Showing papers on "Sulfide published in 1981"

Conducting complexes of polyphenylene sulfides

Abstract: Poly(p‐phenylene) sulfide, poly(m‐phenylene) sulfide, and the newly synthesized polymer poly(thio‐2,8‐dibenzothiophenediyl) have been treated with strong electron acceptors (AsF5, SbF5) to form conducting complexes with p‐type electronic conductivities up to 3 S/cm. Near IR to UV absorption spectra and temperature‐dependent conductivity measurements suggest a localization of charge carriers even at high doping levels. Elemental analysis and IR spectroscopy demonstrate that heavy exposure to AsF5 causes substantial changes in the backbone structure of these polymers. The dopant appears to predominantly induce the formation of carbon–carbon bonds bridging the sulfur linkages to form thiophene rings. This chemical modification enhances the conductivity of the complex and, in the case of poly(m‐phenylene), is shown to be an actual prerequisite for achieving high conductivity.

Use of reduced sulfur compounds by Beggiatoa sp.

Abstract: A strain of Beggiatoa cf leptomitiformis (OH-75-B, clone 2a) was isolated which is unique among reported strains in its ability to deposit internal sulfur granules from thiosulfate It also deposited these characteristic granules (as all BEggiatoa species do) from sulfide In cultures where growth was limited by exhaustion of organic substrates, these granules generally comprised about 20% of the total cell weight With medium containing acetate and thiosulfate, no measurable utilization of thiosulfate or deposition of elemental sulfur (S0) took place until after the exponential growth phase Neither sulfide nor thiosulfate added an increment to heterotrophic growth yield except for the weight of the deposited S0 The deposition of S0 from thiosulfate was probably a disproportionation in which S0 and sulfate were produced in a 1:1 ratio Some of the S0 was further oxidized to sulfate No autotrophic or mixotrophic growth was demonstrated for this strain When inoculated in small, well-dispersed quantities into yeast extract medium, this strain grew only after long lags Addition of the enzyme catalase eliminated initial lags and increased growth rates slightly In contrast, catalase had no influence on growth rate when added to mineral medium containing acetate In yeast extract medium, the inhibition of growth rate was presumably because of peroxides Addition of thiosulfate was almost as effective as catalase in eliminating this inhibition The S0 granules which, in this case, were deposited during the exponential growth phase, appeared to be partly responsible for this relief This strain of Beggiatoa sp remained active for at least 5 days under strictly anaerobic conditions, and under those conditions, it increased its dry weight by about 25-fold Anaerobic "growth" and maintenance required the presence of an energy source, such as acetate When cells containing much internal S0 were transferred to an organic anaerobic medium, a substantial portion of the internal S0 was eventually converted to sulfide

Sulfur isotopic studies of the Dunka Road Cu-Ni deposit, Duluth Complex, Minnesota

Abstract: The Dunka Road deposit is one of a series of Cu-Ni occurrences located within troctolitic rocks of the southern portion of the Duluth Complex, Minnesota. Sulfide minerals, principally pyrrhotite, chalcopyrite, cubanite, and minor pentlandite occur interstitially with silicate minerals and average about 2 volume percent in ore-grade horizons. Areas of sulfide concentrations in excess of 1 to 2 percent occur erratically throughout the troctolitic sequence but are in general concentrated near the basal contact with rocks of the metasedimentary Virginia Formation.The delta 34 S values of sulfides in the troctolites range from 0.2 to 15.8 per mil, with an average value near 7.5 per mil. Pyrrhotite in the underlying Virginia Formation hornfels and pyrite from unmetamorphosed Virginia Formation are characterized by a similar range in delta 34 S values. The high positive delta 34 S values and similarity to values found in the Virginia Formation strongly suggest that most of the sulfur in the Dunka Road deposit was derived from the breakdown of pyrite in the Virginia Formation. The sulfur isotopic compositions of minerals in the troctolites show no consistent lateral or vertical trends and are in general characterized by a high degree of variability. Such fluctuations in delta 34 S values indicate that sulfur isotopic homogenization was not attained throughout the troctolitic sequence.Several mechanisms may have contributed to the variations in delta 34 S values found within the troctolites, including mixing of sedimentary and igneous sulfur, assimilation of sedimentary sulfur characterized by variable delta 34 S values, fractionation caused by fluctuations in oxidation states during sulfur volatilization and assimilation, and periodic introduction of isotopically distinct magma batches. In light of the erratic sulfide mineral and delta 34 S distributions, the predominant mechanism is thought to be the introduction of both isotopically and spatially variable country rock sulfur into crystallizing troctolitic magma.

Reduction of sulfur compounds in the sediments of a eutrophic lake basin.

Abstract: Concentrations of various sulfur compounds (SO42−, H2S, S0, acid-volatile sulfide, and total sulfur) were determined in the profundal sediments and overlying water column of a shallow eutrophic lake. Low concentrations of sulfate relative to those of acid-volatile sulfide and total sulfur and a decrease in total sulfur with sediment depth implied that the contribution of dissimilatory sulfur reduction to H2S production was relatively minor. Addition of 1.0 mM Na235SO4 to upper sediments in laboratory experiments resulted in the production of H235S with no apparent lag. Kinetic experiments with 35S demonstrated an apparent Km of 0.068 mmol of SO42− reduced per liter of sediment per day, whereas tracer experiments with 35S indicated an average turnover time of the sediment sulfate pool of 1.5 h. Total sulfate reduction in a sediment depth profile to 15 cm was 15.3 mmol of sulfate reduced per m2 per day, which corresponds to a mineralization of 30% of the particulate organic matter entering the sediment. Reduction of 35S0 occurred at a slower rate. These results demonstrated that high rates of sulfate reduction occur in these sediments despite low concentrations of oxidized inorganic compounds and that this reduction can be important in the anaerobic mineralization of organic carbon.

The formation of the volcanic-hosted massive sulfide ore deposit at Rosebery, Tasmania

Abstract: The Rosebery pyritic zinc-lead-copper-silver-gold orebody occurs in dominantly felsic volcanic rocks of Cambrian age in western Tasmania. Ore formation occurred in a marine environment following eruption of a thick pyroclastic unit consisting mainly of welded, ashflow tuffs, and subsequent subsidence. The main orebody consists of a discontinuous massive sulfide horizon and in the southern part of the mine there is a generalized metal zonation with a lower and central Cu-Fe-rich zone surrounded and overlain by Zn-Pb-Ag-rich ore. Barite-sulfide ore occurs as separate lenses higher in the sequence separated from the sulfide orebody by unmineralized, cleaved siltstone.The orebody is underlain by an extensive zone of alteration marked by depletion of Na and Sr and enrichment in Rb, K, Mg, Mn, and H 2 O. The pyrite and chalcopyrite content of the altered footwall tuff and the Co content of the pyrite is highest beneath the Fe- and Cu-rich zones in the sulfide orebody and a feeder is inferred in this area.The delta 34 S values for sulfides in the sulfide orebody are higher in the richest Zn-Pb-Ag ore (>14.1ppm) than the Fe-Cu ore (>7.8ppm), a pattern paralleled by a decrease in the Fe/Fe + Mg + Mn ratio of chlorite and a decrease in the FeS content of sphalerite. The delta 34 S values for sulfides in the barite ore are even higher (14.5 to 19.8ppm) and the FeS content of sphalerite lower. Barite throughout the barite and sulfide orebodies is fairly constant between 34.6 and 41.2 per mil, but that in the sulfide ore appears to be epigenetic. The delta 34 S values for barite-sulfide pairs indicate a temperature range of 255 degrees to 298 degrees C for the barite orebody, but the temperature of barite ore formation was probably about 250 degrees C.The use of delta 34 S values for sulfides as stratigraphic markers indicates that the sulfide orebody is diachronous. It is possible to account for the metal and delta 34 S distribution by assuming that the ore solutions are buoyant on reaching the sea floor during the Fe- and Cu-rich phases but show reversing buoyancy during the Pb-Zn-rich phase.The coexisting arsenopyrite-pyrite-chlorite-quartz assemblage in the sulfide orebody defines a range of aO (sub 2 (super -) ) T conditions using the six-component solid solution chlorite model of Walshe and Solomon (1981). The maximum indicated temperature of 300 degrees C is consistent with the minimum temperature required by iron and copper solubilities. However, the chlorite compositions may be postdepositional, as seems to be the case for the FeS contents of sphalerite. The delta 34 S (sub Sigma S) for the sulfide orebody is probably derived by almost complete reduction of Cambrian seawater sulfate mixed with sulfur leached from underlying rocks. The delta 34 S values for the barite orebody may represent partial reduction of seawater sulfate.The ore fluid is supposed to have been generated by convective circulation of seawater in a rock pile heated by a Cambrian granitoid pluton.

Evidence for Coexistence of Two Distinct Functional Groups of Sulfate-Reducing Bacteria in Salt Marsh Sediment

Abstract: Oxidation of acetate in salt marsh sediment was inhibited by the addition of fluoroacetate, and also by the addition of molybdate, an inhibitor of sulfate-reducing bacteria. Molybdate had no effect upon the metabolism of acetate in a freshwater sediment in the absence of sulfate. The inhibitory effect of molybdate on acetate turnover in the marine sediment seemed to be because of its inhibiting sulfate-reducing bacteria which oxidized acetate to carbon dioxide. Sulfide was not recovered from sediment in the presence of molybdate added as an inhibitor of sulfate-reducing bacteria, but sulfide was recovered quantitatively even in the presence of molybdate by the addition of the strong reducing agent titanium chloride before acidification of the sediment. Reduction of sulfate to sulfide by the sulfate-reducing bacteria in the sediment was only partially inhibited by fluoroacetate, but completely inhibited by molybdate addition. This was interpreted as showing the presence of two functional groups of sulfate-reducing bacteria—one group oxidizing acetate, and another group probably oxidizing hydrogen.

Precious metals in the Jimberlana Intrusion, Western Australia; implications for the genesis of platiniferous ores in layered intrusions

Abstract: A neutron activation study of the distribution of Ir, Pd, and An in the Jimberlana Intrusion has shown that Pd and Au partition strongly into the sulfides. The Pd content of sulfides is governed, to a large degree, by the R factor, a measure of the amount of silicate liquid in equilibrium with the sulfide melt. The Pd content of the sulfide horizons from the center of the Jimberlana Intrusion is high but appreciably less than that of the Merensky Reef and the Pt horizon of the Stillwater Complex. The comparatively low Pd content of the Jimberlana sulfides is believed to be due to the sulfides having reached equilibrium with a smaller volume of silicate liquid than the Pt-rich sulfides of the Bushveld and Stillwater Complexes.At the margin of Jimberlana the sulfide content of the rocks may be as high as 10 percent. These sulfides have precipitated rapidly, resulting in a very low R factor and consequently they have anomalously low precious metal contents.Variations in the Ir content of rocks are independent of the presence of sulfides in the Jimberlana Intrusion. This may have resulted from the f (sub O 2 ) of the magma being less than that of the Ir 2 S 3 /Ir buffer allowing Pd, but not Ir, to enter the sulfide melt.

Precious metals in volcanic peridotite-associated nickel sulfide deposits in Western Australia; II, Distribution within the ores and host rocks at Kambalda

Abstract: A detailed study of the distribution of Pd, Ir, and Au in the sulfide component of contact ore layers at Lunnon shoot has shown consistent differences between the matrix and massive layers and significant lateral variation within them. Palladium values in sulfides increase upward in ore sections, and when average values are compared with those predicted by the relationship between Pd and Ni in mined ore (Ross and Keays, 1979), loss of Pd is indicated. The Pd-Au-Cu-enriched footwall sulfide stringers are believed to be the principal repository of remobilized Pd. Iridium has a more uniform distribution and there is no evidence of important loss or gain from contact ore, even though massive layer sulfides contain more Ir at nearly all sample locations. Average values of Au are higher in matrix layer sulfides and some loss of Au from contact ore into footwall stringers, and perhaps more distant sites, is likely. If it is assumed that the distribution of these metals, and of Ni and Cu, was uniform during emplacement of sulfide melt, their present distribution can be attributed to the following processes. Redistribution of Ir could have occurred during igneous cooling in the presence of a high thermal gradient at the base of the komatiitic volcanic pile and could have been accompanied by some movement of Pd in areas of active stress. Most redistribution of Pd is attributed to stress during the existence of metamorphic monosulfide solid solution, and significant redistribution of Cu may also have been induced by stress. The circulation of latestage sulfur-bearing solutions through contact ore layers (Seccombe et al., 1981) could have transferred Pd, Au, and Cu from contact sulfides (particularly from the more permeable massive layer) to footwall stringers and resulted in the close association of anomalous values of Au and Cu. Transfer of about 5 percent of the S in the matrix layer to the massive layer by these solutions would account for the consistently higher Ni content of the matrix layer and development of secondary pyrite in the massive layer.Analyses of sulfide mineral separates from several shoots have consistently shown that pentlandite is the dominant host for Pd; Ir is more uniformly distributed with higher values in pyrite; and chalcopyrite (and perhaps pyrite) is the most important host for Au. Concentrates of secondary pyrite appear to have normal values, which suggests some movement of Ir during its development. The precious metals appear to be uniformly distributed through sulfide mineral hosts, but observed variation in ore sections and layers requires that their abundance in the preferred sulfide host must vary considerably.Further work has strengthened the conclusion of Ross and Keays (1979) that olivine in the original komatiitic magmas was the principal host for Ir and the liquid component was the principal host for Pd. Olivine control lines for Pd and Ir in primary melts predict values at lower MgO in good agreement with those in hanging-wall basalts at Kambalda. At higher MgO they agree closely with the most recent estimate for pyrolite and a chondritic Pd:Ir ratio of about unity. These predicted values result in a substantial increase in Pd:Ir with decreasing MgO. Results from Kambalda and other Ni sulfide deposits indicate that the Pd:Ir ratio of the sulfide melt may approximate that of the coexisting silicate melt even though absolute values may vary widely. This variation exceeds that expected from the relative volumes of silicate and sulfide melt and may result from differences in factors such as f (sub s 2 ) and f (sub o 2 ) when immiscible sulfides formed. Measurements of Pd and Ir offer scope for defining the MgO contents of primary silicate melts associated with immiscible sulfides and may allow a more precise definition of f (sub s 2 ) (and perhaps f (sub o 2 ) ) during formation of immiscible sulfide melts.

Sulfide and Methane Formation in Soils and Sediments

Abstract: In suspensions of Crowley soil, and under conditions of controlled pH and redox potential, sulfide formation took place in the pH range 5.5 to 8.5 and in the redox potential range −175 to −350 mV. At each pH tested, the rate of sulfide formation increased with a decrease of the redox potential. The order of reaction of sulfide formation was found to be ill defined. The optimum pH for both sulfide and methane formation was 6.7. Empirical data were in agreement with thermodynamically predicted values. Nitrate reduction, manganous and ferrous ion, and sulfide and methane formation occurred sequentially according to thermodynamic principles. However, some overlap did occur in the later stages of the formation of manganous, ferrous, and sulfide ions, possibly due to delayed dissolution of manganese and iron compounds. A small amount of methane was formed at redox potentials as high as −120 mV. Nitrate and sulfate or their reduction products repressed methane formation. The effect of nitrate appeared to be twofold: first, it delayed methane formation until the reduction of nitrate was complete and the redox potential was lowered sufficiently for further anaerobic reactions to proceed. Secondly, it exerted a toxic effect on methane formation. The major effect of sulfate appeared to be toxic, although a slight increase of the redox potential did occur at high sulfate concentrations.

X-ray Absorption Spectroscopic Investigation of Trace Vanadium Sites in Coal

Abstract: X-ray absorption spectroscopy was used to probe the chemical and structural environment of vanadium in coal. It was found that vanadium exists in at least two environments, in both of which it was coordinated to oxygens. There was no evidence of vanadium in nitrogen (porphyrin) or sulfide environments. It was also found that the vanadium environments in the raw coal did not survive unchanged in a liquefaction process. These findings have implications for coal cleaning processes and for trace element release into the liquefaction process stream.

Geochemistry of komatiites from Kambalda, Western Australia; I, Chalcophile element depletion, a consequence of sulfide liquid separation from komatiitic magmas

Abstract: The type examples of Archean volcanic peridotite-associated Ni sulfide deposits occur at or toward the base of the ultramafic lava pile at Kambalda, Western Australia. Spinilex-textured komatiites, considered to represent silicate liquids derived from the original magma, are significantly depleted in chalcophile elements throughout the entire ultramafic sequence relative to unmineralized and poorly mineralized komatiites elsewhere and to a theoretically modeled sulfide-undersaturated komatiite system.This depletion is not attributed to postformational modification of the komatiites by sea-floor alteration or metamorphism, although very low sulfur contents in the same rocks probably result from such processes. The depletion is best interpreted as the result of scavenging of metals by sulfide liquid in equilibrium with the silicate magma, implying that all the silicate magma now represented by the ultramafic sequence equilibrated with sulfide liquids at the magmatic stage. These results provide convincing evidence against formation of the sulfide ores by in situ sulfide separation from the thick komatiitic peridotitc host. The magnitude of the depletion in the spinilex-textured komatiite divisions of the peridotitc hosts is much less than that expected for such an origin, but for the entire sequence it is greater than that expected from metal partitioning relations and mass balance calculations for the volume and composition of the ultramafic sequence and the volume of associated sulfides. This suggests that a proportion of the sulfide liquid that formed from the ultramafic magma(s) was lost from the magmatic system prior to extrusion. Such loss is a natural consequence of models for ascent and eruption of sulfur-rich komatiitic magmas that involve prior concentration of sulfides (plus olivine) in high-level magma chambers or separation and segregation of sulfide liquid during ascent from the upper mantle.

Redistribution of ore elements during serpentinization and talc-carbonate alteration of some Archean dunites, Western Australia

Abstract: Serpentinization of barren and weakly mineralized Archean dunites in the Yilgarn Block, Western Australia, occurred without any apparent loss of major components, including the important ore elements Ni and Fe. Sulfur addition during initial serpentinization resulted in about 30 percent of original silicate Ni being redistributed to newly formed sulfide by reactions similar to: olivine + water = lizardite + brucite and lizardite + brucite + S = lizardite + brucite + magnetite + heazlewoodite + water + H 2 . Serpentinization at a higher temperature or metamorphism of the lizardite-bearing assemblage formed antigorite serpentinite in which up to 60 percent of bulk rock Ni is incorporated in sulfide form: lizardite + brucite + magnetite + heazlewoodite + CO 2 + S = antigorite + magnesite + magnetite + Ni sulfide + water + H 2 .Complete CO 2 metasomatism resulted in talc-carbonate rocks with still more Ni redistributed to sulfides, and the formation of some Fe sulfide: antigorite + magnesite + magnetite + Ni sulfide + CO 2 + S = talc + magnesite + pentlanditc + Fe sulfide + or - magnetite + water + O 2 . In areas where low S activity precluded sulfide formation, Ni was strongly enriched in magnetite in serpentinites or talc in talc-carbonate rocks.Preexisting disseminated Ni sulfides of magmatic origin were significantly upgraded by serpentinization. Up to 30 percent of sulfide Ni in ores averaging about 0.7 percent Ni is of metamorphic origin, and this proportion may be higher in talc-carbonate ores. Fe sulfides of metamorphic origin form up to 20 percent of the total sulfide fraction in talc-carbonate-altered disseminated Ni ores, so that about half the sulfide content of these ores may be metamorphically derived by redistribution of elements originally held in olivine.

Acute renal failure associated with barium chloride poisoning.

Abstract: Excerpt Barium salts are an infrequent cause of poisoning. Because the acid-soluble barium salts (acetate, carbonate, chloride, hydroxide, nitrate, and sulfide) are highly toxic, fatalities have oc...

Stabilized polyphenylene sulfide and method for producing same

Abstract: A stabilized polyphenylene sulfide is provided which comprises a recurring unit wherein the average n between foreign units is greater than about 5, and which further comprises about 0.05 to about 10 mole% per phenylene sulfide unit of an aromatic constituent chemically bonded with said polyphenylene sulfide chain, said aromatic consituent containing an electron attractive group selected from the group consisting of -halogen, -SO 2 -, -CO-, -NO., -SO 3 R, -COOR, wherein R is H, lower aliphatic hydrocarbon groups, aromatic hydrocarbon groups or alkaline metals, and -CONH-, and said stabilized polyphenylene sulfide has a melting point in the range of about 250°C to about 350°C. A preferred method for preparing said stabilized polyphenylene sulfide comprises preparing a polyphenylene sulfide consisting mainly of a recurring unit wherein the degree of polymerization of said recurring unit is greater than about 20, and reacting said polyphenylene sulfide with about 0.05 to about 20 mole% per said phenylene sulfide unit of a halogenated aromatic compound having an electron attractive group.

A kinetic study on nonoxidative dissolution of sphalerite in aqueous hydrochloric acid solutions

Abstract: The nonoxidative leaching of sphalerite in aqueous acidic solutions was studied from a kinetic point of view. Also the selective nonoxidation leaching in a hydrochloric acid solution containing a large amount of sodium chloride was examined for a Pb-Zn sulfide bulk concentrate. The dissolution rates of sphalerites from five different mines appeared to be controlled by a chemical reaction on the surface of sphalerite. The dissolution rate of sphalerite is of the first order with respect to the hydrogen ion activity of the solutions. It is also considerably affected by the iron content of the sphalerite sample; a linear relationship was observed between iron content of the sphalerite and its dissolution rate. The addition of sodium chloride to the hydrochloric acid solutions greatly enhanced dissolution rates. Compared to the dissolution rates of galena, which were reported in a previous paper, the dissolution rates of sphalerite were found to be far slower. The difference in the dissolution rates between these two minerals becomes greater with the addition of sodium chloride to the hydrchloric acid solutions. Based on these findings, the selective leaching of Pb-Zn bulk concentrate in a hydrochloric acid solution containing a large amount of sodium chloride was examined. The experimental results clearly showed that the galena was selectively leached, leaving a residue of sphalerite.