Contributions from pyrite

CONTRIBUTIONS FROM PYRITE. This coal has a significant amount of pyrite which may produce sulfur containing organic molecules during pyrolysis. 

Mineral matter may also contribute to the volatile matter by virtue of the loss of water from the clays, the loss of carbon dioxide from carbonate minerals, the loss of sulfur from pyrite (FeS2), and the generation of hydrogen chloride from chloride minerals as well as various reactions that occur within the minerals, thereby influencing the analytical data (Given and Yarzab, 1978). 

Due to contributions from mineral matter (pyrite being of great importance), no systematic correlation exists between coal rank and thermal... 

Resolution. The evolutions of H2S from aliphatic sulfides and from iron pyrite coincide to the extent that it was almost impossible to resolve the two peaks. However, since only a small fraction of the pyrite is reduced, it was possible to estimate the relative contribution of pyritic sulfur and sulfidic sulfur to the unresolved peaks. Somewhat better resolution was obtainable at slow rates of heating however, in these cases the overall recovery and the signal-to-noise ratio were reduced. The dependence of the resolution between two peaks on the rate of temperature programming a is given by Equation (38) ... 

In contrast to the of hydrothermal solution for the vein, that of pyrite in hydrothermally altered rocks (Shimanto Shale) varies very widely, ranging from —5%o to - -15%o. Based on the microscopic observation, pyrite with low values less than 0%o is usually framboidal in form, suggesting that low 8 S was caused by bacterial reduction of seawater sulfate. There are two possible interpretations of high 8 " S values (+10%o to - -15%o). One is the reduction of seawater sulfate in a relatively closed system. The other one is a contribution of volcanic SO2 gas. As noted already, volcanic SO2 gas interacts with H2O to form H2SO4 and H2S. value of SO formed by... 

Reductive dissolution of Fe oxyhydroxides holding sorbed As appears to explain the very large concentrations of As in water from wells drilled into alluvial sediments of the Brahmaputra and Ganges Rivers in Bangladesh and West Begal (Nickson et al 1998, 2000). Dissolved As has accumulated from the reduction of As-rich Fe oxyhydroxides formed upstream of the contaminated areas by weathering of As-rich base metal sulfides. The reduction is driven by sedimentary organic matter in the deposits. Release of As from oxidation of pyrite in shallow wells contributes little to the water contamination because any As(IV) released would be re-sorbed on Fe oxides formed in pyrite oxidation. 

In this case study, the selected phases are pyrite, amorphous FeS, calcite (present in limestones in the roof strata Fig. 5), dolomite (possibly also present in the limestones), siderite (which occurs as nodules in roof-strata mudstones), ankerite (present on coal cleats in the Shilbottle Seam), melanterite and potassium-jarosite (representing the hydroxysulphate minerals see Table 3), amorphous ferric hydroxide (i.e., the ochre commonly observed in these workings, forming by precipitation from ferruginous mine waters), and gypsum (a mineral known to precipitate subaqueously from mine waters with SO4 contents in excess of about 2500 mg/L at ambient groundwater temperatures in this region, and with which most of the mine waters in the district are known to be in equilibrium). In addition, sorption reactions were included in some of the simulations, to contribute to the mole transfer balances for Ca, Na, and Fe. 

The most widely applied activation procedure is that involving the use of copper(II) ions to enhance the floatability of some sulfide minerals, notably the common zinc sulfide mineral sphalerite.2 Sphalerite does not react readily with the common thiol collectors, but after being treated with small amounts of copper it floats readily owing to the formation of a surface layer of CuS." A similar procedure is often adopted in the flotation of pyrrhotite (FeS), pyrite (FeS2), galena (PbS) and stibnite (Sb2S3). In the context of coordination chemistry, the major contribution has been to the understanding of the chemistry involved in the deactivation of these minerals, a procedure often adopted in the sequential flotation of several minerals from a complex ore. 

Pyrite In air, burns to Fe203 and S02 in VM test, decomposes to FeS Increases heat of combustion ash weighs less than MM S from FeS2 contributes to VM... 

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