Showing papers on "Sulfide published in 1979"

An electrochemical model of the induced‐polarization phenomenon in disseminated sulfide ores

Abstract: A disseminated sulfide ore is idealized by a system of electronically conducting metallic spheres randomly dispersed in an electrolytically conducting host medium. When an external electric field is applied, the transport of cations and anions in the interphase region near the metal‐electrolyte interface will involve both drift and diffusion flux densities. The flow of ions to or from the metal‐electrolyte interface causes an excess or deficit of inactive ions to accumulate there, since the metal is neither a source nor sink for these ions. These inactive ions are loosely held to the metallic particles by image forces, and concentration gradients build up which oppose the migration of these ions due to electric fields. In addition to the inactive anions and cations, a minor concentration of active cations is assumed to exist in the electrolytic medium, and the electric fields at the electrolyte‐metal interface cause these to engage in electrochemical reactions making possible charge transfer across the in...

Microbial Transformations of Sulfur-Compounds in a Stratified Lake (Solar Lake, Sinai)

Abstract: Microbiological and chemical aspects of the sulfur cycle were studied in the chemocline of a tropical salt lake. Oxygen and sulfide coexisted in a O-lo-cm layer which migrated up and down during a diurnal cycle. Sulfide was rapidly oxidized by oxygen, with a half-life of 5-10 min, to produce mainly sulfate and thiosulfate. Thiosulfate and elemental sulfur had concentration maxima in the chemocline while polysulfide was abundant throughout the sulfide zone. Radiotracer experiments showed that the elemental sulfur was produced by anoxygenic photosynthesis in cyanobacteria. The elemental sulfur was further oxidized or again reduced, depending on the presence or absence of oxygen. Cyanobacteria in the che- mocline shifted between anoxygenic photosynthesis in the morning and oxygenic photosyn- thesis in the afternoon. A high dark CO, fixation was found in the chemocline which could be stimulated by sulfide, elemental sulfur, and thiosulfate. The oxidation rate of sulfide in the chemocline was dependent on the presence of bacteria.

Redox species in a reducing fjord: equilibrium and kinetic considerations☆

Abstract: In June 1977 ten redox sensitive chemical species were determined in the oxidizing and reducing waters of Saanich Inlet, British Columbia. An oxygen-hydrogen sulfide interface was found at a depth of 130 m. The concentrations of the oxidized species: oxygen, nitrate, iodate, and chromate, and the reduced constituents: hydrogen sulfide, ferrous iron, and ammonia reached background or near background levels at this depth. Three reduced constituents, manganese (II), chromium (III), and iodide existed metastably in the oxic layer. Thermodynamic calculations of pe indicate that the redox couples in the anoxic waters approach equilibrium with each other while those in the oxygenated waters are far from equilibrium. A time-dependent diffusion model is used to determine the removal rate constants for Mn2+ and Cr(III) in the linear temperature-salinity region surrounding the oxygen-hydrogen sulfide interface (130 to 115 m). In this region I− is conservative within the error of our measurements over the period of anoxia in the inlet (estimated to be 3 to 6 months). The residence times of Cr(III) and Mn2+ in the oxic layer are one to three weeks and about two days, respectively. We argue that the dominant manganese removal mechanism is by oxidation, resulting in a calculated oxidation rate constant for Mn2+ five orders of magnitude greater than published laboratory values and widely different from previous field estimates. The rapid oxidation kinetics in Saanich Inlet are probably caused by bacterial catalysis near the oxygen-hydrogen sulfide interface.

Hydrogen sulfide poisoning.

Abstract: Poisoning by hydrogen sulfide has been recognized as an occupational hazard for at least two centuries. The development of alternative sources of energy in North America may increase the incidence of this medical emergency in the future. Until recently, no specific antidote to sulfide was recognized. We have compared sulfide poisoning to cyanide poisoning and documented recent findings that indicate many similarities between the two. The therapeutic induction of methemoglobinemia, as by the intravenous administration of sodium nitrite, has both protective and antidotal effects against sulfide as well as against cyanide in laboratory animals. This procedure has been used successfully in at least one severe human case of sulfide poisoning. Industries at risk should be prepared to initiate this form of therapy in addition to the usual measures for cardiopulmonary resuscitation. No evidence exists to suggest that sulfide poisoning results in an impairment of the oxygen transport capability of blood. On the other hand, some victims of hydrogen sulfide poisoning exhibit frank cyanosis, suggesting that the respiratory tract obstruction is more common in this condition than is generally recognized. Suction of the upper tract and the administration of oxygen may be important ancillary procedures to the administration of sodium nitrite.

Separation of Toxic Heavy Metals by Sulfide Precipitation

Abstract: Sulfide precipitation with Na2S is found to be highly effective to obtain a high degree of separation of heavy metal cations (Cd, Zn, Cu, and Pb) and of the oxyanions of arsenic and selenium from complex wastewaters. The metal separation characteristics are evaluated with a dilute synthetic mixture and with an actual copper smelting plant wastewater. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at sulfide dosages about 60% of the theoretical values and at a final pH greater than 8.0. The removals of Cd, Zn, and Cu from the actual wastewaters are greater than 99%, and As and Se removals are 98 and >92%, respectively. Cd, Cu, and Zn concentrations in the range of 0.05 to 0.1 mg/1 can be achieved with sulfide precipitation. The metal separations and settling rates obtained with conventional hydroxide precipitation (lime) are considerably lower than those obtained with sulfide precipitation.

Effect of inorganic sulfide on the growth and metabolism of Methanosarcina barkeri strain DM.

Abstract: Minimal growth of Methanosarcina barkeri strain DM occurred when sulfide was omitted fromthe growth medium, and addition of either sodium sulfate or coenzyme M to sulfide-depleted media failed to restore growth. Optimal growth occurred in the presence of 1.25 mM added sulfide, giving a molar growth yield (YCH4) of 4.4 mg (dry weight) of cells per mmol of CH4 produced. Increasing sulfide to 12.5 mM led to decrease in YCH4 (1.9 mg [dry weight]/mmol of CH4), in the specific growth rate and in be intracellular levels of adenosine triphosphate. However, the specific rate of methane production increased. The data suggested that at elevated sulfide levels (12.5 mM) the decrease in YCH4 might be a result of an increase in the relative energy needed for maintnenace and of uncoupling of growth from energy production.

Kinetics and mechanism of the oxidation of sulfide by oxygen: catalysis by homogeneous metal-phthalocyanine complexes

Abstract: The kinetics of the catalyzed autoxidation of hydrogen sulfide to sulfur, thiosulfate, and sulfate in aqueous solution has been investigated potentiometrically over the pH range 5-12 The catalytic effects of cobalt(II), nickel(II), and copper(I1) 4,4’,4”,4”'- tetrasulfophthalocyanine have been determined, and differences in catalytic ability have been explained in terms of relative capacity of the octahedral complexes to reversibly bind oxygen Kinetic data have been analyzed in terms of a bisubstrate Michaelis-Menton rate law The rate law and other data indicate that the catalyzed reaction proceeds via the formation of a tertiary-activated complex in which HS^- and O_2 reversibly bind with CoTSP^(2-) pH variations have been explained in terms of the acid dissociation of H_2S, general base catalysis, and deprotonation of pyrrole nitrogens within the phthalocyanine ring

Effects of sulfide and acetylene on nitrous oxide reduction by soil and by Pseudomonas aeruginosa

Abstract: The production and reduction of nitrous oxide (N2O) after the addition of N2O, nitrite (NO2−), or nitrate (NO3−) was studied in non-sterile soil, in sterilized soil inoculated with Pseudomonas aeruginosa, and in washed cell suspensions of this organism. Sodium sulfide (8 μmol S2− mL−1 or g−1) inhibited N2O reduction markedly in cell suspensions and also in soil, an effect which may cause sulfidic habitats to act as sources of N2O. Sodium thiosulfate (up to 64 μmol S2O32− g−1) showed no such effect. Acetylene (0.02 atm C2H2) completely inhibited the reduction of N2O by soil, but the combination of C2H2 with 8 μmol S2− g−1 permitted the complete reduction of 2 μmol added N2O g−1 within 3 days under the most favourable conditions. Under the same conditions, 8 μmol S2O32− g−1 permitted complete reduction of the N2O within 6 days. The rate of such reduction of N2O was decreased, but not inhibited completely, by raising the C2H2 concentration to 0.11 atm. The data have important implications for the effectivene...

Sulfide Induced Corrosion of Copper Nickel Alloys

Abstract: The susceptibility of Cu-Ni alloys to accelerated corrosion in sea water containing low sulfide concentrations has been investigated. Test alloys included wrought 90/10 Cu-Ni, 70/30 Cu-Ni ...

The Corrosion of Cu-Ni Alloys 706 and 715 in Flowing Sea Water. II – Effect of Dissolved Sulfide

Abstract: The corrosion of 90:10 Cu:Ni and 70:30 Cu:Ni alloys in sulfide polluted flowing sea water has been studied as a function of sulfide concentration. The experimental techniques used include small amplitude cyclic voltammetry, AC impedance measurements, large amplitude cyclic voltammetry, and extensive surface examination by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction, and Auger electron spectrometry (AES). It is shown that the presence of sulfide induces a loss in passivity of the alloy surface due to the formation of cuprous sulfide as the principal corrosion product. Furthermore, accelerated corrosion of these materials in sulfide polluted sea water appears to arise from a shift in the corrosion potential to sufficiently active values that hydrogen evolution becomes a viable cathodic process.

Siroheme sulfite reductase isolated from Chromatium vinosum. Purification and investigation of some of its molecular and catalytic properties

Abstract: Cells of the phototrophic bacterium Chromatium vinosum strain D were shown to contain a siroheme sulfite reductase after autotrophic growth in a sulfide/bicarbonate medium. The enzyme could not be detected in cells grown heterotrophically in a malate/sulfate medium. Siroheme sulfite reductase was isolated from autotrophic cells and obtained in an about 80% pure preparation which was used to investigate some molecular and catalytic properties of the enzyme. It was shown to consist of two different types of subunits with molecular weights of 37,000 and 42,000, most probably arranged in an α4β4-structure. The molecular weight of the native enzyme was determined to 280,000, 51 atoms of iron and 47 atoms of acid-labile sulfur were found per enzyme molecule. The absorption spectrum indicated siroheme as prosthetic group; it had maxima at 280 nm, 392 nm, 595 nm, and 724 nm. The molar extinction coefficients were determined as 302×103 cm2xmmol-1 at 392 nm, 98×103 cm2 xmmol-1 at 595 nm and 22×103 cm2x-mmol-1 at 724 nm. With reduced viologen dyes as electron donor the enzyme reduced sulfite to sulfide, thiosulfate, and trithionate. The turnover number with 59 (2 e-/enzyme moleculexmin) was low. The pH-optimum was at 6.0. C. vinosum sulfite reductase closely resembled the corresponding enzyme from Thiobacillus denitrificans and also desulfoviridin, the dismilatory sulfite reductase from Desulfovibrio species. It is proposed that C. vinosum catalyses anaerobic oxidation of sulfide and/or elemental sulfur to sulfite in the course of dissimilatory oxidation of reduced sulfur compounds to sulfate.

Preliminary Measurements of Biogenic Sulfur-Containing Gas Emissions From Soils

Abstract: Some of the results of a preliminary field study using a dynamic emission chamber technique to determine the composition and flux of sulfur gases from a variety of soils within the Electric Power Research Institute (EPRI) Sulfate Regional Experiment (SURE) regional study area in eastern United States are reported. The measured sulfur flux at each of the six sampling sites, when projected to an annual average (unadjusted for the seasonal ranges of ambient temperature), ranged from 0.002 to 152g S/m/sup 2//yr. The highest measured sulfur fluxes of 381, 271, 201, and 137 g S/m/sup 2//yr were found in several small, unique areas at Cox's Landing tidal flat. The relatively unpolluted saline marshy area of Core Sound, Cedar Island, NC may represent a more significant area-wide source of biogenic sulfur flux than did Lockwood Folly Inlet, NC. Further studies will be conducted in these areas. Most published discussions of the nature, sources, and fate of biogenic sulfur compounds have proposed H/sub 2/S as the primary product of biogenic activity. Other authors have suggested that carboxyl sulfide and dimethyl sulfide should be included. The data reported herein suggest that a larger array of biogenic sulfur-containing compounds should be considered. In fact, formore » some soils and conditions, CS/sub 2/ or dimethyl disulfide emissions may provide a sulfur contribution equal to or greater than of H/sub 2/S.« less

Studies of the base metal sulfide deposits at McArthur River, Northern Territory, Australia; II, The sulfide-S and organic-C relationships of the concordant deposits and their significance

Abstract: Common to all models proposed for the origin of the concordant deposits at McArthur River is the formation of laminar and framboidal pyrite (Py 1 ) during early diagenesis by microbial sulfate-reducing reactions. In modern anoxic sediments the formation of diagenetic pyrite by these reactions produces a strong positive correlation between sulfide S and organic C, such that the frequency distributions of sulfide-S to organic-C ratios (S/C) in the sediments are unimodal and symmetrical. Ancient and unmineralized anoxic sedimentary rocks also have unimodal and symmetrical S/C frequency distributions indicating that the processes accompanying the lithification of anoxic sediments do not destroy the sulfide-S and organic-C fingerprint of diagenetic pyrite formation.The S/C frequency distributions of the concordant Ridge II and H.Y.C. (Here9s Your Chance) deposits at McArthur River are unimodal but asymmetrical, suggesting a model in which the deposit of galena and sphalerite modified the sulfide-S and organic-C fingerprint of diagnetic pyrite formation by altering a symmetrical distribution to an asymmetrical one. The model is supported by the sulfide-S and organic-C relationships of the H.Y.C. deposit. Poorly mineralized samples in the deposit, containing mostly pyrite, have a near-symmetrical unimodal S/C frequency distribution like unmineralized anoxic sedimentary rocks. On the other hand, well-mineralized samples, containing galena and sphalerite as well as pyrite, have much higher S/C ratios than the poorly mineralized samples, and these ratios constitute the high S/C tail of the overall S/C frequency distribution of the H.Y.C. deposit. The model is not supported by the sulfide-S and organic-C relationships of the concordant Ridge II deposit which show that both the poorly and well-mineralized samples have similar unimodal and asymmetrical S/C frequency distributions. The different sulfide-S and organic-C relationships of the two deposits are attributed to the greater abundance of overgrowth pyrite (Py 2 ) in the Ridge II deposit.The different sulfide-S and organic-C relationships of the poorly and well-mineralized H.Y.C. samples are used to test the various mineralizing models previously proposed for the deposit. The only models which are consistent with the relationships are the epigenetic sulfate-reduction and syngenetic nonsulfide-exhalative models in which galena and sphalerite are deposited after Py 1 by reactions involving the oxidation of organic C in the host rocks and concurrent reduction (probably inorganic rather than microbial) of solution SO 4 (super -2) . The sulfide-S and organic-C relationships of the concordant Ridge II deposit are also consistent with these models. The relationships indicate that in the Ridge II deposit, the sulfate-reductions deposited galena, sphalerite, and some Py 2 in the well-mineralized samples and significant quantities of Py 2 in the poorly mineralized samples.