Poducts

  • Pyrite formation from FeS and H2S is mediated through

    02.04.2019· With an annual formation of at least 5 million tons, pyrite (FeS 2) is the thermodynamically stable end product of iron compounds reacting with sulfide in reduced sediments, with the latter being produced mainly by microbial sulfate reduction. Consequently, pyrite is the most abundant iron−sulfur mineral on Earth’s surface (1).

  • Cited by: 17
  • Pyrite an overview | ScienceDirect Topics

    Harmandas et al. measured Ω pyrite ∗ in the presence of pyrite seeds to be 5.7 × 10 14 for reaction 5. This result is important since it means that at Ω pyrite ∗ < 10 14 the rate of pyrite nucleation determines the rate of pyrite formation.

  • Pyrite an overview | ScienceDirect Topics

    Converting this to the solubility reactions in terms of HS − gives a similar value for Ω pyrite *. This result is important as it means that at Ω pyrite * < 10 14 the rate of pyrite nucleation determines the rate of pyrite formation. At Ω pyrite * > 10 14 the rate of pyrite crystal growth is the rate limiting process. Rickard et al. (2007) synthesized pyrite from undersaturation with

  • Mechanisms of sedimentary pyrite formation | Sulfur

    The mechanisms of pyrite formation are reviewed. Advances since 1994 in our understanding of the mechanisms and rate of pyrite formation, the role of bacteria in the formation of pyrite, framboid formation, and incorporation of impurities into pyrite are emphasized. Both field studies as well as laboratory studies designed to better represent natural environments have provided significant new

  • Abiotic Pyrite Formation Produces a Large Fe Isotope

    We measured maximum rates of pyrite formation (~2.8 × 10 −6 mol of pyrite l −1 s −1) close to published data [~ 3 × 10 −6 mol of pyrite l −1 s −1 ]. The pyrite-forming process is mechanistically uniform over the 25° to 125°C temperature range ( 13 ), and the observed temperature-independent effect indicates that our results may be extrapolated with reasonable confidence to

  • Alkalinity production coupled to pyrite formation

    This study evaluates drivers of pyrite formation in coastal vegetated habitats, compares pyrite production to TAlk outwelling rates, and estimates global pyrite stocks in mangroves. We quantified pyrite stocks in mangroves, saltmarshes and seagrasses along a latitudinal gradient on the Australian East Coast, including a mangrove dieback area, and in the Everglades (Florida, USA). Our results

  • Pathways for Neoarchean pyrite formation constrained

    29.10.2013· The euhedral (type 2) pyrite grains have positive δ 34 S values, in contrast to the type 1 grains, which range from 5‰ to 22‰. The Δ 33 S of the type 2 grains is also positive, ranging from about 5‰ to 10‰. These grains have negative Δ 36 S values ranging from −12‰ to −4‰.

  • Cited by: 106
  • Pyrite formation and the measurement of sulfate reduction

    Pyrite formation and the measurement of sulfate reduction in salt marsh sediments l Robert W. Howarth and Susan Merkel The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 Abstract A new method was used to study the formation of pyrite plus elemental sulfur during 35S0,2- reduction experiments in salt marsh sediments: the reduction with chromium(I1) of pyrite

  • Cited by: 183
  • Pyrite Wikipedia

    Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold.The color has also led to the nicknames brass, brazzle, and Brazil, primarily used to refer to pyrite found in coal.. The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), "stone or mineral which strikes fire", in turn from

  • Crystal class: Diploidal (m3), H-M symbol: (2/m 3)
  • AMD: Basic chemistry Lehigh University

    Pyrite + Oxygen + Water => Ferrous Iron + Sulfate + Acidity . The second reaction involves the conversion of ferrous iron to ferric iron. The conversion of ferrous iron to ferric iron consumes one mole of acidity. Certain bacteria increase the rate of oxidation from ferrous to ferric iron. This reaction rate is pH dependent with the reaction proceeding slowly under acidic conditions (pH 2-3

  • Pyrite formation and the measurement of sulfate reduction

    Pyrite formation and the measurement of sulfate reduction in salt marsh sediments l Robert W. Howarth and Susan Merkel The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 Abstract A new method was used to study the formation of pyrite plus elemental sulfur during 35S0,2- reduction experiments in salt marsh sediments: the reduction with chromium(I1) of pyrite

  • Abiotic Pyrite Formation Produces a Large Fe Isotope

    We measured maximum rates of pyrite formation (~2.8 × 10 −6 mol of pyrite l −1 s −1) close to published data [~ 3 × 10 −6 mol of pyrite l −1 s −1 ]. The pyrite-forming process is mechanistically uniform over the 25° to 125°C temperature range ( 13 ), and the observed temperature-independent effect indicates that our results may be extrapolated with reasonable confidence to

  • Pyrite formation and the measurement of sulfate

    A new method was used to study the formation of pyrite plus elemental sulfur during 3 5 SO 4 2 ‒ reduction experiments in salt marsh sediments: the reduction with chromium(II) of pyrite and elemental sulfur to hydrogen sulfide. It is both more specific and more sensitive than our previous method, the oxidation of pyrite and elemental sulfur to sulfate by aqua regia, which measures the

  • Pyrite Oxidation Kinetics How Fast does Pyrite Oxidize

    Pyrite oxidation has been studied extensively, in the past, because of its importance in sulfide mineral separations by flotation, in the generation of acid in mine waters and in leaching of pyrite. The oxidation of pyrite also plays key role in supergene alteration of ore deposits, the formation of acid sulfate soils, etc. Pyrite oxidation is generally recognized as a complicated process

  • PYRITE OXIDATION RATES FROM HUMIDITY CELL TESTING OF

    within and among formations. Lapakko and Antonson (2001, 2002) reported on earlier phases of the laboratory studies presented. Pyrite Oxidation Rates The major water quality concern regarding mine waste drainage quality is generation of acidic drainage and associated metal leaching, although release of metals in neutral drainage can also adversely impact water quality. Acid is released as a

  • Pyrite: Mineral information, data and localities.

    Pyrite Group. The isometric (cubic) polymorph of orthorhombic marcasite.Compare UM1997-43-S:Fe. Pyrite is a very common mineral (also one of the most common natural sulfides, and the most common disulfide), found in a wide variety of geological formations from sedimentary deposits to hydrothermal veins and as a constituent of metamorphic rocks.The brassy-yellow metallic colour of pyrite has in

  • (PDF) Pyrite formation in euxinic and semi-euxinic

    Other factors limiting pyrite formation include the amount of organic matter, availability of sulphates and the rate of their reduction, and consequently the concentration of hydrogen sulphide in

  • Greigite: a true intermediate on the polysulfide pathway

    The formation of pyrite (FeS[2] ) from iron monosulfide precursors in anoxic sediments has been suggested to proceed via mackinawite (FeS) and greigite (Fe[3] S[4] ). Despite decades of research, the mechanisms of pyrite formation are not sufficiently

  • AMD: Basic chemistry Lehigh University

    Pyrite + Oxygen + Water => Ferrous Iron + Sulfate + Acidity . The second reaction involves the conversion of ferrous iron to ferric iron. The conversion of ferrous iron to ferric iron consumes one mole of acidity. Certain bacteria increase the rate of oxidation from ferrous to ferric iron. This reaction rate is pH dependent with the reaction proceeding slowly under acidic conditions (pH 2-3

  • Pyrite Wikipedia

    Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold.The color has also led to the nicknames brass, brazzle, and Brazil, primarily used to refer to pyrite found in coal.. The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), "stone or mineral which strikes fire", in turn from

  • Pyrite formation and the measurement of sulfate reduction

    Pyrite formation and the measurement of sulfate reduction in salt marsh sediments l Robert W. Howarth and Susan Merkel The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 Abstract A new method was used to study the formation of pyrite plus elemental sulfur during 35S0,2- reduction experiments in salt marsh sediments: the reduction with chromium(I1) of pyrite

  • Pyrite formation and the measurement of sulfate

    A new method was used to study the formation of pyrite plus elemental sulfur during 3 5 SO 4 2 ‒ reduction experiments in salt marsh sediments: the reduction with chromium(II) of pyrite and elemental sulfur to hydrogen sulfide. It is both more specific and more sensitive than our previous method, the oxidation of pyrite and elemental sulfur to sulfate by aqua regia, which measures the

  • Pyrite Oxidation Mechanism by Oxygen in Aqueous Medium

    08.11.2015· is well-known that different bacteria can catalyze the pyrite oxidation at a much rapid rate, making its mechanism even more complex.20 Many works identified the formation of oxidative dissolution products on pyrite, and surface sensitive techniques have been carried out to understand the pyrite reactivity in the presence of different adsorbents. Different techniques have been used such

  • Pyrite Oxidation Rates from Laboratory Tests on Waste Rock

    expression for the rate of pyrite oxidation in moist air: dFeS 2 10 6.6 0.5 0.5Pt dt (2) where, dFeS 2 /dt is the rate of pyrite oxidation (mol m−2 s−1), P is the partial pressure of oxygen (atm) and t is time in seconds. They reported that the reaction rate decreased over time due to formation of a precipitate layer on the mineral surface that inhibited oxygen transport. The present

  • PYRITE OXIDATION RATES FROM HUMIDITY CELL TESTING OF

    within and among formations. Lapakko and Antonson (2001, 2002) reported on earlier phases of the laboratory studies presented. Pyrite Oxidation Rates The major water quality concern regarding mine waste drainage quality is generation of acidic drainage and associated metal leaching, although release of metals in neutral drainage can also adversely impact water quality. Acid is released as a

  • Abiotic Pyrite Formation Produces a Large Fe Isotope

    Fe(II)RES-pyrite] are1.0025 T0.0007and1.0021 T0.0004at40°C and 100°C, respectively. Within errors, these fractionation factors are indistinguishable, and on average a′ Fe(II)RES-pyrite is 1.0022 T 0.0007. This is large compared with the fractionation during FeS m formation. We measured maximum rates of pyrite formation (~2.8 × 10−6 mol of

  • Pyrite formation by reactions of iron monosulfides with

    Pyrite formation should occur by similar paths at 70°C and at temperatures representative of early sediment diagenesis ( <25”C) ; however, because of the activation energy of heterogeneous processes, reaction rates are temperature-dependent and should be faster at 70°C. At the beginning of an experiment, to remove all air and adsorbed solutes, the vessel was filled with a dilute NaOH

  • Contributions of Microbial “Contact Leaching” to Pyrite

    The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential of the solution and isolate pyrite from microbial contact oxidation.

  • Role of pyrite in formation of hydroxyl radicals in coal

    Pyrite has recently been shown to spontaneously generate hydrogen peroxide (H 2 O 2) [32, 33] and hydroxyl radicals (• OH) [23, 24] when placed in water.The formation of these reactive oxygen species (ROS) also explains the recent observation that aqueous pyrite slurries degrade yeast RNA, ribosomal RNA, and DNA [].Pyrite is thought to form H 2 O 2 through the iron-catalyzed Haber-Weiss

  • AMD: Basic chemistry Lehigh University

    Pyrite + Oxygen + Water => Ferrous Iron + Sulfate + Acidity . The second reaction involves the conversion of ferrous iron to ferric iron. The conversion of ferrous iron to ferric iron consumes one mole of acidity. Certain bacteria increase the rate of oxidation from ferrous to ferric iron. This reaction rate is pH dependent with the reaction proceeding slowly under acidic conditions (pH 2-3