Valence States Of Sulfur Research Articles

Hg0 removal performance of magnetic raffinate slag-based sorbents: Mechanism study on oxidation modification

The sulfur-containing carbon-based sorbent was regarded as potential sorbent for the removal of toxic elemental mercury (Hg0). However, due to its lower reaction temperature and the stronger Hg0 oxidation capacity of oxides at higher temperature, oxidation modification on sulfur-containing raffinate slag-based sorbents was proposed in the study. The effects of O2, H2O2 and KMnO4 oxidation modification on Hg0 removal performance and physicochemical properties of sorbents were investigated. The oxidation modification had little effect on pore structure of sorbents, but mainly affected the content and valence state of sulfur and oxygen elements. Compared with H2O2 oxidation, KMnO4 oxidation was more conducive to forming active lattice oxygen (Oα). The valence state of manganese bound with Oα influenced Hg0 capture a lot, and Oα in MnO2 showed strong oxidation capacity to Hg0. Active S22−and Oα in A850-0.1KMnO4-12h sorbent could both promote the Hg0 removal with HgS and HgO formed in used sorbent. The saturated magnetization of A850-0.1KMnO4-12h sorbent was 5.39 emu·g−1, making it possible to separate mercury-containing sorbents from fly ash. It showed good resistance to low concentration of SO2, and NO could promote its Hg0 removal ability. Meanwhile, KMnO4 oxidation successfully improved the Hg0 removal performance at higher reaction temperature and gas hourly space velocity.

No detectable redox exchange between sulfur and iron during rapid cooling of basalts

The valence states of iron and sulfur in mantle-derived melts influence and respond to the composition of the mantle as well as the subsequent evolution of those melts in Earth's crust. Characterizing the valence states of iron and sulfur in silicate melts that have quenched to form glasses is therefore critical to understanding the composition of the mantle and the magmatic processes that take place before and during volcanic eruptions. Glasses quenched from silicate melts offer the opportunity to precisely measure sulfur and iron valence states, but whether the transition from melt to glass affects the valence state of sulfur and iron is uncertain. Here, we use the glassy margins of two pillow basalts, one from a mid-ocean ridge and one from a back-arc basin, as a natural experiment to test the effect of quench rate on sulfur and iron valence states. We report micro-X-ray Absorption Near Edge Structure (XANES) measurements of S6+/ΣS (S6+/[S6++S2−]) and Fe3+/ΣFe (Fe3+/[Fe2++Fe3+]) along transects from the rapidly quenched rims of the pillows down into the slowly cooled crystal-rich interiors. The range of average quench rates estimated for our selected analysis areas range from 1.2×105°C/sec at the pillow margin to 1.1°C/sec in the interior and span quench rates experienced by natural and experimental glasses. On average, S6+/ΣS = 0.09±0.01 and Fe3+/ΣFe = 0.147±0.002 in the mid-ocean ridge sample and S6+/ΣS = 0.21±0.01and Fe3+/ΣFe = 0.153±0.004 in the back-arc sample, where the quoted uncertainty is the 1σ standard deviation of n= 9-16 analyses. We find that the S6+/ΣS and Fe3+/ΣFe values along transects in each sample show no systematic changes with depth, and by proxy, no systematic changes with quench rate. In each pillow, all measured S6+/ΣS and Fe3+/ΣFe ratios are within the absolute uncertainty of each technique. We propose that these observations are consistent with either sluggish reaction kinetics between sulfur and iron, or an insignificant temperature effect on sulfur-iron redox exchange equilibria. These observations demonstrate that sulfur and iron valence states in glasses with varying quench rates can be directly compared, and that changes in sulfur and iron valence during quench are below the limits of detection with XANES.

Contributions of trans-magmatic fluid in the formation of porphyry copper deposits: A case study from the Baoshan deposit, South China

The classical mechanism “source-transport-storage” of the formation of porphyry copper deposit has been advanced in recent studies, as the “source” is not the main factor for the mineralization in some Cu deposits, and the metallogeny may be affected by other variables factors during the magma-fluid transportation or storage. We recommend the essential role of trans-magmatic fluid in the ore-forming process, this fluid is released from the melting of the sedimentary overlying the subducted plate with high water and volatiles concentrations and high oxygen fugacity. The Baoshan granodioritic cryptoexplosion breccia representing the influence of hydrothermal events as well as the unaltered Baoshan granodiorite porphyry are conducted by LA-MC-ICP-MS analysis, to identify the contribution of trans-magmatic fluid. In case of the εNd(t) of whole rock do not increase with the MgO increasing and SiO2 decreasing, the large variations of zircons εHf(t) values in Baoshan granodiorite porphyry (BGP, −14.24 to −6.38) and Baoshan granodioritic crypto-explosion breccia (BGCB, −25.24 to −6.62) were considered to be the interaction of partial melting of ancient mafic lower crust and Neoproterozoic juvenile crust. However, the copper mineralization requires high oxygen fugacity and a large amount of water, according to the tectonic settings of Baoshan, we recommend that it is the trans-magmatic fluid trapping and concentrating Cu from the whole pluton during the upwelling driven by magma convection. The initial magma was stalled by the ductile-brittle transition at shallow depths of upper-crust. The trans-magmatic fluid leads to the pressure increases at the top of the initial magma, then the overlying rock is ruptured and cryptoexplosion produced. Moreover, after the cryptoexplosion, the sudden reduction of circumference temperature and pressure leads to the decrease in the oxygen fugacity of the ore-forming system, which will change the valence state of sulfur from S6+ to S2−. Finally, sulfur precipitates with chalcophile elements like copper in the metallogenic system and forms porphyry copper deposits with the low Sr/Y ratio. This study highlights the use of trans-magmatic fluid and ductile-brittle transition in the formation of the Baoshan porphyry copper deposits.

Making the Best of Polymers with Sulfur-Nitrogen Bonds: From Sources to Innovative Materials.

Polymers with sulfur-nitrogen bonds have been underestimated for a long time, although the intrinsic characteristics of these polymers offer a myriad of superior properties (e.g., degradation, flame retardancy, film-forming ability, good solubility in polar solvents, and high refractivity with small chromatic dispersions, among other things) compared to their carbon analogues. The remarkable characteristics of these polymers result from the unique chemical properties of the sulfur-nitrogen bond (e.g., its polar character and the multiple valence states of sulfur), and thus open excellent perspectives for the development of innovative (bio)materials. Accordingly, this review describes the most common chemical approaches toward the efficient synthesis of these ubiquitous polymers possessing diverse sulfur-nitrogen bonds, and furthermore highlights their applications in multiple fields, ranging from biomedicine to energy storage, with the aim of providing an informative perspective on challenges facing the synthesis of sulfur-nitrogen polymers with desirable properties.

Effect of copper and iron ions on the sulphidizing floatation of copper in copper smelting slag

This study investigates the influence of Na2S, CuSO4 and FeCl3 on sulphidizing floatation of copper in copper smelting slag. The results show that copper has a good floatability, independent of the addition of Na2S and Cu2 + ions, while Fe3+ inhibits the floatation. In the pH range between 2 and 4, in conditions with Na2S and Cu2 + ions addition, the recovery rate of metal copper rapidly increased and maintained the high level. But the inhibition effect of Fe3+ was enhanced with the increasing of the concentration. Further analysis shows that the Cu2+ and Fe3+ both enhance the surface potential, but with addition of Na2S, Fe3+ and Cu2+ get an opposite effect. Sodium sulfide would formed polysulfide, Monosulfides and polysulfides on solid surface. The addition of Cu2+ would not increase the adsorption amount of S2p on Cu surface and Fe3+ would not only oxidized sulfur ions thus reduce the adsorption and change the valence state of sulfur, but also oxidized metallic copper.

Controllable Sulfoxidation and Sulfenylation with Organic Thiosulfate Salts via Dual Electron- and Energy-Transfer Photocatalysis

Sulfoxides and sulfides are two important functional groups in organic molecules, containing different valence states of sulfur. Both sulfoxidation and sulfenylation with common sulfurating reagents were successfully tuned via a facile variation of the atmosphere under photocatalyzed conditions. The sulfoxidation and sulfenylation transformations involved tandem electron-/energy-transfer and single-electron-transfer processes, respectively. Late-stage sulfoxidation for pharmaceuticals and sugar derivatives was established to be highly compatible. Divergent formal syntheses of sulfoxide/sulfide-containing marketed pharmaceuticals were switchably implemented. Gram-scale operations further demonstrated the practicability of the protocol.

Influence of sulfur on the fermentation characteristics of corn distiller's dried grains with solubles in in vitro culture

The effects of sulfur on the fermentation characteristics of corn distiller’s dried grains with solubles (DDGS) in in vitro culture were investigated. Samples (DDGS) were analyzed for nutrient values and then two independent in vitro experiments were conducted to study the effects of various sulfur sources (Na<sub>2</sub>S, Na<sub>2</sub>S<sub>2</sub>O<sub>4</sub>, Na<sub>2</sub>SO<sub>3</sub>, and Na<sub>2</sub>SO<sub>4</sub>) and different sulfur levels (0.346, 0.692, and 1.038%) on the fermentation characteristics of DDGS. Based on sampling and chemical composition analysis, there existed a great variation in the concentrations of sulfur and proximate nutrients of DDGS. In Experiment 1, sulfur source showed a significant (P < 0.01) effect on the gas production parameters (asymptotic gas production (b) and gas production rate (c)) and gas production of DDGS – sulfur from Na<sub>2</sub>SO<sub>4</sub> and Na<sub>2</sub>S produced more (P < 0.01) gas within 48 h with a faster gas production rate as well as higher digestibilities (dry matter degradability and organic matter digestibility) and more energy supplies (metabolizable energy), net energy for maintenance and gain, and net energy for gain than sulfur from Na<sub>2</sub>SO<sub>3</sub> and Na<sub>2</sub>S<sub>2</sub>O<sub>4</sub>. Neither ammonia-nitrogen (NH<sub>3</sub>-N) concentration nor volatile fatty acids (VFA) profile (total VFA and individual VFA proportion) were affected by sulfur source (P > 0.05). In Experiment 2, no significant (P > 0.05) effect on the fermentation characteristics of DDGS with increasing sulfur content was found. The collective findings suggest that regular chemical analyses are necessary to make full use of DDGS, and that the valence state of sulfur in DDGS exerts an effect on its in vitro fermentation characteristics and there appears no dose-related effect of sulfur on the fermentation of DDGS in a short-term in vitro culture.

Interaction between electrode materials Sr2FeCo0.5Mo0.5O6−δ and hydrogen sulfide in symmetrical solid oxide fuel cells

Symmetrical Solid Oxide Fuel Cells (SSFCs) are highly competitive options for a sustainable energy future, however, its application is hindered by the development of more surfer tolerance and highly efficient electrodes. Sr2FeCo0.5Mo0.5O6−δ (SFCM) was investigated as potential electrode materials for SSFCs using H2S as a fuel directly. SFCM powders, before and after exposure to 0.05% H2S/N2, were carried out to analyze the structure and morphology by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). A maximum power density of 45.69 mW cm−2 was obtained in the configuration of SSFC (SFCM/LSGM/SFCM) in 0.05% H2S/N2 at 800 °C. SFCM had high catalytic activity in converting H2S into SO2 without obviously deactivation. After cell test, X-ray photoelectron spectroscopy (XPS) was used to reveal the distribution of valence state of sulfur. There founding demonstrated that the SSCM has a certain surfer tolerance ability, and that understanding how the electrodes works and impact the cell performance is critical to the design of highly stable double perovskite electrodes.

Thermodynamic Research of S-H<sub>2</sub>O System in Sodium Aluminate Solution

There are many different types of valence of sufur in aluminate sodium solution during the process of the bauxite dissolution, which mainly including S2-, S22-, S, S2O32-, SO32-, SO42- and it may have an effect on the mineral dissolution process. Therefore, it is necessary that the thermodynamic properties of S-H2O system were investigated in sodium aluminate solution. In this paper, the reactions between different valence states of sulfur and lye (with or without oxygen participation) were studied in sodium aluminate solution. The thermodynamic software Factsage 7.0 was carried out to calculate the standard reaction Gibbs free energy (ΔGTθ). The results showed that S2- and SO42- are the most stability in terms of the autoreactive reaction of different valence states at 298-573 K, and that the stability of different valence states of sufur order is “S22- >(S2O32-, SO32-) >S”. At 523 K, SO32- is more stable than S2O32-. On the other hand, the low-valent sulfur was more likely to be oxidized into SO42- under oxidizing conditions at 298-573 K. Besides, it was also found that S22- is most susceptible to oxidation because of the lowest stability. Finally, the stability of the other valence states of sulfur under oxidizing conditions order is “SO32- >S2O32- >S2- >S”.

Synthetic and Structural Studies of 1,8‐Chalcogen Naphthalene Derivatives

Four novel 1,8-disubstituted naphthalene derivatives 4-7 that contain chalcogen atoms occupying the peri positions have been prepared and fully characterised by using X-ray crystallography, multinuclear NMR spectroscopy, IR spectroscopy and MS. Molecular distortion due to noncovalent substituent interactions was studied as a function of the bulk of the interacting chalcogen atoms and the size and nature of the alkyl group attached to them. X-ray data for 4-7 was compared to the series of known 1,8-bis(phenylchalcogeno)naphthalenes 1-3, which were themselves prepared from novel synthetic routes. A general increase in the E...E' distance was observed for molecules containing bulkier atoms at the peri positions. The decreased S...S distance from phenyl-1 and ethyl-4 analogues is ascribed to a weaker chalcogen lone pair-lone pair repulsion acting in the ethyl analogue due to the presence of two equatorial S(naphthyl) ring conformations. Two novel peri-substituted naphthalene sulfoxides of 1, Nap(O=SPh)(SPh) 8 and Nap(O=SPh)(2) 9, which contain different valence states of sulfur, were prepared and fully characterised by using X-ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. Molecular structures were analysed by using naphthalene ring torsions, peri-atom displacement, splay angle magnitude, S...S interactions, aromatic ring orientations and quasi-linear O=S...S arrangements. The axial S(naphthyl) rings in 8 and 9 are unfavourable for S...S contacts due to stronger chalcogen lone pair-lone pair repulsion. Although quasi-linear O=S...S alignments suggest attractive interaction is conceivable, analysis of the B3LYP wavefunctions affords no evidence for direct bonding interactions between the S atoms.

Effects of S doping on electronic structures and photocatalytic properties of anatase TiO2

The crystal structure, impurity formation energy, electronic structure and optical properties of anatase TiO2 doped with sulfur in different valence states were studied by using the plane-wave ultrasoft pseudopotential method based on first_principles. The calculations shown that the existence form of sulfur element in anatase TiO2 was related to the experimental conditions; the octahedral dipole moments were increased due to the changes of lattice parameters, bond length and charges on atoms; the band gap narrowed and the curves of light absorption red-shifted to visible-light region due to the position of conduction band downward shifting, the position of valence band upper shifting and the width of valence band broadening result from hybridizing S 3p states with O 2p states and Ti 3d states. All of these results can explain the better photocatalytic properties of S-doped anatase TiO2 in visible-light region. According to these results, the effects on electronic structures and photocatalytic properties of anatase TiO2 doping with different valence states of sulfur were compared and analyzed.

Sulfur speciation and network structural changes in sodium silicate glasses: Constraints from NMR and Raman spectroscopy

Information about the state of sulfur in silicate melts and glasses is important in both earth sciences and materials sciences. Because of its variety of valence states from S 2− (sulfide) to S 6+ (sulfate), the speciation of sulfur dissolved in silicate melts and glasses is expected to be highly dependent on the oxygen fugacity. To place new constraint on this issue, we have synthesized sulfur-bearing sodium silicate glasses (quenched melts) from starting materials containing sulfur of different valence states (Na 2SO 4, Na 2SO 3, Na 2S 2O 3 and native S) using an internally heated gas pressure vessel, and have applied electron-induced SKα X-ray fluorescence, micro-Raman and NMR spectroscopic techniques to probe their structure. The wavelength shift of SKα X-rays revealed that the differences in the valence state of sulfur in the starting compounds are largely retained in the synthesized sulfur-bearing glasses, with a small reduction for more oxidized samples. The 29Si MAS NMR spectra of all the glasses contain no peaks attributable to the SiO 4-nS n (with n > 0) linkages. The Raman spectra are consistent with the coexistence of sodium sulfate (Na 2SO 4) species and one or more types of more reduced sulfur species containing S-S linkages in all the sulfur-bearing silicate glasses, with the former dominant in glasses produced from Na 2SO 4-doped starting materials, and the latter more abundant in more reduced glasses. The 29Si MAS NMR and Raman spectra also revealed changes in the silicate network structure of the sulfur-bearing glasses, which can be interpreted in terms of changes in the chemical composition and sulfur speciation.

Speciation of sulfur in individual aerosol particles from work places by wavelength-dispersive electron-probe microanalysis.

The oxidation state of sulfur has been determined by measuring the energy shift of the S K(alpha) line by wavelength-dispersive electron-probe microanalysis. On flat polished samples the energy shift between sulfate (S(+6)) and sulfide (S(-2)) was 1.3 eV, in good agreement with previous literature data. The observed energy shift of the S K(alpha) line is dominated by the change of the valence state of sulfur--the effects of co-ordination geometry and nearest neighbours are small. The relationship between the energy shift of the S K(alpha) line and the oxidation number of sulfur is linear, to a first approximation. The effect of particle geometry on the position of the S K(alpha) line is usually small and introduces an error of approximately half an oxidation number. The apparent sulfur valence states observed for individual aerosol particles from work places in a nickel refinery are highly variable and most probably result from different mixtures of the two end-members sulfide and sulfate.

Intramolecular S⋯S and S⋯O close contacts in 1,8-bis(phenylsulfanyl)naphthalene derivatives of different sulfur valence state: an X-ray study

Four peri-substituted naphthalene derivatives, 1,8-bis(phenylsulfanyl)naphthalene (1), 1,8-bis[(2-methoxycarbonylphenyl)sulfanyl]naphthalene (2), bis[(2-methoxycarbonyl-phenyl)-sulfinyl]naphthalene (3) and bis[(2-methoxycarbonylphenyl)sulfonyl]naphthalene (4) with different valence states of sulfur were prepared and their molecular structures determined by X-ray diffraction. Data were collected on CAD-4 diffractometers with monochromated MoKα and CuKα radiations. Naphthalene ring torsions, aromatic ring orientations, S⋯S and S⋯O close contacts were analyzed and the controlling factors established. In both halves of the molecules, the naphthyl and phenyl rings assume axial–equatorial positions in bis-sulfides 1 and 2, and twist-axial positions in bis-sulfoxide 3 and bis-sulfone 4. The S⋯S distance was found to be 3.01, 3.18; 3.01 and 3.53Å, for 1, 2, 3 and 4, respectively. The equatorial S-phenyl rings in 2 and the steric crowd in 4 are unfavorable factors for S⋯S contacts. As expected, S(II)⋯O and S(IV)⋯O close contacts are formed in the equatorial and axial S-phenyl rings of 2 and 3, respectively, with 2.72, 2.73 and 2.77, 2.83Å distances. Steric repulsion in bis-sulfone 4 is moderated by two C(ar)–S(VI)⋯O(sulfonyl) type close contacts (2.89 and 3.02Å), which join the two halves of the molecule.

Sulfided Pt Catalysts: Monitoring Surface Chemical State and Catalytic Properties in n-Hexane Reactions

The amount and valence state of sulfur in sulfided Pt catalysts was monitored, together with parallel studies of the catalytic properties of these catalysts in order to clarify the catalytic effect of S in different chemical states on reactions of low-temperature n-hexane reforming. Pt black and 6% Pt/SiO2(EUROPT-1) were sulfided by H2/H2S. X-ray photoelectron spectroscopy (XPS) detected both sulfate and sulfide. The chemical state of Pt corresponded to metallic Pt with low amounts of S containing surface adlayer and/or PtS present. This could be observed with Pt black and also with EUROPT. With S present, both catalysts lost ca 95% of their activity in n-hexane transformation at 603 K, n-hexenes being the predominant products. Prolonged runs with n-hexane as well as regenerations using O2and H2removed most sulfidic S from Pt black and about half of the original activity came back. Isomers and methylcyclopentane were produced in this state with high selectivities. Some reactivation of EUROPT (where no sulfate could be detected) occurred within one single run. A uniform scheme is proposed to describe the effects of sulfate and sulfide. Accordingly, sulfate acts as a structural modifier occupying a fraction of the active surface. Sulfide in small amounts, in turn, has a bonding modifier effect and poisons selectively benzene and fragmentation, enhancing (within the reduced activity) the selectivity of C5-cyclization and, possibly, also that of isomerization.

Auger parameters for sulfur-containing compounds using a mixed aluminum-silver excitation source

A mixed X-ray source (Al Kα-Ag L) has been used to obtain the precise Auger parameters (S2 p 3 2 -S KL 23L 23) for about sixty sulfur-containing compounds. A two-dimensional chemical state plot for the identification of the valence state of sulfur in a compound and of the specific sulfur-containing compound is presented.

X-ray fluorescence analysis of the concentration and valence state of sulfur in pollution samples

Two special X-ray spectrometers have been developed for the measurement of sulfur pollution. One of them is a portable instrument which uses a 50 W aircooled X-ray tube and a vacuum spectrometer with a NaCl crystal. It can detect 0.5μg/cm 2 of S in 100-s counting interval. The other instrument is specifically for the measurement of valence state of sulfur. It consists of a replacement channel for the multiple-crystal spectrometer instrument used by the Environmental Protection Agency for routine analysis. With this replacement channel details of the sulfur spectrum can be scanned or the crystal may be set for the sulfate Kβ satellite for routine determination of the sulfate fraction of total sulfur.