Sulfide Sulfur Research Articles

Effect of copper ions on transformation of organic sulfur in cationic exchange resins in Li2CO3–Na2CO3–K2CO3 molten-salt system

Cationic exchange resins (CERs) were applied for purification and clarifying process of radioactive wastewater in nuclear industry, which was a kind of sulfur-containing organic material. Molten-salt oxidation (MSO) method can be applied for the treatment of spent CERs and the absorption of acid gas (such as SO2). The experiments about the molten salt destruction of the original resin and Cu ions doped resin were conducted. The transformation of organic sulfur in Cu ions doped resin was investigated. Compared with the original resin, the content of tail gas (such as CH4, C2H4, H2S and SO2) released from the decomposition of Cu ions doped resin was relatively high at 323–657 °C. Sulfur elements in the form of sulfates and copper sulfides were fixed in spent salt through XRD analysis. The XPS result revealed that the portion of functional sulfonic acid groups (-SO3H) in Cu ions doped resin was converted into sulfonyl bridges (-SO2-) at 325 °C. With the enhancement of temperature, sulfonyl bridges (-SO2-) were further decomposed to sulfoxides sulfur (-SO-) and organic sulfide sulfur. The destruction of thiophenic sulfur to H2S and CH4 was prompted by copper ions in copper sulfide. Sulfoxide were oxidized to the sulfone sulfur in molten salt. Sulfones sulfur consumed by reduction of Cu ions at 720 °C was more than it produced by oxidation of sulfoxide through XPS analysis, and the relative proportion of sulfone sulfur was 16.51%.

S, Pb, and Fe isotope compositions of sulfides in middle and southern Okinawa Trough: Implying the complicated hydrothermal systems in back-arc spreading centers

Sulfur, lead, and iron isotopic systematics of sulfides from the Iheya North hydrothermal field in middle Okinawa Trough and the Yonaguni Knoll IV hydrothermal field in southern Okinawa Trough were investigated to understand the origin of ore-forming material and isotope fractionation during sulfide precipitation in back-arc spreading centers. The δ34S values (from 8.60‰ to 9.68‰) of sulfide minerals in Iheya North field suggest sulfur was derived from the leaching of basement rocks and the reduction of seawater sulfate. But an additional light sulfur source from the dissolution of biogenic sulfides in sediments is indispensable for the observed low δ34S values (between 4.78‰ and 4.97‰) of Yonaguni Knoll IV sulfides. Lead isotope compositions of all sulfides vary in a relatively wide range (206Pb/204Pb = 18.432 to 18.563, 207Pb/204Pb = 15.579 to 15.671, and 208Pb/204Pb = 38.539 to 38.979, respectively) which involves the mixing of mantle-derived and sediment-derived lead in varying proportions. Unusually high radiogenic lead isotope ratios of Yonaguni Knoll IV sulfides (207Pb/204Pb = 15.628 to 15.671, and 208Pb/204Pb = 38.854 to 38.979) imply the presence of old crustal fragments beneath southern OT. The hydrothermal fluids in OT are characterized by extremely low calculated δ56Fe values (−1.00‰ to −1.32‰) which is attributed to reducing sediments. The paired Fe-isotope compositions of pyrite and chalcopyrite revealed significantly different iron isotope compositions of hydrothermal fluids in study areas and extremely complicated ore-forming processes. Rapid precipitation of pyrite from FeS precursors accompanying iron isotopic disequilibrium moves from FeS-fluid equilibrium to pyrite-fluid equilibrium during pyrite recrystallization. The combination of sulfur, lead, and iron isotopic data suggests that hydrothermal systems in back-arc spreading centers related to plate subduction are generally affected by mantle, overlying sediments as well as potential old continental crust fragments, which results in various hydrothermal fluids and complicated mineralization processes.

Solubility and dissolution kinetics of sulfur and sulfides in electrolyte solvents for lithium-sulfur and sodium-sulfur batteries.

In this study, we monitor the dissolution of sulfur and sulfides in electrolyte solvents for lithium-sulfur (Li-S) and sodium-sulfur (Na-S) batteries. The first aim of this research is to assemble a comprehensive set of data on solubilities and dissolution kinetics that may be used in the simulation of battery cycling. The investigation also offers important insights to address key bottlenecks in the development and commercialization of metal-sulfur batteries, including the incomplete dissolution of sulfur in discharge and insoluble low-order sulfides in charge, the probability of shuttling of soluble polysulfides, and the pausing of the redox reactions in precipitated low order sulfides depending on their degree of solid state. The tested materials include sulfur, lithium sulfides Li2Sx, x = 1, 2, 4, 6, and 8, and sodium sulfides Na2Sx, x = 1, 2, 3, 4, 6, and 8, dissolved in two alternative electrolyte solvents: DOL:DME 1:1 v/v and TEGDME. The determined properties of the solute dissolution in the solvent include saturation concentration, mass transfer coefficient, and diffusion coefficient of the solvent in the solid solute. In general, the DOL:DME system offers high solubility in Li-S batteries and TEGDME offers the highest solubility in Na-S batteries. Low solubility sulfides are Li2S2 and Li2S for the Li-S batteries, and Na2S3, Na2S2, and Na2S for the Na-S batteries. However, it is noted that Na2S3 dissolves fast in TEGDME and also TEGDME diffuses fast into Na2S3, offering the possibility of a swollen Na2S3 structure in which Na+ ions might diffuse and continue the redox reactions in a semisolid state.

Degradation of methyl orange using persulfate activated by magnetic CuS/Fe3O4 catalyst: Catalytic performance and mechanisms

While magnetic Fe3O4 provides Fe2+ to activate persulfate (PS) to produce sulfate radicals (SO4·-), Fe2+ tends to be oxidized to Fe3+, declining the activation efficiency. The low-valent sulfur in transition metal sulfide could convert Fe3+ to Fe2+ due to its strong reducibility, and CuS was used as the activator of PS. However, its separation and recovery posed great challenges to practical application. Magnetic CuS/Fe3O4 was prepared with a purpose to simultaneously convert Fe3+ to Fe2+ and rapidly separate CuS as a catalyst for the degradation of methyl orange (MO) by activating PS. The results showed that CuS/Fe3O4 exhibited higher activity than sole CuS or Fe3O4 as 94 % of MO was removed within 30 min. SO4·-, hydroxyl radical (·OH), superoxide radical (·O2–) and singlet oxygen (1O2) were detected in the CuS/Fe3O4/PS system and ·OH was the dominant active species. S2- and Sn2- provided electrons for the cycle of Fe3+/Fe2+ and Cu2+/Cu+, resulting in excellent catalytic activity of CuS/Fe3O4. The NC bond cleavage, the breakage of NN bond and the loss of SO2 bond were identified as three possible degradation pathways of MO. This work provided an effective strategy to enhance the catalytic activity and recovery of the catalyst, and improved the understanding of MO degradation mechanisms.

Molecular characterization of non-polar sulfur compounds in the full boiling range crude oil fractions

Organic sulfur compounds (OSCs) are usually the most abundant heteroatomic compounds in crude oils and have very complex molecular composition. Thousands of sulfur-containing compounds have been identified from various petroleum fractions by different techniques. However, complete characterization of sulfur compounds in specific crude oils is rarely reported. In this study, molecular characterization of sulfur compounds in a whole crude oil was carried out with gas chromatographic and mass spectrometric techniques. The crude oil was separated into naphtha (<180 °C), middle distillate (180–350 °C), and the residual (>350 °C) by distillation. The naphtha was directly analyzed by gas chromatography coupled with a sulfur chemiluminescence detector. A methylation/demethylation method was carried out to separate aromatic sulfur compounds (ASCs) and sulfidic sulfur compounds (SSCs) from the middle distillate and the residue. The separated ASCs and SSCs were characterized by GC and mass spectrometry, as well as Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A global distribution of OSCs in the crude oil was obtained by the combination of the analysis results. The type and content of OSCs are significantly different among the distillation fractions. Hydrogen sulfide and mercaptans, accounting for 0.1 % and 1.2 % of the total sulfur content, respectively, mainly distribute in naphtha. SSCs, which are rich in thiadiamondoids, account for 15.5 % of the total sulfur content. ASCs are the most abundant identified species and account for 35.8 % of total sulfur content. Other OSCs such as complex polyheteroatomic compounds occupied 41.0 % of the total sulfur content.

СЕРЕБРЯНАЯ МИНЕРАЛИЗАЦИЯ В ГЛУБИННЫХ МАГМАТОГЕННЫХ СИСТЕМАХ ДРЕВНИХ ОСТРОВНЫХ ДУГ: ИЛЬДЕУССКИЙ УЛЬТРАОСНОВНОЙ МАССИВ, СТАНОВОЙ МОБИЛЬНЫЙ ПОЯС (ДАЛЬНИЙ ВОСТОК РОССИИ)

The Triassic (232–233 Ma) Ildeus mafic-ultrabasic massif is a fragment of a large mineralized magmatogenic system formed within the Stanovoy mobile belt at the Mesozoic stage of its evolution. Ultrabasic rocks are represented by cumulative plagioclase- and amphibole-bearing dunites, peridotites, websterites, and pyroxenites; basic rocks are gabbro-anorthosites, norites, and two-pyroxene gabbro. Most intrusive rocks of the Ildeus magmatogenic system experienced ultramafic (serpentine, chlorite, talc, carbonates) and acidic (quartz, biotite, potassium feldspar, secondary micas) metasomatism. Geochemical characteristics (calc-alkaline differentiation trend, negative anomalies of highly charged incoherent elements) indicate the subduction nature of the primary magma in the Ildeus system. The ultrabasic rocks are intruded by intermediate-acid intrusions with geochemical characteristics of adakite. Magmatic-stage silver mineralization is represented by microinclusions of cuprous silver, alloys of silver, copper, gold and zinc, acanthite and silver halides in association with pentlandite, chalcopyrite, bornite, and pyrrhotite. These rocks are characterized by microinclusions of native platinum, gold, tungsten, bismuth, lead, PGE alloys, W-Co-Ti, Sb-Pb, Cu-Zn-Sn, minerals of Ag-Cu-Sb-Se-S and Zn-Ni systems -Co-Fe-S, barite, chlorapatite and Bi-Sn-Pb chlorides. At the metasomatic stage, native silver, Au-Ag alloys, silver and copper chlorides, acanthite, silver and lead tellurides coexist with digenite, heathlewoodite, pyrite, sphalerite, galena, native nickel and gold, Cu-Zn alloys, sulfides of the Pb-As- Cu-Fe-S and bismuth chloride. At the magmatic stage, silver minerals crystallized under reducing conditions in the presence of high-temperature aqueous fluids enriched in sulfide sulfur, halogens, and volatile siderophile (W, Pt) and chalcophile (Ag, Bi, Sn, Sb, Pb) metals that entered the primary melt from serpentinites, metamorphosed gabbroids, and metal-bearing pelagic sediments of the subducting oceanic plate. Metasomatic parageneses of silver minerals were formed under oxidized near-surface conditions with the participation of low-temperature water-salt solutions with elevated concentrations of sulfate sulfur, arsenic, and tellurium. A two-stage model is proposed for the formation of silver mineralization in island arc magmatic systems, in which the high-temperature magmatic stage of formation in deep crustal parts is replaced by low-temperature hydrothermal ore formation processes in near-surface conditions.

Effect of Sulfide Sulfur on the Crystallization of Low-Alkali Magmas: Prolegomena

The effect of sulfide sulfur on the crystallization of ultramafic–mafic–intermediate magmatic systems is considered in order to assess its scale and direction during the crystallization of rock-forming phases. The study carried out a theoretical analysis of the effect of sulfur on the activity of the components of the silicate melt according to the Korzhinskii’s principle of acid–base interaction. To test the theoretical constructions, published experimental data analyzed to select data allowing a direct comparison of sulfur-saturated and sulfur-free runs. Despite the very limited number of such experiments, they all fit well with theoretically predicted trends. It has been established that the addition of sulfur to the system moderately reduces the liquidus temperature of rock-forming minerals within 20–30°C, and significantly affects their composition. In particular, chrome spinel is enriched in chromium by 10–12 mol % and complementary depleted in aluminum. The composition of plagioclase is enriched in the anorthite component by 3 mol % in dacites and 8 mol % in andesites; this effect was not established in basalts, but its strengthening can be expected. Olivine and orthopyroxene demonstrate an insignificant increase in magnesian content, but the field of their coexistence is significantly reduced in favor of orthopyroxene, which should inevitably lead to a change in their cotectic and peritectic proportions. Natural observations that can be interpreted as the result of the sulfur effect are taken from publications. The results obtained lead to the conclusion that sulfur significantly affects the crystallization of silicate magmas. It follows that the petrological dependences calibrated for sulfur-free experiments should be applied with caution to the interpretation of sulfur-bearing systems.

Salinization of coastal saline-alkali soil might enhance H2S release by affecting H2S-related bacterial communities

Bacterial metabolism can result in the production and release of hydrogen sulfide (H2S), a reductive gas, in soils. Hydrogen sulfide-releasing bacteria (HSRB) assimilate organic sulfur or dissimilate sulfate to generate and release H2S, whereas H2S-oxidizing bacteria (HSOB) oxidize H2S generated by themselves or other bacteria to soluble sulfate resulting in sulfur retention in soil. However, the effects environmental factors such as electrical conductivity on both these bacterial groups and H2S release remain unclear; some key processes such as H2S oxidation also remain underexplored. In this study, we found that high electrical conductivity in coastal saline-alkali soil affects these bacterial communities, especially HSRB, potentially enhancing H2S release. The “sink” of H2S gas, represented by sulfidic sulfur (concentration, 0.2–3.4 nmol/g) in coastal saline-alkali and inland soils, was determined using the methylene blue method, and found to be positively correlated with soil electrical conductivity, suggesting that more H2S gas potentially volatilized from salinized soil. We then revealed that the proportion of HSRB clones was correlated positively and significantly with the electrical conductivity and sulfidic sulfur of soil, but not with the pH or sulfur source. Further, 16S rRNA gene sequence comparison indicated significantly reduced richness and diversity of bacterial communities and considerably altered the composition of dominant bacterial populations in coastal saline-alkali soil. The phyla Proteobacteria, Bacteroidetes, and Gemmatimonadetes accounted for 38 %, 30.1 %, and 11.1 % and for 28 %, 12.9 %, and 2.5 % of the bacterial populations in coastal saline-alkali and inland soil, respectively. PICRUSt analysis showed that the richness of genes encoding the key H2S oxidation enzymes, sulfide:quinone reductase and sulfate hydrolase, was decreased significantly and negatively correlated with the detected sulfidic sulfur. These enzymes are usually expressed by HSOB in coastal saline-alkali soil, implying a low sulfide oxidation capacity. These results indicate that the number of HSRB is increased whereas the ability of H2S oxidation is decreased in coastal saline-alkali soil, which might lead to enhanced H2S release. Overall, this study provides new insights for understanding the sulfur biological cycle in saline-alkali soils.

Slyudyankaite, Na28Ca4(Si24Al24O96)(SO4)6(S6)1/3(CO2)·2H2O, a new sodalite-group mineral from the Malo-Bystrinskoe lazurite deposit, Baikal Lake area, Russia

Abstract The new sodalite-group mineral species slyudyankaite, ideally Na28Ca4(Si24Al24O96) (SO4)6(S6)1/3(CO2)·2H2O, was discovered in altered lazurite-bearing metasomatic rock at the Malo-Bystrinskoe gem lazurite deposit, Baikal Lake area, eastern Siberia, Russia. The associated minerals are diopside, calcite, fluorapatite, phlogopite, lazurite, and pyrite. Slyudyankaite forms green to pale blue isolated anhedral equant grains up to 0.5 cm across and their aggregates. The streak is white and the luster is vitreous. Slyudyankaite is brittle, with a Mohs hardness of 5½. Cleavage and parting are not observed. Density measured by flotation in heavy liquids is equal to 2.46(2) g·cm–3. Density, calculated using the empirical formula and unit-cell volume refined from single-crystal XRD data, is 2.454 g·cm–3. Slyudyankaite was characterized using the IR, Raman, ESR, near infrared (NIR), visible (Vis), and ultraviolet (UV) absorption, XPS and photoluminescence spectroscopy methods. The chemical composition is (wt%, electron microprobe, H2O and CO2 determined by selective sorption of ignition products, CO2 confirmed by quantitative IR spectroscopic method, sulfate sulfur determined by wet chemical analysis): Na2O 19.28, K2O 0.12, CaO 5.13, Al2O3 27.01, SiO2 33.25, SO3 10.94, S 1.75, Cl 0.10, CO2 1.42, H2O 0.90, –O≡(Cl,HS) –0.03, total 99.87. The empirical formula is Na27.57Ca4.05 K0.11(Si24.52Al23.48O96)(SO4)6.06S2.420Cl0.12(CO2)1.43·2.21H2O where S2.420 is the total sulfide sulfur, mainly occurring as neutral S6 and subordinate S4 molecules, according to the structural data. XPS spectroscopy confirms the presence of sulfide sulfur in neutral form. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.0428. Slyudyankaite is triclinic, space group P1, a = 9.0523(4) Å, b = 12.8806(6) Å, c = 25.681(1) Å, α = 89.988(2)°, β = 90.052(1)°, γ = 90.221(1)°, V = 2994.4(2) Å3, Z = 1. Slyudyankaite contains two kinds of sodalite cages occurring in the structure in a ratio of 3:1. Cages of the first kind are completely occupied by SO42− anions and extra-framework cations, whereas cages of the second type contain only neutral molecules (S6, CO2, H2O, and minor S4). The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 6.45 (11) (004, 112, 020), 3.716 (100) (204, 220, 116, 132), 2.878 (12) (136, 028, 044), 2.625 (23) (208, 240), 2.431 (6) (209), 2.275 (6) (048), 2.143 (12) (0.0.12, 336), 1.784 (7) (444, 1.1.14, 356, 172).

DFT study about capturing of toxic sulfur gases over cyclic tetrapyrrole

The development of sensors that can detect hazardous analytes selectively and accurately, particularly sulfur based irritants, is quite essential. The infinite-conjugation in cyclic conducting polymers make them highly sensitive to toxic analytes. We implemented B3LYP-D3/6–311 + G (d, p) level to explore the sensing mechanism of cyclic tetrapyrrole (CTPy) for reliable detection of carbonyl sulfide, carbon disulfide, hydrogen sulfide sulfur monoxide, sulfur dioxide and sulfur trioxide using the DFT practice. The interaction energies, Eint ranges from –25.6 to –89.2 kJ mol−1 for sulfur gases over CTPy. Charge transfer interactions in complexes are predicted using natural bond orbital (NBO) and charge decomposition (CDA) analysis. The reduced density gradient (RDG) method supports hydrogen bonding and dispersion interactions in the complexes. The decrease in HOMO-LUMO energy gaps, as well as the red shifting of λmax in UV–Visible spectra, demonstrate sensitivity of CTPy towards sulfur gases. The improved conductivity of complexes is owing to production of numerous energy levels inoccupied and virtual orbitals closer to the Fermi level in DOS spectra. Furthermore, PDOS spectra reveal that CTPy is chiefly contribute to energy of HOMO. The recent findings show CTPy has a significant sensitivity to sulfurirritants. We hope that the above findings and their implications will give valuable suggestions for an experimentalist in designing extremely sensitive hazardous analyte sensors employing CTPy.

Genesis of the Beixiang Sb-Pb-Zn-Sn Deposit and Polymetallic Enrichment of the Danchi Sn-Polymetallic Ore Belt in Guangxi, SW China

Antimony deposits contain little Sn, whereas Sb and Pb are not the principally contained metal of granite-related Sn deposits. The Danchi Sn-metallogenic ore belt (DSOB) in southwestern China is characterized by Sn-Sb-Zn-Pb co-enrichment, yet the triggers are poorly constrained. The Beixiang deposit in the southern DSOB consists of stage I Sn-Zn and stage II Sb-Pb-Zn mineralization. Here, we analyzed the cassiterite U-Pb age, fluid inclusion H-O and sulfide Pb-S isotopes, and calcite trace elements of the Beixiang ores. By comparing with the Dachang and Mangchang Sn-polymetallic ore-fields within the DSOB, we constrained the timing of regional mineralization and revealed the processes causing the Sb-Pb co-enrichment. The cassiterite U-Pb dating yielded 90.6 ± 4.5 Ma (MSWD = 2.6), similar to the ages of the Dachang and Mangchang ore fields, indicating the Late Cretaceous mineralization event throughout the DSOB. The fluid inclusions from stage II ore have δ18OH2O (−2.8 to −7.8‰) and δDV-SMOW (−90.5 to −59.3‰), and the synchronous calcite features have low REE contents, upward-convex REE patterns, and weak Eu anomalies. These suggest that the ore fluids were derived from meteoric water and oil field brine, which dissolved S and Pb from local strata as recorded by sulfide sulfur (δ34SV-CDT = −6.2 to −4.0‰) and Pb isotopes. However, calcite from the stage I ore have higher REE contents and (La/Yb)N, with strong positive Eu anomalies, indicating that the Sn-rich ore fluids were released by greisenization of granite. Overall, we suggest that the combination of granitic magma- and oil field brine-derived fluids, rich in Sn-Zn and Sb-Pb-Zn, respectively, caused the co-enrichment of Sn-Sb-Pb-Zn in Beixiang and throughout the DSOB.

Carbonyl Sulfide Sulfur Isotope Fractionation During Uptake by C3 and C4 Plants

AbstractCarbonyl sulfide (COS) is a major long‐lived sulfur‐containing gas in the atmosphere. Similar to CO2, COS main sink is the uptake by terrestrial plants. Therefore, COS is used as a proxy for CO2 uptake by terrestrial plants (gross primary production [GPP]). Currently, COS budget estimates have large uncertainties. Sulfur isotopes measurements are used in an isotopic mass‐balance to constrain the COS budget. Here we conducted plant‐chamber experiments for determining the isotopic fractionation during COS uptake by C3 and C4 plants, and that associated with enzymatic fractionation inside plant leaves. We also conducted COS diffusion in nitrogen experiment to determine the fractionation associated with COS diffusion through plant stomata. We then measured the δ34S values of COS from these experiments by a gas chromatograph/multicollector inductively coupled plasma mass spectrometer. Applying these measured δ34S values, we calculated fractionations (εplant) of −1.6 ± 0.1‰ and −5.4 ± 0.5‰ during COS uptake for C3 plants and C4 plants respectively. A fractionation of −5.2 ± 0.5‰ for COS diffusion through plant stomata was calculated as well. We estimate the total diffusive component of plant uptake fractionation (including boundary layer, stomata, and gas‐liquid interface diffusions) as −1.6 ± 0.1‰. Using plant chamber measurements under high CO2 and COS concentrations we calculated the enzymatic component of the plant uptake fractionation as −15 ± 2‰. Based on the diffusive and enzymatic components of plant uptake fractionation, we calculate COS concentrations inside plant leaves. Using the C3 and C4 fractionation results, a value of −2.3 ± 0.5‰ is estimated as the global plant uptake fractionation, which can be incorporated into improved COS‐based‐GPP estimates in the future.

Local charge-displacement analysis: Targeting local charge-flows in complex intermolecular interactions

Charge-displacement (CD) analysis has recently proven to be a simple and powerful scheme for quantitatively analyzing the profile the charge redistribution occurring upon intermolecular interactions along a given interaction axis. However, when two molecular fragments bind through complex interactions involving multiple concurrent charge flows, ordinary CD analysis is capable of providing only an averaged picture of the related charge-flow profiles and no detailed information on each of them. In this article, we combine CD analysis with a Hirshfeld partitioning of the molecular charge redistribution for a local analysis on focused portions of the molecule, allowing for a detailed characterization of one charge flow at a time. The resulting scheme—the local charge-displacement (LCD) analysis—is tested on the intriguing case of the dimethyl sulfide–sulfur dioxide complex, characterized by concurrent charge flows relating to a sulfur–sulfur homochalcogen interaction and a pair of hydrogen bonds. The LCD scheme is then applied to the analysis of multiple hydrogen bonding in the acetic acid dimer, of base-pairing interactions in DNA, and of ambifunctional hydrogen bonding in the ammonia–pyridine complex.

Microbial Biogas Production from Pork Gelatine

This research describes the results of the anaerobic digestion of gelatine as a potential hydrogen source with heat-shocked inoculum. The concentrations of applied gelatine were of VSS (volatile suspended solids) ranging from 10 g VSS/L to 30 g VSS/L. The initial process pH was 5.5, and, depending on the concentration, reached pH values from 7.5 to 7.8 after 55 days. Although the inoculum was heat-shocked in 30 g VSS/L of collagen, the process that occurred was hydrogenotrophic anaerobic digestion. In gelatine concentrations below 30 g VSS/L, hydrogen production was dominant only during the first 5 days of the experiments. Then, there was a change from dark fermentation to hydrogenotrophic methane production. The optimal hydrogen and methane yields resulted from the concentrations of 10 g VSS/L (7.65 mL ± 0.01 mL H2/g VSS and 3.49 ± 0.01 L CH4/g VSS). Additionally, 10 g VSS/L had the lowest accumulated emission of hydrogen sulphide (10.3 ± 0.01 mL of H2S), while 30 g VSS/L (0.440 ± 0.01mL H2S/g VSS) produced the lowest yield. After a lag time, the hydrogen production and hydrogen sulphide grew with a specific ratio, depending on the concentration. The hydrogen sulphide emission and sulphur added analysis proved that hydrogen sulphide originating from biogas created by bacteria remains longer than that from a substrate.

Lithological and geochemical evidence of catagenetic transformations of black shales on the example of the Bazhenov formation in Western Siberia

The regularities of changes in the lithological and geochemical composition of Bazhenov Formation (BF) rocks characterized by different degrees of organic matter transformation are determined. From МК1 2–МК2 (140–170 C–170–195 C), the following tendency is revealed: a) increasing of the number of calcareous-dolomitic interlayers and content of the dolomite in them; b) reducing of the content of S in the whole section; c) reducing of the OM and sulfide sulfur contents in “pyrite-kerogen” layers of roof of BF; d) reducing of the ratios of C/S; d) increasing of the “pyrite” layer thickness in the transition zone of BF and the overlying sediments and the content of pyrite in it. It is concluded that in the period between the stages corresponding to the grades МК1–МК2, there is a transformation of OM, migration of its transformation products, dolomitization of rocks, and pyritization of low-carbon rocks of the overlying BF Podachimov strata.

Safe, accurate, and precise sulfur isotope analyses of arsenides, sulfarsenides, and arsenic and mercury sulfides by conversion to barium sulfate before EA/IRMS

The stable isotope ratios of sulfur (δ34S relative to Vienna Cañon Diablo Troilite) in sulfates and sulfides determined by elemental analysis and isotope ratio mass spectrometry (EA/IRMS) have been proven to be a remarkable tool for studies of the (bio)geochemical sulfur cycles in modern and ancient environments. However, the use of EA/IRMS to measure δ34S in arsenides and sulfarsenides may not be straightforward. This difficulty can lead to potential health and environmental hazards in the workplace and analytical problems such as instrument contamination, memory effects, and a non-matrix-matched standardization of δ34S measurements with suitable reference materials. To overcome these practical and analytical challenges, we developed a procedure for sulfur isotope analysis of arsenides, which can also be safely used for EA/IRMS analysis of arsenic sulfides (i.e., realgar, orpiment, arsenopyrite, and arsenian pyrite), and mercury sulfides (cinnabar). The sulfur dioxide produced from off-line EA combustion was trapped in an aqueous barium chloride solution in a leak-free system and precipitated as barium sulfate after quantitative oxidation of hydrogen sulfite by hydrogen peroxide. The derived barium sulfate was analyzed by conventional EA/IRMS, which bracketed the δ34S values of the samples with three international sulfate reference materials. The protocol (BaSO4-EA/IRMS) was validated by analyses of reference materials and laboratory standards of sulfate and sulfides and achieved accuracy and precision comparable with those of direct EA/IRMS. The δ34S values determined by BaSO4-EA/IRMS in sulfides (arsenopyrite, arsenic, and mercury sulfides) samples from different origins were comparable to those obtained by EA/IRMS, and no sulfur isotope fractionations were introduced during sample preparation. We report the first sulfur isotope data of arsenides obtained by BaSO4-EA/IRMS.Graphical abstract

Carbon Sources as a Factor Determining the Activity of Microbial Oxidation of Sulfide Concentrate at Elevated Temperature

The goal of the present work was to evaluate the possibility of improving the efficiency of the stirred tank reactor biooxidation of sulfide gold-bearing concentrate by means of addition of carbon sources required for the constructive metabolism of microorganisms. Biooxidation experiments were performed on gold-bearing pyrite-arsenopyrite concentrate in continuous mode at 45 °C to determine the influence of additional carbon sources (carbon dioxide and molasses) on sulfide mineral oxidation. The use of CO2 allowed increasing the efficiency of the biooxidation and the extents of sulfide sulfur (Ss) oxidation and gold recovery were 79% and 84%, respectively. Biooxidation in a control experiment (without additional carbon sources) and when using molasses allowed achieving 39% and 66% oxidation of Ss as well as 73% and 81% of gold recovery. Analysis of the microbial populations formed in biooxidation reactors using NGS methods demonstrated that CO2 application led to an increase in the relative abundance of the genus Sulfobacillus. Thus, it was determined that application of additional carbon source makes it possible to manage the biooxidation process, affecting both sulfide mineral oxidation and microbial population composition.

МОДЕЛИ И МЕТОДЫ ГЕОХИМИЧЕСКОЙ ОЦЕНКИ РИСКА ВЗАИМОДЕЙСТВИЯ ПОРОДНЫХ ОТВАЛОВ С ФАКТОРАМИ ВНЕШНЕЙ СРЕДЫ

Models and methods of geochemical testing and evaluation of the influence of rock dumps on environmental factors are considered. The object of testing are samples of ores and rocks in the tailings dump formed during the extraction of porphyry-copper ores by an open method. The purpose of testing is to assess the risk of rock dumps" interaction with environmental factors, to determine the content of harmful substances in dust, as well as the formation of drainage of acidic rocks and leached metals. The task of testing is to analyze the average content of sulfur and sulfur sulfide in dump rocks and ores, to analyze the acid-neutralizing potential in these rocks and the potential for acid neutralization, as well as to assess the risk of rock dumps" interaction with environmental factors. Based on the acid base accounting indicators, characterizing the amount of acid-producing (sulfides) and acid-neutralizing (carbonates) minerals, as well as their ratios, an accelerated predictive assessment of the risk of acid drainage and mine water formation has been performed. With the help of geochemical testing of rock samples and dumps, the contents of sulfur, sulfur sulfide, acid-neutralizing potential and acid neutralization potential are determined. With the help of geochemical testing of rocks and ores, the impact of rock dumps on the external environment has been assessed, the content of harmful substances in dust and the influence of porphyry-copper ores on the formation of acidic drainage rocks and leached metals are determined. The data obtained made it possible to determine the level of saturation of watercourses with acidic products harmful to environmental factors. Based on the results of geochemical tests, options for the location of rock dumps and the construction of mining and processing industries during the development of the deposit are proposed

Study on H2S Occurrence in Low Sulfur Coal Seams

Coal samples from the Shanxi Shaping coal mine were selected to investigate the occurrence of H2S in low sulfur coal seams. The adsorption mechanism of coal to H2S was explored, and an occurrence equation for H2S in coal seams was fitted through adsorption experiment results. The results showed that under ambient temperature and pressure conditions, the H2S adsorbed by coal reached equilibrium within 24 h. The increase in H2S concentrations and the moisture content of coal samples resulted in an increase in the adsorption capacity of H2S. Chemical adsorption of H2S by the coal also occurred. The total sulfur content in the coal increased, and water promoted the conversion from H2S to sulfur in coal. After adsorption, most of the H2S remains in the coal structure in the form of inorganic sulfur, such as sulfur hydride, iron sulfide sulfur, and monomeric sulfur, and a small proportion of H2S is bonded in the structure of the coal in the form of organic sulfur such as thiophene, C-S-C, and C-SH. Therefore, the higher the total sulfur content in coal, the greater the occurrence of H2S. The total amount of H2S increased exponentially with the concentration of free H2S and the moisture content of coal at equilibrium. This meant that the total amount of H2S in the coal seam could be estimated by fitting an equation according to the concentration of free H2S and the moisture content of coal seams. The concentration of free H2S decreased linearly with the increase in moisture content of the coal, therefore, the concentration of H2S in space could be reduced by injecting water into coal seams.

Trace Element and Isotope Systematics in Vent Fluids and Sulphides From Maka Volcano, North Eastern Lau Spreading Centre: Insights Into Three-Component Fluid Mixing

Back-arc spreading centres and related volcanic structures are known for their intense hydrothermal activity. The axial volcanic edifice of Maka at the North Eastern Lau Spreading Centre is such an example, where fluids of distinct composition are emitted at the Maka hydrothermal field (HF) and at Maka South in 1,525–1,543 m water depth. At Maka HF black smoker-type fluids are actively discharged at temperatures of 329°C and are characterized by low pH values (2.79–3.03) and a depletion in Mg (5.5 mmol/kg) and SO4 (0.5 mmol/L) relative to seawater. High metal (e.g., Fe up to ∼6 mmol/kg) and rare Earth element (REE) contents in the fluids, are indicative for a rock-buffered hydrothermal system at low water/rock ratios (2–3). At Maka South, venting of white smoke with temperatures up to 301°C occurs at chimneys and flanges. Measured pH values range from 4.53 to 5.42 and Mg (31.0 mmol/kg), SO4 (8.2 mmol/L), Cl (309 mmol/kg), Br (0.50 mmol/kg) and Na (230 mmol/kg) are depleted compared to seawater, whereas metals like Li and Mn are typically enriched together with H2S. We propose a three-component mixing model with respect to the fluid composition at Maka South including seawater, a boiling-induced low-Cl vapour and a black smoker-type fluid similar to that of Maka HF, which is also preserved by the trace element signature of hydrothermal pyrite. At Maka South, high As/Co (&amp;gt;10–100) and Sb/Pb (&amp;gt;0.1) in pyrite are suggested to be related to a boiling-induced element fractionation between vapour (As, Sb) and liquid (Co, Pb). By contrast, lower As/Co (&amp;lt;100) and a tendency to higher Co/Ni values in pyrite from Maka HF likely reflect the black smoker-type fluid. The Se/Ge ratio in pyrite provides evidence for fluid-seawater mixing, where lower values (&amp;lt;10) are the result of a seawater contribution at the seafloor or during fluid upflow. Sulphur and Pb isotopes in hydrothermal sulphides indicate a common metal (loid) source at the two vent sites by host rock leaching in the reaction zone, as also reflected by the REE patterns in the vent fluids.