Effect of Sulfate Load on Sulfur Removal in Model Constructed Wetlands
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Four model constructed wetlands (CWs) were designed to investigate the effects of sulfate load on sulfate and sulfide removal. The results showed that as the sulfate load increased from 1.42 to 7.01 g S m–3 d–1, the sulfate removal rate increased from 1.42 to 3.16 g S m–3 d–1, and the sulfide discharge rate increased from 0.08 to 1.46 g S m–3 d–1. The total sulfur removal rate ranged between 1.29 and 1.74 g S m–3 d–1. The sulfide in the effluent only accounted for 5.55%–46.9% of the removed sulfate. This indicated that CWs can effectively reduce sulfide discharge while removing sulfate. The conversion of dissolved sulfide into deposited sulfur by CW matrix was a main way for sulfide removal. Elemental sulfur, acid volatile sulfide (AVS), and pyrite-sulfur were the main forms of sulfur deposition in this study. The accumulations of these three sulfur compounds were 16.6–36.2, 22.3–36.0, and 49.7–63.6 mg S kg–1 gravel, respectively. Sulfur balance analysis showed that 42.9%–71.1% of the removed sulfate was deposited in the matrix, and only 0.84%–2.34% was absorbed by the plant.Oxidizing agent
Tetrathionate
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Bacteria that disproportionate elemental sulfur fractionate sulfur isotopes such that sulfate is enriched in sulfur-34 by 12.6 to 15.3 per mil and sulfide is depleted in sulfur-34 by 7.3 to 8.6 per mil. Through a repeated cycle of sulfide oxidation to S0 and subsequent disproportionation, these bacteria can deplete sedimentary sulfides in sulfur-34. A prediction, borne out by observation, is that more extensive sulfide oxidation will lead to sulfides that are more depleted in sulfur-34. Thus, the oxidative part of the sulfur cycle creates circumstances by which sulfides become more depleted in sulfur-34 than would be possible with sulfate-reducing bacteria alone.
Sulfur Cycle
Sulfate-Reducing Bacteria
Isotopes of sulfur
Sulfur Metabolism
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Sulfur Metabolism
Isotopes of sulfur
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Four model constructed wetlands (CWs) were designed to investigate the effects of sulfate load on sulfate and sulfide removal. The results showed that as the sulfate load increased from 1.42 to 7.01 g S m–3 d–1, the sulfate removal rate increased from 1.42 to 3.16 g S m–3 d–1, and the sulfide discharge rate increased from 0.08 to 1.46 g S m–3 d–1. The total sulfur removal rate ranged between 1.29 and 1.74 g S m–3 d–1. The sulfide in the effluent only accounted for 5.55%–46.9% of the removed sulfate. This indicated that CWs can effectively reduce sulfide discharge while removing sulfate. The conversion of dissolved sulfide into deposited sulfur by CW matrix was a main way for sulfide removal. Elemental sulfur, acid volatile sulfide (AVS), and pyrite-sulfur were the main forms of sulfur deposition in this study. The accumulations of these three sulfur compounds were 16.6–36.2, 22.3–36.0, and 49.7–63.6 mg S kg–1 gravel, respectively. Sulfur balance analysis showed that 42.9%–71.1% of the removed sulfate was deposited in the matrix, and only 0.84%–2.34% was absorbed by the plant.
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Onion (Allium cepa L.) was exposed to low levels of H2S in order to investigate to what extent H2S could be used as a sulfur source for growth under sulfate-deprived conditions. Sulfate deprivation for a two-week period resulted in a decreased biomass production of the shoot, a subsequently decreased shoot to root ratio and an increased dry matter content in shoot and roots. Furthermore, it resulted in decreased contents of total sulfur, sulfate and organic sulfur and in a decreased sulfate to total sulfur ratio. Symptoms of sulfur deficiency disappeared upon simultaneous exposure to relatively low levels of H2S (0.05, 0.1 and 0.15 mu l l(-1)), which showed that H2S could be used as a sulfur source for growth. H2S exposure even resulted in a slightly increased biomass production in sulfate-sufficient plants. The observed accumulation of sulfate and organic sulfur upon H2S exposure in both sulfate-sufficient and sulfate-deprived plants is discussed.
Sulfur Metabolism
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Claus process
Carbonyl sulfide
Acid gas
Carbon disulfide
Sour gas
Dimethyl sulfide
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Targeted at pyrite concentrate containing arsenic,improvement on mineral processing technology can gain high-quality sulfur concentrate.A small-scaled closed-circuit test in the lab obtains pyrite concentrate with 49.21 % sulfur,0.104 % arsenic,1.03 g/t gold,sulfur recovery of 92.42 % and gold recovery of 93.13 %.The problem in general utilization of iron-sulfur double resources in pyrite can be fundamentally solved.
Mineral processing
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The Beavon sulfur removal process for the cleanup of Claus plant tail gas is a two-step process in which the sulfur contaminants are first catalytically hydrolyzed and/or hydrogenated to hydrogen sulfide and the hydrogen sulfide is then converted to elemental sulfur and recovered in a Stretford process unit. Commercial plants reduce the concentration of sulfur compounds as hydrogen sulfide in the tail gas from 1-3 vol % to less than 100 ppm. The treated gas contains less than 1 ppm hydrogen sulfide. The chemistry, design criteria, operating experience, and economics of the process are discussed.
Claus process
Acid gas
Sour gas
Carbonyl sulfide
Hydrogen sulphide
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Sulfur isotope compositions (δ34S) were analysed on elemental sulfur and cellular protein in sulfur-oxidizing bacterial mats and on hydrogen sulfide and sulfate in the associated geothermal waters which were collected from nine locations in central and northeastern Japan. The δ34S values of elemental sulfur and cellular protein in the mats were comparable to those of hydrogen sulfide, but far from the associated sulfate in the waters, indicating the positive use of dissolved hydrogen sulfide. There could be observed slightly negative (rod-shaped bacteria) and positive (sickle-formed bacteria) sulfur isotope fractionations (up to 2‰) during the bacterial use of hydrogen sulfide.
Sulfate-Reducing Bacteria
δ34S
Oxidizing agent
Isotopes of sulfur
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Growing cultures of the green obligate photolithotroph, Chlorobaculum parvum DSM 263T (formerly Chlorobium vibrioforme forma specialis thiosulfatophilum NCIB 8327), oxidized sulfide quantitatively to elemental sulfur, with no sulfate formation. In the early stages of growth and sulfide oxidation, the sulfur product became significantly enriched with 34S, with a maximum delta34S above +5 per thousand, while the residual sulfide was progressively depleted in 34S to delta34S values greater than -4 per thousand. As oxidation proceeded, the delta34S of the sulfur declined to approach that of the initial sulfide when most of the substrate sulfide had been converted to sulfur in this closed culture system. No significant formation of sulfate occurred, and the substrate sulfide and elemental sulfur product accounted for all the sulfur provided throughout oxidation. The mean isotope fractionation factors (epsilon) for sulfide and sulfur were equivalent at epsilon values of -2.4 per thousand and +2.4 per thousand respectively. The significance of the experimentally-observed fractionation to the 34S/32S ratios seen in natural sulfur-containing minerals is considered.
Isotopes of sulfur
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