The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
Simo O Pehkonen - One of the best experts on this subject based on the ideXlab platform.
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surface chemistry and corrosion behaviour of 304 stainless steel in simulated seawater containing inorganic Sulphide and sulphate reducing bacteria
Corrosion Science, 2013Co-Authors: Shaojun Yuan, Bin Liang, Yu Zhao, Simo O PehkonenAbstract:Abstract Although many studies have been carried out regarding the role of Sulphide anions in promoting microbial corrosion of various metal substrates, very little is known about the differences between inorganic Sulphide and biogenically-derived Sulphide by sulphate-reducing bacteria (SRB) and what the reasons for differing corrosion behaviour between the two types of Sulphide may be towards common metals. In this study, various electrochemical and surface analytical techniques were employed to study the effect of the inorganic and biogenic Sulphide (active SRB present) on the surface chemistry and corrosion behaviour of 304 stainless steels in a simulated seawater-based modified Baar’s (SSMB) medium. Clear differences in the surface chemistry of the sulphurised passive film by inorganic and biogenic Sulphide (active SRB present) were quantified by X-ray photoelectron spectroscopy (XPS). The transformation of metal Sulphides in abiotic and biotic Sulphide solutions with the exposure time was correlated with different corrosion behaviour of 304 stainless steels.
Shaojun Yuan - One of the best experts on this subject based on the ideXlab platform.
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surface chemistry and corrosion behaviour of 304 stainless steel in simulated seawater containing inorganic Sulphide and sulphate reducing bacteria
Corrosion Science, 2013Co-Authors: Shaojun Yuan, Bin Liang, Yu Zhao, Simo O PehkonenAbstract:Abstract Although many studies have been carried out regarding the role of Sulphide anions in promoting microbial corrosion of various metal substrates, very little is known about the differences between inorganic Sulphide and biogenically-derived Sulphide by sulphate-reducing bacteria (SRB) and what the reasons for differing corrosion behaviour between the two types of Sulphide may be towards common metals. In this study, various electrochemical and surface analytical techniques were employed to study the effect of the inorganic and biogenic Sulphide (active SRB present) on the surface chemistry and corrosion behaviour of 304 stainless steels in a simulated seawater-based modified Baar’s (SSMB) medium. Clear differences in the surface chemistry of the sulphurised passive film by inorganic and biogenic Sulphide (active SRB present) were quantified by X-ray photoelectron spectroscopy (XPS). The transformation of metal Sulphides in abiotic and biotic Sulphide solutions with the exposure time was correlated with different corrosion behaviour of 304 stainless steels.
Jacques Cailteux - One of the best experts on this subject based on the ideXlab platform.
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Anhydrite pseudomorphs and the origin of stratiform Cu-Co ores in the Katangan Copperbelt
Mineralium Deposita, 2016Co-Authors: Philippe Muchez, P. Vanderhaeghen, H. El Desouky, Stijn Dewaele, Adrian J. Boyce, Jens Schneider, Jacques CailteuxAbstract:The stratiform Cu-Co ore deposits in the Katangan Copperbelt consist of dispersed Sulphides, Sulphides in nodules and lenses, which are often pseudomorphs after evaporites, and in veins. Two types of pseudomorphs can be distinguished in the nodules and lenses. In Type 1 examples, dolomite precipitated first and was subsequently replaced by Cu-Co Sulphides and authigenic quartz, whereas in Type 2 examples, authigenic quartz and Cu-Co Sulphides precipitated prior to dolomite and are coarse-grained. The sulphur isotopic composition of the copper-cobalt Sulphides in the Type 1 pseudomorphs is between -10.3 and 3.1 V-CDT, indicating that the Sulphide was derived from bacterial sulphate reduction (BSR). The generation of HCO3- during this process caused the precipitation and replacement of anhydrite by dolomite. A second product of BSR is the generation of H2S. We suggest that metals in the mineralising fluid reacted with the H2S, resulting in the precipitation of Cu-Co Sulphides. Initial Sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core. Precipitation of authigenic quartz was most likely induced by a pH decrease during Sulphide precipitation. Fluid inclusion data from quartz indicate the presence of a high-salinity (8-18 eq. wt% NaCl) mineralising fluid, possibly derived from evaporated seawater which migrated through the deep subsurface. 87Sr/86Sr ratios of dolomite in Type 1 nodules range between 0.71012 and 0.73576 significantly more radiogenic than the strontium isotopic composition of Neoproterozoic marine carbonates (87Sr/86Sr = 0.7056-0.7087). This suggests intense interaction with siliciclastic sedimentary rocks and/or the granitic basement. The low carbon isotopic composition of the dolomite in the pseudomorphs (-7.02 and -9.93 V-PDB) compared to the host rock dolomites (-4.90 and +1.31 V-PDB) resulted from the oxidation of organic matter during BSR.
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Anhydrite pseudomorphs and the origin of stratiform Cu-Co ores in the Katangan Copperbelt (Democratic Republic of Congo)
Mineralium Deposita, 2008Co-Authors: Philippe Muchez, P. Vanderhaeghen, H. El Desouky, Stijn Dewaele, Adrian J. Boyce, Jens Schneider, Jacques CailteuxAbstract:The stratiform Cu–Co ore mineralisation in the Katangan Copperbelt consists of dispersed Sulphides and Sulphides in nodules and lenses, which are often pseudomorphs after evaporites. Two types of pseudomorphs can be distinguished in the nodules and lenses. In type 1 examples, dolomite precipitated first and was subsequently replaced by Cu–Co Sulphides and authigenic quartz, whereas in type 2 examples, authigenic quartz and Cu–Co Sulphides precipitated prior to dolomite and are coarse-grained. The sulphur isotopic composition of the copper–cobalt Sulphides in the type 1 pseudomorphs is between −10.3 and 3.1‰ relative to the Vienna Canyon Diablo Troilite, indicating that the Sulphide component was derived from bacterial sulphate reduction (BSR). The generation of \({\text{HCO}}_3^ - \) during this process caused the precipitation and replacement of anhydrite by dolomite. A second product of BSR is the generation of H2S, resulting in the precipitation of Cu–Co Sulphides from the mineralising fluids. Initial Sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core. Precipitation of authigenic quartz was most likely induced by a pH decrease during Sulphide precipitation. Fluid inclusion data from quartz indicate the presence of a high-salinity (8–18 eq. wt.% NaCl) fluid, possibly derived from evaporated seawater which migrated through the deep subsurface. 87Sr/86Sr ratios of dolomite in type 1 nodules range between 0.71012 and 0.73576, significantly more radiogenic than the strontium isotopic composition of Neoproterozoic marine carbonates (87Sr/86Sr = 0.7056–0.7087). This suggests intense interaction with siliciclastic sedimentary rocks and/or the granitic basement. The low carbon isotopic composition of the dolomite in the pseudomorphs (−7.02 and −9.93‰ relative to the Vienna Pee Dee Belemnite, V-PDB) compared to the host rock dolomite (−4.90 and +1.31‰ V-PDB) resulted from the oxidation of organic matter during BSR.
Malcolm S Cresser - One of the best experts on this subject based on the ideXlab platform.
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automated determination of sulphite and sulphur dioxide by cool flame molecular emission spectrometry after reduction to hydrogen Sulphide with sodium tetrahydroborate iii
Talanta, 1992Co-Authors: T A Arowolo, Malcolm S CresserAbstract:An automated method for the determination of sulphite and sulphur dioxide by cool flame molecular emission spectrometry is described. The method is based on the reduction of both compounds to hydrogen Sulphide with sodium tetrahydroborate III. The sample which is mixed with NaBH(4) is acidified with 6M hydrochloric acid and carried by a continuous-flow stream into a gas-liquid separator where the evolved hydrogen Sulphide is swept by nitrogen into a cool, hydrogen-nitrogen-entrained air flame. The intensity of the blue diatomic S(2) emission generated is measured at 384 nm. The proposed method has a detection limit for sulphite of 0.029 mug/ml and relative standard deviations of 1.2 and 1.5% for 1 and 5 mug/ml respectively. The calibration graph is linear up to 24 mug/ml sulphite and samples can be analysed at a rate of about 40/hr. The method has been applied to the determination of SO(2) in air and sulphite in wines.
L. Kryger - One of the best experts on this subject based on the ideXlab platform.
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Effects of soil ageing on the accumulation of hydrogen Sulphide and metallic Sulphides in mangrove areas in Singapore
Environment International, 1995Co-Authors: L. KrygerAbstract:Abstract The effects of soil ageing on the accumulation of hydrogen Sulphide and metallic Sulphides were studied in reclaimed mangrove plots of increasing ages. The analysis was carried out using a low-cost electrochemical approach, utilizing a Sulphide volatilization/trapping procedure followed by Sulphide quantification with an ion-selective electrode technique. The results showed that the content of hydrogen Sulphide in the soil increased with age. Initially, the content of metallic Sulphides also increased with the age of the soil. However, once the supply of metallic soil components for Sulphide precipitation had been exhausted, the Sulphides generated in the soils existed as hydrogen Sulphide. The reasons for these patterns of Sulphide accumulation in the mangrove soil and their possible impact on the growth of different types of mangrove vegetation are briefly discussed.
