly in a composite form. From the top downwards, the pyrite varies in crystal form from {100} and {210}+{100} to {210}+{100}+{111} to {100}+{111}. Geochemical studies indicate that the molecular contents of pyrite range from Fe1.057S2 to Fe0.941S2. Gold positively correlates with Mn, Sr, Zn, Te, Pb, Ba and Ag. There are four groups of trace elements: Fe-Cu-Sr-Ag, Au-Te-Co, As-Pb-Zn and Mn-V-Ti-Ba-Ni-Cr in pyrite. The REE characteristics show that the total amount of REE (ΣREE) ranges from 32.35×10 -6 to 132.18×10 -6; LREE/HREE, 4.466-9.142; (La/Yb)N, 3.719-11.133; (Eu/Sm)N, 0.553-1.656; (Sm/Nd)N, 0.602-0.717; La/Yb, 6.26-18.75; δEu, 0.628-2.309; δCe, 0.308-0.816. Sulfur isotopic compositions (δ 34S=-2.46‰--7.02‰) suggest that the sulfur associated with gold mineralization was derived from the upper mantle or lower crust.

  20. Arsenic incorporation into authigenic pyrite, Bengal Basin sediment, Bangladesh

    Science.gov (United States)

    Lowers, H.A.; Breit, G.N.; Foster, A.L.; Whitney, J.; Yount, J.; Uddin, Md. N.; Muneem, Ad. A.

    2007-01-01

    Sediment from two deep boreholes (???400 m) approximately 90 km apart in southern Bangladesh was analyzed by X-ray absorption spectroscopy (XAS), total chemical analyses, chemical extractions, and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the Bengal Basin. Authigenic framboidal and massive pyrite (median values 1500 and 3200 ppm As, respectively), is the principal arsenic residence in sediment from both boreholes. Although pyrite is dominant, ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment-bound arsenic between approximately 20 and 100 m, which is the depth range of wells containing the greatest amount of dissolved arsenic. The lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources. The ability of deeper aquifers (>150 m) to produce ground water with low dissolved arsenic in southern Bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis.

  1. Pyrite oxidation under simulated acid rain weathering conditions.

    Science.gov (United States)

    Zheng, Kai; Li, Heping; Wang, Luying; Wen, Xiaoying; Liu, Qingyou

    2017-07-31

    We investigated the electrochemical corrosion behavior of pyrite in simulated acid rain with different acidities and at different temperatures. The cyclic voltammetry, polarization curve, and electrochemical impedance spectroscopy results showed that pyrite has the same electrochemical interaction mechanism under different simulated acid rain conditions, regardless of acidity or environmental temperature. Either stronger acid rain acidity or higher environmental temperature can accelerate pyrite corrosion. Compared with acid rain having a pH of 5.6 at 25 °C, the prompt efficiency of pyrite weathering reached 104.29% as the acid rain pH decreased to 3.6, and it reached 125.31% as environmental temperature increased to 45 °C. Increasing acidity dramatically decreases the charge transfer resistance, and increasing temperature dramatically decreases the passivation film resistance, when other conditions are held constant. Acid rain always causes lower acidity mine drainage, and stronger acidity or high environmental temperatures cause serious acid drainage. The natural parameters of latitude, elevation, and season have considerable influence on pyrite weathering, because temperature is an important influencing factor. These experimental results are of direct significance for the assessment and management of sulfide mineral acid drainage in regions receiving acid rain.

  2. Hydrogeologic and environmental impact of amjhore pyrite mines, India

    Science.gov (United States)

    Choubey, Vishnu D.; Rawat, Rajendra K.

    1991-01-01

    Drainage from active and inactive pyrite mines has produced chemical and physical pollution of both ground- and surface water in Amjhore region. In the present case, chemical pollution is caused by exposing pyrite minerals to oxidation or leaching, resulting in undesirable concentrations of dissolved materials. Pyrite mining suddenly exposed large quantities of sulfides to direct contact with oxygen, and oxidation proceeds rapidly, resulting in acidity and release of metal (Fe) and sulfates to the water system, eventually resulting in water pollution in the region. The magnitude and impact of the problem is just being recognized and, as the present and the future projected demand for clean water is of top priority, the present studies were undertaken. Mine drainage includes water flowing from the surface and underground mines and runoff or seepage from the pyrite mines. This article describes the various hydrologic factors that control acid water formation and its transport. The mine drainage is obviously a continuing source of pollution and, therefore, remedial measures mainly consisting of a double-stage limestone-lime treatment technique have been suggested. The present results will be used to develop an alternative and more effective abatement technology to mitigate acid production at the source, namely, the technique of revegetation of the soil cover applied to the waste mine dump material. Water quality change is discussed in detail, with emphasis on acidity formed from exposed pyrite material and on increase in dissolved solids. Preventive and treatment measures are recommended.

  3. Hydrogeological and environmental impact of Amjhore pyrite mines, India

    Energy Technology Data Exchange (ETDEWEB)

    Choubey, V.D.; Rawat, R.K. (Indian School of Mines, Dhanbad (India))

    Drainage from active and inactive pyrite mines has produced chemical and physical pollution of both ground and surface water in Amjhore region. In the present case, chemical pollution is caused by exposing pyrite minerals to oxidation or leaching, resulting in undesirable concentrations of dissolved materials. Pyrite mining suddenly exposed large quantities of sulfides to direct contact with oxygen, and oxidation proceeds rapidly, resulting in acidity and release of metal (Fe) and sulfates to the water system, eventually resulting in water pollution in the region. The magnitude and impact of the problem is just being recognized and, as the present and the future projected demand for problem demand for clean water is of top priority, the present studies were undertaken. Mine drainage includes water flowing from the surface and underground mines and runoff or seepage from the pyrite mines. This article describes the various hydrologic factors that control acid water formation and its transport. The mine drainage is obviously a continuing source of pollution and, therefore, remedial measures mainly consisting of a double-stage limestone-lime treatment technique have been suggested. The present results will be used to develop an alternative and more effective abatement technology to mitigate acid production at the source, namely, the technique of revegetation of the soil cover applied to the waste mine dump material. Water quality change is discussed in detail, with emphasis on acidity formed from exposed pyrite material and on increase in dissolved solids. Preventive and treatment measures are recommended.

  4. A study of the interfacial chemistry of pyrite and coal in fine coal cleaning using flotation

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Chengliang [Univ. of Kentucky, Lexington, KY (United States)

    1993-01-01

    Surface oxidation, surface charge, and flotation properties have been systematically studied for coal, coal-pyrite and ore-pyrite. Electrochemical studies show that coal-pyrite exhibits much higher and more complex surface oxidation than ore-pyrite and its oxidation rate depends strongly on the carbon/coal content. Flotation studies indicate that pyrites have no self-induced floatability. Fuel oil significantly improves the floatability of coal and induces considerable flotation for coal-pyrite due to the hydrophobic interaction of fuel oil with the carbon/coal inclusions on the pyrite surface. Xanthate is a good collector for ore-pyrite but a poor collector for coal and coal-pyrite. The results from thermodynamic calculations, flotation and zeta potential measurements show that iron ions greatly affect the flotation of pyrite with xanthate and fuel oil. Various organic and inorganic chemicals have been examined for depressing coal-pyrite. It was found, for the first time, that sodium pyrophosphate is an effective depressant for coal-pyrite. Solution chemistry shows that pyrophosphate reacts with iron ions to form stable iron pyrophosphate complexes. Using pyrophosphate, the complete separation of pyrite from coal can be realized over a wide pH range at relatively low dosage.

  5. Biogenic syngenetic pyrite from tuffaceous sedimentary RF3-V rocks

    Science.gov (United States)

    Kozyreva, Irina; Nikulova, Natalia

    2015-04-01

    Biogenic framboidal pyrite was found in intraformational tuffaceous sedimentary gravelites, within basic volcanites (RF3-V) in Subpolar Urals (Sablya Ridge). Pyrite grains (Fe 44.07-44,33, S 50.22-53.31 wt. %) are composed of ball-like microconcretions, sometimes intergrown with crystals of pentagondodecahedron and cubic habit. The microconcretions (20 to 40 mcm) are roundish and composed of microcrystals, which end faces form spherical surface. The nuclei of the microconcretions are represented by frambohedrons 4-5 mcm in size, which are pyritized cells of sulphate-reducing colonial coccoid microfossils. The formation of the frambohedrons occurred synchronously to sedimentation in stagnant reducing environment at interaction of biogenic hydrogen sulphide with water-dissolved iron. The biogenic hydrogen sulphide is reduced by microorganisms in the conditions of free and unrestricted access of dissolved sulphate ions sourced from sulphur of fumarole gases. Iron came from washed-out basic volcanites. The growth of outer radial parts of microconcretions occurred during compaction of sediments in diagenetic stage. The quantity of dissolved sulphate and iron during pyrite formation exceeded possibilitites of bacterial "starters" which resulted in the formation of pyrites of other morphological varieties. This is confirmed by the accretion of concentric rays of the concretions and cubic microcrystals of pyrite in the aggregate grains. The formation of tuffaceous sediments occurred during temporary decrease of volcanic activity in a continuous linear water flow with stagnant areas composed of water-displaced pebbles from underlying metaterrigenous rocks (RF 1-2), which were exposed beyond the development area of volcanic strata, unchanged clasts of recent and synchronously formed basic and medium volcanites with participation of air-driven ashes and influence of volcanic gases in the presence of sulphate-reducing bacteria. The work is financially supported by the Program

  6. Mechanism of separating pyrite and dolomite by flotation

    Institute of Scientific and Technical Information of China (English)

    Anping Liu; Wen Ni; Wei Wu

    2007-01-01

    To study the mechanism of separating pyrite and dolomite by flotation, the acting mechanisms of WHL depressor and both the minerals were studied by means of thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrareddiffuse reflection spectroscopy (FTIR-DRS), and X-ray photoelectron spectroscopy (XPS). The results indicated that WHL formed metal salts with metal ions dissolved in water from dolomite and pyrite, which then deposited on their surfaces. Both of the minerals could be depressed by WHL. In the process of flotation, sulfur was created besides the WHL being absorbed on the surface of the sulfur concentrate, and its recovery rate was slightly affected.

  7. SEM and AFM images of pyrite surfaces after bioleaching by the indigenous Thiobacillus thiooxidans.

    Science.gov (United States)

    Liu, H-L; Chen, B-Y; Lan, Y-W; Cheng, Y-C

    2003-09-01

    The bioleaching mechanism of pyrite by the indigenous Thiobacillus thiooxidans was examined with the aid of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the pyrite surface. The presence of pyrite eliminated the lag phase during growth of this microorganism. This was due to the stimulatory effect on cell growth of the slight amount of Cu2+ that had leached from the pyrite. Zn2+ was found to be much more readily solubilized than Cu2+. The efficiency of bioleaching was four times higher than that of chemical leaching. SEM images provided evidence of direct cell attachment onto the pyrite surface, thereby enhancing the bioleaching rate. Furthermore, extracellular polymeric substances (EPSs) were found on the pyrite surface after 4 days of oxidation. AFM images showed that the pyrite surface area positively correlated with the oxidation rate. A combination of direct and indirect mechanism is probably responsible for the oxidation of pyrite by T. thiooxidans.

  8. Study of possibilities of pyrite content reduction in black coals from the Mecsek Area

    Energy Technology Data Exchange (ETDEWEB)

    Petho, S.; Bokanyi, L.

    1985-01-01

    Certain parts of the pyrite content of coals can be removed by physical methods in inorganic form. The pyrite content of the Hungarian black coals as well as the pyrite distribution, as a function of density and grain size, are discussed. Based on literature data and laboratory experiments the pyrite content reduction by means of flotation, magnetic and gravitation enrichment is dealt with. Conclusions are drawn on how to apply these different procedures in black coal processing in Hungary.

  9. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Osseo-Asare, K.; Wei, D.

    1996-01-01

    This project is concerned with the physiochemical processes occuring at the pyrite/aqueous interface, in the context of coal cleaning, desulfurization, and acid mine drainage. The use of synthetic particles of pyrite as model electrodes to investigate the semiconductor electrochemistry of pyrite is employed.

  10. Galvanic interaction between galena and pyrite in an open system

    Institute of Scientific and Technical Information of China (English)

    ZHOU Li; LI Heping; XU Liping

    2006-01-01

    Galvanic interactions between sulfide minerals have very important influences on hydrometallurgical processes, the supergene enrichment of sulfides and the formation of acid mine drainage. By changing the concentrations of Fe3 + , the pH values, status of the flowing of the solution and the solution salinity ( e. g. the concentrations of Na2 SO4 ) and monitoring the galvanic currents and potentials, studies were conducted in this work on the galvanic interaction between pyrite acting as the anode and galena acting as the cathode. The results indicated that the concentrations of Fe3 + , pH values and the flowing of the solution exhibit a great effect on the galvanic interaction of galena-pyrite couple, while the salinity of the solution has only a slight influence on the interaction. The experiments also revealed that in case cracks exist on the surface of pyrite electrode, the potential of pyrite will decrease so sharply as to be lower than that of galena under the same experimental condition. The experimental results were explained in terms of the Butler-Volume equation and the theory of mixed potential.

  11. Contribution of microorganisms to the oxidation of pyrite

    NARCIS (Netherlands)

    Arkesteyn, G.J.M.W.

    1980-01-01

    Optimum conditions for the accumulation of substantial amounts of pyrite (FeS 2 ) in the sediment are found in estuarine areas, especially in the tropics. In such areas anaerobic conditions prevail owing to continuous saturation with water. There is an abundant supply of organic matter, i

  12. Characterization and separation of pyrite from Abu Tartur black shale

    Institute of Scientific and Technical Information of China (English)

    Ibrahim S.S.; El Kammar A.M.; Guda A.M.

    2015-01-01

    This work aimed for pyrite separation from Abu Tartur black shale as a source of sulfur to be an added economic value of Abu Tartur area. The considered samples in the present work were collected from a core drilled in Abu Tartur plateau representing the pyrite-rich black shale of the U. Cretaceous age. Sample characterization was carried out using petrographic microscope, XRD, DTA/DTG, C/S and XRF techniques. Clay minerals, silt-sized quartz, calcite, and hematite were the main minerals associating pyr-ite (5.34%). Liberation behavior of the sample was about 80%below 5 lm. Sample processing was achieved through one-day soaking followed by classification using 1 inch Mozley hydro-cyclone where about 35.5% by weight went to underflow and 64.5% went to overflow. The underflow product was subjected to an advanced gravity separation process using SB-40 Falcon Concentrator through a CCD statistical design prepared by Design-Expert 6.0 software proposed to opti-mize the separation process through a study for the effects of frequency (Hz) and water pressure (Psi) on both assay and recovery of the sulfur-rich heavy fraction. A heavy concentrate weighed 10.90%with inorganic sulfur content reached 11.37%(21.24%pyrite) with overall recovery (50.01%) was obtained after two cleaning at the optimum conditions.

  13. Investigation of pyrite surface state by DFT and AFM

    Institute of Scientific and Technical Information of China (English)

    先永骏; 聂琪; 文书明; 刘建; 邓久帅

    2015-01-01

    The surface states of pyrite (FeS2) were theoretically investigated using first principle calculation based on the density functional theory (DFT). The results indicate that both the (200) and (311) surfaces of pyrite undergo significant surface atom relaxation after geometry optimization, which results in a considerable distortion of the surface region. In the normal direction, i.e., perpendicular to the surface, S atoms in the first surface layer move outward from the bulk, while Fe atoms move toward the bulk, forming an S-rich surface. The surface relaxation processes are driven by electrostatic interaction, which is evidenced by a relative decrease in the surface energy after surface relaxation. Such a relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. Atomic force microscopy (AFM) analysis reveals that only sulfur atom is visible on the pyrite surface. This result is consistent with the DFT data. Such S-rich surface has important influence on the flotation properties of pyrite.

  14. The mechanisms of pyrite oxidation and leaching: A fundamental perspective

    Science.gov (United States)

    Chandra, A. P.; Gerson, A. R.

    2010-09-01

    Pyrite is the earth's most abundant sulfide mineral. Its frequent undesirable association with minerals of economic value such as sphalerite, chalcopyrite and galena, and precious metals such as gold necessitates costly separation processes such as leaching and flotation. Additionally pyrite oxidation is a major contributor to the environmental problem of acid rock drainage. The surface oxidation reactions of pyrite are therefore important both economically and environmentally. Significant variations in electrical properties resulting from lattice substitution of minor and trace elements into the lattice structure exist between pyrite from different geographical locations. Furthermore the presence of low coordination surface sites as a result of conchoidal fracture causes a reduction in the band gap at the surface compared to the bulk thus adding further electrochemical variability. Given the now general acceptance after decades of research that electrochemistry dominates the oxidation process, the geographical location, elemental composition and semi-conductor type (n or p) of pyrite are important considerations. Aqueous pyrite oxidation results in the production of sulfate and ferrous iron. However other products such as elemental sulfur, polysulfides, hydrogen sulfide, ferric hydroxide, iron oxide and iron(III) oxyhydroxide may also form. Intermediate species such as thiosulfate, sulfite and polythionates are also proposed to occur. Oxidation and leach rates are generally influenced by solution Eh, pH, oxidant type and concentration, hydrodynamics, grain size and surface area in relation to solution volume, temperature and pressure. Of these, solution Eh is most critical as expected for an electrochemically controlled process, and directly correlates with surface area normalised rates. Studies using mixed mineral systems further indicate the importance of electrochemical processes during the oxidation process. Spatially resolved surface characterisation of fresh

  15. Pyrite sulfur isotopes reveal glacial-interglacial environmental changes

    Science.gov (United States)

    Pasquier, Virgil; Sansjofre, Pierre; Rabineau, Marina; Revillon, Sidonie; Houghton, Jennifer; Fike, David A.

    2017-06-01

    The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes to the Earth’s surface environment, including the rise of atmospheric oxygen. Such inferences assume that individual δ34S records reflect temporal changes in the global sulfur cycle; this assumption may be well grounded for sulfate-bearing minerals but is less well established for pyrite-based records. Here, we investigate alternative controls on the sedimentary sulfur isotopic composition of marine pyrite by examining a 300-m drill core of Mediterranean sediments deposited over the past 500,000 y and spanning the last five glacial-interglacial periods. Because this interval is far shorter than the residence time of marine sulfate, any change in the sulfur isotopic record preserved in pyrite (δ34Spyr) necessarily corresponds to local environmental changes. The stratigraphic variations (>76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial-interglacial sea level and temperature changes. In this case, the dominant control appears to be glacial-interglacial variations in sedimentation rates. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records, especially associated with intervals of substantial sea level change. This work provides an important perspective on the origin of variability in such records and suggests meaningful paleoenvironmental information can be derived from pyrite δ34S records.

  16. Bio-leaching effects of Leptospirillum ferriphilum on the surface chemical properties of pyrite

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Leptospirillum ferriphilum cultured using different energy sources(either soluble ferrous ion or pyrite) changed the surface properties of pyrite.Cell adsorption,zeta-potential,hydrophobicty,FT-IR spectra and surface morphology were investigated.Adhesion of bacterial cells to the pyrite surface is a fast process.Furthermore,the adsorption of cells grown in pyrite is greater than of cells grown in soluble ferrous ion.The Iso-Electric Point(IEP) of pyrite treated with L.ferriphilum approaches that of the cell...

  17. Surface electrochemical control for fine coal and pyrite separation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, M.E.; Bodily, D.M.; Hu, Weibai; Chen, Wanxiong; Huang, Qinping; Liang, Jun; Riley, A.M.; Li, Jun; Wann, Jyi-Perng; Zhong, Tingke; Zhu, Ximeng

    1993-01-20

    Laboratory flotation tests were carried out on three coals and on coal pyrite. Floatability measurements included natural floatability, flotation with a xanthate collector and salt flotation. The ranking of the floatability of the three coals were: Upper Freeport > Pittsburgh > Illinois. The floatability of mineral pyrite and coal pyrite increased markedly with xanthate concentration, but decreased with increased pH. In general, coal pyrite was more difficult to float than mineral pyrite. This was attributed to the presence of surface carbonaceous and mineral matter, since floatability of coal pyrite improved by acid pretreatment. Flotation tests demonstrated that the floatability of coal and mineral pyrite was greatly enhanced by the presence of an electrolyte. Flotation was also enhanced by the addition of modifiers such as CuSO{sub 4}, Na{sub 2}S, CO{sub 2} and EDTA. Lime additions markedly reduced the floatability of coal pyrite. Enhanced floatability of coal pyrite resulted when the pyrite was anodically oxidized in a specially constructed electrochemical flotation cell Pretreatment in potential ranges previously observed for polysulfide and sulfur film formation resulted in the enhanced floatability. While interesting trends and influences, both chemical and electrochemical, markedly improved the floatability of coal, there is little hope for reverse flotation as an effective technology for coal/coal-pyrite separations. The effects of poor liberation and entrainment appear overriding.

  18. Trace metal pyritization variability in response to mangrove soil aerobic and anaerobic oxidation processes.

    Science.gov (United States)

    Machado, W; Borrelli, N L; Ferreira, T O; Marques, A G B; Osterrieth, M; Guizan, C

    2014-02-15

    The degree of iron pyritization (DOP) and degree of trace metal pyritization (DTMP) were evaluated in mangrove soil profiles from an estuarine area located in Rio de Janeiro (SE Brazil). The soil pH was negatively correlated with redox potential (Eh) and positively correlated with DOP and DTMP of some elements (Mn, Cu and Pb), suggesting that pyrite oxidation generated acidity and can affect the importance of pyrite as a trace metal-binding phase, mainly in response to spatial variability in tidal flooding. Besides these aerobic oxidation effects, results from a sequential extraction analyses of reactive phases evidenced that Mn oxidized phase consumption in reaction with pyrite can be also important to determine the pyritization of trace elements. Cumulative effects of these aerobic and anaerobic oxidation processes were evidenced as factors affecting the capacity of mangrove soils to act as a sink for trace metals through pyritization processes.

  19. Comparative Mössbauer study of the oxidation of pyrite under different conditions

    Science.gov (United States)

    Gracia, M.; Gancedo, J. R.; Martínez-Alonso, A.; Tascón, J. M. D.

    1990-07-01

    Samples of pyrite-rich brown coal from As Pontes and Meirama coalfields (Spain) were oxidized either by air at atmospheric pressure or by a cool oxygen plasma generated by radiofrequency activation. Despite the very different nature and characteristics of the oxidizing media, in both cases the RT Mössbauer spectra were easily fitted to two doublets, whose parameters matched those of pyrite and jarosite (hydrated iron (III) sulphate). The extent of pyrite oxidation to jarosite was monitored by the relative spectral areas of pyrite and jarosite doublets. Both, air and plasma, oxidized pyrite to the same extent and in a similar way, in contrast to coal organic matter, which was scarcely modified by air but completely oxidized by the plasma at the same temperature (ca. 423 K). The incomplete oxidation of pyrite by plasma is attributed to the action of a thin calcium sulphate layer which hinders the access of activated oxygen to small pyrite crystals.

  20. Comparative Moessbauer study of the oxidation of pyrite under different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Gracia, M.; Gancedo, J.R.; Martinez-Alonso, A.; Tascon, J.M.D. (Instituto de Quimica Fisica ' Rocasolano' , Madrid (Spain))

    1990-07-01

    Samples of pyrite-rich brown coal from As Pontes and Meirama coalfields (Spain) were oxidized either by air at atmospheric pressure or by a cool oxygen plasma generated by radiofrequency activation. Despite the very different nature and characteristics of the oxidizing media, in both cases the RT Moessbauer spectra were easily fitted to two doublets, whose parameters matched those of pyrite and jarosite (hydrated iron (III) sulphate). The extent of pyrite oxidation to jarosite was monitored by the relative spectral areas of pyrite and jarosite doublets. Both, air and plasma, oxidized pyrite to the same extent and in a similar way, in contrast to coal organic matter, which was scarcely modified by air but completely oxidized by the plasma at the same temperature (ca. 423 K). The incomplete oxidation of pyrite by plasma is attributed to the action of a thin calcium sulphate layer which hinders the access of activated oxygen to small pyrite crystals. 18 refs., 3 tabs., 2 figs.

  1. Source of arsenic-bearing pyrite in southwestern Vermont, USA: Sulfur isotope evidence

    Energy Technology Data Exchange (ETDEWEB)

    Mango, Helen, E-mail: helen.mango@castleton.edu [Department of Natural Sciences, Castleton State College, 233 South Street, Castleton, VT 05735 (United States); Ryan, Peter, E-mail: pryan@middlebury.edu [Department of Geology, Middlebury College, 276 Bicentennial Way, Middlebury, VT 05753 (United States)

    2015-02-01

    Arsenic-bearing pyrite is the source of arsenic in groundwater produced in late Cambrian and Ordovician gray and black slates and phyllites in the Taconic region of southwestern Vermont, USA. The aim of this study is to analyze the sulfur isotopic composition of this pyrite and determine if a relationship exists between pyrite δ{sup 34}S and arsenic content. Pyrite occurs in both sedimentary/diagenetic (bedding-parallel layers and framboids) and low-grade metamorphic (porphyroblast) forms, and contains up to > 2000 ppm As. The sulfur isotopic composition of arsenic-bearing pyrite ranges from − 5.2‰ to 63‰. In the marine environment, the sulfur in sedimentary pyrite becomes increasingly enriched in {sup 34}S as the geochemical environment becomes increasingly anoxic. There is a positive correlation between δ{sup 34}S and arsenic content in the Taconic pyrite, suggesting that uptake of arsenic by pyrite increased as the environment became more reducing. This increased anoxia may have been due to a rise in sea level and/or tectonic activity during the late Cambrian and Ordovician. Low-grade metamorphism appears to have little effect on sulfur isotope composition, but does correlate with lower arsenic content in pyrite. New groundwater wells drilled in this region should therefore avoid gray and black slates and phyllites that contain sedimentary/diagenetic pyrite with heavy δ{sup 34}S values. - Highlights: • Pyrite is the source of arsenic in groundwater in the Taconic region of Vermont, USA. • As-bearing pyrite δ{sup 34}S = – 5.2 to 63‰ with higher {sup 34}S as environment becomes more anoxic. • High sea level, tectonic activity create anoxia, with incorporation of As into pyrite. • New wells should avoid slate/phyllite containing sedimentary pyrite with heavy δ{sup 34}S.

  2. A proposed new type of arsenian pyrite: Composition, nanostructure and geological significance

    Science.gov (United States)

    Deditius, Artur P.; Utsunomiya, Satoshi; Renock, Devon; Ewing, Rodney C.; Ramana, Chintalapalle V.; Becker, Udo; Kesler, Stephen E.

    2008-06-01

    This report describes a new form of arsenian pyrite, called As3+-pyrite, in which As substitutes for Fe [(Fe,As)S2], in contrast to the more common form of arsenian pyrite, As1--pyrite, in which As1- substitutes for S [Fe(As,S)2]. As3+-pyrite has been observed as colloformic overgrowths on As-free pyrite in a hydrothermal gold deposit at Yanacocha, Peru. XPS analyses of the As3+-pyrite confirm that As is present largely as As3+. EMPA analyses show that As3+-pyrite incorporates up to 3.05 at % of As and 0.53 at. %, 0.1 at. %, 0.27 at. %, 0.22 at. %, 0.08 at. % and 0.04 at. % of Pb, Au, Cu, Zn, Ni, and Co, respectively. Incorporation of As3+ in the pyrite could be written like: As+yAu+1-y(□)⇔2Fe; where Au+ and vacancy (□) help to maintain the excess charge. HRTEM observations reveal a sharp boundary between As-free pyrite and the first overgrowth of As3+-pyrite (20-40 nm thick) and co-linear lattice fringes indicating epitaxial growth of As3+-pyrite on As-free pyrite. Overgrowths of As3+-pyrite onto As-free pyrite can be divided into three groups on the basis of crystal size, 8-20 nm, 100-300 nm and 400-900 nm, and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals. The Yanacocha deposit, in which As3+-pyrite was found, formed under relatively oxidizing conditions in which the dominant form of dissolved As in the stability field of pyrite is As3+; in contrast, reducing conditions are typical of most environments that host As1--pyrite. As3+-pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments, including high-sulfidation epithermal deposits and shallow groundwater systems, where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of As3+ and toxic heavy metals in oxidizing natural systems.

  3. Pyrite surface characterization and control for advanced fine coal desulfurization technologies. First annual report, September 1, 1990--August 30, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang-Huai

    1991-12-31

    The objective of this project is to conduct extensive studies on the surface reactivity of pyrite by using electrochemical, surface analysis, potentiometric and calorimetric titration, and surface hydrophobicity characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The products as well as their structure, the mechanisms and the kinetics of the oxidation of coal-pyrite surfaces and their interaction with various chemical reagents will be systematically studied and compared with that of mineral-pyrite and synthetic pyrite to determine the correlation between the surface reactivity of pyrite and the bulk chemical properties of pyrite and impurities. The surface chemical studies and the studies of floatability of coal-pyrite and the effect of various parameters such as grinding media and environment, aging under different atmospheres, etc. on thereof, are directed at identifying the causes and possible solutions of the pyrite rejection problems in coal cleaning.

  4. Protein footprinting by pyrite shrink-wrap laminate.

    Science.gov (United States)

    Leser, Micheal; Pegan, Jonathan; El Makkaoui, Mohammed; Schlatterer, Joerg C; Khine, Michelle; Law, Matt; Brenowitz, Michael

    2015-04-07

    The structure of macromolecules and their complexes dictate their biological function. In "footprinting", the solvent accessibility of the residues that constitute proteins, DNA and RNA can be determined from their reactivity to an exogenous reagent such as the hydroxyl radical (·OH). While ·OH generation for protein footprinting is achieved by radiolysis, photolysis and electrochemistry, we present a simpler solution. A thin film of pyrite (cubic FeS2) nanocrystals deposited onto a shape memory polymer (commodity shrink-wrap film) generates sufficient ·OH via Fenton chemistry for oxidative footprinting analysis of proteins. We demonstrate that varying either time or H2O2 concentration yields the required ·OH dose-oxidation response relationship. A simple and scalable sample handling protocol is enabled by thermoforming the "pyrite shrink-wrap laminate" into a standard microtiter plate format. The low cost and malleability of the laminate facilitates its integration into high throughput screening and microfluidic devices.

  5. Heterocoagulation of chalcopyrite and pyrite minerals in flotation separation.

    Science.gov (United States)

    Mitchell, Timothy K; Nguyen, Anh V; Evans, Geoffrey M

    2005-06-30

    Heterocoagulation between various fine mineral particles contained within a mineral suspension with different structural and surface chemistry can interfere with the ability of the flotation processes to selectively separate the minerals involved. This paper examines the interactions between chalcopyrite (a copper mineral) and pyrite (an iron mineral often bearing gold) as they approach each other in suspensions with added chemicals, and relates the results to the experimental data for the flotation recovery and selectivity. The heterocoagulation was experimentally studied using the electrophoretic light scattering (ELS) technique and was modelled by incorporating colloidal forces, including the van der Waals, electrostatic double layer and hydrophobic forces. The ELS results indicated that pyrite has a positive zeta potential (zeta) up to its isoelectric point (IEP) at approximately pH 2.2, while chalcopyrite has a positive zeta up to its IEP at approximately pH 5.5. This produces heterocoagulation of chalcopyrite with pyrite between pH 2.2 and pH 5.5. The heterocoagulation was confirmed by the ELS spectra measured with a ZetaPlus instrument from Brookhaven and by small-scale flotation experiments.

  6. Effect of processing history of pyrite on its leaching kinetics

    Institute of Scientific and Technical Information of China (English)

    赵中伟; 李洪桂; 孙培梅; 李运姣; 霍广生

    2003-01-01

    Different researchers often attained scattered kinetic results for the same leaching process. Usually, the difference is ascribed to the variation in mineral resource, chemical composition and, accuracy of experimental methods, while less attention is paid to the sample processing history. The present study shows that processing history of pyrite sample can cause great changes in its physico-chemical properties. Crushing, grinding and milling lead to an increase of the leachability of pyrite and the leaching becomes less temperature dependence owing to the decreasing of apparent activation energy of the reaction. The activation energy for its leaching in H2SO4-HNO3 solution is depressed from 73.9 to 47.5kJ/mol after being activated through vibrating milling for 40min. On the contrary, aging causes the reverse change owing to the release of extra inner energy stored during mechanical treatments. Thus activity of pyrite will decrease towards its original value. Surely the processing history of concentrate sample should be taken into consideration when studying the kinetics of leaching reaction.

  7. Source of arsenic-bearing pyrite in southwestern Vermont, USA: sulfur isotope evidence.

    Science.gov (United States)

    Mango, Helen; Ryan, Peter

    2015-02-01

    Arsenic-bearing pyrite is the source of arsenic in groundwater produced in late Cambrian and Ordovician gray and black slates and phyllites in the Taconic region of southwestern Vermont, USA. The aim of this study is to analyze the sulfur isotopic composition of this pyrite and determine if a relationship exists between pyrite δ(34)S and arsenic content. Pyrite occurs in both sedimentary/diagenetic (bedding-parallel layers and framboids) and low-grade metamorphic (porphyroblast) forms, and contains up to >2000 ppm As. The sulfur isotopic composition of arsenic-bearing pyrite ranges from -5.2‰ to 63‰. In the marine environment, the sulfur in sedimentary pyrite becomes increasingly enriched in (34)S as the geochemical environment becomes increasingly anoxic. There is a positive correlation between δ(34)S and arsenic content in the Taconic pyrite, suggesting that uptake of arsenic by pyrite increased as the environment became more reducing. This increased anoxia may have been due to a rise in sea level and/or tectonic activity during the late Cambrian and Ordovician. Low-grade metamorphism appears to have little effect on sulfur isotope composition, but does correlate with lower arsenic content in pyrite. New groundwater wells drilled in this region should therefore avoid gray and black slates and phyllites that contain sedimentary/diagenetic pyrite with heavy δ(34)S values.

  8. Interfacial electrokinetic characteristics before and after bioleaching microorganism adhesion to pyrite

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-she; WANG Zhao-hui; CHEN Hong; ZHANG Yan-hua

    2006-01-01

    Zeta potentials of pyrite and Acidithiobacillusferrooxidans cultured by sulfur in different levels of ionic strength and pH values were measured by Coulter Delsa 440SX zeta potential determinator. Meanwhile, the effects of bacterial adhesion and bacterial concentration on zeta potential of pyrite after adsorption were investigated. The results show that with the increase of ionic strength,zeta potentials of pyrite decrease in the range of pH 2.5-10.5 and the isoelectric point(IEP) of mineral shifts to the left. It is also found that the specific adsorption on pyrite of chloride ion can affect zeta potentials of pyrite sharply. As bacterial adsorption occurs,IEP of pyrite shifts towards that of Acidithiobacillus ferrooxidans; as bacterial concentration is increscent, this tendency is even larger and more obvious. Finally, a reasonable explanation for above-mentioned experimental phenomena was given by electrical double layer model and surface ionization model.

  9. Speciation of arsenic in pyrite by micro-X-ray absorption fine- structure spectroscopy (XAFS)

    Energy Technology Data Exchange (ETDEWEB)

    Paktunc, D. (CCM)

    2008-09-30

    Pyrite (FeS2) often contains variable levels of arsenic, regardless of the environment of formation. Arsenian pyrite has been reported in coals, sediments and ore deposits. Arsenian pyrite having As concentrations of up to 10 wt % in sedimentary rocks (Kolker et al. 1997), about 10 wt% in gold deposits (Fleet et al. 1993), 12 wt % in a refractory gold ore (Paktunc et al. 2006) and 20 wt % in a Carlin-type gold deposit in Nevada (Reich et al. 2005) have been reported. Arsenian pyrite is the carrier of gold in hydrothermal Carlin-type gold deposits, and gold concentrations of up to 0.9 wt % have been reported (Reich et al. 2005; Paktunc et al. 2006). In general, high Au concentrations correlate with As-rich zones in pyrite (Paktunc et al. 2006). Pyrite often ends up in mining and metallurgical wastes as an unwanted mineral and consititutes one of the primary sources of As in the wastes. Arsenic can be readily released to the environment due to rapid oxidative dissolution of host pyrite under atmospheric conditions. Pyrite is also the primary source of arsenic in emissions and dust resulting from combustion of bituminous coals. Despite the importance of arsenian pyrite as a primary source of anthropogenic arsenic in the environment and its economic significance as the primary carrier of gold in Carlin-type gold deposits, our understanding of the nature of arsenic in pyrite is limited. There are few papers dealing with the mode of occurrence of arsenic by bulk XAFS in a limited number of pyrite-bearing samples. The present study documents the analysis of pyrite particles displaying different morphologies and a range of arsenic and gold concentrations to determine the nature and speciation of arsenic.

  10. Pyritization of the Coastal Sediments in the Kelantan Plains in the Malay Peninsula during the Holocene

    Directory of Open Access Journals (Sweden)

    M. S.K. Enio

    2011-01-01

    Full Text Available Problem statement: For a number of geological reasons a proportion of the present coastal plains in the Malay Peninsula were inundated by seawater in the past when pyrite in some of the soils is believed to have been mineralized. Random survey of these sites showed a unique distribution and depth of pyritic layer in the soils along the coastal plains. A study was conducted in order to explain the mechanism of pyritization in the sediments of the present day coastal plains in Kelantan, Peninsular Malaysia. Approach: Soil surveys were conducted and soils were sampled and analyzed. Spatial distribution of the pyritic soils was used to construct an imaginary line to indicate the probable position of the shoreline when the sea level was at its highest. Results: Results of the study showed that soils containing pyrite occur sporadically in the plains. This pyrite occurs in the soils at varying depth; some soils have pyritic layer below 2 m from the surface (northern region, while others have pyrite in the surface horizon (southern region. Pyrite was formed by the reaction of ferrous and sulfide ions which were respectively reduced from ferric ions (sediments and sulfate (seawater ions, respectively. In the middle of the study area, pyritic layer overlain by peaty materials were observed. Conclusion: The presence of pyrite in the soils can be used as an evidence for sea level rise in the area during the Holocene. This pyrite is assumed to have been formed about 6,000 years BP when the sea level rose 3-5 m above the present. Its oxidation has caused untold damage to the productivity of the paddy soils in the area.

  11. Iron Phosphate Coating:A Novel Approach to Controlling Pyrite Oxidation

    Institute of Scientific and Technical Information of China (English)

    HUANGXIAO; V.P.EVANGELOU

    1997-01-01

    A novel coating technique was develped for controlling pyrite oxidation .The technique involved leaching pyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide.During the leaching rpocess,the iron released from pyrite by hydrogen proxide was precipitated by phosphate as a ferric phosphate coating .This coating was shown to be able to effectively prevent pyirte from oxidation and it could be established at the expense of only surface portions of pyrite.The emergence of this technique could provide a unique potential route for abating acid mine draingage and reclaiming sulfide-containing degraded mining land.

  12. Paleoredoc and pyritization of soft-bodied fossils in the Ordovician Frankfort Shale of New York

    DEFF Research Database (Denmark)

    Farrell, Una C.; Briggs, Derek E. G.; Hammarlund, Emma U.

    2013-01-01

    Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization by inves......Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization...

  13. Spectroscopic study of cystine adsorption on pyrite surface: From vacuum to solution conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Arenillas, M.; Mateo-Marti, E., E-mail: mateome@cab.inta-csic.es

    2015-09-08

    Highlights: • Successful adsorption of cystine on pyrite surface under several conditions. • Detailed XPS spectroscopic characterization of cystine adsorption on pyrite surface. • Spectroscopy evidence, oxidation and anoxic conditions adjust molecular adsorption. • Molecular chemistry on pyrite is driven depending on the surrounding conditions. • The cystine/pyrite(100) model is in good agreement with Wächtershäuser’s theory. - Abstract: We characterized the adsorption of cystine molecules on pyrite surface via X-ray photoelectron spectroscopy. Anoxic conditions were simulated under ultra-high-vacuum conditions. In contrast, to simulate oxidation conditions, the molecules were adsorbed on pyrite surface from solution. A novel comparative analysis revealed remarkable differences with respect to molecular adsorption and surface chemistry induced by environmental conditions. Molecular adsorption under anoxic conditions was observed to be more favorable, concentrating a large number of molecules on the surface and two different chemical species. In contrast, the presence of oxygen induced an autocatalytic oxidation process on the pyrite surface, which facilitated water binding on pyrite surface and partially blocked molecular adsorption. Pyrite is a highly reactive surface and contains two crucial types of surface functional groups that drive molecular chemistry on the surface depending on the surrounding conditions. Therefore, the system explored in this study holds interesting implications for supporting catalyzed prebiotic chemistry reactions.

  14. Hot-Water Deposition of Pyritic Stromatolite and Its Relation to Biomineralization

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Pyritic stromatolite, a rich pyrite ore, is scattered as reef masses in sedex deposits of the Proterozoic Yanshan rift trough. The pyritic stromatolite consists of a core and alternating concentric rims of light colloidal pyrite and dark organic materials. The concentric rims are cemented together by trichomes highly similar to the trichomic microorganisms inhabiting substantively around the black chimneys on the current sea beds while the core is composed chiefly of groups of thermophilous sulphur bacteria. Biomarkers for the molecules of pyritic stromatolite include pristane, phytane, regular isoprenoids paraffin, methyl-heptadecyl, and so on. This study reveals the existence of methane-yielding bacteria in the pyritic stromatolite and reflects the evolution of thermophilous thallophyta.Long pulsation of mineralizing thermal solutions venting up along contemporaneous faults in rift troughs contributed greatly not just to the reproduction of thermophilous organisms living around the vents, but to their adsorption of Fe2+ from the solutions in a reducing environment. Pyritic stromatolite constantly took shape through metabolism and reduction of these organisms. Owing to the uneven development of the organic communities close to the vents or the hydrothermal plumes, pyritic stromatolite occurred eventually as scattered reef masses. This mineralizing mechanism may be summarized as the following procedure: flowing of hydrothermal fluids associated with submarine exhalation(r) adsorption and metabolism of thermophilous micro-organisms(r) reduction of organic materials(r) formation of deposits of pyritic stromatolite.

  15. Study of initial stage of mechanochemical transformation in pyrite

    Directory of Open Access Journals (Sweden)

    Paneva D.

    2007-01-01

    Full Text Available The initial stage of transformation of pyrite to Fe(II-sulfate as a result of mechanical milling is studied by X-ray powder diffraction (XRD, Moessbauer spectroscopy (MS, Infrared (IR and X-ray photoelectron spectroscopy (XPS techniques. A degree of conversion of 0.071 is achieved in the time interval of 0 36 min. The kinetic data satisfy the equation of a shrinking core reaction 1-(1-α1/3=kt. The reaction is of the first order. The calculated rate constant is k=6.434.10-4 min-1. .

  16. Molecular Ink Processed Iron Pyrite Thin Films for Photovoltaics

    OpenAIRE

    Weber, Amanda Sue

    2015-01-01

    Thin-film photovoltaics (PV) have the potential to supply our future energy needs, but the dominant commercial thin film technologies rely on rare or toxic elements that may limit their capacity to scale to the terawatt levels of electricity generation needed to impact global energy demand. Iron pyrite (FeS2) is a promising, earth-abundant material that has a suitable band gap of 0.95 eV, a large optical absorption coefficient, and adequate carrier diffusion lengths for use in PV. Unfortunate...

  17. Manipulation of pyrite colonization and leaching by iron-oxidizing Acidithiobacillus species.

    Science.gov (United States)

    Bellenberg, Sören; Barthen, Robert; Boretska, Mariia; Zhang, Ruiyong; Sand, Wolfgang; Vera, Mario

    2015-02-01

    In this study, the process of pyrite colonization and leaching by three iron-oxidizing Acidithiobacillus species was investigated by fluorescence microscopy, bacterial attachment, and leaching assays. Within the first 4-5 days, only the biofilm subpopulation was responsible for pyrite dissolution. Pyrite-grown cells, in contrast to iron-grown cells, were able to oxidize iron(II) ions or pyrite after 24 h iron starvation and incubation with 1 mM H₂O₂, indicating that these cells were adapted to the presence of enhanced levels of reactive oxygen species (ROS), which are generated on metal sulfide surfaces. Acidithiobacillus ferrivorans SS3 and Acidithiobacillus ferrooxidans R1 showed enhanced pyrite colonization and biofilm formation compared to A. ferrooxidans (T). A broad range of factors influencing the biofilm formation on pyrite were also identified, some of them were strain-specific. Cultivation at non-optimum growth temperatures or increased ionic strength led to a decreased colonization of pyrite. The presence of iron(III) ions increased pyrite colonization, especially when pyrite-grown cells were used, while the addition of 20 mM copper(II) ions resulted in reduced biofilm formation on pyrite. This observation correlated with a different extracellular polymeric substance (EPS) composition of copper-exposed cells. Interestingly, the addition of 1 mM sodium glucuronate in combination with iron(III) ions led to a 5-fold and 7-fold increased cell attachment after 1 and 8 days of incubation, respectively, in A. ferrooxidans (T). In addition, sodium glucuronate addition enhanced pyrite dissolution by 25%.

  18. Microbial acceleration of aerobic pyrite oxidation at circumneutral pH.

    Science.gov (United States)

    Percak-Dennett, E; He, S; Converse, B; Konishi, H; Xu, H; Corcoran, A; Noguera, D; Chan, C; Bhattacharyya, A; Borch, T; Boyd, E; Roden, E E

    2017-09-01

    Pyrite (FeS2 ) is the most abundant sulfide mineral on Earth and represents a significant reservoir of reduced iron and sulfur both today and in the geologic past. In modern environments, oxidative transformations of pyrite and other metal sulfides play a key role in terrestrial element partitioning with broad impacts to contaminant mobility and the formation of acid mine drainage systems. Although the role of aerobic micro-organisms in pyrite oxidation under acidic-pH conditions is well known, to date there is very little known about the capacity for aerobic micro-organisms to oxidize pyrite at circumneutral pH. Here, we describe two enrichment cultures, obtained from pyrite-bearing subsurface sediments, that were capable of sustained cell growth linked to pyrite oxidation and sulfate generation at neutral pH. The cultures were dominated by two Rhizobiales species (Bradyrhizobium sp. and Mesorhizobium sp.) and a Ralstonia species. Shotgun metagenomic sequencing and genome reconstruction indicated the presence of Fe and S oxidation pathways in these organisms, and the presence of a complete Calvin-Benson-Bassham CO2 fixation system in the Bradyrhizobium sp. Oxidation of pyrite resulted in thin (30-50 nm) coatings of amorphous Fe(III) oxide on the pyrite surface, with no other secondary Fe or S phases detected by electron microscopy or X-ray absorption spectroscopy. Rates of microbial pyrite oxidation were approximately one order of magnitude higher than abiotic rates. These results demonstrate the ability of aerobic microbial activity to accelerate pyrite oxidation and expand the potential contribution of micro-organisms to continental sulfide mineral weathering around the time of the Great Oxidation Event to include neutral-pH environments. In addition, our findings have direct implications for the geochemistry of modern sedimentary environments, including stimulation of the early stages of acid mine drainage formation and mobilization of pyrite-associated metals

  19. Leaching of pyrite by acidophilic heterotrophic iron-oxidizing bacteria in pure and mixed cultures

    Energy Technology Data Exchange (ETDEWEB)

    Bacelar-Nicolau, P.; Johnson, D.B. [Univ. of Wales, Bangor (United Kingdom). School of Biological Sciences

    1999-02-01

    Seven strains of heterotrophic iron-oxidizing acidophilic bacteria were examined to determine their abilities to promote oxidative dissolution of pyrite (FeS{sub 2}) when they were grown in pure cultures and in mixed cultures with sulfur-oxidizing Thiobacillus spp. Only one of the isolates (strain T-24) oxidized pyrite when it was grown in pyrite-basal salts medium. However, when pyrite-containing cultures were supplemented with 0.02% (wt/vol) yeast extract, most of the isolates oxidized pyrite, and one (strain T-24) promoted rates of mineral dissolution similar to the rates observed with the iron-oxidizing autotroph Thiobacillus ferroxidans. Pyrite oxidation by another isolate (strain T-21) occurred in cultures containing between 0.005 and 0.05% (wt/vol) yeast extract but was completely inhibited in cultures containing 0.5% yeast extract. Ferrous iron was also needed for mineral dissolution by the iron-oxidizing heterotrophs, indicating that these organisms oxidize pyrite via the indirect mechanism. Mixed cultures of three isolates (strains T-21, T-232, and T-24) and the sulfur-oxidizing autotroph Thiobacillus thiooxidans promoted pyrite dissolution; since neither strains T-21 and T-23 nor T. thiooxidans could oxidize this mineral in yeast extract-free media, this was a novel example of bacterial synergism. Mixed cultures of strains T-21 and T-23 and the sulfur-oxidizing mixotroph Thiobacillus acidophilus also oxidized pyrite but to a lesser extent than did mixed cultures containing T. thiooxidans. Pyrite leaching by strain T -23 grown in an organic compound-rich medium and incubated either shaken or unshaken was also assessed. The potential environmental significance of iron-oxidizing heterotrophs in accelerating pyrite oxidation is discussed.

  20. Carrier-microencapsulation using Si-catechol complex for suppressing pyrite floatability

    Energy Technology Data Exchange (ETDEWEB)

    Jha, R.K.T.; Satur, J.; Hiroyoshi, N.; Ito, M.; Tsunekawa, M. [Hokkaido University, Hokkaido (Japan). Graduate School of Engineering

    2008-11-15

    Pyrite (FeS{sub 2}) is a common sulfide mineral associated with valuable metal minerals and coal, and it is rejected as a gangue mineral using physical separation techniques such as froth flotation and discharged into tailing pond. In the flotation, pyrite is frequently entrapped in the froth due to its hydrophobic nature. Formation of acid mine drainage due to the air-oxidation of pyrite in the tailing pond is also a serious problem. The authors have proposed carrier-microencapsulation (CME) as a method for suppressing both the floatability and oxidation of pyrite. In this method, pyrite is coated with a thin layer of metal oxide or hydroxide using catechol solution as a carrier combined with metal ions. The layer converts the pyrite surface from hydrophobic to hydrophilic and acts as a protective coating against oxidation. The present study demonstrates the effect of CME using Si-catechol complex to suppress the pyrite floatability: The bubble pick-up experiments showed that attachment of pyrite particles to air bubble is suppressed by the CME treatment at pH 4-10, Si-catechol complex concentration over 0.5 mol m{sup -3} and treatment time within 2 min. The Hallimond tube flotation experiments showed that the pyrite floatability is suppressed by the CME treatment even in the presence of typical flotation collectors such as kerosene and xanthate. SEM-EDX analysis confirmed that Si present on the pyrite surface treated by Si-catechol complex, implying that SiO{sub 2} or SiOH{sub 4} layer formed by the CME treatment convert the pyrite surface hydrophobic to hydrophilic.

  1. Electrochemical Properties for Co-Doped Pyrite with High Conductivity

    Directory of Open Access Journals (Sweden)

    Yongchao Liu

    2015-09-01

    Full Text Available In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS2. The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. Co in the crystal lattice of FeS2 could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS2 batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g−1 with a doping ratio of 7% was significantly higher than that of the original FeS2 (574.6 mAh·g−1 because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS2.

  2. Surfactant-Assisted Hydrothermal Synthesis of Single Phase Pyrite FeS2 Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Wadia, Cyrus; Wu, Yue; Gul, Sheraz; Volkman, Steven; Guo, Jinghua; Alivisatos, Paul

    2009-03-27

    Iron pyrite nanocrystals with high purity have been synthesized through a surfactant-assisted hydrothermal reaction under optimum pH value. These pyrite nanocrystals represent a new group of well-defined nanoscale structures for high-performance photovoltaic solar cells based on non-toxic and earth abundant materials.

  3. Relationship between pyrite Stability and arsenic mobility during aquifer storage and recovery in southwest central Florida.

    Science.gov (United States)

    Jones, Gregg W; Pichler, Thomas

    2007-02-01

    Elevated arsenic concentrations are common in water recovered from aquifer storage and recovery (ASR) systems in west-central Florida that store surface water. Investigations of the Suwannee Limestone of the Upper Floridan aquifer, the storage zone for ASR systems, have shown that arsenic is highest in pyrite in zones of high moldic porosity. Geochemical modeling was employed to examine pyrite stability in limestone during simulated injections of surface water into wells open only to the Suwannee Limestone with known mineralogy and water chemistry. The goal was to determine if aquifer redox conditions could be altered to the degree of pyrite instability. Increasing amounts of injection water were added to native storage-zone water, and resulting reaction paths were plotted on pyrite stability diagrams. Native storage-zone water plotted within the pyrite stability field, indicating that conditions were sufficiently reducing to allow for pyrite stability. Thus, arsenic is immobilized in pyrite, and its groundwater concentration should be low. This was corroborated by analysis of water samples, none of which had arsenic concentrations above 0.036 microg/L. During simulation, however, as injection/native storage-zone water ratios increased, conditions became less reducing and pyrite became unstable. The result would be release of arsenic from limestone into storage-zone water.

  4. Fabrication and characterization of PDLLA/pyrite composite bone scaffold for osteoblast culture

    Indian Academy of Sciences (India)

    Lifang Zhang; Yanyan Zheng; Chengdong Xiong

    2015-06-01

    A series of highly interconnected porous poly(D,L-lactide acid) (PDLLA)/pyrite (Zi-Ran-Tong, FeS2) scaffold containing 5–20% of pyrite was fabricated by particle leaching combined with the thermal-induced phase separation method. Pyrite (FeS2, named as Zi-Ran-Tong in Chinese medicine), as a traditional Chinesemedicine, has been used in the Chinese population to treat bone diseases and to promote bone healing. The mechanical properties of the PDLLA scaffold were significantly enhanced after the addition of pyrite. The osteoblastic ROS17/2.8 cell line was used and seeded on the PDLLA/pyrite scaffold to study its potential to support the growth of osteoblastic cells and to estimate the optimal dose of pyrite for bone tissue engineering. The effects of pyrite on cell proliferation and differentiation were evaluated by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide and alkaline phosphatase activity assay. The cells on the porous composite scaffold formed a continuous layer on the outer and inner surface observed by scanning electron microscopy and fluorescence microscope. The results strongly suggested that the PDLLA/pyrite composite scaffold could stimulate the growth of ROS17/2.8 cells in vitro and it could be potentially used as a scaffold for bone tissue engineering.

  5. Isotopic and microbiological signatures of pyrite-driven denitrification in a sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Slomp, C.P.; Broers, H.P.; Bostick, B.; Passier, H.F.; Böttcher, M.E.; Omoregie, E.O.; Lloyd, J.R.; Polya, D.A.; Van Cappellen, P.

    2012-01-01

    Denitrificationdriven by pyrite oxidation can play a major role in the removal of nitrate from groundwater systems. As yet, limited information is available on the interactions between the micro-organisms and aqueous and mineral phases in aquifers where pyrite oxidation is occurring. In this study,

  6. Intermediary sulfur compounds in pyrite oxidation: implications for bioleaching and biodepyritization of coal

    Energy Technology Data Exchange (ETDEWEB)

    Schippers, A.; Rohwerder, T.; Sand, W. [Hamburg Univ. (Germany). Inst. fuer Allgemeine Botanik und Botanischer Garten

    1999-07-01

    Accumulation of elemental sulfur during pyrite oxidation lowers the efficiency of coal desulfurization and bioleaching. In the case of pyrite bioleaching by Leptospirillum ferrooxidans, an iron(II)-ion-oxidizing organism without sulfur-oxidizing capacity, from the pyritic sulfur moiety about 10% elemental sulfur, 2% pentathionate, and 1% tetrathionate accumulated by a recently described cyclic pyrite oxidation mechanism. In the case of pure cultures of Thiobacillus ferrooxidans and mixed cultures of L. ferrooxidans and T. thiooxidans, pyrite was nearly completely oxidized to sulfate because of the capacity of these cultures to oxidize both iron(II) ions and sulfur compounds. Pyrite oxidation in acidic solutions, mediated chemically by iron(III) ion, resulted in an accumulation of similar amounts of sulfur compounds as obtained with L. ferrooxidans. Changes of pH to values below 2 or in the iron ion concentration are not decisive for diverting the flux of sulfur compounds. The literature on pyrite bioleaching is in agreement with the findings indicating that the chemistry of direct and indirect pyrite leaching is identical. (orig.)

  7. Bio-reduction of pyrite investigated in a gas lift loop reactor

    NARCIS (Netherlands)

    Hol, A.; Weijden, van der R.D.; Weert, van G.; Kondos, P.; Buisman, C.J.N.

    2010-01-01

    To liberate gold from refractory pyrite, oxidative destruction techniques that consume lots of energy and generate acidic waste streams are custom. As an alternative the “bio-reduction” of pyrite is proposed and investigated in this study. Bio-reduction is an anaerobic process based on sulfate/sulfu

  8. Framboidal and idiomorphic pyrite in the upper Maastrichtian sedimentary rocks at Gabal Oweina, Nile Valley, Egypt: Formation processes, oxidation products and genetic implications to the origin of framboidal pyrite

    Science.gov (United States)

    Soliman, Mamdouh F.; El Goresy, Ahmed

    2012-08-01

    The upper Maastrichtian organic-rich sediments studied at Gabal Oweina, Egypt, are moderately enriched in syngenetic and diagenetic pyrite. Pyrite occurs mostly as layers or bands, group of lamina, lenses, diagenetic intercalated pockets, burrow fills and disseminated individual pyrite framboids and crystals within the host sediments. The pyritic thin bands and lamina consist mostly of unconsolidated to compact-oriented pyrite (oriented along the bedding planes) in gypsiferous-clayey matrix and less common as poorly oriented pyrite crystallites. In several cases, pyrite crystals of the latter type depict zoning, fracturing and micro-concretions. Pyritic burrow fills are composed mainly of pyrite, phosphatic ooids, microfossils, glauconitic grains, poorly graphitized carbon and native sulfur. Pyrite replaces minerals other than gypsum, sulfur or carbon. It also replaces microfossils thus turning some of the phosphatic ooids and microfossils to pyritized pseudomorphs. None of the studied phosphate ooids or framboids contains any mackinawite, pyrrhotite or greigite. Based on the microscopic and SEM observations of the micro-textures of disseminated pyrite found at Gabal Oweina section, four morphological forms of primary pyrite could be identified: (1) Grouped multiple-framboids; (2) Individual framboids; (3) Pyrite idiomorphic crystal overgrowths on framboids and (4) Single and aggregates of euhedral pyrite crystals. The multiple-framboid formation may have emerged from three successive processes: nucleation and growth of individual aggregates of the microcrystals to form combined micro-framboids (the growth of framboids); and followed by grouping of the several pyrite framboids. Direct pyrite nucleation (shell formation), crystallization, and aggregation processes might complete a single framboid. The disseminated single and aggregated euhedral pyrite crystals bear evidence indicating that their formation was via nucleation and growth of pyrite crystallites and

  9. The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits

    Science.gov (United States)

    Deditius, Artur P.; Reich, Martin; Kesler, Stephen E.; Utsunomiya, Satoshi; Chryssoulis, Stephen L.; Walshe, John; Ewing, Rodney C.

    2014-09-01

    The ubiquity of Au-bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of Au and As in this sulfide occurs under a wide range of physico-chemical conditions. Despite significant advances in the last 20 years, fundamental factors controlling Au and As ratios in pyrite from ore deposits remain poorly known. Here we explore these constraints using new and previously published EMPA, LA-ICP-MS, SIMS, and μ-PIXE analyses of As and Au in pyrite from Carlin-type Au, epithermal Au, porphyry Cu, Cu-Au, and orogenic Au deposits, volcanogenic massive sulfide (VHMS), Witwatersrand Au, iron oxide copper gold (IOCG), and coal deposits. Pyrite included in the data compilation formed under temperatures from ∼30 to ∼600 °C and in a wide variety of geological environments. The pyrite Au-As data form a wedge-shaped zone in compositional space, and the fact that most data points plot below the solid solubility limit defined by Reich et al. (2005) indicate that Au1+ is the dominant form of Au in arsenian pyrite and that Au-bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native Au. The analytical data also show that the solid solubility limit of Au in arsenian pyrite defined by an Au/As ratio of 0.02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal-chemical properties of pyrite and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility in pyrite is retrograde; Au and As contents decrease as a function of increasing temperature from ∼200 to ∼500 °C. Based on these results, two major Au-As trends for Au-bearing arsenian pyrite from ore deposits are defined. One trend is formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock interactions and/or can be highly perturbed by changes in temperature and

  10. Lipid extraction and esterification for microalgae-based biodiesel production using pyrite (FeS2).

    Science.gov (United States)

    Seo, Yeong Hwan; Sung, Mina; Oh, You-Kwan; Han, Jong-In

    2015-09-01

    In this study, pyrite (FeS2) was used for lipid extraction as well as esterification processes for microalgae-based biodiesel production. An iron-mediated oxidation reaction, Fenton-like reaction, produced an expected degree of lipid extraction, but pyrite was less effective than FeCl3 commercial powder. That low efficiency was improved by using oxidized pyrite, which showed an equivalent lipid extraction efficiency to FeCl3, about 90%, when 20 mM of catalyst was used. Oxidized pyrite was also employed in the esterification step, and converted free fatty acids to fatty acid methyl esters under acidic conditions; thus, the fatal problem of saponification during esterification with alkaline catalysts was avoided, and esterification efficiency over 90% was obtained. This study clearly showed that pyrite could be utilized as a cheap catalyst in the lipid extraction and esterification steps for microalgae-based biodiesel production.

  11. Pyrite surface interaction with selected organic aqueous species under anoxic conditions

    Directory of Open Access Journals (Sweden)

    Bebié Joakim

    2000-10-01

    Full Text Available The interaction between low-molecular weight organic compounds and pyrite under anoxic conditions has been studied using a combination of electrophoresis and batch sorption experiments. The results suggest that acetate, carbamide, ethylamine, formamide, purine, D-ribose, and adenine, as well as the amino acids alanine, cysteine and glycine, interact within the electrophoretic shearplane of the pyrite surface. The observed surface interaction between the negatively charged surface of pyrite and the organic aqueous species takes place regardless of the formal charge of the aqueous species of interest. This indicates that the interaction of organic molecules with pyrite surfaces under anoxic conditions is dictated by interactions with specific surface sites (thiol or iron surface sites rather than electrostatic forces. Dissolved metals typically enhance the interaction of the organics species. This enhancement is either due to an alteration in the distribution of thiol and iron groups on the pyrite surface or by the formation of ternary surface complexes.

  12. Occurrence and Geological Genesis of Pyrites in Late Paleozoic Coals in North China

    Institute of Scientific and Technical Information of China (English)

    刘大锰; 杨起; 等

    2000-01-01

    The occurrence and geological genesis of pyrites in Late Paleozoic colas of North china have been systematically studied in terms of coal petrology,coal chemistry,elemental geochemistry and sulfur isotope geochemistry.The results suggest that eight types of pyrite,i.e.,framboidal,automorphic graular,oolitic,massive,homogeneous spherical,allotriomorphic,nodular,joint-and fisure-filling pyrintes can be subdivided under the microscope,Four generations of pyrite are also reconized according to the shape,size,coexisting assemblage,spacial distribution relationship with macerals,the contents of sulfur and iron.atomic S/Fe ratios and associated elements in pryites.Sulfur in Late Palozoic colas of North China is of diverse source as evidenced by sulfur isotope variations in the pyrites.The δ34S values of pyrite generated at the early stage ted to be negative,and at the late stage,positive.

  13. Spectroscopic study of cystine adsorption on pyrite surface: From vacuum to solution conditions

    Science.gov (United States)

    Sanchez-Arenillas, M.; Mateo-Marti, E.

    2015-09-01

    We characterized the adsorption of cystine molecules on pyrite surface via X-ray photoelectron spectroscopy. Anoxic conditions were simulated under ultra-high-vacuum conditions. In contrast, to simulate oxidation conditions, the molecules were adsorbed on pyrite surface from solution. A novel comparative analysis revealed remarkable differences with respect to molecular adsorption and surface chemistry induced by environmental conditions. Molecular adsorption under anoxic conditions was observed to be more favorable, concentrating a large number of molecules on the surface and two different chemical species. In contrast, the presence of oxygen induced an autocatalytic oxidation process on the pyrite surface, which facilitated water binding on pyrite surface and partially blocked molecular adsorption. Pyrite is a highly reactive surface and contains two crucial types of surface functional groups that drive molecular chemistry on the surface depending on the surrounding conditions. Therefore, the system explored in this study holds interesting implications for supporting catalyzed prebiotic chemistry reactions.

  14. Remnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis

    Science.gov (United States)

    Foley, N.; Ayuso, R.A.; Seal, R.R.

    2001-01-01

    Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that gold mineralization was coeval with deposition of host rocks and not solely related to Paleozoic tectonic events. Ore horizons at the Haile deposit, South Carolina, contain many remnants of early pyrite: (1) fine-grained cubic pyrite disseminated along bedding; (2) fine- grained spongy, rounded masses of pyrite that may envelop or drape over pyrite cubes; (3) fragments of botryoidally and crustiform layered pyrite, and (4) pyritic infilling of vesicles and pumice. Detailed mineral chemistry by petrography, microprobe, SEM, and EDS analysis of replaced pumice and colloform structures containing both arsenic compositional banding and electrum points to coeval deposition of gold and the volcanic host rocks and, thus, confirms a syngenetic origin for the gold deposits. Early pyrite textures are present in other major deposits of the Carolina slate belt, such as Ridgeway and Barite Hill, and these provide strong evidence for models whereby the sulfide ores formed prior to tectonism. The role of Paleozoic metamorphism was to remobilize and concentrate gold and other minerals in structurally prepared sites. Recognizing the significance of paragenetically early pyrite and gold textures can play an important role in distinguishing sulfide ores that form in volcanic and sedimentary environments from those formed solely by metamorphic processes. Exploration strategies applied to the Carolina slate belt and correlative rocks in the eastern United States in the Avalonian basement will benefit from using syngenetic models for gold mineralization.

  15. Control of pyrite surface chemistry in physical coal cleaning. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Luttrell, G.H.; Yoon, R.H.; Richardson, P.E.

    1993-05-19

    In Part I, Surface Chemistry of Coal Pyrite the mechanisms responsible for the inefficient rejection of coal pyrite were investigated using a number of experimental techniques. The test results demonstrate that the hydrophobicity of coal pyrite is related to the surface products formed during oxidation in aqueous solutions. During oxidation, a sulfur-rich surface layer is produced in near neutral pH solutions. This surface layer is composed mainly of sulfur species in the form of an iron-polysulfide along with a smaller amount of iron oxide/hydroxides. The floatability coal pyrite increases dramatically in the presence of frothers and hydrocarbon collectors. These reagents are believed to absorb on the weakly hydrophobic pyrite surfaces as a result of hydrophobic interaction forces. In Part III, Developing the Best Possible Rejection Schemes, a number of pyrite depressants were evaluated in column and conventional flotation tests. These included manganese (Mn) metal, chelating agents quinone and diethylenetriamine (DETA), and several commercially-available organic depressants. Of these, the additives which serve as reducing agents were found to be most effective. Reducing agents were used to prevent pyrite oxidation and/or remove oxidation products present on previously oxidized surfaces. These data show that Mn is a significantly stronger depressant for pyrite than quinone or DETA. Important factors in determining the pyrite depression effect of Mn include the slurry solid content during conditioning, the addition of acid (HCl), and the amount of Mn. The acid helps remove the oxide layer from the surface of Mn and promotes the depression of pyrite by Mn.

  16. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Osseo-Asare, K.; Wei, Dawei

    1996-01-01

    This project seeks to advance the fundamental understanding of the physico-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. Central to this research is the use of synthetic microsize particles of pyrite as model microelectrodes to investigate the semiconductor electrochemistry of pyrite. The research focuses on: (a) the synthesis of microsize particles of pyrite in aqueous solution at room temperature, (b) the formation of iron sulfide complex, the precursor of FeS or FeS{sub 2}, and (c) the relationship between the semiconductor properties of pyrite and its interfacial electrochemical behavior in the dissolution process. In Chapter 2, 3 and 4, a suitable protocol for preparing microsize particles of pyrite in aqueous solution is given, and the essential roles of the precursors elemental sulfur and ``FeS`` in pyrite formation are investigated. In Chapter 5, the formation of iron sulfide complex prior to the precipitation of FeS or FeS{sub 2} is investigated using a fast kinetics technique based on a stopped-flow spectrophotometer. The stoichiometry of the iron sulfide complex is determined, and the rate and formation constants are also evaluated. Chapter 6 provides a summary of the semiconductor properties of pyrite relevant to the present study. In Chapters 7 and 8, the effects of the semiconductor properties on pyrite dissolution are investigated experimentally and the mechanism of pyrite dissolution in acidic aqueous solution is examined. Finally, a summary of the conclusions from this study and suggestions for future research are presented in Chapter 9.

  17. Retention and reduction of uranium on pyrite surface; Retention et reduction de l'uranium a la surface de la pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Eglizaud, N

    2006-12-15

    In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS{sub 2}). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH {>=} 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10{sup -9} mol g{sup -1}, an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. {>=} -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 {+-} 0.8) x 10{sup -7} mol L{sup -1} of uranium(VI). Modelling of uranium sorption at high surface coverage ({>=} 4 x 10{sup -9} mol g{sup -1}) by the Langmuir model yields an adsorption constant of 8 x 10{sup 7} L mol{sup -1}. Finally, a great excess of uranium(VI) above the

  18. Ultrasonic ash/pyrite liberation. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Yungman, B.A.; Buban, K.S.; Stotts, W.F.

    1990-06-01

    The objective of this project was to develop a coal preparation concept which employed ultrasonics to precondition coal prior to conventional or advanced physical beneficiation processes such that ash and pyrite separation were enhanced with improved combustible recovery. Research activities involved a series of experiments that subjected three different test coals, Illinois No. 6, Pittsburgh No. 8, and Upper Freeport, ground to three different size fractions (28 mesh {times} 0, 200 mesh {times} 0, and 325 mesh {times} 0), to a fixed (20 kHz) frequency ultrasonic signal prior to processing by conventional and microbubble flotation. The samples were also processed by conventional and microbubble flotation without ultrasonic pretreatment to establish baseline conditions. Product ash, sulfur and combustible recovery data were determined for both beneficiation processes.

  19. Oxygen adsorption on pyrite (100) surface by density functional theory

    Institute of Scientific and Technical Information of China (English)

    孙伟; 胡岳华; 邱冠周; 覃文庆

    2004-01-01

    Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference.The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

  20. All inorganic iron pyrite nano-heterojunction solar cells

    Science.gov (United States)

    Kirkeminde, Alec; Scott, Randall; Ren, Shenqiang

    2012-11-01

    The large absorption coefficient of iron pyrite (FeS2) nanocrystals coupled with their low-cost and vast-abundance shows great promise as a potential photovoltaic absorber. Here, we demonstrate that bulk heterojunction (BHJ) nanostructures consisting of 80 nm FeS2 nanocubes (NCs) and 4 nm CdS quantum dot (QD) matrix, lead to a well-defined percolation network, which significantly improved open-circuit voltage (Voc) to 0.79 V and power conversion efficiency of 1.1% under AM 1.5 solar illumination. The localized surface plasmon resonances (LSPRs) arising from p-type colloidal FeS2 NCs exhibit plasmonic photoelectron conversion. Our approach can be applied to a wide range of colloidal nanocrystals exhibiting the LSPRs effect and is compatible with solution processing, thereby offering a general tactic to enhancing the efficiency of all inorganic BHJ solar cells and LSPRs-based NIR photodetectors.The large absorption coefficient of iron pyrite (FeS2) nanocrystals coupled with their low-cost and vast-abundance shows great promise as a potential photovoltaic absorber. Here, we demonstrate that bulk heterojunction (BHJ) nanostructures consisting of 80 nm FeS2 nanocubes (NCs) and 4 nm CdS quantum dot (QD) matrix, lead to a well-defined percolation network, which significantly improved open-circuit voltage (Voc) to 0.79 V and power conversion efficiency of 1.1% under AM 1.5 solar illumination. The localized surface plasmon resonances (LSPRs) arising from p-type colloidal FeS2 NCs exhibit plasmonic photoelectron conversion. Our approach can be applied to a wide range of colloidal nanocrystals exhibiting the LSPRs effect and is compatible with solution processing, thereby offering a general tactic to enhancing the efficiency of all inorganic BHJ solar cells and LSPRs-based NIR photodetectors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32097e

  1. Role of hydrogen peroxide and hydroxyl radical in pyrite oxidation by molecular oxygen

    Science.gov (United States)

    Schoonen, Martin A. A.; Harrington, Andrea D.; Laffers, Richard; Strongin, Daniel R.

    2010-09-01

    Hydrogen peroxide and hydroxyl radical are readily formed during the oxidation of pyrite with molecular oxygen over a wide range of pH conditions. However, pretreatment of the pyrite surface influences how much of the intermediates are formed and their fate. Acid-washed pyrite produces significant amounts of hydrogen peroxide and hydroxyl radical when suspended in air-saturated water. However, the hydrogen peroxide concentration shows an exponential decrease with time. Suspensions made with partially oxidized pyrite yield significantly lower amounts of hydrogen peroxide product. The presence of Fe(III)-oxide or Fe(III)-hydroxide patches facilitates the conversion of hydrogen peroxide to oxygen and water. Hence, the degree to which a pyrite surface is covered with patches of Fe(III)-oxide or Fe(III)-hydroxide patches is an important control on the concentration of hydrogen peroxide in solution. Hydrogen peroxide appears to be an important intermediate in the four-electron transfer from pyrite to molecular oxygen. Addition of catalase, an enzyme that decomposes hydrogen peroxide to water and molecular oxygen, to a pyrite suspension reduces the oxidation rate by 40%. By contrast, hydroxyl radical does not appear to play a significant role in the oxidation mechanism. It is estimated on the basis of a molecular oxygen and sulfate mass balance that 5-6% of the molecular oxygen is consumed without forming sulfate.

  2. [Characterization of oxidation on pyrite by in situ attenuated total reflection-Fourier transform infrared spectroscopy].

    Science.gov (United States)

    Zhang, Ping; Chen, Yong-Heng; Liu, Juan; Wang, Chun-Lin

    2008-11-01

    Pyrite is one of common natural minerals in the environment, which is easily oxidated and is the main source of acidity mine drainage (AMD). The study on the oxidation of pyrite is helpful to comprehend the mechanism of its pollution. In the present paper, the oxidation of pyrite under the condition of air and water was respectively investigated by the attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) through the designing experiment on the formation of carbon dioxide by the reaction of carbonate in pyrite with sulfuric acid formed by the oxidation of pyrite. The CO2 measurement by in situ ATR indicated that the oxidation rate of pyrite both in the air and in water both reduced by time and the latter reduced more obviously than the former, which indicates that the oxidation rate of pyrite in water is slower than that in the air. In the ATR measurement, the double absorption peaks at 2 350 cm(-1) that indicates CO2 have high selectivity, and permits the in situ analysis.

  3. Flocculation of Pyrite Fines in Aqueous Suspensions with Corn Starch to Eliminate Mechanical Entrainment in Flotation

    Directory of Open Access Journals (Sweden)

    Wei Ge

    2015-10-01

    Full Text Available The hydrophilic flocculation of pyrite fines in aqueous suspensions with corn starch was studied by measuring particle size distribution, microscopy observation and micro-flotation. Furthermore, the interaction of corn starch with pyrite was investigated by determining the adsorption density and based on zeta potential measurements and X-ray photoelectron spectrometer (XPS analysis in this work. The results of the particle size distribution measurement show that corn starch can effectively aggregate pyrite fines, and the pyrite floccules (flocs are sensitive to mechanical stirring. The micro-flotation results suggest that the mechanical entrainment of pyrite fines in flotation can be effectively eliminated through the formation of large-size flocs. The zeta potential of pyrite particles decreases with the addition of corn starch. The XPS results prove that carboxyl groups are generated on the digested corn starch, and both iron hydroxyl compounds and ferrous disulfide on the pyrite surface can chemically interact with the corn starch digested by sodium hydroxide.

  4. Particulate Pyrite Autotrophic Denitrification (PPAD) for Remediation of Nitrate-contaminated Groundwater

    Science.gov (United States)

    Tong, S.; Rodriguez-Gonzalez, L. C.; Henderson, M.; Feng, C.; Ergas, S. J.

    2015-12-01

    The rapid movement of human civilization towards urbanization, industrialization, and increased agricultural activities has introduced a large amount of nitrate into groundwater. Nitrate is a toxic substance discharged from groundwater to rivers and leads to decreased dissolved oxygen and eutrophication. For this experiment, an electron donor is needed to convert nitrate into non-toxic nitrogen gas. Pyrite is one of the most abundant minerals in the earth's crust making it an ideal candidate as an electron donor. The overall goal of this research was to investigate the potential for pyrite to be utilized as an electron donor for autotrophic denitrification of nitrate-contaminated groundwater. Batch studies of particulate pyrite autotrophic denitrification (PPAD) of synthetic groundwater (100 mg NO3--N L-1) were set up with varying biomass concentration, pyrite dose, and pyrite particle size. Reactors were seeded with mixed liquor volatile suspended solids (VSS) from a biological nitrogen removal wastewater treatment facility. PPAD using small pyrite particles (treatment and promoted the utilization of pyrite in the field of environmental remediation.

  5. Abundances and isotopic compositions of rhenium and osmium in pyrite samples from the Huaibei coalfield, Anhui, China

    Science.gov (United States)

    Liu, Gaisheng; Chou, C.-L.; Peng, Z.; Yang, G.

    2008-01-01

    Two pyrite samples from the Shihezi Formation (Lower Permian), Huaibei coalfield, Anhui, China, have been analyzed for abundances and isotopic compositions of rhenium and osmium using negative thermal ion mass spectrometry. The Re-Os ages of the pyrites are 64.4 and 226 Ma, which are younger than the formation age of the coal seam. The pyrite samples may consist of pyrite formed at various stages during the history of coal formation. The ??Osvalues of the two pyrite samples are +17 and +18, respectively. Such high ??Osvalues are reported for the first time for recycles crustal materials from a sedimentary basin. ?? Springer-Verlag 2007.

  6. Geochemical investigation of the galvanic effects during oxidation of pyrite and base-metals sulfides.

    Science.gov (United States)

    Chopard, Aurélie; Plante, Benoît; Benzaazoua, Mostafa; Bouzahzah, Hassan; Marion, Philippe

    2017-01-01

    Predicting the water quality at mine sites is of significant importance for developing mines with respect for the environment. Acid mine drainage (AMD) occurs when sulfides are in contact with oxygen and water, and several parameters and mechanisms influence final drainage quality. Galvanic interactions influence the reactivity of sulfide minerals, which act as semi-conductors. These galvanic interactions have been insufficiently studied in the context of AMD generation. In this study, the influence of pyrite on the reactivity of sphalerite and chalcopyrite was investigated. Five blends, comprised of free grains of quartz/pyrite, quartz/chalcopyrite, quartz/sphalerite, quartz/pyrite/chalcopyrite, and quartz/pyrite/sphalerite, were subjected to geochemical testing. Five weathering cells were monitored over a 200-day period during which they were leached twice weekly. Leachates were analyzed for pH, Eh, electrical conductivity, and sulfate and metal concentrations. The results of these analyses showed that galvanic interactions occurred between free sulfide grains. Pyrite was galvanically protected over the full testing period in the quartz/pyrite/chalcopyrite blend, and partially protected in the quartz/pyrite/sphalerite blend. Moreover, the release of Cu from chalcopyrite and Zn, Mn, and Cd from sphalerite was accelerated in the presence of pyrite. This work provides a better understanding of the influence of pyrite on chalcopyrite and sphalerite reactivity by highlighting the galvanic effects. In the future, to improve the reliability of AMD prediction tests, galvanic interactions should be considered in both the prediction of the acid generation potential and the estimation of metal and metalloid release rates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Adsorção de xantatos sobre pirita Adsorption of xanthate on pyrite

    Directory of Open Access Journals (Sweden)

    Fábio Garcia Penha

    2001-10-01

    Full Text Available This paper presents a study of adsorption of xanthate with alkyl chain of two (C2XK, four (C4XK and eight (C8XK atoms of carbon, on pyrite from Santa Catarina, Brazil. The results showed that pyrite surface changes from hydrophilic to hydrophobic when xanthate is adsorbed increasing the contact angle to 35º for C2XK, and to 90º for C4XK and C8XK. The rate of flotation of pyrite particles after adsorption increases with the increase of the number of carbon atoms in the alkyl chain in agreement with the results of contact angle measurements.

  8. Quantification of Pyritic Sulfur of One Colombian Coal by Mössbauer Spectroscopy

    Science.gov (United States)

    Reyes, F.; Pérez Alcázar, G. A.; Barraza, J. M.; Bohórquez, A.; Tabares, J. A.

    2003-06-01

    The aim of this work was to identify and quantify by means of Mössbauer spectroscopy the amount of pyritic sulfur in coal samples of the Guachinte mine, Valle, Colombia. For the quantification a calibration curve for pyritic sulfur content vs. relative spectral area ratio of sulfur and pure (99.99%) Fe-powder was obtained, using Mössbauer spectroscopy. The samples used in the calibration were the representative ones of the fractions obtained after one and two hydrocyclonic removal processes of a homogeneous sample of raw coal. A linear relationship was obtained and used to determine the amount of pyritic sulfur of the original coal.

  9. Nickel mobilization in a groundwater well field: Release by pyrite oxidation and desorption from manganese oxides

    DEFF Research Database (Denmark)

    Postma, Dieke; Larsen, Flemming

    1997-01-01

    is furthermore characterized by enhanced Mn2+ concentrations. Apparently nickel accumulates on manganese oxides during pyrite oxidation. When the water table rises again, partially oxidized pyritic layers are resubmerged, and due to an insufficient supply of oxygen, the oxidation of Fe2+ released during pyrite...... oxidation becomes incomplete. The mobilized Fe2+ may reduce manganese oxides and thereby release large amounts of Ni2+ to the groundwater. Calculations using a surface complexation model indicate retardation of nickel to be strongly affected by bulk water composition. At the background groundwater...

  10. Selective separation of arsenopyrite from pyrite by biomodulation in the presence of Acidithiobacillus ferrooxidans.

    Science.gov (United States)

    Chandraprabha, M N; Natarajan, K A; Somasundaran, P

    2004-08-15

    Effective methods for selective separation using flotation or flocculation of arsenopyrite from pyrite by biomodulation using Acidithiobacillus ferrooxidans are presented here. Adhesion of the bacterium to the surface of arsenopyrite was very slow compared to that to pyrite, resulting in a difference in surface modification of the minerals subsequent to interaction with cells. The cells were able to effectively depress pyrite flotation in presence of collectors like potassium isopropyl xanthate and potassium amyl xanthate. On the other hand the flotability of arsenopyrite after conditioning with the cells was not significantly affected. The activation of pyrite by copper sulfate was reduced when the minerals were conditioned together, resulting in better selectivity. Selective separation could also be achieved by flocculation of biomodulated samples.

  11. Electronic, thermodynamic and elastic properties of pyrite RuO_2

    Institute of Scientific and Technical Information of China (English)

    Yang Ze-Jin; Guo Yun-Dong; Wang Guang-Chang; Li Jin; Dai Wei; Liu Jin-Chao; Cheng Xin-Lu; Yang Xiang-Dong

    2009-01-01

    This paper calculates the elastic, thermodynamic and electronic properties of pyrite (Pa3) RuO_2 by the plane-wave pseudopotential density functional theory (DFT) method. The lattice parameters, normalized elastic constants, Cauchy pressure, brittle-ductile relations, heat capacity and Debye temperature are successfully obtained. The Murnaghan equation of state shows that pyrite RuO_2 is a potential superhard material. Internal coordinate parameter increases with pressure, which disagrees with experimental data. An analysis based on electronic structure and the pseudogap reveals that the bonding nature in RuO_2 is a combination of covalent, ionic and metallic bonding. A study of the elastic properties indicates that the pyrite phase is isotropic under usual conditions. The relationship between brittleness and ductility shows that pyrite RuO_2 behaves in a ductile matter at zero pressure and the degree of ductility increases with pressure.

  12. Geological significance of componential characteristics of pyrite from Shibaqinghao gold deposit in central Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    Yihong Liang; Hongying Zhang; Yanhua Ma

    2006-01-01

    There are two types of gold ore in Shibaqinghao gold deposit, mylonite ore and quartz vein ore. Pyrite accompanying with native gold in mylonite ore has Fe from 43.66 to 45.32 wt% and S from 52.64 to 53.55 wt%. It is clear that this kind of pyrite is poor in both sulphur and iron. That means that the mylonite ore may be related to metamorphic water. Pyrite in the quartz vein ore has Fe from 44.38 to 45.30 wt% and S from 53.08 to 54.00 wt%. It means that this kind of pyrite is poor in iron but rich in sulphur, while the quartz vein ore may be related to magma water.

  13. Pyrite Iron Sulfide Solar Cells Made from Solution Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Law, Matt [Univ. of California, Irvine, CA (United States)

    2017-03-21

    This document summarizes research done under the SunShot Next Generation PV II project entitled, “Pyrite Iron Sulfide Solar Cells Made from Solution,” award number DE-EE0005324, at the University of California, Irvine, from 9/1/11 thru 11/30/16. The project goal was to develop iron pyrite (cubic FeS2) as an absorber layer for solution-processible p-n heterojunction solar cells with a pathway to >20% power conversion efficiency. Project milestones centered around seven main Tasks: (1) make device-quality pyrite thin-films from solar ink; (2) develop an ohmic bottom contact with suitable low resistivity; (3) produce a p-n heterojunction with VOC > 400 mV; (4) make a solar cell with >5% power conversion efficiency; (5) use alloying to increase the pyrite band gap to ~1.2-1.4 eV; (6) produce a p-n heterojunction with VOC > 500 mV; and finally (7) make a solar cell with >10% power conversion efficiency. In response to project findings, the Tasks were amended midway through the project to focus particular effort on passivating the surface of pyrite in order to eliminate excessively-strong surface band bending believed to be responsible for the low VOC of pyrite diodes. Major project achievements include: (1) development and detailed characterization of several new solution syntheses of high-quality thin-film pyrite, including two “molecular ink” routes; (2) demonstration of Mo/MoS2 bilayers as good ohmic bottom contacts to pyrite films; (3) fabrication of pyrite diodes with a glass/Mo/MoS2/pyrite/ZnS/ZnO/AZO layer sequence that show VOC values >400 mV and as high as 610 mV at ~1 sun illumination, although these high VOC values ultimately proved irreproducible; (4) established that ZnS is a promising n-type junction partner for pyrite; (5) used density functional theory to show that the band gap of pyrite can be increased from ~1.0 to a more optimal 1.2-1.3 eV by alloying with oxygen; (6) through extensive measurements of ultrahigh

  14. New method for the simultaneous determination of pyrite content and proximate analysis in coal

    Energy Technology Data Exchange (ETDEWEB)

    Aylmer, D.M.; Rowe, M.W.

    1984-01-01

    A combined thermogravimetric and thermomagnetometric procedure using inert, oxidising and reducing gases is described. It is shown to give good agreement with the ASTM methods and to have advantages over the latter, especially as regards occluded or weathered pyrite.

  15. The role of sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, K.; Tsunekawa, M.; Ohtsuka, T.; Konno, H. [Hokkaido University, Sapporo (Japan). Graduate School of Engineering

    1998-02-28

    The paper investigates the role of the sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering in order to clarify the effects of the bacteria on the dissolution behavior of pyrite and the formation of secondary minerals using Raman spectroscopy and powder X-ray diffraction (XRD) in addition to solution analysis. It was found that T. thiooxidans, when present with the iron-oxidizing bacteria Thiobacillus ferrooxidans, enhanced the dissolution of Fe and S species for pyrite, whereas T. thiooxidans alone did not oxidize pyrite. Enhancement of the consumption of elemental sulfur and regeneration of Fe(II) ions were also observed with T. thiooxidans together with T. ferrooxidans, while this did not occur with T. ferrooxidans alone.

  16. Copper-arsenic decoupling in an active geothermal system: A link between pyrite and fluid composition

    Science.gov (United States)

    Tardani, Daniele; Reich, Martin; Deditius, Artur P.; Chryssoulis, Stephen; Sánchez-Alfaro, Pablo; Wrage, Jackie; Roberts, Malcolm P.

    2017-05-01

    Over the past few decades several studies have reported that pyrite hosts appreciable amounts of trace elements which commonly occur forming complex zoning patterns within a single mineral grain. These chemical zonations in pyrite have been recognized in a variety of hydrothermal ore deposit types (e.g., porphyry Cu-Mo-Au, epithermal Au deposits, iron oxide-copper-gold, Carlin-type and Archean lode Au deposits, among others), showing, in some cases, marked oscillatory alternation of metals and metalloids in pyrite growth zones (e.g., of Cu-rich, As-(Au, Ag)-depleted zones and As-(Au, Ag)-rich, Cu-depleted zones). This decoupled geochemical behavior of Cu and As has been interpreted as a result of chemical changes in ore-forming fluids, although direct evidence connecting fluctuations in hydrothermal fluid composition with metal partitioning into pyrite growth zones is still lacking. In this study, we report a comprehensive trace element database of pyrite from the Tolhuaca Geothermal System (TGS) in southern Chile, a young and active hydrothermal system where fewer pyrite growth rims and mineralization events are present and the reservoir fluid (i.e. ore-forming fluid) is accessible. We combined the high-spatial resolution and X-ray mapping capabilities of electron microprobe analysis (EMPA) with low detection limits and depth-profiling capacity of secondary-ion mass spectrometry (SIMS) in a suite of pyrite samples retrieved from a ∼1 km drill hole that crosses the argillic (20-450 m) and propylitic (650-1000 m) alteration zones of the geothermal system. We show that the concentrations of precious metals (e.g., Au, Ag), metalloids (e.g., As, Sb, Se, Te), and base and heavy metals (e.g., Cu, Co, Ni, Pb) in pyrite at the TGS are significant. Among the elements analyzed, As and Cu are the most abundant with concentrations that vary from sub-ppm levels to a few wt.% (i.e., up to ∼5 wt.% As, ∼1.5 wt.% Cu). Detailed wavelength-dispersive spectrometry (WDS) X

  17. Chalcophile Siderophile Trace Element Systematics of Hydrothermal Pyrite from Martian Regolith Breccia NWA 7533

    Science.gov (United States)

    Lorand, J.-P.; Hewins, R. H.; Humayun, M.; Remusat, L.; Zanda, B.; La, C.; Pont, S.

    2016-08-01

    Martian impact breccia NWA 7533 contains hydrothermal pyrite. Laser ablation ICPMS analyses show that its chalcophile siderophile element content was inherited from both early meteorite bombardment and later hydrothermal inputs from H2S fluids.

  18. Pyrite Genesis During Early Diagenesis in Yellow Sea and East China Sea

    Institute of Scientific and Technical Information of China (English)

    段伟民; 陈丽蓉

    1994-01-01

    The content and isotopic compositions of different sulphur species in pore-water and solid phases have been examined on five sediment cores taken from muddy sediment region in the Yellow Sea and the East China Sea. Relationships among these data have been investigated with the combination of morphology of mineral pyrite and organic matter so as to role out the diagenetic behaviour of sulphur species at the early stage of diagenesis in modern marine sediment and the origin of pyrite formation.

  19. Preparation of pyrite-coated sand grains for research on roll-type uranium deposits

    Science.gov (United States)

    Gent, Carol A.

    1977-01-01

    Ordinary quartz sand grains can be coated with pyrite for use in laboratory experiments on the genetic geochemistry of roll-type uranium deposits. The sand is first added to a ferric chloride solution. The slow addition of sodium hydroxide to the mixture gives the sand grains an iron oxide coating. This coating is then converted to pyrite by reaction with hydrogen sulfide, thus yielding a product suitable for experimental use.

  20. The Fe removal through mineralogical phase transformation of pyrite by physicochemical method

    Science.gov (United States)

    Kim, BongJu; Cho, Kanghee; Jo, JiYu; Bak, GeonYeong; Choi, NagChoul; Park*, Cheonyoung

    2015-04-01

    Gold is often associated with sulfide minerals (arsenopyrite, pyrite, chalcopyrite, pyrrhotite, galena) as ''invisible'' gold that is thought to consist either of submicrometer metallic particles or to be bound to sulfur in metal sulfide lattice. Pyrite is one of the major minerals accumulating gold in most ores, although a solubility of Au in nonarsenian pyrite is minor, and increased concentrations of gold are associated with arsenic content and iron deficiency. The objective of this study was to investigate the Fe removal through mineralogical phase transformation of pyrite by physical treatment (high frequency) and chemical leaching (ammonia solvent). The high frequency treatment experiment for the pyrite showed that (1) the pyrite phase was transformed pyrrhotite and magnetite, (2) mass loss of the sample by volatilization of included sulfur(S) in pyrite. The treated pyrite by high frequency was observed rim structure from photomicrograph result. Fe removal experiments for were performed under various conditions of high frequency exposure (10~60min), grain size (+140 mesh~-325mesh), sulfuric acid concentration (0.5~3.0M), ammonia sulfate concentration (1.7~6.8M), hydrogen peroxide concentration (0.5~3.0M). Increasing the high frequency exposure produced a positive effect on Fe removal in arsenopyrite. The highest percentage Fe removal of 95.53% was obtained under the following conditions by ammonia solvent: grain size = -325mesh, sulfuric acid concentration = 2.0M, ammonia sulfate concentration = 5.1M, hydrogen peroxide concentration = 1.0M. This subject is supported by Korea Ministry of Environment(MOE) as "Advanced Technology Program for Environmental Industry".

  1. Enhanced bioleaching on attachment of indigenous acidophilic bacteria to pyrite surface

    Science.gov (United States)

    Wi, D. W.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.

    2012-04-01

    In recent years, bioleaching has been widely applied on an industrial scale due to the advantages of low cost and environment friendliness. The direct contact mechanism of bioleaching assumes the action of a metal sulfide-attached cell oxidizing the mineral by an enzyme system with oxygen to sulfate and metal cations. Fundamental surface properties of sulfide particles and leaching-bacteria in bioleaching play the key role in the efficiency of this process. The aim of this work is to investigate of direct contact bioleaching mechanism on pyrite through attachment properties between indigenous acidophilic bacteria and pyrite surfaces. The bacteria were obtained from sulfur hot springs, Hatchobaru thermal electricity plant in Japan. And pyrite was collected from mine waste from Gwang-yang abandoned gold mines, Korea. In XRD analyses of the pyrite, x-ray diffracted d-value belong to pyrite was observed. The indigenous acidophilic bacteria grew well in a solution and over the course of incubation pH decreased and Eh increased. In relation to a bacterial growth-curve, the lag phase was hardly shown while the exponential phase was very fast. Bioleaching experiment result was showed that twenty days after the indigenous acidophilic bacteria were inoculated to a pyrite-leaching medium, the bacterial sample had a greater concentration of Fe and Zn than within the control sample. In SEM-EDS analyses, rod-shaped bacteria and round-shaped microbes were well attached to the surface of pyrite. The size of the rod-shaped bacteria ranged from 1.05~1.10 ? to 4.01~5.38 ?. Round-shaped microbes were more than 3.0 ? in diameter. Paired cells of rod-shaped bacteria were attached to the surface of pyrite linearly.

  2. Application of fuel cell for pyrite and heavy metal containing mining waste

    Science.gov (United States)

    Keum, H.; Ju, W. J.; Jho, E. H.; Nam, K.

    2015-12-01

    Once pyrite and heavy metal containing mining waste reacts with water and air it produces acid mine drainage (AMD) and leads to the other environmental problems such as contamination of surrounding soils. Pyrite is the major source of AMD and it can be controlled using a biological-electrochemical dissolution method. By enhancing the dissolution of pyrite using fuel cell technology, not only mining waste be beneficially utilized but also be treated at the same time by. As pyrite-containing mining waste is oxidized in the anode of the fuel cell, electrons and protons are generated, and electrons moves through an external load to cathode reducing oxygen to water while protons migrate to cathode through a proton exchange membrane. Iron-oxidizing bacteria such as Acidithiobacillus ferrooxidans, which can utilize Fe as an electron donor promotes pyrite dissolution and hence enhances electrochemical dissolution of pyrite from mining waste. In this study mining waste from a zinc mine in Korea containing 17 wt% pyrite and 9% As was utilized as a fuel for the fuel cell inoculated with A. ferrooxidans. Electrochemically dissolved As content and chemically dissolved As content was compared. With the initial pH of 3.5 at 23℃, the dissolved As concentration increased (from 4.0 to 13 mg/L after 20 d) in the fuel cell, while it kept decreased in the chemical reactor (from 12 to 0.43 mg/L after 20 d). The fuel cell produced 0.09 V of open circuit voltage with the maximum power density of 0.84 mW/m2. Dissolution of As from mining waste was enhanced through electrochemical reaction. Application of fuel cell technology is a novel treatment method for pyrite and heavy metals containing mining waste, and this method is beneficial for mining environment as well as local community of mining areas.

  3. Progressive oxidation of pyrite in five bituminous coal samples: An As XANES and 57Fe Mössbauer spectroscopic study

    Science.gov (United States)

    Kolker, Allan; Huggins, Frank E.

    2007-01-01

    Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32–1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26–0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O2 atmosphere; (3) room atmosphere (relative humidity ∼20–60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and 57Fe Mössbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. 57Fe Mössbauer spectroscopy also shows a much greater proportion of Fe3+ forms (jarosite, Fe3+ sulfate, FeOOH) for samples stored under wet conditions, but much less

  4. Spatial Mapping for Managing Oxidized Pyrite (FeS2 in South Sumatra Wetlands, Indonesia

    Directory of Open Access Journals (Sweden)

    M. Edi Armanto

    2015-05-01

    Full Text Available The research aimed to analyze spatial mapping for managing oxidized pyrite (FeS2 in South Sumatra wetlands, Indonesia. The field observations are done by exploring several transect on land units. The field description refers to Soil Survey Staff (2014. Water and soil samples were taken from selected key areas for laboratory analysis. The vegetation data was collected by making sample plots (squares method placed on each vegetation type with plot sizes depending on the vegetation type, namely 10 x 10 m for secondary forests and 5 x 5 m for shrubs and grass. The observations of surface water level were done during the river receding with units of m above sea level (m asl. The research results showed that pyrite formation is largely determined by the availability of natural vegetation as Sulfur (S donors, climate and uncontrolled water balance and supporting fauna such as crabs and mud shrimp.  Climate and water balance as well as supporting faunas is the main supporting factors to accelerate the process of pyrite formation. Oxidized pyrite serves to increase soil acidity, becomes toxic to fish ponds and arable soils, plant growth and disturbing the water and soil nutrient balances. Oxidized pyrite is predominantly accelerated by the dynamics of river water and disturbed natural vegetation by human activities.  The pyrite oxidation management approach is divided into three main components of technologies, namely water management, land management and commodity management.

  5. Mineralogy, geochemistry and pyrite content of Bulgarian subbituminous coals, Pernik Basin

    Energy Technology Data Exchange (ETDEWEB)

    Kostova, I.; Petrov, O.; Kortenski, J. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Applied Mineralogy

    1996-08-01

    The mineralogy and geochemistry of Pernik subbituminous coals (coal bed A) and some genetic peculiarities related to the mineral formation were studied. The mineral matter of the coal consists chiefly of pyrite, kaolinite, siderite, quartz and calcite. Other minerals (dolomite, ankerite, plagioclase and some sulphates) are present in minor amounts, some occurring as accessory single crystals. Pyrite is them main mineral in these coals and exhibits a large array of textures and morphology. Isolated and clustered euhedral, bacterial and inorganic framboidal, cluster-like, homogeneous and microconcretional massive, infilling and replacing anhedral, and cleat-filling and fracture-filling infiltrational pyrite types were observed. Four stages of mineralization were distinguished: pyrite-kaolinite, pyrite, pyrte-siderite and sulphate stages. The amount of pyrite present in two sections of coal bed A was determined by quantitative powder X-ray diffraction analysis. The concentrations of 37 trace elements were determined. As, Cu, Co, Ni, Zn, Pb, V, Ti, Mo Rb, Cr and Mn are typomorphic for this coal. On the basis of their relation to organic or inorganic matter, four groups of trace elements were subdivided; and on the basis of cluster analysis four associations were differentiated. 19 refs., 31 figs., 2 tabs.

  6. Bio-oxidation of pyrite, chalcopyrite and pyrrhotite by Acidithiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper deals with the bio-oxidation processes by Acidithiobacillus ferrooxidans of pyrite, chalcopyrite and pyrrhotite. Our experimental results show distinctive bio-oxidation characteristics for the three sulfide minerals. In the presence of A. ferrooxidans, the sulfide oxidation rates generally decrease in the order of pyrrhotite, chalcopyrite and pyrite. The pH during bio-oxidation of pyrite tends to decrease as a whole, whereas a rise-fall pattern was recorded for both chalcopyrite and pyrrhotite in their pH variations. No deposition was observed during the bio-oxidation of pyrite, suggesting a possible link to lower pH value in the process. However, large amounts of jarosite and element sulfur were determined in the bio-oxidation processes of chalcopyrite and pyrrhotite. A. ferrooxidans individuals were found directly as attachments to erosion pits on the smooth surface of pyrite. The erosion pits are similar to the bacterium in shape and length, and thus are probably products of dissolution of organic acid secreted by the cells on the mineral surface. More complicatedly, biofilm exists on the surfaces of chalcopyrite and pyrrhotite. This type of structured community of A. ferrooxidans is enclosed in the extracellular polymeric substances (EPS), and covered with the deposition generated in the bio-oxidation processes of chalcopyrite and pyrrhotite. Different bio-oxidation processes of pyrite, chalcopyrite and pyrrhotite may be linked mainly to characteristics of individual minerals and the pH in the reaction solution of the bio-oxidation system.

  7. A kinetic assessment of substantial oxidation by sulfolobus acidocaldarius in pyrite dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Vitaya, V.B.; Koizumi, J.; Toda, K. (King Mongkuts Institute of Technology, Bangkok (Thailand). Dept. of Chemical Engineering)

    1994-01-01

    The relative contributions of biological and chemical reactions to the total rate of pyrite oxidation in the presence of Sulfolobus acidocaldarius were studied on the basis of experimental work coupled with mathematical modeling. Kinetic constants for the individual reactions were determined in independent experiments. The specific growth rate of cells on the pyrite surface, which is the only unknown parameter, was assumed to be [mu](s) 0.1 h[sup -1] and justified by the agreement of the simulated results of a proposed model and the experimental results. The model includes: reversible adsorption, biological dissolution of pyrite by the adsorbed cells, chemical dissolution of pyrite accompanied by the reduction of ferric ions to ferrous ions, biochemical oxidation of ferrous ions to ferric ions by free cells, and change of the surface area of pyrite particles. It is suggested that the contributions of direct (biological) and indirect (chemical) reaction to the total rate of pyrite oxidation were in a ratio of 2:1.

  8. Degradation of off-gas toluene in continuous pyrite Fenton system.

    Science.gov (United States)

    Choi, Kyunghoon; Bae, Sungjun; Lee, Woojin

    2014-09-15

    Degradation of off-gas toluene from a toluene reservoir and a soil vapor extraction (SVE) process was investigated in a continuous pyrite Fenton system. The removal of off-gas toluene from the toluene reservoir was >95% by 8h in the pyrite Fenton system, while it was ∼97 % by 3h in classic Fenton system and then rapidly decreased to initial level by 8h. Continuous consumption of low Fe(II) concentration dissolved from pyrite surface (0.05-0.11 mM) was observed in the pyrite Fenton system, which can lead to the effective and successful removal of the gas-phase toluene due to stable production of OH radical (OH). Inhibitor and spectroscopic test results showed that OH was a dominant radical that degraded gas-phase toluene during the reaction. Off-gas toluene from the SVE process was removed by 96% in the pyrite Fenton system, and remnant toluene from rebounding effect was treated by 99%. Main transformation products from toluene oxidation were benzoic acid (31.4%) and CO2 (38.8%) at 4h, while traces of benzyl alcohol (1.3%) and benzaldehyde (0.7%) were observed. Maximum operation time of continuous pyrite Fenton system was estimated to be 56-61 d and its optimal operation time achieving emission standard was 28.9 d. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Research on Genesis of Pyrite near the Permian-Triassic Boundary in Meishan, Zhejiang, China

    Institute of Scientific and Technical Information of China (English)

    JIANG Yao-fa; TANG Yue-gang; CHOU Chen-lin

    2006-01-01

    The content and crystal forms of pyrite and sulfur isotope composition of pyrite sulfur as well as its vertical distribution near the Permian-Triassic (P/T) boundary in the Meishan section, Changxing county, Zhejiang province, China were studied using geological, petrological, mineralogical and geochemical methods (techniques). The result showed that the genesis of abundant pyrites in bed 24e2 at the uppermost part of the Changxing Formation in the Meishan section may be related to volcanic activity. In bed 24e2 of the Meishan section, pyrite has its highest content of 1.84% and the sulfur isotope composition has the highest δ34S value at +2.2‰ which is very similar to that of the average value of volcanic gas. There are some volcanic products such as β-quartz, siliceous cylinders and siliceous spherules which coexisted with pyrites in beds 24e2 and 24f. It can be concluded that a large quantity of volcanic ash fell into the South China Sea and was incorporated into marine sediments during the formation of limestone at the uppermost part of the Changxing Formation. The volcanic eruption with massive amounts of H2S and SO2 gas at the end of the Permian period resulted in the enrichment of H2S in the South China Sea areas. The reaction of H2S with reactive iron minerals formed the mass of abundant pyrites.

  10. Biogeochemistry of pyrite and iron sulfide oxidation in marine sediments

    DEFF Research Database (Denmark)

    Schippers, A.; Jørgensen, BB

    2002-01-01

    Pyrite (FeS2) and iron monosulfide (FeS) play a central role in the sulfur and iron cycles of marine sediments, They may be buried in the sediment or oxidized by O-2 after transport by bioturbation to the sediment surface. FeS2 and FeS may also be oxidized within the anoxic sediment in which NO3......-, Fe(III) oxides, or MnO2 are available as potential electron acceptors. In chemical experiments, FeS2 and FeS were oxidized by MnO2 but not with NO3- or amorphous Fe(III) oxide (Schippers and Jørgensen, 2001). Here we also show that in experiments with anoxic sediment slurries, a dissolution of tracer......-marked (FeS2)-Fe-55 occurred with MnO2 but not with NO3- or amorphous Fe(III) oxide as electron acceptor. To study a thermodynamically possible anaerobic microbial FeS, and FeS oxidation with NO3- or amorphous Fe(III) oxide as electron acceptor, more than 300 assays were inoculated with material from several...

  11. Early diagenetic pyrite morphology in a mudstone-dominated succession: the Lower Jurassic Cleveland Ironstone Formation, eastern England

    Science.gov (United States)

    Taylor, K. G.; Macquaker, J. H. S.

    2000-03-01

    Diagenetic pyrite in the mudstones and ironstones of the Lower Jurassic Cleveland Ironstone Formation of eastern England exhibits two distinct morphologies: framboidal pyrite, commonly associated with organic matter, and euhedral pyrite, associated with detrital clay pellets. These two morphologies are mutually exclusive in occurrence. Framboidal pyrite is present in clay-rich mudstones, ooidal ironstones, apatite-rich units and some silt-rich mudstones. Euhedral pyrite is present in silt-rich and sand-rich mudstones. δ34S isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea-water, although both probably acted as sites for continued pyrite precipitation during burial. It is proposed that framboidal pyrite precipitated from iron-dominated porewaters at sites of sulfide supply (i.e. in the region of organic matter as a result of bacterial sulfate reduction) where, locally, sulfide production rates were high enough for porewaters to reach supersaturation with respect to FeS. Euhedral pyrite also precipitated from iron-dominated porewaters, but sulfide production rates from organic matter was such that FeS saturation was not reached at the sites of sulfide production. Instead, euhedral pyrite was precipitated directly from porewater when FeS2 saturation was reached. The control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments. The sand-rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with O2-rich bottom waters. The ironstones and apatite-rich units were deposited under very low sedimentation rates, and as a result organic matter contents were very low and iron reduction dominated early diagenesis, which inhibited sulfate-reduction. The presence of minor framboidal pyrite within these units, however, suggests that

  12. DFT study on the galvanic interaction between pyrite (100) and galena (100) surfaces

    Science.gov (United States)

    Ke, Baolin; Li, Yuqiong; Chen, Jianhua; Zhao, Cuihua; Chen, Ye

    2016-03-01

    The galvanic interaction between pyrite and galena surface has been investigated using density functional theory (DFT) method. The calculated results show that galvanic interactions between pyrite and galena surface are decreased with the increase of contact distance. The galvanic interactions still occurs even the distance larger than the sum of two atoms radius (≈2.8 Å), and the limit distance of galvanic interaction between galena and pyrite surface is about 10 Å, which is consistent with the quantum tunneling effect. Through Mulliken charge population calculation, it is found that electrons transfer from galena to pyrite. For galena surface, Pb 6s and 6p states lose electrons and S 3p state loses a small amount of electrons, which causes the electron loss of galena. For pyrite surface, Fe 4p state obtains large numbers of electrons, resulting in the decrease of positive charge of Fe atom. However, the 3p state of S atom loses a small numbers of electrons. The reactivity of mineral surface has also been studied by calculating the frontier orbitals of minerals. Results suggest that the highest occupied molecular orbital (HOMO) coefficients of galena are increased whereas those of pyrite are decreased with the enhancing galvanic interaction, indicating that the oxidation of galena surface would be enhanced due to the galvanic interaction. The Fukui indices and dual descriptor values of surface atoms suggest that the nucleophilicity of the galena surface increases, meanwhile, the electrophilicity of pyrite surface increases with the decrease of the contact distance. In addition, the density of states (DOS) of atoms results show that the activity of electrons in Pb 6s and 6p orbitals enhances while the activity of electrons in Fe 3d orbitals weaken due to the galvanic contact between minerals.

  13. Action time effect of lime on its depressive ability for pyrite

    Institute of Scientific and Technical Information of China (English)

    Tichang Sun

    2004-01-01

    Two sample groups of bulk concentrates consisting mainly of pyrite and chalcopyrite from Daye and Chenghchao Mines in Hubei Province of China were used to investigate the effect of the action time of lime on its depressive ability for pyrite. The experimental results conducted with different samples and collectors showed that the action time between lime and pyrite markedly influences the depressive ability of lime. The depressive ability of lime increased with the action time increasing. It was also proved that the depressive results obtained at a large lime dosage after a shorter action time are similar to those obtained at a small lime dosage after a longer action time. The increase of depressive ability of lime after a longer action time is because that there are different mechanisms in different action time. The composition on the surface of pyrite acted for different time with lime was studied by using ESCA (Electron Spectroscopic Chemical Analysis). The results showed that iron hydroxide and calcium sulphate formed on the pyrite surface at the presence of lime in the pulp but the amounts of iron hydroxide and calcium sulphate were different at different action time. At the beginning action time the compound formed on the pyrite surface was mainly calcium sulphate and almost no iron hydroxide formed; but with the action time increasing, iron hydroxide formed. The longer the action time, the more iron hydroxide and the less calcium sulphate formed. It was considered that the stronger depressive ability of lime after a longer action time is because more iron hydroxide forms on the pyrite surface.

  14. Dynamics of electrodeposition of tetraethylthioram disulphide(TETD) on pyrite surface

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiostatic and ehronopotentiometry. Tetraethylthioram disulphide (TETD) was electrodeposited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i = 1/(9.08×10-5 + 4.77 × 10-3 t0.5 ), and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10-6 cm2/s.At pH 11.4, the thickness of TETD adsorbed on pyrite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η = 0.116- 0.0641og[1-(t/τ)0.5]. The kinetic parameters were determined as follows: the exchange current density (io) is 3.08μA/cm2; the transmission coefficient(α) is 0.462.

  15. Pyrite Oxidation in Leaching Process of Radionuclides and Heavy Metals from Uranium Mill Tailings

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Pyrite is a sensitive mineral in the geological environment, and its oxidation produces an important geochemical and environmental effect on the control of the redox and pH conditions. Column experiment results were used for modeling the geochemical processes in uranium mill tailings under lcaching conditions. Oxidation of pyrite dominates the control of the tailings leaching process. The experimental and modeling results show that the leachate chemistry changes substantially with the decrease in pyrite consumption. In the initial stage of the leaching experiment, the pyrite is consumed several hundred times greater than that in the later stages, for much more oxygen is present in the tailings in the initial stage. As the experiment continues, the tailings is gradually saturated with water and the oxygen concentration greatly decreases and so does pyrite consumption. The experimental and modeling results are useful for the design of mill tailing decommissioning., oxidation process and transport of radioactive nuclides and heavy metals can be constrained by controlling the oxygen concentration of tailings and the infiltration of meteoric water.

  16. Trace element mapping of pyrite from Archean gold deposits – A comparison between PIXE and EPMA

    Energy Technology Data Exchange (ETDEWEB)

    Agangi, A., E-mail: aagangi@uj.ac.za [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa); Przybyłowicz, W., E-mail: przybylowicz@tlabs.ac.za [Materials Research Department, iThemba LABS, National Research Foundation, Somerset West 7129 (South Africa); AGH University of Science and Technology, Faculty of Physics & Applied Computer Science, Al. A. Mickiewicza 30, 30-059 Krakow (Poland); Hofmann, A., E-mail: ahofmann@uj.ac.za [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa)

    2015-04-01

    Chemical zoning of pyrites can record the evolution of mineralising fluids at widely varying P–T conditions ranging from diagenesis to medium-grade metamorphism. If preserved, zoning can reveal growth textures, brecciation and veining, resorption and recrystallisation events, thus shedding light on the processes that contributed to ore formation. Chemical zoning of sulfides is invisible in optical microscopy, but can be studied by chemical etching, high-contrast back-scattering electron images, and elemental imaging. In this study we compared micro-PIXE and WDS-EPMA elemental maps on the chemically zoned pyrites in mineralised vein-bearing samples from the Sheba and Fairview gold mines in the Barberton Greenstone Belt, South Africa. Elemental images show complex distribution of trace elements, suggesting multiple events of pyrite crystallisation and gold deposition. EPMA maps show fine-scale variations reflecting growth and recrystallisation textures marked, in particular, by variations of As, Ni, and Co. In PIXE maps, gold occurs both as finely-distributed and discrete inclusions, suggesting incorporation in the pyrite structure as solid solution, and deposition as electrum inclusions, respectively. Micro-PIXE and EPMA provide complementary information, forming together a powerful tool to obtain information on chemical zoning of pyrites in ore deposits.

  17. A demonstration of an affinity between pyrite and organic matter in a hydrothermal setting

    Directory of Open Access Journals (Sweden)

    Holm Nils G

    2011-02-01

    Full Text Available Abstract One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials.

  18. Pyrite Formation in Organic-rich Clay, Calcitic and Coal-Forming Environments

    Institute of Scientific and Technical Information of China (English)

    Gordana DEVI(C); Petar PFENDT; Branimir JOVAN(C)I(C)EVI(C); Zoran POPOVIC

    2006-01-01

    The early diagenetic characteristics of pyrite formation processes in a Miocene freshwater sequence of mixed sediments (coal fragments in clays, sandstones or shales) alternating with continuous brown coal layers was investigated. Based on abundant minerals, the following main sedimentary environments were distinguished: the illite-montmorillonitic (I-M), calcitic (Ct) and coal-forming environment (CL). For these hydrogeochemically differing environments the effects of limiting factors on the pyrite formation process (availability of sulphate and Fe, amount of organic matter and participation of organic sulphur) were assessed by correlation analysis. Significant differences in the effects of these limiting factors in the particular environments were observed. These differences were explained taking in account the different oxidative activity, Fe-complex and surface complex forming properties of hnmic substances in dependence of pH of environment and the abundance of sorptionally active clay minerals. In environments having a relatively low pH and containing clay minerals (I-Mand CL-environments) the oxidative activity of humic substances (Hs) on pyrite precursors was greatly prevented however pyrite formation depended on reactive Fe availability as the consequence of complex formation. On the contrary, in environments with a relatively high pH, as it was the calcitic,the oxidative activity of Hs was greatly enhanced, thus oxidizing the sulfur precursors of pyrite. The oxidation degree of organic matter was probably also a consequence of the differing activity of the humic electron-acceptors.

  19. New method for the simultaneous determination of pyrite content and proximate analysis in coal and lignite

    Energy Technology Data Exchange (ETDEWEB)

    Aylmer, D.M.

    1983-01-01

    The new method combines thermogravimetry and thermomagnetometry and utilizes inert, oxidizing, and reducing gases. Results by the new technique are compared to the ASTM method, one set obtained by the author on a Fisher Coal Analyzer and one set by the Coal Research Laboratory of the Pennsylvania State University. Comparison of thermo-magneto-gravimetric-analysis with the ASTM method indicates good agreement and comparable accuracy. These studies show that the thermo-magneto-gravimetric-analysis are: 1) ease of determination of both proximate analysis and pyrite, which permits use of unskilled technicians; 2) widespread availability of the apparatus; 3) cost effectiveness due to use of unskilled operators; 4) automation, presently available for proximate analysis on some commercial instruments and is easily accomplished for pyrite analysis, as well; 5) advantage over pyrite analysis by the ASTM method in two situations: first, when pyrite is totally surrounded by acid-insoluble organic-material and secondly where significant amounts of pyrite have been oxidized to FeSO/sub 4/; and 6) a permanent record of the measurements, which are continuous, is made in contrast to the ASTM method which records only initial and final conditions.

  20. [Limestone and pyrite-limestone constructed wetlands for treating river water].

    Science.gov (United States)

    Zhang, Jing; Li, Rui-hua; Li, Jie; Hu, Jun-song; Sun, Qian-qian

    2013-09-01

    Polluted river water was treated with limestone and pyrite-limestone subsurface horizontal constructed wetlands. The aims were to know the performance of two wetlands on removal of common pollutants, especially nitrogen and phosphorus, and analyze the actions of these minerals. The relationship between hydraulic retention time and purification performance of two constructed wetlands was studied. The optimal hydraulic retention time for pollutant removal was about 3 d, The average removal efficiency of COD, TN and TP were 51%, 70% and 95%, respectively. With same influent and hydraulic loading, the average removal efficiency of COD, NH4+ -N, TN and TP were 53.93%, 82.13%, 66%, 50.9%, and 51.66%, 77.43%, 72.06%, 97.35% for limestone and pyrite-limestone constructed wetlands, respectively. There were few differences between limestone and pyrite-limestone wetlands on COD removal, but the nitrogen and phosphorus removal of pyrite-limestone constructed wetland was higher than that of limestone constructed wetland. The phosphorus removal of pyrite-limestone wetland was more efficiency and stable, not affected by temperature.

  1. Galvanic Interaction between Chalcopyrite and Pyrite with Low Alloy and High Carbon Chromium Steel Ball

    Directory of Open Access Journals (Sweden)

    Asghar Azizi

    2013-01-01

    Full Text Available This study was aimed to investigate the galvanic interaction between pyrite and chalcopyrite with two types of grinding media (low alloy and high carbon chromium steel ball in grinding of a porphyry copper sulphide ore. Results indicated that injection of different gases into mill altered the oxidation-reduction environment during grinding. High carbon chromium steel ball under nitrogen gas has the lowest galvanic current, and low alloy steel ball under oxygen gas had the highest galvanic current. Also, results showed that the media is anodic relative to pyrite and chalcopyrite, and therefore pyrite or chalcopyrite with a higher rest potential acted as the cathode, whilst the grinding media with a lower rest potential acted as the anode, when they are electrochemically contacted. It was also found that low alloy steel under oxygen produced the highest amount of EDTA extractable iron in the slurry, whilst high carbon chromium steel under nitrogen atmosphere led to the lowest amount.

  2. Crystalomorphological Characteristics of Pyrite in Hydrothermal Gold Deposit--An Experimental Study

    Institute of Scientific and Technical Information of China (English)

    蔡元吉; 周茂

    1994-01-01

    On the basis of the geological characteristics of primary gold deposits, with an experiment on modelling the environment of gold mineralization , the evolutionary array and growth mechanism and their relationship with gold mineralization of the crystal forms of pyrite, i. e. pentagonal dodecahedron, octahedron and cube, formed under the different values of fo2, fs2, T (℃), P(Pa) and C (salinity) in the hy-drothermal system are studied. The results show that the crystal form of pyrite is not only related to the temperature L, but also affected by the geochemistry of iron and sulfur which formed pyrite and other physicochemical conditions.Our results promote the study of gold mineralization, genetic and prospecting mineralogy.

  3. Re-Os dating of pyrite from Giant Bayan Obo REE-Nb-Fe deposit

    Institute of Scientific and Technical Information of China (English)

    LIU Yulong; YANG Gang; CHEN Jiangfeng; DU Andao; XIE Zhi

    2004-01-01

    Six pyrite samples from the giant Bayan Obo REE-Nb-Fe deposit are dated by Re-Os technique. Pyrite studied is associated with barite and separated from a vein cutting REE mineralization. Pyrites analyzed contain 16-30 ng Re and 0.10-0.16 ng Os, and yield a Caledonian isochron age of 439 ± 86 Ma. High Re/Os ratio, low Os concentration and highly radiogenic Os isotopic ratios of these samples suggest that they are of crustal origin. The northern margin of the North China Block was a passive continental margin, but not a subduction zone with enormous volcanic activities in the Early Paleozoic Era. Our Re-Os result provides new evidences, showing that Bayan Obo deposit experienced a thermal disturbance of crustal origin in the Caledonian time and some isotopic systems recorded only the time of the disturbance, not the mineralization age.

  4. Hydrometallurgical-UV process to produce ferrous sulfate from the pyrite present in coal tailings

    Energy Technology Data Exchange (ETDEWEB)

    Viganico, E.M.; Silva, R.A. [South Rio Grande Federal Univ., Porto Alegre (Brazil).Graduate Program in Mining, Metallurgical and Materials Technology Center

    2010-07-01

    The oxidation of pyrite can promote acid mine drainage (AMD). This study developed a hydrometallurgical-UV route for the production of ferrous sulfate. The laboratory study was conducted using a pyrite concentrate obtained from a processed coal tailing. Leaching of the tailing was performed in packed bed columns in an oxidizing environment with an aqueous medium. Recirculation of the liquor produced an Fe{sup 3+} iron rich extract. Ultraviolet irradiation was then used to convert the Fe{sup 3+} to Fe{sup 2+}. Heat provided by the UV lamps caused the ferrous sulfate to crystallize. X-ray diffraction (XRD) studies of the crystals demonstrated that it is possible to produce commercial-grade ferrous sulfate heptahydrate crystals from the pyrite present in coal tailings. The crystals are used to treat anemia in humans and animals, and are also used as reagents for waste and waste water treatment. 7 refs., 2 tabs., 2 figs.

  5. Ferruginous Microspherules in Bauxite at Maochang, Guizhou Province, China: Products of Microbe-Pyrite Interaction?

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yuefei; WANG Rucheng; LU Jianjun; LI Yiliang

    2006-01-01

    The Maochang bauxite in Guizhou Province is one of the important aluminum ore deposits in southwestern China. Ferruginous spherules, measuring about a few microns across, were found in the transitional layer of the deposit. The EDS and XRD results show that the microspherules are composed mostly of iron (hydr)oxide minerals (goethite) with only weak presence of aluminum and silicon.Occasionally, some pyrite micrograins with dissolved surface are found associated with goethite within the spherules. It is thus suggested that microspherules are linked to pyrite oxidization. It is also thought that microbial activities contribute not only to pyrite oxidization, but also to ball-like assemblage of the iron (hydr)oxides. The mechanism of the formation of ferruginous microspherules is also believed to be important in studying geomicrobiology of bauxite.

  6. Evidence for microbial dissolution of pyrite from the Lower Cambrian oolitic limestone, South China

    Directory of Open Access Journals (Sweden)

    W. Liu

    2011-03-01

    Full Text Available The oxidative dissolution of the sulphide mineral pyrite (FeS2 has been of significant interest since it affects global geochemical cycles, generates acid mine drainage, and is used in industrial metal extraction. Several different groups of prokaryotes are known to catalyze the dissolution of pyrite and use the free energy generated from the oxidation, which may result in the dissolution of the mineral and the precipitation of the secondary ferric iron minerals either on the cell surface or is separated from the cells. However, straightforward evidence for such metabolic process in the ancient sediments is rare. Here we report pyrite crystals from the Lower Cambrian oolitic limestones that show indications of microbial erosion in various degrees. Erosion pits and tubular micro-tunnels with characteristic shapes and sizes in our samples are generally similar to those obtained from the laboratory studies on the oxidative dissolution of pyrite by iron-oxidizing bacteria. Diagenetic examination demonstrates that the bioerosion predates the consolidation of the limestone. In addition, bacillus-sized and -shaped microfossils encrusted with iron oxides are present in our samples, which are very likely to be fossilized sheaths produced by iron-oxidizing bacteria. Our findings indicate that the microbial oxidative dissolution of pyrite existed in the Cambrian shallow marine carbonate sediments. Furthermore, we suggest that characteristic pitting patterns on the pyrite crystals from ancient sediments are an important clue to trace the evolution of life, in particular, the evolution of metabolism like microbial iron oxidation in the remote past on our planet, independent of biomarkers, isotopic signals and body fossils as well.

  7. Pyrite-enhanced methylene blue degradation in non-thermal plasma water treatment reactor

    Energy Technology Data Exchange (ETDEWEB)

    Benetoli, Luis Otavio de Brito, E-mail: luskywalcker@yahoo.com.br [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Cadorin, Bruno Mena; Baldissarelli, Vanessa Zanon [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Geremias, Reginaldo [Departamento de Ciencias Rurais, Universidade Federal de Santa Catarina (UFSC), Curitibanos, SC (Brazil); Goncalvez de Souza, Ivan [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Debacher, Nito Angelo, E-mail: debacher@qmc.ufsc.br [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer We use O{sub 2} as the feed gas and pyrite was added to the non-thermal plasma reactor. Black-Right-Pointing-Pointer The methylene blue removal by NTP increased in the presence of pyrite. Black-Right-Pointing-Pointer The total organic carbon content decreased substantially. Black-Right-Pointing-Pointer The acute toxicity test showed that the treated solution is not toxic. Black-Right-Pointing-Pointer The dye degradation occurs via electron impact as well as successive hydroxylation. - Abstract: In this study, methylene blue (MB) removal from an aqueous phase by electrical discharge non-thermal plasma (NTP) over water was investigated using three different feed gases: N{sub 2}, Ar, and O{sub 2}. The results showed that the dye removal rate was not strongly dependent on the feed gas when the electrical current was kept the same for all gases. The hydrogen peroxide generation in the water varied according to the feed gas (N{sub 2} < Ar < O{sub 2}). Using O{sub 2} as the feed gas, pyrite was added to the reactor in acid medium resulting in an accentuated increase in the dye removal, which suggests that pyrite acts as a Fenton-like catalyst. The total organic carbon (TOC) content of the dye solution decreased slightly as the plasma treatment time increased, but in the presence of the pyrite catalyst the TOC removal increased substantially. The acute toxicity test using Artemia sp. microcrustaceans showed that the treated solution is not toxic when Ar, O{sub 2} or O{sub 2}-pyrite is employed. Electrospray ionization mass spectrometry analysis (ESI-MS) of the treated samples indicated that the dye degradation occurs via high energy electron impact as well as successive hydroxylation in the benzene rings of the dye molecules.

  8. Contributions to the research on the principles of a pyrite solar cell. Beitraege zur Erforschung der Grundlagen einer Pyritsolarzelle

    Energy Technology Data Exchange (ETDEWEB)

    Sailer, B.

    1994-01-01

    Within the framework of the dissertation experiences on pyrite thin film production by plasma sulfurization of iron films and thermal sulfurization of iron films in closed, evacuated quartz ampullas are given. X-ray investigation show that both methods are suitable for pyrite thin film production. Problems have been shown concerning film porosity, film adhesion on the substrates and film stability. (BWI)

  9. Atomistic simulation of the structure and elastic properties of pyrite (FeS2) as a function of pressure

    CSIR Research Space (South Africa)

    Sithole, Happy M

    2003-10-01

    Full Text Available Interatomic potential parameters have been derived at simulated temperatures of 0 K and 300 K to model pyrite FeS2. The predicted pyrite structures are within 1% of those determined experimentally, while the calculated bulk modulus is within 7...

  10. Proving of Golden Pyrite (golden pyrite (Pyr-d. Patogenesia de Pirita dorada (pirita dorada (Pyr-d. Patogenesia de Pirita dorada (pirita dorada (Pyr-d.

    Directory of Open Access Journals (Sweden)

    Silvia Waisse Priven

    2003-01-01

    Full Text Available The results of the proving of Golden Pyrite are presented here. The proving followed the protocol adopted for Brosimum gaudichaudii, further modified to adjust to our group’s demands. They are also presented a thematic study of the remedy, its reportorial rubrics, its differential diagnosis and new rubrics that ought to be added to the repertory. The experience created the need of suggesting new practical guidelines to be included in the protocol.

  11. A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia

    Science.gov (United States)

    Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam

    2014-01-01

    The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into

  12. Morphology, origin and infrared microthermometry of fluid inclusions in pyrite from the Radka epithermal copper deposit, Srednogorie zone, Bulgaria

    Science.gov (United States)

    Kouzmanov, Kalin; Bailly, Laurent; Ramboz, Claire; Rouer, Olivier; Bény, Jean-Michel

    2002-08-01

    Pyrite samples from the Radka epithermal, replacement type, volcanic rock-hosted copper deposit, Bulgaria, have been studied using near-infrared (IR) microscopy. Two generations of pyrite based on their textures, composition and behaviour in IR light can be distinguished. Electron microprobe analyses, X-ray elemental mapping and Fourier transform infrared spectroscopy were used to study the relationship between crystal zoning, trace element contents and IR transmittance of pyrite. The observed crystal zoning is related to variable arsenic contents in massive fine-grained and colloform pyrite from the early pyrite-quartz assemblage, and cobalt contents in pyrite crystals from the late quartz-pyrite vein assemblage. There is a negative correlation between trace element content and IR transmittance of pyrite. The IR transparency of pyrite is thus a sensitive indicator of changes in trace element concentrations. Fluid inclusions have only been found in the second pyrite generation. Scanning electron microscopy observations on open fluid inclusion cavities permitted the crystallographic features of vacuoles to be determined. A characteristic feature of primary fluid inclusions in pyrite is a negative crystal habit, shaped mainly by {100}, {111} and {210}. This complicated polyhedral morphology is the reason for the observed opacity of some isometric primary inclusions. Secondary fluid inclusion morphology depends on the nature of the surface of the healed fracture. Recognition of the primary or secondary origin of fluid inclusions is enhanced by using crystallographically oriented sections. Microthermometric measurements of primary inclusions indicate that the second pyrite generation was deposited at maximum P-T conditions of 400 °C and 430 bar and from a fluid of low bulk salinity (3.5-4.6 wt%), possibly KCl-dominant. There are large ranges for homogenisation temperatures in secondary inclusions because of necking-down processes. Decrepitation features of some of

  13. Synchrotron Spectroscopic Studies of the Reaction of Cleaved Pyrite ( {FeS2}) Surfaces with Cr(VI) Solutions

    Science.gov (United States)

    Doyle, C. S.; Kendelewicz, T.; Bostick, B. C.; Brown, G. E.

    2002-12-01

    Pyrite is one of the most common sulfide ores, and the separation of valuable sulfide minerals from it has been an area of considerable interest for a long time. This extraction has led to a large quantity of pyrite waste, typically remaining in mine tailings piles which can interact with oxygen and surface water. The oxidation of pyrite under these conditions leads to the commonly known environmental problem of acid mine drainage, with acidification of surface waters, and the release of potentially toxic metals remaining within the pyrite matrix. A microscopic understanding of this oxidation process is extremely important and has been the aim of a number of studies. We apply the methods of synchrotron based surface science to this problem, utilizing surface sensitive photoemission and X-ray absorption spectroscopy to study the surface species present on the pyrite surface at the initial stages of oxidation. We have reacted pyrite surfaces with solutions containing chromate. Chromium exists in solution in two principal valence states, trivalent Cr(III) and hexavalent Cr(VI). Hexavalent chromium is itself considered an environmental problem due to its high toxicity and solubility, and thus mobility, whilst trivalent chromium is much less toxic and relatively insoluble. Hexavalent chromate is a strong oxidizing agent, and will react rapidly with the pyrite surface allowing the identification of oxidized iron and sulfur surface species. The possibility of using pyrite as a means of reducing chromate, and at the same time using chromate to passivate the pyrite surface to further oxidation through the buildup of a non-reactive iron-chromium (oxy)hydroxide layer will be investigated. The work was performed on rods cut from a natural pyrite single crystal from the Logroño region of Spain. The rods were then fractured over a reaction vessel, producing a fresh (100) surface for each experiment. The pyrite surfaces were reacted with 50 μM Cr(VI) solutions for 5 minutes at

  14. Pyritization processes and greigite formation in the advancing sulfidization front in the Upper Pleistocene sediments of the Black Sea

    DEFF Research Database (Denmark)

    Neretin, LN; Bottcher, ME; Jørgensen, BB

    2004-01-01

    Pyritization in late Pleistocene sediments of the Black Sea is driven by sulfide formed during anaerobic methane oxidation. A sulfidization front is formed by the opposing gradients of sulfide and dissolved iron. The sulfidization processes are controlled by the diffusion flux of sulfide from above...... and by the solid reactive iron content. Two processes of diffusion-limited pyrite formation were identified. The first process includes pyrite precipitation with the accumulation of iron sulfide precursors with the average chemical composition of FeSn (n = 1.10-1.29), including greigite. Elemental sulfur...... and polysulfides, formed from H,S by a reductive dissolution of Fe(Ill)-containing minerals, serve as intermediates to convert iron sulfides into pyrite. In the second process, a "direct" pyrite precipitation occurs through prolonged exposure of iron-containing minerals to dissolved sulfide. Methane-driven sulfate...

  15. Preparation of natural pyrite nanoparticles by high energy planetary ball milling as a nanocatalyst for heterogeneous Fenton process

    Energy Technology Data Exchange (ETDEWEB)

    Fathinia, Siavash [Department of Mining Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of); Fathinia, Mehrangiz [Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of); Rahmani, Ali Akbar [Department of Mining Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Khataee, Alireza, E-mail: a_khataee@tabrizu.ac.ir [Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2015-02-01

    Graphical abstract: - Highlights: • Pyrite nanoparticles were successfully produced by planetary ball milling process. • The physical and chemical properties of pyrite nanoparticles were fully examined. • The degradation of AO7 was notably enhanced by pyrite nanoparticles Fenton system. • The influences of basic operational parameters were investigated using CCD. - Abstract: In the present study pyrite nanoparticles were prepared by high energy mechanical ball milling utilizing a planetary ball mill. Various pyrite samples were produced by changing the milling time from 2 h to 6 h, in the constant milling speed of 320 rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM) linked with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis and Brunauer–Emmett–Teller (BET) were performed to explain the characteristics of primary (unmilled) and milled pyrite samples. The average particle size distribution of the produced pyrite during 6 h milling was found to be between 20 nm and 100 nm. The catalytic performance of the different pyrite samples was examined in the heterogeneous Fenton process for degradation of C.I. Acid Orange 7 (AO7) solution. Results showed that the decolorization efficiency of AO7 in the presence of 6 h-milled pyrite sample was the highest. The impact of key parameters on the degradation efficiency of AO7 by pyrite nanoparticles catalyzed Fenton process was modeled using central composite design (CCD). Accordingly, the maximum removal efficiency of 96.30% was achieved at initial AO7 concentration of 16 mg/L, H{sub 2}O{sub 2} concentration of 5 mmol/L, catalyst amount of 0.5 g/L and reaction time of 25 min.

  16. AN INNOVATIVE INTEGRATED APPROACH TO MINIMIZING GYPSUM AND PYRITE WASTES BY CONVERSION TO MARKETABLE PRODUCTS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel Tao

    2000-06-27

    The objective of this research program is to develop a novel integrated process to eliminate millions of tons of gypsum and pyrite wastes generated annually by the U.S. energy industries and reduce the emission of millions of tons of greenhouse gas carbon dioxide. This was accomplished by converting gypsum and pyrite wastes to marketable products such as lime, direct reduced iron (DRI), and sulfur products and obviating the need to calcine millions of tons of limestone for use in utility scrubbers. Specific objectives included: (1) Develop a novel, integrated process for utilizing two major wastes generated by mining and energy industries to produce lime for recycling and other marketable products. (2) Study individual chemical reactions involved in pyrite decomposition, DRI production, and Muller-Kuhne process for lime regeneration to determine optimum process variables such as temperature, time, and reactant composition. (3) Investigate techniques for effective concentration of pyrite from tailing waste and methods for effective separation of DRI from calcium sulfide.

  17. Pyrite nanoparticles as a Fenton-like reagent for in situ remediation of organic pollutants

    Directory of Open Access Journals (Sweden)

    Carolina Gil-Lozano

    2014-06-01

    Full Text Available The Fenton reaction is the most widely used advanced oxidation process (AOP for wastewater treatment. This study reports on the use of pyrite nanoparticles and microparticles as Fenton reagents for the oxidative degradation of copper phthalocyanine (CuPc as a representative contaminant. Upon oxidative dissolution in water, pyrite (FeS2 particles can generate H2O2 at their surface while simultaneously promoting recycling of Fe3+ into Fe2+ and vice versa. Pyrite nanoparticles were synthesized by the hot injection method. The use of a high concentration of precursors gave individual nanoparticles (diameter: 20 nm with broader crystallinity at the outer interfaces, providing a greater number of surface defects, which is advantageous for generating H2O2. Batch reactions were run to monitor the kinetics of CuPc degradation in real time and the amount of H2O2. A markedly greater degradation of CuPc was achieved with nanoparticles as compared to microparticles: at low loadings (0.08 mg/L and 20 h reaction time, the former enabled 60% CuPc removal, whereas the latter enabled only 7% removal. These results confirm that the use of low concentrations of synthetic nanoparticles can be a cost effective alternative to conventional Fenton procedures for use in wastewater treatment, avoiding the potential risks caused by the release of heavy metals upon dissolution of natural pyrites.

  18. Pyrite oxidation in saturated and Unsaturated Porous Media Flow: AComparison of alternative mathematical modeling approaches

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; White, Stephen P.; Pruess, Karsten

    1998-02-15

    Pyrite (FeS{sub 2}) is one of the most common naturally occurring minerals that is present in many subsurface environments. It plays an important role in the genesis of enriched ore deposits through weathering reactions, is the most abundant sulfide mineral in many mine tailings, and is the primary source of acid drainage from mines and waste rock piles. The pyrite oxidation reaction serves as a prototype for oxidative weathering processes with broad significance for geoscientific, engineering, and environmental applications. Mathematical modeling of these processes is extremely challenging because aqueous concentrations of key species vary over an enormous range, oxygen inventory and supply are typically small in comparison to pyrite inventory, and chemical reactions are complex, involving kinetic control and microbial catalysis. We present the mathematical formulation of a general multi-phase advective-diffusive reactive transport model for redox processes. Two alternative implementations were made in the TOUGHREACT and TOUGH2-CHEM simulation codes which use sequential iteration and simultaneous solution, respectively. The simulators are applied to reactive consumption of pyrite in (1) saturated flow of oxidizing water, and (2) saturated-unsaturated flow in which oxygen transport occurs in both aqueous and gas phases. Geochemical evolutions predicted from different process models are compared, and issues of numerical accuracy and efficiency are discussed.

  19. The Influence of Pyrite on the Solubility of Minjingu and Panda ...

    African Journals Online (AJOL)

    with pyrite also resulted into high amounts of A I and Mn being released in ... low P:S ratios this point was attained earlier than those with high P:S ratios. ..... tribution of ST AMICO staff who pro- ... maize- wheat rotation on submontarie soils.

  20. Comment on "Abiotic pyrite formation produces a large Fe isotope fractionation".

    Science.gov (United States)

    Czaja, Andrew D; Johnson, Clark M; Yamaguchi, Kosei E; Beard, Brian L

    2012-02-01

    Guilbaud et al. (Reports, 24 June 2011, p. 1548) suggest that the geologic record of Fe isotope fractionation can be explained by abiological precipitation of pyrite. We argue that a detailed understanding of the depositional setting, mineralogy, and geologic history of Precambrian sedimentary rocks indicates that the Fe isotope record dominantly reflects biological fractionations and Fe redox processes.

  1. Degradation of anthraquinone dye reactive blue 4 in pyrite ash catalyzed Fenton reaction.

    Science.gov (United States)

    Becelic-Tomin, Milena; Dalmacija, Bozo; Rajic, Ljiljana; Tomasevic, Dragana; Kerkez, Djurdja; Watson, Malcolm; Prica, Miljana

    2014-01-01

    Pyrite ash (PA) is created by burning pyrite in the chemical production of sulphuric acid. The high concentration of iron oxide, mostly hematite, present in pyrite ash, gives the basis for its application as a source of catalytic iron in a modified Fenton process for anthraquinone dye reactive blue 4 (RB4) degradation. The effect of various operating variables such as catalyst and oxidant concentration, initial pH and RB4 concentration on the abatement of total organic carbon, and dye has been assessed in this study. Here we show that degradation of RB4 in the modified Fenton reaction was efficient under the following conditions: pH=2.5; [PA]0=0.2 g L(-1); [H2O2]0=5 mM and initial RB4 concentration up to 100 mg L(-1). The pyrite ash Fenton reaction can overcome limitations observed from the classic Fenton reaction, such as the early termination of the Fenton reaction. Metal (Pb, Zn, and Cu) content of the solution after the process suggests that an additional treatment step is necessary to remove the remaining metals from the water. These results provide basic knowledge to better understand the modified, heterogeneous Fenton process and apply the PA Fenton reaction for the treatment of wastewaters which contains anthraquinone dyes.

  2. Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Lara, René H; García-Meza, J Viridiana; Cruz, Roel; Valdez-Pérez, Donato; González, Ignacio

    2012-08-01

    Massive pyrite (FeS₂) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)²⁻, S⁰). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S₂) to active sulfur species (e.g., Fe(1-x )S(2-y ), S⁰). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)²⁻/S⁰ speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)²⁻/S⁰ surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria.

  3. Pyrite-pyrrhotite intergrowths in calcite marble from Bistriški Vintgar, Slovenia

    Science.gov (United States)

    Zavašnik, J.

    2016-02-01

    Roman marble quarry in Bistrica gorge in southern Pohorje Mt. (north-eastern Slovenia) is situated in a 20 m thick lens of layered marble, at the contact zone between granodiorite and metamorphites. Grey and yellowish non-homogenous calcite marble is heavily included by mica, quartz, feldspars, zoisite, pyrite and amphiboles. In the present research, we have studied numerous pyrite (FeS2) crystals associated with yellowish-bronze non-stoichiometric pyrrhotite (Fe1-xS), not previously reported from this locality. SEM investigation revealed unusual sequence of crystallisation: primary skeletal pyrrhotite matrix is sparsely overgrown by well-crystalline pyrite, both being overgrown by smaller, well-developed hexagonal pyrrhotite crystals of the second generation. With TEM we identify the pyrrhotite as 5T-Fe1-xS phase, where x is about 0.1 and is equivalent to Fe9S10. The pyrite-pyrrhotite coexistence allows us a construction of fO2-pH diagram of stability fields, which reflects geochemical conditions at the time of marble re-crystallisation.

  4. Enhanced Photoresponse of FeS2 Films : The Role of Marcasite–Pyrite Phase Junctions

    NARCIS (Netherlands)

    Wu, Longfei; Dzade, N.Y.; Gao, L.; Scanlon, D. O.; Özturk, Zafer; Hollingsworth, N.; Weckhuysen, B.M.; Hensen, E. J. M.; de Leeuw, Nora H.; Hofmann, J. P.

    2016-01-01

    The beneficial role of marcasite in iron sulfide-based photo-electrochemical applications is reported for the first time. A spectacular improvement of the photoresponse observed experimentally for mixed pyrite/marcasite-FeS2 films can be ascribed to the presence of p/m phase junctions at the interfa

  5. Microbial Oxidation of Pyrite Coupled to Nitrate Reduction in Anoxic Groundwater Sediment

    DEFF Research Database (Denmark)

    Jørgensen, Christian Juncher; Elberling, Bo; Jacobsen, Ole Stig;

    2009-01-01

    denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can...

  6. Degradation of Anthraquinone Dye Reactive Blue 4 in Pyrite Ash Catalyzed Fenton Reaction

    Directory of Open Access Journals (Sweden)

    Milena Becelic-Tomin

    2014-01-01

    Full Text Available Pyrite ash (PA is created by burning pyrite in the chemical production of sulphuric acid. The high concentration of iron oxide, mostly hematite, present in pyrite ash, gives the basis for its application as a source of catalytic iron in a modified Fenton process for anthraquinone dye reactive blue 4 (RB4 degradation. The effect of various operating variables such as catalyst and oxidant concentration, initial pH and RB4 concentration on the abatement of total organic carbon, and dye has been assessed in this study. Here we show that degradation of RB4 in the modified Fenton reaction was efficient under the following conditions: pH=2.5; [PA]0=0.2 g L−1; [H2O2]0=5 mM and initial RB4 concentration up to 100 mg L−1. The pyrite ash Fenton reaction can overcome limitations observed from the classic Fenton reaction, such as the early termination of the Fenton reaction. Metal (Pb, Zn, and Cu content of the solution after the process suggests that an additional treatment step is necessary to remove the remaining metals from the water. These results provide basic knowledge to better understand the modified, heterogeneous Fenton process and apply the PA Fenton reaction for the treatment of wastewaters which contains anthraquinone dyes.

  7. Pyrite oxidation in unsaturated aquifer sediments. Reaction stoichiometry and rate of oxidation

    DEFF Research Database (Denmark)

    Andersen, Martin Søgaard; Larsen, Flemming; Postma, Diederik Jan

    2001-01-01

    the reaction stoichiometry and partitioning of gases between the solution and the gas phase. Pyrite oxidation with concurrent calcite dissolution was found to be consistent with the experimental data while organic carbon oxidation was not. The reaction involves changes in the total volume of the gas phase...

  8. Pyrite (FeS 2) oxidation: A sub-micron synchrotron investigation of the initial steps

    Science.gov (United States)

    Chandra, Anand P.; Gerson, Andrea R.

    2011-10-01

    Pyrite is an environmentally significant mineral being the major contributor to acid rock drainage. Synchrotron based SPEM (scanning photoelectron microscopy) and micro-XPS (X-ray photoelectron spectroscopy) have been used to characterise fresh and oxidised pyrite (FeS 2) with a view to understanding the initial oxidation steps that take place during natural weathering processes. Localised regions of the pyrite surface containing Fe species of reduced coordination have been found to play a critical role. Such sites not only initiate the oxidation process but also facilitate the formation of highly reactive hydroxyl radical species, which then lead the S oxidation process. Four different S species are found to be present on fresh fractured pyrite surfaces: S 22-(bulk) (4-fold coordination), S 22-(surface) (3-fold coordination), S 2- and S 0/S n2- (metal deficient sulfide and polysulfide respectively). These species were found to be heterogeneously distributed on the fractured pyrite surface. Both O 2 and H 2O gases are needed for effective oxidation of the pyrite surface. The process is initiated when O 2 dissociatively and H 2O molecularly adsorb onto the surface Fe sites where high dangling bond densities exist. H 2O may then dissociate to produce rad OH radicals. The adsorption of these species leads to the formation of Fe-oxy species prior to the formation of sulfoxy species. Evidence suggests that Fe-O bonds form prior to Fe-OH bonds. S oxidation occurs through interactions of rad OH radicals formed at the Fe sites, with formation of SO 42- occurring via S 2O 32-/SO 32- intermediates. The pyrite oxidation process is electrochemical in nature and was found to occur in patches, where site specific adsorption of O 2 and H 2O has occurred. Fe and S oxidation was found to occur within the same area of oxidation probably in atomic scale proximity. Furthermore, the O in SO 42- arises largely from H 2O; however, depending on the surface history, SO 42- formed early in

  9. Nanoscale analysis of pyritized microfossils reveals differential heterotrophic consumption in the ~1.9-Ga Gunflint chert.

    Science.gov (United States)

    Wacey, David; McLoughlin, Nicola; Kilburn, Matt R; Saunders, Martin; Cliff, John B; Kong, Charlie; Barley, Mark E; Brasier, Martin D

    2013-05-14

    The 1.88-Ga Gunflint biota is one of the most famous Precambrian microfossil lagerstätten and provides a key record of the biosphere at a time of changing oceanic redox structure and chemistry. Here, we report on pyritized replicas of the iconic autotrophic Gunflintia-Huroniospora microfossil assemblage from the Schreiber Locality, Canada, that help capture a view through multiple trophic levels in a Paleoproterozoic ecosystem. Nanoscale analysis of pyritic Gunflintia (sheaths) and Huroniospora (cysts) reveals differing relic carbon and nitrogen distributions caused by contrasting spectra of decay and pyritization between taxa, reflecting in part their primary organic compositions. In situ sulfur isotope measurements from individual microfossils (δ(34)S(V-CDT) +6.7‰ to +21.5‰) show that pyritization was mediated by sulfate-reducing microbes within sediment pore waters whose sulfate ion concentrations rapidly became depleted, owing to occlusion of pore space by coeval silicification. Three-dimensional nanotomography reveals additional pyritized biomaterial, including hollow, cellular epibionts and extracellular polymeric substances, showing a preference for attachment to Gunflintia over Huroniospora and interpreted as components of a saprophytic heterotrophic, decomposing community. This work also extends the record of remarkable biological preservation in pyrite back to the Paleoproterozoic and provides criteria to assess the authenticity of even older pyritized microstructures that may represent some of the earliest evidence for life on our planet.

  10. Attenuation of pyrite oxidation with a fly ash pre-barrier: Reactive transport modelling of column experiments

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, R.; Cama, J.; Nieto, J.M.; Ayora, C.; Saaltink, M.W. [University of Huelva, Huelva (Spain). Dept. of Geology

    2009-09-15

    Conventional permeable reactive barriers (PRBs) for passive treatment of groundwater contaminated by acid mine drainage (AMD) use limestone as reactive material that neutralizes water acidity. However, the limestone-alkalinity potential ceases as inevitable precipitation of secondary metal-phases on grain surfaces occurs, limiting its efficiency. In the present study, fly ash derived from coal combustion is investigated as an alternative alkalinity generating material for the passive treatment of AMD using solution-saturated column experiments. Unlike conventional systems, the utilization of fly ash in a pre-barrier to intercept the non-polluted recharge water before this water reacts with pyrite-rich wastes is proposed. Chemical variation in the columns was interpreted with the reactive transport code RETRASO. In parallel, kinetics of fly ash dissolution at alkaline pH were studied using flow-through experiments and incorporated into the model. In a saturated column filled solely with pyritic sludge-quartz sand (1: 10), oxidation took place at acidic conditions (pH 3.7). According to SO{sub 4}{sup 2-} release and pH, pyrite dissolution occurred favourably in the solution-saturated porous medium until dissolved O{sub 2} was totally consumed. In a second saturated column, pyrite oxidation took place at alkaline conditions (pH 10.45) as acidity was neutralized by fly ash dissolution in a previous level. At this pH Fe release from pyrite dissolution was immediately depleted as Fe-oxy(hydroxide) phases that precipitated on the pyrite grains, forming Fe-coatings (microencapsulation). With time, pyrite microencapsulation inhibited oxidation in practically 97% of the pyritic sludge. Rapid pyrite-surface passivation decreased its reactivity, preventing AMD production in the relatively short term.

  11. Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite

    Science.gov (United States)

    Sun, Fenglong

    The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by XANES/EXAFS, which could result in

  12. Existing forms of REE in gold-bearing pyrite of the Jinshan gold deposit,Jiangxi Province,China

    Institute of Scientific and Technical Information of China (English)

    毛光周; 华仁民; 高剑峰; 李伟强; 赵葵东; 龙光明; 陆慧娟

    2009-01-01

    Rare earth element(REE) is widely used in various fields of geology.Study of the existing forms of REE in geological objects is a necessity for us to solve geological problems related with REE.This paper tried to make it clear the existing forms of REE in gold-bearing pyrite in Jinshan gold deposit by stepwise dissolution test with ICP-MS analysis.Results showed that content of REE in fluid-inclusions of gold-bearing pyrite was very low,which only took about 0.07%-0.70% of the ΣREE,and that of pyrite phase ...

  13. The origin of copiapite from chlorite pyritic schist (Wiesciszowice, Lower Silesia, Poland) in the light of Moessbauer analysis

    Energy Technology Data Exchange (ETDEWEB)

    Adamczyk, Z., E-mail: zdzislaw.adamczyk@polsl.pl [Silesian University of Technology, Institute of Applied Geology (Poland); Komraus, J. L., E-mail: komraus@us.edu.pl [University of Silesia, Institute of Physics (Poland)

    2008-01-15

    This work presents the results of the analysis of copiapite, formed from weathering and oxidation of pyrite in pyritic schist from Wiesciszowice, Lower Silesia (Poland). The pure phase of copiapite was found in secondary minerals after pyrite and identified by optical microscopy, XRD and Moessbauer spectroscopy. In the analyzed copiapite major cations appear to be Fe{sup 2+} and Fe{sup 3+}. Some Fe{sup 3+} is substituted by other cations, mainly Al{sup 3+}. Al{sup 3+} probably comes from leaching of chlorite from which hydrated sulphates of iron, mainly szomolnokite, form followed by hydrated sulphates fibroferrite, which is replaced by copiapite.

  14. THE STUDY OF THE BASIC THEORY AND THE APPLICATION OF REMOVAL PYRITE AND ASH FROM FINE COAL WITH ELECTROSTATIC SEPARATOR

    Institute of Scientific and Technical Information of China (English)

    章新喜; 陈清加

    1996-01-01

    The effect of removing pyrite and ash from fine coal with electrostatic separator is determined by the electric property of coal, the distribution of corona ion and electrostatic field, and the disperse and even feed. The dielectric constant of coal and mineral matter is studied in this paper and the amendment has been made to survey theory. The oscillogram is adopted to study the distribution of corona ion and electrostatic field. The paper details the study of remoing pyrite and ash from fine coal, and the test results demonstrate the high efficiency of removing pyrite and ash with electrostatic separator.

  15. On the origin of framboidal pyrite in sediments of the Suakin Deep (Red Sea)Sur l'origine de la pyrite framboïdale dans les sédiments de la fosse Suakin (mer Rouge)

    Science.gov (United States)

    Pierret, Marie-Claire; Blanc, Gérard; Clauer, Norbert

    2000-01-01

    Suakin Deep is one of the southern depressions of the Red Sea, with sediments containing up to 20 % of pyrite. Although metalliferous sediments result from hydrothermal activity in most deeps, those of Suakin have different characteristics. Pyrite is framboïdal and the REE patterns of its sediments are similar to those of biodetrital sediments. The sediments seem to be of biodetritic origin and to have undergone diagenetic changes without hydrothermal activity.

  16. Biohydrometallurgical process to produce the coagulant ferric sulfate from the pyrite present in coal tailings

    Energy Technology Data Exchange (ETDEWEB)

    Colling, A.V.; Santos Menezes dos, J.C.S.; Silveira, P.S.; Schneider, I.A.H. [South Rio Grande Federal Univ., Porto Alegre (Brazil). Graduate Program in Mining, Metallurgical and Materials Technology Center

    2010-07-01

    This paper presented details of a biohydrometallurgical study conducted to characterize the production of a ferric sulfate coagulate from pyrite (FeS{sub 2}) contained in coal tailings. Leaching experiments were conducted with coal tailings samples from the Santa Catarina mining site in Brazil. The experiments were conducted for sterile and non-sterile samples, as well as samples inoculated with acidophilic bacteria and acidophilic bacteria with the addition of nutrients. Samples were collected weekly in order to analyze total iron, sulfate, and the amounts of Acidithiobacillus ferroxidans bacteria. An analysis of the samples showed that the pyrite oxidation, iron sulfate production, and quantities of bacteria were higher in the column inoculated with the bacteria and nutrient additions. The samples produced an aqueous solution that was rich in ferric sulfate. Water treatment tests demonstrated that the resulting coagulant is as efficient as conventionally-produced coagulants. 8 refs., 2 tab., 2 figs.

  17. Simulation of electrocatalytic hydrogen production by a bioinspired catalyst anchored to a pyrite electrode.

    Science.gov (United States)

    Zipoli, Federico; Car, Roberto; Cohen, Morrel H; Selloni, Annabella

    2010-06-30

    The possibility of using the active site, the [FeFe](H) cluster, of the bacterial di-iron hydrogenases as a catalyst for hydrogen production from water by electro- or photocatalysis is of current scientific and technological interest. We present here a theoretical study of hydrogen production by a modified [FeFe](H) cluster stably linked to a pyrite electrode immersed in acidified water. We employed state-of-the-art electronic-structure and first-principles molecular-dynamics methods. We found that a stable sulfur link of the cluster to the surface analogous to that linking the cluster to its enzyme environment cannot be made. However, we have discovered a modification of the cluster which does form a stable, tridentate link to the surface. The pyrite electrode readily produces hydrogen from acidified water when functionalized with the modified cluster, which remains stable throughout the hydrogen production cycle.

  18. Pyrite thermochemistry, ash agglomeration, and char fragmentation during pulverized coal combustion. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.; Diaz, R.; Niksa, S.

    1991-10-01

    The objective of the present work is to introduce an experimental program that will eventually lead to time-resolved iron ash composition over the technological operating domain. The preceding literature survey suggests two important stipulations on any such experimental program. The first stipulation is that good control must be established over the operating conditions, to accurately quantify their effects. The other is that data must be obtained rapidly, to thoroughly cover the important operating domain. This work presents a series of studies that has characterized the desulfurization of pyrite during the early stages of combustion. An experimental system was established and used to monitor the effects of oxygen, temperature, and residence time on the evolution of condensed phase products of the combustion of pure pyrite. (VC)

  19. Pyrite thermochemistry, ash agglomeration, and char fragmentation during pulverized coal combustion

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.; Diaz, R.; Niksa, S.

    1991-10-01

    The objective of the present work is to introduce an experimental program that will eventually lead to time-resolved iron ash composition over the technological operating domain. The preceding literature survey suggests two important stipulations on any such experimental program. The first stipulation is that good control must be established over the operating conditions, to accurately quantify their effects. The other is that data must be obtained rapidly, to thoroughly cover the important operating domain. This work presents a series of studies that has characterized the desulfurization of pyrite during the early stages of combustion. An experimental system was established and used to monitor the effects of oxygen, temperature, and residence time on the evolution of condensed phase products of the combustion of pure pyrite. (VC)

  20. Influences of silver sulfide on the bioleaching of chalcopyrite, pyrite and chalcopyrite-containing ore

    Institute of Scientific and Technical Information of China (English)

    胡岳华; 王军; 邱冠周; 王淀佐

    2002-01-01

    The effects of silver sulfide (Ag2S) on the bioleaching of chalcopyrite and pyrite were investigated in this paper. It has been shown that Ag2S enhanced the yields of bioleaching of chalcopyrite but inhibited the bio-oxidation of pyrite. The addition of Ag2S selectively increased the copper dissolution from the chalcopyrite-containing ores in shake flasks with a recovery of 85.3% compared with 24.3% without Ag2S, while slightly decreased the iron yields from 51% to 41.8%. The copper extraction of the chalcoopyrite-containing waste rock in column leaching charged with 18 kg mass increased up to 21.7% in the presence of Ag2S, while only 3.4% in the absence of the catalyst. The mechanism of Ag2S catalysis could be explained well by the "Mixed potential model".

  1. Preparation of Metallic Iron Powder from Pyrite Cinder by Carbothermic Reduction and Magnetic Separation

    Directory of Open Access Journals (Sweden)

    Hongming Long

    2016-04-01

    Full Text Available The reduction and magnetic separation procedure of pyrite cinder in the presence of a borax additive was performed for the preparation of reduced powder. The effects of borax dosage, reduction temperature, reduction time and grinding fineness were investigated. The results show that when pyrite cinder briquettes with 5% borax were pre-oxidized at 1050 °C for 10 min, and reduced at 1050 °C for 80 min, with the grinding fineness (<0.44 mm passing 81%, the iron recovery was 91.71% and the iron grade of the magnetic concentrate was 92.98%. In addition, the microstructures of the products were analyzed by optical microscope, scanning electron microscope (SEM, and mineralography, and the products were also studied by the X-ray powder diffraction technique (XRD to investigate the mechanism; the results show that the borax additive was approved as a good additive to improve the separation of iron and gangue.

  2. Factors Influencing Conversion of Pyritic Sulfur in Coal by Microwave Irradiation

    Institute of Scientific and Technical Information of China (English)

    SUI Jian-cai; XU Ming-hou; QIU Ji-hua; CHENG Rong

    2005-01-01

    The high sulfur coal from southwest of China was used to examine the influence of different factors such as irradiation time, particle size of coal, and leachant (Na2CO3, NaOH and CuCl2.2H2O)on the conversion rate of pyrite to pyrrhotite by microwave irradiation. Single factor experiment was performed firstly, then orthogonal test method was used to explore these factors. The result shows that the optimal treating conditions for the conversion are a treatment time of 3 min, a particle size from 0.086 mm to 0.102 mm, and a favorable leachant of sodium hydroxide. Under these conditions the conversion rate of pyrite can reach 45.7 %.

  3. Preparation of solid polyferric sulfate from pyrite cinders and its structure feature

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 龚竹青; 陈白珍; 刘立华

    2003-01-01

    Acid leaching solution was obtained after mixing pyrite cinders with H2SO4, then heating the mixture of pyrite cinders and H2SO4 at 200-300 ℃, leaching the heated mixture with water and filtrating. Polyferric sulfate (PFS) solution was produced by adding suitable amounts of FeSO4*7H2O and NaClO3 into acid leaching solution. By concentrating and drying PFS solution, solid PFS with alkali degree of 6.40%-22.4% was prepared. Fe4.67(SO4)6(OH)2*20H2O in the solid PFS was discovered by XRD analysis. FT-IR spectroscopy shows that the absorption peaks at 3 400 cm-1 and 1 635 cm-1 arise from OH and absorption peaks at 998 cm-1 and 669 cm-1 come from Fe-OH in the solid PFS.

  4. Comparisons of species and coagulation effects of PFS solution and solid PFS from pyrite cinders

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 龚竹青; 刘立华; 陈白珍

    2002-01-01

    Pyrite cinder is a kind of solid waste of sulfuric acid industry. After mixing pyrite cinders with sulfuric acid, ferric sulfate was obtained by heating, maturing, dissolving and filtrating. Suitable amounts of FeSO4 * 7H2O and NaClO3 were added into ferric sulfate solution and polyferric sulfate(PFS) solution was produced. Solid PFS was made by concentrating and drying PFS solution. Time-dependent complex colorimetric tests were done while ferron agent reacted with Fe3+ in the solution. The results show that the proportion of transitional low polymeric species and high polymeric species are increased after PFS solution is transferred into solid PFS. It was discovered by jar tests that solid PFS has very good coagulation effects relevant to the increase of transitional lower polymeric species.

  5. Pyrite oxidation in the presence of hematite and alumina: I. Batch leaching experiments and kinetic modeling calculations.

    Science.gov (United States)

    Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi

    2017-02-15

    Pyrite is one of the most common and geochemically important sulfide minerals in nature because of its role in the redox recycling of iron (Fe). It is also the primary cause of acid mine drainage (AMD) that is considered as a serious and widespread problem facing the mining and mineral processing industries. In the environment, pyrite oxidation occurs in the presence of ubiquitous metal oxides, but the roles that they play in this process remain largely unknown. This study evaluates the effects of hematite (α-Fe2O3) and alumina (α-Al2O3) on pyrite oxidation by batch-reactor type experiments, surface-sensitive characterization of the oxidation layer and thermodynamic/kinetic modeling calculations. In the presence of hematite, dissolved sulfur (S) concentration dramatically decreased independent of the pH, and the formation of intermediate sulfoxy anionic species on the surface of pyrite was retarded. These results indicate that hematite minimized the overall extent of pyrite oxidation, but the kinetic model could not explain how this suppression occurred. In contrast, pyrite oxidation was enhanced in the alumina suspension as suggested by the higher dissolved S concentration and stronger infrared (IR) absorption bands of surface-bound oxidation products. Based on the kinetic model, alumina enhanced the oxidative dissolution of pyrite because of its strong acid buffering capacity, which increased the suspension pH. The higher pH values increased the oxidation of Fe(2+) to Fe(3+) by dissolved O2 (DO) that enhanced the overall oxidative dissolution kinetics of pyrite. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. High-resolution (SIMS) versus bulk sulfur isotope patterns of pyrite in Proterozoic microbialites with diverse mat textures

    Science.gov (United States)

    Gomes, M. L.; Fike, D. A.; Bergmann, K.; Knoll, A. H.

    2015-12-01

    Sulfur (S) isotope signatures of sedimentary pyrite preserved in marine rocks provide a rich suite of information about changes in biogeochemical cycling associated with the evolution of microbial metabolisms and oxygenation of Earth surface environments. Conventionally, these S isotope records are based on bulk rock measurements. Yet, in modern microbial mat environments, S isotope compositions of sulfide can vary by up to 40‰ over a spatial range of ~ 1 mm. Similar ranges of S isotope variability have been found in Archean pyrite grains using both Secondary Ion Mass Spectrometry and other micro-analytical techniques. These micron-scale patterns have been linked to changes in rates of microbial sulfate reduction and/or sulfide oxidation, isotopic distillation of the sulfate reservoir due to microbial sulfate reduction, and post-depositional alteration. Fine-scale mapping of S isotope compositions of pyrite can thus be used to differentiate primary environmental signals from post-depositional overprinting - improving our understanding of both. Here, we examine micron-scale S isotope patterns of pyrite in microbialites from the Mesoproterozoic-Neoproterozoic Sukhaya Tunguska Formation and Neoproterozoic Draken Formation in order to explore S isotope variability associated with different mat textures and pyrite grain morphologies. A primary goal is to link modern observations of how sulfide spatial isotope distributions reflect active microbial communities present at given depths in the mats to ancient processes driving fine-sale pyrite variability in microbialites. We find large (up to 60‰) S isotope variability within a spatial range of less than 2.5cm. The micron-scale S isotope measurements converge around the S isotope composition of pyrite extracted from bulk samples of the same microbialites. These micron-scale pyrite S isotope patterns have the potential to reveal important information about ancient biogeochemical cycling in Proterozoic mat environments

  7. Dependence of reaction rate of pyrite oxidation on temperature, pH and oxidant concentration

    Institute of Scientific and Technical Information of China (English)

    LU; Long; WANG; Rucheng; XUE; Jiyue; CHEN; Fanrong; CHEN; J

    2005-01-01

    The kinetic sstudy of pyrite oxidation was performed in a series of experiments by a mixed flow reactor. The release rates of Fe(II) are in the order of 3.22×10-9-5.51×10-7 mol·m-2·s-1 at temperature (T ) 25 to 44℃, initial pH (pH )1.4 to 2.7, and initial Fe(III) concentration ([Fe(III)]I) 10-5 to 5×10-3 mol·kg-1. The release rate of Fe(II) increased with increasing T or/and pH or/and [Fe(III)]I in the above range. The rate law and activation energy of pyrite oxidation were derived by statistical analyses of Rfe(II) vs. [Fe(III)]I, Rfe(II) vs. pH and Rfe(II) vs. T, and are given as (1) Rate law: Rfe(II)=104.65e-64.54×103/8.31T[Fe(III)]i0.6./[H+]0.45 ; (2) activation energy: 64.54 ( 8.07 kJ·mol-1. The expression can be applied to more cases (e.g., quantifying the pollutant released from sulfide-rich mining waste and assessing reliable performance of underground repository sites where pyrite acts as an engineered barrier material). Using the rate law derived from this study, the magnitude of the pollutants transferred to secondary phases, soil and water from oxidized pyrite during Jiguanshan mine waste weathering was preliminarily estimated. The estimated magnitude is very high, suggesting that the pile has possibly posed significant impact on the water quality in this region.

  8. Pyrite as a proxy for the identification of former coastal lagoons in semiarid NE Brazil

    Science.gov (United States)

    Ferreira, Tiago O.; Nóbrega, Gabriel N.; Albuquerque, Antonia G. B. M.; Sartor, Lucas R.; Gomes, Irlene S.; Artur, Adriana G.; Otero, Xosé L.

    2015-10-01

    This work aimed to test the suitability of pyrite (FeS2) as a proxy for reconstructing past marine environmental conditions along the semiarid coast of Brazil. Morphological description combined with physicochemical analyses including Fe partitioning were conducted for soil depth profiles (30 and 60 cm depths) at three sites in two contrasting lagoons of the state of Ceará: a suspected former lagoon that would have been transformed into a freshwater "lake" at a site vegetated by Juncus effusus (site P1), and another lagoon with connection to the sea at sites vegetated by J. effusus (site P2) or Portulaca oleracea (site P3). Soil samples were collected in September 2010. Site P3 had more reducing conditions, reaching Eh values of -132 mV in the surface layer (0-10 cm), whereas minimum values for the P1 and P2 sites were +219 and +85 mV, respectively. Lower pyritic Fe values were found at site P1, with a degree of pyritization (DOP) ranging from 10 to 13%. At sites P2 and P3, DOP ranged from 9 to 67% and from 55 to 72%, respectively. These results are consistent with an interruption of tidal channels by eolian dune migration inducing strong changes in the hydrodynamics and physicochemical characteristics (lower salinity, oxidizing conditions) of these sites, causing the dieback of suspected former mangroves and a succession to freshwater marshes with an intermediate salt marsh stage. Together with other physicochemical signatures, pyrite can evidently serve as a useful proxy in tracking environmental changes in such ecotones, with implications for coastal management.

  9. Mineral chemistry and isotope geochemistry of pyrite from the Heilangou gold deposit, Jiaodong Peninsula, Eastern China

    Institute of Scientific and Technical Information of China (English)

    Yutong Yan; Na Zhang; Shengrong Li; Yongsheng Li

    2014-01-01

    The Heilangou gold deposit is located in the northern QixiaePenglai gold belt, which is one amongst the three large gold belts in the eastern Shandong Province (Jiaodong Peninsula). The ore body has formed within the Guojialing granite. In this study, we report the mineral chemistry of pyrite, as well as the S, Pb, and HeO isotope data of the Heilangou gold deposit. The chemical composition of pyrite in the Heilangou gold deposit indicates that the associated gold deposit is a typical magmatic hydrothermal one. The geochemical signatures and crystal structure of pyrite show that the ore-forming materials have been derived from the crust. The S isotope data of the pyrites from Heilangou show an overall range from 5.5 to 7.8&and an average of 6.7&. The S isotope data in this deposit are similar to those from the deposits in the Jiaodong gold belt. The Pb and S isotope variations are small in the Heilangou gold deposit. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios are 17.4653e17.5958, 15.5105e15.5746 and 38.0749e38.4361, respec-tively. These data plot between the lower crust and the orogenic belt. The Pb isotope data in the Heilangou gold deposit are similar to those in the Linglong gold deposit. From the Qixia gold area (the Liukou and Majiayao gold deposits) to the MupingeRushan gold belt (Rushan gold deposit) to the ZhaoeYe gold belt (the Linglong, Sanshandao and Jiaojia gold deposits), the 206Pb/204Pb ratios progressively increase. The DeO isotope data obtained from quartz separates suggest that the ore-forming fluid was similar to a mixture of magmatic and meteoric waters. These results suggest that the ore-forming elements were primarily from source fluids derived from the lower crust.

  10. Equation of state of pyrite to 85 GPa and 2400 K

    Science.gov (United States)

    Thompson, E. C.; Chidester, B.; Campbell, A. J.; Prakapenka, V.

    2014-12-01

    Pyrite (FeS2), a Pa3 space group non-magnetic semiconductor, is the most abundant iron sulfide in nature, yet the high cosmic abundance of sulfur is not reflected in the terrestrial crust, implying it is either sequestered in the Earth's interior or was volatilized during accretion. As it has widely been suggested that sulfur could be one of the contributing light elements leading to the density deficit of Earth's core, a robust thermal equation of state of FeS2 is vital for understanding the evolution and properties of Earth's interior. We performed X-ray diffraction measurements on FeS2 at the GSECARS sector 13-ID-D and HPCAT sector 16-ID-B beamlines at the Advanced Photon Source. Pressures from 17 to 85 GPa and temperatures up to 2400 K were achieved using laser-heated diamond anvil cells. Pressures were determined from the lattice parameters of KBr [1], which served as an insulator and pressure medium, and temperatures were determined by spectroradiometry. No phase transitions were observed in the pyrite structure over the pressure and temperature ranges investigated. By combining our new P-V-T data with previously published room temperature compression data [2], we have determined a thermal equation of state for FeS2, with bulk modulus K=182.6(74) GPa, pressure derivative K'=3.82(25), and αKT=0.00329(45). Our revised equation of state for pyrite is consistent with a core density deficit satisfied by 9-10 wt.% sulfur. We compare these findings to previously published ab intio equation of state parameters for pyrite under a similar range of pressures [3]. [1] Fischer et al. (2012) EPSL 357-358, 268-276. [2] Merkel et al. (2002) PCM 29, 1-9. [3] Le Page and Rodgers (2005) PCM 32, 564-567.

  11. Arsenopyrite and pyrite bioleaching: evidence from XPS, XRD and ICP techniques.

    Science.gov (United States)

    Fantauzzi, Marzia; Licheri, Cristina; Atzei, Davide; Loi, Giovanni; Elsener, Bernhard; Rossi, Giovanni; Rossi, Antonella

    2011-10-01

    In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite (FeS(2)) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved. The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching, no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate of the leaching process and precipitated secondary phases (Fe-OOH and jarosite), together with adsorbed arsenates, was detected. Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces, of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action.

  12. Further studies of the effects of oxidation on the surface properties of coal and coal pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, Miguel Nicolas [Univ. of California, Berkeley, CA (United States)

    1994-01-01

    The objective of this research was to investigate the oxidation behavior of coal and coal pyrite and to correlate the changes in the surface properties induced by oxidation, along with the intrinsic physical and chemical properties of these organic and inorganic materials, with the behavior in physical coal cleaning processes. This provide more fundamental knowledge for understanding the way in which different factors interact in a medium as heterogeneous as coal. Fourteen coal samples of different ranks ranging from high to medium sulfur content were studied by dry oxidation tests at different temperatures and humidities, and by wet oxidation tests using different oxidizing agents. The concentration of surface oxygen functional groups was determined by ion-exchange methods. The changes in the coal composition with oxidation were analyzed by spectroscopic techniques. The wettability of as-received and oxidized coal and coal pyrite samples was assessed by film flotation tests. The electrokinetic behavior of different coals and coal pyrite samples was studied by electrokinetic tests using electrophoresis. Possible oxidation mechanisms have been proposed to explain the changes on the coal surface induced by different oxidation treatments.

  13. Selective Sulfidation of Lead Smelter Slag with Pyrite and Flotation Behavior of Synthetic ZnS

    Science.gov (United States)

    Han, Junwei; Liu, Wei; Wang, Dawei; Jiao, Fen; Zhang, Tianfu; Qin, Wenqing

    2016-08-01

    The selective sulfidation of lead smelter slag with pyrite in the presence of carbon and Na salts, and the flotation behavior of synthetic ZnS were studied. The effects of temperature, time, pyrite dosage, Na salts, and carbon additions were investigated based on thermodynamic calculation, and correspondingly, the growth mechanism of ZnS particles was studied at high temperatures. The results indicated that the zinc in lead smelter slag was selectively converted into zinc sulfides by sulfidation roasting. The sulfidation degree of zinc was increased until the temperature, time, pyrite, and carbon dosages reached their optimum values, under which it was more than 95 pct. The growth of ZnS particles largely depended upon roasting temperature, and the ZnS grains were significantly increased above 1373 K (1100 °C) due to the formation of a liquid phase. After the roasting, the zinc sulfides generated had a good floatability, and 88.34 pct of zinc was recovered by conventional flotation.

  14. Further studies of the effects of oxidation on the surface properties of coal and coal pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, M.N.

    1994-12-31

    The objective of this research was to investigate the oxidation behavior of coal and coal pyrite and to correlate the changes in the surface properties induced by oxidation, along with the intrinsic physical and chemical properties of these organic and inorganic materials, with the behavior in physical coal cleaning processes. This provide more fundamental knowledge for understanding the way in which different factors interact in a medium as heterogeneous as coal. Fourteen coal samples of different ranks ranging from high to medium sulfur content were studied by dry oxidation tests at different temperatures and humidities, and by wet oxidation tests using different oxidizing agents. The concentration of surface oxygen functional groups was determined by ion-exchange methods. The changes in the coal composition with oxidation were analyzed by spectroscopic techniques. The wettability of as-received and oxidized coal and coal pyrite samples was assessed by film flotation tests. The electrokinetic behavior of different coals and coal pyrite samples was studied by electrokinetic tests using electrophoresis. Possible oxidation mechanisms have been proposed to explain the changes on the coal surface induced by different oxidation treatments.

  15. Bio-decomposition of rock phosphate containing pyrites by Acidithiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    CHI Ru-an; XIAO Chun-qiao; HUANG Xiao-hui; WANG Cun-wen; WU Yuan-xin

    2007-01-01

    Leaching soluble phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans (A. f) is feasible,and the reaction mechanism is as follows. Pyrites are oxidized by A. f. to produce H2SO4 and FeSO4; the rock phosphate is decomposed by H2SO4, forming soluble phosphorus compounds; and Fe2+ from FeSO4 is oxidized to Fe3+, providing energy for the growth of A. f.. In this process, as H2SO4 is produced in the reaction, an acidic condition in the culture medium is formed, which benefits the growth of A. f. and aids both continuous oxidation of pyrites and leaching of soluble phosphorus from rock phosphate.The fraction of phosphorous leached can reach the largest in the presence of 1.0 g/L Fe3+, 200 mg/L Mg2+ and 400 mg/L NH4+. The optimal technological parameters on the fraction of phosphorous leached are as follows: the volume fraction of inocula of A. f, the

  16. Biogeochemical processes governing natural pyrite oxidation and release of acid metalliferous drainage.

    Science.gov (United States)

    Chen, Ya-ting; Li, Jin-tian; Chen, Lin-xing; Hua, Zheng-shuang; Huang, Li-nan; Liu, Jun; Xu, Bi-bo; Liao, Bin; Shu, Wen-sheng

    2014-05-20

    The oxidative dissolution of sulfide minerals (principally pyrite) is responsible for the majority of acid metalliferous drainage from mine sites, which represents a significant environmental problem worldwide. Understanding the complex biogeochemical processes governing natural pyrite oxidation is critical not only for solving this problem but also for understanding the industrial bioleaching of sulfide minerals. To this end, we conducted a simulated experiment of natural pyrite oxidative dissolution. Pyrosequencing analysis of the microbial community revealed a distinct succession across three stages. At the early stage, a newly proposed genus, Tumebacillus (which can use sodium thiosulfate and sulfite as the sole electron donors), dominated the microbial community. At the midstage, Alicyclobacillus (the fifth most abundant genus at the early stage) became the most dominant genus, whereas Tumebacillus was still ranked as the second most abundant. At the final stage, the microbial community was dominated by Ferroplasma (the tenth most abundant genus at the early stage). Our geochemical and mineralogical analyses indicated that exchangeable heavy metals increased as the oxidation progressed and that some secondary sulfate minerals (including jarosite and magnesiocopiapite) were formed at the final stage of the oxidation sequence. Additionally, we propose a comprehensive model of biogeochemical processes governing the oxidation of sulfide minerals.

  17. Matrix composition and community structure analysis of a novel bacterial pyrite leaching community.

    Science.gov (United States)

    Ziegler, Sibylle; Ackermann, Sonia; Majzlan, Juraj; Gescher, Johannes

    2009-09-01

    Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS(2)) oxidation. This community grows in stalactite-like structures--snottites--on the ceiling of an abandoned pyrite mine at pH values of 2.2-2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro-X-ray diffraction analysis showed that jarosite [(K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6)] is the major mineral embedded in the snottites. X-ray absorption near-edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self-contained consortium of bacterial species fuelled by the decomposition of pyrite.

  18. Hydrothermal vents as a source of pyrite and trace metal- containing mineral nanoparticles to the ocean

    Science.gov (United States)

    Gartman, A.; Yucel, M.; Luther, G. W.

    2012-12-01

    The pathways by which metals from hydrothermal vents may be transported through the ocean are still largely unknown. We demonstrate that pyrite nanoparticles as small as 4nm aggregate into nanoframboids of 50-350nm and are emitted from high temperature black smokers from vents at Lau Basin and the East Pacific Rise. These nanoparticles, which contain other metals including copper, are characterized via chemical methods as well as by using a combination of physical chemical techniques (TEM, SEM-EDS and EELS). Data indicate that the metal sulfide nanoparticles from Lau Basin, a back arc basin and EPR 9N, a fast spreading mid ocean ridge, have similar morphology. We report that laboratory hydrothermal syntheses can reproduce the size and morphology of the natural pyrite nanoparticles. Laboratory oxidation experiments show that these synthesized pyrite nanoparticles are stable in oxic seawater for months, and thus provide a potential transport mechanism for iron far from vent sources. These nanoparticles as well as others including iron silicates, which have also been identified, likely influence the transport of iron and other elements from the hydrothermal environment to the ocean. Hydrothermal vents serve as nanoparticle 'factories' that fertilize the ocean with metals that are important in a variety of biogeochemical processes.

  19. Synthesis and adsorption/photocatalysis performance of pyrite FeS2

    Science.gov (United States)

    Liu, Shuling; Li, Miaomiao; Li, Shu; Li, Honglin; Yan, Lu

    2013-03-01

    FeS2 crystallites were synthesized successfully via a solvothermal method, using potassium ferrocyanide K4[Fe(CN)6]·3H2O as Fe source, sulfur powder as S source in the presence of polyvinyl pyrrolidone (PVP) as dispersant. And potassium carbonate provided an alkaline environment. The phase and morphology of the products were characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the temperature and solvent ratio (V:VO) play a crucial role in the formation of FeS2 with a cubic phase structure (pyrite). Then based on a series of experiments, the possible formation mechanism of pyrite FeS2 crystallites was proposed. In addition, research also showed that the as-prepared pyrite FeS2 crystallites could high-efficiently absorb or photocatalytically degrade some organic dyes such as Methylene blue (MB), Safranine T, Methyl orange (MO), Rhodamine B (Rh B) and Pyronine B. Furthermore, the adsorption and photocatalytic degradation abilities of FeS2 for organic dyes were also compared.

  20. Copper and cobalt recovery from pyrite ashes of a sulphuric acid plant.

    Science.gov (United States)

    Erust, Ceren; Akcil, Ata

    2016-06-01

    The pyrite ashes formed as waste material during the calcination of concentrated pyrite ore used for producing sulphuric acid not only has a high iron content but also contains economically valuable metals. These wastes, which are currently landfilled or dumped into the sea, cause serious land and environmental pollution problems owing to the release of acids and toxic substances. In this study, physical (sulphation roasting) and hydrometallurgical methods were evaluated for their efficacy to recover non-iron metals with a high content in the pyrite ashes and to prevent pollution thereby. The preliminary enrichment tests performed via sulphation roasting were conducted at different roasting temperatures and with different acid amounts. The leaching tests investigated the impact of the variables, including different solvents, acid concentrations and leach temperatures on the copper and cobalt leaching efficiency. The experimental studies indicated that the pre-enrichment via sulphation roasting method has an effect on the leaching efficiencies of copper and cobalt, and that approximate recoveries of 80% copper and 70% cobalt were achieved in the H2O2-added H2SO4 leaching tests.

  1. Biogeneration of iron-based catalyst precursors by Acidianus brierleyi on high- and low-pyrite coals for direct liquefaction.

    Energy Technology Data Exchange (ETDEWEB)

    Murty, M.V.S.; Huggins, F.E.; Aleem, M.I.H.; Kermode, R.I.; Bhattacharyya, D. [University of Kentucky, Lexington, KY (United States). Dept. of Chemical Engineering

    1995-03-01

    Treatment of high-pyrite, high-sulphur Illinois (IBS) coals and pyrite-free Blind Canyon (DECS) coal with added pyrite in the presence of {ital Acidianus brierleyi} showed formation of iron oxyhydroxide (FeOOH) particles and subsequent sulphiding caused enhancement in liquefaction and oil yield. IBC No. 101 and 105, and DECS No. 17 containing different amounts of pyrite were treated with {ital A. brierleyi} to evaluate its effect on FeOOH formation. Chemical analysis of the liquid phase and Moessbauer analysis of the coals revealed that all the biotreated coals showed significant reduction in pyrite after 21 days (or less with pH alteration in the middle of IBC No. 105 coal run) of incubation. Further data on bioprocessed coals obtained from Moessbauer spectroscopy verified the formation of an FeOOH phase, which acts as a catalyst precursor for direct coal liquefaction (DCL). The direct liquefaction conversion and oil yield of the biotreated DECS No. 17 coal with added pyrite increased by 14 and 5% respectively, over the control which did not contain {ital A. brierleyi}. 40 refs., 8 figs., 2 tabs.

  2. Sulfur amino acids and alanine on pyrite (100) by X-ray photoemission spectroscopy: Surface or molecular role?

    Science.gov (United States)

    Sanchez-Arenillas, M.; Galvez-Martinez, S.; Mateo-Marti, E.

    2017-08-01

    This paper describes the first successful adsorption of the cysteine, cystine, methionine and alanine amino acids on the pyrite (100) surface under ultra-high vacuum conditions with crucial chemical adsorption parameters driving the process. We have demonstrated by X-ray photoemission spectroscopy (XPS) that the surface pretreatment annealing process on pyrite surfaces is a critical parameter driving surface reactivity. The presence of enriched monosulfide species on the pyrite (100) surface favours the amino acid NH2 chemical form, whereas a longer annealing surface pretreatment of over 3 h repairs the sulfur vacancies in the pyrite, enriching disulfide species on the pyrite surface, which promotes NH3+ adsorption due to the sulfur vacancies in the pyrite being replaced by sulfur atom dimers (S22-) on the surface. Furthermore, even if the surface chemistry (monosulfide or disulfide species enrichment) is the main factor promoting a partial conversion from NH2 to NH3+ species, the unique chemical structure of each amino acid provides a particular fingerprint in the process.

  3. A silica/fly ash-based technology for controlling pyrite oxidation. Semi-annual, March 1, 1996 - August 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Evangelou, V.P. [USDOE Pittsburgh Energy Technology Center, PA (United States)

    1996-12-31

    The overall objective is to develop methodologies by which metasilicate or fly ash may produce an effective coating on pyrite surfaces for inhibiting pyrite oxidation. During the past six months, the investigators produced wet chemistry evidence demonstrating that pyrite-HCO{sub 3} complexes promote pyrite oxidation. This is an important finding for their over all strategy in controlling pyrite oxidation because it suggests that pyrite microencapsulation is important in order to control oxidation in near cirumneutral pH environments produced by addition of alkaline material, e.g., fly ash. In their previous studies, the investigators reported that pyrite microencapsulation could be carried out by reacting pyrite with a pH buffered solution and in the presence of metasilicate. The coating formed on the surface of pyrite appeared to be an amorphous iron-oxide-silicate material which inhibited pyrite oxidation. During this past six months, the investigators evaluated: the molecular mechanisms of silicate adsorption by iron oxide; the effects of silicate on the bulk and surface properties of iron oxides; and the effect of silicate on metal-cation adsorption properties by iron oxides.

  4. Geochemistry of Early Frasnian (Late Devonian) pyrite-ammonoid level in the Kostomłoty Basin, Poland, and a new proxy parameter for assessing the relative amount of syngenetic and diagenetic pyrite

    Science.gov (United States)

    Pisarzowska, Agnieszka; Berner, Zsolt A.; Racki, Grzegorz

    2014-07-01

    Pyrite geochemistry (isotope and trace element composition, degree of pyritization, S/Corg ratio) was used in context of selected lithogeochemical parameters (major and trace elements, including sulphur, organic carbon, and δ13C of carbonate carbon) to constrain fluctuations in depositional conditions during the Early to Middle Frasnian carbon isotopic perturbation (punctata Event) in the Kostomłoty Basin, Poland. Based on the ratio between the sum of oxyanionic elements and transition metals in pyrite, a new proxy parameter (index of syngenetic pyrite, ISYP) is proposed for assessing the relative amount of syngenetic pyrite in a sample. The distribution of the ISYP along the Kostomłoty - Małe Górki section (upper Szydłówek to the basal Kostomłoty beds) is in concert with conclusions inferred from paleoecologic data and other geochemical parameters (degree of pyritization, S/Corg, δ34Spyrite). According to these, the lower segment of the Szydłówek Beds was deposited in a normally oxygenated environment, but undergoing increasing primary productivity in surface water, as indicated by an increase in δ13Ccarb and in Cu/Zr ratio in bulk rock, which triggered the periodic deposition of sediments slightly enriched in organic matter, notably within the pyrite-ammonoid level (= Goniatite Level). Fluctuating, but in general high S/Corg ratios, DOPR values and ISYP values suggest that during this time - against the background of a generally dysoxic environment - shorter or longer lasting episodes of more restricted (anoxic and possibly even euxinic) bottom water conditions developed. Low sedimentation rates enabled a continuous and practically unlimited supply of sulphate during bacterial sulphate reduction (BSR), which in turn led to a strong depletion of pyrite sulphur in 34S in this interval (constantly around -29‰). In contrast, below and above the Goniatite Level, higher δ34S values (up to + 3‰), are compatible with closed system conditions and higher

  5. Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States

    Science.gov (United States)

    Vikre, P.G.; Poulson, S.R.; Koenig, A.E.

    2011-01-01

    The thick (???8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high d34S values (-11.6 to 40.8%, derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( 207Pb/204Pb derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources. In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in

  6. Pyrite deformation and connections to gold mobility: insight from micro-structural analysis and trace element mapping

    Science.gov (United States)

    Dubosq, Renelle; Rogowitz, Anna; Lawley, Christopher; Schneider, David; Jackson, Simon

    2017-04-01

    Pyrite is an important and ubiquitous gold-bearing phase in many orogenic gold deposits making the study of its deformation behaviour under metamorphic conditions crucial to the understanding of gold (re)mobilization. However, pyrite deformation mechanisms and their influence on the retention or release of trace elements during deformation and metamorphism remain poorly understood. We propose a syn- to post-peak metamorphic and deformation driven gold upgrading model where gold is remobilized through deformation-induced diffusion pathways in the form of substructures in pyrite. The middle amphibolite facies assemblage (actinolite-biotite-plagioclase-almandine) of the Detour Lake deposit (Canada) makes it an ideal study area due to maximum temperatures reaching 550°C, exceeding the conditions for plastic deformation in pyrite (450°C). The world-class Detour Lake deposit, containing 16.4 Moz of Au at 1 g/t, is a Neoarchean orogenic gold ore body located in the northern Abitibi district within the Superior Province. The mine is situated along the high strain, sub-vertical ductile-brittle Sunday Lake Deformation Zone (SLDZ) parallel to the broadly E-W trending Abitibi greenstone belt. Herein we combine orientation contrast (OC) forescatter imaging, electron backscatter diffraction (EBSD) and 2D laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element pyrite mapping to evaluate the influence of pyrite brittle and plastic deformation on the release of trace elements during syn-metamorphic gold remobilization. Local misorientation patterns in pyrite exhibit parallel bands that can be described by continuous rotation around one of the axes, whereas higher strain areas reveal more heterogeneous misorientation patterns and the development of low-angle grain boundaries with late fractures indicative of dislocation creep and strain hardening. These late fractures are an important micro-structural setting for gold and clusters of precious

  7. Gold and trace element zonation in pyrite using a laser imaging technique: Implications for the timing of gold in orogenic and carlin-style sediment-hosted deposits

    Science.gov (United States)

    Large, R.R.; Danyushevsky, L.; Hollit, C.; Maslennikov, V.; Meffre, S.; Gilbert, S.; Bull, S.; Scott, R.; Emsbo, P.; Thomas, H.; Singh, B.; Foster, J.

    2009-01-01

    Laser ablation ICP-MS imaging of gold and other trace elements in pyrite from four different sediment- hosted gold-arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit: an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements, in particular, As, Ni, Pb, Zn, Ag, Mo, Te, V, and Se; and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and/or hydrothermal pyrite or as narrow gold- arsenic rims on the outermost parts of the overgrowth hydrothermal pyrite. Compared to the diagenetic pyrites, the hydrothermal pyrites are commonly depleted in Ni, V, Zn, Pb, and Ag with cyclic zones of Co, Ni, and As concentration. The outermost hydrothermal pyrite rims are either As-Au rich, as in moderate- to high- grade deposits such as Carlin and Bendigo, or Co-Ni rich and As-Au poor as in moderate- to low-grade deposits such as Sukhoi Log and Spanish Mountain. The early enrichment of gold in arsenic-bearing syngenetic to diagenetic pyrite, within black shale facies of sedimentary basins, is proposed as a critical requirement for the later development of Carlin-style and orogenic gold deposits in sedimentary environments. The best grade sediment-hosted deposits appear to have the gold climax event, toward the final stages of deformation-related hydrothermal pyrite growth and fluid flow. ?? 2009 Society of Economic Geologists, Inc.

  8. Research on the growth orientation of pyrite grains in the colloform textures in Baiyunpu Pb-Zn polymetallic deposit, Hunan, China

    Science.gov (United States)

    Gao, Shang; Huang, Fei; Gu, Xiangping; Chen, Zhenyu; Xing, Miaomiao; Li, Yongli

    2017-02-01

    A large number of colloform-textured pyrites were found in Baiyunpu Pb-Zn ore bodies in Xinshao County, Hunan, China. This study investigates the growth orientation of the pyrite grains in these structures by field emission scanning electron microscopy (FE-SEM), in situ micro X-ray diffraction (μXRD) and electron backscatter diffraction (EBSD). The growth proceeded from micro-crystalline cores in the colloform textures. Moreover, the pyrite layers were discrete and separated by locally significant quantities of galena and calcite. The μXRD results suggested clear crystalline characteristics and weakly preferred orientations of the colloform textures. EBSD confirmed that the pyrite grains exist preferred orientations or in the layered zones. According to the crystal growth theory, the formation and variation of crystal preferred orientations (CPOs) in pyrite are mainly restricted by the internal crystal structure of the pyrite and depends on the external environment conditions, such as trace element concentrations and the supersaturation degree. We inferred the evolutionary regularity of lattice planes with different indices in the pyrite crystal structure from morphological, compositional and growth orientation information, which reflect the crystal growth history of the colloform pyrite. This study will advance our understanding of the growth processes of colloform pyrite and environmental evolution in the Baiyunpu Pb-Zn polymetallic deposits.

  9. Flotation and Adsorption of a New Polysaccharide Depressant on Pyrite and Talc in the Presence of a Pre-Adsorbed Xanthate Collector

    Directory of Open Access Journals (Sweden)

    Wei Deng

    2017-03-01

    Full Text Available The flotation and adsorption of a new polysaccharide konjac gum (KG on pyrite and talc in the presence of pre-adsorbed potassium butyl xanthate (PBX is investigated. The micro-flotation results show that KG is a quality depressant for talc and that conditioning the minerals initially with PBX before KG will increase the recovery difference between pyrite and talc. The results of artificially mixing the minerals show that compared with adding KG before PBX, when minerals are pre-adsorbed with PBX, the grade and the recovery of sulfur (S increases by 1.96% and 5.44%, respectively. The contact angle results show that the addition of PBX before KG will increase the contact angles of pyrite, but the addition order of KG/PBX has little influence on the contact angles of talc. The adsorption tests show that KG can adsorb on pyrite and talc surfaces, while PBX can only adsorb on the pyrite surface. The addition order of KG/PBX affects the adsorption of KG and PBX on the pyrite surface but not on the talc surface. Fourier transform infrared (FTIR spectra analysis further demonstrates the chemical adsorption of KG on pyrite and talc surfaces, while PBX chemisorbs on the pyrite surface. Based on these analyses, a schematic illustration of the reagent adsorption forms on pyrite and talc surfaces is drawn to explain the competitive adsorption of KG and PBX on mineral surfaces.

  10. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching.

    Science.gov (United States)

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio

    2016-01-01

    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution.

  11. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching

    Science.gov (United States)

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio

    2016-01-01

    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution. PMID:26947441

  12. Cinnabar, arsenian pyrite and thallium-enrichment in active shallow submarine hydrothermal vents at Paleochori Bay, Milos Island, Greece

    Science.gov (United States)

    Kati, Marianna; Voudouris, Panagiotis; Valsami-Jones, Eugenia; Magganas, Andreas; Baltatzis, Emmanouil; Kanellopoulos, Christos; Mavrogonatos, Constantinos

    2015-04-01

    We herein report the discovery of active cinnabar-depositing hydrothermal vents in a submarine setting at Paleochori Bay, within the offshore southeastern extension of the Milos Island Geothermal Field, South Aegean Active Volcanic Arc. Active, low temperature (up to 115 °C) hydrothermal venting through volcaniclastic material has led to a varied assemblage of sulfide and alteration mineral phases in an area of approximately 1 km2. Our samples recovered from Paleochori Bay are hydrothermal edifices composed of volcaniclastic detrital material cemented by pyrite, or pure sulfide (mainly massive pyrite) mounts. Besides pyrite and minor marcasite, the hydrothermal minerals include cinnabar, amorphous silica, hydrous ferric oxides, carbonates (aragonite and calcite), alunite-jarosite solid solution and Sr-rich barite. Among others, growth textures, sieve-textured pyrite associated with barite, alunite-jarosite solid solution and hydrous ferric oxides rims colloform-banded pyrite layers. Overgrowths of arsenian pyrite layers (up to 3.2 wt. % As and/or up to 1.1 wt. % Mn) onto As-free pyrite indicate fluctuation in As content of the hydrothermal fluid. Mercury, in the form of cinnabar, occurs in up to 5 μm grains within arsenian pyrite layers, usually forming distinct cinnabar-enriched micro-layers. Hydrothermal Sr-rich barite (barite-celestine solid solution), pseudocubic alunite-jarosite solid solution and Mn- and Sr-enriched carbonates occur in various amounts and closely associated with pyrite and/or hydrous ferric oxides. Thallium-bearing sulfides and/or sulfosalts were not detected during our study; however, hydrous ferric oxides show thallium content of up to 0.5 wt. % Tl. The following scenarios may have played a role in pyrite precipitation at Paleochori: (a) H2S originally dissolved in the deep fluid but separated upon boiling could have reacted with oxygenated seawater under production of sulphuric acid, thus causing leaching and dissolution of primary iron

  13. Multiscale characterization of pyritized plant tissues in blueschist facies metamorphic rocks

    Science.gov (United States)

    Bernard, Sylvain; Benzerara, Karim; Beyssac, Olivier; Brown, Gordon E., Jr.

    2010-09-01

    Pyritized plant tissues with well-preserved morphology were studied in rocks from Vanoise (western Alps, France) that experienced high-pressure, low-temperature metamorphic conditions in the blueschist facies during the Alpine orogeny. Organic and inorganic phases composing these fossils were characterized down to the nanometer scale by Raman microspectroscopy, scanning transmission X-ray microscopy and transmission electron microscopy. The graphitic but disordered organic matter composing these fossils is chemically and structurally homogeneous and mostly contains aromatic functional groups. Its original chemistry remains undefined likely because it was significantly transformed by diagenetic processes and/or thermal degradation during metamorphism. Various mineral phases are closely associated with this organic matter, including sulphides such as pyrite and pyrrhotite, carbonates such as ankerite and calcite, and iron oxides. A tentative time sequence of formation of these diverse mineral phases relative to organic matter decay is proposed. The absence of traces of organic matter sulphurization, the pervasive pyritization of the vascular tissues and the presence of ankerite suggest that the depositional/diagenetic environment of these metasediments was likely rich in reactive iron. Fe-sulphides and ankerite likely precipitated early and might have promoted the preservation of the fossilized biological soft tissues by providing mechanical resistance to compaction during diagenesis and subsequent metamorphism. In contrast, iron oxides which form rims of 100-nm in thickness at the interface between organic matter and Fe-sulphides may result from metamorphic processes. This study illustrates that it may be possible in some instances to deconvolve metamorphic from diagenetic imprints and opens new avenues to better constrain processes that may allow the preservation of organic fossils during diagenesis and metamorphism.

  14. The pyrite-type high-pressure form of FeOOH

    Science.gov (United States)

    Nishi, Masayuki; Kuwayama, Yasuhiro; Tsuchiya, Jun; Tsuchiya, Taku

    2017-07-01

    Water transported into Earth’s interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth’s deep interior, implying that surface water may be transported as far as the core-mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system. Here we report the stability of FeOOH phases at the pressure and temperature conditions of the deep lower mantle, based on first-principles calculations and in situ X-ray diffraction experiments. In contrast to previous work suggesting the dehydrogenation of FeOOH into FeO2 in the middle of the lower mantle, we report the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe2O3 and releases H2O when subducted slabs are heated at the base of the mantle. This process may cause the incorporation of hydrogen into the outer core by the formation of iron hydride, FeHx, in the reducing environment of the core-mantle boundary.

  15. Iron pyrite thin films synthesized from an Fe(acac)3 ink.

    Science.gov (United States)

    Seefeld, Sean; Limpinsel, Moritz; Liu, Yu; Farhi, Nima; Weber, Amanda; Zhang, Yanning; Berry, Nicholas; Kwon, Yon Joo; Perkins, Craig L; Hemminger, John C; Wu, Ruqian; Law, Matt

    2013-03-20

    Iron pyrite (cubic FeS2) is a promising candidate absorber material for earth-abundant thin-film solar cells. Here, we report on phase-pure, large-grain, and uniform polycrystalline pyrite films that are fabricated by solution-phase deposition of an iron(III) acetylacetonate molecular ink followed by sequential annealing in air, H2S, and sulfur gas at temperatures up to 550 °C. Phase and elemental compositions of the films are characterized by conventional and synchrotron X-ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy (XPS). These solution-deposited films have more oxygen and alkalis, less carbon and hydrogen, and smaller optical band gaps (E(g) = 0.87 ± 0.05 eV) than similar films made by chemical vapor deposition. XPS is used to assess the chemical composition of the film surface before and after exposure to air and immersion in water to remove surface contaminants. Optical measurements of films rich in marcasite (orthorhombic FeS2) show that marcasite has a band gap at least as large as pyrite and that the two polymorphs share similar absorptivity spectra, in excellent agreement with density functional theory models. Regardless of the marcasite and elemental impurity contents, all films show p-type, weakly activated transport with curved Arrhenius plots, a room-temperature resistivity of ~1 Ω cm, and a hole mobility that is too small to measure by Hall effect. This universal electrical behavior strongly suggests that a common defect or a hole-rich surface layer governs the electrical properties of most FeS2 thin films.

  16. Evolution of biofilms during the colonization process of pyrite by Acidithiobacillus thiooxidans.

    Science.gov (United States)

    González, Dulce M; Lara, René H; Alvarado, Keila N; Valdez-Pérez, Donato; Navarro-Contreras, Hugo R; Cruz, Roel; García-Meza, Jessica Viridiana

    2012-01-01

    We have applied epifluorescence principles, atomic force microscopy, and Raman studies to the analysis of the colonization process of pyrite (FeS(2)) by sulfuroxidizing bacteria Acidithiobacillus thiooxidans after 1, 15, 24, and 72 h. For the stages examined, we present results comprising the evolution of biofilms, speciation of S (n) (2-) /S(0) species, adhesion forces of attached cells, production and secretion of extracellular polymeric substances (EPS), and its biochemical composition. After 1 h, highly dispersed attached cells in the surface of the mineral were observed. The results suggest initial non-covalent, weak interactions (e.g., van der Waal's, hydrophobic interactions), mediating an irreversible binding mechanism to electrooxidized massive pyrite electrode (eMPE), wherein the initial production of EPS by individual cells is determinant. The mineral surface reached its maximum cell cover between 15 to 24 h. Longer biooxidation times resulted in the progressive biofilm reduction on the mineral surface. Quantification of attached cell adhesion forces indicated a strong initial mechanism (8.4 nN), whereas subsequent stages of mineral colonization indicated stability of biofilms and of the adhesion force to an average of 4.2 nN. A variable EPS (polysaccharides, lipids, and proteins) secretion at all stages was found; thus, different architectural conformation of the biofilms was observed during 120 h. The main EPS produced were lipopolysaccharides which may increase the hydrophobicity of A. thiooxidans biofilms. The highest amount of lipopolysaccharides occurred between 15-72 h. In contrast with abiotic surfaces, the progressive depletion of S (n) (2-) /S(0) was observed on biotic eMPE surfaces, indicating consumption of surface sulfur species. All observations indicated a dynamic biooxidation mechanism of pyrite by A. thiooxidans, where the biofilms stability and composition seems to occur independently from surface sulfur species depletion.

  17. Inertization of pyrite cinders and co-inertization with electric arc furnace flue dusts by pyroconsolidation at solid state.

    Science.gov (United States)

    Viñals, J; Balart, M J; Roca, A

    2002-01-01

    The viability of a pyroconsolidation process to render pyrite cinders inert and to co-inert pyrite cinders with a hazardous polymetallic residue such as electric arc furnace flue dusts (EAF) containing Pb, Cu, Zn, As, Cr, Ni and Mo were investigated. The effects of pyroconsolidation temperature (800-1200 degrees C), milling pyrite cinders and additions of both CaO and EAF on the resulting microstructure of the pellets were determined. The microstructural changes were then compared with the results of the standard leaching tests. Full inertization of pyrite cinders was achieved after milling to < 100 micron followed by a pelletization and pyroconsolidation process at a temperature of 1200 degrees C. This process also allows co-inertization of pyrite cinders with controlled additions of EAF (up to approximately to 10%). Following pyroconsolidation at 1200 degrees C, the metallic elements were inert components in the four main phases: traces of Cr in hematite; Cr, Cu, Zn and Ni in spinel-phase; traces of Cr and Zn in calcium ferrites; and Pb and traces of Cu, Zn and Ba in K-Ca-Al-Fe glassy silicate.

  18. Surficial phase-identification and structural profiles from weathered natural pyrites: A grazing-incidence X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Cai Yuanfeng [State Key Laboratory of Mineral Deposits Research, Nanjing 210093 (China); Department of Earth Sciences, Nanjing University, Nanjing 210093 (China)], E-mail: caiyf@nju.edu.cn; Pan, Yuguan [State Key Laboratory of Mineral Deposits Research, Nanjing 210093 (China); Xue Jiyue; Su Guizhen [Department of Earth Sciences, Nanjing University, Nanjing 210093 (China)

    2009-01-15

    Five pyrites with original crystal face (1 0 0) with different tarnish colours were selected from one pyrite-bearing ore sample from Tongling multi-metal deposit, Anhui, China. They are henna mottled with dark violet, yellow mottled with red, yellow, blue mottled with violet and reddish brown in surface colour. Grazing-incidence X-ray diffractometry (GIXRD) was used to study the phases formed or precipitated on the surface of pyrite (1 0 0) face during chemical weathering. By changing the incident angle, GIXRD can provide information on the changes in the mineral phases from the surface as a function of depth. Products formed or precipitated on the surface of pyrite (1 0 0) face are one or several sulfur or iron-bearing hydrated oxides and include gypsum, jalpaite, goethite, goldichite. The sulfur-bearing minerals present on the surface imply the oxidation of sulfur to sulfate, or the reduction of sulfur to sulfide. By analyzing a series of GIXRD patterns obtained at different angles of incidence for a single pyrite, the mineral assemblage differs from the surface into the body of the crystal. Taking the reddish brown sample as an example, four diffraction profiles at 2.575, 2.2105, 1.9118 and 1.613 A are present in the pattern of a 2{sup o} incident angle experiment whereas they cannot be found at a GIXRD angle smaller than 0.6{sup o}.

  19. Influence of Sulfobacillus thermosulfidooxidans on Initial Attachment and Pyrite Leaching by Thermoacidophilic Archaeon Acidianus sp. DSM 29099

    Directory of Open Access Journals (Sweden)

    Jing Liu

    2016-07-01

    Full Text Available At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1 Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidansT during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2 active or inactivated cells of S. thermosulfidooxidansT on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3 S. thermosulfidooxidansT exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment.

  20. Selenium, tellurium and precious metal mineralogy in Uchalinsk copper-zinc-pyritic district, the Urals

    Science.gov (United States)

    Vikentev, I.

    2016-04-01

    During processing the most of Au, Ag, Se, Te, Pb, Bi, Sb, Hg as well as notable part of Cu, Zn and Cd fail for tailings and became heavy metal pollutants. Modes of occurrence of Au, Ag, Te and Se covers two giant VMS deposits: Uchaly (intensively deformed) and Uzelginsk (altered by late hydrothermal processes) as well as middle-sized Molodezn and West Ozern deposits (nondeformed) have been studied. Mineral forms of these elements as well as their presence in disperse mode in common ore minerals (pyrite, chalcopyrite, sphalerite) have been studied using SEM, EPMA, INAA, ICP-MS and LA-ICP-MS.

  1. Synthesis, characterization and processing of cubic iron pyrite nanocrystals in a photovoltaic cell

    Energy Technology Data Exchange (ETDEWEB)

    Alam Khan, M., E-mail: alamkhan77@gmail.com; Sarker, J.C.; Lee, Seunyong; Mangham, Scott C.; Manasreh, M.O.

    2014-12-15

    Cubic iron pyrite (fool's gold) nanocrystals with an average diameter of ∼60 nm were grown in an oleylamine ligand which acts as a solvent and surfactant without the utilization of alkyl phosphine and phosphonic acids at 230 °C in a Schlenk flask. For the first time photoluminescence properties of such cubic nanocrystals were analyzed at 77 K, showing band gaps of 1.71 eV. However, UV–Vis spectra shows a band gap of 1.41 eV for the same nanocrystals, close to the direct band gap (1.38 eV) of reported pyrite materials. The discrepancy of 0.3 eV in absorption (UV–Vis) and emission spectra (PL) are attributed to the phonon coupling (stokes shift). The prepared cubic nanocrystals were well suited for an inexpensive thin film solar cells and further processed and spin casted with a synthesized CdSe quantum dots in chloroform solvent as a bulk-heterojunction (BHJ) solar cell in order to get photovoltaic responses in real devices. We successfully report here an efficiency of 0.5% with the J{sub SC} of 3.7 mA/cm{sup −2} and V{sub OC} of 0.16 mV with a cell structure of ITO/PEDOT:PSS/FeS{sub 2}:CdSe/Au. The morphology and optoelectronic properties are elucidated by SEM, TEM, TEM-EDS, XRD, micro-Raman spectra, IV curve and micro-PL techniques. - Highlights: • Excellent cubic iron pyrite nanocrystals are synthesized by using an oleylamine ligand. • First time PL spectra were used to measure band gaps of such colloidal cubic nanocrytsals. • Pyrite ink was made in suitable solvent to fabricate practical devices. • A successful 0.5% efficiency is reported in bulk-heterojunction cell with CdSe QDs.

  2. Degree of trace metal pyritization in sediments from the Pacific coast of Baja California, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nava Lopez, Carmen; Huerta Diaz, Miguel Angel [Instituto de Investigaciones Oceanologicas, Ensenada, Baja California (Mexico)

    2001-06-01

    We analyzed sediments from a core collected on the Pacific coast of Baja California, 45 km off the city of Tijuana and at 1257 m water depth (32 Celsius degrees 9.5N , 117 Celsius degrees 8.3W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate transference of Cu>Ni>Zn>>Hg y Ag from the HCl to the pyrite fraction. Sediments have degrees of pyritization (DOP) that average 7.2{+-} 4.9% with a maximum value of 18.5%. Average degrees of trace metal pyritization (DTMP) range from 6.2 {+-}2.1% to 83{+-} 8% for Mn and Hg, respectively, although maximum values for some metals were closed to 100%. This transference is apparently a function of the solubility products of metal sulfides and the relative abundances of metals in the HCl fraction, as suggested by the significant correlation (p<0.001) observed between these two parameters and the DTMP of a number of trace metals. A similar correlation was obtained from published data of two cores collected in the Gulf of Mexico. [Spanish] Se analizaron sedimentos de un nucleo recolectado en la costa del Pacifico de Baja California 45 km de la costa de la ciudad de Tijuana y a 1257 m de profundidad del agua (32 grados Celsius 9.5N, 117 grados Celsius 8.3W), para determinar su contenido de metales traza en dos fracciones operacionales definidas HCl y pirita. Los resultados indican una transferencia de Cu>Ni>Zn>>Hg y Ag de la fraccion de HCl a la fase piritica. Los grados de piritizacion (DOP) en los sedimentos promediaron 7.2{+-} 4.9%, con un valor maximo de 18.5%. Los valores promedio de los grados de piritizacion de metales traza (DTMP) abarcaron el intervalo de 6.2 {+-}2.1% a 83{+-}18% para Mn y Hg, respectivamente, aunque los valores maximos para algunos metales estuvieron cercanos al 100%. Esta transferencia aparentemente es funcion de los productos de solubilidad de los sulfuros metalicos y de la abundancia relativa de metales en la fraccion HCl, como sugiere la correlacion

  3. Determination of the Content of Heavy Metals in Pyrite Contaminated Soil and Plants

    Directory of Open Access Journals (Sweden)

    Miroslava Marić

    2008-09-01

    Full Text Available Determination of a pyrite contaminated soil texture, content of heavy metals in the soil and soil pH, was the aim in the investigation. Acidification of damaged soil was corrected by calcium carbonate. Mineral nutrients and organic matter (NPK, dung, earthworm cast, straw and coal dust were added to damaged soil. Afterwards, the soil was used for oat production. Determination of total heavy metal contents (Cu, Pb, Zn, Fe in soil was performed by atomic absorption spectrofotometry. Plant material (stems, seeds was analysed, too. Total concentration of the heavy metals in the plant material were greater than in crop obtained in unaffected soil.

  4. The effect of rehabilitation on the rate of oxidation of pyrite in a mine waste rock dump.

    Science.gov (United States)

    Harries, J R; Ritchie, A I

    1987-06-01

    Temperature profiles within a mine waste rock dump undergoing pyritic oxidation have been used to estimate the rate of oxidation and the sites where oxidation was occurring. The waste rock dump is located at the abandoned Rum Jungle mine site in Northern Australia and was a major source of pollution to the local river system. The dump was rehabilitated in 1983-84 by reshaping to reduce erosion and covering with clay and soil to reduce infiltration of water.Heat source distributions were derived from temperature profiles measured in the dump. The oxidation of pyritic material is the main cause of heat in the dump, hence the rate and location of oxidation can be obtained from the distribution of heat sources. A comparison of the heat source distributions before and after rehabilitation showed that rehabilitation greatly reduced or stopped the oxidation of pyrite in the dump.

  5. Archaeal diversity and the extent of iron and manganese pyritization in sediments from a tropical mangrove creek (Cardoso Island, Brazil)

    Science.gov (United States)

    Otero, X. L.; Lucheta, A. R.; Ferreira, T. O.; Huerta-Díaz, M. A.; Lambais, M. R.

    2014-06-01

    Even though several studies on the geochemical processes occurring in mangrove soils and sediments have been performed, information on the diversity of Archaea and their functional roles in these ecosystems, especially in subsurface environments, is scarce. In this study, we have analyzed the depth distribution of Archaea and their possible relationships with the geochemical transformations of Fe and Mn in a sediment core from a tropical mangrove creek, using 16S rRNA gene profiling and sequential extraction of different forms of Fe and Mn. A significant shift in the archaeal community structure was observed in the lower layers (90-100 cm), coinciding with a clear decrease in total organic carbon (TOC) content and an increase in the percentage of sand. The comparison of the archaeal communities showed a dominance of methanogenic Euryarchaeota in the upper layers (0-20 cm), whereas Crenarchaeota was the most abundant taxon in the lower layers. The dominance of methanogenic Euryarchaeota in the upper layer of the sediment suggests the occurrence of methanogenesis in anoxic microenvironments. The concentrations of Fe-oxyhydroxides in the profile were very low, and showed positive correlation with the concentrations of pyrite and degrees of Fe and Mn pyritization. Additionally, a partial decoupling of pyrite formation from organic matter concentration was observed, suggesting excessive Fe pyritization. This overpyritization of Fe can be explained either by the anoxic oxidation of methane by sulfate and/or by detrital pyrite tidal transportation from the surrounding mangrove soils. The higher pyritization levels observed in deeper layers of the creek sediment were also in agreement with its Pleistocenic origin.

  6. Re-Os pyrite geochronology of Zn-Pb mineralization in the giant Caixiashan deposit, NW China

    Science.gov (United States)

    Li, Dengfeng; Chen, Huayong; Hollings, Pete; Zhang, Li; Mi, Mei; Li, Jie; Fang, Jing; Wang, Chengming; Lu, Wanjian

    2016-03-01

    The newly discovered Caixiashan Irish-type Zn-Pb deposit (˜131 Mt at 3.95 % Zn + Pb), located in the Eastern Tianshan of Xinjiang, is one of the largest Zn-Pb deposits in NW China. Massive colloform/framboidal textured syn-sedimentary pyrite yielded a Re-Os isochron age of 1019 ± 70 Ma (MSWD = 3.5), which is interpreted to be the depositional age of the Kawabulake group that hosts the ore. The age of the main mineralization stage is constrained by two types of pyrite: the layered pyrite coexists with recrystallized calcite and dolomite and is locally replaced by sphalerite, whereas the euhedral pyrite occurs with galena that crosscuts the massive sphalerite. The layered pyrite yielded a Re-Os age of 859 ± 79 Ma (MSWD = 6.7; initial 187Os/188Os ratio [IOs] = 0.19 ± 0.25) and the euhedral pyrite 837 ± 39 Ma (MSWD = 6.5; [IOs] = 0.16 ± 0.09), which are interpreted to be the Zn and Pb mineralization ages, respectively. The low radiogenic initial Os values of the Zn-Pb mineralization suggest interaction between a hydrothermal fluid and a mafic or ultramafic source rock with a mantle Os signature with some contamination with Mesoproterozoic Kawabulake group. Based on our new Re-Os ages, we conclude that the giant Caixiashan Zn-Pb deposit formed in the early Neoproterozoic and it represents a newly identified mineralization epoch in the Eastern Tianshan of the Central Asia Orogenic Belt.

  7. Electrochemical mineralization of the antibiotic levofloxacin by electro-Fenton-pyrite process.

    Science.gov (United States)

    Barhoumi, Natija; Labiadh, Lazhar; Oturan, Mehmet A; Oturan, Nihal; Gadri, Abdellatif; Ammar, Salah; Brillas, Enric

    2015-12-01

    Levofloxacin is a large spectrum antibiotic from fluoroquinolones family, widely used and detected in natural waters. Here, this drug was degraded by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder in suspension regulates the solution pH to 3.0 and supplies 0.2mM Fe(2+) as catalyst to the solution. Trials were performed with a stirred boron-doped diamond (BDD)/carbon-felt cell under O2 bubbling for cathodic H2O2 generation. Hydroxyl radicals formed from water oxidation at the BDD anode and in the bulk from Fenton's reaction between Fe(2+) and H2O2 were the main oxidizing agents. The effect of applied current and antibiotic concentration over the mineralization rate and degree, mineralization current efficiency and specific energy consumption was studied. An almost total mineralization was achieved for a 0.23mM drug solution operating at 300mA for 8h. The kinetic decay of the drug was followed by reversed-phase HPLC and obeyed a pseudo-first-order reaction. Ion-exclusion HPLC analysis of treated solutions revealed that oxalic and oxamic acids, the most persistent final products, were the predominant pollutants remaining in solution at long electrolysis time. Ion chromatography analysis confirmed the release of F(-), NO3(-) and NH4(+) ions during levofloxacin mineralization. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

    KAUST Repository

    Cabán-Acevedo, Miguel

    2015-09-14

    The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS 2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm at overpotentials as low as 48mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n -p-p silicon micropyramids achieved photocurrents up to 35 mA cm at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

  9. Sulfidation Roasting of Hemimorphite with Pyrite for the Enrichment of Zn and Pb

    Science.gov (United States)

    Min, Xiao-Bo; Xue, Ke; Ke, Yong; Zhou, Bo-Sheng; Li, Yang-Wen-Jun; Wang, Qing-Wei

    2016-09-01

    With the increasing consumption of zinc and the depletion of zinc sulfide ores, the exploitation of low-grade zinc oxide ores may be important for the sustainability of the zinc industry. Hemimorphite, a zinc hydroxyl silicate hydrate, is a significant source of Zn and Pb. It is difficult to obtain Zn and Pb from the hemimorphite using traditional technology. In this work, for the first time, sulfidation roasting of hemimorphite with pyrite was studied for the enrichment of Zn and Pb by a flotation process. Four stages of sulfidation roasting were determined based on x-ray diffraction and thermogravimetry analysis. Then, the effects of sulfidation temperature, pyrite dosage and reaction time on the sulfidation percentages were investigated at the laboratory scale. The experimental results showed that the sulfidation percentages of Pb and Zn were as high as 98.08% and 90.55% under optimum conditions, respectively. Finally, a flotation test was performed to enrich Zn and Pb in the sulfidation product. A flotation concentrate with 8.78% Zn and 9.25% Pb was obtained, and the recovery of Zn and Pb reached 56.14% and 75.94%, respectively.

  10. An experimental study of pyrite bio-leaching as a way to control spontaneous combustion

    Institute of Scientific and Technical Information of China (English)

    Yin Shenghua; Wu Aixiang; Liu Jinzhi; Huang Mingqing; Wang Hongjiang

    2011-01-01

    Bio-leaching of pyrite by native strains of acidophilic bacteria was examined by laboratory scale tests.Three groups of batch trials in agitated flasks and three continuous column leaching tests were performed.The leaching ability and efficiency of native bacteria was greatly improved by adaptation of the bacteria to the test conditions.These cultivated bacteria were then used for the leaching process.The changes in solution pH,Eh,Fe2+ concentration,and sulfate ion concentration were monitored throughout the tests.A portion of the pyritic sulfur is transformed into soluble sulfate ion.The desulfurization ratio of 42.6% was obtained in a flask shaking test and a ratio of 39.4% was obtained during column leaching.A weight gain test was performed on leached and unleached samples by exposing the samples to humid air for several days.A smaller weight gain of the bio-leached samples indicates that removing sulfur from the sulphide ore helps reduce its oxidation rate and the potential for spontaneous combustion.

  11. A novel magnetic 4A zeolite adsorbent synthesised from kaolinite type pyrite cinder (KTPC)

    Science.gov (United States)

    Wang, Weiqing; Feng, Qiming; Liu, Kun; Zhang, Guofan; Liu, Jing; Huang, Yang

    2015-01-01

    As a solid waste, kaolinite type pyrite cinder (KTPC) is a special pyrite cinder, its mineral components include metakaolin and magnetite, and the chemical compositions of these minerals include SiO2, Al2O3, FeO and Fe2O3. In this study, a novel magnetic 4A zeolite adsorbent was synthesised from KTPC using the hydrothermal method, and the optimum hydrothermal synthesis conditions were investigated using X-ray diffraction (XRD) and by determining the specific surface area (SSA) and the saturated cation exchange adsorption capacity (SCEAC) to Cs+. Under the optimum hydrothermal synthesis conditions, the magnetic 4A zeolite adsorbent can be synthesised with high crystallinity, and the SSA and SCEAC to Cs+ are 24.49 m2/g and 106.63 mg/g, respectively. The further characterisations of pore size distribution, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) were performed. The results revealed that magnetic particles are coated onto the zeolite surface and further form magnetic aggregates, and the existing magnetic particles in KTPC do not change their crystal structure and do not affect the synthesis of the 4A zeolite. In addition, the synthesised 4A zeolite adsorbent can be used as a magnetic adsorbent in wastewater treatment with high magnetic sensitivity and is thermally stable up to approximately 900 °C.

  12. Bacterial communities involved in soil formation and plant establishment triggered by pyrite bioweathering on arctic moraines.

    Science.gov (United States)

    Mapelli, Francesca; Marasco, Ramona; Rizzi, Agostino; Baldi, Franco; Ventura, Stefano; Daffonchio, Daniele; Borin, Sara

    2011-02-01

    In arctic glacier moraines, bioweathering primed by microbial iron oxidizers creates fertility gradients that accelerate soil development and plant establishment. With the aim of investigating the change of bacterial diversity in a pyrite-weathered gradient, we analyzed the composition of the bacterial communities involved in the process by sequencing 16S rRNA gene libraries from different biological soil crusts (BSC). Bacterial communities in three BSC of different morphology, located within 1 m distance downstream a pyritic conglomerate rock, were significantly diverse. The glacier moraine surrounding the weathered site showed wide phylogenetic diversity and high evenness with 15 represented bacterial classes, dominated by Alphaproteobacteria and pioneer Cyanobacteria colonizers. The bioweathered area showed the lowest diversity indexes and only nine bacterial families, largely dominated by Acidobacteriaceae and Acetobacteraceae typical of acidic environments, in accordance with the low pH of the BSC. In the weathered BSC, iron-oxidizing bacteria were cultivated, with counts decreasing along with the increase of distance from the rock, and nutrient release from the rock was revealed by environmental scanning electron microscopy-energy dispersive X-ray analyses. The vegetated area showed the presence of Actinomycetales, Verrucomicrobiales, Gemmatimonadales, Burkholderiales, and Rhizobiales, denoting a bacterial community typical of developed soils and indicating that the lithoid substrate of the bare moraine was here subjected to an accelerated colonization, driven by iron-oxidizing activity.

  13. Investigation by sup 5 sup 7 Fe- Moessbauer spectroscopy of some pyrite samples of different Romanian natural deposits

    CERN Document Server

    Constantinescu, S; Calogero, S

    2002-01-01

    Extracted pyrites from four Romanian geological deposits have been investigated by Moessbauer spectroscopy. The room temperature results of this investigation have been correlated with the data of sulfur isotope ratio and minor elements analysis of pyrite samples. The presence of three signals is identified in the Moessbauer spectra. They correspond to the two crystalline structure of FeS sub 2 while the third is suggested to be assigned to one of the components of the iron-sulfur-arsenic series of investigated minerals. (authors)

  14. Cretaceous Cu-Au, pyrite, and Fe-oxide-apatite deposits in the Ningwu basin, Lower Yangtze Area, Eastern China

    Science.gov (United States)

    Yu, Jin-Jie; Lu, Bang-Cheng; Wang, Tie-Zhu; Che, Lin-Rui

    2015-05-01

    The Cretaceous Ningwu volcanic basin of the Middle and Lower Yangtze River Valley metallogenic belt of eastern China hosts numerous Fe-oxide-apatite, Cu-Au, and pyrite deposits. The mineralization in the Ningwu basin is associated with subvolcanic rocks, consisting of gabbro-diorite porphyry and/or pyroxene diorite. However, the mineralization is associated with subvolcanic and volcanic rock suite belonging to the Niangniangshan Formation in the Tongjing Cu-Au deposit, including nosean-bearing aegirine-augite syenites, quartz syenites, and quartz monzonites. The zoning displayed by the alteration and mineralization comprises: (1) an upper light-colored zone of argillic, carbonate, and pyrite alteration and silicification that is locally associated with pyrite and gold mineralization, (2) a central dark-colored zone of diopside, fluorapatite-magnetite, phlogopite, and garnet alteration associated with fluorapatite-magnetite mineralization, and (3) a lowermost light-colored zone of extensive albite alteration. The Cu-Au and pyrite orebodies are peripheral to the Fe-oxide-apatite deposits in this area and overlie the iron orebodies, including the Meishan Cu-Au deposit in the northern Ningwu basin and the pyrite deposits in the central Ningwu basin. The δ34S values of sulfides from the Fe-oxide-apatite, Cu-Au, and pyrite deposits in the Ningwu basin show large variation, with a mixed sulfur source, including magmatic sulfur and/or a mixture of sulfur derived from a magmatic component, country rock, and thermochemical reduction of sulfate at 200-300 °C. The ore-forming fluids associated with iron mineralization were derived mainly from magmatic fluids, and the late-stage ore-forming fluids related to Cu-Au and pyrite mineralization may have formed by the introduction of cooler meteoric water to the system. The Fe-oxide-apatite, Cu-Au, and pyrite deposits of the Ningwu basin formed in an extensional environment and are associated with a large-scale magmatic

  15. S/Se ratio of pyrite from eastern Australian VHMS deposits: implication of magmatic input into volcanogenic hydrothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Huston, D.L. [Geological Survey of Canada, Ottawa, ON (Canada); Sie, S.H.; Suter, G.F. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience; Cooke, D.R. [Tasmania Univ., Sandy Bay, TAS (Australia)

    1993-12-31

    The proton microprobe was used to determine the concentrations of over twenty trace elements in pyrite grains from four volcanic-hosted massive sulphide (VHMS) deposits in eastern Australia. Of the elements determined, Se has the most potential in resolving important problems in the genesis of this class of ore deposits. This paper summarises analytical conditions, describes the distribution of Se in pyrite in VHMS deposits as determined in this and other studies, discusses the speciation of Se in hydrothermal fluids, and presents a genetic model on the relative contribution of magmatic versus sea water Se (and S) in VHMS systems. 2 refs., 1 fig.

  16. Degradation of tyrosol by a novel electro-Fenton process using pyrite as heterogeneous source of iron catalyst.

    Science.gov (United States)

    Ammar, Salah; Oturan, Mehmet A; Labiadh, Lazhar; Guersalli, Amor; Abdelhedi, Ridha; Oturan, Nihal; Brillas, Enric

    2015-05-01

    Tyrosol (TY) is one of the most abundant phenolic components of olive oil mill wastewaters. Here, the degradation of synthetic aqueous solutions of 0.30 mM TY was studied by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder was the source of Fe(2+) catalyst instead of a soluble iron salt used in classical EF. Experiments were performed with a cell equipped with a boron-doped diamond anode and a carbon-felt cathode, where TY and its products were destroyed by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between Fe(2+) and H2O2 generated at the cathode. Addition of 1.0 g L(-1) pyrite provided an easily adjustable pH to 3.0 and an appropriate 0.20 mM Fe(2+) to optimize the EF-pyrite treatment. The effect of current on mineralization rate, mineralization current efficiency and specific energy consumption was examined under comparable EF and EF-pyrite conditions. The performance of EF-pyrite was 8.6% superior at 50 mA due to self-regulation of soluble Fe(2+) by pyrite. The TY decay in this process followed a pseudo-first-order kinetics. The absolute rate constant for TY hydroxylation was 3.57 × 10(9) M(-1) s(-1), as determined by the competition kinetics method. Aromatic products like 3,4-dihydroxyphenylethanol, 4-hydroxyphenylacetic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid and catechol, as well as o-benzoquinone, were identified by GC-MS and reversed-phase HPLC. Short-chain aliphatic carboxylic acids like maleic, glycolic, acetic, oxalic and formic were quantified by ion-exclusion HPLC. Oxalic acid was the major and most persistent product found. Based on detected intermediates, a plausible mineralization pathway for TY by EF-pyrite was proposed.

  17. Abiotic oxidation of pyrite by Fe(III) in acidic media and its implications for sulfur isotope measurements of lattice-bound sulfate in sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Mazumdar, A.; Goldberg, T.; Strauss, H

    from our pure pyrite oxidation experiments show that in a solution of acidic pH, the amount of sulfate formed is very similar under both oxygenated and oxygen-free experimental conditions which is suggestive of the dominant role of Fe sup(3+) in pyrite...

  18. 某矿山硫铁矿尾砂浮选试验研究%Study on the flotation test of pyrite tailings from a pyrite mine

    Institute of Scientific and Technical Information of China (English)

    王淑红; 董风芝; 孙永峰

    2009-01-01

    在对试验用硫铁矿尾砂进行物理化学性质研究的基础上,对其进行浮选试验.以乙黄药为捕收剂,2号油为起泡剂,经过一粗一扫一精闭路试验,一次精选尾矿和扫选精矿合并返回粗选可以得到精矿品位41.07%、回收率92.73%、产率10.95%、尾矿品位0.4%的最终指标.%Flotation test was conducted on the basis of the study on physical and chemical characteristics of the tailings from pyrite ores.With ethylxanthate as collector and 2# oil as frother, roughing was under way in alkaline slurry with one roughing and one concentrating ,and the final indexes of concentrate grade of 41.07%, recovery rateof 92.73%, yield of 10.95% and grade of railings 0.4% are obtained.

  19. Evidence of CFC degradation in groundwater under pyrite-oxidizing conditions

    Science.gov (United States)

    Sebol, L.A.; Robertson, W.D.; Busenberg, E.; Plummer, L.N.; Ryan, M.C.; Schiff, S.L.

    2007-01-01

    A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1-5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ???5 years old was confined to an aerobic zone at ???5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7-11 ??C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6-7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3H/3He ratios indicated that groundwater-age continued to increase uniformly with depth, to a maximum value of 27 years at 13 m depth. CFC concentrations, however, decreased abruptly within the denitrifying zone, leading to substantial age overestimation compared to the 3H/3He ages. Noble gas data indicated that the apparent CFC mass loss was not likely the result of gas stripping from possible bubble formation; thus, CFC degradation was indicated in the anoxic zone. The field data are consistent with first-order degradation rates of 0.3 yr-1 for CFC-12, 0.7 yr-1 for CFC-11, and 1.6 yr-1 for CFC-113. CFC attenuation at this site coincides with a zone where reduced S (pyrite) is actively oxidized by NO3 and dissolved oxygen (DO). Similar behavior has been observed at other sites [Tesoriero, A.J., Liebscher, H., Cox, S.E., 2000. Mechanism and rate of denitrification in an agricultural watershed: electron and mass balance along groundwater flow path. Water Resour. Res. 36 (6), 1545-1559; Hinsby, K., Hojberg, A.L., Engesgaard, P., Jensen, K.H., Larsen, F., Plummer, L.N., Busenberg, E., Accepted for publication. Transport and degradation of chlorofluorocarbons (CFCs) in a pyritic aquifer, Rabis Creek, Denmark. Water Resour. Res.], further demonstrating that the use of CFCs for age-dating anaerobic

  20. Reactivity of Dazomet, a Hydraulic Fracturing Additive: Hydrolysis and Interaction with Pyrite

    Science.gov (United States)

    Consolazio, N.; Lowry, G. V.; Karamalidis, A.; Hakala, A.

    2015-12-01

    The Marcellus Shale is currently the largest shale gas formation in play across the world. The low-permeability formation requires hydraulic fracturing to be produced. In this process, millions of gallons of water are blended with chemical additives and pumped into each well to fracture the reservoir rock. Although additives account for less than 2% of the fracking fluid mixture, they amount to hundreds of tons per frack job. The environmental properties of some of these additives have been studied, but their behavior under downhole conditions is not widely reported in the peer-reviewed literature. These compounds and their reaction products may return to the surface as produced or waste water. In the event of a spill or release, this water has the potential to contaminate surface soil and water. Of these additives, biocides may present a formidable challenge to water quality. Biocides are toxic compounds (by design), typically added to the Marcellus Shale to control bacteria in the well. An assessment of the most frequently used biocides indicated a need to study the chemical dazomet under reservoir conditions. The Marcellus Shale contains significant deposits of pyrite. This is a ubiquitous mineral within black shales that is known to react with organic compounds in both oxic and anoxic settings. Thus, the objective of our study was to determine the effect of pyrite on the hydrolysis of dazomet. Liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) was used to calculate the loss rate of aqueous dazomet. Gas chromatography-mass spectrometry (GC-MS) was used to identify the reaction products. Our experiments show that in water, dazomet rapidly hydrolyses in water to form organic and inorganic transformation products. This reaction rate was unaffected when performed under anoxic conditions. However, with pyrite we found an appreciable increase in the removal rate of dazomet. This was accompanied by a corresponding change in the distribution of observed

  1. Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, April 1, 1995--June 30, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.E.J.; Mitchell, R.E.

    1995-12-01

    This document is the fourth quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion. The research project is intended to advance PETC`s efforts to improve our technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. The knowledge gained from this work is intended to be incorporated into numerical codes that can be used to formulate anti-slagging strategies involving minimal disturbance of coal combustor performance. This project is to be performed over the three-year period from September 1994 to August 1997. The project aims to identify the mechanisms of pyrite combustion and to quantify their effects, in order to formulate a general rate expression for the combustion of pyrite that accounts for coal properties as well as furnace conditions.

  2. Model-based integration and analysis of biogeochemical and isotopic dynamics in a nitrate-polluted pyritic aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Prommer, H.; Broers, H.P.; Slomp, C.P.; Greskowiak, J.; Van Der Grift, B.; Van Cappellen, P.

    2013-01-01

    Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as

  3. Element mobility during pyrite weathering: implications for acid and heavy metal pollution at mining-impacted sites

    Science.gov (United States)

    Lu, Long; Wang, Rucheng; Chen, Fanrong; Xue, Jiyue; Zhang, Peihua; Lu, Jianjun

    2005-11-01

    Based on back scattered electron images and electron micro-probe analysis results, four alteration layers, including a transition layer, a reticulated ferric oxide layer, a nubby ferric oxide layer and a cellular ferric oxide layer, were identified in the naturally weathering products of pyrite. These layers represent a progressive alteration sequence of pyrite under weathering conditions. The cellular ferric oxide layer correlates with the strongest weathering phase and results from the dissolution of nubby ferric oxide by acidic porewater. Leaching coefficient was introduced to better express the response of element mobility to the degree of pyrite weathering. Its variation shows that the mobility of S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite is oxidized to sulfuric acid and sulfate that are basically released into to porewater, and heavy metals Co and Bi are evidently released by acid dissolution. As, Cu and Zn are enriched in ferric oxide by adsorption and by co-precipitation, but they would re-release to the environment via desorption or dissolution when porewater pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may pose a substantial impact on water quality. Considering that metal mobility and its concentration in mine waste are two important factors influencing heavy metal pollution at mining-impacted sites, Bi and Co are more important pollutants in this case.

  4. Study on Bailing Properties of Pyrite Cinder%硫酸渣成球性能研究

    Institute of Scientific and Technical Information of China (English)

    陈文达; 翟大成; 李航

    2011-01-01

    对硫酸渣成球性能进行了研究.对硫酸渣磨矿后,其粒度和成球性能得到很大的改善.通过对硫酸渣球团的落下强度、抗压强度和生球爆裂温度等进行测定,得出在粒度水平(74μm/95.1%)及膨润土为1.0%条件下,硫酸渣的成球性能较好,能够满足冶金工艺的要求.%The bailing pmpenies of pyrite cinder are studied in this paper. AFter grinding on pyrite cinder, particle size and bailing properties are greatlly improved. Through the measuring of drop strength, compressive strength and cracking temperture on pyrite cinder pellet, it is found that the bailing properties of pyrite cinder is best at the level panicle size (74μm95.1%) and 1.0% bentonite, which can meet the requirements of metallurgical technology.

  5. Redox potential (Eh) and anion effects of pyrite (FeS 2 ) leaching at pH 1

    Science.gov (United States)

    Chandra, Anand P.; Gerson, Andrea R.

    2011-11-01

    Pyrite plays the central role in the environmental issue of acid rock drainage. Natural weathering of pyrite results in the release of sulphuric acid which can lead to further leaching of heavy and toxic metals from other associated minerals. Understanding how pyrite reacts in aqueous solution is critical to understanding the natural weathering processes undergone by this mineral. To this end an investigation of the effect of solution redox potential (Eh) and various anions on the rate of pyrite leaching under carefully controlled conditions has been undertaken. Leaching of pyrite has been shown to proceed significantly faster at solution Eh of 900 mV (SHE) than at 700 mV, at pH 1, for the leach media of HCl, H 2SO 4 and HClO 4. The predominant effect of Eh suggests electrochemical control of pyrite leaching with similar mechanism(s) at Eh of 700 and 900 mV albeit with different kinetics. Leach rates at 700 mV were found to decrease according to HClO 4 > HCl > H 2SO 4 while at 900 mV the leach rate order was HCl > HClO 4 > H 2SO 4. Solution Fe 3+ activity is found to continually increase during all leaches; however, this is not accompanied by an increase in leach rate. Synchrotron based photoemission electron microscopy (PEEM) measurements showed a localised distribution of adsorbed and oxidised surface species highlighting that pyrite oxidation and leaching is a highly site specific process mediated by adsorption of oxidants onto specific surface sites. It appears that rates may be controlled, in part, by the propensity of acidic anions to bind to the surface, which varies according to SO42->Cl->ClO4-, thus reducing the reactive or effective surface area. However, anions may also be involved in specific reactions with surface leach products. Stoichiometric dissolution data (Fe/S ratio), XPS and XRD data indicate that the highest leach rates (in HCl media at 900 mV Eh) correlate with relatively lower surface S abundance. Furthermore, there are indications that

  6. A Comprehensive Utilization Process for Black Manganese-silver Ores by Pyrite Reducing Method

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    On a 5 kg bench scale, the separating of Mn-Ag from black manganese-silver ores by pyrite reducing was investigated. Leached Mn content of 98.3% (mass fraction) along with silver loss of 1.5% is achieved. The purification of solution by the precipitation method was effectively used. Chemical grade -MnO2 with TMn content of 60.13% (mass fraction) and MnO2 content of 92.28% (mass fraction) is obtained. Mn recovery efficiency is 94.04%. The residues from leaching Mn process of black Mn-Ag ores was employed for silver extraction by cyanidation with leached silver content of 92.17% (mass fraction), displacement ratio of 99.5%, recovery efficiency of 90.79%. Therefore, the present study provides a feasible process for making full use of black manganese-silver ore resources.

  7. Evaluating structure selection in the hydrothermal growth of FeS2 pyrite and marcasite

    Science.gov (United States)

    Kitchaev, Daniil A.; Ceder, Gerbrand

    2016-12-01

    While the ab initio prediction of the properties of solids and their optimization towards new proposed materials is becoming established, little predictive theory exists as to which metastable materials can be made and how, impeding their experimental realization. Here we propose a quasi-thermodynamic framework for predicting the hydrothermal synthetic accessibility of metastable materials and apply this model to understanding the phase selection between the pyrite and marcasite polymorphs of FeS2. We demonstrate that phase selection in this system can be explained by the surface stability of the two phases as a function of ambient pH within nano-size regimes relevant to nucleation. This result suggests that a first-principles understanding of nano-size phase stability in realistic synthesis environments can serve to explain or predict the synthetic accessibility of structural polymorphs, providing a guideline to experimental synthesis via efficient computational materials design.

  8. Elastic stability and electronic structure of pyrite type PtN2: Ahard semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rong; Zhan, Qian; Zhang, Xiao-Feng

    2006-08-29

    The elastic properties and electronic structure of PtN2 withthe pyrite structure (PtN2(C2)) were studied with first-principlescalculations. The crystal structure is demonstrated to be elasticallystable with a lower energy than the metastable fluorite structureproposed before. The calculated shear modulus of 214 GPa suggests thatPtN2(C2) is harder than some well known hard materials such as TiN andSiC. The high elastic moduli are attributed to a stacking ofcorner-shared PtN6 octahedra bonded by strong N-N covalent bonding. Incontrast to the metallic fluorite-type phase, PtN2(C2) is semiconductingwith an indirect band gap.

  9. Pyrite oxidation and reduction - Molecular orbital theory considerations. [for geochemical redox processes

    Science.gov (United States)

    Luther, George W., III

    1987-01-01

    In this paper, molecular orbital theory is used to explain a heterogeneous reaction mechanism for both pyrite oxidation and reduction. The mechanism demonstrates that the oxidation of FeS2 by Fe(3+) may occur as a result of three important criteria: (1) the presence of a suitable oxidant having a vacant orbital (in case of liquid phase) or site (solid phase) to bind to the FeS2 via sulfur; (2) the initial formation of a persulfido (disulfide) bridge between FeS2 and the oxidant, and (3) an electron transfer from a pi(asterisk) orbital in S2(2-) to a pi or pi(asterisk) orbital of the oxidant.

  10. Density functional calculation of equilibrium geometry and electronic structure of pyrite

    Institute of Scientific and Technical Information of China (English)

    邱冠周; 肖奇; 胡岳华; 徐竞

    2001-01-01

    The equilibrium geometry and electronic structure of pyrite has been studied using self-consistent density-functional theory within the local density approximation (LDA). The optimum bulk geometry is in good agreement with crystallographic data. The calculated band structure and density of states in the region around the Fermi energy show that valence-band maximum (VBM) is at X (100), and the conduction-band minimum (CBM) is at G (000). The indirect and direct band gaps are 0.6eV and 0.74eV, respectively. The calculated contour map of difference of charge density shows excess charge in nonbonding d electron states on the Fe sites. The density increases between sulfur nuclei and between iron and sulfur nuclei qualitatively reveal that S-S bond and Fe-S bond are covalent binding.

  11. Spin-driven symmetry breaking in the frustrated fcc pyrite MnS2.

    Science.gov (United States)

    Kimber, Simon A J; Chatterji, Tapan

    2015-06-10

    We report the characterisation of natural samples of the cubic pyrite mineral MnS2 using very high resolution synchrotron x-ray diffraction techniques. At low temperatures we find a new low temperature polymorph, which results from coupling between magnetic and lattice degrees of freedom. Below the magnetic ordering temperature T(N) = 48 K, we detect a pseudo-tetragonal distortion with a tiny c/a ratio of 1.0006. The structure can be refined in the space group Pbca The symmetry lowering reduces magnetic frustration in the fcc Mn(2+) lattice and is likely responsible for the previously reported lock-in of the magnetic propagation vector. This behaviour is similar to the spin-Peierls phase transitions reported in other three-dimensional Heisenberg magnets like the chromate spinels.

  12. Near infrared to ultraviolet optical properties of bulk single crystal and nanocrystal thin film iron pyrite

    Science.gov (United States)

    Subedi, Indra; Bhandari, Khagendra P.; Ellingson, Randall J.; Podraza, Nikolas J.

    2016-07-01

    We report optical properties of iron pyrite (FeS2) determined from ex situ spectroscopic ellipsometry measurements made on both a commercially available bulk single crystal and nanocrystalline thin film over a spectral range of 0.735-5.887 eV. The complex dielectric function, ɛ (E) = ɛ 1 (E) + iɛ 2 (E), spectra have been determined by fitting a layered parametric model to the ellipsometric measurements. Spectra in ɛ are modeled using a Kramers-Kronig consistent critical point parabolic band model involving seven critical points for the bulk single crystal and four critical points for the nanocrystalline film. Absorption coefficient spectra for both types of samples are also determined from ɛ. Critical point features in the nanocrystalline films are broader, have lower amplitude and lower energy critical points detected having a small blue shift when compared to the single crystal sample.

  13. Metalloproteins and the Pyrite-based Origin of Life: A Critical Assessment

    Science.gov (United States)

    Rivas, Mario; Becerra, Arturo; Peretó, Juli; Bada, Jeffrey L.; Lazcano, Antonio

    2011-08-01

    We critically examine the proposal by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that putative transition metal binding sites in protein components of the translation machinery of hyperthermophiles provide evidence of a direct relationship with the FeS clusters of pyrite and thus indicate an autotrophic origin of life in volcanic environments. Analysis of completely sequenced cellular genomes of Bacteria, Archaea and Eucarya does not support the suggestion by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that aminoacyl-tRNA synthetases and ribosomal proteins bear sequence signatures typical of strong covalent metal bonding whose absence in mesophilic species reveals a process of adaptation towards less extreme environments.

  14. The volcanic-sedimentary sequence of the Lousal deposit, Iberian Pyrite Belt (Portugal)

    Science.gov (United States)

    Rosa, Carlos; Rosa, Diogo; Matos, Joao; Relvas, Jorge

    2010-05-01

    The Iberian Pyrite Belt (IPB) is a massive sulfide province that is located in the south of Portugal and Spain, and hosts more than 90 massive sulfide deposits that amount to more than 1850 million metric tonnes of sulfide ore (Tornos, 2006). The ore deposits size, vary from ~1Mt to >100Mt (e.g. Neves Corvo and Aljustrel in Portugal, and Rio Tinto and Tharsis in Spain). The ore deposits are hosted by a submarine sedimentary and volcanic, felsic dominated, succession that constitutes the Upper Devonian to Lower Carboniferous Volcanic and Sedimentary Complex (VSC). The VSC ranges in thickness from approximately 600 to 1300 m (Tornos 2006). The VSC overlies the Phyllite-Quartzite Group (PQ) (Upper Devonian, base unknown) and is overlain by the Baixo Alentejo Flysch Group (Lower to Upper Carboniferous). The Lousal massive sulfide deposit is located in the western part of the IPB and occurs mostly interbedded with black mudstone. The VSC sequence at Lousal mine consists of a mudstone and quartzite sequence (PQ Group) in the lower part of the succession, over which a thick sequence of rhyolitic lavas (>300 m) occurs. Above the rhyolitic lavas there is a thick sequence of black and grey mudstone that hosts the massive sulfide ore bodies, and a rhyolitic sill. The upper part of the VSC sequence consists of a thick mudstone interval that hosts two thick basaltic units, locally with pillows. The rhyolites have small coherent cores, locally with flow bands, that grade to surrounding massive clastic intervals, with large lateral extent. The clasts show jigsaw-fit arrangement in many places and have planar or curviplanar margins and locally are perlitic at the margin. The top contact of these units is in most locations not exposed, which makes difficult to interpret the mode of emplacement. However, the thick clastic intervals, above described, are in accordance with quenching of volcanic glass with abundant water and therefore indicate that quenching of the rhyolites was the

  15. The role of isomorphous substitutions in natural selenides belonging to the pyrite group

    Energy Technology Data Exchange (ETDEWEB)

    Bindi, Luca [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy)], E-mail: luca.bindi@unifi.it; Cipriani, Curzio [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Pratesi, Giovanni [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Dipartimento di Scienze della Terra, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Trosti-Ferroni, Renza [Dipartimento di Scienze della Terra, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy)

    2008-07-14

    The present paper reports chemical and structural data of selenide minerals belonging to the pyrite group. Eighteen samples of minerals in this group with variable chemical composition (7 samples of penroseite, NiSe{sub 2}; 10 samples of krutaite, CuSe{sub 2}; 1 sample of trogtalite, CoSe{sub 2}) were studied by means of X-ray single-crystal diffraction and electron microprobe. On the basis of information gained from the chemical characterization, we can conclude that a complete solid solution between NiSe{sub 2} and CuSe{sub 2} exists in nature with the absence of pure end-members. Although verified only for the Ni-rich members, we also infer a solid solution between NiSe{sub 2} and CoSe{sub 2}. The unit-cell parameters were modeled using a multiple regression method as a function of the Co, Ni, and Cu contents.

  16. Transport and degradation of chlorofluorocarbons (CFCs) in the pyritic Rabis Creek aquifer, Denmark

    Science.gov (United States)

    Hinsby, K.; Hojberg, A.L.; Engesgaard, P.; Jensen, K.H.; Larsen, F.; Plummer, L.N.; Busenberg, E.

    2007-01-01

    Vertical profiles of the chlorofluorocarbons CFC-11, CFC-12, and CFC-113 penetrating aerobic and anaerobic parts of a shallow sandy aquifer show that the CFC gases are degraded in the groundwater in a pyritic sand aquifer at Rabis Creek, Denmark. Two-dimensional solute transport simulations with either zero-order or first-order degradation in the anaerobic zone corroborate this interpretation. The transport model was previously calibrated against detailed tritium profiles in the same wells. First-order degradation is found to best match the observed CFC profiles yielding an approximate half-life of a few months for CFC-11. Degradation is not as clearly recognized for CFC-12 and CFC-113, but it may occur with rates corresponding to a half-life of a few years or more. Data indicate a geochemical control of the CFC concentration gradient at the redox front and that denitrification and denitrifiers are not of major importance for the observed CFC degradation. The responsible mechanism behind the observed degradation is not known but we suggest that reductive dehalogenation by surface-bound Fe(II) on pyrite possibly enhanced by the presence of Fe(III)-bearing weathering products (green rust) may be a plausible mechanism. The observed data and the performed simulations confirm the potential application of the CFC gases as age-dating tools in the aerobic part of the investigated aquifer, but also that CFC data must be analyzed carefully before it is used as a dating tool in reducing aquifers because degradation may have occurred. The use of multiple or alternative tracers should be considered in anaerobic environments. Copyright 2007 by the American Geophysical Union.

  17. Natural Monocrystalline Pyrite as Sensor for Potentiometric Redox Titrations. Part I. Titrations with Permanganate

    Directory of Open Access Journals (Sweden)

    B. V. Vukanovic

    2002-04-01

    Full Text Available Results obtained in potentiometric titrations of Fe(II, Mn(II, Fe(CN64-, C2O42- and As(III with standard potassium permanganate solution, are presented. The titration end point (TEP was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III were carried out in HCl (1.2 M and H2SO4 solutions (0.1- 4.5 M, whereas oxalate was determined in H2SO4 (0.1-4.5 M. Iron(II and hexacyanoferrate(II were titrated in H2SO4 and also in H3PO4 solutions (0.1-4.5 M. The titrations of Mn(II were performed in H2P2O72- media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II in H3PO4 (240-330 mV/0.1 mL. Reversed titrations were also performed and accurate and reproducible results were obtained.

  18. Trace elements contamination of agricultural soils affected by sulphide exploitation (Iberian Pyrite Belt, Sw Spain)

    Science.gov (United States)

    López, María; González, Isabel; Romero, Antonio

    2008-04-01

    Agricultural soils of the Riotinto mining area (Iberian Pyrite Belt) have been studied to assess the degree of pollution by trace elements as a consequence of the extraction and treatment of sulphides. Fifteen soil samples were collected and analysed by ICP-OES and INAA for 51 elements. Chemical analyses showed an As-Cu-Pb-Zn association related with the mineralisation of the Iberian Pyrite Belt. Concentrations were 19-994 mg kg-1 for As, 41-4,890 mg kg-1 for Pb, 95-897 mg kg-1 for Zn and of 27-1,160 mg kg-1 for Cu. Most of the samples displayed concentrations of these elements higher than the 90th percentile of the corresponding geological dominium, which suggests an anthropogenic input besides the bedrock influence. Samples collected from sediments were more contaminated than leptosols because they were polluted by leachates or by mining spills coming from the waste rock piles. The weathering of the bedrock is responsible for high concentrations in Co, Cr and Ni, but an anthropogenic input, such as wind-blown dust, seems to be indicative of the high content of As, Cu, Pb and Zn in leptosols. The metal partitioning patterns show that most trace elements are associated with Fe amorphous oxy-hydroxides, or take part of the residual fraction. According to the results obtained, the following mobility sequence is proposed for major and minor elements: Mn, Pb, Cd, > Zn, Cu > Ni > As > Fe > Cr. The high mobility of Pb, Cu and Zn involve an environmental risk in this area, even in soils where the concentrations are not so high.

  19. Extracting gold from pyrite roster cinder by ultra-fine-grinding and resin-in-pulp

    Institute of Scientific and Technical Information of China (English)

    危俊婷; 严规有; 郭炳昆; 高桂兰

    2003-01-01

    The ultra-fine-grinding and resin-in-pulp with pH value of 10 are used to extract gold from pyrite roster cinder. During leaching process, aluminium oxide ball is used as stirring medium, hydrogen peroxide as leaching agent and sodium hexametaphosphate as grinding agent. With AM-26 resin as absorber and sulfocarbamide as eluent, gold is recovered from cyanide pulp of pyrite roster cinder by resin-in-pulp. The effects of contact time, temperature and acidity etc. on the gold absorption are investigated by static methods and dynamic method respectively. The effects of flow rate of solution on dynamic adsorption and elution of gold are studied. The results show that AM-26 resin has good adsorbability in cyanide solution, and gold can be easily eluated from the loaded resin with 0. 1mol/L hydrochloric acid and lmol/L sulfocabamide. The adsorption rate and the elution of gold exceed 98%. When leaching time is 2 h, mass ratio of liquid to solid 4: 1, consumption of sodium cyanide 3 kg/t, concentration of hydrogen peroxide and sodium hexametaphosphate 0. 05% respectively, adsorption time 30 min, temperature 10-30 ℃, volume of resin 3 mL, ratio of eluent to resin (10-20): 1, velocity of eluent 1.5 mL/min, the leaching rate of gold reaches 85%. Compared with traditional leaching technology, it can reduce leaching time, avoid complex filter process, decrease sodium cyanide consumption and increase leaching rate of gold by 35%.

  20. Phase Stability and Stoichiometry in Thin Film Iron Pyrite: Impact on Electronic Transport Properties.

    Science.gov (United States)

    Zhang, Xin; Scott, Tom; Socha, Tyler; Nielsen, David; Manno, Michael; Johnson, Melissa; Yan, Yuqi; Losovyj, Yaroslav; Dowben, Peter; Aydil, Eray S; Leighton, Chris

    2015-07-01

    The use of pyrite FeS2 as an earth-abundant, low-cost, nontoxic thin film photovoltaic hinges on improved understanding and control of certain physical and chemical properties. Phase stability, phase purity, stoichiometry, and defects, are central in this respect, as they are frequently implicated in poor solar cell performance. Here, phase-pure polycrystalline pyrite FeS2 films, synthesized by ex situ sulfidation, are subject to systematic reduction by vacuum annealing (to 550 °C) to assess phase stability, stoichiometry evolution, and their impact on transport. Bulk probes reveal the onset of pyrrhotite (Fe(1-δ)S) around 400 °C, rapidly evolving into the majority phase by 425 °C. This is supported by X-ray photoelectron spectroscopy on (001) crystals, revealing surface Fe(1-δ)S formation as low as 160 °C, with rapid growth near 400 °C. The impact on transport is dramatic, with Fe(1-δ)S minority phases leading to a crossover from diffusive transport to hopping (due to conductive Fe(1-δ)S nanoregions in an FeS2 matrix), followed by metallicity when Fe(1-δ)S dominates. Notably, the crossover to hopping leads to an inversion of the sign, and a large decrease in magnitude of the Hall coefficient. By tracking resistivity, magnetotransport, magnetization, and structural/chemical parameters vs annealing, we provide a detailed picture of the evolution in properties with stoichiometry. A strong propensity for S-deficient minority phase formation is found, with no wide window where S vacancies control the FeS2 carrier density. These findings have important implications for FeS2 solar cell development, emphasizing the need for (a) nanoscale chemical homogeneity, and (b) caution in interpreting carrier types and densities.

  1. Pyrite oxidation in the presence of hematite and alumina: II. Effects on the cathodic and anodic half-cell reactions.

    Science.gov (United States)

    Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi

    2017-03-01

    The oxidative dissolution of pyrite is an important process in the redox recycling of iron (Fe) and is well-known for its role in the formation of acid mine drainage (AMD), which is considered as the most serious and widespread problem after the closure of mines and mineral processing operations. Because this process requires the movement of electrons, common metal oxides in nature that have either semiconducting (e.g., hematite) or insulating (e.g., alumina) properties may have strong effects on it. In this study, changes in the electrochemical behavior of pyrite in the presence of hematite and alumina were investigated. Results showed that the formation of surface-bound species directly influenced the anodic and cathodic half-cell reactions as well as the transfer of electrons between these sites. Pyrite pretreated in the air became anodically more reactive than that pretreated in oxygenated water, but the type of oxidizing media had little effect on the cathodic half-cell reaction. The presence of hematite and alumina during pretreatment also had strong effects on the electrochemical properties of pyrite. Chronoamperometry measurements suggest that hematite and alumina enhanced the anodic half-cell reaction but suppressed the cathodic half-cell reaction of pyrite oxidation. Increased anodic half-cell reaction in the presence of hematite could be attributed to electron "bridging" and catalytic effects of this mineral. In contrast, the effects of alumina on the anodic half-cell reaction were indirect and could be explained by the formation of Fe(3+)-oxyhydroxide surface species during pretreatment. Suppression of the cathodic half-cell reaction by both minerals was attributed to their "protective" effect on cathodic sites. Our results also point to the cathodic half-cell reaction as the rate determining-step of the overall oxidative dissolution process.

  2. Stratigraphic and micropetrographic occurrences of pyrite in sediments at the confluence of carbonate and peat-forming depositional systems, southern Florida, USA

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.E.; Cohen, A.D. (University of South Carolina, Columbia, SC (United States). Dept. of Geological Sciences)

    1995-01-01

    This study was undertaken to investigate peat/carbonate relationships in a modern coal-forming setting, with initial research on pyrite and sulfur contents relative to stratigraphic and petrographic conditions. Over 40 closely spaced cores were taken from transects from Florida Bay inland through mangrove swamps and freshwater Everglades. Core stratigraphy confirms an overall transgressive sequence, but new evidence supports a small regression within the overall transgression. On average, both total S and pyrite are lowest at inland sites, highest near the coastline, and intermediate in Florida Bay sediments. Total S is higher in marine than freshwater peats, but freshwater peats overlain by marine peats are enriched in S. In cores that start with peat at the top, pyrite is generally absent or very low in the top 20 cm. Higher percentages of pyrite occur in carbonate rather than peat facies. Pyrite exists in three forms, framboidal aggregates, minute crystals, and large solitary crystals. Most of the pyrite occurs as minute crystals ([lt]2[mu]m) and framboidal aggregates. The occurrence of large crystals ([gt]2[mu]m) is less common and generally restricted to the cavities of larger cells or cavities within other organics (e.g. foraminifer, pollen grains, fungal sclerotia). A general relationship seems to exist in certain cases between the occurrence of spherical organic cell fillings and the occurrence of the framboidal form of pyrite. 37 refs., 20 figs., 2 tabs.

  3. Solution-based Syntheses of Iron Pyrite Thin Films for Photovoltaic and Protein Foot-printing Applications

    Science.gov (United States)

    El Makkaoui, Mohammed

    Iron pyrite (cubic FeS2) is a non-toxic, earth abundant semiconductor possessing a set of excellent optical/electronic properties for serving as an absorber layer in PV devices. Additionally, pyrite is a very efficient hydroxyl radical generator via Fenton chemistry and has shown promise in oxidative protein and DNA foot-printing application. The main focus of this thesis is on fabricating phase and elementally pure iron pyrite thin films using a solution-based approach that employs hydrazine as a solvent. A precursor ink is formed at room temperature by mixing elemental iron and sulfur in anhydrous hydrazine and then deposited on Mo-coated glass substrates, via spin coating, to yield amorphous iron sulfide films that are then annealed in H2S (340°C) and sulfur gas (≤ 500 °C) to form uniform, polycrystalline and phase pure pyrite films with densely packed grains. This approach is likely to yield the most elementally pure pyrite thin films made to date, through a very simple and scalable process. The ink has shown to be very sensitive to environmental conditions and has a very short shelf life (˜1 day). Additionally, the film microstructure is greatly influenced by the S:Fe concentration ratio that when tuned to 3:1, yielded uniform, robust and optically flat iron sulfide thin films with an optimal thickness (˜320 nm) for PV application. The results however were not reproducible, mainly due to failure in applying multiple layers without compromising film morphology. Thinner (films, on the other hand, are reproducibly produced, but are too thin to be employed in PV devices. Direct annealing in sulfur gas at 475°C for 4 hours, bypassing the > 12 hour H2S annealing step, yielded phase pure pyrite films, with good morphology, at lower processing time and annealing temperatures (polymer laminates for protein foot-printing application in collaboration with the Brenowitz lab at the Albert Einstein College of Medicine and the Khine lab at the University of California

  4. Chemical and sulphur isotope compositions of pyrite in the Jaduguda U (-Cu-Fe) deposit, Singhbhum shear zone, eastern India: Implications for sulphide mineralization

    Science.gov (United States)

    Pal, Dipak C.; Sarkar, Surajit; Mishra, Biswajit; Sarangi, A. K.

    2011-06-01

    The Jaduguda U (-Cu-Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A - high Co (up to 30800 ppm), no/low Ni; type-B - moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type-C - no/low Co and high Ni (up to 43000 ppm); type-D - neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06‰. Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0‰. By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone.

  5. Chemical and sulphur isotope compositions of pyrite in the Jaduguda U (–Cu–Fe) deposit, Singhbhum shear zone, eastern India: Implications for sulphide mineralization

    Indian Academy of Sciences (India)

    Dipak C Pal; Surajit Sarkar; Biswajit Mishra; A K Sarangi

    2011-06-01

    The Jaduguda U (–Cu–Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A — high Co (up to 30800 ppm), no/low Ni; type-B — moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type-C — no/low Co and high Ni (up to 43000 ppm); type-D — neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06%. Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0. By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone.

  6. Hydrochemical and stable isotope indicators of pyrite oxidation in carbonate-rich environment; the Hamersley Basin, Western Australia

    Science.gov (United States)

    Dogramaci, Shawan; McLean, Laura; Skrzypek, Grzegorz

    2017-02-01

    Sulphur (S) is a commonly occurring element in most aquifers, primarily in oxidised (sulphates) and reduced (sulphides) forms. Sulphides often constitute a risk to groundwater quality due to acid rock drainage, especially in catchments that are subject to mining excavations or groundwater injection. However, in semi-arid regions detection of the acid rock drainage risk can be challenging and traditional methods based on observations of increasing SO4 concentrations or SO4/Cl ratios in surface and groundwater, are not necessarily applicable. In addition, decreasing pH, usually accompanying pyrite oxidation, can be masked by the high pH-neutralisation capacity of carbonate and silicate minerals. Analysis of 73 surface and groundwater samples from different water bodies and aquifers located in the Hamersley Basin, Western Australia found that most of the samples are characterised by neutral pH but there was also a large spatial variability in the dissolved sulphate (SO4) concentrations that ranged from 1 mg/L to 15,000 mg/L. Not surprisingly, groundwater in aquifers that contained pyrite had high sulphate concentrations (>1000 mg/L). This was associated with low δ34SSO4 values (+1.2‰ to +4.6‰) and was consistent with the values obtained from aquifer matrix pyritic rock samples (-1.9‰ to +4.4‰). It was also found that the SO4 concentrations and acidity levels were not only dependent on δ34SSO4 values and existence of pyrite but also on the presence of carbonate minerals in the aquifer matrix. The groundwater in aquifers containing both pyrite and carbonate minerals had a neutral pH and was also saturated with respect to gypsum and had high magnesium concentrations of up to 2200 mg/L suggesting de-dolomitisation as the process buffering the acidity generated by pyrite oxidation. Based on the findings from this study, a classification scheme has been developed for identification of the acid rock drainage contribution to groundwater that encompasses a myriad of

  7. 云浮硫铁矿及其焙烧灰渣中元素铊的组成特征%Distribution of Thallium in Pyrite Ores and Its Cinders of Yunfu Pyrite Mine,Guangdong

    Institute of Scientific and Technical Information of China (English)

    谢文彪; 陈永亨; 陈穗玲; 王甘霖; 常向阳

    2001-01-01

    本文研究了铊元素在云浮硫铁矿矿石及其焙烧灰和渣中的含量特征,并探讨了矿山开采和资源利用过程中产生的含铊废弃物对环境的影响。表明进一步开展相关的资源综合利用研究和废弃物综合治理研究是十分必要的。%In this paper,the content and distribution of thallium in pyrite ore,ash and cinder is studied.The effect of thallium in ore and cinder on environment is also approached.The study shows that it is necessary to research comprehensive utilization methods of this type of resources and complex harnessing way of pyrite ash and cinder.

  8. Mineralization and trace element distribution in pyrite using EMPA in exploration drill holes from Cheshmeh Zard gold district, Khorasan Razavi Province, Iran

    Directory of Open Access Journals (Sweden)

    Zahra Alaminia

    2015-10-01

    Full Text Available Introduction Pyrite is the most abundant sulfide mineral in low sulfidation ore deposits. Experimental studies have shown that low-temperature ( 200°C from hydrothermal or metamorphic fluids (Butler and Rickard, 2000. Framboidal pyrite mostly occurs in sedimentary environments, though it could also form during metamorphism and hydrothermal alteration (Scott et al., 2009. The pyrite formed tends to be enriched in various trace elements such as Au and As. For this study we have combined the geology, alteration, mineralization with recent studies of the description of the deposit from core logging and underground mapping and geochemistry in the CheshmehZard gold district and also investigated the compositional variation and textural differences between pyrite types. This study is based on the results of our alteration and mineralization mapping and detailed logging of 1937.8 m of drill core. Materials and Methods Geology, hydrothermal alteration and mineralization were examined in drill holes along several cross sections. Host-rock alteration minerals and veins were determined for 11 samples using standard X-ray diffraction (XRD and X-ray fluorescence spectrometry (XRF techniques. Polished sections were studied by reflected light microscopy and backscattered electron images (BSE. In this study, the trace-element composition of pyrite samples from the Au-III vein system was obtained using electron microprobe analyzer (EMPA data. All analyseswere carried out at the department of Materials Engineering and Physics of the University of Salzburg in Austria. The EMPA measurements and BSE imaging were made using a JXA-8600 electron microprobe. Spot analyses of 30 pyrite grains from CheshmehZard are given in Table 1. Results The study area is located in the north of Khorasan Razavi Province 45 km to the south of Neyshabour. The area near CheshmehZard could become important as a site of economically significant gold mineralization. Six gold-bearing vein

  9. Peptide synthesis in aqueous environments: the role of extreme conditions and pyrite mineral surfaces on formation and hydrolysis of peptides.

    Science.gov (United States)

    Schreiner, Eduard; Nair, Nisanth N; Wittekindt, Carsten; Marx, Dominik

    2011-06-01

    A comprehensive study of free energy landscapes and mechanisms of COS-mediated polymerization of glycine via N-carboxy anhydrides (NCAs, "Leuchs anhydrides") and peptide hydrolysis at the water-pyrite interface at extreme thermodynamic conditions is presented. Particular emphasis is set on the catalytic effects of the mineral surface including the putative role of the ubiquitous sulfur vacancy defects. It is found that the mere presence of a surface is able to change the free energetics of the elementary reaction steps. This effect can be understood in terms of a reduction of entropic contributions to the reactant state by immobilizing the reactants and/or screening them from bulk water in a purely geometric ("steric") sense. Additionally, the pyrite directly participates chemically in some of the reaction steps, thus changing the reaction mechanism qualitatively compared to the situation in bulk water. First, the adsorption of reactants on the surface can preform a product-like structure due to immobilizing and scaffolding them appropriately. Second, pyrite can act as a proton acceptor, thus replacing water in this role. Third, sulfur vacancies are found to increase the reactivity of the surface. The finding that the presence of pyrite speeds up the rate-determining step in the formation of peptides with respect to the situation in bulk solvent while stabilizing the produced peptide against hydrolysis is of particular interest to the hypothesis of prebiotic peptide formation at hydrothermal aqueous conditions. Apart from these implications, the generality of the studied organic reactions are of immediate relevance to many fields such as (bio)geochemistry, biomineralization, and environmental chemistry.

  10. Pyrite framboids associated with the Mesozoic Jehol Biota in northeastern China: Implications for microenvironment during early fossilization

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Despite of the recent influx of reports describing important fossil specimens from the Mesozoic Jehol Biota, detailed information on the mechanism of fossilization and paleoenvironment in which these fossils were deposited is scanty. We present an analysis of microenvironment based upon scanning electron microscope observations of in situ pyrite framboids and microcrystallines of plant and vertebrate feather fossils in the Jehol Biota. Pyrite microcrystallines and framboids occur extensively inside and on surface of plant fossils.Framboids found on feathers and in sedimentary matrix were in a lower abundance. These framboids have diameters ranging from 6 μm to 31 μm with an average of 20 μm, indicating a dysoxic aqueous condition with free oxygen level less than 30 μmol/L for the microenvironment where these framboids were formed. The outgrowth of framboids inside plant tissues suggests the presence of water molecules and free oxygen at the cellular level during pyritization; the relative timing between tissue decay and framboid formation implies a rapid tissue degradation occurred during the very early stage of fossilization. This line of reasoning is consistent with the observation that cell level structure of plant fossils from these deposits is rarely preserved. We propose a "fossil envelop" model to accommodate the different geochemical conditions between the microenvironment surrounding the fossil material and the macroenvironment of background lake bottom water.

  11. Deep subsurface sulfate reduction and methanogenesis in the Iberian Pyrite Belt revealed through geochemistry and molecular biomarkers.

    Science.gov (United States)

    Puente-Sánchez, F; Moreno-Paz, M; Rivas, L A; Cruz-Gil, P; García-Villadangos, M; Gómez, M J; Postigo, M; Garrido, P; González-Toril, E; Briones, C; Fernández-Remolar, D; Stoker, C; Amils, R; Parro, V

    2014-01-01

    The Iberian Pyrite Belt (IPB, southwest of Spain), the largest known massive sulfide deposit, fuels a rich chemolithotrophic microbial community in the Río Tinto area. However, the geomicrobiology of its deep subsurface is still unexplored. Herein, we report on the geochemistry and prokaryotic diversity in the subsurface (down to a depth of 166 m) of the Iberian Pyritic belt using an array of geochemical and complementary molecular ecology techniques. Using an antibody microarray, we detected polymeric biomarkers (lipoteichoic acids and peptidoglycan) from Gram-positive bacteria throughout the borehole. DNA microarray hybridization confirmed the presence of members of methane oxidizers, sulfate-reducers, metal and sulfur oxidizers, and methanogenic Euryarchaeota. DNA sequences from denitrifying and hydrogenotrophic bacteria were also identified. FISH hybridization revealed live bacterial clusters associated with microniches on mineral surfaces. These results, together with measures of the geochemical parameters in the borehole, allowed us to create a preliminary scheme of the biogeochemical processes that could be operating in the deep subsurface of the Iberian Pyrite Belt, including microbial metabolisms such as sulfate reduction, methanogenesis and anaerobic methane oxidation. © 2013 John Wiley & Sons Ltd.

  12. Thermal-sprayed, thin-film pyrite cathodes for thermal batteries -- Discharge-rate and temperature studies in single cells

    Energy Technology Data Exchange (ETDEWEB)

    GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W.; DAI,JINXIANG; XIAO,T. DANNY; REISNER,DAVID

    2000-05-25

    Using an optimized thermal-spray process, coherent, dense deposits of pyrite (FeS{sub 2}) with good adhesion were formed on 304 stainless steel substrates (current collectors). After leaching with CS{sub 2} to remove residual free sulfur, these served as cathodes in Li(Si)/FeS{sub 2} thermal cells. The cells were tested over a temperature range of 450 C to 550 C under baseline loads of 125 and 250 mA/cm{sup 2}, to simulate conditions found in a thermal battery. Cells built with such cathodes outperformed standard cells made with pressed-powder parts. They showed lower interracial resistance and polarization throughout discharge, with higher capacities per mass of pyrite. Post-treatment of the cathodes with Li{sub 2}O coatings at levels of >7% by weight of the pyrite was found to eliminate the voltage transient normally observed for these materials. Results equivalent to those of standard lithiated catholytes were obtained in this manner. The use of plasma-sprayed cathodes allows the use of much thinner cells for thermal batteries since only enough material needs to be deposited as the capacity requirements of a given application demand.

  13. Application of the pyrite ash in the microwave Fenton process of decolorization of the synthetic color solution

    Directory of Open Access Journals (Sweden)

    Bečelić-Tomin Milena R.

    2013-01-01

    Full Text Available The aim of this study is to investigate the possibility of fly ash and pyrite ash applications as a Fenton catalysts in the advancement of the microwave/hydrogen peroxide (MW/H2O2 treatment in the Rhodamine B decolorization process. At the same time, a comparison of the influence of these heterogenous catalysts with the homogenous Fenton catalyst on the decolorization process was conducted. The influence of the catalyst was tracked in previously optimized conditions MW/H2O2: [Rhodamine B] = 0.2 mM; pH 3.2; temperature 85ºC; [H2O2] = 80 mM; power = 300 W. Under such conditions, the efficiency of 99.5% was achieved after 30 minutes of reaction time. The same efficiency was achieved through the application of MW/Fe2+/H2O2 and MW/pyrite ash/H2O2 after only 10 minutes of reaction time. The order of the tested integrated processes according to the initial reaction rate is as follows: MW/Fe2+/H2O2>MW/fly ash/H2O2>MW/H2O2. The results of this study present a basis for further research and optimization of water solution decolorization process through pyrite ash with MW and hydrogen peroxide application.

  14. An Innovative Approach to Separate Iron Oxide Concentrate from High-sulfur and Low-grade Pyrite Cinders

    Institute of Scientific and Technical Information of China (English)

    Yong LI; Fu-chun ZHOU; Zhao-xin ZHOU; Zhi-han TIAN; Chao YANG; Xi-ke TIAN

    2016-01-01

    High-sulfur and low-grade pyrite cinders are the waste products of sulfuric acid manufacturing plants. Many valuable components,such as iron oxide,are contained in pyrite cinders and difficult to be separated and puri-fied j ust via the high temperature roasting process.Considering this,an innovative method including water-washing, aqua regia leaching,hydrothermal alkali activation and acid-washing was developed.And the effects of different pa-rameters on recovery efficiency of iron oxide were systematically investigated.The optimum parameters were pro-posed as follows:water rinse-leaching at room temperature for 5-20 min,and melting at 160 ℃ for 2.0 h with NaOH (concentration of 30 mass%),followed by leaching with aqua regia solution (3.0 vol.%)for 1.0 h.After the treatment,the content of iron oxides increased from 54.3 to 96.0 mass% with the recovery rate exceeding 85%. Meanwhile,calcium sulphate was recovered as the high value-added products by alkali extraction liquid.Further-more,the phase transformation and microstructure of the samples in the process were studied by physicochemical methods to reveal the separation mechanisms of different components in the pyrite cinders.

  15. Single grain Rb-Sr dating of euhedral and cataclastic pyrite from the Qiyugou gold deposit in western Henan,central China

    Institute of Scientific and Technical Information of China (English)

    HAN YiGui; LI XiangHui; ZHANG ShiHong; ZHANG YuanHou; CHEN FuKun

    2007-01-01

    The Rb-Sr isotopic dating of pyrite mineral from ore deposits can directly provide mineralization age. However,many geological factors may affect the Rb-Sr isotopic system,which baffles application of this method. Employing ultra-low procedural blank Rb-Sr method,we have dated pyrites separated from the No. 4 breccia pipe of the Qiyugou gold deposit,western Henan Province. Single grains of euhedral pyrite crystal with few micro-cracks yield an isochron age of 126 ± 11 Ma,which represents time of the main mineralization stage of the deposit. Pyrite grains of cataclastic type show nevertheless scattered Rb-Sr isotopic composition and no reasonable isochron can be defined. Crystal morphology and mineral inclusion studies reveal that Rb and Sr of pyrite mineral probably are preserved mainly in biotite,K-feldspar,and sericite mineral inclusions. The dating results likely suggest that cataclastic pyrite is not suitable for the Rb-Sr dating due to modification of the Rb-Sr isotopic system by later hydrothermal activity of fluid.

  16. Quantifying Fenton reaction pathways driven by self-generated H2O2 on pyrite surfaces

    Science.gov (United States)

    Gil-Lozano, C.; Davila, A. F.; Losa-Adams, E.; Fairén, A. G.; Gago-Duport, L.

    2017-03-01

    Oxidation of pyrite (FeS2) plays a significant role in the redox cycling of iron and sulfur on Earth and is the primary cause of acid mine drainage (AMD). It has been established that this process involves multi-step electron-transfer reactions between surface defects and adsorbed O2 and H2O, releasing sulfoxy species (e.g., S2O32-, SO42-) and ferrous iron (Fe2+) to the solution and also producing intermediate by-products, such as hydrogen peroxide (H2O2) and other reactive oxygen species (ROS), however, our understanding of the kinetics of these transient species is still limited. We investigated the kinetics of H2O2 formation in aqueous suspensions of FeS2 microparticles by monitoring, in real time, the H2O2 and dissolved O2 concentration under oxic and anoxic conditions using amperometric microsensors. Additional spectroscopic and structural analyses were done to track the dependencies between the process of FeS2 dissolution and the degradation of H2O2 through the Fenton reaction. Based on our experimental results, we built a kinetic model which explains the observed trend of H2O2, showing that FeS2 dissolution can act as a natural Fenton reagent, influencing the oxidation of third-party species during the long term evolution of geochemical systems, even in oxygen-limited environments.

  17. Mycorrhizal Fungal Community of Poplars Growing on Pyrite Tailings Contaminated Site near the River Timok

    Directory of Open Access Journals (Sweden)

    Marina Katanić

    2015-06-01

    Full Text Available Background and Purpose: Mycorrhizal fungi are of high importance for functioning of forest ecosystems and they could be used as indicators of environmental stress. The aim of this research was to analyze ectomycorrhizal community structure and to determine root colonization rate with ectomycorrhizal, arbuscular mycorrhizal and endophytic fungi of poplars growing on pyrite tailings contaminated site near the river Timok (Eastern Serbia. Materials and Methods: Identification of ectomycorrhizal types was performed by combining morphological and anatomical characterization of ectomycorrhizae with molecular identification approach, based on sequencing of the nuclear ITS rRNA region. Also, colonization of poplar roots with ectomycorrhizal, arbuscular mycorrhizal and dark septated endophytic fungi were analysed with intersection method. Results and Conclusions: Physico-chemical analyses of soil from studied site showed unfavourable water properties of soil, relatively low pH and high content of heavy metals (copper and zinc. In investigated samples only four different ectomycorrhizal fungi were found. To the species level were identified Thelephora terrestris and Tomentella ellisi, while two types remained unidentified. Type Thelephora terrestris made up 89% of all ectomycorrhizal roots on studied site. Consequently total values of Species richness index and Shannon-Weaver diversity index were 0.80 and 0.43, respectively. No structures of arbuscular mycorrhizal fungi were recorded. Unfavourable environmental conditions prevailing on investigated site caused decrease of ectomycorrhizal types diversity. Our findings point out that mycorrhyzal fungal community could be used as an appropriate indicator of environmental changes.

  18. Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings

    Energy Technology Data Exchange (ETDEWEB)

    Simon, M. [Departamento de Edafologia, EPS-CITE IIB, Canada San Urbano, Universidad de Almeria, 04120 Almeria (Spain)]. E-mail: msimon@ual.es; Martin, F. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain); Garcia, I. [Departamento de Edafologia, EPS-CITE IIB, Canada San Urbano, Universidad de Almeria, 04120 Almeria (Spain); Bouza, P. [Centro Nacional Patagonico, CONICEF, Boulevard Brown s/n, 9120 Puerto Madryn, Chubut (Argentina); Dorronsoro, C. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain); Aguilar, J. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain)

    2005-05-01

    To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed. - Basaluminite, schwertmannite and jarosite armored the limestone grains, and almost all trace elements co-precipitated, but the precipitation of As and Pb tended to decrease as the pH rose.

  19. Leachability and physical stability of solidified and stabilized pyrite cinder sludge from dye effluent treatment

    Directory of Open Access Journals (Sweden)

    Kerkez Đurđa V.

    2015-01-01

    Full Text Available This work is concerned with exploring the possibilities of using solidification/stabilization (S/S treatment for toxic sludge generated in dye effluent treatment, when pyrite cinder is used as catalytic iron source in the modified heterogeneous Fenton process. S/S treatment was performed by using different clay materials (kaolin, bentonite and native clay from the territory of Vojvodina and fly ash in order to immobilize toxic metals and arsenic presented in sludge. For the evaluation of the extraction potential of toxic metals and the effectiveness of the S/S treatment applied, four single-step leaching tests were performed. Leaching test results indicated that all applied S/S treatments were effective in immobilizing toxic metals and arsenic presented in sludge. X-ray diffraction analysis confirmed the formation of pozzolanic products, and compressive strength measurement proved the treatment efficacy. It can be concluded that the S/S technique has significant potential for solving the problem of hazardous industrial waste and its safe disposal. [Projekat Ministarstva nauke Republike Srbije, br. III43005 i br. TR37004

  20. Phytoremediation trials on metal- and arsenic-contaminated pyrite wastes (Torviscosa, Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Vamerali, Teofilo [Department of Environmental Sciences, University of Parma, Viale G.P. Usberti 11/A, 43100 Parma (Italy)], E-mail: teofilo.vamerali@unipd.it; Bandiera, Marianna; Coletto, Lucia; Zanetti, Federica [Department of Environmental Agronomy and Crop Sciences, University of Padova, Viale dell' Universita 16, 35020 Legnaro - Padova (Italy); Dickinson, Nicholas M. [Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF (United Kingdom); Mosca, Giuliano [Department of Environmental Agronomy and Crop Sciences, University of Padova, Viale dell' Universita 16, 35020 Legnaro - Padova (Italy)

    2009-03-15

    At a site in Udine, Italy, a 0.7 m layer of As, Co, Cu, Pb and Zn contaminated wastes derived from mineral roasting for sulphur extraction had been covered with an unpolluted 0.15 m layer of gravelly soil. This study investigates whether woody biomass phytoremediation is a realistic management option. Comparing ploughing and subsoiling (0.35 m depth), the growth of Populus and Salix and trace element uptake were investigated in both pot and field trials. Species differences were marginal and species selection was not critical. Impaired above-ground productivity and low translocation of trace elements showed that bioavailable contaminant stripping was not feasible. The most significant finding was of coarse and fine roots proliferation in surface layers that provided a significant sink for trace elements. We conclude that phytostabilisation and effective immobilisation of metals and As could be achieved at the site by soil amelioration combined with woody species establishment. Confidence to achieve a long-term and sustainable remediation requires a more complete quantification of root dynamics and a better understanding of rhizosphere processes. - In As- and metal-contaminated pyrite wastes, contaminant stripping is not feasible, and root foraging and quantification of root dynamics holds the key to stabilisation in woody species.

  1. Iron pyrite: Phase and shape control by facile hot injection method

    Science.gov (United States)

    Trinh, Thanh Kieu; Pham, Viet Thanh Hau; Truong, Nguyen Tam Nguyen; Kim, Chang Duk; Park, Chinho

    2017-03-01

    Pure phases of cubic and spherical FeS2 nanocrystals (NCs) with the mean size of 80 nm and 30 nm, respectively, were obtained using trioctylamine and oleylamine as the solvents to dissolve the sulfur source via a facile and efficient hot injection method. The pure phase formation and shape control were strongly dependent on the concentration of active sulfur source (H2S) that could be formed by the reaction between the elemental sulfur and a primary amine. The chemically active sulfur source could facilitate the formation of a pure FeS2 phase from a FeS phase via a Fe3S4 phase. In addition, the active sulfur concentration is believed to be the main factor to drive the orientation attachment to obtain different shapes of FeS2 NCs. The obtained FeS2 pyrite NCs with excellent phase purity and good optical properties are believed to have potential applications to various energy devices including low-cost photovoltaics.

  2. Composition and spectra of copper-carotenoid sediments from a pyrite mine stream in Spain

    Science.gov (United States)

    Garcia-Guinea, Javier; Furio, Marta; Sanchez-Moral, Sergio; Jurado, Valme; Correcher, Virgilio; Saiz-Jimenez, Cesareo

    2015-01-01

    Mine drainages of La Poderosa (El Campillo, Huelva, Spain), located in the Rio Tinto Basin (Iberian Pyrite Belt) generate carotenoid complexes mixed with copper sulfates presenting good natural models for the production of carotenoids from microorganisms. The environmental conditions of Rio Tinto Basin include important environmental stresses to force the microorganisms to accumulate carotenoids. Here we show as carotenoid compounds in sediments can be analyzed directly in the solid state by Raman and Luminescence spectroscopy techniques to identify solid carotenoid, avoiding dissolution and pre-concentration treatments, since the hydrous copper-salted paragenesis do not mask the Raman emission of carotenoids. Raman spectra recorded from one of these specimens' exhibit major features at approximately 1006, 1154, and 1520 cm-1. The bands at 1520 cm-1 and 1154 cm-1 can be assigned to in-phase Cdbnd C (γ-1) and Csbnd C stretching (γ-2) vibrations of the polyene chain in carotenoids. The in-plane rocking deformations of CH3 groups linked to this chain coupled with Csbnd C bonds are observed in the 1006 cm-1 region. X-irradiation pretreatments enhance the cathodoluminescence spectra emission of carotenoids enough to distinguish organic compounds including hydroxyl and carboxyl groups. Carotenoids in copper-sulfates could be used as biomarkers and useful proxies for understanding remote mineral formations as well as for terrestrial environmental investigations related to mine drainage contamination including biological activity and photo-oxidation processes.

  3. Environmental regulatory failure and metal contamination at the Giap Lai pyrite mine, Northern Vietnam.

    Science.gov (United States)

    Håkan Tarras-Wahlberg, N; Nguyen, Lan T

    2008-03-01

    The causes for the failure in enforcement of environmental regulations at the Giap Lai pyrite mine in northern Vietnam are considered and the environmental impacts that are associated with this mine are evaluated. It is shown that sulphide-rich tailings and waste rock in the mining area represent significant sources of acid rock drainage (ARD). The ARD is causing elevated metal levels in downstream water bodies, which in turn, represent a threat to both human health and to aquatic ecosystems. Metal concentrations in impacted surface waters have increased after mine closure, suggesting that impacts are becoming progressively more serious. No post-closure, remediation measures have been applied at the mine, in spite of the existence of environmental legislation and both central and regional institutions charged with environmental supervision and control. The research presented here provides further emphasis for the recommendation that, while government institutions may need to be strengthened, and environmental regulations need to be in place, true on the ground improvement in environmental quality in Vietnam and in many other developing countries require an increased focus on promoting public awareness of industrial environmental issues.

  4. On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite

    Science.gov (United States)

    Placencia-Gómez, Edmundo; Slater, Lee D.

    2016-12-01

    In order to expand the application of the induced polarization (IP) method as a technique for monitoring metallic mineral dissolution and precipitation mechanisms, we studied the effects of variations in pore water chemistry on the spectral induced polarization (SIP) response of a mixture of silica-sand and pyrite particles in the laboratory. We investigated the dependence of the SIP response on both pore water conductivity and pH for various chemical compositions: redox-passive (P) versus redox-active (A) ions, using CaCl2 as P-ions, and FeSO4 and FeCl3 as A-ion brines. The effect of pore water chemistry was evaluated by means of a recently proposed volumetric specific capacitance model. The SIP response (IP-effect) was primarily determined by the pore water conductivity and the specific capacitance was only weakly dependent on the chemical composition and pHw. We found that the specific capacitance varies to first order over a limited range and approximates a single value (≈ 302 F m- 3 in average). However, variations in the specific capacitance as a function of active versus inactive ion chemistry might be important to consider when using IP to monitor specific mineral dissolution and precipitation processes.

  5. Platinum-group element concentrations in pyrite from the Main Sulfide Zone of the Great Dyke of Zimbabwe

    Science.gov (United States)

    Piña, R.; Gervilla, F.; Barnes, S.-J.; Oberthür, T.; Lunar, R.

    2016-10-01

    The Main Sulfide Zone (MSZ) of the Great Dyke of Zimbabwe hosts the world's second largest resource of platinum-group elements (PGE) after the Bushveld Complex in South Africa. The sulfide assemblage of the MSZ comprises pyrrhotite, pentlandite, chalcopyrite, and minor pyrite. Recently, several studies have observed in a number of Ni-Cu-PGE ore deposits that pyrite may host significant amounts of PGE, particularly Pt and Rh. In this study, we have determined PGE and other trace element contents in pyrite from the Hartley, Ngezi, Unki, and Mimosa mines of the Great Dyke by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Based on the textures and PGE contents, two types of pyrite can be differentiated. Py1 occurs as individual euhedral or subhedral grains or clusters of crystals mostly within chalcopyrite and pentlandite, in some cases in the form of symplectitic intergrowths, and is PGE rich (up to 99 ppm Pt and 61 ppm Rh; 1.7 to 47.1 ppm Ru, 0.1 to 7.8 ppm Os, and 1.2 to 20.2 ppm Ir). Py2 occurs as small individual euhedral or subhedral crystals within pyrrhotite, pentlandite, and less frequently within chalcopyrite and silicates and has low PGE contents (<0.11 ppm Pt, <0.34 ppm Rh, <2.5 ppm Ru, <0.37 ppm Ir, and <0.40 ppm Os). Py1 contains higher Os, Ir, Ru, Rh, and Pt contents than the associated pyrrhotite, pentlandite, and chalcopyrite, whereas Py2 has similar PGE contents as coexisting pyrrhotite and pentlandite. Based on the textural relationships, two different origins are attributed for each pyrite type. Py1 intergrowth with pentlandite and chalcopyrite is inferred to have formed by late, low temperature (<300 °C) decomposition of residual Ni-rich monosulfide solid solution, whereas Py2 is suggested to have formed by replacement of pyrrhotite and pentlandite caused by late magmatic/hydrothermal fluids.

  6. Bacterial Disproportionation of Elemental Sulfur Inferred from a Field Study of Stable-Isotope Fractionations between Elemental Sulfur and Pyrite

    Science.gov (United States)

    Hardisty, D.; Pratt, L. M.; Olyphant, G. A.; Bell, J.; Johnson, A.

    2011-12-01

    Elemental sulfur (ES) is a common product of pyrite oxidation during acid mine drainage (AMD), but bacterial disproportionation of ES has not previously been inferred in acidic environments. Pore water profiles were collected seasonally within a coal-mine waste deposit, Minnehaha, in Southwest Indiana that has been abandoned for over 30 years. Geochemical characterization and modeling were used to assess how the interactions between the sulfur and iron cycle are affected by seasonally dynamic hydrologic conditions. Pore waters were collected seasonally and concentrations of Fe-species and sulfur isotopic compositions of sulfate were determined. Additionally, a sediment core was collected and used for sequential extraction and isotopic characterization of solid-phase sulfur species including elemental sulfur (δ34Ses), pyrite (δ34Spy), acid-volatile sulfides, water-soluble sulfates, and acid-soluble sulfates. The dominant disulfide phase was found to be pyrite through x-ray diffraction of an additional sediment core. Sulfur isotope fractionations between δ34Spy and δ34Ses (Δ34Ses-py) of up to -33% are inferred to indicate bacterial disproportionation of ES in the presence of a non-limiting sulfide 'scrub' Fe(III). The initial isotopic composition, following formation from pyrite oxidation, is inferred from δ34Spy, found to be ≈ 8.75% at the study site. Although ES has previously been found to accumulate in acidic Fe(III)-rich pore waters, ES is typically assumed to account for less than 1% of the oxidized sulfur pool and measurements of the ES isotopic composition are often neglected during field studies of acid AMD. The pore waters at Minnehaha were seasonally suboxic with sharp transitions from Fe(III)- to Fe(II)- dominated conditions near the phreatic surface. It is hypothesized that the sulfide product of ES disproportionation, fractionated by up to -8.6%, is immediately re-oxidized to ES near the redox gradient via reaction with Fe(III). Sulfide re

  7. Comparison of Different Methods for Determination of Pyrite Oxidation Rate in Wate Rock Pile at Mine Doyon, Quebec, Canada

    Science.gov (United States)

    Sracek, O.; Nicholson, R.; Gélinas, P.; Lefebvre, R.

    2004-05-01

    Mine Doyon is a gold mine located close to Noranda, Québec, Canada. The South waste rock pile contains mostly highly friable sericite schists with pyrite content up to 7 wt percent. Oxidation of pyrite resulted in the production of acid mine drainage with pH values of about 2.0, and sulfate concentrations in pore water above 200 g/L. The waste rock material is characterized by high permeability allowing thermally driven convective supply of oxygen at temperatures reaching up to 67oC close to the slopes of the pile. Several methods for the determination of pyrite oxidation rate (POR) in waste rock have been compared and evaluated. Methods based on data collected in situ such as the interpretation of oxygen concentration profiles in waste rock pile and pyrite concentrations in solid phase were compared with the oxygen consumption method (OCM) in the laboratory. Analytical 1-D solution based on oxygen and temperature profiles in the pile was used for preliminary determination of POR. Analytical modeling results were used as an input for 2-D numerical model using TOUGH AMD. POR values based on pyrite mass balance (PMB) in solid phase were also calculated, assuming that average pyrite content in the deep, almost non-oxidized zone of the pile represents pre-oxidation conditions. Calculations were performed for prismatic columns with 1 m2 base. An approach based on dissolved sulfate mass balance was not used because of the lack of data from early stage of the pile and the non-conservative behavior of sulfate (precipitation of gypsum and jarosite in the pile). Finally, the oxygen consumption method (OCM) in the laboratory was based on oxygen concentration decline in headspace of closed chamber, where samples of waste rock sprinkled by water were located. Both fresh samples from mining operation and partially weathered samples collected in the pile were used. A range of POR values (mol(O2).kg-1.s-1) were obtained from the various methods. At Site 6 on the slope of the pile

  8. Multiple sulfur isotope constraints on sulfate-driven anaerobic oxidation of methane: Evidence from authigenic pyrite in seepage areas of the South China Sea

    Science.gov (United States)

    Lin, Zhiyong; Sun, Xiaoming; Strauss, Harald; Lu, Yang; Gong, Junli; Xu, Li; Lu, Hongfeng; Teichert, Barbara M. A.; Peckmann, Jörn

    2017-08-01

    Multiple sulfur isotope signatures and secondary ion mass spectroscopy (SIMS) sulfur isotope compositions of pyrite from two seafloor sites (DH-CL11 and HD109) in seepage areas of the South China Sea were measured in order to study isotope effects of sulfate-driven anaerobic oxidation of methane (SO4-AOM). The multiple sulfur isotopes of pyrite reveal variable ranges for both sites (δ34S: between -44.1‰ and -2.9‰ for DH-CL11 and between -43.8‰ and -1.6‰ for HD109; Δ33S: between 0.02‰ and 0.17‰ for DH-CL11 and between -0.03‰ and 0.14‰ for HD109). SIMS analysis reveals an extreme variability of δ34S values (between -50.3‰ and -2.7‰ in DH-CL11; between -50.1 and 52.4‰ in HD109) for three types of pyrite: (1) framboids, (2) zoned aggregates with radial overgrowth surrounding a framboidal core, and (3) euhedral pyrite crystals. The synchronous changes of geochemical proxies (sulfate and methane concentrations, δ34Ssulfate and δ18Osulfate, δ34Spyrite, and pyrite content) at the sulfate-methane transition zone (SMTZ) at site DH-CL11 are interpreted to be induced by SO4-AOM under steady state conditions. In contrast, pyrite content and δ34S value fluctuations throughout core HD109 suggest that the sediment at this site was affected by multiple pyritization events during diagenesis. Multiple sulfur isotope signatures of early diagenetic pyrite (i.e., with low and high δ34S values, the latter above 315 cmbsf in DH-CL11; above 70 cmbsf in HD109) in the upper sediment column suggest that organoclastic sulfate reduction (OSR) and sulfur disproportionation generated the observed isotopic signatures. In contrast to the early diagenetic 34S depleted framboids, the higher SIMS δ34S values of overgrowth and euhedral crystals suggest a late diagenetic 34S enriched pool of dissolved sulfide derived from SO4-AOM at the current and paleo-SMTZs. Interestingly, pyrite resulting from SO4-AOM in the SMTZ at site DH-CL11 reveals a distinct pattern with higher

  9. The role of dissolved molecular oxygen in abiotic pyrite oxidation under acid pH conditions - Experiments with {sup 18}O-enriched molecular oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Heidel, Claudia, E-mail: claudia.heidel@gmx.net [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany); Tichomirowa, Marion [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany)

    2010-11-15

    Research highlights: {yields} A small amount of molecular oxygen is permanently incorporated into sulfate during pyrite oxidation. {yields} Molecular oxygen may be incorporated into sulfate by sulfite oxidation and tetrathionate oxidation. {yields} Molecular oxygen is incorporated into water molecules during its cathodic reduction. {yields} Molecular oxygen mainly accepts electrons from pyrite and minor from dissolved and adsorbed ferrous iron. - Abstract: Several O isotope studies have shown that SO{sub 4}{sup 2-} produced from aqueous pyrite oxidation mainly contains water-derived O and minor atmospherically-derived O{sub 2}. However, the incorporation of O{sub 2} into SO{sub 4}{sup 2-} has been shown to decrease continuously during pyrite oxidation experiments. Hence, it remains uncertain if (and how) O{sub 2} is permanently incorporated into SO{sub 4}{sup 2-} during pyrite oxidation. Abiotic aerobic batch pyrite oxidation experiments in aqueous solutions were performed under acid pH conditions. After 151 days, {sup 18}O-enriched O{sub 2} was injected into the headspace of the reaction vessels. Increasing {delta}{sup 18}O{sub SO{sub 4}} values with increasing injection volume of {sup 18}O-enriched O{sub 2} indicated the permanent incorporation of about 9% O{sub 2} into the produced SO{sub 4}{sup 2-} during pyrite oxidation from 151 to 201 days. Molecular oxygen may be incorporated into SO{sub 4}{sup 2-} by oxidation of the S intermediate species sulfite (and maybe tetrathionate) into SO{sub 4}{sup 2-}. However, only 4% of the O{sub 2} consumed during the experiments was incorporated into SO{sub 4}{sup 2-}. Slightly increased {delta}{sup 18}O{sub H{sub 2}O} values from experiments with the largest injection of {sup 18}O-enriched O{sub 2} indicated the incorporation of O{sub 2} into water molecules which may proceed during the cathodic reduction of O{sub 2}. Thus, O{sub 2} was an important electron acceptor under aerobic acid conditions. The observed {epsilon

  10. Re-Os systematics and age of pyrite associated with stratiform Zn-Pb mineralization in the Howards Pass district, Yukon and Northwest Territories, Canada

    Science.gov (United States)

    Kelley, Karen D.; Selby, David; Falck, Hendrik; Slack, John F.

    2016-05-01

    Stratiform Zn-Pb deposits hosted in unmetamorphosed carbonaceous and siliceous mudstones of the Ordovician to Silurian Duo Lake Formation define the Howards Pass district in Yukon Territory and Northwest Territories, western Canada. Collectively, the deposits are amongst the largest in the world, containing drill-indicated and inferred resources of 423 Mt at 4.84 % Zn and 1.59 % Pb. Sulphide textures include (a) fine-scale laminations of sphalerite, galena, and pyrite from rock; (b) layers of coarse sulphide that are structurally controlled by microfolds; and (c) veins that cut bedding and sulphide laminations. The finely interlaminated nature of sulphides with mudstone has been used as evidence for syngenetic mineralizing processes, whereas paleomagnetic data determined on coarse layered sulphides suggest a Middle Jurassic age of mineralization. Here, we present new rhenium-osmium (Re-Os) isotopic data for 12 pyrite separates obtained from 4 laminated sulphide-rich samples from the XY Central (XYC) and Don (DON) deposits and for 1 unmineralized organic-rich mudstone ˜20 m stratigraphically below the sulphide-bearing zone. Pyrite separates that lack mudstone inclusions ("pure") from the XYC deposit contain 2.2 to 4.0 ppb Re and 93.4 to 123.4 ppt Os; pure pyrite from the DON deposit is significantly more enriched in Re and Os (34-37 ppb Re; 636.8-694.9 ppt Os). The 187Re/188Os values of pure pyrite separates from the XYC and DON deposits range from 137.6 to 197 and 182.1 to 201.4, respectively. Regression of all pure pyrite Re-Os data from both deposits yields an isochron age of 442 ± 14 Ma (MSWD = 7.4) and an initial 187Os/188Os (Osi) value of 0.71 ± 0.07. The Re-Os age indicates that the early phase of pyrite precipitation (and by inference, sphalerite and galena) occurred during the early Silurian, consistent with biostratigraphic ages of the host rocks. The Osi value of ˜0.8 for earliest Silurian seawater recorded from organic-rich shale in the basal

  11. Subsurface mapping in the Iberian Pyrite Belt using seismic reflection profiling and potential-field data

    Science.gov (United States)

    Carvalho, João; Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Granado, Isabel; Branch, Tim; Represas, Patrícia; Carabaneanu, Livia; Matias, Luís; Sousa, Pedro

    2017-04-01

    The Iberian Pyrite Belt (IPB) hosts world-class massive sulphide deposits, such as Neves-Corvo in Portugal and Rio Tinto in Spain. In Portugal, the Palaeozoic Volcanic-Sedimentary Complex (VSC) hosts these ore deposits, extending from the Grândola-Alcácer region to the Spanish border with a NW-SE to WNW-ESE trend. In the study area, between the Neves-Corvo mine region and Alcoutim (close to the Spanish border), the VSC outcrops only in a small horst near Alcoutim. Sparse exploration drill-hole data indicate that the depth to the top of the VSC varies from several 100 m to about 1 km beneath the Mértola Formation Flysch cover. Mapping of the VSC to the SE of Neves-Corvo mine is an important exploration goal and motivated the acquisition of six 2D seismic reflection profiles with a total length of approximately 82 km in order to map the hidden extension of the VSC. The data, providing information deeper than 10 km at some locations, were integrated in a 3D software environment along with potential-field, geological and drill-hole data to form a 3D structural framework model. Seismic data show strong reflections that represent several long Variscan thrust planes that smoothly dip to the NNE. Outcropping and previously unknown Late Variscan near-vertical faults were also mapped. Our data strongly suggest that the structural framework of Neves-Corvo extends south-eastwards to Alcoutim. Furthermore, the VSC top is located at depths that show the existence within the IPB of new areas with good potential to develop exploration projects envisaging the discovery of massive sulphide deposits of the Neves-Corvo type.

  12. Subsurface mapping in the Iberian Pyrite Belt using seismic reflection profiling and potential-field data

    Science.gov (United States)

    Carvalho, João; Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Granado, Isabel; Branch, Tim; Represas, Patrícia; Carabaneanu, Livia; Matias, Luís; Sousa, Pedro

    2016-06-01

    The Iberian Pyrite Belt (IPB) hosts world-class massive sulphide deposits, such as Neves-Corvo in Portugal and Rio Tinto in Spain. In Portugal, the Palaeozoic Volcanic-Sedimentary Complex (VSC) hosts these ore deposits, extending from the Grândola-Alcácer region to the Spanish border with a NW-SE to WNW-ESE trend. In the study area, between the Neves-Corvo mine region and Alcoutim (close to the Spanish border), the VSC outcrops only in a small horst near Alcoutim. Sparse exploration drill-hole data indicate that the depth to the top of the VSC varies from several 100 m to about 1 km beneath the Mértola Formation Flysch cover. Mapping of the VSC to the SE of Neves-Corvo mine is an important exploration goal and motivated the acquisition of six 2D seismic reflection profiles with a total length of approximately 82 km in order to map the hidden extension of the VSC. The data, providing information deeper than 10 km at some locations, were integrated in a 3D software environment along with potential-field, geological and drill-hole data to form a 3D structural framework model. Seismic data show strong reflections that represent several long Variscan thrust planes that smoothly dip to the NNE. Outcropping and previously unknown Late Variscan near-vertical faults were also mapped. Our data strongly suggest that the structural framework of Neves-Corvo extends south-eastwards to Alcoutim. Furthermore, the VSC top is located at depths that show the existence within the IPB of new areas with good potential to develop exploration projects envisaging the discovery of massive sulphide deposits of the Neves-Corvo type.

  13. Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event.

    Science.gov (United States)

    Konhauser, Kurt O; Lalonde, Stefan V; Planavsky, Noah J; Pecoits, Ernesto; Lyons, Timothy W; Mojzsis, Stephen J; Rouxel, Olivier J; Barley, Mark E; Rosìere, Carlos; Fralick, Phillip W; Kump, Lee R; Bekker, Andrey

    2011-10-19

    The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48 Gyr ago, but within the 160 Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48 Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology.

  14. Yeast diversity in the extreme acidic environments of the Iberian Pyrite Belt.

    Science.gov (United States)

    Gadanho, Mário; Libkind, Diego; Sampaio, José Paulo

    2006-10-01

    In the Iberian Pyrite Belt (IPB), acid rock drainage gives rise to aquatic habitats with low pH and high concentrations of heavy metals, a situation that causes important environmental problems. We investigated the occurrence and diversity of yeasts in two localities of the IPB: São Domingos (Portugal) and Rio Tinto (Spain). Yeast isolation was performed on conventional culture media (MYP), acidified (pH 3) media (MYP3), and on media prepared with water from the study sites (MYPw). The main goal of the study was to determine the structure of the yeast community; a combination of molecular methods was used for accurate species identifications. Our results showed that the largest fraction of the yeast community was recovered on MYPw rather than on MYP and MYP3. Twenty-seven yeast species were detected, 48% of which might represent undescribed taxa. Among these, an undescribed species of the genus Cryptococcus required low pH for growth, a property that has not been observed before in yeasts. The communities of S. Domingos and R. Tinto showed a considerable resemblance, and eight yeast species were simultaneously found in both localities. Taking into consideration the physicochemical parameters studied, we propose a hierarchic organization of the yeast community in terms of high-, intermediate-, or low-stress conditions of the environment. According to this ranking, the acidophile yeast Cryptococcus sp. 5 is considered the most tolerant species, followed by Cryptococcus sp. 3 and Lecytophora sp. Species occurring in situations of intermediate environmental stress were Candida fluviatilis, Rhodosporidium toruloides, Williopsis californica, and three unidentified yeasts belonging to Rhodotorula and Cryptococcus.

  15. Magnetic pyrite cinder as an efficient heterogeneous ozonation catalyst and synergetic effect of deposited Ce.

    Science.gov (United States)

    Wu, Deli; Liu, Ying; He, Hongping; Zhang, Yalei

    2016-07-01

    Heterogeneous catalytic ozonation was emerged to be a promising alternative in the mineralization of various persistent organic pollutants in recent decades. Magnetic pyrite cinder (PyC), which was employed as the catalyst in our investigation, was further deposited by Ce (Ce-PyC) to enhance its catalytic activity in the degradation of aqueous reactive black 5 (RB5). The results showed that additional 17.39%, 42.12% mineralization efficiency was obtained by O3/PyC, O3/Ce-PyC, respectively, in the degradation of RB5 compared to that of O3 alone under identical experimental condition. The reaction mechanism involved the enhanced mineralization of aqueous RB5 at the catalyst-solution interface via hydroxyl radicals produced by the reaction between O3 and catalyst surface. Besides surface hydroxyl, surface Ce(Ⅲ) was crucial for Ce-PyC in the enhanced generation of hydroxyl radicals. More surprisingly, it was found that both PyC and Ce-PyC could exert quite stable catalytic activity in a wide pH range from 3 to 10, which was supposed to be combined with inherently comprised various metal oxide, such as Fe2O3, Fe3O4, MnO2 and CuO. Ozone utilization evaluation demonstrated that PyC and Ce-PyC facilitated effective ozone decomposition, as ozone utilization efficiency (mgTOC/mgO3) of O3/PyC and O3/Ce-PyC increased 64.0%, 155.0%, respectively, compared to that of O3 alone. This investigation provided an effective alternative in the resource utilization of PyC, which was traditionally characterized as a waste material.

  16. Immobilization of toxic elements in mine residues derived from mining activities in the Iberian Pyrite Belt (SW Spain): Laboratory experiments

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, R.; Nieto, J.M.; de Almodovar, G.R. [University of Huelva, Huelva (Spain). Dept. of Geology

    2007-09-15

    In the mining environments of the Iberian Pyrite Belt (IPB), the oxidation of sulphide wastes generates acid drainage with high concentrations of SO{sub 4}, metals and metalloids (Acid Mine Drainage, AMD). These acid and extremely contaminated discharges are drained by the fluvial courses of the Huelva province (SW Spain) which deliver high concentrations of potentially toxic elements into the Gulf of Cadiz. In this work, the oxidation process of mine tailings in the IPB, the generation of AMD and the potential use of coal combustion fly ash as a possible alkaline treatment for neutralization of and metal removal from AMD, was studied in non-saturated column experiments. The laboratory column tests were conducted on a mine residue (71.6 wt% pyrite) with artificial rainfall or irrigation. A non-saturated column filled solely with the pyrite residue leached solutions with an acid pH (approx. 2) and high concentrations of SO{sub 4} and metals. These leachates have the same composition as typical AMD, and the oxidation process can be compared with the natural oxidation of mine tailings in the IPB. However, the application of fly ash to the same amount of mine residue in another two non-saturated columns significantly increased the pH and decreased the SO{sub 4} and metal concentrations in the leaching solutions. The improvement in the quality of leachates by fly ash addition in the laboratory was so effective that the leachate reached the pre-potability requirements of water for human consumption under EU regulations. The extrapolation of these experiments to the field is a promising solution for the decontamination of the fluvial courses of the IPB, and therefore, the decrease of pollutant loads discharging to the Gulf of Cadiz.

  17. A remediation strategy based on active phytoremediation followed by natural attenuation in a soil contaminated by pyrite waste

    Energy Technology Data Exchange (ETDEWEB)

    Clemente, Rafael [Department of Soil and Water Conservation and Organic Waste Management, Centro de Edafologia y Biologia Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Apartado 164, 30100 Espinardo, Murcia (Spain)]. E-mail: rclemente@cebas.csic.es; Almela, Concepcion [Instituto de Agroquimica y Tecnologia de Alimentos, CSIC, Apartado 73, 46100 Burjassot, Valencia (Spain); Bernal, M. Pilar [Department of Soil and Water Conservation and Organic Waste Management, Centro de Edafologia y Biologia Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Apartado 164, 30100 Espinardo, Murcia (Spain)

    2006-10-15

    Phytoremediation of metal-polluted soils can be promoted by the proper use of soil amendments and agricultural practices. A 4-year phytoremediation programme was applied to a site affected by the toxic spill of pyrite residue at Aznalcollar (Spain) in 1998, contaminated with heavy metals (Zn, Cu, Pb, Cd) and arsenic. This consisted of active phytoremediation, using organic amendments (cow manure and compost) and lime and growing two successive crops of Brassica juncea (L.) Czern., followed by natural attenuation without further intervention. Changes in soil pH, extractable metal and As concentrations, organic carbon content and microbial biomass was evaluated. The initial oxidation of metal sulphides from pyrite residues released soluble metals and reduced soil pH to extremely acidic values (mean 4.1, range 2.0-7.0). The addition of lime (up to 64 t ha{sup -1}) increased soil pH to adequate values for plant growth, resulting in a significant decrease in DTPA-extractable metal concentrations in all plots. Natural attenuation phase showed also a decrease in extractable metals. Organic treatments increased the soil total organic carbon, which led to higher values of microbial biomass (11.6, 15.2 and 14.9 g kg{sup -1} TOC and 123, 170 and 275 {mu}g g{sup -1} biomass-C in control, compost and manure plots, respectively). Active phytoremediation followed by natural attenuation, was effective for remediation of this pyrite-polluted soil. - The addition of lime and organic amendments decreased heavy metal solubility and promoted Natural attenuation of a recently-contaminated soil.

  18. Effect of Surface Oxidation on Interfacial Water Structure at a Pyrite (100) Surface as Studied by Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.; Wick, Collin D.

    2015-06-01

    In the first part of this paper, a Scanning Electron Microscopy and contact angle study of a pyrite surface (100) is reported describing the relationship between surface oxidation and the hydrophilic surface state. In addition to these experimental results, the following simulated surface states were examined using Molecular Dynamics Simulation (MDS): fresh unoxidized (100) surface; polysulfide at the (100) surface; elemental sulfur at the (100) surface. Crystal structures for the polysulfide and elemental sulfur at the (100) surface were simulated using Density Functional Theory (DFT) quantum chemical calculations. The well known oxidation mechanism which involves formation of a metal deficient layer was also described with DFT. Our MDS results of the behavior of interfacial water at the fresh and oxidized pyrite (100) surfaces without/with the presence of ferric hydroxide include simulated contact angles, number density distribution for water, water dipole orientation, water residence time, and hydrogen-bonding considerations. The significance of the formation of ferric hydroxide islands in accounting for the corresponding hydrophilic surface state is revealed not only from experimental contact angle measurements but also from simulated contact angle measurements using MDS. The hydrophilic surface state developed at oxidized pyrite surfaces has been described by MDS, on which basis the surface state is explained based on interfacial water structure. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE funded work performed by Liem X. Dang. Battelle operates the Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.

  19. 硫铁矿烧渣的熟化及机理%Maturation of pyrite cinders and its mechanism

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 陈白珍; 龚竹青; 陈文汨

    2001-01-01

    研究了熟化法回收硫铁矿浇渣中的铁及其反应机 理。 将硫铁矿烧渣与硫酸混合后, 经过熟化处理可使烧渣中铁的回收率达到90%以上。 熟 化温度为100~300  ℃、 熟化时间1~2  h、 硫酸用量为理论用量的1.0~ 1.2倍以及硫酸浓度为65 %~85%时, 铁回收率较高。 表面电镜(SEM)实验表明熟化后烧渣变成晶状颗粒, X射线衍 射证实熟化烧渣中有FeH(SO4)2*4H2O生成。%The maturation of pyrite cinders for recovering iron and its mechanism were studied. The rate of iron recovery of pyrite cinder s is up to 90 % by maturation treatment after pyrite cinders mixing with sulfur acid. Higher rat e of iron recovery can be obtained when maturation temperature is 100~300  ℃, maturation time 1~2  h, sulfur acid 1~1.2 times of th eoretical quality and concentration of sulfur acid 65%~85%. SEM demonstrated t hat the globula r cinders become crystal grains after maturation. XRD analysis proved t hat FeH(SO4)2*4H2O is produced after maturation.

  20. Sedimentary pyrite δ34S differs from porewater sulfide in Santa Barbara Basin: Proposed role of organic sulfur

    Science.gov (United States)

    Raven, Morgan Reed; Sessions, Alex L.; Fischer, Woodward W.; Adkins, Jess F.

    2016-08-01

    Santa Barbara Basin sediments host a complex network of abiotic and metabolic chemical reactions that knit together the carbon, sulfur, and iron cycles. From a 2.1-m sediment core collected in the center of the basin, we present high-resolution profiles of the concentrations and isotopic compositions of all the major species in this system: sulfate, sulfide (∑H2S), elemental sulfur (S0), pyrite, extractable organic sulfur (OS), proto-kerogen S, total organic and dissolved inorganic carbon, and total and reducible iron. Below 10 cm depth, the core is characterized by low apparent sulfate reduction rates (biogeochemical cycles and redox structure in sedimentary paleoenvironments.

  1. Contribution of Cistus ladanifer L. andCistus salvifolius L. for environmentla rehabilitation of mine areas from iberian pyrite belt

    OpenAIRE

    Santos, Erika; Ferreira, Mara; Abreu, Maria Manuela

    2011-01-01

    The aim of this study was to evaluate the potential of combined use of Cistus ladanifer and Cistus salviifolius for environmental rehabilitation of abandoned mine areas from Iberian Pyrite Belt. Soils from São Domingos mine area are heterogeneous, due to different characteristics of the original materials, and showed high total concentrations of trace elements (1940- 3030 mg As kg-1; 210-237 mg Cu kg-1; 5280-9210 mg Pb kg-1). Available fractions of trace elements presented, in gen...

  2. Chalcopyrite dissolution: Scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite

    Science.gov (United States)

    Li, Yubiao; Qian, Gujie; Brown, Paul L.; Gerson, Andrea R.

    2017-09-01

    Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS2) surfaces (pH 1.0 HClO4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S2- (bulk), S22- and Sn2- were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S0 and SO42- were observed but not SO32-, indicating that the greater Fe3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS2) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S0, SO32- and SO42- being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g. contacting with pyrite, while increased Fe3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting

  3. Study of magnetic properties of nano-powders prepared by pyrite -> troilite transformation via high energy milling

    DEFF Research Database (Denmark)

    Balaz, P.; Alacova, A.; Godocikova, E.;

    2004-01-01

    the formation of troilite FeS together with residual Fe metal after relatively short milling times. The kinetic studies performed by Mossbauer spectrometry and VSM magnetometry enabled us to follow the progress of nanocrystalline magnetic phase formation in more details. It was shown that the pyrite......The preparation of nanocrystalline troilite by high-energy milling of FeS2 sulphide with elemental Fe acting as reducing element is reported. X-ray difractometry was used in order to determine the presence of different phases in investigated samples. This technique allowed us to identify......-->troilite transformation is almost finished already after 25 minutes of high-energy milling....

  4. Soil pollution by oxidation of tailings from toxic spill of a pyrite mine

    Energy Technology Data Exchange (ETDEWEB)

    Simon, M.; Martin, F.; Ortiz, I.; Garcia, I.; Fernandez, J.; Fernandez, E.; Dorronsoro, C.; Aguilar, J. [Dpto. de Edafologia y Quimica Agricola, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain)

    2001-11-12

    On the 25th April 1998, toxic water and tailings from a pyrite mine of Aznalcollar (southern Spain) spilled into the Agrio and Guadiamar River Basin affecting some 40 km{sup 2}. In five sectors throughout the basin, we monitored the physical and chemical properties of the tailings as well as the degree of pollution in the soils on four different sampling dates: 5 May, 20 May, 4 June and 22 July 1998. The characteristics of the tailings deposited on the soils are shown to be related to distance from the spill. The oxidation rate of the tailings and the solubilization of the pollutant elements were more pronounced in the middle and lower sectors of the basin, where the particle size was finer, the sulfur content higher and the bulk density less. The increases in water-soluble sulfates, Zn, Cd and Cu were very rapid (the highest values being reached 25 days after the spill) and intense (reaching 45% of the total Cu, 65% of the total Zn and Cd). Meanwhile, the increases in water-soluble As, Bi, Sb, Pb and Tl were far lower (ranging between 0.002% of the total Tl and 2.5% of the total As) and less rapid in the case of As, Bi and Pb (the highest values for these elements being reached 40 days after the spill). These soluble elements infiltrated the soils with the rainwater, swiftly augmenting the soil pollution. Twenty-five days after the spill, when the rainfall ranged between 45 and 63 mm, the first 10-cm of the soils in the middle and lower sectors of the basin exceeded the maximum concentration permitted for agricultural soils in Zn, Cu and Tl. At 40 days after the spill, when the rainfall ranged between 60 and 89 mm, all the soils reached or exceeded the maximum permitted concentrations for As and Tl. Nevertheless, the pollutants tended to concentrate in the first 10 cm of the soils without seriously contaminating either the subsoil or the groundwaters. Consequently, a rapid removal of the tailings and the ploughing of the first 25-30 cm of the soils would be urgent

  5. First-principles investigation of the electronic states at perovskite and pyrite hetero-interfaces

    KAUST Repository

    Nazir, Safdar

    2012-09-01

    Oxide heterostructures are attracting huge interest in recent years due to the special functionalities of quasi two-dimensional quantum gases. In this thesis, the electronic states at the interface between perovskite oxides and pyrite compounds have been studied by first-principles calculations based on density functional theory. Optimization of the atomic positions are taken into account, which is considered very important at interfaces, as observed in the case of LaAlO3/SrTiO3. The creation of metallic states at the interfaces thus is explained in terms of charge transfer between the transition metal and oxygen atoms near the interface. It is observed that with typical thicknesses of at least 10-12 °A the gases still extend considerably in the third dimension, which essentially determines the magnitude of quantum mechanical effects. To overcome this problem, we propose incorporation of highly electronegative cations (such as Ag) in the oxides. A fundamental interest is also the thermodynamic stability of the interfaces due to the possibility of atomic intermixing in the interface region. Therefore, different cation intermixed configurations are taken into account for the interfaces aiming at the energetically stable state. The effect of O vacancies is also discussed for both polar and non-polar heterostructures. The interface metallicity is enhanced for the polar system with the creation of O vacancies, while the clean interface at the non-polar heterostructure exhibits an insulating state and becomes metallic in presence of O vacancy. The O vacancy formation energies are calculated and explained in terms of the increasing electronegativity and effective volume of A the side cation. Along with these, the electronic and magnetic properties of an interface between the ferromagnetic metal CoS2 and the non-magnetic semiconductor FeS2 is investigated. We find that this contact shows a metallic character. The CoS2 stays quasi half metallic at the interface, while the

  6. Simulation of pyrite oxidation in fresh mine tailings under near-neutral conditions.

    Science.gov (United States)

    Alakangas, Lena; Lundberg, Angela; Nason, Peter

    2012-08-01

    Sulphidic residual products from ore processing may produce acid rock drainage, when exposed to oxygen and water. Predictions of the magnitude of ARD and sulphide oxidation rates are of great importance in mine planning because they can be used to minimize or eliminate ARD and the associated economic and environmental costs. To address the lack of field data of sulphide oxidation rate in fresh sulphide-rich tailings under near-neutral conditions, determination and simulation of the rate was performed in pilot-scale at Kristineberg, northern Sweden. The quality of the drainage water was monitored, along with oxygen and carbon dioxide concentrations. The chemical composition of the solid tailings was also determined. The field data were compared to predictions from simulations of pyrite oxidation using a 1-D numerical model. The simulations' estimates of the amount of Fe and S released over a seven year period (52 kg and 178 kg, respectively) were in reasonably good agreement with those obtained by analysing the tailings (34 kg and 155 kg, respectively). The discrepancy is probably due to the formation of secondary precipitates such as iron hydroxides and gypsum; which are not accounted for in the model. The observed mass transport of Fe and S (0.05 and 1.0 kg per year, respectively) was much lower than expected on the basis of the simulations and the core data. Neutralization reactions involving carbonates in the tailings result in a near-neutral pH at all depths except at the oxidation front (pH < 5), indicating that the dissolution of carbonates was too slow for the acid to be neutralized, which instead neutralized deeper down in the tailings. This was also indicated by the reduced abundance of solid Ca at greater depths and the high levels of carbon dioxide both of which are consistent with the dissolution of carbonates. It could be concluded that the near-neutral pH in the tailings has no decreasing effect on the rate of sulphide oxidation, but does reduce the

  7. An experimental study on the geochemical behavior of highly siderophile elements (HSE) and metalloids (As, Se, Sb, Te, Bi) in a mss-iss-pyrite system at 650 °C: A possible magmatic origin for Co-HSE-bearing pyrite and the role of metalloid-rich phases in the fractionation of HSE

    Science.gov (United States)

    Cafagna, Fabio; Jugo, Pedro J.

    2016-04-01

    Pyrite, the most abundant sulfide in the Earth's crust, is an accessory mineral in several magmatic sulfide deposits. Although most pyrite is hydrothermal, previous experimental studies have shown that pyrite can also have a primary magmatic origin, by exsolving from monosulfide solid solution (mss) during cooling of a sulfide melt, if sulfur fugacity is sufficiently high. Pyrite from some localities has significant amounts of Co, and complex zonation in some low-melting-point chalcophile elements (LMCE), such as As, Se, Sb, Te, Bi (henceforth referred to as metalloids) and some platinum-group elements (PGE: Ru, Rh, Pd, Os, Ir, Pt). However, the origin of such pyrite and the causes of zonation are not clear. Because the distribution of some of these elements is heterogeneous and seems to be developed in concentric zones, the zonation has been interpreted to represent growth stages, some of them secondary and caused partly by hydrothermal fluids. Better constraints on the origin of Co-PGE-bearing pyrite could help unravel the geochemical processes affecting the sulfide assemblages in which it is found; thus, an experimental study was undertaken to characterize pyrite formation in magmatic sulfide environments and its relationship with metalloids and highly siderophile elements (HSE: PGE, Re, Au). Natural pyrrhotite, chalcopyrite, pentlandite and elemental S were mixed and doped with approximately 50 ppm of each HSE. A mixture of metalloids was added at 0.2 wt.% or 3 wt.% to aliquots of sulfide mixtures. Starting materials were sealed in evacuated silica tubes and fused at 1200 °C. The temperature was subsequently reduced to 750 °C (at 60 °C/h), then to 650 °C (at 0.5 °C/h) to produce relatively large euhedral pyrite crystals, then quenched. The experiments were analyzed using reflected light, SEM, EPMA and LA-ICP-MS. Experimental products contained euhedral pyrite, mss, intermediate solid solution (iss) and metalloid-rich phases, interpreted as quench product

  8. X-ray absorption near the edge structure and x-ray photoelectron spectroscopy studies on pyrite prepared by thermally sulfurizing iron films

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Liu Ying-Shu; Wang Bao-Yi; Wei Long; Kui Re-Xi; Qian Hai-Jie

    2009-01-01

    This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by x-ray absorption near edge structure spectra and x-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.

  9. Isolation and characterization of a novel Acidithiobacillus ferrivorans strain from the Chilean Altiplano: attachment and biofilm formation on pyrite at low temperature.

    Science.gov (United States)

    Barahona, Sergio; Dorador, Cristina; Zhang, Ruiyong; Aguilar, Pablo; Sand, Wolfgang; Vera, Mario; Remonsellez, Francisco

    2014-11-01

    Microorganisms are used to aid the extraction of valuable metals from low-grade sulfide ores in mines worldwide, but relatively little is known about this process in cold environments. This study comprises a preliminary analysis of the bacterial diversity of the polyextremophilic acid River Aroma located in the Chilean Altiplano, and revealed that Betaproteobacteria was the most dominant bacterial group (Gallionella-like and Thiobacillus-like). Taxa characteristic of leaching environments, such Acidithiobacillus and Leptospirillum, were detected at low abundances. Also, bacteria not associated with extremely acidic, metal-rich environments were found. After enrichment in iron- and sulfur-oxidizing media, we isolated and identified a novel psychrotolerant Acidithiobacillus ferrivorans strain ACH. This strain can grow using ferrous iron, sulfur, thiosulfate, tetrathionate and pyrite, as energy sources. Optimal growth was observed in the presence of pyrite, where cultures reached a cell number of 6.5 · 10(7) cells mL(-1). Planktonic cells grown with pyrite showed the presence of extracellular polymeric substances (10 °C and 28 °C), and a high density of cells attached to pyrite grains were observed at 10 °C by electron microscopy. The attachment of cells to pyrite coupons and the presence of capsular polysaccharides were visualized by using epifluorescence microscopy, through nucleic acid and lectin staining with Syto(®)9 and TRITC-Con A, respectively. Interestingly, we observed high cell adhesion including the formation of microcolonies within 21 days of incubation at 4 °C, which was correlated with a clear induction of capsular polysaccharides production. Our data suggests that attachment to pyrite is not temperature-dependent in At. ferrivorans ACH. The results of this study highlight the potential of this novel psychrotolerant strain in oxidation and attachment to minerals under low-temperature conditions.

  10. Effect of capping ligands on the optical properties and electronic energies of iron pyrite FeS{sub 2} nanocrystals and solid thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Guangmei, E-mail: zhaiguangmei@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Jiangsu Key Laboratory for Solar Cell Materials and Technology, Changzhou University, Changzhou, Jiangsu 213164 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Xie, Rongwei; Wang, Heng; Zhang, Jitao; Yang, Yongzhen; Wang, Hua; Li, Xuemin [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Liu, Xuguang [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Xu, Bingshe [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China)

    2016-07-25

    In this work, the optical and electronic properties of iron pyrite FeS{sub 2} nanocrystals and solid thin films with various capping ligands were systematically investigated by UV–Vis–NIR absorption spectroscopy, cyclic voltammetry and current density–voltage characteristic measurements. The iron pyrite nanocrystals with various ligands have an indirect band gap of around 1.05 eV and broad absorption spanning into the near-infrared region, exhibiting favorable optical properties for their photovoltaic applications. The electron affinities and ionization potentials of FeS{sub 2} nanocrystals determined through cyclic voltammetry measurements show strong ligand dependence. An energy level shift of up to 190 meV was obtained among the pyrite nanocrystals capped with the ligands employed in this work. The iron pyrite nanocrystal films capped with iodide and 1,2-ethanedithiol exhibit the largest band edge energy shift and conductivity, respectively. Our results not only provide several useful optical and electronic parameters of pyrite nanocrystals for their further use in optoelectronic devices as active layers and/or infrared optical absorption materials, but also highlight the relationship between their surface chemistry and electronic energies. - Highlights: • The energy levels of FeS{sub 2} nanocrystals with various ligands were determined via electrochemical measurements. • The energy levels of FeS{sub 2} nanocrystals showed strong ligand-dependence. • An energy level shift of up to 190 meV was obtained for the pyrite nanocrystals studied in the work. • The conductivities of FeS{sub 2} nanocrystals with different ligands were obtained by current density–voltage measurements.

  11. Assisted phytoremediation of mixed metal(loid)-polluted pyrite waste: effects of foliar and substrate IBA application on fodder radish.

    Science.gov (United States)

    Vamerali, Teofilo; Bandiera, Marianna; Hartley, William; Carletti, Paolo; Mosca, Giuliano

    2011-06-01

    Exogenous application of plant-growth promoting substances may potentially improve phytoremediation of metal-polluted substrates by increasing shoot and root growth. In a pot-based study, fodder radish (Raphanus sativus L. var. oleiformis Pers.) was grown in As-Zn-Cu-Co-Pb-contaminated pyrite waste, and treated with indolebutyric acid (IBA) either by foliar spraying (10 mgL(-1)), or by direct application of IBA to the substrate (0.1 and 1 mgkg(-1)) in association, or not, with foliar spraying. With the exception of foliar spraying, IBA reduced above-ground biomass, whilst direct application of IBA to the substrate surface reduced root biomass (-59%). Trace element concentrations were generally increased, but removals (mg per plant) greatly reduced with IBA application, together with greater metal leaching from the substrate. It is concluded that, in our case, IBA had a negative effect on plant growth and phytoextraction of trace elements, possibly due to unsuitable root indoleacetic acid concentration following soil IBA application, the direct chelating effect of IBA and the low microbial activity in the pyrite waste affecting its breakdown.

  12. A review of the fundamental studies of the copper activation mechanisms for selective flotation of the sulfide minerals, sphalerite and pyrite.

    Science.gov (United States)

    Chandra, A P; Gerson, A R

    2009-01-30

    A review of the considerable, but often contradictory, literature examining the specific surface reactions associated with copper adsorption onto the common metal sulfide minerals sphalerite, (Zn,Fe)S, and pyrite (FeS(2)), and the effect of the co-location of the two minerals is presented. Copper "activation", involving the surface adsorption of copper species from solution onto mineral surfaces to activate the surface for hydrophobic collector attachment, is an important step in the flotation and separation of minerals in an ore. Due to the complexity of metal sulfide mineral containing systems this activation process and the emergence of activation products on the mineral surfaces are not fully understood for most sulfide minerals even after decades of research. Factors such as copper concentration, activation time, pH, surface charge, extent of pre-oxidation, water and surface contaminants, pulp potential and galvanic interactions are important factors affecting copper activation of sphalerite and pyrite. A high pH, the correct reagent concentration and activation time and a short time delay between reagent additions is favourable for separation of sphalerite from pyrite. Sufficient oxidation potential is also needed (through O(2) conditioning) to maintain effective galvanic interactions between sphalerite and pyrite. This ensures pyrite is sufficiently depressed while sphalerite floats. Good water quality with low concentrations of contaminant ions, such as Pb(2+)and Fe(2+), is also needed to limit inadvertent activation and flotation of pyrite into zinc concentrates. Selectivity can further be increased and reagent use minimised by opting for inert grinding and by carefully choosing selective pyrite depressants such as sulfoxy or cyanide reagents. Studies that approximate plant conditions are essential for the development of better separation techniques and methodologies. Improved experimental approaches and surface sensitive techniques with high spatial

  13. Final Technical Report. Reactivity of Iron-Bearing Minerals and CO2 Sequestration and Surface Chemistry of Pyrite. An Interdisciplinary Approach

    Energy Technology Data Exchange (ETDEWEB)

    Strongin, Daniel [Temple Univ., Philadelphia, PA (United States)

    2014-12-31

    Over the course of the scientific program, two areas of research were pursued: reactions of iron oxides with supercritical CO2 and sulfide and surface reactivity of pyrite. The latter area of interest was to understand the chemistry that results when supercritical CO2 (scCO2 ) with H2 S and/or SO2 in deep saline formations (DFS) contacts iron bearing minerals. Understanding the complexities the sulfur co-injectants introduce is a critical step in developing CO2 sequestration as a climate-mitigating strategy. The research strategy was to understand macroscopic observations of this chemistry with an atomic/molecular level view using surface analytical techniques. Research showed that the exposure of iron (oxyhdr)oxides (which included ferrihydrite, goethite, and hematite) to scCO2 in the presence of sulfide led to reactions that formed siderite (FeCO3). The results have important implications for the sequestration of CO2 via carbonation reactions in the Earth’s subsurface. An earlier area of focus in the project was to understand pyrite oxidation in microscopic detail. This understanding was used to understand macroscopic observations of pyrite reactivity. Results obtained from this research led to a better understanding how pyrite reacts in a range of chemical environments. Geochemical and modern surface science techniques were used to understand the chemistry of pyrite in important environmental conditions. The program relied on a strong integration the results of these techniques to provide a fundamental understanding to the macroscopic chemistry exhibited by pyrite in the environment. Major achievements during these studies included developing an understanding of the surface sites on pyrite that controlled its reactivity under oxidizing conditions. In particular sulfur anion vacancies and/or ferric sites were sites of reactivity. Studies also showed that the

  14. High-resolution quadruple sulfur isotope analyses of 3.2 Ga pyrite from the Barberton Greenstone Belt in South Africa reveal distinct environmental controls on sulfide isotopic arrays

    NARCIS (Netherlands)

    Roerdink, D.L.; Mason, P.R.D.; Whitehouse, M.J.; Reimer, T.

    2013-01-01

    Multiple sulfur isotopes in Paleoarchean pyrite record valuable information on atmospheric processes and emerging microbial activity in the early sulfur cycle. Here, we report quadruple sulfur isotope data (32S, 33S, 34S, 36S) analyzed by secondary ion mass spectrometry from pyrite in a 3.26–3.23 Ga

  15. Physiological response of Cistus monspeliensis L. growing in two mine areas of the Iberian Pyrite Belt

    Science.gov (United States)

    Arenas Lago, Daniel; Carvalho, Luisa C.; Santos, Erika S.; Abreu, Maria Manuela; Andrade, María Luisa

    2015-04-01

    São Domingos and Lousal mines, nowadays in abandoned state, are located in Portugal, in the Iberian Pyrite Belt, a world-class volcanic-hosted massive sulfide. As a result of the intense mining activity large volumes of wastes containing metal(loid)s were partly exposed to weathering realising potential hazardous elements contaminating waters, soils and sediments. In both mines, a great part of the contaminated areas is relatively covered by several wild species. These species have developed mechanisms of response to oxidative stress originated by high concentration of metal(loid)s in plant tissues, whose presence leads to the formation of reactive oxygen species, thus causing oxidative damage. The main objective of this study was to evaluate changes in the ecophysiological behaviour of Cistus monspeliensis L., which grows spontaneously in both mine areas, in soils containing high concentrations of metal(loid)s. With this purpose, the variation of some physiological parameters was analysed in order to identify which parameters can be indicators of the plant'sresponse to oxidative stress. Representative soils from rhizosphere and plants were sampled, in the same locations, in different areas of São Domingos and Lousal mines and in an uncontaminated area nearby São Domingos. Soils were characterized for the classic properties. Multielemental total concentration was analysed in soils and plants (shoots and roots), and multielemental concentration in the available fraction of soils. Pigments (chlorophylls, anthocyanins and carotenoids), glutathione, ascorbate, H2O2 and antioxidative enzyme activities were measured in plant shoots. In general, total and available concentrations (mg/kg) of Zn (total 149-463; available 2-16), As (total 62-3030; available 0.03-1.9), Cd (total 0.3-1.2; available 0.01-0.05), Cu (total 79-375; available 0.8-10) and Pb (total 95-9210; available 0.2-40) are significantly higher in mine soils than in uncontaminated soils Zn (total 92

  16. U-Pb Geochronology of VMS mineralization in the Iberian Pyrite Belt

    Science.gov (United States)

    Barrie, Tucker C.; Amelin, Yuri; Pascual, Emilio

    2002-10-01

    A geochronology study using U-Pb isotope dilution TIMS analyses of zircon has been conducted to determine the ages of volcanic-associated massive sulfide (VMS) deposits in the Iberian Pyrite Belt (IPB), the world's most prolific VMS province. Ages have been determined for host rocks to four VMS systems that span the IPB: the giant Rio Tinto and Aljustrel districts in the central region, Lagoa Salgada to the west, and Las Cruces to the east. A sample of chloritized quartz porphyritic dacite/rhyolite in the footwall of the San Dionisio massive sulfide deposit of the Rio Tinto district is 349.76±0.90 Ma. This is taken as the best age estimate of the mineralization in the Rio Tinto district, probably the world's largest volcanogenic massive sulfide system. Two xenocrystic zircons from the same sample yielded 207Pb/206Pb ages of 414 and 416 Ma, which provide a minimum estimate for the age of the inherited component. A biotite tonalite from the Campofrio area, 3.5 km north of the center of the Rio Tinto district, is chemically similar to the felsic host rock protolith at Rio Tinto. The Campofrio sample has an age of 346.26±0.81 Ma, slightly younger and outside of the 2σ error for the Rio Tinto age; therefore, this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the Rio Tinto district. The Campofrio sample also has three zircon analyses with 207Pb/206Pb minimum ages of 534, 536, and 985 Ma, indicating inheritance from Ordovician and Neoproterozoic sources. In the Aljustrel VMS district, a U-Pb zircon age of 352.9±1.9 Ma characterizes the altered Green Tuff host rock of the Algares deposit, which is slightly older than the Rio Tinto age. Two zircons with 207Pb/206Pb ages of 531 and 571 Ma from this sample indicate inheritance from a Cambrian or older source. The age of mineralization at Lagoa Salgada is given by essentially identical ages of 356.21±0.73 and 356.4±0.8 Ma, for footwall and hanging wall samples

  17. The mobilization of toxic trace elements due to pyrite oxidation at the mega-nourishment The Sand Motor, the Netherlands

    Science.gov (United States)

    Pit, I.; Doodeman, L.; Van Heteren, S.; van Bruggen, M.; Griffioen, J.

    2014-12-01

    Pilot project "The Sand Motor" is a 21.5 million m3 nourishment of sandy sediment situated along the coast of the Netherlands close to The Hague (figure 1). It was constructed in 2011 and initially spans the shore over a 2.4 km stretch and extends up to 1 km offshore creating a hook-shaped peninsula. Due to wind, waves and currents the Sand Motor will gradually change in shape and eventually be fully incorporated into the dunes and beach. This concept is expected to be more environmentally friendly compared to traditional beach and shoreface nourishments. The aim of this project is to understand how oxidation changed the geochemistry of the sediment applied and to address possible toxic element mobilization. The sediment was taken 10 km out of shore from the sea floor, which was at a depth of 20 m. Grab samples of the upper 25 cm seabed analyzed for geochemical mapping of Southern North Sea sediments, show locally high contents of sulfur, iron and trace elements like arsenic indicating presence of pyrite with impurities. Sediment was removed to a maximum depth of 6 m below sea floor, reaching different geological layers including bog iron ore layers. Different degrees of pyrite oxidation are expected with depth at the Sand Motor. First, minimum oxidation when sediment was deposited from the ship directly by opening the bottom floor, which is now present under water at the deepest part of the nourishment. Second, limited oxidation when sediment was applied from the ship under high pressure through the air, and settled below sea level. Last, maximum oxidation when the same method was used but the sediment remains located in a surface layer having a maximum height of 4 m above sea level. At the Sand Motor, samples were taken of surface water, pore water and sediment from the surface to a depth of 10 m, the bottom of the nourishment. Analyses show that pyrite oxidation has occurred above sea level and mobilization of arsenic is present up to a maximum concentration of

  18. Synergistic effect of biogenic Fe(3+) coupled to S° oxidation on simultaneous bioleaching of Cu, Co, Zn and As from hazardous Pyrite Ash Waste.

    Science.gov (United States)

    Panda, Sandeep; Akcil, Ata; Mishra, Srabani; Erust, Ceren

    2017-03-05

    Pyrite ash, a waste by-product formed during roasting of pyrite ores, is a good source of valuable metals. The waste is associated with several environmental issues due to its dumping in sea and/or land filling. Although several other management practices are available for its utilization, the waste still awaits and calls for an eco-friendly biotechnological application for metal recovery. In the present study, chemolithotrophic meso-acidophilic iron and sulphur oxidisers were evaluated for the first time towards simultaneous mutli-metal recovery from pyrite ash. XRD and XRF analysis indicated higher amount of Hematite (Fe2O3) in the sample. ICP-OES analysis indicated concentrations of Cu>Zn>Co>As that were considered for bioleaching. Optimization studies indicated Cu - 95%, Co - 97%, Zn - 78% and As - 60% recovery within 8days at 10% pulp density, pH - 1.75, 10% (v/v) inoculum and 9g/L Fe(2+). The productivity of the bioleaching system was found to be Cu - 1696ppm/d (12% dissolution/d), Co - 338ppm/d (12.2% dissolution/d), Zn k 576ppm/d (9.8% dissolution/d) and As - 75ppm/d (7.5% dissolution/d). Synergistic actions for Fe(2+) - S° oxidation by iron and sulphur oxidisers were identified as the key drivers for enhanced metal dissolution from pyrite ash sample.

  19. Fabrication of pyrite FeS{sub 2} thin films by sulfurizing oxide precursor films deposited via successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Kaiwen; Su, Zhenghua; Yang, Jia; Han, Zili [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Liu, Fangyang, E-mail: liufangyang@csu.edu.cn [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia); Lai, Yanqing; Li, Jie [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Engineering Research Center of High Performance Battery Materials and Devices, Research Institute of Central South University in Shenzhen, Shenzhen 518057 (China); Liu, Yexiang [School of Metallurgy and Environment, Central South University, Changsha 410083 (China)

    2013-09-02

    Iron pyrite (FeS{sub 2}) is a naturally abundant and nontoxic semiconductor that can potentially be used in photovoltaic devices. In this report, pure pyrite FeS{sub 2} thin films with homogeneous morphology and ideal composition are fabricated by sulfurizing Fe{sub 2}O{sub 3} precursor thin films deposited via successive ionic layer adsorption and reaction method. The formation mechanism of FeS{sub 2} is identified by X-ray photoelectron spectroscopy. The optical and electrical (including photoelectrochemical) measurements show that the prepared pyrite FeS{sub 2} thin films have high absorption coefficient, suitable band gap, p-type conductivity and good photo-electrical conversion ability. - Highlights: • FeS{sub 2} films were prepared based on successive ionic layer adsorption and reaction method. • XPS analysis revealed the formation mechanism of FeS{sub 2} films. • The FeS{sub 2} thin films are of pure pyrite structure and p-type conductivity. • The FeS{sub 2} thin films have suitable optical and electrical properties for solar cells.

  20. Coal proximate analysis and pyrite contents by the TM/TG method: the problem of iron-bearing carbonates. [Thermomagnetic/thermogravimetric

    Energy Technology Data Exchange (ETDEWEB)

    Warne, S.S.J.

    1985-01-01

    The presence of siderite was found to give falsely high values for pyrite content in the thermomagnetic-thermogravimetric method, but other iron-bearing species had no effect. The use of DTA in N/sub 2/ and CO/sub 2/ is proposed as a method of detecting Fe carbonates.

  1. Photoelectrochemistry: Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions  (Adv. Mater. 43/2016, Back Cover)

    NARCIS (Netherlands)

    Wu, Longfei; Dzade, N.Y.|info:eu-repo/dai/nl/41249311X; Gao, L.; Scanlon, D. O.; Öztürk, Z.; Hollingsworth, N.; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397; Hensen, E. J. M.; de Leeuw, Nora H.|info:eu-repo/dai/nl/376421061; Hofmann, J. P.

    2016-01-01

    The beneficial role of marcasite in pyrite thin films for photoelectrochemical applications is reported by J. P. Hofmann and co-workers on page 9602. A bulk heterojunction with staggered band alignment at the pyrite–marcasite interface enhances charge-carrier separation and leads to a dramatic

  2. Photoelectrochemistry: Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions  (Adv. Mater. 43/2016, Back Cover)

    OpenAIRE

    Wu, Longfei; Dzade, N.Y.; Gao, L; Scanlon, D. O.; Öztürk, Z.; Hollingsworth, N.; Weckhuysen, B. M.; Hensen, E. J. M.; de Leeuw, Nora H.; Hofmann, J.P.

    2016-01-01

    The beneficial role of marcasite in pyrite thin films for photoelectrochemical applications is reported by J. P. Hofmann and co-workers on page 9602. A bulk heterojunction with staggered band alignment at the pyrite–marcasite interface enhances charge-carrier separation and leads to a dramatic increase of photocurrent in the FeS2 films.

  3. Primary multiple sulfur isotopic compositions of pyrite in 2.7 Ga shales from the Joy Lake sequence (Superior Province) show felsic volcanic array-like signature

    Science.gov (United States)

    Li, Jianghanyang; Zhang, Zhe; Stern, Richard A.; Hannah, Judith L.; Stein, Holly J.; Yang, Gang; Li, Long

    2017-04-01

    Multiple sulfur isotopes provide a powerful tool to study photochemical and biological processes controlling the Archean sulfur cycle and infer related atmospheric and marine environments. However, our understanding of early Earth's environment remains limited by the availability of well-preserved geological samples, as most Archean sedimentary rocks have experienced some degree of metamorphic alteration. To evaluate sulfur isotopic behavior during post-depositional processes and elucidate the sulfur cycle at 2.7 Ga, we use high-resolution in situ analytical techniques (EPMA and SIMS) to determine elemental compositions and multiple sulfur isotopic compositions of large diagenetic pyrite nodules and fine-grained secondary pyrite disseminated in quartz veins (formed during a lower greenschist metamorphic event) in shales from the 2.7 Ga Joy Lake sequence in the southwest Superior Province. Results show that trace metals and sulfur in the secondary pyrite were derived from both metamorphic fluid and pre-existing diagenetic pyrite. Diagenetic pyrite nodules could have been partially dissolved by metamorphic fluid. But the surviving nodules show elemental and isotopic features different from those of the deduced metamorphic fluid endmember, suggesting the nodules were not geochemically altered by metamorphism, and thus preserve primary isotopic signatures acquired during diagenesis. The sulfur isotopic ratios of pyrite nodules show strong variations, with decreasing δ34S values and increasing Δ33S values from cores to rims. This negative Δ33S-δ34S relationship is different from the commonly observed 'Archean reference line' defined by most Archean pyrite data, but similar to the 'felsic volcanic array'. Our observation provides a first possible case from 2.7 Ga, the age of peak crustal growth in the Archean, to support the hypothesis that photochemical pathways could be different under conditions of intense volcanic emission. This study also shows that high

  4. The case for metamorphic base metal mineralization: pyrite chemical, Cu and S isotope data from the Cu-Zn deposit at Kupferberg in Bavaria, Germany

    Science.gov (United States)

    Höhn, S.; Frimmel, H. E.; Debaille, V.; Pašava, J.; Kuulmann, L.; Debouge, W.

    2017-01-01

    The stratiform Cu-Zn sulfide deposit at Kupferberg in Germany represents Bavaria's largest historic base metal producer. The deposit is hosted by Early Paleozoic volcano-sedimentary strata at the margin of a high-grade allochthonous metamorphic complex. The present paper reports on the first Cu and S isotope data as well as trace element analyses of pyrite from this unusual deposit. The new data point to syn-orogenic mineralization that was driven by metamorphic fluids during nappe emplacement. Primary Cu ore occurs as texturally late chalcopyrite within stratiform laminated pyrite in black shale in two different tectonostratigraphic units of very low and low metamorphic grade, respectively, that were juxtaposed during the Variscan orogeny. Trace element contents of different pyrite types suggest the presence of at least one hydrothermal pyrite generation (mean Co/Ni = 35), with the other pyrite types being syn-sedimentary/early diagenetic (mean Co/Ni = 3.7). Copper isotope analyses yielded a narrow δ65Cu range of -0.26 to 0.36‰ for all ore types suggesting a hypogene origin for the principal chalcopyrite mineralization. The ore lenses in the two different tectonostratigraphic units differ with regard to their δ34S values, but little difference exists between poorly and strongly mineralized domains within a given locality. A genetic model is proposed in which syn-sedimentary/early diagenetic pyrite with subordinate chalcopyrite and sphalerite formed in black shale beds in the two different stratigraphic units, followed by late-tectonic strata-internal, hydrothermal mobilization of Fe, Cu, and Zn during syn-orogenic thrusting, which concentrated especially Cu to ore grade. In agreement with this model, Cu distribution in stream sediments in this region shows distinct enrichments bound to the margin of the allochthonous complex. Thus, Kupferberg can be considered a rare example of a syn-orogenic Cu deposit with the Cu probably being derived from syn

  5. Electro-generative mechanism for simultaneous leaching of pyrite and MnO2 in presence of A. ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A dual cell system was used to study the output power, output voltage, galvanic polarization of anode and cathode, and the relationship between the electric quantity(Q) and some factors, such as the dissolved Fe2+ magnitude, the time in the electrogenerative simultaneous leaching with bacteria(BEGSL) and without bacteria(EGSL). A three-electrode system was adopted to study their individual self-corrosion current, which was smaller compared with the galvanic current. The results show that the output power and voltage in BEGSL are higher than those in EGSL. The accumulated sulfur on the surface of sulfides produced in BEGSL can be oxidized by A. ferrooxidans, and the ratio of biologic electric quantity reaches 51.50% in 72 h. The first stage both in EGSL and in BEGSL is the dissolution of pyrite on the surface to ferrous ion and sulfur element, which was oxidized by A. ferrooxidans in the further procedure.

  6. Drainage waters affected by pyrite oxidation in a coal mine in Galicia (NW Spain): composition and mineral stability

    Energy Technology Data Exchange (ETDEWEB)

    Monterroso, C.; Macias, F. [University of Santiago (Spain)

    1998-05-14

    The quality of the drainage water from the As Puentes lignite mine dump (Galicia, Spain) was evaluated along with the geochemical processes which determine its composition. Analysis of water form different areas of the dump was carried out at monthly intervals over a period of 2 years. In general, the water samples were characterised by the presence of elevated concentrations of Fe{sub 2}, SO{sub 4}{sup 2-} and H{sup +}, liberated from the oxidation of pyrite, and of Si, Al, Ca, and Mg derived from the accelerated mineral hydrolysis. At the same time, very high concentrations of elements, in particular Mn, Zn, Ni and Co, which were liberated from both processes, were recorded. The best water quality was found in the most recently constructed areas of the dump.

  7. [XRD, FTIR and XPS analysis of oxidized particles from Dongshengmiao pyrite-polymetallic sulfide deposit, inner Mongolia].

    Science.gov (United States)

    Yuan, Xue-Ling; Cao, Jian-Jin; Xie, Fang-Yan; Yang, Xiao-Jie; Yan, Hong-Bin; Lai, Pei-Xin; Wang, Zheng-Hai; Zeng, Jian-Nian

    2013-01-01

    In the present paper, characteristics of material compositions, phase structures, surface element states, and transformation mechanism of oxidized particles from Dongshengmiao pyrite-polymetallic sulfide deposit were studied using modern analytical testing technology including XRD, FTIR and XPS. The results show that the samples consist of gypsum, calcite, quartz, muscovite, goethite, organic matter, etc. Primary ore in deep oxidation zone mainly under went such processes as oxidization, hydrolysis, dehydration and carbonation. Compared to the surface oxidation zone of arid and extremely arid regions in the northwestern China, the oxidation process and oxidizing condition of the deep oxidation zone were less complex. New mineral type was also not found, and extensively developed sulfate minerals were rare to be seen. The research results can not only be applied to mineral identification of oxidized particles from this type of ore deposit but also play an important role in ore exploration, mining, mineral processing, etc.

  8. Quantifying adhesion of acidophilic bioleaching bacteria to silica and pyrite by atomic force microscopy with a bacterial probe.

    Science.gov (United States)

    Diao, Mengxue; Taran, Elena; Mahler, Stephen; Nguyen, Tuan A H; Nguyen, Anh V

    2014-03-01

    The adhesion of acidophilic bacteria to mineral surfaces is an important phenomenon in bioleaching processes. In this study, functionalized colloidal probes covered by bioleaching bacterial cells (Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans) were developed and used to sense specific adhesion forces to a silica surface and a pyrite surface in various solutions. Experimentally, recorded retraction curves of A. thiooxidans revealed sawtooth features that were in good agreement with the wormlike chain model, while that of L. ferrooxidans exhibited stair-step separation. The magnitudes of adhesion forces and snap-off distances were strongly influenced by the ionic strength and pH. Macroscopic surface properties including hydrophobicity and surface potential for bacterial cells and substrata were measured by a sessile drop method and microelectrophoresis. The ATR-FTIR spectra indicated the presence of different types of biopolymers on two strains of bacteria.

  9. Petrography, geochemistry and geochronology of granite hosted rhyodacites associated with a disseminated pyrite mineralization (Arnolz, Southern Bohemian Massif, Austria)

    Science.gov (United States)

    Göd, Richard; Kurzweil, Johannes; Klötzli, Urs

    2017-04-01

    The study focuses on a subvolcanic rhyodacite dyke intruding a fine grained biotite granite and paragneisses of the South Bohemian Massif, part of the Variscan Orogenic Belt in Central Europe. The subvertical dyke strikes NNE, displays a thickness of about 30 m and has been traced by boulder mapping for approximately 7 km. The rhyodacites have been affected by two hydrothermal fluids. An older one of oxidizing condition giving rise to a reddish to brownish type of rock (Type I) and a younger fluid of reducing condition causing a greenish variety (Type II). The hydrothermal alteration is associated with the formation of the clay minerals chlorite, sericite, kaolinite and smectite and a disseminated pyrite mineralization. Bulk chemistries of the rhyodacites emphasize the hydrothermal alterations to be isochemical with the exception of sulphur enriched up to a maximum of 0.6 wt%. Trace element composition of the rhyodacites points to a barren geochemical environment in terms of base and precious elements. Sulphur isotope investigations of pyrites from the rhyodacites and the hosting granites respectively yield d34S data ranging from +0.07 to -2.22 ‰, emphasizing a magmatic origin of the sulphur. Geochronological investigations yield in situ U/Pb zircon ages of 312 ± 4 Ma for the biotite granite and of 292 ± 4 Ma for the rhyodacitic dykes indicating a time gap of ≈ 20 Ma between these two intrusive events. A contemporaneous but geochemically specialized granitic intrusion associated with NW striking "felsitic" dykes occurs about 10 to 20 km to the NW of Arnolz. However, the rhyodacites around Arnolz differ significantly from these felsitic dykes in their geochemistry and alteration phenomena which points to a different magmatic source. This coincides with a change in the orientation of the dykes from a NW direction controlling the geochemically specialized intrusions in the NW to a dominating NNE direction mirrored by the studied rhyodacites at Arnolz.

  10. Monitoring the Extent of Contamination from Acid Mine Drainage in the Iberian Pyrite Belt (SW Spain Using Hyperspectral Imagery

    Directory of Open Access Journals (Sweden)

    Asuncion Riaza

    2011-10-01

    Full Text Available Monitoring mine waste from sulfide deposits by hyperspectral remote sensing can be used to predict surface water quality by quantitatively estimating acid drainage and metal contamination on a yearly basis. In addition, analysis of the mineralogy of surface crusts rich in soluble salts can provide a record of annual humidity and temperature. In fact, temporal monitoring of salt efflorescence from mine wastes at a mine site in the Iberian Pyrite Belt (Huelva, Spain has been achieved using hyperspectral airborne Hymap data. Furthermore, climate variability estimates are possible based on oxidation stages derived from well-known sequences of minerals, by tracing sulfide oxidation intensity using archive spectral libraries. Thus, airborne and spaceborne hyperspectral remote sensing data can be used to provide a short-term record of climate change, and represent a useful set of tools for assessing environmental geoindicators in semi-arid areas. Spectral and geomorphological indicators can be monitored on a regular basis through image processing, supported by field and laboratory spectral data. In fact, hyperspectral image analysis is one of the methods selected by the Joint Research Centre of the European Community (Ispra, Italy to study abandoned mine sites, in order to assess the enforcement of the European Mine Waste Directive (2006/21/EC of the European Parliament and of the Council 15 March 2006 on the management of waste from extractive industries (Official Journal of the European Union, 11 April 2006. The pyrite belt in Andalucia has been selected as one of the core mission test sites for the PECOMINES II program (Cracow, November 2005, using imaging spectroscopy; and this technique is expected to be implemented as a monitoring tool by the Environmental Net of Andalucía (REDIAM, Junta de Andalucía, Spain.

  11. Petrography, geochemistry and geochronology of granite hosted rhyodacites associated with a disseminated pyrite mineralization (Arnolz, Southern Bohemian Massif, Austria)

    Science.gov (United States)

    Göd, Richard; Kurzweil, Johannes; Klötzli, Urs

    2016-09-01

    The study focuses on a subvolcanic rhyodacite dyke intruding a fine grained biotite granite and paragneisses of the South Bohemian Massif, part of the Variscan Orogenic Belt in Central Europe. The subvertical dyke strikes NNE, displays a thickness of about 30 m and has been traced by boulder mapping for approximately 7 km. The rhyodacites have been affected by two hydrothermal fluids. An older one of oxidizing condition giving rise to a reddish to brownish type of rock (Type I) and a younger fluid of reducing condition causing a greenish variety (Type II). The hydrothermal alteration is associated with the formation of the clay minerals chlorite, sericite, kaolinite and smectite and a disseminated pyrite mineralization. Bulk chemistries of the rhyodacites emphasize the hydrothermal alterations to be isochemical with the exception of sulphur enriched up to a maximum of 0.6 wt%. Trace element composition of the rhyodacites points to a barren geochemical environment in terms of base and precious elements. Sulphur isotope investigations of pyrites from the rhyodacites and the hosting granites respectively yield d34S data ranging from +0.07 to -2.22 ‰, emphasizing a magmatic origin of the sulphur. Geochronological investigations yield in situ U/Pb zircon ages of 312 ± 4 Ma for the biotite granite and of 292 ± 4 Ma for the rhyodacitic dykes indicating a time gap of ≈ 20 Ma between these two intrusive events. A contemporaneous but geochemically specialized granitic intrusion associated with NW striking "felsitic" dykes occurs about 10 to 20 km to the NW of Arnolz. However, the rhyodacites around Arnolz differ significantly from these felsitic dykes in their geochemistry and alteration phenomena which points to a different magmatic source. This coincides with a change in the orientation of the dykes from a NW direction controlling the geochemically specialized intrusions in the NW to a dominating NNE direction mirrored by the studied rhyodacites at Arnolz.

  12. Geochemistry of pyrite and chalcopyrite from an active black smoker in 49.6°E Southwest Indian Ridge

    Science.gov (United States)

    Yuan, Bo; Yang, Yaomin; Yu, Hongjun; Zhao, Yuexia; Ding, Qingfeng; Yang, Jichao; Tang, Xin

    2017-06-01

    Active hydrothermal chimneys, as the product of submarine hydrothermal activity, can be used to determine the fluid evolution and formation process of potential volcanic-hosted massive sulfide deposits. A hard-won specimen from an active hydrothermal chimney was collected in the 49.6°E ultraslow-spreading Southwest Indian Ridge (SWIR) field through a television-guided grab. A geochemical study of prominent sulfide (e.g., pyrite and chalcopyrite) included in this sample was performed using laser ablation inductively coupled plasma mass spectroscopy. The early sulfides produced at low temperature are of disseminated fine-grained anhedral morphology, whereas the late ones with massive, coarse euhedral features precipitated in a high-temperature setting. The systematic variations in the contents of minor and trace elements are apparently related to the crystallization sequence, as well as to texture. Micro-disseminated anhedral sulfides rich in Pb, As, Ni, Ba, Mn, Mo, U, and V were formed during the initial chimney wall growth, whereas those rich in Sn, Se, and Co with massive, coarse euhedral morphology were formed within the late metallogenic stage. The hydrothermal fluid composition has experienced a great change during the chimney growth. Such a conclusion is consistent with that indicated by using principal component analysis, which is a powerful statistical analysis method widely used to project multidimensional datasets (e.g., element contents in different mineral phases) into a few directions. This distribution pattern points to crystallographic controls on minor and trace element uptake during chimney growth, occurring with concomitant variations in the fluid composition evolutionary history. In this pyrite-chalcopyrite-bearing active hydrothermal chimney at the SWIR, the metal concentration and precipitation of sulfides largely occurred at the seafloor as a result of mixing between the upwelling hot hydrothermal fluid and cold seawater. Over the course of

  13. Germination and Seedling Growth of Perennial Ryegrass in Acid Sulfate Soil Treated by Pyrite Nano-Encapsulation

    Science.gov (United States)

    Lee, J.; Kim, J.; Yi, J.; Kim, T.

    2007-05-01

    The trial pot experiment was conducted to validate the effect of encapsulation in reduction of acid rock drainage. Six different treatments were performed: A = control, four times spraying of distilled water; B = four times of 0.01 M H2O2; C = once-encapsulated and three times spraying of distilled water; D = twice-encapsulated and twice spraying of distilled water; E = three times-encapsulated and once spraying of distilled water and F = four times-encapsulated for the acid sulfate soil with pyrite bearing andesite powder and sand. After the encapsulation treatment, the perennial ryegrass (Loium perenne) was sowed to evaluate germination rate and growth for three months. The leachate was examined for the chemical properties. The leachate from the A pot (control) is characterized as acidic (pH below 3) and high concentrations of SO4-2: 12,022 mg/L, Al: 85.8 mg/L and Mn: 34.1 mg/L which can be toxic effect to the plant growth. However, the leachate from encapsulated pots showed near neutral (pH 6 to 7) and low concentrations of SO4-2 (below 3,000 mg/L), Al (below 45mg/L) and Mn (24 gm/L). The frequency of encapsulation treatment is related to reduction of acidic drainage. It was hard to identify the significant difference of the seed germination rate of ryegrass between the treatments, although root and shoot growth showed three times difference between the control (1.90g/pot) and four times encapsulated treatment (6.33g/pot) after 2 month growth. It is suggested that encapsulation of pyrite in acid sulfate soil causes the reduction of acidic drainage resulting in the higher growth of herbaceous plants.

  14. Tridimensional modelling and resource estimation of the mining waste piles of São Domingos mine, Iberian Pyrite Belt, Portugal

    Science.gov (United States)

    Vieira, Alexandre; Matos, João; Lopes, Luis; Martins, Ruben

    2016-04-01

    Located in the Iberian Pyrite Belt (IPB) northern sector, near the Portuguese/Spanish border, the outcropping São Domingos deposit was mined since Roman time. Between 1854 and 1966 the Mason & Barry Company developed open pit excavation until 120 m depth and underground mining until 420 m depth. The São Domingos subvertical deposit is associated with felsic volcanics and black shales of the IPB Volcano-Sedimentary Complex and is represented by massive sulphide and stockwork ore (py, cpy, sph, ga, tt, aspy) and related supergene enrichment ore (hematite gossan and covellite/chalcocite). Different mine waste classes were mapped around the old open pit: gossan (W1), felsic volcanic and shales (W2), shales (W3) and mining waste landfill (W4). Using the LNEG (Portuguese Geological Survey) CONASA database (company historical mining waste characterization based on 162 shafts and 160 reverse circulation boreholes), a methodology for tridimensional modelling mining waste pile was followed, and a new mining waste resource is presented. Considering some constraints to waste removal, such as the Mina de São Domingos village proximity of the wastes, the industrial and archaeological patrimony (e.g., mining infrastructures, roman galleries), different resource scenarios were considered: unconditioned resources (total estimates) and conditioned resources (only the volumes without removal constraints considered). Using block modelling (SURPAC software) a mineral inferred resource of 2.38 Mt @ 0.77 g/t Au and 8.26 g/t Ag is estimated in unconditioned volumes of waste. Considering all evaluated wastes, including village areas, an inferred resource of 4.0 Mt @ 0.64 g/t Au and 7.30 g/t Ag is presented, corresponding to a total metal content of 82,878 oz t Au and 955,753 oz t Ag. Keywords. São Domingos mine, mining waste resources, mining waste pile modelling, Iberian Pyrite Belt, Portugal

  15. Re-Os isotopic and trace element compositions of pyrite and origin of the Cretaceous Jinchang porphyry Cu-Au deposit, Heilongjiang Province, NE China

    Science.gov (United States)

    Zhang, Peng; Huang, Xiao-Wen; Cui, Bin; Wang, Bo-Chao; Yin, Yi-Fan; Wang, Jing-Rui

    2016-11-01

    The Jinchang Cu-Au deposit in Northeast China contains more than 76 tons of Au and 4683 tons of Cu with average ore grades of 11.34 g/t Au and 1.44% Cu. The deposit is typical of porphyry types and consists of gold orebodies mainly hosted in a ∼113 Ma granitic porphyry and breccia pipes within the porphyry intrusion. Mineralization is closely associated with early potassic alteration and late phyllic alteration. Pyrite is the main Au-bearing mineral and contains 1.48-18.9 ppb Re and 11.4-38 ppt common Os. Extremely low common Os concentrations and high Re/Os ratios are indicative of derivation of ore-forming materials from the crust. Low Re in pyrite from the Jinchang deposit may indicate a mixing source of mantle and crust or a crustal source. Five Re-Os isotopic analyses yield a model 1 isochron age of 114 ± 22 Ma (2σ, MSWD = 0.15), similar to the age of the host porphyry. Pyrite contains detectable Co, Ni, Cu, Zn, As, Ag, Au, Sb, Pb and Bi. Pyrite has Co/Ni ratios similar to that of volcanogenic and hydrothermal sulfide deposits, indicating a magmatic-hydrothermal origin, and has Au and As contents similar to that of porphyry-epithermal systems. Pyrite grains from potassic and phyllic alteration stages have different trace element contents, reflecting the evolution of ore-forming fluids from magmatic dominated to magmatic mixed with meteoric water. In combination with regional geology, our new results are suggestive of origin of the Jinchang Cu-Au deposit from contemporary intrusions of granitic porphyries related to the Early Cretaceous subduction of the Paleo-Pacific plate.

  16. Deciphering a multistage history affecting U-Cu(-Fe) mineralization in the Singhbhum Shear Zone, eastern India, using pyrite textures and compositions in the Turamdih U-Cu(-Fe) deposit

    Science.gov (United States)

    Pal, Dipak C.; Barton, Mark D.; Sarangi, A. K.

    2009-01-01

    The ˜200-km-long intensely deformed Singhbhum Shear Zone (SSZ) in eastern India hosts India’s largest U and Cu deposits and related Fe mineralization. The SSZ separates an Archaean cratonic nucleus to the south from a Mesoproterozoic fold belt in the North and has a complex geologic history that obscures the origin of the contained iron-oxide-rich mineral deposits. This study investigates aspects of the history of mineralization in the SSZ by utilizing new petrographic and electron microprobe observations of pyrite textures and zoning in the Turamdih U-Cu(-Fe) deposit. Mineralization at Turamdih is hosted in intensively deformed quartz-chlorite schist. Sulfides and oxides include, in inferred order of development: (a) magmatic Fe(-Ti-Cr) oxide and Fe-Cu(-Ni) sulfide minerals inferred to be magmatic (?) in origin; followed by (b) uranium, Fe-oxide, and Fe-Cu(-Co) sulfide minerals that predate most or all ductile deformation, and are inferred to be of hydrothermal origin; and (c) Fe-Cu sulfides that were generated during and postdating ductile deformation. These features are associated with the formation of three compositionally and texturally distinct pyrites. Pyrite (type-A), typically in globular-semiglobular composite inclusions of pyrite plus chalcopyrite in magnetite, is characterized by very high Ni content (up to 30,700 ppm) and low Co to Ni ratios (0.01-0.61). The textural and compositional characteristics of associated chalcopyrite and rare pyrrhotite suggest that this pyrite could be linked to the magmatic event via selective replacement of magmatic pyrrhotite. Alternatively, this pyrite and associated sulfide inclusions might be cogenetic with hydrothermal Fe-oxide. Type-B pyrite that forms elongate grains and irregular relics and cores of pyrite with high Co contents (up to 23,630 ppm) and high Co to Ni ratios (7.2-140.9) are interpreted to be related to hydrothermal mineralization predating ductile deformation. A third generation of pyrite (type C

  17. Trace element content of sedimentary pyrite as a new proxy for deep-time ocean-atmosphere evolution

    Science.gov (United States)

    Large, Ross R.; Halpin, Jacqueline A.; Danyushevsky, Leonid V.; Maslennikov, Valeriy V.; Bull, Stuart W.; Long, John A.; Gregory, Daniel D.; Lounejeva, Elena; Lyons, Timothy W.; Sack, Patrick J.; McGoldrick, Peter J.; Calver, Clive R.

    2014-03-01

    Sedimentary pyrite formed in the water column, or during diagenesis in organic muds, provides an accessible proxy for seawater chemistry in the marine rock record. Except for Mo, U, Ni and Cr, surprisingly little is known about trace element trends in the deep time oceans, even though they are critical to developing better models for the evolution of the Earth's atmosphere and evolutionary pathways of life. Here we introduce a novel approach to simultaneously quantify a suite of trace elements in sedimentary pyrite from marine black shales. These trace element concentrations, at least in a first-order sense, track the primary elemental abundances in coeval seawater. In general, the trace element patterns show significant variation of several orders of magnitude in the Archaean and Phanerozoic, but less variation on longer wavelengths in the Proterozoic. Certain trace elements (e.g., Ni, Co, As, Cr) have generally decreased in the oceans through the Precambrian, other elements (e.g., Mo, Zn, Mn) have generally increased, and a further group initially increased and then decreased (e.g., Se and U). These changes appear to be controlled by many factors, in particular: 1) oxygenation cycles of the Earth's ocean-atmosphere system, 2) the composition of exposed crustal rocks, 3) long term rates of continental erosion, and 4) cycles of ocean anoxia. We show that Ni and Co content of seawater is affected by global Large Igneous Province events, whereas redox sensitive trace elements such as Se and Mo are affected by atmosphere oxygenation. Positive jumps in Mo and Se concentrations prior to the Great Oxidation Event (GOE1, c. 2500 Ma) suggest pulses of oxygenation may have occurred as early as 2950 Ma. A flat to declining pattern of many biologically important nutrient elements through the mid to late Proterozoic may relate to declining atmosphere O2, and supports previous models of nutrient deficiency inhibiting marine evolution during this period. These trace elements (Mo

  18. Assessing Soil Quality in Areas Affected by Sulfide Mining. Application to Soils in the Iberian Pyrite Belt (SW Spain

    Directory of Open Access Journals (Sweden)

    Isabel González

    2011-11-01

    Full Text Available The characterization, evaluation and remediation of polluted soils is one of the present environmental challenges to be addressed in the coming years. The origin of trace elements in soils can be either geogenic or anthropogenic, but only the latter is interesting from a legal point of view. The hazard of the pollutants in the soils not only depends on their total concentration, but particularly on their availability. The mobility of the trace elements depends on their speciation, and it is also affected by several soil parameters. Mining activity is one of the most important anthropogenic causes of soil pollution. As a case study, this work is focused in the Riotinto mining area (Iberian Pyrite Belt, IPB, SW Spain. The IPB is one of the most important metallogenic provinces in the world and it has been exploited for thousands of years. The disposal of mining residues has produced important sources of contamination by trace elements and acidic waters affecting soils and rivers. In addition to these problems, the closure of mines in the Pyrite Belt at the end of the 20th Century has led to a great loss of employment, which has caused the development of an intensive agriculture of citrus fruits as a new source of income. The intensive growing of citrus fruits and the traditional subsistence agriculture have been developed surrounding the mining areas and on floodplains near to mining sites. The level of soil pollution has not been taken into account in these cases, nor has its impact on the health of the inhabitants of these areas. Therefore, it is of great interest to study the current state of the cultivated soils and the sources and types of contaminants derived from mining activity in order to program its decontamination, where appropriate, according to legislation. In order to know the present and future hazard posed by the soils chemical and mineralogical speciation has been carried out, given that the availability of a metal depends on the

  19. Influence factors of pyrite promotion on the bioleaching of chalcopyrite%黄铁矿促进黄铜矿微生物浸出影响因素

    Institute of Scientific and Technical Information of China (English)

    莫晓兰; 林海; 傅开彬; 徐承焱; 汪涵

    2012-01-01

    Chalcopyrite-pyrite bioleaching tests were performed with shaking flasks by Aeidithiobacillusferrooxidans. The research focused on the effects of basic salt mediums, pyrite-to-chalcopyrite mass ratio and mineral size distribution. It is found that chaleopyrite bioleaching can be promoted by pyrite, The leaching rate of copper in the iron-free 9K medium in pyrite-chaleopyrite bioleaching is 1.68 times as large as that in the 9K medium. The leaching of copper is better using a wide size range of minerals and the leaching rate of copper is related to the mass ratio of pyrite to chalcopyrite. When the mass ratio is 2: 2, the highest leaching rate of copper is ob- tained to be 45.58%. The content of pyrite is of the essence in affecting the leaching rate level of copper. At a mass ratio of pyrite to chalcopyrite no more than 5:2 the oxidation of Acidithiobacillus ferrooxidans plays an important role in the bioleaching, but when the mass ratio is 10:2 the galvanic effect between the two sulphide minerals mainly influences the bioleaehing. X-ray diffraction analyses of leaching residues indicate that the generation of jarosite in the iron-free 9K medium is less than that in the 9K medium, FeSO4 in the 9K medium can be replaced by pyrite, the galvanic effect forms with chaleopyrite, and therefore the bioleaehing efficiency of copper is increased.%采用摇瓶实验,以氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,At.f)浸出黄铁矿--黄铜矿,重点研究了基础培养基、矿物配比和粒度组成等因素的影响.黄铁矿能促进黄铜矿的微生物浸出,以采用无Fe 9K培养基效果较好,它对应铜浸出率是9K培养基的1.68倍;采用宽粒级矿物时铜浸出效果较好,且铜浸出率与黄铁矿和黄铜矿的质量比有关,当质量比为2∶2时铜浸出率最高可达45.58%;黄铁矿含量大小是影响铜浸出率高低的实质,当质量比小于等于5∶2时以At.f菌的氧化作用为主,当质量比为10∶2时以硫

  20. The potential use of storm water and effluent from a constructed wetland for re-vegetating a degraded pyrite trail in Queen Elizabeth National Park, Uganda

    Science.gov (United States)

    Osaliya, R.; Kansiime, F.; Oryem-Origa, H.; Kateyo, E.

    During the operation of the Kilembe Mines (copper mining) a cobaltiferous stockpile was constructed, which began to erode after the closure of the mines in the early 1970s. The erosion of the pyrite stockpile resulted in a large acid trail all the way to Lake George (a Ramsar site). The acid trail contaminated a large area of Queen Elizabeth National Park (QENP) resulting in the death of most of the shallow-rooted vegetation. Processes and conditions created by storm water and effluent from a constructed wetland were assessed for vegetation regeneration in the degraded QENP pyrite trail. Cynodon dactylon, Imperata cylindrica and Hyparrhenia filipendula dominated the regeneration zone (RZ) where storm water and effluent from a constructed wetland was flowing; and the adjacent unpolluted area (UP) with importance value indices of 186.4 and 83.3 respectively. Typha latifolia and C. dactylon formed two distinct vegetation sub-zones within the RZ with the former inhabiting areas with a higher water table. Soil pH was significantly higher in the RZ, followed by UP and bare pyrite trail (BPT) at both 0-15 cm and 16-30 cm depths. Soil electrical conductivity was not significantly different in the RZ and BPT but significantly higher than that in UP for both depths. For 0-15 cm depth, RZ had significantly higher concentrations of copper than BPT and UP which had similar concentrations. Still at this depth (0-15 cm), the unpolluted area had significantly higher concentrations of total phosphorus and total nitrogen than the regeneration zone and the bare pyrite trail which had similar concentrations. The RZ dominated by Typha had significantly higher concentrations of TP and TN compared to the RZ dominated by Cynodon. The concentrations of NH 4-N were significantly lower in Typha regeneration zone than in CRZ at 0-15 cm depth but similar at 16-30 cm depth. At 16-30 cm depth, concentrations of copper were significantly higher in the regeneration zone followed by the bare pyrite

  1. 硫酸烧渣中铁的综合利用研究进展%Research Progress on the Comprehensive Utilization of Iron from Pyrite Cinder

    Institute of Scientific and Technical Information of China (English)

    金程; 李登新

    2011-01-01

    The comprehensive utilization of iron in pyrite cinder as well as the new research trend were studied. The suitable conditions and the existing problems in each extracting process of iron from pyrite cinder were intensively analyzed and contrasted. It indicated that the direct activation acid-leaching method owns a good prospect in industrial application with advantages of simple process and energy saving etc.%综述了硫酸烧渣中铁的综合利用途径及最新研究进展.重点对硫酸烧渣中铁的各种提取方法的适用条件、存在问题进行了分析和对比,指出直接活化酸溶法具有工艺简单、节能环保等优点,工业化应用前景良好.

  2. Model study of pyrite demineralization by hydrogen peroxide oxidation at 30 {sup o}C in the presence of metal ions (Ni{sup 2+}, Co{sup 2+} and Sn{sup 2+})

    Energy Technology Data Exchange (ETDEWEB)

    Borah, Dipu [Department of Chemistry, Pragjyotika J. College, Titabar 785 630, Assam (India); Baruah, Mrinal K.; Gogoi, Probin C. [Department of Chemistry, NNS College, Titabar 785 630, Assam (India)

    2005-04-25

    Dissolution of pyrite involving oxidation by hydrogen peroxide (H{sub 2}O{sub 2}) in the presence of metal ions (Ni{sup 2+}, Co{sup 2+} and Sn{sup 2+}) has been investigated. Before oxidation, pure and well crystalline structure of the acid washed pyrite sample, used in the present investigation, was confirmed by X-ray diffraction and chemical analysis. Oxidation of pyrite was examined by the determination of soluble sulfur. The rate of oxidation of pyrite with H{sub 2}O{sub 2} is best represented by determining the rates of total soluble sulfur production. Each experiment was carried out for short (1-4 h) and extended (24 h) time periods. Pyrite is oxidized by H{sub 2}O{sub 2} (1:1) up to the extent of 31.3% at short time period, which however remained the same even at extended time period. Increased amount of soluble sulfur has been observed when pyrite was oxidized by H{sub 2}O{sub 2} (1:1) in the presence of Ni{sup 2+} or Co{sup 2+} or Sn{sup 2+} ion at short time period. The effectiveness of these metal ions in relation to pyrite oxidation at short time period decreases in the order Co{sup 2+}>Sn{sup 2+}>Ni{sup 2+}, while at extended time period the order is Co{sup 2+}>Ni{sup 2+}>Sn{sup 2+}. With Co{sup 2+} ion, the highest pyrite oxidation is obtained both at short (34.0%) and extended (35.0%) time period, while it is the lowest 31.3% with Ni{sup 2+} ion at short time and 25.3% with Sn{sup 2+} ion at extended time period. The effect of chloride ion on the rate of oxidation of pyrite is not pronounced in the metal ion containing systems. Substantial depletion in the concentration of externally added metal ions is in good agreement with the level of oxidation and infers certain adsorption or precipitation of metal ions on pyrite surface. The results of this study throw a new light of the influence of metal ions in the dissolution of pyrite in oxidation systems and has considerable applications in fields of demineralization, desulfurization and environmental

  3. Isolation and characterization of bacteria on the drainage water from Ratones mine and its behaviour on pyrite; Aislamiento y caracterizacion de bacterias en aguas de la mina de ratones y su comportamiento con pirita

    Energy Technology Data Exchange (ETDEWEB)

    Merino, J. L.; Saez, R. M.

    1974-07-01

    This paper describes some of the studies made about iron and sulfur oxidizing bacteria on the drainage water from Ratones mine. Different liquid and solid media were utilized as well as some energy sources, ferrous sulphate, thiosulfate and sulfur. Some experiment were al so realized on museum grade pyrite aimed at determining the possibilities of applying the mentioned bacteria on the leaching of pyrite and subsequently on the leaching of uranium ores. (Author) 27 refs.

  4. Super-heavy pyrite (δ34Spyr > δ34SCAS) in the terminal Proterozoic Nama Group, Southern Namibia: Implications for atmospheric oxygen and seawater sulfate at the dawn of animal life

    Science.gov (United States)

    Ries, J. B.; Fike, D. A.; Pratt, L.; Lyons, T. W.; Grotzinger, J. P.

    2009-12-01

    Sulfur isotope analysis (δ34S) of well-preserved carbonates spanning a ca. 10 Myr interval of the terminal Proterozoic Nama Group in Namibia, southwestern Africa, reveals that pyrite is consistently enriched in 34S relative to coeval seawater sulfate as preserved in carbonate associated sulfate (CAS). This observation is not consistent with the current paradigm for interpreting the geologic record of sulfur isotopes, which assumes that pyrite δ34S (δ34Spyr) will be equal to or less than co-occurring CAS δ34S (δ34SCAS) due to the kinetic isotope effect of bacterial sulfate reduction (BSR) that favors the lighter isotope of sulfur (32S) during sulfur-oxygen bond-breakage. Although the precise mechanism of pyrite enrichment is debatable, our combined observations of extremely enriched pyrite, low concentrations of CAS and pyrite, and high frequency fluctuations in δ34SCAS and δ34Spyr throughout the Nama Group carbonates point to very low concentrations of sulfate in portions of the terminal Proterozoic ocean. The additional occurrence of 34S-enriched pyrite in contemporaneous terminal Proterozoic sections from Poland and Canada reveal that low seawater sulfate may have been widespread in the oceans at this time. However, the absence of such extremely 34S-enriched pyrites from well-preserved, coeval carbonate sections in Oman suggests that such conditions were not globally uniform. Low, geographically varied concentrations of marine sulfate in terminal Proterozoic time are consistent with elevated and geographically varied concentrations of reactive, non-pyritized iron in marine shales recently reported for this interval, suggesting that high dissolved Fe(II)/low O2 conditions persisted in a range of marine facies as late as 543 Ma - tens of millions of years after the origin of animals yet prior to their major diversification in Early Cambrian time.

  5. Assessment of the flotability of chalcopyrite, molybdenite and pyrite using biosolids and their main components as collectors for greening the froth flotation of copper sulphide ores.

    OpenAIRE

    Sobarzo, Francisco; Herrera Urbina, Ronaldo; Higueras Higueras, Pablo Leon; Sáez Navarrete, César; Godoy Faúndez, Alex; Reyes Bozo, Lorenzo; Vásquez Bestagno, Jorge

    2014-01-01

    Biosolids and representative compounds of their main components ? humic acids, sugars, and proteins ? have been tested as possible environment-friendly collectors and frothers for the flotation of copper sulphide ores. The floatability of chalcopyrite and molybdenite ? both valuable sulphide minerals present in these ores ? as well as non-valuable pyrite was assessed through Hallimond tube flotation tests. Humic acids exhibit similar collector ability for chalcopyrite and molybdenite as that ...

  6. Phase stabilities of pyrite-related MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Bachhuber, Frederik [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Krach, Alexander; Furtner, Andrea [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Söhnel, Tilo [School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Auckland (New Zealand); Peter, Philipp; Rothballer, Jan [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Weihrich, Richard, E-mail: richard.weihrich@chemie.uni-r.de [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany)

    2015-03-15

    Pyrite-type and related systems appear for a wide range of binary and ternary combinations of transition metals and main group elements that form Zintl type dumbbell anion units. Those representatives with 20 valence electrons exhibit an extraordinary structural flexibility and interesting properties as low-gap semiconductors or thermoelectric and electrode materials. This work is devoted to the systematic exploration of novel compounds within the class of MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te) by means of density functional calculations. Their preferred structures are predicted from an extended scheme of colored pyrites and marcasites. To determine their stabilities, competing binary MT{sub 2} and MCh{sub 2} boundary phases are taken into account as well as ternary M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} systems. Recently established stability diagrams are presented to account for MTCh ordering phenomena with a focus on a not-yet-reported ordering variant of the NiAs{sub 2} type. Due to the good agreement with experimental data available for several PtTCh systems, the predictions for the residual systems are considered sufficiently accurate. - Graphical abstract: Compositional and structural stability of MTCh compounds is investigated from first principle calculations. A conceptional approach is presented to study and predict novel stable and metastable compounds and structures of low gap semiconductors with TCh dumbbell units that are isoelectronic and structurally related to pyrite (FeS{sub 2}). - Highlights: • Study of compositional stability of MTCh vs. M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} compounds. • Study of structural stability of known and novel MTCh compounds. • Prediction of novel stable and metastable structures and compounds isoelectronic to pyrite, FeS{sub 2}.

  7. Pyrite framboid size distribution as a record for relative variations in sedimentation rate: An example on the Toarcian Oceanic Anoxic Event in Southiberian Palaeomargin

    Science.gov (United States)

    Gallego-Torres, David; Reolid, Matías; Nieto-Moreno, Vanesa; Martínez-Casado, Francisco Javier

    2015-12-01

    The Early Toarcian Oceanic Anoxic Event (T-OAE) represents one of the major alterations of the carbon cycle of the Mesozoic period. Despite being globally recognized, and particularly represented within the Tethys realm, its expression in the sedimentary record is highly variable depending on the studied section, which suggests local environmental factors exert a major control on the resulting lithological appearance of the event. We investigated the Fuente Vidriera section, in the eastern External Subbetic of the Betic Cordillera (Spain), where the Lower Jurassic is represented by alternate layers of marls and marly limestones, and the T-OAE is identified by a major δ13C excursion, micropalaeontological, ichnofacies and geochemical evidences. For this study, we analyzed pyrite framboid size distribution of the sedimentary sequence in Fuente Vidriera. The outcome, according to previous studies on pyrite framboid distribution, is contradictory when compared to all other evidences, suggesting oxygen depletion during the T-OAE. The results have been reinterpreted in the light of Crystal Size Distribution Theory and we conclude that not only growth time but also geochemical environment controls pyrite formation. Since growth time is directly related to burial rates, this approach allows us to reconstruct relative variations of sedimentation rates during the Early Jurassic in this location. Based on the obtained results, we provide new evidences for wide-spread transgression during the Early Toarcian in the South Iberian palaeomargin, which induced low sedimentation rate and lower energetic conditions, as well as favored oxygen impoverished bottom waters.

  8. Attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum cultured under varying conditions to pyrite, chalcopyrite, low-grade ore and quartz in a packed column reactor.

    Science.gov (United States)

    Africa, Cindy-Jade; van Hille, Robert P; Harrison, Susan T L

    2013-02-01

    The attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum spp. grown on ferrous medium or adapted to a pyrite mineral concentrate to four mineral substrata, namely, chalcopyrite and pyrite concentrates, a low-grade chalcopyrite ore (0.5 wt%) and quartzite, was investigated. The quartzite represented a typical gangue mineral and served as a control. The attachment studies were carried out in a novel particle-coated column reactor. The saturated reactor containing glass beads, which were coated with fine mineral concentrates, provided a quantifiable surface area of mineral concentrate and maintained good fluid flow. A. ferrooxidans and Leptospirillum spp. had similar attachment characteristics. Enhanced attachment efficiency occurred with bacteria grown on sulphide minerals relative to those grown on ferrous sulphate in an ore-free environment. Selective attachment to sulphide minerals relative to gangue materials occurred, with mineral adapted cultures attaching to the minerals more efficiently than ferrous grown cultures. Mineral-adapted cultures showed highest levels of attachment to pyrite (74% and 79% attachment for A. ferrooxidans and L. ferriphilum, respectively). This was followed by attachment of mineral-adapted cultures to chalcopyrite (63% and 58% for A. ferrooxidans and L. ferriphilum, respectively). A. ferrooxidans and L. ferriphilum exhibited lower levels of attachment to low-grade ore and quartz relative to the sulphide minerals.

  9. Comparative investigation on integrated vertical-flow biofilters applying sulfur-based and pyrite-based autotrophic denitrification for domestic wastewater treatment.

    Science.gov (United States)

    Kong, Zhe; Li, Lu; Feng, Chuanping; Dong, Shanshan; Chen, Nan

    2016-07-01

    Two parallel biofilters applying sulfur/pyrite-based autotrophic denitrification were investigated for removing COD, TP and TN by a coordinated process. Results demonstrated good performance by removing 86.32% vs 87.14% COD and 92.56% vs 89.65% NH4(+)-N. Biofilter with sulfur (BS) was superior on nitrate (89.74% vs 80.72%) and TN removal (83.18% vs 70.42%) while biofilter with pyrite (BP) was better on TP removal (82.58% vs 77.40%) and maintaining sulfate (27.56mgL(-1) vs 41.55mgL(-1)) and pH (7.13 vs 6.31). Water-permeable adsorbents lowered clogging risk and buffered loading. Clone library revealed reasons of diversities, pH variation and sulfate accumulation of both biofilters. Sulfur was efficient on denitrification but whose byproducts were troublesome, pyrite produced less byproduct but which was sensitive to organics. This research was the first attempt to systematically compare two promising alternatives and their merits/demerits for rural wastewater on-site treatment.

  10. The influence of pH and reaction time on the formation of FeSe{sub 2} upon selenite reduction by nano-sized pyrite-greigite

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Mingliang [Sun Yat-sen Univ., Zhuhai (China). Sino-French Institute of Nuclear Engineering and Technology; Bardelli, Fabrizio; Ma, Bin; Charlet, Laurent [Grenoble Univ. (France). Environmental Geochemistry Group; Chen, Fanrong; Yang, Yongqiang [Chinese Academy of Sciences, Guangzhou (China). Key Laboratory of Mineralogy and Metallogeny; Chinese Academy of Sciences, Guangzhou (China). Guangdong Provincial Key Laboratory of Mineral Physics and Materials

    2016-11-01

    The influence of pH and reaction time on the formation of FeSe{sub 2} by reductive precipitation of Se(IV) with nano-sized pyrite-greigite was investigated. Reductive precipitation is an effective method of attenuating the mobility of {sup 79}Se, which is foreseen to be a dangerous radioisotope for the geological disposal of high-level radioactive waste (HLW). The results indicated that Se(0)was formed at pH <4.05, whereas, at pH > 6.07, considerable amount of FeSe{sub 2} was formed along with Se(0). These observations are in agreement with the thermodynamic predictions reported in this work. Furthermore, the formation of FeSe{sub 2} was found to continue by increasing the reaction time, indicating that the Se(0) formed in the early reaction stage is gradually transformed to FeSe{sub 2} upon the depletion of aqueous Se(IV). Since FeSe{sub 2} has a stronger reactivity than pyrite, it was proposed that greigite, rather than pyrite, was responsible for the formation of FeSe{sub 2}. The findings in this study are of interest for key geochemical processes governing the mobility of toxic {sup 79}Se in the environment in presence of iron sulfides.

  11. 硫铁矿烧渣直接还原回收有价金属%Recovering Valuable Metals from Pyrite Cinder by Direct Reduction

    Institute of Scientific and Technical Information of China (English)

    范增

    2015-01-01

    研究了采用回转短窑对硫铁矿烧渣进行焙烧以回收有价金属的方法 ,考察了不同的工艺条件对硫铁矿烧渣焙烧的影响.研究结果表明 :在还原温度在1 250℃下、还原时间为60 min下 ,硫铁矿烧渣得到充分的还原.金、银、铜、铅、锌的挥发率中试分别达到93 .26% , 82 .20% ,82 .55% ,88 .53% 和83 .48% ,此时球团的硬度可以达到2 100 N.%The roasting method was used to recover valuable metals from pyrites cinder in rotary kiln , and the influences of different process conditions on roasting pyrite cinder were examined . The results show that the pyrite cinder can be fully reduced under the conditions of reaction temperature at 400℃ and reac-tion time for 60 minutes . The volatilizing rates of gold , silver , copper , lead and zinc in pilot scale experi-ment can reach 93 .26% ,82 .20% ,82 .55% ,88 .53% and 83 .48% , respectively . Hardness of the pellets can reach 2100 N at this time .

  12. Overview on Microbial Desulfurization for Pyrite Cinder%硫铁矿烧渣的微生物脱硫概况

    Institute of Scientific and Technical Information of China (English)

    周文博; 邹平; 孙珮石

    2013-01-01

    对硫酸渣微生物氧化脱硫研究进行了综述,主要包括硫酸渣的特性、脱硫工艺、脱硫微生物种类、细菌氧化机理、微生物脱硫影响因素、硫酸渣生物氧化脱硫现状和存在问题等,展望了该技术未来的研究方向及应用前景.%The research on microbial oxidation desulfurization for pyrite cinder is summarized in this paper, which mainly includes the characteristics of pyrite cinder, desulfuration process, desulfurization microbial species, bacterial oxidation mechanism, the influence factors of microbial desulfurization, the present situation and the existing problems of pyrite cinder's biological oxidation desulfurization, and so on, the future direction of the research and the application prospect are also forecasted in this paper.

  13. Overall hydrochemical characterization of the Iberian Pyrite Belt. Main acid mine drainage-generating sources (Huelva, SW Spain)

    Science.gov (United States)

    Grande, J. A.; de la Torre, M. L.; Cerón, J. C.; Beltrán, R.; Gómez, T.

    2010-09-01

    SummaryAMD is an anthropogenic process caused by sulfide mineralization and the increase in the contact surface due to mining activity and grain-size reduction. In Spain, the contamination comes from the metal sulfide mines in the Iberian Pyrite Belt (IPB). Spreading over an area 230 km long and approximately 50 km wide, it is one of the largest metallogenic regions in the world, with massive sulfide reserves of about 1700 Mt. In the present study we will characterize AMD contamination processes in the IPB, especially by As, by identifying the sources responsible for these processes (active mines and effluents from mines and slag heaps) in the basins of the Tinto and Odiel rivers. It is also the aim of this study to discover the mineral associations of the deposits. The study of the AMD process generating source is complemented with hydrochemical characterization of the effluents produced, which will be carried out by means of sample-taking and subsequent chemical analysis and statistical treatment (cluster analysis). Characteristics in common with samples taken in other AMD-affected watercourses are observed in the seven zones defined in the study area. With respect to the samples studied, obvious differences can also be found. These differences are inherent to the mineral associations, watershed and distance to the generating source and, ultimately, to the affected area, and the type, intensity and duration of the mine treatment process developed in the acid-producing area.

  14. New markers to identify the provenance of lapis lazuli: trace elements in pyrite by means of micro-PIXE

    Energy Technology Data Exchange (ETDEWEB)

    Re, A. [Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino (Italy); Angelici, D. [Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino (Italy); Universita di Torino, Dipartimento di Fisica, Torino (Italy); Universita di Torino, Dipartimento di Scienze della Terra, Torino (Italy); Lo Giudice, A. [Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Torino, Torino (Italy); Universita di Torino, Dipartimento di Fisica, Torino (Italy); Maupas, E. [Universita di Torino, Dipartimento di Fisica, Torino (Italy); Giuntini, L.; Calusi, S.; Massi, M.; Mando, P.A. [Universita di Firenze, Dipartimento di Fisica, Sesto Fiorentino, Firenze (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Firenze, Sesto Fiorentino, Firenze (Italy); Gelli, N. [Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Firenze, Sesto Fiorentino, Firenze (Italy); Borghi, A. [Universita di Torino, Dipartimento di Scienze della Terra, Torino (Italy); Gallo, L.M. [Museo Regionale di Scienze Naturali, Torino (Italy); Pratesi, G. [Universita di Firenze, Dipartimento di Scienze della Terra, Firenze (Italy); Museo di Storia Naturale, Firenze (Italy)

    2013-04-15

    Lapis lazuli has been used for glyptics and carving since the fifth millennium BC to produce jewels, amulets, seals, inlays, etc; the identification of the origin of the stone used for carving artworks may be valuable for reconstructing old trade routes. Since ancient lapis lazuli art objects are precious, only non-destructive techniques can be used to identify their provenance, and ion beam analysis (IBA) techniques allow us to characterise this stone in a fully non-invasive way. In addition, by using an ion microprobe, we have been able to focus the analysis on single crystals, as their typical dimensions may range from a few microns to hundreds of microns. Provenance markers, identified in previous IBA studies and already presented elsewhere, were based on the presence/absence of mineral phases, on the presence/quantity of trace elements inside a phase and on characteristic features of the luminescence spectra. In this work, a systematic study on pyrite crystals, a common accessory mineral in lapis lazuli, was carried out, following a multi-technique approach: optical microscopy and SEM-EDX to select crystals for successive trace element micro-PIXE measurements at two Italian facilities, the INFN Laboratori Nazionali di Legnaro and the INFN LABEC laboratory in Firenze. The results of this work allowed us to obtain new markers for lapis lazuli provenance identification. (orig.)

  15. Episodic euxinia in the Changhsingian (late Permian) of South China: Evidence from framboidal pyrite and geochemical data

    Science.gov (United States)

    Wei, Hengye; Algeo, Thomas J.; Yu, Hao; Wang, Jiangguo; Guo, Chuan; Shi, Guo

    2015-04-01

    A multiproxy study of a new Upper Permian-Lower Triassic section (Xiaojiaba) in Sichuan Province, China, documents large changes in marine productivity, redox conditions and detrital input prior to the latest Permian mass extinction. Marine productivity, as proxied by total organic carbon content (TOC), biogenic SiO2, and excess barium, displays a long-term decline through most of the Changhsingian stage (late late Permian), culminating in very low values around the Permian-Triassic boundary. Concurrently, redox proxies including pyrite framboid, δ34Spy, Moauth and Uauth, and Corg/P document a shift from suboxic to dysoxic/oxic conditions that was interrupted by several episodes of benthic euxinia, and detrital siliciclastic proxies (Al, Hf, Nb, and REEs) suggest an increased flux of weathered material from land areas. The long-term changes in productivity, redox conditions, and terrigenous detrital fluxes were probably caused by a regional sea-level fall across the South China Craton. On the other hand, the brief euxinic episodes occurring during the late Permian had oceanographic causes, probably related to the transient upward expansion of the chemocline at the top of the oceanic oxygen-minimum zone. These euxinic episodes may have been harbingers of the more widespread anoxia that developed concurrently with the latest Permian mass extinction and that may have played a major role in triggering the largest biotic crisis of the Phanerozoic.

  16. New markers to identify the provenance of lapis lazuli: trace elements in pyrite by means of micro-PIXE

    Science.gov (United States)

    Re, A.; Angelici, D.; Lo Giudice, A.; Maupas, E.; Giuntini, L.; Calusi, S.; Gelli, N.; Massi, M.; Borghi, A.; Gallo, L. M.; Pratesi, G.; Mandò, P. A.

    2013-04-01

    Lapis lazuli has been used for glyptics and carving since the fifth millennium BC to produce jewels, amulets, seals, inlays, etc; the identification of the origin of the stone used for carving artworks may be valuable for reconstructing old trade routes. Since ancient lapis lazuli art objects are precious, only non-destructive techniques can be used to identify their provenance, and ion beam analysis (IBA) techniques allow us to characterise this stone in a fully non-invasive way. In addition, by using an ion microprobe, we have been able to focus the analysis on single crystals, as their typical dimensions may range from a few microns to hundreds of microns. Provenance markers, identified in previous IBA studies and already presented elsewhere, were based on the presence/absence of mineral phases, on the presence/quantity of trace elements inside a phase and on characteristic features of the luminescence spectra. In this work, a systematic study on pyrite crystals, a common accessory mineral in lapis lazuli, was carried out, following a multi-technique approach: optical microscopy and SEM-EDX to select crystals for successive trace element micro-PIXE measurements at two Italian facilities, the INFN Laboratori Nazionali di Legnaro and the INFN LABEC laboratory in Firenze. The results of this work allowed us to obtain new markers for lapis lazuli provenance identification.

  17. Pyrite multiple-sulfur isotope evidence for rapid expansion and contraction of the early Paleoproterozoic seawater sulfate reservoir

    Science.gov (United States)

    Scott, Clint; Wing, Boswell A.; Bekker, Andrey; Planavsky, Noah J.; Medvedev, Pavel; Bates, Steven M.; Yun, Misuk; Lyons, Timothy W.

    2014-03-01

    Earth's oxygenation is often described in terms of two unidirectional steps at the beginning and end of the Proterozoic Eon, separated by a long-lived intermediate redox state. Recent work defines a more complicated path to oxygenation, exemplified by an apparent drop in oxidation state following the early Paleoproterozoic Lomagundi carbon isotope excursion. The timing of this proposed drop in oxidation state is not well constrained, and it is not clear how it relates to redox conditions during the remainder of the Proterozoic. Here we present a study of pyrite multiple-sulfur isotopes, supported by Fe speciation and organic carbon isotopes, from early Paleoproterozoic black shales. We find evidence for the rapid expansion of the seawater sulfate reservoir during the Great Oxidation Event at ca. 2.3 Ga followed by a subsequent contraction in the size of the seawater sulfate reservoir at ca. 2.05 Ga. This scenario is consistent with the emerging view of a rise and fall in surface oxidation state during the early Paleoproterozoic. Comparison of our new data to other records of the seawater sulfate reservoir suggests that the elevated sulfate concentrations that characterize the early Paleoproterozoic did not return until the late Neoproterozoic.

  18. Recovery of Iron from Pyrite Cinder Containing Non-ferrous Metals Using High-Temperature Chloridizing-Reduction-Magnetic Separation

    Science.gov (United States)

    Chen, Dong; Guo, Hongwei; Xu, Jifang; Lv, Yanan; Xu, Zemin; Huo, Haijiang

    2017-01-01

    This study presents a new technique that uses high-temperature chloridizing -reduction-magnetic separation to recover iron from pyrite cinder containing non-ferrous metals. The effects of the reduction temperature, reduction time, and chlorinating agent dosage were investigated. The optimized process parameters were proposed as the following: CaCl2 dosage of 2 pct, chloridizing at 1398 K (1125 °C) for 10 minutes, reducing at 1323 K (1050 °C) for 80 minutes, grinding to a particle size of 78.8 pct less than 45 μm, and magnetic field intensity of 73 mT. Under the optimized conditions, the Cu, Pb, and Zn removal rates were 45.2, 99.2, and 89.1 pct, respectively. The iron content of the magnetic concentrate was 90.6 pct, and the iron recovery rate was 94.8 pct. Furthermore, the reduction behavior and separation mechanism were determined based on microstructure and phase change analyses using X-ray powder diffraction, scanning electron microscope, and optical microscopy.

  19. The effect of pulse venting on anaerobic oxidation of methane and pyrite formation in the cold seep environment, offshore SW Taiwan

    Science.gov (United States)

    Cheng, Wan-Yen; Lin, Saulwood; Tseng, Yi-Ting; Chen, NeiChen; Hsieh, I.-Chih

    2016-04-01

    AOM (Anaerobic oxidation of methane) is a key process in seep environment. Sulfate was consumed during oxidation of methane or organic matter with pyrite as a major end product in the anoxic marine environment. Typical changes observed in the pore water include an increase of methane with depth beneath the SMTZ (sulfate methane transition zone), as a result of diffusion and/or advection, and appearances of a dissolved sulfide maximum underneath a dissolved iron peak with depth. A number of other related biogeochemical processes and end products may register their respective changes in sediments as a result of AOM and related reactions. However, flux, time and duration of gas migration may have changed by either long term processes, e.g., tectonic activities and/or climatic induced sea level changes, or short term, e.g., tidal variations. There is relatively little study addressing termination of gas migrations and subsequent changes in the seep environments. In this study, we will present our study on a seep environment where pulses of gas migration may have occurred with a number of chemical anomalies in sediments. We have collected pore water and sediments for their chemical compositions of sulfate, dissolved sulfide, chloride, organic carbon, carbonate carbon and pyrite as well as echo sounding for flares, and towcam for sea surface topography and benthic community. Our results show that methane gas may have migrated in sediments in carrying out AOM reaction and pyrite formation, however, gas migration may have been relatively short and in pulses. Pulses of gas migration resulted in little or even no sulfate reduction in pore water, but with appearance of dissolved sulfide as well as very high concentrations of pyrite in sediments. Flares were observed but not constantly at the site where chemical anomalies were observed. Pulses of gas migration may come from solid gas hydrate formation and dissociation as evidence from pore water chloride enrichment and

  20. Iron isotope compositions and origins of pyrites from the Turee Creek Group, Western Australia: the contribution of high-resolution femtosecond Laser Ablation -MC-ICP-MS

    Science.gov (United States)

    d'Abzac, F.; Beard, B. L.; Williford, K. H.; Valley, J. W.; Van Kranendonk, M. J.; Johnson, C.

    2013-12-01

    The Paleoproterozoic Great Oxidation Event (GOE) records a transition from an anoxic environment to a O2-bearing atmosphere, but its timing and duration remain unclear. High-spatial-resolution S isotope analyses by SIMS have shown that pyrite grains in the ~2.4Gy diamictites of the Meteorite Bore Member (MBM; Turee Creek Group, Western Australia), deposited during the GOE, contain evidence for a complex depositional and paragenetic history, including microbial sulfate reduction under low atmospheric O2 yet high seawater sulfate concentrations. The pyrites show various morphologies: euhedral, subhedral, anhedral, rounded, and zoned, where low- δ34S rounded cores may have high-δ34S euhedral/subhedral overgrowths [1]. New in-situ Fe isotope data by femtosecond laser ablation (fs-LA) analysis using Multi Collector ICP-MS on 118 pyrite grains within five rock samples previously analyzed for S isotopes documents δ56Fe values between -2.3‰ and +2.3‰. Transitional cherts at the base of the MBM record the highest δ56Fe values, >0.7‰. Within the upper mudstones/sandstones deposits, anhedral, rounded grains and zoned pyrite cores have a wide range of δ56Fe from -2.3‰ to +1.1‰ whereas euhedral grains and grains overgrowths have mainly positive δ56Fe values, up to +1.34‰, spread over narrower ranges in each sample (100°C [5, 6], in agreement with [1]. The δ34S gradient of highly negative to positive values from zoned pyrites cores to rims is well correlated with our observations of low-δ56Fe cores to positive δ56Fe rims, within the same set of grains, which supports the paragenesis described in [1]. This study demonstrates the importance of high resolution in-situ isotopic analysis for samples of complex histories and multiple isotopic components, and in the case of the GOE transition, document that a large variety of Fe pathways were active during the transition. 1. Williford, K.H., et al., Geochimica et Cosmochimica Acta, 2011. 75(19): p. 5686-5705. 2

  1. Oxygen-dependent niche formation of a pyrite-dependent acidophilic consortium built by archaea and bacteria.

    Science.gov (United States)

    Ziegler, Sibylle; Dolch, Kerstin; Geiger, Katharina; Krause, Susanne; Asskamp, Maximilian; Eusterhues, Karin; Kriews, Michael; Wilhelms-Dick, Dorothee; Goettlicher, Joerg; Majzlan, Juraj; Gescher, Johannes

    2013-09-01

    Biofilms can provide a number of different ecological niches for microorganisms. Here, a multispecies biofilm was studied in which pyrite-oxidizing microbes are the primary producers. Its stability allowed not only detailed fluorescence in situ hybridization (FISH)-based characterization of the microbial population in different areas of the biofilm but also to integrate these results with oxygen and pH microsensor measurements conducted before. The O2 concentration declined rapidly from the outside to the inside of the biofilm. Hence, part of the population lives under microoxic or anoxic conditions. Leptospirillum ferrooxidans strains dominate the microbial population but are only located in the oxic periphery of the snottite structure. Interestingly, archaea were identified only in the anoxic parts of the biofilm. The archaeal community consists mainly of so far uncultured Thermoplasmatales as well as novel ARMAN (Archaeal Richmond Mine Acidophilic Nanoorganism) species. Inductively coupled plasma analysis and X-ray absorption near edge structure spectra provide further insight in the biofilm characteristics but revealed no other major factors than oxygen affecting the distribution of bacteria and archaea. In addition to catalyzed reporter deposition FISH and oxygen microsensor measurements, microautoradiographic FISH was used to identify areas in which active CO2 fixation takes place. Leptospirilla as well as acidithiobacilli were identified as primary producers. Fixation of gaseous CO2 seems to proceed only in the outer rim of the snottite. Archaea inhabiting the snottite core do not seem to contribute to the primary production. This work gives insight in the ecological niches of acidophilic microorganisms and their role in a consortium. The data provided the basis for the enrichment of uncultured archaea.

  2. Origins of Carbonaceous Matter, Hematite, and Pyrite in the 3.46Ga Marble Bar Chert/Jasper/Basalt Formation, Pilbara, Western Australia

    Science.gov (United States)

    Ohmoto, H.; Bevacqua, D. C.; Watanabe, Y.; Otake, T.

    2004-12-01

    The 3.46 Ga Marble Bar Chert/Jasper unit in the Pilbara district, W.A. was probably deposited in a deep (>500 m) ocean during the accumulation of a thick (>5 km) submarine basalt. Debate focuses on whether organic matter in pre-2.0 Ga cherts is a remnant of marine organisms or the product of abiotic synthesis in hydrothermal systems, whether the hematite crystals in jaspers were primary or products of modern oxidation of siderite and pyrite, and whether the pyrite crystals formed by sulfate-reducing bacteria, hydrothermal fluids, or atmospheric sulfur. At the drilling site, the Marble bar Chert/Jasper is over turned diping about 80 degrees. A continuous 264 m- long core, drilled at 50 degrees, was recovered. The major chert/jasper unit, comprising alternating beds (0.1 - 5 cm thick) of white/green/gray/black/red chert, is 105 m thick. The abundance of red jasper beds increases down hole, indicating that the hematite crystals were not produced by subaerial oxidation of ferrous minerals. Petrological, mineralogical, and geochemical investigations of the core samples, especially using an X-ray chemical microscope, have revealed that the dominant Fe-bearing minerals are siderite, magnetite, and hematite, in the green, gray-black, and red cherts, respectively. These Fe-bearing minerals and disseminated pyrite crystals (ubiquitous in all cherts) are typically very fine grained (less than 10 microns). The basalts (pillows and tuffs), which occur below, above, and interbedded with the chert/jasper unit, are in places heavily hematitized with various characteristics of submarine hydrothermal alteration, such as chloritization, silicification, pyritization, large variations in the contents of Fe, Mg, Ba, and depletions in Ca, Sr, and Na. Veinles containing quartz and pyrite are abundant in the chert/jaster beds and also in the heavily hematitized basalts. These data suggest the hematite, magnetie, siderite, pyrite and silica in the chert/jasper unit, basalt tuffs, and pillow

  3. Iron extraction from pyrite cinder by mixed acid%双酸法提取硫铁矿烧渣中铁

    Institute of Scientific and Technical Information of China (English)

    刘培; 江健; 刘宗宽; 张磊; 贺延龄

    2013-01-01

    Extraction of iron from pyrite cinder by mixed acid of sulfuric acid and hydrochloric acid,and main factors influencing iron leaching rate were investigated.In order to analyze feasibility of extraction of iron from pyrite cinder,the main elements were determined by using X-ray fluorescence spectrum analyzer (XRF).The crystal type of iron oxide in the pyrite cinder was also analyzed by X-ray diffraction (XRD) to understand the presence forms of iron in pyrite cinder.First,10 g dried pyrite cinder were added to a 250 ml three-necked flask.Then,sulfuric acid and hydrochloric acid of specified concentration and quantity were gradually added into the flask under proper stirring,and were kept at a specific temperature for several hours.After filtration,the solution was diluted to 250 ml with distilled water.The diluted solution was used for determination of iron content in leacheate using the stannous chloride-mercury chloridepotassium dichromate method.At last extraction conditions were optimized.The results showed that the significances of each factor on iron extraction were as follows:concentration of sulfuric acid>hydrochloric acid amount>reaction time>sulfuric acid over-dose coefficient.Iron extraction rate increased with higher reaction temperature and increasing amount of hydrochloric acid.However,there existed an optimum combination of sulfuric acid concentration,reaction time and sulfuric acid over-dose coefficient.The optimal conditions were reaction temperature 118-125℃,reaction time 3 h,sulfuric acid concentration 50%-60%,and hydrochloric acid 0.25 ml · (g pyrite cinder)-1,sulfuric acid over-dose coefficient 1.2.Under these conditions,the extraction yield of iron was 93.1%,much higher than that by a single acid.So,the process can improve utilization of iron resource.%应用硫酸-盐酸混酸浸出回收硫铁矿烧渣中的铁,探讨了主要因素对铁浸取率的影响,确定了最佳浸取条件.结果表明,各因素对铁浸取率影

  4. Effects of selective handling of pyritic, acid-forming materials on the chemistry of pore gas and ground water at a reclaimed surface coal mine in Clarion County, PA, USA

    Science.gov (United States)

    Cravotta, Charles A.; Dugas, Diana L.; Brady, Keith; Kovalchuck, Thomas E.

    1994-01-01

    A change from dragline to “selective handling” mining methods at a reclaimed surface coal mine in western Pennsylvania did not significantly affect concentrations of metals in ground water because oxidation of pyrite and dissolution of siderite were not abated. Throughout the mine, placement of pyritic material near the land surface facilitated the oxidation of pyrite, causing the consumption of oxygen (O2) and release of acid, iron, and sulfate ions. Locally in the unsaturated zone, water sampled within or near pyritic zones was acidic, with concentrations of sulfate exceeding 3,000 milligrams per liter (mg/L). However, acidic conditions generally did not persist below the water table because of neutralization by carbonate minerals. Dissolution of calcite, dolomite, and siderite in unsaturated and saturated zones produced elevated concentrations of carbon dioxide (CO2), alkalinity, calcium, magnesium, iron, and manganese. Alkalinity concentrations of 600 to 800 mg/L as CaCO3 were common in water samples from the unsaturated zone in spoil, and alkalinities of 100 to 400 mg/L as CaCO3 were common in ground-water samples from the underlying saturated zone in spoil and bedrock. Saturation indices indicated that siderite could dissolve in water throughout the spoil, but that calcite dissolution or precipitation could occur locally. Calcite dissolution could be promoted as a result of pyrite oxidation, gypsum precipitation, and calcium ion exchange for sodium. Calcite precipitation could be promoted by evapotranspiration and siderite dissolution, and corresponding increases in concentrations of alkalinity and other solutes. Partial pressures of O2 (Po2) and CO2 (Pco2) in spoil pore gas indicated that oxidation of pyrite and precipitation of ferric hydroxide, coupled with dissolution of calcite, dolomite, and siderite were the primary reactions affecting water quality. Highest vertical gradients in Po2, particularly in the near-surface zone (0-1 m), did not correlate

  5. The Gruta de las Maravillas (Aracena, South-West Iberia): Setting and origin of a cave in marbles from dissolution of pyrite

    Science.gov (United States)

    Martínez-Moreno, F. J.; Pedrera, A.; Galindo-Zaldívar, J.; López-Chicano, M.; Azor, A.; Martín-Rosales, W.; Ruano, P.; Calaforra, J. M.; Hódar-Pérez, A.

    2016-01-01

    The Gruta de las Maravillas cave is located at the WNW side of the Cerro del Castillo hill in Aracena (Huelva, SW Spain). The cavity is hosted within marbles included in a strip of high-grade metamorphic rocks belonging to the so-called Aracena Massif in the southernmost Ossa-Morena Zone. The hill is made up of granodiorites, marbles, quartzites, and gneisses, with the foliation trending N110°E and dipping roughly 60-80° towards NE. The marbles appear highly deformed in ductile conditions, with isoclinal folds of different sizes, boudins, porphyroblasts with sigmoidal morphology, and left-lateral S-C shear fabrics. Close to the granodiorite contact, the marbles include a thin band of disseminated and massive pyrite, partially transformed to Fe-oxides. Analysis of the brittle deformation and the associated paleostresses indicates a NE-SW oriented maximum compression, probably related to the latest Variscan collisional tectonics (300 Ma; Late Carboniferous). The Gruta de las Maravillas is divided into three main levels (located at ~ 650, ~ 665 and ~ 685 m a.s.l.), the dissolution having progressed from top to bottom in different stages of stability of the water table. The initial dissolution phases were probably favoured by the presence of pyrite in the host rock, which, in turn, would have caused acidification of the circulating water. Favouring this hypothesis, a thin layer of Fe-oxides, locally including gypsum, covers some parts of the cave walls. The morphology and structure of the cavity result from interaction between the general NNE dipping foliation with sub-perpendicular joints, the pyrite-bearing band in the host marbles, and the descending water table.

  6. The energetics of the reductive citric acid cycle in the pyrite-pulled surface metabolism in the early stage of evolution.

    Science.gov (United States)

    Kalapos, Miklós Péter

    2007-09-21

    The chemoautotrophic theory concerning the origin of life postulates that a central role is played in the prebiotic chemical machinery by a reductive citric acid cycle operating without enzymes. The crucial point in this scenario is the formation of pyrite from hydrogen sulfide and ferrous sulfide, a reaction suggested to be linked to endergonic reactions, making them exergonic. This mechanism is believed to provide the driving force for the cycle to operate as a carbon dioxide fixation network. The present paper criticizes the thermodynamic calculations and their presentation in the original version of the archaic reductive citric acid cycle [Wächtershäuser, 1990. Evolution of the first metabolic cycles. Proc. Natl Acad. Sci. USA 87, 200-204.]. The most significant differences between the Wächtershäuser hypothesis and the present proposal: Wächtershäuser did not consider individual reactions in his calculations. A particularly questionable feature is the involvement of seven molecules of pyrite which does not emerge as a direct consequence of the chemical reactions presented in the archaic reductive citric acid cycle. The involvement of a considerable number of sulfur-containing organic intermediates as building blocks is also disputed. In the new scheme of the cycle proposed here, less free energy is liberated than hypothesized by Wächtershäuser, but it has the advantages that the free energy changes for the individual reactions can be calculated, the number of pyrite molecules involved in the cycle is reduced, and fewer sulfur-containing intermediates are required for the cycle to operate. In combination with a plausible route for the anaplerotic reactions [Kalapos, 1997a. Possible evolutionary role of methylglyoxalase pathway: anaplerotic route for reductive citric acid cycle of surface metabolists. J. Theor. Biol. 188, 201-206.], this new presentation of the cycle assigns a special meaning to hydrogen sulfide formation in the early stage of biochemical

  7. Gold deposition on pyrite and the common sulfide minerals: An STM/STS and SR-XPS study of surface reactions and Au nanoparticles

    Science.gov (United States)

    Mikhlin, Yuri L.; Romanchenko, Alexander S.

    2007-12-01

    Gold species spontaneously deposited on pyrite and chalcopyrite, pyrrhotite, galena, sphalerite from HAuCl 4 solutions at room temperature, as well as the state of the reacted mineral surfaces have been characterized using synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS), scanning tunneling microscopy and tunneling spectroscopy (STM/STS). The deposition of silver from 10 -4 M AgNO 3 has been examined for comparison. Gold precipitates as metallic nanoparticles (NPs) from about 3 nm to 30 nm in diameter, which tends to aggregate forming larger particles, especially on pyrite. The Au 4f binding energies increase up to 1 eV with decreasing size of individual Au 0 NPs, probably due to the temporal charging in the final state. Concurrently, a positive correlation between the tunneling current and the particle size was found in STS. Both these size effects were observed for unusually large, up to 20 nm Au particles. In contrast, silver deposited on the minerals as nanoparticles of semiconducting sulfide showed no shifts of photoelectron lines and different tunneling spectra. The quantity of gold deposited on pyrite and other minerals increased with time; it was lower for fracture surfaces and it grew if minerals were moderately pre-oxidized, while the preliminary leaching in Fe(III)-bearing media inhibited the following Au deposition. After the contact of polished minerals with 10 -4 M AuCl4- solution (pH 1.5) for 10 min, the gold uptake changed in the order CuFeS 2 > ZnS > PbS > FeAsS > FeS 2 > Fe 7S 8. It was noticed that the open circuit (mixed) potentials of the minerals varied in approximately the same order, excepting chalcopyrite. We concluded that the potentials of minerals were largely determined by Fe(II)/Fe(III) couple, whereas the reduction of gold complexes had a minor effect. As a result, the deposition of gold, although it proceeded via the electrochemical mechanism, increased with decreasing potential. This suggests, in particular, that the

  8. Optical Properties of Pyrite-structure TiO2%Pyri te-结构Ti O2的光学性质

    Institute of Scientific and Technical Information of China (English)

    刘强; 肖贵乾; 杨秋萍

    2014-01-01

    利用第一性原理计算了立方相TiO2为黄铁矿结构时的光学性质,利用Kramers-Kronig色散关系分别对金红石矿TiO2和黄铁矿结构TiO2的复介电常数、吸收光谱等参数进行了计算,并将两者进行了比较。金红石矿TiO2的静介电常数的计算结果与实验值一致,而黄铁矿结构TiO2的静介电常数为6.02。吸收谱的对比分析结果表明:与金红石矿TiO2相比,黄铁矿结构TiO2在30 nm处增加了新的吸收峰,并且吸收谱范围扩大到了可见光区。%A density functional theory is used in calculating the optical properties of pyrite type TiO2 . In addition,the author calculated the complex dielectric constant and absorption spectrum of rutile type TiO2 and pyrite type TiO2 through Kramers-Kronig dispersion relation and compared the results of two kinds of structure.It is suggested that the static dielectric constant of rutile type TiO2 calculated is in accord with corresponding experimental data,meanwhile,the static dielectric constant of pyrite type TiO2 is 6.02.The comparison of absorption spectrum in these two structures indicated that a new absorption peak at 30 nm can be observed in absorption spectrum of pyrite type TiO2 and the absorp-tion range extended to the visible region compared with rutile type TiO2 .

  9. FeS2微粉的水热合成及晶体结构研究%Preparation of Pyrite Powder by Hydrothermal Process

    Institute of Scientific and Technical Information of China (English)

    吴荣; 郑毓峰; 张校刚; 孙言飞; 徐金宝; 姜海涛

    2005-01-01

    利用水热法一步合成了黄铁矿型FeS2(Pyrite)多晶粉体.样品的X射线衍射线和Rietvild结构精修表明,所得样品具有AB2型立方结构,空间群Pa3,晶格常数a=5.4151 A,Wyckoff参量u=0.3868,结合水热生长模式分析了晶体的生长过程.

  10. Oxidation of dibenzothiophene as a model substrate for the removal of organic sulphur from fossil fuels by iron(III ions generated from pyrite by Acidithiobacillus ferrooxidans

    Directory of Open Access Journals (Sweden)

    VLADIMIR P. BESKOSKI

    2007-06-01

    Full Text Available Within this paper a new idea for the removal of organically bonded sulphur from fossil fuels is discussed. Dibenzothiophene (DBT was used as a model compound of organicmolecules containing sulphur. This form of (biodesulphurization was performed by an indirect mechanism in which iron(III ions generated from pyrite by Acidithiobacillus ferrooxidans performed the abiotic oxidation. The obtained reaction products, dibenzothiopene sulfoxide and dibenzothiophene sulfone, are more soluble in water than the basic substrate and the obtained results confirmed the basic hypothesis and give the posibility of continuing the experiments related to application of this (biodesulphurization process.

  11. Using airborne hyperspectral data to characterize the surface pH and mineralogy of pyrite mine tailings

    Science.gov (United States)

    Zabcic, N.; Rivard, B.; Ong, C.; Mueller, A.

    2014-10-01

    Acid mine drainage (AMD) is a key concern of the mining industry due to its impact on the quality of water and soils surrounding mine waste deposits. Acid mine drainage derives from the oxidation of metal sulphides, e.g. pyrite (FeS2), exposed to oxygen and water. The leachate acidity is capable of releasing heavy metals contained in the mining waste rock, which can affect water quality and lead to metal enrichment in sediments and potentially resulting in ecosystem degradation. Predicting tailings leachate pH is key to the management of sulfide-bearing mine wastes and is an emerging remote sensing application with limited studies having been realized. Such a capability would supplement traditional methods (i.e. ground surveys) that are challenging to implement due to the extent and large volume of mine waste. This study reports regional scale tailings mineral maps generated from airborne hyperspectral information of the Sotiel-Migollas complex in Spain and pinpoints sources of AMD. The extraction of spectral endmembers from imagery revealed twenty six endmembers for tailings material that represent mostly mineral mixtures. From these, eleven spectral groups were defined, each encompassing minor variations in mineral mixtures. The mineral maps resulting from the use of these endmembers for the detailed investigation of four tailings serve as indicators of the metal, sulphate, and pH levels of the AMD solution at the time of mineral precipitation. Predicted mineralogy was assessed using spectra from samples collected in the field and associated X-ray diffraction measurements. We also discuss the relative merits of the minerals maps of this study and soil leachate pH maps that we previously reported for the same locality using the same airborne data. The pH maps tend to provide predictions consistent with the mineralogy predicted from the mineral maps and the field and laboratory evidence. The pH maps offer information on the pH conditions of the tailings thus giving

  12. Annual sulfate budgets for Dutch lowland peat polders: The soil is a major sulfate source through peat and pyrite oxidation

    Science.gov (United States)

    Vermaat, Jan E.; Harmsen, Joop; Hellmann, Fritz A.; van der Geest, Harm G.; de Klein, Jeroen J. M.; Kosten, Sarian; Smolders, Alfons J. P.; Verhoeven, Jos T. A.; Mes, Ron G.; Ouboter, Maarten

    2016-02-01

    Annual sulfate mass balances have been constructed for four low-lying peat polders in the Netherlands, to resolve the origin of high sulfate concentrations in surface water, which is considered a water quality problem, as indicated amongst others by the absence of sensitive water plant species. Potential limitation of these plants to areas with low sulfate was analyzed with a spatial match-up of two large databases. The peat polders are generally used for dairy farming or nature conservation, and have considerable areas of shallow surface water (mean 16%, range 6-43%). As a consequence of continuous drainage, the peat in these polders mineralizes causing subsidence rates generally ranging between 2 and 10 mm y-1. Together with pyrite oxidation, this peat mineralization the most important internal source of sulfate, providing an estimated 96 kg SO4 ha-1 mm-1 subsidence y-1. External sources are precipitation and water supplied during summer to compensate for water shortage, but these were found to be minor compared to internal release. The most important output flux is discharge of excess surface water during autumn and winter. If only external fluxes in and out of a polder are evaluated, inputs average 37 ± 9 and exports 169 ± 17 kg S ha-1 y-1. During summer, when evapotranspiration exceeds rainfall, sulfate accumulates in the unsaturated zone, to be flushed away and drained off during the wet autumn and winter. In some polders, upward seepage from early Holocene, brackish sediments can be a source of sulfate. Peat polders export sulfate to the regional water system and the sea during winter drainage. The available sulfate probably only plays a minor role in the oxidation of peat: we estimate that this is less than 10% whereas aerobic mineralization is the most important. Most surface waters in these polders have high sulfate concentrations, which generally decline during the growing season when aquatic sediments are a sink. In the sediment, this sulfur is

  13. The world-class Howard's Pass SEDEX Zn-Pb district, Selwyn Basin, Yukon. Part I: trace element compositions of pyrite record input of hydrothermal, diagenetic, and metamorphic fluids to mineralization

    Science.gov (United States)

    Gadd, Michael G.; Layton-Matthews, Daniel; Peter, Jan M.; Paradis, Suzanne J.

    2016-03-01

    The Howard's Pass district, located in Yukon Territory, comprises 14 Zn-Pb sedimentary exhalative (SEDEX) deposits that collectively contain approximately 400.7 Mt grading at 4.5 % Zn and 1.5 % Pb. Sulfide mineralization is hosted in carbonaceous and calcareous to siliceous mudstones. Pyrite is a minor but ubiquitous component. Detailed petrographic analyses reveal that pyrite has a complex and protracted growth history, and multiple generations of pyrite are preserved in single grains. Combined electron probe microanalysis (EPMA) and laser ablation-inductively coupled mass plasma-mass spectrometry (LA-ICP-MS) of paragenetically complex pyrite reveal minor and trace element zonation that mimic textural features. These data provide information on the relative timing and cation content of depositional (i.e., ambient marine), hydrothermal, and metamorphic fluids. These data also identify a suite of nonore elements (Mn, As, Ag, Sb, and Tl) associated with the Zn-Pb mineralizing hydrothermal fluids. Lithogeochemical data and statistical results corroborate the microanalytical findings. These elements are associated with both syngenetic to earliest diagenetic pyrite and later diagenetic pyrite overgrowths, suggesting that SEDEX mineralization was not only the product of hydrothermal precipitates that settled on the seafloor, but also dense metalliferous brine also settled on, and percolated through, unconsolidated carbonaceous muds and precipitated metals. This genetic model is similar to that proposed for the Paleoproterozoic HYC Zn-Pb-Ag SEDEX deposit in northern Australia, and it is likely that common processes and ambient conditions led to the formation and preservation of both of these large SEDEX districts.

  14. Geochemical characterisation of pyrite oxidation and environmental problems related to release and transport of metals from a coal washing low-grade waste dump, Shahrood, northeast Iran.

    Science.gov (United States)

    Doulati Ardejani, Faramarz; Jodieri Shokri, Behshad; Moradzadeh, Ali; Shafaei, Seyed Ziadin; Kakaei, Reza

    2011-12-01

    Pyrite oxidation and release of the oxidation products from a low-grade coal waste dump to stream, groundwater and soil was investigated by geochemical and hydrogeochemical techniques at Alborz Sharghi coal washing plant, Shahrood, northeast Iran. Hydrogeochemical analysis of water samples indicates that the metal concentrations in the stream waters were low. Moreover, the pH of the water showed no considerable change. The analysis of the stream water samples shows that except the physical changes, pyrite oxidation process within the coal washing waste dump has not affected the quality of the stream water. Water type was determined to be calcium sulphate. The results of the analysis of groundwater samples indicate that the pH varies from 7.41 to 7.51. The concentrations of the toxic metals were low. The concentration of SO4 is slightly above than its standard concentration in potable water. It seems that the groundwater less affected by the coal washing operation in the study area. Geochemical analysis of the sediment samples shows that Fe concentration decreases gradually downstream the waste dump with pH rising. SO(4) decreases rapidly downstream direction. Copper, Zn and Co concentrations decrease with distance from the waste dump due to a dilution effect by the mixing of uncontaminated sediments. These elements, in particular, Zn are considerably elevated in sediment sample collected at the nearest distance to the waste dump. There is no doubt that such investigations can help to develop an appropriate water remediation plan.

  15. Definition of redox and pH influence in the AMD mine system using a fuzzy qualitative tool (Iberian Pyrite Belt, SW Spain).

    Science.gov (United States)

    de la Torre, M L; Grande, J A; Valente, T; Perez-Ostalé, E; Santisteban, M; Aroba, J; Ramos, I

    2016-03-01

    Poderosa Mine is an abandoned pyrite mine, located in the Iberian Pyrite Belt which pours its acid mine drainage (AMD) waters into the Odiel river (South-West Spain). This work focuses on establishing possible reasons for interdependence between the potential redox and pH, with the load of metals and sulfates, as well as a set of variables that define the physical chemistry of the water-conductivity, temperature, TDS, and dissolved oxygen-transported by a channel from Poderosa mine affected by acid mine drainage, through the use of techniques of artificial intelligence: fuzzy logic and data mining. The sampling campaign was carried out in May of 2012. There were a total of 16 sites, the first inside the tunnel and the last at the mouth of the river Odiel, with a distance of approximately 10 m between each pair of measuring stations. While the tools of classical statistics, which are widely used in this context, prove useful for defining proximity ratios between variables based on Pearson's correlations, in addition to making it easier to handle large volumes of data and producing easier-to-understand graphs, the use of fuzzy logic tools and data mining results in better definition of the variations produced by external stimuli on the set of variables. This tool is adaptable and can be extrapolated to any system polluted by acid mine drainage using simple, intuitive reasoning.

  16. Heterogeneous sono-Fenton-like process using nanostructured pyrite prepared by Ar glow discharge plasma for treatment of a textile dye.

    Science.gov (United States)

    Khataee, Alireza; Gholami, Peyman; Vahid, Behrouz

    2016-03-01

    The plasma-treated pyrite (PTP) nanostructures were prepared from natural pyrite (NP) utilizing argon plasma due to its sputtering and cleaning effects resulting in more active surface area. The NP and PTP were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) methods. The performance of the PTP was greater than NP for treatment of Reactive Red 84 (RR84) by the heterogeneous sono-Fenton process. The optimum amounts of main operational parameters were obtained as PTP of 4 g/L, initial dye concentration of 10 mg/L, pH of 5, and ultrasonic power of 300 W after 120 min of reaction time. Also, the effects of enhancers, and inorganic salts and t-butanol as hydroxyl radical scavengers on the degradation efficiency were investigated. Gas chromatography-mass spectroscopy analysis (GC-MS) was applied for detection of some degradation intermediates. Environmentally friendly plasma modification of the NP, in situ production of H2O2 and OH radicals, low leached iron concentration and repeated reusability at the milder pH are the significant benefits of the PTP utilization.

  17. Novel microorganism for selective separation of coal from ash and pyrite. Sixth quarterly technical progress report, January 1, 1995--March 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Misra, M.; Smith, R.W.; Raichur, A.M.

    1995-08-01

    The objective of this research project is to study the effectiveness of a novel hydrophobic microorganism, Mycobacterium phlei (M. phlei), for the selective flocculation of coal from pyrite and ash forming minerals. During the reporting period, the flocculation efficiencies of Illinois No. 6 and KY No. 9 coal in the presence of whole and ruptured cells of M. phlei were studied. The effect of synthetic flocculants were also studied for comparison at selected pH values. Results showed that the whole cells of M. phlei can flocculate coal very effectively and rapidly for both the coal samples. However, with ruptured cells of M. phlei the flocculation efficiency is significantly less which can be attributed to the loss of extracellular surfactants during rupturing. Separation of flocs using column flotation was studied for both the coal samples in the acidic pH range. Results indicated that excellent rejection of pyritic sulfur and ash could be obtained with a high combustible recovery. DLVO calculations were performed for all the minerals used in this study to calculate the interaction energies in the presence of whole cells and ruptured cells of M. phlei. A minimum in interaction energy is observed between coal and whole cells of M. phlei at pH 4 which is probably responsible for the higher adhesion and flocculation efficiencies at the pH. However, with ruptured cells the interaction energy increases thus decreasing the amount of M. phlei cells adhering to the surface.

  18. Novel microorganism for selective separation of coal from ash and pyrite; First quarterly technical progress report, September 1, 1993--November 30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Misra, M.; Smith, R.W.; Raichur, A.M.

    1993-12-31

    This report summarizes the progress made during the first quarter of the research project entitled ``A Novel Microorganism for Selective Separation of Coal from Ash and Pyrite,`` DOE Grant No. DE-FG22-93PC93215. The objective of this project is to study the effectiveness of a novel hydrophobic microorganism, Mycobacterium phlei (M. phlei), for the selective flocculation of coal from pyrite and ash-forming minerals. During the reporting period, three different coal samples: Illinois No. 6 coal, Kentucky No. 9 coal and Pittsburgh No. 8 coal, were collected to be used in the investigation. The microorganism, M. phlei, was obtained as freeze-dried cultures and the growth characteristics of the bacteria were studied. Scanning electron microphotographs revealed that M. phlei cells are coccal in shape and are approximately 1 {mu}m in diameter. Electrokinetic measurements showed that the Illinois No. 6 and Pittsburgh No. 8 coal samples had an isoelectric point (IEP) around pH 6 whereas M. phlei had an IEP around pH 1.5. Electrokinetic measurements of the ruptured microorganisms exhibited an increase in IEP. The increase in IEP of the ruputured cells was due to the release of fatty acids and polar groups from the cell membrane.

  19. 硫酸渣煤基直接还原应用基础研究%Fundamental Research on Direct Reduction Process of Coal Based Pyrite Cinder

    Institute of Scientific and Technical Information of China (English)

    闫仲科; 郭亚光

    2013-01-01

    Carbon containing pellets which were made by pyrite cinder and pulverized coal as raw material were introduced to roasting process.The influences of roasting time,roasting temperature,coal amount on metallization rate were investigated.Results showed that roasting temperature of 1 225 ℃,roasting time of 15min and n (C)/n (O) of 1.2 were the optimal control parameters,metallization rate reached 92.5% under these circumstances.These control parameters fulfilled the high reduction efficiency characteristic in rotary hearth furnace,thus,pellets which made up of pyrite cinder are suitable for rotary hearth furnace smelting technology.%以硫酸渣和煤粉为主要原料,对硫酸渣含碳球团进行焙烧,考察焙烧时间、焙烧温度、配碳量对球团金属化率的影响,确定了最佳工艺参数,即焙烧温度为1 225℃、焙烧时间15 min、n(C)/n(O)为1.2时,球团金属化率可达92.5%,此工艺参数满足转底炉高效还原的特点,适用于转底炉工艺.

  20. Research on Enrichment of Iron in Pyrite Cinder%硫酸渣中铁的富集试验研究

    Institute of Scientific and Technical Information of China (English)

    李国旺; 王家伟; 赵平源; 吴霜

    2014-01-01

    研究了从硫酸渣中富集铁,考察了物料细度、物料配比、焙烧温度、焙烧时间对铁品位的影响。结果表明:在物料配比0.20、700℃下焙烧1.5 h ,再用试剂WJ‐2浸出,可将硫酸渣中铁质量分数从49%提高到59.24%。%Enrichmentof iron in pyrite cinder was studied .The effects of pyrite cinder fineness, material proportion, roasting temperature, roasting time on iron grade were examined .The results show that at the conditions of roasting temperature of 700 ℃, the materials proportion of 0 .20, roasting time of 1 .5 h, and leaching using WJ‐2 reagent, the mass fraction of iron in the leaching residue can increase from 49% to 59 .24% .

  1. Photoanodic reactions at natural pyrite(100) studied by photocalorimetry: internal quantum and energy efficiencies and Peltier heats after different surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Schaaf, N.-S.; Dohrmann, J.K. [Freie Univ. Berlin (Germany). Inst. fuer Physikalische und Theoretische Chemie; Seeliger, W.; Tributsch, H. [Hahn-Meitner-Inst., Berlin (Germany). Abt. Solare Energetik

    1996-12-31

    Photoanodic oxidation of I{sup -}, Fe(CN){sup 4-}{sub 6}, and Fe{sup 2+} at the (100)-face of a natural pyrite electrode (n-type FeS{sub 2}) has been investigated by photocalorimetry at 633 nm. The internal and external quantum efficiencies, {eta}{sub a} and {eta}{sub c}, respectively, the maximal internal efficiency, L{sub G}, for conversion of optical into electrical energy, the Peltier heat, Q{sub PE}, of the electrode process, and the reflectivity, R, of the electrode-solution interface have been determined at cathodically activated pyrite and (for I{sup -}, and Fe{sup 2+}) after additional treatment of the electrode with pyrazine or (1 H-benzotriazol-1-yl)-methylisocyanide (btic), L{sub G}, {eta}{sub a}, and {eta}{sub c} decrease in the order I{sup -} > Fe(CN){sup 4}{sub 6} > Fe{sup 2+}. At the bare electrode L{sub G} was 0.6% for I{sup -} 0.2% for Fe(CN){sup 4}{sub 6}, and 0.02% for Fe{sup 2+}. Adsorption of pyrazine and btic affects {eta}{sub a} and L{sub G} for oxidation of I{sup -}, without changing Q{sub PE} (-0.09 eV) and R (67%). With btic, L{sub G} increased to 0.9%. For oxidation of Fe{sup 2+}, the adsorbates diminish {eta}{sub a} and L{sub G} and shift Q{sub PE} from -0.24 eV at the bare electrode to -0.13 eV (pyrazine) and +0.23 eV (btic). The effects demonstrate different pathways for charge transfer from I{sup -} and Fe{sup 2+} to the electrode. The shift of Q{sub PE} for oxidation of Fe{sup 2+} is attributed to adsorbate-induced differences in the hydration entropies of the pyrite surface. (orig.) 27 refs.

  2. A high-pyrite semianthracite of Late Permian age in the Songzao Coalfield, southwestern China: Mineralogical and geochemical relations with underlying mafic tuffs

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Shifeng; Wang, Xibo; Chen, Wenmei [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, (China); Li, Dahua [Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, (China); Chou, Chen-Lin [Illinois State Geological Survey (Emeritus), 615 East Peabody Drive, Champaign, IL 61820, (United States); Zhou, Yiping [Yunnan Institute of Coal Geology Prospection, Kunming 650218, (China); Zhu, Changsheng; Li, Hang [Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, (China); Zhu, Xingwei; Xing, Yunwei; Zhang, Weiguo; Zou, Jianhua [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, (China)

    2010-09-01

    The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis. The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. The high pyrite (S{sub p,d} 8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids. Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO{sub 2}/Al{sub 2}O{sub 3} (1.13) but a higher Al{sub 2}O{sub 3}/Na{sub 2}O (80.1) value and is significantly enriched in trace elements including Sc (13.5 {mu}g/g), V (121 {mu}g/g), Cr (33.6 {mu}g/g), Co (27.2 {mu}g/g), Ni (83.5 {mu}g/g), Cu (48.5 {mu}g/g), Ga (17.3 {mu}g/g), Y (68.3 {mu}g/g), Zr (444 {mu}g/g), Nb (23.8 {mu}g/g), and REE (392 {mu}g/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO{sub 2}/Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}/Na{sub 2}O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for

  3. A high-pyrite semianthracite of Late Permian age in the Songzao Coalfield, southwestern China: Mineralogical and geochemical relations with underlying mafic tuffs

    Science.gov (United States)

    Dai, S.; Wang, X.; Chen, W.; Li, D.; Chou, C.-L.; Zhou, Y.; Zhu, Chen; Li, H.; Zhu, Xudong; Xing, Y.; Zhang, W.; Zou, J.

    2010-01-01

    The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis.The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. The high pyrite (Sp,d=8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids.Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO2/Al2O3 (1.13) but a higher Al2O3/Na2O (80.1) value and is significantly enriched in trace elements including Sc (13.5??g/g), V (121??g/g), Cr (33.6??g/g), Co (27.2??g/g), Ni (83.5??g/g), Cu (48.5??g/g), Ga (17.3??g/g), Y (68.3??g/g), Zr (444??g/g), Nb (23.8??g/g), and REE (392??g/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO2/Al2O3 and Al2O3/Na2O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for incompatible elements and chondrite-normalized diagram for rare earth elements) of coal and tuff, indicated that

  4. Study on the occurrence mode of invisible gold in pyrite of Muyanggou gold deposit%牧羊沟金矿黄铁矿中不可见金的赋存状态

    Institute of Scientific and Technical Information of China (English)

    李英; 郭月琴

    2012-01-01

    不可见金存在于许多金矿的黄铁矿中.以牧羊沟金矿为例,对黄铁矿中不可见金的存在形式进行了多种实验方法研究.化学分析和扫描电子显微镜实验结果表明,黄铁矿中不可见金大部分是自然金.分步溶解实验也证实,黄铁矿中的不可见金以自然金的形式存在.%Invisible gold occurs in pyrite of many gold deposits in the world. With Muyanggou gold deposit as example , the occurrence mode of invisible gold in pyrite was examined with many methods. Poly-spot chemical analysis and SEM examination of invisible gold in pyrite showed that most of the invisible gold was native gold. Invisible gold in pyrite do exist as native gold by step-dissolution experiments.

  5. Structural, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, GeN 2)

    Science.gov (United States)

    Ding, Y. C.; Xiang, A. P.; He, X. J.; Hu, X. F.

    2011-04-01

    The crystal structures, band structures, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, and GeN 2) are obtained from the density functional theory using the plane-wave pseudopotential (PWP) method within the local density and generalized gradient approximations. The formation enthalpies for AN 2 (A=C, Si, and Ge) compounds suggest the three structures that are stable. The calculated band structures show the indirect gaps ( Γ-R) in CN 2, SiN 2, and GeN 2. The intrinsic hardnesses of AN 2 (A=C, Si, and Ge ) compounds are calculated. Our results show that the cubic CN 2 and SiN 2 are superhard materials. Furthermore, we studied the optical properties such as the complex dielectric function and the electron energy loss spectra.

  6. A geochemical transport model for redox-controlled movement of mineral fronts in groundwater flow systems: A case of nitrate removal by oxidation of pyrite

    Science.gov (United States)

    Engesgaard, Peter; Kipp, Kenneth L.

    1992-01-01

    A one-dimensional prototype geochemical transport model was developed in order to handle simultaneous precipitation-dissolution and oxidation-reduction reactions governed by chemical equilibria. Total aqueous component concentrations are the primary dependent variables, and a sequential iterative approach is used for the calculation. The model was verified by analytical and numerical comparisons and is able to simulate sharp mineral fronts. At a site in Denmark, denitrification has been observed by oxidation of pyrite. Simulation of nitrate movement at this site showed a redox front movement rate of 0.58 m yr−1, which agreed with calculations of others. It appears that the sequential iterative approach is the most practical for extension to multidimensional simulation and for handling large numbers of components and reactions. However, slow convergence may limit the size of redox systems that can be handled.

  7. Study of coupled pyrite leached pyrolusite by functional microflora%功能菌群耦合黄铁矿浸出软锰矿的研究

    Institute of Scientific and Technical Information of China (English)

    马皛梅; 韩一凡; 路福平; 张小霞; 温丹; 刘勇金; 白利明; 胡影; 黄志勇

    2012-01-01

    [Objective] Three different environmental samples were mixed and inoculated into 100 mL fresh medium containing 1% pyrolusite and 1% pyrite.After enrichment we got bioleaching microflora.[Methods] Obtained microorganism consortia were used to leach pyrite and low-grade pyrolusite.Non-inoculation system was conducted as control group.[Results] Series of parameter were monitored during the process, including dynamic of consortia construction, pH value, leaching ratio of manganese, and XRD analyze of leaching residual.Leaching ratio of manganese was 92.48% after 15 days cultivation.And it was much higher than control group (40.34%).Within microbial consortia, Thiomonas sp.was the dominant species and its proportion increased from 2% to 93% of the consortia.Value of pH was declined from 4.0 to 2.5 in experimental group.Jarosite was observed in bioleaching residual.[Conclusion] Decrease of pH value and formation of jarosite indicated abundant sulfuric acid produced by bacterial metabolism.Result suggested that increasing bioleaching ratio of pyrite and pyrolusite due to dissociation of pyrite and decline of pH value by bacterial activity.This study could provide the basis for the further research of bioleaching mechanism and improvement of industrial art of low-manganese ore mineral resource.%[目的]将3种不同来源的环境样品混合后接种至含1%黄铁矿和1%软锰矿的培养基中进行富集培养,初步得到有一定浸矿功能的混合微生物菌群.[方法]菌群继续用于黄铁矿和低品位软锰矿共同浸出,设置未接种的体系作为对照.[结果]对浸出过程中菌群结构的变化、pH、锰浸出率和浸出残渣的成分进行分析,结果发现接种过微生物菌群的浸出体系在反应15 d后,锰浸出率达到92.48%,远高于未接菌对照组的40.34%;菌群中Thiomonas sp.所占比例从最初的2%上升到浸出结束时的93%.实验组的pH从最初的4.0下降到2.5;X射线衍射(XRD)分析发现,通

  8. Isotopic studies of authigenic sulfides, silicates and carbonates, and calcite and pyrite veinlets in the Creede Formation, San Juan Mountains, Southwest Colorado

    Science.gov (United States)

    Bethke, Philip M.; Rye, Robert O.; Finkelstein, David B.

    2000-01-01

    Sulfur isotope analysis of authigenic pyrite in the Creede Formation documents its precipitation by the reaction between iron in the volcaniclastic sediments and H2S formed through bacteriogenic reduction of sulfate added to the lake during and immediately following repeated volcanic eruptions during sedimentation. Pyrite veinlets in the underlying Snowshoe Mountain Tuff were formed by the percolation of H2S-bearing pore waters into fractures in the tuff. Conventional analyses of bulk samples of authigenic pyrite range from -20.4% to 34.5% essentially equivalent to the range of -30% to 40% determined using SHRIMP microprobe techniques. Conventional analyses of bulk samples of pyrite from veinlets in the Snowshow Mountain Tiff range from -3.5% to 17.6% much more limited than the ranges of -23% to 111% and -15.6% to 67.0% determined by SHRIMP and laser ablation microbeam techniques, respectively. The extreme range of δ34S for the veinlets is interpreted to be the result of continued fractionation of the already 34S-depleted pore water. Oxygen isotope analysis of authigenic smectite, kaolinite, and K-feldspar together with fluid-inclusion temperatures and oxygen isotope analysis of calcite coexisting with kaolinite indicate that the smectites formed early during burial diagenesis, in accord with petrographic observations. The 40Ar/39Ar dating of K-feldspar, concorfance of K-feldspar, kaolinite, and calcite δ18O values, and fluid-inclusion temperatures in calcite, indicate that the sediments at core hole CCM-1 were subjected to a hydrothermal event at 17.6 Ma. The minerals formed oxygen-shifted meteoric waters with δ18O values of ~-9% Smecities at CCM-1 at least partially exchanged with these waters. Carbon and oxygen isotope analysis of authigenic calcites in the Creede Formation show that they formed over a wide range of temperatures from fluids having a wide range of isotopic composition, presumably over an extended period time. Some of the cements apparently

  9. Microbial Diversity and Its Relationship to Physicochemical Characteristics of the Water in Two Extreme Acidic Pit Lakes from the Iberian Pyrite Belt (SW Spain.

    Directory of Open Access Journals (Sweden)

    Esther Santofimia

    Full Text Available The Iberian Pyrite Belt (IPB hosts one of the world's largest accumulations of acidic mine wastes and pit lakes. The mineralogical and textural characteristics of the IPB ores have favored the oxidation and dissolution of metallic sulfides, mainly pyrite, and the subsequent formation of acidic mining drainages. This work reports the physical properties, hydrogeochemical characteristics, and microbial diversity of two pit lakes located in the IPB. Both pit lakes are acidic and showed high concentrations of sulfate and dissolved metals. Concentrations of sulfate and heavy metals were higher in the Nuestra Señora del Carmen lake (NSC by one order of magnitude than in the Concepción (CN lake. The hydrochemical characteristics of NSC were typical of acid mine waters and can be compared with other acidic environments. When compared to other IPB acidic pit lakes, the superficial water of CN is more diluted than that of any of the others due, probably, to the strong influence of runoff water. Both pit lakes showed chemical and thermal stratification with well defined chemoclines. One particular characteristic of NSC is that it has developed a chemocline very close to the surface (2 m depth. Microbial community composition of the water column was analyzed by 16S and 18S rRNA gene cloning and sequencing. The microorganisms detected in NSC were characteristic of acid mine drainage (AMD, including iron oxidizing bacteria (Leptospirillum, Acidithiobacillus ferrooxidans and facultative iron reducing bacteria and archaea (Acidithiobacillus ferrooxidans, Acidiphilium, Actinobacteria, Acidimicrobiales, Ferroplasma detected in the bottom layer. Diversity in CN was higher than in NSC. Microorganisms known from AMD systems (Acidiphilium, Acidobacteria and Ferrovum and microorganisms never reported from AMD systems were identified. Taking into consideration the hydrochemical characteristics of these pit lakes and the spatial distribution of the identified

  10. 硫铁矿烧渣双酸酸解工艺研究%Study on decomposition process of pyrite cinder with hydrochloric acid and sulfuric acid

    Institute of Scientific and Technical Information of China (English)

    左大学; 王仁宗

    2012-01-01

    The decomposition process of pyrite cinder with hydrochloric acid and sulfuric acid , and its influence factors are studied. Through orthogonal test, the optimum process conditions are confirmed including: the consumption factor of hydrochloric acid with w(HC1) of 37% is 0.12; the consumption factor of sulfuric acid with w(H2SO4) of 65%-70% is 0.95, the reaction temperature is of 125 ℃, the reaction time is of 4h. The decomposition rate of pyrite cinder can reach to above 95%, and the product ferric sulfate solution can be used to produce polymeric ferric sulfate and iron oxide pigments.%研究了硫铁矿烧渣双酸酸解工艺及影响酸解的因素。通过正交实验,找到最适宜的工艺条件:w(HCl)37%,盐酸用量系数为0.12,硫酸用量系数为0.95,硫酸W(H2SO4)为65%~70%,反应温度为125℃,反应时间为4h,酸解率可达95%以上,制得的硫酸铁盐溶液可用作生产聚合硫酸铁及氧化铁系颜料的原料。

  11. Experimental Study on Microbial Desulfurization of Pyrite Cinder%硫铁矿烧渣微生物脱硫试验研究

    Institute of Scientific and Technical Information of China (English)

    周文博; 邹平; 孙珮石

    2013-01-01

    The mixed culture of acidophilic bacteria was used to remove sulfur from pyrite cinder .The effects of different culture mediums ,solid-liquid ratio ,pH ,inoculum volume ,surfactant usage , temperature and particle size on the desulfurization rate were examined by shake flask experiments . The results indicated that the optimal conditions of desulfurization were solid-liquid ratio of 3∶10 , inoculation amount of 3% ,pH of 1 .5 ,rotation speed of 180 r/min and temperature of 25 ℃ .After 72 hours leaching ,the total sulfur content in the pyrite cinder was reduced significantly from 1 .78% to 0 .28% with a desulfurization rate of 86 .02% ,and iron content was enriched effectively from 53 .78%to 59 .56% .The desulfurization slag meet the requirements of ore concentrate for steelmaking .%  研究了从高硫硫铁矿烧渣中微生物脱硫,考察了培养基种类、矿浆固液质量体积比、pH、细菌接种量、表面活性剂、温度及粒度等因素对微生物脱硫的影响。试验结果表明:在菌种接种量3%、矿浆pH=1.5、温度30℃条件下对固液质量体积比3∶10的硫酸渣矿浆进行脱硫,72 h内,烧渣的硫质量分数由1.78%降至0.28%,脱硫率达86.02%,铁品位由53.78%提高到59.56%;脱硫后的烧渣符合铁精矿要求。

  12. High-resolution quadruple sulfur isotope analyses of 3.2 Ga pyrite from the Barberton Greenstone Belt in South Africa reveal distinct environmental controls on sulfide isotopic arrays

    Science.gov (United States)

    Roerdink, Desiree L.; Mason, Paul R. D.; Whitehouse, Martin J.; Reimer, Thomas

    2013-09-01

    Multiple sulfur isotopes in Paleoarchean pyrite record valuable information on atmospheric processes and emerging microbial activity in the early sulfur cycle. Here, we report quadruple sulfur isotope data (32S, 33S, 34S, 36S) analyzed by secondary ion mass spectrometry from pyrite in a 3.26-3.23 Ga sedimentary barite deposit in the Barberton Greenstone Belt, South Africa. Our results demonstrate the presence of distinct pyrite populations and reproducible isotopic arrays in barite-free and barite-rich samples. The most 34S-depleted signatures with weakly positive Δ33S/δ34S were found in disseminated pyrite in barite, whereas positive Δ33S-values with negative Δ33S/δ34S and Δ36S/Δ33S = -0.9 ± 0.2 were exclusively observed in pyrite hosted by chert, dolomite, conglomerate and breccia. We interpret these variations to be related to local redox reactions and mixing in the sulfide phase, rather than representing primary atmospheric variability alone. The strong correlation between lithology and isotopic composition indicates distinct environments of sulfide formation linked to local sulfate concentrations and fluctuating inputs from different sulfur metabolisms. Strongly 34S-depleted sulfide was formed by microbial sulfate reduction at [SO42-] > 200 μM during deposition of barite-rich sediments, whereas isotope effects were suppressed when sulfate levels decreased during deposition of terrigeneous clastic rocks. Positive Δ33S-values indicate an increased input of sulfide derived from elemental sulfur metabolisms when sulfate concentrations fell below 200 μM. Our results support an important role for local sulfate concentrations on the expression of biogenic sulfur isotope signatures in some of the oldest rocks on Earth.

  13. Reaction mechanism of coal liquefaction: hydrogenolysis of model compound using synthetic pyrite as catalysts. 7. Property change of synthetic pyrite catalyst with the time after production; Sekitan ekika hanno kiko (model kagobutsu no hanno). 7. Gosei ryukatetsu shokubai no keiji henka ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Ito, H.; Meno, H.; Uemaki, O.; Shibata, T.; Tsuji, T. [Hokkaido University, Sapporo (Japan)

    1996-10-28

    Reactions of various model compounds were investigated using synthetic pyrites for coal liquefaction. In this study, successive changes of the catalysts were investigated from the reactions of model compounds by using three different synthetic pyrites with the lapse of time after production. Benzyl phenyl ether, dibenzyl, and n-octylbenzene were used as model compounds. Reactions were conducted in an autoclave, into which sample, catalyst, decalin as solvent, and initial hydrogen pressure 10 MPa were charged. The autoclave was held at 450 or 475{degree}C of reaction temperature for 1 hour. The catalyst with a shorter lapse of time after production acted to hydrogen transfer, and inhibited the formation of condensation products due to the stabilization of decomposed fragment. It also acted to isomerization of materials by cutting alkyl side chains. When adding sulfur to the catalyst with longer lapse of time after production under these reaction conditions, it inhibited the formation of condensation products for the reaction of benzyl phenyl ether. However, it did not provide the effect for the reaction of n-octylbenzene. 5 refs., 3 figs.

  14. Open system sulphate reduction in a diagenetic environment - Isotopic analysis of barite (δ34S and δ18O) and pyrite (δ34S) from the Tom and Jason Late Devonian Zn-Pb-Ba deposits, Selwyn Basin, Canada

    Science.gov (United States)

    Magnall, J. M.; Gleeson, S. A.; Stern, R. A.; Newton, R. J.; Poulton, S. W.; Paradis, S.

    2016-05-01

    Highly positive δ34S values in sulphide minerals are a common feature of shale hosted massive sulphide deposits (SHMS). Often this is attributed to near quantitative consumption of seawater sulphate, and for Paleozoic strata of the Selwyn Basin (Canada), this is thought to occur during bacterial sulphate reduction (BSR) in a restricted, euxinic water column. In this study, we focus on drill-core samples of sulphide and barite mineralisation from two Late Devonian SHMS deposits (Tom and Jason, Macmillan Pass, Selwyn Basin), to evaluate this euxinic basin model. The paragenetic relationship between barite, pyrite and hydrothermal base metal sulphides has been determined using transmitted and reflected light microscopy, and backscatter electron imaging. This petrographic framework provides the context for in-situ isotopic microanalysis (secondary ion mass spectrometry; SIMS) of barite and pyrite. These data are supplemented by analyses of δ34S values for bulk rock pyrite (n = 37) from drill-core samples of un-mineralised (barren), siliceous mudstone, to provide a means by which to evaluate the mass balance of sulphur in the host rock. Three generations of barite have been identified, all of which pre-date hydrothermal input. Isotopically, the three generations of barite have overlapping distributions of δ34S and δ18O values (+22.5‰ to +33.0‰ and +16.4‰ to +18.3‰, respectively) and are consistent with an origin from modified Late Devonian seawater. Radiolarian tests, enriched in barium, are abundant within the siliceous mudstones, providing evidence that primary barium enrichment was associated with biologic activity. We therefore propose that barite formed following remobilisation of productivity-derived barium within the sediment, and precipitated within diagenetic pore fluids close to the sediment water interface. Two generations of pyrite are texturally associated with barite: framboidal pyrite (py-I), which has negative δ34S values (-23‰ to -28

  15. The chemical conditions of the late Archean Hamersley basin inferred from whole rock and pyrite geochemistry with Δ33S and δ34S isotope analyses

    Science.gov (United States)

    Gregory, Daniel D.; Large, Ross R.; Halpin, Jacqueline A.; Steadman, Jeffery A.; Hickman, Arthur H.; Ireland, Trevor R.; Holden, Peter

    2015-01-01

    The well-preserved late Archean sedimentary rocks of the Fortescue and Hamersley Basins in Western Australia offer fascinating insights into early earth ocean chemistry prior to the Great Oxidation Event (GOE). In this study, we use a combination of whole rock geochemistry, LA-ICPMS trace element analysis of sedimentary pyrite and pyrrhotite and SHRIMP-SI sulfur isotope analyses to elucidate the chemical changes in these sedimentary rocks. These proxies are used to examine chemical conditions of the ocean during the late Archean. Two to three periods of oxygen enrichment prior to the deposition of banded iron formations (BIF) can be identified. One minor stage of general increase in whole rock enrichment factors and trace element content of pyrite is observed up stratigraphy in the Jeerinah Formation, Fortescue Basin and a more substantial stage is present in the Paraburdoo and Bee Gorge Members of the Wittenoom Formation, Hamersley Basin. Some of the trace element enrichments indicate organic matter burial flux (Ni, Cr, Zn, Co and Cu) which suggests an increase in biological productivity. If the increased biological activity reflects an increase in cyanobacteria activity then an associated increase in oxygen is likely to have occurred during the deposition of the Bee Gorge Member. An increase in atmospheric oxygen would result in continental weathering of sulfide and other minerals, increasing the trace element content of the water column via erosion and avoiding excessive depletion of trace elements due to drawdown in seawater. Since some of these trace elements may also be limiting nutrients (such as Mo and Se) for the cyanobacteria, the degree of biological productivity may have further increased due to the increasing amount of trace elements introduced by oxygenation in a positive feedback loop. These periods of increased productivity and oxygen rise stopped prior to the onset of BIF deposition in the Hamersley Basin. This may be due to the ocean reaching an

  16. Iron recovery from pyrite cinder by flotation process to remove impurities in sulfide concentrates%硫精矿除杂提纯浮选工艺回收利用硫酸烧渣中的铁

    Institute of Scientific and Technical Information of China (English)

    冯国臣; 高金昌

    2015-01-01

    Pyrite cinder is the product of oxidizing roasting of pyrite ores. The technical index in iron recovery from pyrite cinder keeps low. The main reason for it is that fine ferric oxide particles produced in the oxidizing roasting process of pyrite ores will in high temperature interact with impurities and gangue minerals including mutual inclu-ding,sticking and polluting. The paper modifies conventional process of iron recovery from pyrite cinder,and turns to a sulfide concentrates flotation process to concentrate ferric sulfide,that is to increase the mass fraction of ferric sulfide in raw materials of pyrites,so that gangue minerals and impurities are removed from the raw materials,reaching a sul-fur grade over 50 % to 52 % and sulfur and iron grade of 90 % to 92 %. The high grade sulfur concentrates are used to made sulfuric acid. The iron in pyrite cinder reaches 63 % to 67 % making the entire cinder directly become iron concentrates without the need of further beneficiation,which is an effective way to utilize the iron in the cinder. The reason for higher technical index lies in the choice of sulfur flotation for impurity removal. High grade sulfur concen-trates making sulfuric acid avoids unwanted minerals hindering the oxidizing roasting of ferric sulfide and high content of impurities,low iron grade and low ore-dressing technical index in the process of iron recovery from pyrite cinder.%硫酸烧渣是硫铁矿制酸氧化焙烧产物;从硫酸烧渣中选铁的工艺技术指标一直不高,其主要原因是硫铁矿氧化焙烧过程中生成的氧化铁矿物颗粒微细,高温时新生成的氧化铁矿物颗粒会与杂质和脉石矿物颗粒相互包裹、相互黏结、相互污染. 该文将硫酸烧渣选铁改为硫精矿再浮选提纯硫化铁,即通过提纯硫酸原料中硫化铁的质量分数,从而去除原料中的脉石和杂质,使硫酸原料中硫品位达到50 % ~52 %(黄铁矿型原料)以上,硫、铁回收率均达到90 % ~92 %;

  17. 硫酸渣辐射屏蔽材料制备与效果评价%Preparation and Effect Assessment of Gamma Ray Shielding Materials Containing Pyrite Cinder

    Institute of Scientific and Technical Information of China (English)

    王烨; 张晓文; 王续琨; 钟永明; 吕俊文; 彭莹; 李密

    2015-01-01

    采用直接掺杂法分别制备了硫酸渣—混凝土、硫酸渣—粉煤灰—混凝土和铅—混凝土屏蔽材料,用NaI( TI)探测器、多道脉冲幅度分析仪和WINXCOM软件分析它们对γ射线的辐射防护能力。结果表明:硫酸渣制备的屏蔽材料辐射防护性能优于已有的石灰岩制备的屏蔽材料和FPPB屏蔽材料,可用作射线屏蔽材料,并有望实现固体废弃物的合理利用。%Pyrite cinder-concrete,pyrite cinder-fly ash-concrete and lead-concrete shielding materials have been prepared by means of direct doping. NaI ( TI) detectors,multi-channel pulse amplitude analyzer and WinXCOM software were used to test and analyze their radia-tion shielding property. The results show that the radiation shielding property of shielding material containing pyrite cinder is better than the existing shielding materials prepared from limestone and FPPB. Consequently,it can be used effectively as shielding materials against gamma radiation,and is expected to achieve the goal of rational utilization of solid waste.

  18. Organic carbon, nitrogen, sulphur, and {delta}{sup 34}S composition of pyrite and pore waters in the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.F.; Matsumoto, R.; Tomaru, H.; Anton, D. [Tokyo Univ., Tokyo (Japan). Dept. of Earth and Planetary Science

    2005-07-01

    This study examined the geochemical characteristics of the gas-hydrate-bearing sediments and interstitial waters in the JAPEX/JNOC/GSC et al. Mallik 5L-38 research well. Samples taken from 890 m to 1150 m were examined. The {delta}{sup 34}S values of interstitial water sulphates and sedimentary pyrite suggest that high sulphate concentrations in interstitial waters and pyrite formations were influenced by the invasion of seawater and burial diagenesis. Four depositional environmental zones were detected based on organic carbon-nitrogen ratios, organic-carbon to total-carbon ratios, organic-carbon to pyrite-sulphur ratios and {delta}{sup 34}S values. The first zone which occurs at 890 to 930 m, is a fluvial-plain, storm-dominated environment. The second zone occurs at 930 to 1000 m, and is a marsh and shallow-marine deposits from a lower delta-plain environment. The third zone occurs at 1000 to 1070 m, and is an upper delta plain-swamp with minimal marine influence. The fourth zone occurs at 1070 to 1150 m, and is a mixture of freshwater and marine environments of a lower-upper delta-plain setting. These environmental zones are in agreement with facies models determined from lithological features.

  19. Effect of CO2 and N2 on microbial community changes during column bioleaching of low-grade high pyrite-bearing chalcocite ore

    Institute of Scientific and Technical Information of China (English)

    陈勃伟; 武彪; 刘兴宇; 温建康

    2015-01-01

    Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40 °C with aeration of CO2 and N2. Ore samples were collected at day 43, 64, 85, 106 and subjected to microbial community analysis by 16S rRNA gene clone library. Phylogenetic analyses of 16S rDNA fragments revealed that the retrieved sequences are mainly related to genus Acidithiobacillus,Leptospirillum andSulfobacillus. Aeration of CO2 and N2 significantly impacted the microbial community composition. When CO2 was aerated, the proportion of genusAcidithiobacillus considerably increased, whereas the proportion of genusLeptospirillum and genusSulfobacillus declined. However, with the aeration of N2, the proportion of genusAcidithiobacillus andLeptospirillum increased, but genusSulfobacillus decreased. When there was no aeration, the microbial community was similar to the inocula with the proportion of genusLeptospirillum mounted. These results indicated that the limitation of oxygen could change the bioleaching microbial community and the aeration of CO2 and N2 was favourable for the growth of sulfur-oxidizer (At. caldus) and iron-oxidizer (L. ferriphilum) respectively, which could be used for the regulation of microorganisms’ role in mineral bioleaching.

  20. [FeS/FeS2], a redox system for the origin of life (some experiments on the pyrite-hypothesis).

    Science.gov (United States)

    Kaschke, M; Russell, M J; Cole, W J

    1994-02-01

    The FeS/FeS, redox system, whose importance is stressed in recent theories on the origin of life, has been tested experimentally. In this paper it is demonstrated by thermodynamical calculations as well as by experiments, that cyclohexanone, which served as model compound, can be reduced by the aforementioned redox system. Reactions were carried out in methanol and DMF at 25 degrees C and at 100 degrees C. Besides products that were synthesised in both solvents, like cyclohexanethiol and dicyclohexydisulphide, special compounds were obtained in methanol and in DMF, because of the involvement of the respective solvent in the reaction. Yields of reduced compounds were lower in methanol owing to compound that hindered the reduction (cyclohexylketal). With increasing temperature and duration the amount of reduced compounds increased. Further experiments have shown that 1,1-cyclohexanedithiol is likely to be a necessary intermediate for the reduced products. The experiments give evidence to the 'pyrite hypothesis', which postulates that the FeS/FeS2, redox system was of importance for the origin of life.

  1. Development of an on-line image analysis for assessment of pyrite liberation. Technical report, December 1, 1992--February 28, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Yen, M.S.C.; Chu, P.T.C. [Southern Illinois Univ., Carbondale, IL (United States); Ho, K. [Illinois Clean Coal Inst., Carterville, IL (United States)

    1993-05-01

    An automation procedure based on the principles of image processing is proposed to perform the analysis of pyrite/minerals liberation of coal. To make the automated image analysis system possible, a data base of the light reflectance characteristics of different coal constituents must be established. Characterization of coal images through the analysis of their histogram was conducted. In general, it was found that the distinction of coal particles or particle groups may be accomplished by determining the gray levels of zero pixel or by taking average gray level of each particle. In particular, when the gray level averaging is applied, the spread of gray levels of a given maceral becomes smaller. In other words, the spread in gray level among different maceral group becomes larger. This has led to a distinct boundary between different material group of coal. Two computer programs based on these findings are being developed. The implementation of these criteria will cover most of the coal samples that are previously analyzed. Consideration of special cases will require additional data analysis of histogram.

  2. He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGE-polymetallic Deposits in Lower Cambrian Black Rock Series, South China

    Institute of Scientific and Technical Information of China (English)

    SUN Xiaoming; WANG Min; XUE Ting; MA Mingyang; LI Yinhe

    2004-01-01

    He-Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGEpolymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore-forming fluids possess a low 3He/4He ratio, varying from 0.43x10-8 to 26.39×10-8, with corresponding R/Ra value of 0.003-0.189. The 40Ar/36Ar ratios are 258-287, close to those of airsaturated water (ASW). He-Ar isotopic indicator studies show that the ore-forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle-derived fluid or deep-derived magmatic water might be negligible. The PGE-polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was expelled and migrated laterally along strata because of the pressure generated by overlying sediments. The basinal hot brine ascended along faults, mixed with sea water and finally deposited ore minerals.

  3. Preparation of Carbon Nanotube/TiO2 Mesoporous Hybrid Photoanode with Iron Pyrite (FeS2) Thin Films Counter Electrodes for Dye-Sensitized Solar Cell

    Science.gov (United States)

    Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Ozer, Oguz Can; Asgin, Mansur; Cebeci, Hulya; Urk, Deniz; Mucur, Selin Pravadili

    2016-05-01

    Multi-walled carbon nanotube (MWCNT)/TiO2 mesoporous networks can be employed as a new alternative photoanode in dye-sensitized solar cells (DSSCs). By using the MWCNT/TiO2 mesoporous as photoanodes in DSSC, we demonstrate that the MWCNT/TiO2 mesoporous photoanode is promising alternative to standard FTO/TiO2 mesoporous based DSSC due to larger specific surface area and high electrochemical activity. We also show that iron pyrite (FeS2) thin films can be used as an efficient counter electrode (CE), an alternative to the conventional high cost Pt based CE. We are able to synthesis FeS2 nanostructures utilizing a very cheap and easy hydrothermal growth route. MWCNT/TiO2 mesoporous based DSSCs with FeS2 CE achieved a high solar conversion efficiency of 7.27% under 100 mW cm‑2 (AM 1.5G 1-Sun) simulated solar irradiance which is considerably (slightly) higher than that of A-CNT/TiO2 mesoporous based DSSCs with Pt CE. Outstanding performance of the FeS2 CE makes it a very promising choice among the various CE materials used in the conventional DSSC and it is expected to be used more often to achieve higher photon-to-electron conversion efficiencies.

  4. The effect of the introduction of exogenous strain Acidithiobacillus thiooxidans A01 on functional gene expression, structure and function of indigenous consortium during pyrite bioleaching.

    Science.gov (United States)

    Liu, Yi; Yin, Huaqun; Zeng, Weimin; Liang, Yili; Liu, Yao; Baba, Ngom; Qiu, Guanzhou; Shen, Li; Fu, Xian; Liu, Xueduan

    2011-09-01

    Acidithiobacillus thiooxidans A01 was added to a consortium of bioleaching bacteria including Acidithiobacilluscaldus, Leptospirillumferriphilum, Acidithiobacillus ferrooxidans, Sulfobacillus thermosulfidooxidans, Acidiphilium spp., and Ferroplasma thermophilum cultured in modified 9 K medium containing 0.5% (w/v) pyrite, and 10.7% increase of bioleaching rate was observed. Changes in community structure and gene expression were monitored with real-time PCR and functional gene arrays (FGAs). Real-time PCR showed that addition of At. thiooxidans caused increased numbers of all consortium members except At. caldus, and At. caldus, L. ferriphilum, and F. thermophilum remained dominant in this community. FGAs results showed that after addition of At. thiooxidans, most genes involved in iron, sulfur, carbon, and nitrogen metabolisms, metal resistance, electron transport, and extracellular polymeric substances of L. ferriphilum, F. thermophilum, and Acidiphilium spp., were up-regulated while most of these genes were down-regulated at 70-78 h in At. caldus and up-regulated in At. ferrooxidans, then down-regulated at 82-86 h.

  5. Preparation of pre-reduced pellet using pyrite cinder containing nonferrous metals with high temperature chloridizingreduction roasting technology—Effect of CaCl2additive

    Institute of Scientific and Technical Information of China (English)

    陈栋; 朱德庆; 洪澜; 陈瑶; 许继芳; 伍凌

    2015-01-01

    The role of CaCl2 during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. The effects of CaCl2 dosage on pelletizing, preheating and reduction were investigated. The results show that CaCl2 can improve the wet drop strength but reduces the thermostability of pyrite cinder green balls. When the dosage of CaCl2 exceeds 1%, the compressive strength of preheated pellets decreases while the growth of iron oxide particles is improved. Furthermore, the compressive strength of pre-reduced pellets increases but the metallization degree of pre-reduced pellets decreases with CaCl2 additive. The removal tests indicate that Zn can be removed completely without CaCl2 additive, Cu is removed only under the condition with CaCl2 additive and part of Pb must be removed by CaCl2 additive.

  6. Preparation of pre-reduced pellet using pyrite cinder containing nonferrous metals with high temperature chloridizing- reduction roasting technology-Effect of CaCl2 additive

    Institute of Scientific and Technical Information of China (English)

    陈栋; 朱德庆; 洪澜; 陈瑶; 许继芳; 伍凌

    2015-01-01

    The role of CaCl2 during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. The effects of CaCl2 dosage on pelletizing, preheating and reduction were investigated. The results show that CaCl2 can improve the wet drop strength but reduces the thermostability of pyrite cinder green balls. When the dosage of CaCl2 exceeds 1%, the compressive strength of preheated pellets decreases while the growth of iron oxide particles is improved. Furthermore, the compressive strength of pre-reduced pellets increases but the metallization degree of pre-reduced pellets decreases with CaCl2 additive. The removal tests indicate that Zn can be removed completely without CaCl2 additive, Cu is removed only under the condition with CaCl2 additive and part of Pb must be removed by CaCl2 additive.

  7. Pyrite cinder as a cost-effective heterogeneous catalyst in heterogeneous Fenton reaction: decomposition of H(2)O(2) and degradation of Acid Red B.

    Science.gov (United States)

    Wu, Deli; Liu, Yanxia; Duan, Dong; Ma, Luming

    2014-01-01

    Pyrite cinder (PyC) was employed as a heterogeneous Fenton-like catalyst, and its catalytic activity was evaluated in view of the effects of catalyst dosage, pH and leaching metal ions. PyC showed significant reactivity, and the pseudo-first-order kinetic rate constant for decomposition of H(2)O(2) and degradation of Acid Red B (ARB) were 3.4 and 14.89 (10⁻³ min⁻¹) respectively when pH = 5. When 20 g/L PyC was added into 10 mM H(2)O(2) solution in neutral pH, H(2)O(2) could be completely degraded within 4 h, and more than 90% ARB was removed. Leaching metal ions from PyC were found to have little effect on decomposition of H(2)O(2) or on degradation of ARB. PyC still had high catalytic activity after five successive runs. The decomposition mechanism of H(2)O(2) was analyzed and the Haber-Weiss mechanism was employed in this paper. The electron spin resonance image showed •OH was produced and increased between 3 and 5 min in the PyC catalyzing H(2)O(2) reaction, which demonstrated that PyC had a durable ability to produce •OH.

  8. 润磨强化硫酸渣制备氧化球团的技术及机理%Enhancing technology and mechanism of oxidized pellet prepared from pyrite cinder by moisture grinding

    Institute of Scientific and Technical Information of China (English)

    白国华; 周晓青; 范晓慧; 李建臣

    2011-01-01

    In connection with characteristic of pyrite cinder, the characteristic of oxidized pellet prepared from pyrite cinder and the mechanism of moisture grinding on pellet preparation were studied. The results show that the strength of green balls is very low, and the moisture of green balls is fairly higher without moisture grinding. Moisture grinding is an effective means to improve the strength and reduce the moisture of green ball with the less dosage of bentonite by improving size distribution, specific surface area and lowering the porosity of green balls. Moisture grinding can improve the roasting performance of pyrite cinder pellet by improving the surface energy of pyrite cinder and increasing contact points between particles, which has the advantages of diffusion. The compressive strength of pellets overruns 3 kN per pellet with moisture grinding after roasted at 1 150℃ for 10 min. The roasting temperature can be greatly reduced. The high quality oxidized pellet can be produced as a blast furnace feed by using pyrite cinder.%从硫酸渣本身特点出发,对硫酸渣制备氧化球团的特点及润磨在球团制备过程中的作用机理进行研究。研究结果表明:无润磨的硫酸渣生球强度极差,水分较高,润磨可改善硫酸渣的粒度组成、比表面积,降低生球的孔隙率,从而有效降低膨润土用量,大幅提高生球的强度及降低生球的水分;润磨也能提高硫酸渣颗粒活性,增加颗粒与颗粒之间的接触点,使质点利于扩散,从而改善硫酸渣球团的焙烧性能,润磨后的球团在焙烧温度为1150℃、焙烧时间为10 min的条件下,便可获得抗压强度大于3 kN/个的球团,大大降低了球团的焙烧温度。使用硫酸渣能生产出优质的球团供高炉使用。

  9. 利用钠盐助磨剂制备超细黄铁矿粉体的界面光学特性%Interfacial and optical characteristics of pyrite ultrafine powder prepared using sodium salts as grinding additives

    Institute of Scientific and Technical Information of China (English)

    李丹; 尹周澜; 陈启元

    2012-01-01

    以超细黄铁矿粉体为研究对象,利用吸光度法研究黄铁矿在液相中添加六偏磷酸钠、油酸钠、硅酸钠、多聚磷酸钠、十二烷基硫酸钠后的分散性.研究结果表明:含有表面活性基团的油酸钠和十二烷基硫酸钠对于黄铁矿具有较好的分散效果.对这2种效果较好的添加剂的分散条件如pH、超声时间的影响进行分析,并对黄铁矿在这两种添加剂中的界面性质包括沉降曲线、表面电位和润湿性进行研究.在此基础上,用红外光谱对油酸钠和十二烷基硫酸钠作为助磨剂时制备黄铁矿超细粉体的光学性质结合扫描电镜进行研究,结果表明在研磨过程中黄铁矿粉体有部分硫被氧化成硫酸根,油酸钠与十二烷基硫酸钠助磨剂的使用有利于降低黄铁矿研磨过程中的氧化程度.%Using pyrite ultrafine powder as the object of this work, the dispersion of pyrite in different sodium salt additives such as sodium hexametaphosphate, sodium oleate, sodium silicate, sodium polyphosphate, and sodium dodecyl sulfate was analyzed with spectrometry. The results indicate that two surfactants namely sodium dodecyl sulfate and sodium oleate show better disperisibility for pyrite. The effects of some dispersion conditions such as pH and ultronication time on the disperisibility of dium dodecyl sulfate and sodium oleate were analyzed. The interfacial properties of pyrite dispersed in sodium dodecyl sulfate and sodium oleate solutions were investigated with precipitation curve, zeta potentiometry, and wettability. Based on these results, pyrite ultrafine powder was prepared using sodium dodecyl sulfate and sodium oleate as grinding additives, whose optical characteristics were studied by FTIR spectrometry in cooperation with scanning electron microscopy. The FTIR spectra indicate that although some parts of sulfur in pyrite are oxidized into sulfate during the grinding, sodium dodecyl sulfate and sodium oleate can

  10. Gold-bearing Characteristics of Arsenian Pyrites and Arsenopyrites in the Bojitian Carlin-type Gold Deposits, Southwestern Guizhou Province, Southwest China%黔西南簸箕田卡林型金矿中含砷黄铁矿和毒砂的赋金特征研究

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

      黔西南簸箕田金矿是新近发现的一个中型卡林型金矿。该文在显微镜矿相学观察的基础上,采用电子探针显微分析,包括背散射电子图像、点分析和面分析,对金矿中的赋金矿物展开了基本特征和赋金状态研究,发现含砷黄铁矿和毒砂是主要的赋金矿物。赋金黄铁矿又以环带状和细粒自形为主,莓球状、粗粒以及条带状次之。这些黄铁矿成因复杂,并且可能普遍受到热液蚀变作用影响。环带状黄铁矿核部中的金可能主要以“不可见”超显微包裹金(纳米级自然金,Au0)的形式赋存,而环带部分中的金可能以固溶体金(Au+)的形式赋存,并也可能存在纳米级自然金(Au0)。相比而言,莓球状、粗粒和条带状黄铁矿中的金既可能含有纳米级自然金(Au0),也可能含有固溶体金(Au+)。对于毒砂,单独的毒砂和黄铁矿-毒砂集合体中的毒砂均为热液成因,都赋存金,但以单独的毒砂为主,金以“不可见”超显微包裹金(纳米级自然金, Au0)的形式存在。%The recently discovered Bojitian carlin-type gold deposits are located in the southwestern Guizhou Province and are middle in scale. In this study, we investigated the mineral’s gold-bearing characteristics based on integrated studies of microscope observations and electron-probe back-scattered image, element spot and element map analyses. Analytical results show that arsenian pyrites and arsenopyrites are major gold-bearing minerals. The gold-bearing pyrites are dominated by zoned arsenian pyrites and fine-grained arsenian pyrites, followed by framboidal pyrites, coarse-grained pyrites, and banded pyrites. These pyrites have complex origins and most of them may hare undergone hydrothermal alterations. The gold in the cores of the zoned arsenian pyrites occurs as“invisible”microscopic inclusions of gold grains (nanoparticles of native gold

  11. Pyrite framboid diameter distribution in the Lower Oligocene black shales of the Vrancea Nappe as an indicator of changes in redox conditions, Eastern Outer Carpathians, Romania

    Science.gov (United States)

    Wendorff, Małgorzata; Marynowski, Leszek; Rospondek, Mariusz

    2016-04-01

    Studies of recent and ancient sediments revealed that the diameter distribution of pyrite framboids may be reliably used to characterise oxygen-restricted environments and distinguish ancient euxinic conditions (water column hydrogen sulphide bearing thus oxygen-free) from anoxic, non-sulfidic or dysoxic (oxygen-poor) conditions. Such diagnoses are of great importance when reconstructing palaeoenvironments in ancient basins and the processes of source rocks formation. During Oligocene to early Miocene time an extensive accumulation of organic matter (OM)-rich sediments occurred in the entire Paratethys including the Carpathian Foredeep, which was closed forming fold-thrust belt of the Outer Carpathians. These OM-rich black shales are represented by so-called Menilite shales, widely considered as hydrocarbon source rocks, which constitute as well a detailed archive for palaeoenvironmental changes. The purpose of this preliminary study is to characterise the depositional environment of the Lower Oligocene black shales basing on the pyrite framboid diameter distribution. Five samples of finely laminated black shales were selected from the Nechit section outcropping in the Bistrica half-window of the Vrancea Nappe in the Eastern Outer Carpathians, E Romania. At least 100 framboid diameters were measured on polished blocks using scanning electron microscope in a back-scattered electron mode. Framboids from four samples starting from the lowermost part of the section exhibit a narrow range of diameters from 1.0 to 11.5 μm; mean value ranges from 3.65 to 4.85 μm. Small-sized framboids (10 μm) are absent or rare (max. 2%). Within the sample from the uppermost part of the section framboids reveal more variable sizes, 2 - 25 μm, with mean value of 6.63 μm. Small framboids are still numerous (54%), however the amount of framboids >10 μm increases to 15%. The domination of small framboids with narrow size range in analysed samples, as well as lamination of rocks, suggest

  12. Removal of pyrite and trace elements from waste coal by dissolved-CO{sub 2} flotation and chelating agents. Final technical report, September 1, 1993--August 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Shiao, S.Y. [Babcock and Wilcox Co., New Orleans, LA (United States); Ho, K. [Illinois Clean Coal Inst., Carterville, IL (United States)

    1994-12-31

    The overall objective of this project was to use ultrafine bubbles generated by dissolved C0{sub 2} to recover useable fuel, and reject pyrite and other minerals from a waste coal in flotation. In addition, a chelating agent was used to remove trace metals from the froth products. Illinois No. 6 waste coal obtained from a refuse thickener of a coal cleaning circuit was used as the feed in flotation. The as-received waste coal had a top size of 2400 microns. The waste coal was ground to {minus}75 microns ({minus}200 mesh) and {minus}44 microns ({minus}325 mesh). The as-received and the ground waste coal samples were subjected to flotation. Dissolved-CO{sub 2} flotation tests were performed mainly in a 3-inch diameter by 8 feet high packed column under various test conditions. Some tests were also performed in a 2-inch diameter microbubble column for comparison. The flotation performance of the waste coal in the microbubble column was higher than that for the packed column. The packing in the packed column hindered the coal flotation. The separation efficiency of the ground coal was less than that for the asreceived coal. Flotation of the waste coal was also performed in the packed column using coarser bubbles generated by dispersed C0{sub 2} and air. The separation efficiency of the ground waste coal of 44 microns top size was higher than that for dissolved-CO{sub 2} flotation. Additives were used to modify the waste coal surfaces. Triton-X 100, a nonionic surfactant and EDTA, a chelating agent, increased the separation efficiency of the waste coal.Most of the trace metals in coal were reduced in different degrees by flotation. Triton X-100 or EDTA enhanced removal of chromium, nickel, and selenium. Applying EDTA to the froth products further removed lead significantly.

  13. Geochemistry of metamorphosed basaltic and sedimentary rocks from the Smolník Cu-pyrite deposit (Gemeric Superunit, Western Carpathians: a reappraisal of older geochemical data

    Directory of Open Access Journals (Sweden)

    Peter Ivan

    2016-12-01

    Full Text Available Stratiform chalcopyrite-pyrite deposit of Smolník is located in the low-grade metamorphosed Early Palaeozoic volcano-sedimentary Gelnica Group. Various types of phyllites, mostly sericite and graphite-sericite phyllites with metadolerite bodies build up proximate vicinity of the deposit. The imminent host rocks of sulphide pods are chlorite phyllites with subordinate chlorite-sericite phyllites intercallations. Metadolerites previously interpreted as effusive rocks are probably subvolcanic in origin. Original igneous mineral association of clinopyroxene, plagioclase, ilmenite and probably also olivine were transformed to association of amphiboles, albite, clinozoisite/epidote, titanite ± calcite by metamorphic alteration. Composition of metadolerites is close to basaltic liquids although indices of some fractionation of plagioclase, olivine/chromspinelide or clinopyroxene exist. Trace element distribution points to their similarity to within-plate continental tholeiites (CT and probable relation to the beginning of rifting in the Lower Devonian time. Three possible sources of sedimentary material have been identified in the sedimentary host rocks of the Smolník deposit: (i basalts generated from enriched mantle reservoir; (ii less fractionated calc-alkaline volcanic rocks and (iii fractionated calc-alkaline rhyolites. An additional hydrothermal source for silica and iron is supposed for chlorite phyllites and allows classified them as metaexhalites. The sulphide ores were directly precipitated in the exhalite environment due to reaction hydrothermal solution with hydrogen sulphide produced by thermochemical reduction of the marine sulphate. Geochemical data on metamorphosed dolerites and sediments in combination to other geological characteristics of the Smolník deposit support its classification as the Besshi-type deposit.

  14. Comparison of pretreating pyrite cinder by high pressure roller grinding with damp milling to improve pelletization%高压辊磨和润磨预处理强化硫酸渣球团对比研究

    Institute of Scientific and Technical Information of China (English)

    朱德庆; 陈栋; 潘建

    2011-01-01

    The pretreatment of pyrite cinder was studied using high pressure roll grinding (HPRG), which aims to improve the quality of green pellets and reinforce roasting performance of pyrite cinder pellets, and HPRG was compared with damp milling was made. The results show that both HPRG and damp milling can significantly improve green ball quality while bentonite consumption is dramatically reduced, the drop number of green balls increases from 9.0 times without pretreatment to more than 30.0 times from 0.5 m height by pretreating the pyrite cinder using HPRG and 27.4 times from 0.5 m height by using damp milling, the compressive strength increases from 7.2 N per pellet without pretreatment to 10.6 N per pellet by using HPGR to pretreat cinder and 13.7 N per pellet by using damp milling, respectively. Thermal shock temperature of green balls is above 540 ℃ and the moisture of green pellets drops by 6.5%. After the pyrite cider is pretreated by HPRG and damp milling, the preheating and roasting temperatures of the pyrite cinder pellets are decreased by 150 ℃ and 80 ℃, respectively, and the roasting time is shortened by 6 mines. Therefore, the roasting performance of pyrite cinder pellets is reinforced greatly by HPRG and damp milling. The mechanisms of HPRG and damp milling show that specific surface areas and surface energy and activity are improved, and that solid diffusion reactions are enhanced, resulting in strong bonding inside fired pellets. However, productivity of HPRG is much higher than that of damp milling, and unit energy consumption is lower than that of damp milling.%采用高压辊磨技术预处理硫酸渣改善生球质量和强化球团焙烧,并且与传统的润磨技术进行对比.研究结果表明:高压辊磨和润磨预处理硫酸渣均可大幅度提高生球质量,在膨润土用量大幅降低的同时,生球落下强度从9 0次/(0.5 m)分别增加到大于30.0次/(0.5 m)和27.4次/(0.5 m),抗压强度从7.2 N/个分别增加到10

  15. Mathematical modelling of transport of gaseous and liquid substances induced by pyrite oxidation in spoil banks of lignite mines; Mathematische Modellierung der durch Pyritoxidation induzierten Stofftransporte in Braunkohleabraumkippen in gasfoermiger und fluessiger Phase

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, R.

    2001-07-01

    Pyrite (FeS{sub 2}) oxidation due to open-pit lignite mining activities may result in acid mine drainage and dissolved metals in the soil and ground water of the overburden spoil piles. The pyrite oxidation takes place firstly during the mining process and at the temporary surfaces of the mine, secondly in deep zones of the overburden spoil pile as a result of gas transport through the unsaturated zone. The second process continues after mine closure possibly over several decades and therefore contaminates the environment for a long time. Whereas some studies deal with a minimisation by geochemical means, this research focuses on a minimisation by impacting the physical boundary conditions. Special attention is given to the transport of oxygen from the soil surface to the pyrite oxidation zone. Soil column experiments with columns of 2.90 m height yield experimental data concerning the pyrite oxidation and the related transport processes in the unsaturated zone. Experimental data are compared to simulation results obtained with the model MUSIC; it calculates coupled reaction and transport processes in a one-dimensional soil profile using the finite volume method. Pyrite oxidation is described by means of a first order kinetics, the gas transport takes place by diffusion as well as convection. The transport of solutes in the soil water is described by the convection-dispersion equation (Cl{sup -}, Fe{sup 2+} and SO{sub 4}{sup 2-}). The simulations are able to reproduce the measured time series of oxygen concentrations in the soil profile. (orig.) [German] Die durch Braunkohlegewinnung im Tagebau hervorgerufene Pyritoxidation (Pyrit: FeS{sub 2}) kann zu Versauerung, Schwermetallfreisetzung und Aufmineralisierung des Boden- und Grundwassers in den Abraumkippen fuehren. Die Pyritoxidation findet zum einen waehrend des Abbaubetriebs und an den temporaeren Oberflaechen des Tagebaus statt, zum anderen in tieferen Bereichen der Abraumkippe durch Gastransport durch die

  16. Source and evolution of ore-forming hydrothermal fluids in the northern Iberian Pyrite Belt massive sulphide deposits (SW Spain): evidence from fluid inclusions and stable isotopes

    Science.gov (United States)

    Sánchez-España, Javier; Velasco, Francisco; Boyce, Adrian J.; Fallick, Anthony E.

    2003-08-01

    A fluid inclusion and stable isotopic study has been undertaken on some massive sulphide deposits (Aguas Teñidas Este, Concepción, San Miguel, San Telmo and Cueva de la Mora) located in the northern Iberian Pyrite Belt. The isotopic analyses were mainly performed on quartz, chlorite, carbonate and whole rock samples from the stockworks and altered footwall zones of the deposits, and also on some fluid inclusion waters. Homogenization temperatures of fluid inclusions in quartz mostly range from 120 to 280 °C. Salinity of most fluid inclusions ranges from 2 to 14 wt% NaCl equiv. A few cases with Th=80-110 °C and salinity of 16-24 wt% NaCl equiv., have been also recognized. In addition, fluid inclusions from the Soloviejo Mn-Fe-jaspers (160-190 °C and ≈6 wt% NaCl equiv.) and some Late to Post-Hercynian quartz veins (130-270 °C and ≈4 wt% NaCl equiv.) were also studied. Isotopic results indicate that fluids in equilibrium with measured quartz (δ18Ofluid ≈-2 to 4‰), chlorites (δ18Ofluid ≈8-14‰, δDfluid ≈-45 to -27‰), whole rocks (δ18Ofluid ≈4-7‰, δDfluid ≈-15 to -10‰), and carbonates (δ18Oankerite ≈14.5-16‰, δ13Cfluid =-11 to -5‰) evolved isotopically during the lifetime of the hydrothermal systems, following a waxing/waning cycle at different temperatures and water/rock ratios. The results (fluid inclusions, δ18O, δD and δ13C values) point to a highly evolved seawater, along with a variable (but significant) contribution of other fluid reservoirs such as magmatic and/or deep metamorphic waters, as the most probable sources for the ore-forming fluids. These fluids interacted with the underlying volcanic and sedimentary rocks during convective circulation through the upper crust.

  17. Availability of potentially hazardous elements in soils and their transfer to plants. A case study in polluted soils from the Iberian Pyrite Belt (SW Spain)

    Science.gov (United States)

    Romero-Baena, Antonio; Abreu, Maria Manuela; Santos, Erika S.; Arán, Diego; González, Isabel

    2017-04-01

    Protocols for the study of potentially polluted soils by potentially hazardous elements (PHEs) are based on total element concentration. Nevertheless, the hazard depends on their availability and ability to be uptake and translocated to edible part of the plants and consequently to the food chain. Because the bioavailability of elements depends on several factors, as soil properties and plant species, there is not a universal method for its evaluation. The objectives of this work are: to assess the bioavailability of PHEs using different aqueous solutions for chemical elements extraction from different soils and to evaluate its concentrations in edible part of Lactuca sativa (lettuce) and Petroselinum crispum (parsley). The study has been carried out in four soils polluted by mining activities in Tharsis, Sotiel and Riotinto-Nerva areas (Iberian Pyrite Belt, SW Spain). The soils show high concentration in PHEs (e.g. As 471-1645, Cu 333-1455, Pb 1143-5131, Zn 273-1371 mg/kg). The pH is neutral (7.1-7.9) and the content in organic carbon ranges from 34 to 85 g/kg. For this purpose, experimental work was performed in greenhouse conditions in pots filled with 1.5 kg soil/pot (n=5 per soil). Lettuce and parsley seedlings (11 and 6 cm height, respectively) were transplanted. After six weeks of growth, plants were harvested and soil samples were collected. The availability of PHEs in soils (beginning and end of the assay) has been assessed by extraction with different aqueous solutions: water (24 hours contact); 1 mol/dm3 ammonium acetate (6 hours contact); DTPA (0.005 mol/dm3 diethylenetriaminepentaacetic acid + 0.1 mol/dm3 triethanolamine + 0.01 mol/dm3 calcium chloride; 6 hours contact); and 10 mmol/dm3 of a mixture of low-molecular weight organic acids (acetic, lactic, citric, malic, formic acids; molar ratio 4:2:1:1:1; 16 hours contact; rhizosphere-based method). The availability of As has been assessed by extraction with 0.05 mol/dm3 ammonium monophosphate (16 hours

  18. 某硫铁矿烧渣选铁除砷工艺研究%Study on Iron Recovery and Arsenic Removal to A Pyrite Cinder

    Institute of Scientific and Technical Information of China (English)

    董风芝; 王苹

    2012-01-01

    针对武汉某化工公司的硫铁矿烧渣进行弱磁选富集铁矿物—化学法除砷试验,结果表明:在磨矿细度为-0.038 mm占80%、磁场强度为160 kA/m的条件下弱磁选1次,所得精矿铁品位为61.91%、铁回收率为92.96%、硫含量为0.682%、砷含量为0.381%;弱磁选精矿以盐酸作浸出药剂,在矿浆浓度为40%、酸固比为1∶25、搅拌强度为300 r/min条件下浸出40 min,滤除废酸后用水清洗3次,最终能够制备出铁品位为63.35%、铁回收率为92.88%、硫含量为0.325%、砷含量为0.083%的铁精粉.如何在保证脱砷效果的同时提高硫的脱除率是需要进一步研究的课题.%The processing technology of the pyrite cinder from a chemical plant in Wuhan is that the iron recovered by low intensity magnetic separation and arsenic removed by chemical method. The conditions of low intensity magnetic separation include grinding fineness -0. 038 mm 80% , magnetic field intensity 160 kA/ra, under which the iron concentrate containing Fe 61. 91% , S 0. 682% and As 0. 381% with the iron recovery 92. 96% was obtained by one stage magnetic separation. The conditions of chemical leaching of iron concentrate by hydrochloride include pulp density 40% , ratio of hydrochloride and the solid(iron concentrate) 1:25, the leaching time 40 min, the agitation intensity 300 r/min and washing 3 times after filtering waste acid, under which the iron concentrate assaying Fe 63. 33% , S 0. 325% and As 0.083% with the iron recovery 92. 88% iron grade 63. 35% can be achieved. How to ensure the effectiveness of arsenic removal while increasing the sulfur removal rate is need for further study.

  19. Evaluation of germination, growth and ecophysiological response of Cistus monspeliensis L. in different contaminated and uncontaminated soils of the Iberian Pyrite Belt

    Science.gov (United States)

    Arenas Lago, Daniel; Santos, Erika S.; Carvalho, Luisa C.; Abreu, Maria Manuela

    2016-04-01

    Iberian Pyrite Belt (IPB) is one of the most important volcanogenic massive sulfide ore deposits in the world. As a result of the mine activities, many areas from the IPB have become extreme environments with high concentrations of a wide variety of potentially hazardous elements (PHEs) and low pH in their soils, which cause severe contamination problems and inhibit or reduce the plant colonization and their growth. Nevertheless, Cistus monspeliensis L. grows spontaneously in mine areas from the IPB under these extreme conditions, which suggests that this species must have mechanisms to adapt and defend itself against oxidative stress caused by the high levels of PHEs. The main objectives of this study are to evaluate germination, growth, development and ecophysiological behaviour of C. monspeliensis in different contaminated and uncontaminated soils. For this purpose, two different assays were conducted in potted plants in a greenhouse with C. monspeliensis seeds collected in the São Domingos mine area (SE Portugal, IPB). In the first assay, twenty C. monspeliensis seeds were sowed to evaluate the germination in pots (n=4) with five different contaminated and uncontaminated soils - Uncontaminated soils: a sandy soil (A) and a soil from Caldeirão (C) (S of Portugal), Contaminated soils: two gossans from São Domingos mine (SD and G) and a gossan amended with an organic corrective (GC). After one month, germination rate was evaluated. Total and available multielemental concentrations were determined in the soils. In the second assay, C. monspeliensis seedlings were planted in the contaminated soil GC and in the uncontaminated soil C. After three months of growth, plants were harvested and shoots were separated from roots. Plant height, fresh biomass and multielemental concentration in shoots were quantified. Pigments (chlorophylls, anthocyanins and carotenoids), glutathione, ascorbate, H2O2 and the activities of several key antioxidative enzymes were also

  20. Use of hard coal tailings for landfill construction with particular consideration to pyrite decay and to suitability of tailings as a geochemical barrier; Die Verwendung von Steinkohlebergematerialien im Deponiebau im Hinblick auf die Pyritverwitterung und die Eignung als geochemische Barriere

    Energy Technology Data Exchange (ETDEWEB)

    Schuering, J.

    1996-10-01

    The purpose of the present paper was to determine the hazard potential of acid formation during oxidation of the pyrite naturally contained in hard coal tailings and the efficacy of such tailings as a barrier against pollutants. The results were intended to show to what extent tailings can be recycled as a valuable material. This would not only offer an alternative to the land-consuming practice of dumping, which upon exhaustion of buffering capacity also gives rise to the problems associated with acid pit water, but would also allow the conservation of natural resources otherwise consumed in the sealing of landfills. (orig./HS) [Deutsch] Ziel dieser Arbeit war zum einen die Erfassung des Gefaehrdungspotentials durch die Saeurebildung bei der Oxidation des geogen im Bergmaterial enthaltenen Pyrits und zum anderen die Wirksamkeit als Barriere gegenueber Schadstoffen. Die Ergebnisse sollten aufzeigen, inwieweit das Bergematerial als Werkstoff eine weitere Verwendung finden kann. Von Bedeutung ist dabei nicht nur die Alternative zur flaechenintensiven Aufhaldung und den, bei Erschoepfung der Pufferkapazitaet, unter Umstaenden verbundenen Problemen bei der Bildung Saurer Grubenwaesser, sondern auch die Schonung natuerlicher Ressourcen bei der Verwendung in Deponieabdichtungen. (orig./HS)

  1. Experimental study on comprehensive utilization of Au -Ag -Cu polymetallic pyrite cinders%金银铜多金属黄铁矿烧渣综合回收试验研究

    Institute of Scientific and Technical Information of China (English)

    库建刚

    2012-01-01

    Based on the physical and chemical characteristics of the pyrite cinders, experimental study on comprehensive recovery of pyrite cinders are carried out. The results of the tests indicate that pyrite cinders are mainly comprised of ferric oxide and abundant with gold, silver, copper and zinc. A part of gold, silver and copper is included in sulfide such as pyrite and zinc is mainly existed in zinc fer-rite. Under the condition of alkaline slurry which pH value is ranged between 10 and 11, pulp density 35% , original pyrite cinders is cyanide leached for 24 h with sodium cyanide consumption is 6 kg·t-1, are the leaching rate of gold and silver reaches 67.25% and 60.08%. The grade of gold and silver in concentrate is 8.66 g·t-1 and 100.31 g·t-1 with the recovery 37.82% and 20.26%. The cy-aniding leaching rate of gold and silver of flotation tailing reaches 96.85% and 70.08%.%根据黄铁矿烧渣的物理、化学性质特征,完成了多金属综合回收试验.结果表明:烧渣组成以氧化铁为主,并含有贵金属及有色金属,部分金、银、铜包裹于黄铁矿等硫化物中,而锌主要以铁酸锌形式存在.对烧渣进行氰化浸出,在试样未磨情况下,采用石灰调节矿浆pH =10 ~11、矿浆浓度35%、浸出时间24h、氰化钠耗量6kg·t-1的试验条件,可以获得金、银浸出率分别为67.25%、60.08%;采用浮选法处理烧渣可获得金品位8.66g· t-1、回收率为37.82%的浮选产品,其中银品位和回收率分别为100.3 g·t-1、20.26%;对浮选尾矿直接进行氰化浸出,可获得金、银浸出率分别为96.85%、70.08%.

  2. Estudo da dissolução oxidativa microbiológica de uma complexa amostra mineral contendo pirita (FeS2, Pirrotita (Fe1-xS e Molibdenita (MoS2 Microbiological oxidative dissolution of a complex mineral sample containing pyrite (FeS2, pyrrotite (Fe1-xS and molybdenite (MoS2

    Directory of Open Access Journals (Sweden)

    Wilmo E. Francisco Jr

    2007-10-01

    Full Text Available This work aims to study the oxidation of a complex molybdenite mineral which contains pyrite and pyrrotite, by Acidithiobacillus ferrooxidans. This study was performed by respirometric essays and bioleaching in shake flasks. Respirometric essays yielded the kinetics of mineral oxidation. The findings showed that sulfide oxidation followed classical Michaelis-Menten kinetics. Bioleaching in shake flasks allowed evaluation of chemical and mineralogical changes resulting from sulfide oxidation. The results demonstrated that pyrrotite and pyrite were completely oxidized in A. ferrooxidans cultures whereas molybdenite was not consumed. These data indicated that molybdenite was the most recalcitrant sulfide in the sample.

  3. Massive sulfide exploration models of the Iberian Pyrite Belt Neves Corvo mine region, based in a 3D geological, geophysical and geochemical ProMine study

    Science.gov (United States)

    Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Mário Castelo-Branco, José; Granado, Isabel; Carvalho, João; João Baptista, Maria; Represas, Patrícia; Pereira, Zélia; Oliveira, Tomás; Araujo, Vitor

    2013-04-01

    The Iberian Pyrite Belt (IPB) hosts one of the largest concentrations of massive sulfides in the Earth's crust. This highly productive VMS belt contains more than 85 massive sulfide deposits, totalling an estimate of 1600 Mt of massive ore and about 250 Mt of stockwork ore (Leistel et al., 1998; Oliveira et al., 2005; Tornos, 2006). Included in the South Portuguese Zone the IPB is represented by the Phyllite-Quartzite Group (PQG) composed of shales and quartzites of late Devonian age followed by the Volcanic-Sedimentary Complex (VSC) a submarine succession of sediments and felsic and basic volcanic rocks (late Famennian-late Viséan age). Above the IPB a turbidite sedimentary unit occurs being represented by the Baixo Alentejo Flysch Group (BAFG). The ore deposits are hosted by felsic volcanic rocks and sediments that are dominant in the lower part of the VSC succession. The Neves Corvo (ProMine, EU FP7) project area is focused on the Neves Corvo deposit, an active copper mine. The project area is located between the Messejana Fault and the Portuguese/Spanish border which has been selected for the 3D geological and geophysical modelling study, based on high exploration potential of the Neves Corvo area (Oliveira et al. 2006, Relvas et al. 2006, Pereira et al. 2008, Rosa et al. 2008, Matos et al. 2011, Oliveira et al. 2013). In this study existing LNEG and AGC geological, geophysical and geochemistry databases were considered. New surveys were done: i) - A physical volcanology and palynostratigraphic age data study and log of the Cotovio drill-hole core (1,888 m, drilled by AGC). ii) - Interpretation of 280 km of Squid TEM performed by AGC. Based on the TEM data, significant conductors have been identified related with: shallow conductive cover, graphitic shale, black shale and sulphide mineralizations. The most important TEM conductors are related with the Neves Corvo massive sulphides lenses (1-10 Ωm). iii) - Ground and residual gravimetry studies including

  4. A ground electromagnetic survey used to map sulfides and acid sulfate ground waters at the abandoned Cabin Branch Mine, Prince William Forest Park, northern Virginia gold-pyrite belt

    Science.gov (United States)

    Wynn, Jeffrey C.

    2000-01-01

    INTRODUCTION AND BACKGROUND: Prince William Forest Park is situated at the northeastern end of the Virginia Gold-Pyrite belt northwest of the town of Dumfries, VA. The U. S. Marine Corps Reservation at Quantico borders the park on the west and south, and occupies part of the same watershed. Two abandoned mines are found within the park: the Cabin Branch pyrite mine, a historic source of acid mine drainage, and the Greenwood gold mine, a source of mercury contamination. Both are within the watershed of Quantico Creek (Fig.1). The Cabin Branch mine (also known as the Dumfries mine) lies about 2.4 km northwest of the town of Dumfries. It exploited a 300 meter-long, lens-shaped body of massive sulfide ore hosted by metamorphosed volcanic rocks; during its history over 200,000 tons of ore were extracted and processed locally. The site became part of the National Capitol Region of the National Park Service in 1940 and is currently managed by the National Park Service. In 1995 the National Park Service, in cooperation with the Virginia Department of Mines, Minerals, and Energy reclaimed the Cabin Branch site. The Virginia Gold-Pyrite belt, also known as the central Virginia volcanic-plutonic belt, is host to numerous abandoned metal mines (Pavlides and others, 1982), including the Cabin Branch deposit. The belt itself extends from its northern terminus near Cabin Branch, about 50 km south of Washington, D.C., approximately 175 km to the southwest into central Virginia. It is underlain by metamorphosed volcanic and clastic (non-carbonate) sedimentary rocks, originally deposited approximately 460 million years ago during the Ordovician Period (Horton and others, 1998). Three kinds of deposits are found in the belt: volcanic-associated massive sulfide deposits, low-sulfide quartz-gold vein deposits, and gold placer deposits. The massive sulfide deposits such as Cabin Branch were historically mined for their sulfur, copper, zinc, and lead contents, but also yielded byproduct

  5. 辽西北票二道沟金矿的成矿特点和黄铁矿热电性特征%Ore-forming Characteristics and Pyroelectricity of Pyrite of the Erdaogou Gold Deposit, Beipiao, Western Liaoning

    Institute of Scientific and Technical Information of China (English)

    王鹏; 董国臣; 李志国; 聂飞; 陈友长; 孙凡; 王霞; 董美玲

    2013-01-01

    通过对辽西北票二道沟金矿Ⅲ号脉的不同中段的矿石组构、金的分布特点和主要载金矿物立方体、五角十二面体及它形黄铁矿的热电性研究,讨论了成矿特征,计算了成矿温度和矿体剥蚀率并对深部找矿远景进行了预测.研究表明:二道沟金矿金的分布特点存在不均匀性;黄铁矿热电性以P型为主且变化范围宽,只有少量的N型,表明矿体的剥蚀率较低.二道沟金矿可能存在多期次的热液活动,且每一期次相互叠加改造;成矿热液来自南东方向,成矿热液早期温度较高,金属元素大量沉淀温度为150 ~300℃,属中低温,且不同中段的成矿温度有一定的变化规律.不同晶形的黄铁矿热电性研究表明,不同晶形载金能力不同,黄铁矿热电性P型频率不同,形成的温度不同,但计算的矿体剥蚀率相差不大.%According to the ore texture, gold occurrence, shape and pyroelectricity of pyrites of vein Ⅲ in the Erdaogou gold deposit in Western Liaoning, the authors discussed the ore-forming temperatures, denudation rates and evaluated the ore deep prospects. The studies prove that the gold occurrence in the ores was unhomo-geneous. The pyrite was mainly P-type and varied widely, with a few N-type, in terms of pyroelectricity, which indicated that a few part of the orebody was removed by uplift and erosion. Possibly, there were several hydro-thermal activities superposed each other in the Erdaogou gold deposit. The metallogenic hydrothermal solution came from southeast direction. Though the initial hydrothermal temperature was high, most metal minerals precipitated when the temperature ranged from 150 to 300 ℃ , indicating that the Erdaogou gold deposit belonged low-medium hydrothermal type. The pyroelectricity measurements of pyrite indicated that denudation rate was similar, even though the pyrites were different in frequency of P-type, forming temperature and gold content.

  6. 金矿床中金与黄铁矿和毒砂的关系%Hydrothermal evolution of gold-bearing pyrite and arsenopyrite from different types of gold deposits

    Institute of Scientific and Technical Information of China (English)

    卢焕章; 朱笑青; 单强; 王中刚

    2013-01-01

    卡林型金矿中的金,以肉眼,甚至在显微镜下都看不到,因而称之为“不可见金”.经过金的物相分析,发现Au与毒砂、黄铁矿有关.进一步的问题是:Au在毒砂、黄铁矿中呈何状态分布,是呈微细的独立矿物?还是类质同象?是以化学键进入毒砂、黄铁矿的晶格?还是吸附在其表面?进一步的研究表明,世界上其他类型金矿,如浊积岩型金矿、造山带内太古代绿岩带金矿、变质金矿、与火成岩有关的金矿,甚至含金的块状硫化物矿床,其中的金除了以自然金(可见金)产出外,在黄铁矿、毒砂、辉锑矿、雄黄等硫化物中还含有不可见金.从不可见金到可见金,需经过热液蚀变作用,在高As条件下,温度和硫逸度的升高,可溶出不可见金,在温度下降和还原条件下,Au以可见金形式存在于蚀变环带中.这种从不可见金到可见金的转换过程,反映了Au、As、S以及Fe等元素的地球化学特征.金矿中的黄铁矿和毒砂具有相似的结构,包括在其原始生长的晶体中含有不可见金,并且在稍后的成矿阶段内形成赋存有可见金的蚀变环带.蚀变环带以As含量高为特征,并且,后期的可见金是沿裂隙或毒砂与黄铁矿的粒间分布.可见金是热液活化了矿物内的不可见金而形成的.%This study investigates the microstructures,geochemistry,and hydrothermal evolution of gold-bearing pyrite and arsenopyrite from Carlin type (both in the USA and China),turbidite hosted gold deposits of China,intrusion related gold deposits,epithermal gold deposits and six orogenic gold deposits in the Archean Eastern Goldfields Province,Western Australia.Scanning electron microscope (SEM),EPMA,and LA-ICP-MS analyses show that the gold-bearing pyrite and arsenopyrite possess a number of similar textural features,including the occurrence of invisible gold within initial phases of growth,and later-stage visible gold associated with alteration rims

  7. Oceanic anoxia during the Late Permian: Evidence from pyrite morphology%二叠纪末期海洋缺氧:来自黄铁矿形态的证据

    Institute of Scientific and Technical Information of China (English)

    遇昊; 陈代钊; 韦恒叶; 汪建国; 常华进

    2011-01-01

    晚二叠世是古生代环境和生物演化的重要时期,也是重要的"冰室气候"时期,但其中仍然含有大量的富有机质沉积,并发育成为我国南方扬子板块重要的烃源岩层位.为恢复这一时期古海洋氧化还原状态,我们对湖北恩施赵家坝剖面大隆组硅质岩和四川广元上寺长江沟剖面大隆组碳酸盐岩中草莓状黄铁矿的粒径大小和分布进行了测量、统计和研究.统计结果显示,这些硅质岩和灰岩样品中的草莓状黄铁矿基本为原生,少见自行晶和后期充填,具有如下特点:单体粒径普遍偏小,变化范围相当狭窄,大多数草莓状黄铁矿粒径小于5μm,80%以上的粒径小于7.7μm.这些粒径特征和分布特点表明,我国南方记录的晚二叠世大隆组烃源岩沉积于台内盆地极度缺氧(甚至硫化)的海洋环境,有利于有机质的保存.另外,该时期的极度缺氧为晚二叠世-早三叠世之交的大规模生物灭绝拉开了序幕.%Late Permian is an important stage marked by vast environmental and biological changes in the Paleozoic. Although an "Ice-House climate" predominated over the period, organic-rich sediments,which are served as important source rocks, were deposited extensively in intraplatform basins on Yangtze block, South China. In order to reconstruct the paleoredox conditions of the Yangtze sea during this period, we measured framboid size of pyrite in cherts and siliceous carbonates of Dalong Formation at Zhaojiaba section, Hubei province, and Changjianggou section,Sichuan province, respectively. Our data indicate that pyrite framboids in the cherts and carbonates are mostly of primary origin, although minor idiotopic crystals showing post-depositional transformation are observed. Pyrite framboids generally vary in a very narrow range in size,mostly smaller than 5 μm,and over 80% of which are smaller than 7.7 μm. These suggest that, during the Late Permian, the organic-rich sediments were

  8. Improve sulfur concentrate quality and realize double resource utilization of pyrite%提高硫精矿质量实现硫铁双资源利用的研究

    Institute of Scientific and Technical Information of China (English)

    叶雪均; 刘子帅

    2013-01-01

    提出了通过选矿技术提高硫精矿质量,可解决烧渣利用率低的问题,因此针对不同种类的黄铁矿进行了提高硫精矿质量的工艺研究.研究表明,不同种类的矿石经合理的选矿工艺都可获得高质量的硫精矿.铜硫矿石可获得硫精矿品位48.85%,含砷0.178%,硫回收率达89.86%;硫金矿石获得了硫精矿含硫48.41%,含砷0.38%,硫作业回收率82.00%;多金属硫化矿闭路结果可获得硫精矿硫品位为48.94%,含砷为0.44%,回收率为55.30%的良好指标.可研分析表明,当硫精矿品位≥45%时,焙烧所得硫酸烧渣铁含量达60%以上,直接作为铁精粉利用,实现无烧渣排放,也实现了硫铁双资源的利用.%The paper put forword to improving sulfur concentrate quality through the processing technology , and solve the problem of the utilization rate of poor cinder. Different types of pyrites are studied to improve the quality of sulfur concentrate for flotation. It is found that for the different types of ore, if choose a reasonable flowsheet and pharmaceutical systems, we can get the surfure concentrate of high quality. Copper sulfur ore can obtain sulphur concentrate grade 48. 85% , 0. 178% arsenic, and sulfur recovery rate of 89.86% ; Sulfur gold ore get sulfur concentrate grade of S 48.41% , As 0. 38% , and sulfur operating recovery 82.0% ; Many metal sulfide ore concentrate can obtain the closed-circuit sulfur sulfur grade of 48. 94% , As 0. 44% , and recovery rate is 55. 30%. Feasibility analysis shows that when sulphur concentrate grade exceed 45% , roasting the sulfuric acid slag iron burn content of 60% a-bove, and directly as iron essence pink use, achieving the possibility of not burn slag discharge and the double use of pyrite resources.

  9. Analysis of iron- and sulfur-oxidizing bacteria in a treatment plant of acid rock drainage from a Japanese pyrite mine by use of ribulose-1, 5-bisphosphate carboxylase/oxygenase large-subunit gene.

    Science.gov (United States)

    Kamimura, Kazuo; Okabayashi, Ai; Kikumoto, Mei; Manchur, Mohammed Abul; Wakai, Satoshi; Kanao, Tadayoshi

    2010-03-01

    Iron- and sulfur-oxidizing bacteria in a treatment plant of acid rock drainage (ARD) from a pyrite mine in Yanahara, Okayama prefecture, Japan, were analyzed using the gene (cbbL) encoding the large subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RubisCO). Analyses of partial sequences of cbbL genes from Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidithiobacillus caldus strains revealed the diversity in their cbbL gene sequences. In contrast to the presence of two copies of form I cbbL genes (cbbL1 and cbbL2) in A. ferrooxidans genome, A. thiooxidans and A. caldus had a single copy of form I cbbL gene in their genomes. A phylogenetic analysis based on deduced amino acid sequences from cbbL genes detected in the ARD treatment plant and their close relatives revealed that 89% of the total clones were affiliated with A. ferrooxidans. Clones loosely affiliated with the cbbL from A. thiooxidans NB1-3 or Thiobacillus denitrificans was also detected in the treatment plant. cbbL gene sequences of iron- or sulfur-oxidizing bacteria isolated from the ARD and the ARD treatment plant were not detected in the cbbL libraries from the treatment plant, suggesting the low frequencies of isolates in the samples. Copyright 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  10. STUDY ON MICROWAVE PRETREATMENT OF REFRACTORY MICRODIMENSIONAL GOLD PACKAGED BY PYRITE IN GOLD ORES%微波处理难浸微细粒包裹金的试验研究

    Institute of Scientific and Technical Information of China (English)

    魏明安; 张锐敏

    2001-01-01

    利用微波的加热特性,通过条件试验确定,在450℃用微波处理5min,可使某金矿的金精矿氰化浸出率由74%提高到90%以上,使现场金精矿氰化渣的氰化浸出率达到86%以上。试验结果表明,微波预处理对于打开黄铁矿包裹金的前景光明。%By using the heating feature of microwave, it has shown from condition tests that the gold leaching recovery can be improved from 74% to more than 90% if the gold concentrates is treated for 5 minutes in a microwave oven at 450℃. Therefore, the gold leaching recovery of cyanide residue of more than 86% can be obtained in leaching plant. The results indicate that microwave pretreatment to packaged gold by pyrite in gold ores has a glory prospect.

  11. 3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    Science.gov (United States)

    Kampmann, Tobias C.; Stephens, Michael B.; Weihed, Pär

    2016-06-01

    Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the south-western part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D1 and D2) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D1 and D2, and even after D2. F2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone- to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

  12. 浙江台州湾潮间带沉积物痕量金属形态及其黄铁矿矿化程度%Trace Metal Occurence in Sediments and Its Bearing on Pyritization from Taizhou Bay, Zhejiang

    Institute of Scientific and Technical Information of China (English)

    叶思源; 丁喜桂; 袁红明; 赵广明; 王锦

    2011-01-01

    Three undisturbed samples were collected in intertidal zone in the Taizhou Bay of Zhejiang Province, China. Reactive and pyrite fractions of trace metals in the sediments were obtained using sequential extraction method, meanwhile, acid volatile sulfide (AVS) was measured by cold diffusion method. The results indicated that the degree of pyritization (DOP) of trace metals in the study area was low and trace metals were very active and liable to take part in biogeochemical cycle, but elements differed greatly in degree of trace metal pyritization (DTMP) : As and Hg underwent most significant pyritization, Cu, Zn, Cd, Cr, and Ni moderately, and Pb and Mri the least. Factors that controlled the degrees of pyritization depended upon whether there was abundant organic carbon (OrgC) and AVS in the sediments and also upon the presence of an anoxic reducing system. Concentrations of the reactive trace metals were not a limiting factor in the present study.%在浙江椒江口潮间带采集了3个未扰动沉积物柱状样,并采用分级提取方法获得了沉积物各痕量金属的活性态和黄铁矿态分量,同时采用冷扩散法测试了酸可挥发性硫化物(AVS).结果表明:研究区痕量金属黄铁矿矿化程度(DOP)较低,痕量金属存在较大的活性,容易参与水生系统的生物地球化学循环;但各元素的痕量金属黄铁矿矿化度(DTMP)存在较大差别,即元素As和Hg的DTMP值最大,Cu、Zn、Cd、Cr和Ni中等,Pb和Mn最小.控制黄铁矿矿化程度的因素包括沉积物是否存在大量的有机碳(OrgC)、AVS以及是否存在隔氧的还原系统.

  13. Thermoelectric characteristics of pyrite from the main ore zone of the Huachanggou gold deposit, Shaanxi Province and its significance%陕西省铧厂沟金矿床主矿带黄铁矿热电性特征及其地质意义

    Institute of Scientific and Technical Information of China (English)

    刘冲昊; 刘家军; 王建平; 吴杰; 王维钰; 王立新; 于康伟; 陈冬; 李志国

    2013-01-01

    陕西省铧厂沟金矿是一个主要赋存于海底基性火山喷流细碧岩中的金矿床.文中系统研究了该矿床主矿带黄铁矿的热电性特征.主矿带成矿温度主要集中在130~330℃,属中—低温矿床;黄铁矿导电类型从早期到晚期由N型向P型转变;P型黄铁矿出现频率从浅部到深部呈减小趋势;金品位高值区与P型黄铁矿的高值区及热电系数离散度的低值区相对应;主矿带黄铁矿热电导型及热电性参数特征反映出主矿带开采区位于矿体中部偏下,向深处仍有一定规模的延伸.综合分析认为,0至2勘探线深部以及22~26勘探线深部发现新的富矿段的可能性较大.%The Huachanggou gold deposit in Shaanxi Province mainly occurs in the submarine basic volcanic effusive spilite.On the basis of a study of the thermoelectric characteristics of pyrite,the authors put forward the following conclusions.The main ore zone is a low-medium temperature gold deposit,whose pyrite crystallization temperature is in the range of 130-330 ℃.The electric conduct assemblage type of the pyrite changes in the order of N-type to P-type from the early stage to the late stage.The frequence of P-type pyrites gradually decreases from the shallow part to the deep.The high average gold grade corresponds to the high frequence of P-type pyrites and low value of thermoelectrical coefficient dispersions.The characteristics of thermoelectricity imply that the lower to middle parts of the ore body have been exhumed until now,and there exists an extension of the main ore zone in the deep.Furthermore,the authors suggest that the better exploring prospect would be expectable in the depth of exploration line Nos.0,2 and Nos.22-26.

  14. 某硫铁矿矿泥柱浮选半工业试验%Pilot Test of a Pyrite Slime Flotation by Cyclone-Static Micro-bubble Flotation Column

    Institute of Scientific and Technical Information of China (English)

    黄根; 岳双凌; 文涵睿

    2012-01-01

    order to effectively utilize the slime produced in the course of producing - 3 mm production in a pyrite concentrator from Guangdong province,carried out the pilot test of once roughing once cleaning column flotation by two Φ400 mm ×4 000 mm cyclone static micro-bubble flotation columns. Suitable handling capacity,reagent system and circu-lating pump pressure of flotation column were determined by conditions test After 72 h continous production,the S concentrate with 48. 46% grade,93. 71% recovery was achineved,comparing to the spot flotation machine,the S recovery increased by 13 percentage ponits.%为使广东某硫铁矿生产-3 mm产品过程中产生的矿泥得到高效利用,采用2台Φ400 mm×4 000 mm旋流-静态微泡浮选柱在现场对该矿泥进行了1粗1精柱式浮选半工业试验.首先通过条件试验确定了合适的处理量、药剂制度以及浮选柱中矿循环泵压力,然后进行72 h连续运转,获得了硫精矿硫品位为48.46%、硫回收率为93.71%的良好指标.与现场采用浮选机的选别指标相比,硫回收率提高了约13个百分点.

  15. Acid drainages of the pyritic sterile from the Pocos de Caldas uranium mine: environmental interpretation and implications; Drenagens acidas do esteril piritoso da mina de uranio de Pocos de Caldas: interpretacao e implicacoes ambientais

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Vicente Paulo de

    1995-12-01

    Considering the planned closure of the first uranium mine and milling plant operating in Brazil, located in the Pocos de Caldas Plateau, in the State of Minas Gerais, in the next two years, there is the need to obtain basic information for its decommissioning. Special attention has been directed to the following critical areas: open pit, tailing, dam and waste rock piles, because these are the main sources of acid drainage generation. These waters cannot be allowed to flow in the external environment because in addition to sulphuric acid, there is a number of elements in concentration above those allowed by regulations. Among the waste piles (bota-foras BF) two of them BF-4 and BF-8, are in a process of acid generation, thus requiring more attention. The objective of this work was to simulate at the laboratory scale the oxidation and the reduction zones of BF-4. The experiments were conducted in acrylic columns, where the waste sample was kept under aerated and saturated conditions, in different columns. The control of the chemical (solubilized chemical species), physico-chemical (redox potential, pH, conductivity) and biological (bacterial activity) parameters has been carried out on the acid solutions generated by the chemical and biological reactions that occur at the waste. Although the results refer to a four month period, some relevant points can be highlighted, which will serve as a basis for further research. The mineralogical characterization identified the existence of other sulphides associated to pyrite with lower oxidation potential than the latter. The results obtained with the biological characterization for the two conditions studied revealed that the bacterial activity is more intense in the region in contact with air, than in saturated region. (author) 30 refs., 29 figs., 8 tabs.

  16. Producción de Ácido Sulfúrico por Medio del Tratamiento de Gases Residuales Generados en la Tostación de Piritas Production of Sulphuric Acid by Treatment of Residual Gases Generated by Pyrite Roasting

    Directory of Open Access Journals (Sweden)

    Sergio Rosas

    2007-01-01

    Full Text Available Se presenta el estudio técnico-económico para la obtención de ácido sulfúrico por medio del proceso de contacto doble. Con base en las características de los gases residuales generados por la tostación de piritas se selecciona la tecnología de limpieza del efluente y el proceso de producción de ácido sulfúrico. Para la limpieza de los gases se establece utilizar un tren de separación conformado por un separador ciclónico, un lavador Venturi, un eliminador de neblina y dos precipitadores electrostáticos de neblina ácida. Además, para la síntesis de trióxido de azufre se diseña un convertidor catalítico de cuatro camas. Finalmente, se presentan la estimación de los costos de capital y la factibilidad económica para dos concentraciones de producto.A technical-economical study of the sulphuric acid production by the double-contact process is presented. Based on the characteristics of the residual gases produced by pyrite roasting the effluent cleaning technology and the sulphuric acid production process were selected. To clean out the gaseous effluent a separation train that consists in a cyclone separator, a Venturi washer, a mist eliminator, and two electrostatic precipitators were considered. Also, for the sulphur trioxide synthesis a four-bed catalytic converter was designed. Finally, the capital cost estimation and the economic feasibility for two product concentrations are presented.

  17. Expanded halogen-bonded anion organic networks with star-shaped iodoethynyl-substituted molecules: from corrugated 2D hexagonal lattices to pyrite-type 2-fold interpenetrated cubic lattices.

    Science.gov (United States)

    Lieffrig, Julien; Jeannin, Olivier; Fourmigué, Marc

    2013-04-24

    Halogen bonding interactions between halide anions and neutral polyiodinated linkers are used for the elaboration of anion organic frameworks, by analogy with well-known MOF derivatives. The extended, 3-fold symmetry, 1,3,5-tris(iodoethynyl)-2,4,6-trifluorobenzene (1) cocrystallizes with a variety of halide salts, namely, Et3S(+)I(-), Et3MeN(+)I(-), Et4N(+)Br(-), Et3BuN(+)Br(-), Me-DABCO(+)I(-), Bu3S(+)I(-), Bu4N(+)Br(-), Ph3S(+)Br(-), Ph4P(+)Br(-), and PPN(+)Br(-). Salts with 1:1 stoichiometry formulated as (1)·(C(+),X(-)) show recurrent formation of corrugated (6,3) networks, with the large cavities thus generated, filled either by the cations and solvent (CHCl3) molecules and/or by interpenetration (up to 4-fold interpenetration). The 2:1 salt formulated as (1)2·(Et3BuN(+)Br(-)) crystallizes in the cubic Ia3 space group (a = 22.573(5) Å, V = 11502(4) Å(3)), with the Br(-) ion located on 3 site and molecule 1 on a 3-fold axis. The 6-fold, unprecedented octahedral coordination of the bromide anion generates an hexagonal three-dimensional network of Pa3 symmetry, as observed in the pyrite model structure, at variance with the usual, but lower-symmetry, rutile-type topology. In this complex system, the I centering gives rise to a 2-fold interpenetration of class Ia, while the cations and solvent molecules are found disordered within interconnected cavities. Another related cubic structure of comparable unit cell volume (space group Pa3̅, a = 22.4310(15) Å, V = 11286.2(13) Å(3)) is found with (1)2·(Et3S(+)I(-)).

  18. He-Ar isotopic system of fluid inclusions in pyrite from the molybdenum deposits in south margin of North China Block and its trace to metallogenetic and geodynamic background

    Institute of Scientific and Technical Information of China (English)

    ZHU LaiMin; ZHANG GuoWei; GUO Bo; LEE Ben

    2009-01-01

    The helium and argon isotopic compositions of the ore-forming fluids from the molybdenum deposits such as Jinduicheng, Donggou, Shijiawan, and Sandaozhuang, which are located in the East Qinling molybdenum belt in south margin of North China Block (SMCNB), are reported in this paper. The origin and the evolution of the ore-forming fluids and their coupled-relationships with the intra-continental collision and orogenic process of Qinling Orogen in Mesozoic-Cenozoic have been discussed. The 3He/4He and 40Ar/36Ar values (3He/4He=1.38-3.64 Ra, and 40Ar/36Ar=295.68-346.39, respectively) of the fluid inclusions in pyrite from the molybdenum deposits in East Qinling suggest that, the ore-forming fluid system is mixed by two end members. One is the high temperature deep-derived fluid congenetic with the porphyries generated by crust-mantle mixing, and the other is the low-temperature meteoric water which is rich in crustal radiogenic He with the component of atmospheric Ar. From the Pb isotopic composition, and ore-bearing potential of the porphyry and the regional stratum, we can conclude that the ore-forming materials of the deposits in the East Qinling molybdenum belt are derived from the deep source by the mixing of lower crust and upper mantle. Therefore, the formation of the molybdenum deposits in SMNCB can be related to the crust-mantle interaction, which is accompanied by the intra-continental orogenic and extension process in the post-collision period of Qinling Orogen. The granitic porphyries which are related to Mo mineralization are not simple crust-remelting type granites or S type granites, but belong to syntexis-type or mantle-derived granites, hence their formation has a profound and regional geodynamic background.

  19. 胶东杜家崖金矿黄铁矿热电系数、热电阻率与金矿化关系研究%A Study on Correlations of Thermoelectric Coefficient, Thermal Resistance Rate of Pyrite and Golden Mineralization in the Dujiaya Gold Deposit, East Shandong Province

    Institute of Scientific and Technical Information of China (English)

    庞阿娟; 李胜荣; 王潇; 刑金蕊

    2012-01-01

    Different from other types (quartz vein, alteration and broken breccia) of gold deposits in the Shandong Province, the Dujiaya gold deposit, which has been studied very little, is an interlayer gliding alteration type deposit. It hopes that the study of the thermoelectricity of pyrite can provide evidence for deep exploration. 1692 pyrite grains from 37 ore samples of the I orehody were analyzed by BHTE-06 type thermoelectric instrument and 1900 pyrite grains from 38 ore samples of the I orebody were analyzed by BHMR-08 type impedance analyzer. The calculation on the basis of the measured thermoelectric coefficients indicated that the pyrite crystallization temperatures are in the range of 74. 3 - 387. 5°C and mostly in the range of 141. 3 - 343. 4°C. Based on the map of thermoelectric coefficient and thermal resistance rate, this study predicts that locations of -100 meter below the 36~38 and 54 prospecting lines may contain high grade gold ore and have good perspective of mineralization.%杜家崖金矿为层间滑脱蚀变岩型金矿,不同于山东蚀变岩型、石英脉型及破碎角砾岩型金矿.前人对该矿床的研究极少,因此,希望通过对该矿床矿石中黄铁矿热电性的研究,可以为深部找矿提供依据.利用BHTE-06热电系数测试仪对Ⅰ号矿体37件矿石样品中1692粒黄铁矿进行了热电系数分析,并用BHMR- 08型半导体矿粒调温电阻测试分析仪测出了38件矿石样品中1900粒黄铁矿的热电阻率.根据所得热电性系数数据计算出该矿床的黄铁矿形成温度范围为78.6~380.8℃,主要集中在141.3~350.9℃.据所得数据进行黄铁矿热电系数及热电阻率填图,可推测36~38、54勘探线海拔-100m以下附近的区域可能为富矿段,成矿远景较好.

  20. The Waste - heat Recovery and Equipment Selection of the 200kt/a - Output Plant of the Sulfuric Acid by Pyrite Roasting%年产20万t硫铁矿制酸装置的余热回收和相关设备选型

    Institute of Scientific and Technical Information of China (English)

    陈雄

    2011-01-01

    介绍了200kt/a硫铁矿制酸的余热回收和利用,主要分为高温、中温、低温余热,并介绍了相应的设备选型过程。%The waste- heat recovery of the 200kt/a- output plant of the sulfuric acid by pyrite roasting was introduced, including high temperature waste- heat, middle temperature waste- heat, low temperature waste - heat. And the process of equipment selection was also mentioned.

  1. 高岭石型硫铁矿烧渣破碎粒度与解离度及磁选效果研究%Study on the Relation of Liberation Degree and Magnetic Separation Effect with Crushing Size of Kaolinite-type Pyrite Cinder

    Institute of Scientific and Technical Information of China (English)

    黄利; 白怡; 冯启明; 黄阳

    2012-01-01

    This paper has made a research about liberation degree of metakaolin and magnetite and the effect of magnetic separation under the different particle size of kaolinite-pyrite cinder to make effective use of metakaolin and iron mineral in kaolinite-type pyrite cinder. The results show that the liberation degree of magnetite and metakaolin is up to 99% when the kaolinite-type pyrite cinder was crushed to 140~160 mesh. Yields of magnetite concentrate reach to 36.00%, the iron grade of which is 59.32% and the iron recovery of which is 89.00% after the magnetic separation, yields and iron content of metakaolin decreased gradually by the decrease of broken particle size. It have extremely high comprehensive utilization value to separate kaolinite-pyrite cinder that magnetite can be used as good ironmaking raw materials and metakaolin also is excellent cement mixed material and concrete admixture.%为了使高岭石型硫铁矿烧渣中的偏高岭石和铁矿物得到高效利用,本实验就高岭石型硫铁矿烧渣在不同破碎粒级下偏高岭石与磁铁矿的解离程度及试样的破碎粒级对磁选分离效果的影响进行了研究.结果表明:高岭石型硫铁矿烧渣破碎到140~160目,磁铁矿和偏高岭石解离度达99%.通过磁选后所得铁精矿产率为36.00%,品位59.32%,铁回收率89.00%;尾矿中偏高岭石产率及其铁含量均随破碎粒度减小而逐渐降低.铁精矿是很好的炼铁原料,而偏高岭石又是很好的水泥混合材和混凝土活性掺合料,具有极高的综合利用价值.

  2. 改进硫脲法浸出含硫铁矿炼锌渣中银的工艺%Leaching process of silver from zinc-smelting slag of sulfur-bearing pyrite by modified thiourea method

    Institute of Scientific and Technical Information of China (English)

    张玉; 苏静; 龙云飞; 吕小艳; 文衍宣

    2013-01-01

    采用硫脲为络合剂、双氧水为氧化剂,研究了在硝酸介质中浸出含硫铁矿炼锌渣中银的工艺.考察了搅拌速率、反应时间、反应温度、硝酸初始浓度、双氧水浓度、硫脲浓度等因素对银浸出率的影响.结果表明,银的浸出率随着搅拌速率的增大和反应时间的延长先增大然后保持不变,随反应温度、硫脲浓度、双氧水浓度和硝酸初始浓度的增加先增大后减小.当搅拌速率为200 r/min、硝酸浓度为4.11 mol/L、双氧水浓度为0.82 mol/L、硫脲浓度为3.25 mol/L、反应温度为50℃、反应时间为lh时,银浸出率可达82.0%.%The leaching process of silver from zinc-smelting slag of sulfur-bearing pyrite with thiourea as chelating agent and H2O2 as oxidant in HNO3 was studied.The effects of stirring speed,reaction time,reaction temperature,HNO3 initial concentration,H2O2 concentration,and thiourea concentration etc.on the leaching efficiency of silver were investigated.Results showed that the leaching ratio of silver first increased and then kept constant with the increase of the stirring speed and the reaction time,while it first increased and then decreased with the increase of reaction temperature,HNO3 initial concentration,H2O2 concentration,and thiourea concentration.The optimal conditions for leaching of silver with thiourea were found as follows:the stirring speed was 200 r/min,HNO3 initial concentration was 4.11 mol/L,H2O2 concentration was 0.82 mol/L,thiourea concentration was 3.25 mol/L,reaction temperature was 50 ℃,and reaction time was 1.0 h.Under these conditions,the leaching ratio of silver was up to 82.0%.

  3. The Guadiamar soils: characterization and evolution of soils affected by the pyrite sludge; Los suelos del Guadiamar: estudios de caracterizacion y de la evolucion de los suelos contaminados por el lodo

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, C.; Anton-Pacheco, C.; Barettino, D.; Lopez Pamo, E. [Instituto Geologico y Minero de Espana. Madrid (Spain); Cabrera, F.; Fernandez, J. E.; Giron, I. F.; Moreno, F. [Instituto de Recursos Naturales y Agrobiologia de Sevilla (Spain); Fernandez, A. M.; Garcia-Gutierrez, M.; Pelayo, M.; Rivas, P.; Villar, M. V. [Ciemat. Madrid (Spain); Giraldez, J. V.; Vanderlinden, K. [Universidad de Cordoba (Spain); Ordonez, R. [CIFA. Cordoba (Spain)

    2001-07-01

    The study of the geochemical background shows the evidence of high contents in heavy metals in the soils from the affected area of the Guadimar basin before the Aznalcollar mine spill. This means a previous contamination due to the Aznalcollar mineralizations, and above all, to the intense mining works of the last two decades. Two areas been defined, with different geochemical background: Guadiamar alluvial soils and soils over the marsh deposits in the southern area of the affected zone. These southern soils have, higher contents of iron, zinc and copper and slightly lower of lead and arsenic, compared to the contents from the alluvial. The soils of the affected area of the Guadiamar basin are quite heterogeneous and show a high spatial variability of its physical and mineralogical characteristics. Once the sludge removal operations are finished, a high spatial variability of the concentration of soils of different elements related to the contamination has been observed. This variability is observed at a very small scale, so that in a few metres this concentrations vary in some order of magnitude. This variability is also related to the remnant sludge, because the cleanup did not remove the whole of the mining waste, and this remaining part has been incorporated to the soils during the soil remediation operations. At a basin scale, an important increase of the contaminant concentrations has been observed in the upper part of the soils. This concentration mean values are from 3 to 6 times the geochemical background levels, depending on the element considered. These increase are higher for zinc, and lower for lead, arsenic and copper, in that order. The concentrations of these elements in soils decrease with the depth. The highest concentrations for arsenic and lead were observed in the zone where the pyritic sludge was deposited, whereas the highest zinc concentrations are determined in the southern part, where the acid water were retained. After the soil

  4. 山西耿庄黄铁矿晶须形貌的显微观测及其标型意义%Microscopic Observation of the Pyrite Whisker Patterns in Gengzhuang, Shanxi Province, and Its Typomorphic Significance

    Institute of Scientific and Technical Information of China (English)

    黄菲; 寇大明; 宋丹; 王永钱; 成秋明; 高文元; 谭伟

    2011-01-01

    Growth of pyrite whiskers is a special type of crystallization. Three-dimensional microscopic observation was conducted on pyrite whishkers occurring on the different parts of barite crystals from Gengzhuang by using laser microscope. The data indicate that whiskers on different parts of barite crystals vary greatly in size, with lengths ranging usually from 150 /xm to 1700 )nm and diameter from 3. 504 μm to 113. 720 μm and the degree of surface undulation changing from 0. 349 μm to 35. 128 μm. Whisker growth presents a law that whisker's length grows gradually from a zone to d zone, while both diameter and degree of surface undulation decreases gradually. Based on occurrence of crystal whiskers and study of fluid inclusions in barite and EPMA data component data, this study comprehensively analyzed the interrelation between crystal whiskers and hydrothermal state or/and evolution process. It is concluded that huge crystal whiskers with relatively low ratio of length and diameter, surface strumae and high impurity content are typomorphic features for comparatively high temperature and high concentration conditions and represent an unstable growth environment; Whikers with varied diameters and complicated appearance are typomorphic features for a wide range of temperatures, relatively high concentration of components and metastable state; and whiskers with small diameters, equality and simple shape represent typomorphic features for a stable temperature, relatively low concentration of components, and stable state. Increasing diameter of crystal whiskers indicates existence of pulsating and repeated process during process of hydrothermal solution evolution. The microscopic characteristic of crystal whiskers is indicative of hydrothermal activity and provides evidence of mineral morphology for studying features and evolution process of hydrothermal fluids.%黄铁矿的晶须状生长是一种特殊的结晶类型,本次运用激光显微镜,对耿庄重晶石晶

  5. Biological evaluation on poly lactic-co-glycolic acid/pyrite composite active bone repair scaffold%聚乳酸-乙醇酸复合中药自然铜活性骨修复支架生物学评价

    Institute of Scientific and Technical Information of China (English)

    田嘉军; 郑华; 黄聘和; 王定国; 熊成东

    2015-01-01

    目的:评价新型骨修复材料聚乳酸-乙醇酸复合中药自然铜活性骨修复支架的生物安全性。方法根据医疗器械生物学评价标准的要求,选取了溶血试验、细胞毒性试验、遗传毒性试验、刺激与致敏试验、全身毒性试验、植入试验等,全方位评价该新型材料的生物安全性。结果聚乳酸-乙醇酸复合中药自然铜活性骨修复支架的血液相容性良好,无全身毒性和细胞毒性,未发现短期遗传毒性,无皮肤刺激和致敏作用,材料植入骨后周围组织反应正常,骨修复情况良好。结论聚乳酸-乙醇酸复合中药自然铜活性骨修复支架是一种生物相容性好的骨修复材料,可安全应用于临床。%Objective To evaluate biological safety of poly lactic-co-glycolic acid( PLGA )/pyrite composite active bone repalr scaffold. Methods According to biological evaluation criterion of medical devices, we selected hemolytic test, cytotoxicity test, genotoxicity test, tests for irritation and delayed-type hypersensitivity,general toxicity test and implantation test,to evaluate biological safety of the new materials. Results PLGA /pyrite composite active bone repalr scaffold had good blood compatibility,without general toxicity,cell toxicity,skin irritation and sensitization. The tissue reaction was normal after planting to the bone and the bone repalring was in good condition. Conclusions PLGA/ pyrite composite active bone repalr scaffold was one kind of bone repalr material with good biocompatibility and could be safely applied to clinical use.

  6. Contribuição de Cistus Ladanifer L. e Cistus Salviifolius L. na recuperação de áreas mineiras da faixa piritosa ibérica Contribution of Cistus Ladanifer L. and Cistus Salviifolius for environmental rehabilitation of mine areas from iberian pyrite belt

    Directory of Open Access Journals (Sweden)

    Erika Santos

    2011-07-01

    Full Text Available Este estudo teve como objectivo avaliar o potencial de utilização conjunta de Cistus ladanifer e Cistus salviifolius na recuperação ambiental de áreas mineiras abandonadas da Faixa Piritosa Ibérica. Os solos de São Domingos são muito heterogéneos, devido aos materiais que lhes deram origem, apresentando concentrações totais (mg kg-1 elevadas de As (1940-3030, Cu (210-237 e Pb (5280-9210. Contudo, a fracção disponível é, geralmente, baixa variando consoante as características dos solos. O comportamento face aos elementos vestigiais variou com a espécie: C. salviifolius apresentou maiores concentrações de As, Cu e Zn relativamente ao C. ladanifer, contudo para o Pb observou-se o contrário. As plantas de C. ladanifer e C. salviifolius são uma boa aposta para a recuperação ambiental de áreas mineiras da Faixa Piritosa Ibérica pois, apresentam excelente capacidade para colonizar áreas degradadas, grande tolerância a elevadas concentrações de elementos vestigiais no solo, adaptando-se bem a solos nutricionalmente pobres.The aim of this study was to evaluate the potential of combined use of Cistus ladanifer and Cistus salviifolius for environmental rehabilitation of abandoned mine areas from Iberian Pyrite Belt. Soils from São Domingos mine area are heterogeneous, due to different characteristics of the original materials, and showed high total concentrations of trace elements (1940-3030 mg As kg-1; 210-237 mg Cu kg-1; 5280-9210 mg Pb kg-1. Available fractions of trace elements presented, in general, small concentrations which vary with soils characteristics. Cistus salviifolius presented larger concentrations of As, Cu and Zn than C. ladanifer, however the former species showed the smallest Pb concentration. Both Cistus plants have an excellent capacity for colonization of these degraded areas and are well adapted to contaminated soils with low nutrient contents. It is apparent that these plants can be used for

  7. 胶东金青顶金矿床成矿流体来源的黄铁矿微量元素及He-Ar同位素证据%Trace element and He-Ar isotopic evidence of pyrite for the source of oreforming fluids in the Jinqingding gold deposit, eastern Shandong Province

    Institute of Scientific and Technical Information of China (English)

    张运强; 李胜荣; 陈海燕; 张秀宝; 周起凤; 崔举超; 宋玉波; 郭杰

    2012-01-01

    The Jinqingding gold deposit with identified reserves of more than 50t is currently the largest lode gold deposit in terms of single vein gold resources and is also a superlarge gold deposit located in the middle part of the Muping- Rushan gold belt in Jiaodong; nevertheless, the genetic type and source of ore-forming fluids in the gold deposit constitute a problem that needs urgent solution. A study of trace elements and REE compositions and features of gold-bearing pyrite from No. II ore body of the Jinqingding gold deposit reveals that the pyrite displays hydrothermal characteristics with Co/Ni ratios from 2.317 to 11.734 (7.17 on average). The HFSE indicates that the ore-forming fluid originally belonged to the F-rich system and generally evolved into the Cl- rich system at the chief metallogenic stage, and the distribution patterns of REE shows that the source of matallogenic materials was not mainly from Mesozoic Kunyunshan monzonitic granite. According to an analysis of the characteristic parameters (3He/4He =0.1-2.2 Ra (0.60 Ra on average)),40Ar/36Ar =462.7-1507.5 (831 on average), it is considered that the source of matallogenic materials was mainly derived from the lower crust and was contaminated by meteoric water during the intrusion, and the mantle fluids were involved in the metallogenic process.%金青顶金矿床是目前国内最大的石英单脉型金矿,其金储量超过50 t,规模为大型.对该矿床成矿流体性质和来源的研究十分必要.笔者通过Ⅱ号矿体主要载金矿物黄铁矿微量元素的研究发现,其Co/Ni为2.317~11.734(平均7.17),显示主要为热液成因;高场强元素(HFSE)特征显示,成矿早期以富F流体为主,主成矿期以富C1流体为主;稀土配分模式显示成矿物质并不是直接来源于围岩昆嵛山二长花岗岩.对黄铁矿流体包裹体He、Ar同位素特征的研究表明,3He/4He、40Ar/36Ar分别为0.1~2.2 Ra(平均值0.60 Ra),462.7~1 507.5(平均值831),显示成

  8. 黄铁矿产酸成分与中和酸成分的消耗及其有效成分的确定%DEPLETION OF ACID POTENTIAL (AP) AND NEUTRALIZATION POTENTIAL (NP) FROM PYRITE AND THE DETERMINATION OF AP AND NP AVAILABILITY

    Institute of Scientific and Technical Information of China (English)

    李锦文; 李晓; 吴惠明; 陈永亨; Basra Sohan

    2011-01-01

    动态浸滤法研究黄铁矿氧化产酸过程中产酸成分(AP)和中和酸成分(NP)的消耗,讨论了有效NP、AP的确定.50周实验结果表明:(1)中和酸成分NP和产酸成分AP消耗速率呈非线性变化.酸性排放(ARD)前,即pH=4前,AP、NP平均消耗速率VAP与VNPp基本相同;ARD开始释放后,VAP>2VNP;(2)排放液pH<3后,Fe3+参与并加速氧化反应,AP消耗的平均速率及固溶物溶出速率提高4倍以上;(3)抑制ARD释放的有效NP<50%,控制排放液中性的有效NP<30%;引起ARD释放的有效AP>75%,且ARD将持续释放30年以上.%The depletion of Neutralization Potential (NP) and Acid Potential (AP) and the determination of available AP and available NP in pyrite acidification process were studied by using kinetic flood leaching in humidity cell. 50 cycles kinetic test for the studied sample shows that: ( 1 ) The rate of NP and AP depletion changed nonlinearly. The average rate of NP depletion (VNP) is almost same as the average rate of AP deletion (VAP) before onset of acid rock drainage ( drainage pH = 4). VAP is more than 2 VNP after onset of acid rock drainage (ARD); (2) Fe3 + speeds the sulphide oxidation and VAP together with the rate of mineral dissolution increased by over 4 times after drainage pH < 3; (3) The NP availability controlling ARD is less than 50% and NP availability keeping drainage neutral is less than 30%. The AP availability causing ARD is more than 75% and ARD will last more than 30 years.

  9. Evaluation of pyritic mine tailings as a plant growth substrate.

    Science.gov (United States)

    Roseby, Stuart J; Kopittke, Peter M; Mulligan, David R; Menzies, Neal W

    2017-10-01

    At the Kidston gold mine, Australia, the direct establishment of vegetation on tailings was considered as an alternative to the use of a waste rock cover. The tailings acid/base account was used to predict plant growth limitation by acidity, and thus methods capable of identifying tailings that would acidify to pH 4.5 or lower were sought. Total S was found to be poorly correlated with acid-generating sulfide, and total C was poorly correlated with acid-neutralizing carbonate, precluding the use of readily determined total S and C as predictors of net acid generation. Therefore, the selected approach used assessment of sulfide content as a predictor of acid generation, and carbonate content as a measure of the acid-neutralizing capacity available at pH 5 and above. Using this approach, the majority of tailings (67%) were found to be non-acid generating. However, areas of potentially acid-generating tailings were randomly distributed across the dam, and could only be located by intensive sampling. The limitations imposed by the large sample numbers, and costly analysis of sulfide and carbonate, make it impractical to identify and ameliorate acid-generating areas prior to vegetation establishment. However, as only a small proportion of the tailings will acidify, a strategy of re-treating acid areas following oxidation is suggested. The findings of the present study will assist in the selection of appropriate methods for the prediction of net acid generation, particularly where more conservative measurements are required to allow vegetation to be established directly in tailings. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Extracellular polymers of acid streamers from pyritic mines

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.B.; Kelso, W.I.

    1981-01-01

    Extracellular polymers (slimes) extracted from acid streamers found in three disused North Wales mines were found to be a mixture of polysaccharides and RNA. The polymers exist as microfibrils synthesised by viable members of the acid streamer microbial community. Acid streamers from three mines, and from different zones in one of the mines, were shown to contain similar polymers, although the ratio of monomers varied from site to site. Monosaccharides identified in acid hydrolysates of slimes were glucose, galactose, mannose, ribose, xylose, arabinose, rhamnose and fucose.

  11. Some quantitative data on bacterial attachment to pyrite

    NARCIS (Netherlands)

    Florian, B.; Noël, N.; Thyssen, C.; Felschau, I.; Sand, W.

    2011-01-01

    Bacterial attachment and biofilm formation are important for microbial bioleaching of metal sulfides, however, many details of the role played by bacteria are still unknown. Attachment as the first step in biofilm formation is critical. Our investigations are focused on these processes to control ba

  12. Iron monosulfide accumulation and pyrite formation in eutrophic estuarine sediments

    NARCIS (Netherlands)

    Kraal, P.; Burton, E.D.; Bush, R.T.

    2013-01-01

    This study investigates iron (Fe) and sulfur (S) cycling in sediments from the eutrophic Peel–Harvey Estuary in Western Australia, which is subject to localized accumulation of strongly reducing, organic- and sulfide-rich sediments. Sedimentary iron was mostly present in highly reactive form (on

  13. MICROBIAL OXIDATION OF PYRITE: EXPERIMENTS USING MICROORGANISMS FROM AN EXTREME ACIDIC ENVIRONMENT. (R826189)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Advective and diffusive contributions to reactive gas transport during pyrite oxidation in the unsaturated zone

    DEFF Research Database (Denmark)

    Binning, Philip John; Postma, Diederik Jan; Russel, T.F.;

    2007-01-01

    at depth in the unsaturated zone, a pressure gradient is created between the reactive zone and the ground surface, causing a substantial advective air flow into the subsurface. To determine the balance between advective and diffusive transport, a one-dimensional multicomponent unsaturated zone gas...... flows at steady state. However, greater pressure gradients are found in low-permeability soils. In transient cases, advective fluxes depend on the initial conditions and can be far greater than diffusive fluxes. In contrast to steady state conditions the transient case is sensitive to other model...

  15. Study of CO adsorption on perfect and defective pyrite(100)surfaces by density functional theory

    Institute of Scientific and Technical Information of China (English)

    Yudong Du; Wenkai Chen; Yongfan Zhang; Xin Guo

    2011-01-01

    First-principles calculations based on density functional theory(DFT)and the generalized gradient approximation(GGA)have been used to study the adsorption of CO molecule on the perfect and defective FeS2(100)surfaces.The defective Fe2S(100)surfaces are caused by sulfur deficiencies.Slab geometry and periodic boundary conditions are employed with partial relaxations of atom positions in calculations.Two molecular orientations,C-and O-down,at various distinct sites have been considered.Total energy calculations indicated that no matter on perfect or deficient surfaces,the Fe position is relatively more favored than the S site with the predicted binding energies of 120.8 kJ/mol and 140.8 kJ/mol,respectively.Moreover,CO was found to be bound to Fe atom in vertical configuration.The analysis of density of states and vibrational frequencies before and after adsorption showed clear changes of the C-O bond.

  16. Analysis of the microbial community in moderately acidic drainage from the Yanahara pyrite mine in Japan.

    Science.gov (United States)

    Wang, Yang; Yasuda, Takashi; Sharmin, Sultana; Kanao, Tadayoshi; Kamimura, Kazuo

    2014-01-01

    Acid rock drainage (ARD) originating from the Yasumi-ishi tunnel near the main tunnel of the Yanahara mine in Japan was characterized to be moderately acidic (pH 4.1) and contained iron at a low concentration (51 mg/L). The composition of the microbial community was determined by sequence analysis of 16S rRNA genes using PCR and denaturing gradient gel electrophoresis. The analysis of the obtained sequences showed their similarity to clones recently detected in other moderately acidic mine drainages. Uncultured bacteria related to Ferrovum- and Gallionella-like clones were dominant in the microbial community. Analyses using specific primers for acidophilic iron- or sulfur-oxidizing bacteria, Acidithiobacillus ferrooxidans, Leptospirillum spp., Acidithiobacillus caldus, Acidithiobacillus thiooxidans, and Sulfobacillus spp. revealed the absence of these bacteria in the microbial community in ARD from the Yasumi-ishi tunnel. Clones affiliated with a member of the order Thermoplasmatales were detected as the dominant archaea in the ARD microbial population.

  17. Pyrite-enhanced methylene blue degradation in non-thermal plasma water treatment reactor.

    Science.gov (United States)

    Benetoli, Luís Otávio de Brito; Cadorin, Bruno Mena; Baldissarelli, Vanessa Zanon; Geremias, Reginaldo; de Souza, Ivan Gonçalvez; Debacher, Nito Angelo

    2012-10-30

    In this study, methylene blue (MB) removal from an aqueous phase by electrical discharge non-thermal plasma (NTP) over water was investigated using three different feed gases: N(2), Ar, and O(2). The results showed that the dye removal rate was not strongly dependent on the feed gas when the electrical current was kept the same for all gases. The hydrogen peroxide generation in the water varied according to the feed gas (N(2)degradation occurs via high energy electron impact as well as successive hydroxylation in the benzene rings of the dye molecules.

  18. QUANTUM CHEMICAL STUDY ON THE REACTION OF PYRITE WITH NITRIC ACID~+

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    QUANTUMCHEMICALSTUDYONTHEREACTIONOFPYRITEWITHNITRICACID~+¥YangTianzu;ZhaoTiancong;LuYiyuan(DepartmentofNonferrousMetallurgy,C?..

  19. Transport and degradation of chlorofluorocarbons (CFCs) in the pyritic Rabis Creek aquifer, Denmark

    DEFF Research Database (Denmark)

    Hinsby, K.; Hojberg, A.L.; Engesgaard, P.;

    2007-01-01

    of Fe(III)-bearing weathering products (green rust) may be a plausible mechanism. The observed data and the performed simulations confirm the potential application of the CFC gases as age-dating tools in the aerobic part of the investigated aquifer, but also that CFC data must be analyzed carefully...

  20. Denitrification coupled to pyrite oxidation and changes in groundwater quality in a shallow sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Slomp, C.P.; Broers, H.P.; Passier, H.F.; Cappellen, P. van

    2009-01-01

    This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating (3H/3He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherland