ウスタイトの還元速度と還元鉄性状に及ぼす還元ガス中の酸素と硫黄ポテンシャルの影響

The reduction of dense Wustite plate was investigated over the temperature range of 600 to 1200°C, using hydrogen containing hydrogen sulphide and water vapour of various contents in such proportions that metallic iron remains stable. Sulphur in the reducing gas affects remarkably the kinetics of the reduction of Wustite and the morphology of reduced iron. The following results were obtained.(1) In the reduction at 800 and 1000°C, sulphur in the reducing gas of content just below that for the formation of iron sulphide extensively enhances the reduction of Wustite due to the formation of porous iron rather than dense iron, and, conversely, sulphur of extremely low content compared with that in equilibrium with iron sulphide retards the reduction due to the formation of dense iron.(2) The addition of both water vapour and hydrogen sulphide to hydrogen stops the reduction at 600°C, in spite of their low concentrations.(3) In the reduction at 1000 and 1200°C, the reduction rate becomes smaller by the addition of sulphur, in which case the coarsening of metallic iron is observed.

Influences of water vapor and fly ash addition on NO and SO 2 gas conversion efficiencies enhanced by pulsed corona discharge

A study on the neutralization of sulfur compounds during the filtration combustion of model mixture compositions containing iron sulfide or copper sulfate by adding marble (CaCO3) was carried out. It has been experimentally shown that during burning model charge compositions with additions of both iron sulfide and copper sulfate, replacing chemically inert sapphire with marble leads to a decrease in combustion temperature by approximately 150–200 °C. At the same time, the content of CO2 in gaseous products increases, and the concentrations of CO and H2 decrease. The greatest effect on the absorption of sulfur-containing substances when adding marble was shown in experiments where sulfur was present in the fuel in sulfide form: the addition of 50% marble made it possible to capture 72% of the initial sulfur content, and for compositions with 90% marble in the charge, 85%. The absorption of sulfur compounds formed during the combustion of model mixture compositions with copper sulfate is much worse. When the charge contains 50% and 85% marble, sulfur-containing compounds were absorbed by only 19% and 24%, respectively.

The features of superficial phases (SPs) formation with different mineral buffers from metallic Fe and Cu films containing nanoparticles (NPs) of gold are studied. The data on gold occurrence forms in sulfide SPs are obtained by scanning probe microscopy (SPM), electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). SPM shows that metal films of gold, iron and copper obtained by magnetron sputtering on polished sulfide substrates of arsenopyrite (FeAsS) and chalcopyrite (CuFeS2) have a fractal nature. Under annealing, the fractal dimension (Df) of films varies in the interval 2.3-2.4, providing suggestion that the process of sulfidation of metal films proceeds by a partial ripening of metal grains and the formation of iron and (or) copper sulfides. A portion of Au NPs is "trapped" by growing sulfide micro- and nanophases (binding energy (BE) for XPS spectrum line Au 4f7/2 equal to 84.5±0.2 eV indicates the form Aunano). Other NPs are represented by spherical microsized gold-containing phases on the surface of sulfide substrates (the form Au°) formed by the self-assembly mechanism (BE=84.0±0.2 eV), and partially are chemisorbed on SPs displaying Au-S chemical bonding (the form Au+ with BE=85.0±0.2 eV).

Sulfur and iron analyses of marine archaeological wood in shipwrecks from the Baltic Sea and Scandinavian waters

The Ce1–xFexO2–x/2 solid solution was synthesized using a microwave-assisted hydrothermal route. The solubility limit corresponds to a Fe (x) content equal to 0.15. Our previous works showed also that isolated Fe3+ distorted octahedral sites and Fe3+ clusters are randomly distributed into the ceria network. Thermogravimetric analysis (TGA) under Ar/5%H2 revealed a higher reduction rate for Fe-substituted ceria with changes of slope and the appearance of pseudoplateaus around 400 and 550 °C. The first Fe K-edge X-ray absorption near-edge spectroscopy (XANES) spectra recorded at several temperatures up to 700 °C shift gradually to lower energies as the temperature increases, with the formation of metallic iron starting at 550 °C, as confirmed by X-ray diffraction analysis. Moreover, on the basis of the principal component factor analysis, three K-edge structures associated with three oxidation states of iron (Fe3+, Fe2+, and Fe0) have been distinguished during this temperature-programmed reduction. The second component attributed to Fe2+ is the most intense one around 500 °C. Beyond this temperature, the coexistence of the three oxidation states Fe3+/Fe2+/Fe0 has to be mentioned up to 650 °C, the temperature at which metallic iron is mainly stabilized. Ce LIII-edge and Fe K-edge XANES spectra recorded in quick extended X-ray absorption fine structure mode and at various temperatures show the progressive reduction of Ce4+ and Fe3+ starting beyond 250 °C, which is in good agreement with the change of slope observed on the TGA curves. The Ce LIII-edge XANES spectrum of pure CeO2 recorded at 700 °C under reducing atmosphere exhibits much less Ce3+ stabilized into the fluorite network than Fe-substituted ceria. Fe3+ ions randomly distributed into ceria strongly contribute to enhancing the Ce4+ reducibility properties. The Ce4+ reduction seems to appear at lower temperatures and is slower than the Fe3+ reduction, whose speed decreases around 400 °C. At this temperature, the Fe2+ and Fe3+ components dominate and the Ce3+ content remains high. However, a plateau with the stabilization of Ce4+/Ce3+ mixed valences around 500 °C appears where the Fe2+ contribution is also a maximum and the Fe reduction is slower. Because of the large content of either Ce3+ and Fe2+, a charge-transfer equilibrium Ce4+ + Fe2+ ⇔ Ce3+ + Fe3+ may occur at this temperature at which a change of slope on TGA curve also is observed with the appearance of a plateau at 550 °C associated with the Fe0 demixtion phenomenon. Then, after reaching the maximum Fe2+ rate, the Ce4+ reduction rate increases again up to 700 °C, the temperature at which all Fe atoms have been transformed into metallic iron.

SUMMARYHydrogen sulfide is formed from the meat of baby clams during canning. The amounts of hydrogen sulfide are usually below 50 mg%, which may be the minimum amount necessary to cause blackening. When hydrogen sulfide is produced in amounts more than 50 mg% (e.g. when the raw material is not fresh), blackening may be accelerated, or the canned baby clams may decompose and hydrogen sulfide concentration increase slightly during storage. The blackening is caused by the formation of copper sulfide and iron sulfide. Iron transferred to the intestine from the mud where the clams live, is involved in blackening. Also implicated is copper freed from hemocyanin in baby clam by boiling. Some phosphate compounds (0.270) are effective in decreasing the blackening.

Exploratory studies were made to determine the value of four potential catalysts in increasing the gas plating rate for nickel carbonyl. The catalysts studied were anhydrous ammonia, water vapor, oxygen, and hydrogen sulfide. No catalytic effect was observed for either ammonla alone or for water vapor alone. Oxygen was not tested alone. With hydrogen sulfide present in the 0.2 to 0.4% concentration range, significant improvement in plating rate was observed. The best results were obtained with mixtures of hydrogen sulfide and water vapor or mixtures of hydrogen sulfide and oxygen, using hydrogen sulfide concentrations of 0.2 to 0.8%, water vapor concentrations of 0.03 to 0.08%, and oxygen concentrations of 0.8 to 1.0%. The catalytic effect can also be used to reduce the temperature required s plating with nickel carbonyl. Using the hydrogen sulfide-oxygen mixture, nickel carbonyl gas plating was performed at room temperature on the following materials: iron, copper, aluminum, glass, paper, cardboard, cotton cloth, and cork. (auth)

The source and depositional environment of early Silurian iron formation in NW China: Constraints from element and isotope (Fe, C, O) geochemistry

Isothermal reduction of haematite carbon mixtures was investigated at temperatures 750–1100°C under inert atmosphere. Mass loss curves proved the stepwise reduction of haematite to metallic iron. The non-linear feature of haematite to magnetite reduction kinetics was observed and an activation energy of 209 kJ mol−1 was calculated. Irrespective of carbon-bearing material type, reduction rate of magnetite was linear. Activation energy values were calculated to be 293–418 kJ mol−1. Significant increase in the reduction kinetics in the last step (Wustite reduction) was observed and explained by the catalytic effect of freshly formed metallic iron. During the initial stages of wustite reduction, the activation energy values were calculated to be in the range of 251–335 kJ mol−1 for all carbon-bearing materials.

The mixtures of large- and small-particle α-Fe2O3 which are formed during the preparation of silica-supported iron-iridium catalysts with low concentrations of iridium in air are partially reduced by treatment in hydrogen at 270°C to Fe3O4 and iron (II). Increases in the iridium content of the bimetallic particles induces the formation of metallic iron when the catalysts are heated in hydrogen whilst catalysts with large concentrations of iridium are partially converted to iron-iridium alloys. Treatment of the catalysts containing metallic iron in carbon monoxide and hydrogen results in the formation of iron carbides.

Characterization of iron sulfides, determination of corrosion rate and hydrogen absorption were performed in UNS G41300 steel for different regions of Figure 1 of ISO 15156/MR 0175 (Environmental severity with respect to SSC of carbon and low alloy steels) at 24ºC in high chloride acid solutions (pH<6) with H2S partial pressures between 0.03 to 1 bar. Weigh loss experiments were performed using coupons in stagnant conditions and hydrogen insertion was evaluated using Devanathan Stachursky double cell. SEM/EDS and X-Ray Diffraction were used to characterize the corrosion products. The initial contact of the steel with an acid brine solution generated an amorphous layer initially rich in oxygen that converted to sulfide by replacement of O2- by S2- once the hydrogen sulfide was introduced in the testing vessel; sometimes leading to a crystalline iron sulfide, M(S,O). The corrosion product was semi protective since hydrogen insertion and therefore steel oxidation were not eliminated after the film formation. Cubic FeS and mackinawite were detected when partial pressures of hydrogen sulfide were higher than 0.1 bar. Cubic iron sulfide was unstable and converted to mackinawite by solid state reaction once the product was removed from the testing vessel. Transformation kinetics cubic FeS was dependent upon the presence of acetate, pH and O2. Based on the obtained results, a mechanism of sulfide formation was proposed. Corrosion rate and hydrogen insertion were found to be dependent on the product of the dissolved hydrogen sulfide and proton concentrations; suggesting that adsorption of reactants (particularly OH- and S2-) on the surface and stability of the amorphous layer plays a key role in both phenomena.

Loss of tidal wetlands is a world-wide phenomenon. Many factors may contribute to such loss, but among them are geochemical stressors such as exposure of the marsh plants to elevated levels on hydrogen sulfide in the pore water of the marsh peat. Here we report the results of a study of the geochemistry of iron and sulfide at different seasons in unrestored (JoCo) and partially restored (Big Egg) salt marshes in Jamaica Bay, a highly urbanized estuary in New York City where the loss of salt marsh area has accelerated in recent years. The spatial and temporal 2-dimensional distribution patterns of dissolved Fe2+ and H2S in salt marshes were in situ mapped with high resolution planar sensors for the first time. The vertical profiles of Fe2+ and hydrogen sulfide, as well as related solutes and redox potentials in marsh were also evaluated by sampling the pore water at discrete depths. Sediment cores were collected at various seasons and the solid phase Fe, S, N, C, and chromium reducible sulfide in marsh peat at discrete depths were further investigated in order to study Fe and S cycles, and their relationship to the organic matter cycling at different seasons. Our results revealed that the redox sensitive elements Fe2+ and S2– showed significantly heterogeneous and complex three dimensional distribution patterns in salt marsh, over mm to cm scales, directly associated with the plant roots due to the oxygen leakage from roots and redox diagenetic reactions. We hypothesize that the oxic layers with low/undetected H2S and Fe2+ formed around roots help marsh plants to survive in the high levels of H2S by reducing sulfide absorption. The overall concentrations of Fe2+ and H2S and distribution patterns also seasonally varied with temperature change. H2S level in JoCo sampling site could change from <0.02 mM in spring to >5 mM in fall season, reflecting significantly seasonal variation in the rates of bacterial oxidation of organic matter at this marsh site. Solid phase Fe and S showed that very high fractions of the diagenetically reactive iron at JoCo and Big Egg were associated with pyrite that can persist for long periods in anoxic sediments. This implies that there is insufficient diagenetically reactive iron to buffer the pore water hydrogen sulfide through formation of iron sulfides at JoCo and Big Egg.

Sulfidization of lepidocrocite and its effect on uranium phase distribution and reduction

Metal sulfide scales are found in several fields in onshore and offshore oil and gas wells around the world. Although there has been some success in the development of sulfide scale inhibitors, significantly high concentration of inhibitor is often required specially to mitigate zinc sulfide. Microbial biosurfactants have an inherent affinity towards different mineral surfaces including sulfides. The unique surface and interfacial properties of these naturally derived products make them potential candidates for development of new products for metal sulfide scale management and control. In this work the properties of sophorolipids and rhamnolipids as dispersion and modification agents for iron and zinc sulfide precipitates were investigated. Surface and interfacial tension behaviors of microbial biosurfactants were measured using a drop shape tensiometer. Accelerated dispersion stability testing were used to determine the efficiency of biosurfactants for dispersing field collected and lab-made iron and zinc sulfides. Fourier transform – infrared (FTIR) and ultraviolet – visible (UV-vis) spectroscopy was used to determine the mode of interaction of the biosurfactant active sites with metal sulfide surfaces.