Our pyrite formation mechanisms

Pyrite-Induced Hydrogen Peroxide Formation as a Driving ...


Jul 05, 2004· The remarkable discovery of pyrite-induced hydrogen peroxide (H 2 O 2) provides a key step in the evolution of oxygenic photosynthesis.Here we show that H 2 O 2 can be generated rapidly via a reaction between pyrite and H 2 O in the absence of dissolved oxygen. The reaction proceeds in the dark, and H 2 O 2 levels increase upon illumination with visible light.

Iron sulfide Formation-3-10-2011


The understanding of iron sulfide formation under Earth surface conditions has largely been informed by extensive laboratory studies (see summary by Morse et al., 1987). Multiple potential pathways for sedimentary iron sulfide (pyrite) formation have been recognized. As summarized

Kinetics of pyrite formation by the H2S oxidation of iron ...


Kinetics of pyrite formation by the H2S oxidation of iron (II) monosulfide in aqueous solutions between 25 and 125°C: The mechanism DAVID RICKARDl and GEORGE W. LUTHER III 2 tDepartment of Earth Sciences, University of Wales, Cardiff CF13YE, Wales, UK 2College of Marine Studies, University of Delaware, Lewes, Delaware 19958, USA

Coupled partitioning of Au and As into pyrite controls ...


Coupled As and Au partitioning during experimental siderite replacement by pyrite. The partitioning of As and Au into pyrite was studied by replacing siderite (FeCO 3) by pyrite (FeS 2) by reacting the Fe carbonate with H 2 S-containing aqueous fluids under experimental conditions similar to those of CTGD formation (i.e., 200°C, fluid-dominated conditions, 0.05 m H 2 S, and slightly acidic ...

Formation processes of framboidal pyrite - ScienceDirect


Although greigite (Fe3S4) is a ferrimagnetic precursor to pyrite, and greigite formation is considered to be a key step in framboid formation (Sweeney and Kaplan, 1973; Morse et al., 1987), mechanisms that might form framboidal pyrite via the attraction of greigite microcrystals have not been critically evaluated.

Suppression of Pyrite Oxidation by Formation of Iron ...


Based on the oxidation mechanism, the rate of pyrite oxidation and the environmental contamination by the acid drainage can be reduced with reducing activity of free 3+ Fe, depriving O2, and neutralizing acidity. Acid drainage abatement technologies include physical barriers to prevent the contact of water and O2 to pyrite surface.

Replacement of pyrrhotite by pyrite and marcasite under ...


The pyrrhotite to Fe disulfide reaction proceeded by a dissolution-reprecipitation mechanism under all conditions. Marcasite and pyrite formed under both oxic and anaerobic conditions, which is inconsistent with the traditionally assumed polysulfide route for FeS2 formation (oxidants required for polysulfide formation).

Pyrite-induced hydroxyl radical formation and its effect ...


While the exact mechanism or mechanisms of the hydrogen peroxide-to-hydroxyl radical conversion cannot be resolved on the basis of the experiments reported in this study, it is clear that the pyrite surface promotes the reaction. The formation of hydroxyl radicals is significant because they react nearly instantaneously with most organic molecules.

Formation mechanism of pyrite framboid and its research ...


Formation mechanism of pyrite framboid and its research significance: Zhou Jie 1,2 Qiu Zhen 2,3 Wang Hongyan 2 Lu Bin 2 Bai Wenhua 2 Liu Dexun 2 Tan Xin 4 Jiang Zengguang 4: Research Institute of Seepage Fluid Mechanics,The University of Chinese Academy of Sciences,Langfang,Hebei 065007;

Experimental study of formation mechanisms of hydrothermal ...


In the following S" surfaces differs from that of pyrite crystals formed on section, habit sequence I refers to pyrite formation via pyr- pyrrhotite surfaces has led us to propose that two mechanisms rhotite precursor surfaces and habit sequence II to pyrite for- existed in our experimental systems for nucleation and growth mation on S ...

24. FRAMBOIDAL PYRITE IN DEEP-SEA SEDIMENTS Federal ...


24. FRAMBOIDAL PYRITE IN DEEP-SEA SEDIMENTS1 Roger Schallreuter, Geologisch-Palàontologisches Institut und Museum, University of Hamburg, Hamburg, Federal Republic of Germany ABSTRACT The framboidal form of pyrite from two different types of sediments at DSDP Site 530 (Angola Basin) was ex- ... The formation mechanism of the framboids is ...

Mechanism of Sulfur Oxidation in Pyrite - 911metallurgist.com


The Mechanism of Sulfur Oxidation in Pyrite is base on what is generally believed as anodic oxidation of pyrite occurs according to the reactions to form S° and SO4=. ... The change in electrochemical behavior on repeated scanning is associated with formation of intermediates during oxidation. For the cathodic peak, the parameter βC remained ...

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.

Geochemical Transactions BioMed Central - Home - Springer


transition state, commensurate with a solid-state mechanism. Background The formation of pyrite is an important geochemical path-way linking the global biogeochemical cycles of iron, sul-fur and carbon in anoxic sediments [1-3]. Furthermore, chemical reactions involved in pyrite formation have important implications for the fate and mobility of ...

Mechanism of Pyrite Dissolution in the Presence of ...


pyrite. In this mechanism, the rate of dissolution of pyrite is dependent on the concentrations in solution, in particular the concentrations of ferric and ferrous ions, and the pH (15, 30). In this mechanism, the bacteria do not directly affect the rate of dissolution of pyrite. However, in 1964, Silverman and Ehrlich (24) proposed that

Role of pyrite in formation of hydroxyl radicals in coal ...


By comparing coal samples of varying pyrite content with cellular toxicity and cellular formation of ROS, the role of pyrite and ROS in the mechanisms that lead to …

MARCASITE IN BLACK SHALES—A MINERAL PROXY FOR …


pyrite framboids and corrosion features on pyrite grains indicate partial pyrite destruction in surface sediments, and suggest that intermittent reoxidation of earlier formed iron sulfides may indeed have generated the low pH values required for marcasite formation.

Oxidation of pyrite during extraction of carbonate ...


pyrite values, the isotopic offset imparted by oxidation of pyrite should be much less than −4‰. Awealth of literature exists on the oxidation of pyrite by Fe3+ and we believe this mechanism drives the oxidation of pyrite during CAS extraction, during which the oxygen used to form sulfate is taken from H 2O, not O 2. Consequently ...

Pyrite Oxidation Mechanism by Oxygen in Aqueous Medium ...


The mechanism of the initial steps of pyrite (100) surface oxidation was investigated in detail by means of density functional theory/plane-wave calculations. Pyrite oxidation is related to many environmental and technological issues, and its mechanism has not been completely understood. A chemical picture of the pyrite oxidation process in the presence of oxygen and water was proposed in the ...

(PDF) Kinetics and Mechanism of Pyrite Formation at Low ...


The kinetics of pyrite formation in the reaction between FeS, sulfur, and hydrogen sulfide in aqueous solution have been investigated between 20 degree and 50 degree C and at 1 atm pressure.

Formation of zinc sulfide species during roasting of ZnO ...


May 18, 2018· Formation of zinc sulfide species during roasting of ZnO with pyrite and its contribution on flotation. ... In this paper, the formation mechanisms of zinc sulfides involving evolution process ...

Effect of pH and Dissolved Silicate on the Formation of ...


The oxidant can be inhibited at pyrite particle surfaces by a surface barrier through the formation of pasivation s layers [2,3,7-10] and some coating agents, e.g. acetyl acetone, humic acids, ammonium lignosulfonates, oxalic acid and sodium silicate, were reported to be employed-for pyrite surface treatmentbut only minor reductions in

(PDF) Mechanisms of sedimentary pyrite formation | Martin ...


Sedimentary pyrite formation is the mechanism of pyrite formation and specifically to derive reac- by no means restricted to marine coastal environments, although tion rates, there are still some significant gaps in our knowledge. that is where most sedimentary pyrite is formed.

Mechanisms of sedimentary pyrite formation | Request PDF


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 ...

MECHANISMS OF PYRITE OXIDATION TO NON-SLAGGING ... - …


Sep 01, 2002· The propensity for slagging can be minimized by the judicious redistribution of furnace air to maximize the oxide formation rate. This must be accomplished with minimal degradation of other aspects of boiler performance. To effect this, an understanding of the rate-limiting mechanisms of pyrite oxidation is required.

Experimental study of formation mechanisms of hydrothermal ...


A second mechanism to explain the accumulation of polysulfides in liquid S droplets involves the concept of equilibrium polymerization of S at T > 159° C. This process results in the formation of radical chain S. Polysulfides may form when the sulfur radical reacts with H 2 S (aq) from the experimental solution upon which nucleation of pyrite ...

Mackinawite - Wikipedia


Mackinawite is a metastable mineral that occurs predominantly as a poorly crystalline precipitate. After the initiation of precipitation, mackinawite can take up to 2 years to form at 25 °C. It has been reported that mackinawite can be stable for up to 16 weeks at temperatures up to 100 °C at pH values from 3-12.

Mineral Vein Formation Mechanism


Mineral Vein Formation Mechanism ... Pyrite is usually one of the first sulphide minerals deposited, and microscopic examination shows that the pyrite crystals are commonly ruptured and the fragments separated by later minerals, such as chalcopyrite, bornite, etc. Graton and Murdoch, after an extensive investigation, state that ...

Ziad Beydoun Memorial Award for 2014 Best Poster at AAPG ...


Bacterial sulphate reduction is considered the most likely mechanism for late authigenic pyrite formation given the present reservoir temperature of approximately 100ºC and the minimum quartz overgrowth homogenisation temperatures of 78ºC (Lisk et al., 1999). In addition

Pyrite framboids and their development: a new conceptual ...


It has been suggested that the two morphologies of sedimentary pyrite, framboids and euhedra, may reflect two distinct pathways of pyrite formation. Framboids form indirectly via iron monosulphides, whereas euhedra form from direct precipitation from solution.


Top