pyrite formation rate
OXIDATIVE DISSOLUTION OF PYRITE: A COMBINED EXPERIMENTAL AND IRON ISOTOPE INVESTIGATION by AMY LYNN WOLFE B.S. Marine Science, University of South Carolina, 2001 Submitted to the Graduate Faculty of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2010
The expected amounts of organic matter decomposition and reduced sulfur (mainly pyrite) formation over selected sediment depth ranges have been calculated, from /sup 35/S measurements of in situ rates of sulfate reduction, for four anoxic sediment sites in Long Island Sound.
A 1 million tonne pyrite deposit could form from a solution containing 1 mmol FeS and 1 mmol H 2 S by this process in 1000 years at a flow rate of 0.3 Ls -1. The fluid would have a H 2 concentration of 3 × 10 -9 M. The process is by far the most rapid of the pyrite-forming reactions hitherto identified.
High burial (and bioturbation) rates enable reactive compounds to become available for sulphate reduction, at depth, which otherwise would be destroyed by molecular oxygen at or above the sediment-water interface. An important consequence of bacterial sulphate reduction is the formation of sedimentary pyrite, FeS 2. In normal marine sediments ...
Oct 29, 2013· Experimental and field studies have suggested that large framboidal pyrite grains typically form in sulfide-rich environments and associated with rapid rates of pyrite formation, whereas euhedral pyrite grains form in settings where sulfide concentrations are lower and pyrite formation rates are slower (20 ⇓ –22).
The effect of temperature on the oxidation rates of sulphides in tailings has been discussed in many studies . A significant increase in the oxidation rate of pyrite and pyrrhotite with ...
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 ...
At pH = 7, for the same total sulfide and FeS constraints, the rate of pyrite formation 1.5 10-9 to 1.5 10-4 mol FeS2 per g sediment per year. In hydrothermal systems, such as deep ocean vents, the rate of pyrite formation by oxidation of FeS by H2S at 125 assuming a typical HzS concentration of 1 mM is 3.2 10_6 mol L i s-1 per mol FeS.
Jun 24, 2011· The iron isotope composition of sedimentary pyrite has been proposed as a potential proxy to trace microbial metabolism and the redox evolution of the oceans. We demonstrate that Fe isotope fractionation accompanies abiotic pyrite formation in the absence of Fe(II) redox change. Combined fractionation factors between Fe(II)aq, mackinawite, and pyrite permit the generation of pyrite …
This result is important since 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 and this feature was exploited by Harmandas et al. in their experimental investigation of pyrite crystal-growth kinetics.
Allowing for the inherent errors in the latter observations, there appeared to be a predictive relationship between the results from the partial oxidation and the rate of pyrite oxidation in the shale. Of the ten shales, seven had an annual pyrite oxidation approximately 2.5 times their partial oxidation values (mMoles/kg/year).
pyrite transformation to magnetite, finer grinding of the coal feed to liberate pyrite inclusions would enhance the rate of the overall pyrite conversion process. In addition, smaller coal-char particles would have higher internal oxygen levels (higher effectiveness factors) and hence, pyrite inclusions would have higher rates of oxidation.
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.
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 ...
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 ...
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
Figure 1 Aqueous nickel impurity accelerates the formation of pyrite from a FeS (m) precursor. Powder XRD patterns of the solids collected over the course of the pyrite synthesis experiments conducted at room temperature in the absence (left) or presence (right) of aqueous Ni in the starting solution.
Sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time. The amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter, dissolved sulfate, and reactive detrital iron ...
The latter fraction provided a lower limit for the OS contribution to pyrite formation, as additional pyrite could originate from mineralization of the oxidized OS pool upon its reduction in sediment.
Read "Kinetics of pyrite formation by the H 2 S oxidation of iron (II) monosulfide in aqueous solutions between 25 and 125°C: The rate equation, Geochimica et Cosmochimica Acta" on DeepDyve, the largest online rental service for scholarly research with thousands of …
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 ...
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.
Acid/Base Balance and Reaction Rates ... The conditions most conducive to acid formation are high pyrite contents with little base material present. Conversely, an excess of base relative to pyrite is most likely to preclude acid formation. ... Although the basic processes of acid mine drainage formation are universal, the importance of any single
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.
Kinetics of the marcasite-pyrite transformation: An infrared spectroscopic study Ar-rsrarn R. LnNNrn, Davro J. YaucneN ... the formation of pyrite in the marcasite matrix. ... mental work that the rate of direct nucleation of pyrite and marcasite in slightly acidic solutions is insignificant below 573 K. Instead, most pyrite and marcasite in hy-
The rate of pyrite formation For example, it is tacitly assumed in abiotic experiments that in these experiments was enhanced by the presence of ferrihy- the role of dissimilatory sulfate-reducing bacteria is restricted to drite, the most reactive Fe(III)-hydroxide phase known (Canfield the formation of hydrogen sulfide.
Sedimentary pyrite formation: An update ... rates of pyrite sulfur burial and organic carbon burial over Phanerozoic time and results are shown in Fig. 11. Note that percentage changes in pyrite burial are much greater than cor- responding changes in organic carbon burial and this results in large calculated worldwide changes in C/S ratios of ...
The dissolution of pyrite is important in the geochemical cycling of iron and sulphur, in the formation of acid mine drainage, and in the extraction of metals by bacterial leaching. Many researchers have studied the kinetics of dissolution, and the rate of dissolution has …
suitable for measuring incorporation of 3sS into pyrite and elemental sulfur during 35S0,2- reduction measurements in salt marsh sediments. Failure to explicitly measure the formation of 35S-labcled pyrite can result in the rate of sulfate reduction being underestimated by 2-fold to lo-fold or more.
Pyrite Group. The isometric (cubic) polymorph of orthorhombic marcasite. 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 many cases lead to ...
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