Rhombic Sulfur Research Articles

Temperature dependence of sulfur solubility in dimethyl sulfoxide and changes in concentration of supersaturated sulfur solutions at 25 °C

This is the first systematic study on the isothermal dependence of the solubility of rhombic sulfur in dimethyl sulfoxide at a temperature range of 298–448 K (25–175 °C) using a gravity method. It was found that sulfur solubility is affected not only by the temperature of the solvent, but also by the phase transition of sulfur to monoclinic modification occurring during the dissolution process, as well as by the melting of the rhombic phase of sulfur. It was shown that the concentration of a supersaturated sulfur solution in dimethyl sulfoxide under standard states, obtained by cooling isothermally heated solutions to 298 K (25 °C), increases significantly as the temperature of the isotherm rises, which contrasts with the findings available in the existing literature. Key aspects of sulfur solubility in DMSO are considered.

Multiple sharp terahertz absorption peaks in rhombic sulfur detected using high-resolution terahertz spectroscopy

We investigated rhombic sulfur (S) using a tunable, coherent, terahertz (THz) frequency spectroscopic system (0.6–6.0 THz) herein. At 70 K, we detected unique absorbance peaks in the spectra around 1.3, 2.2, 2.4, 4.5, 5.5, and 5.9 THz, which shifted to higher frequencies with decreasing temperature. Density-functional theory (DFT) calculations revealed unique triple peaks at approximately 5.6, 5.8 and 5.9 THz. The sharp and strong absorbance that produced the multiple peaks can be attributed to intramolecular twisting and deformation vibrations of the S8 ring structure. Many unique peaks originating from intermolecular vibrations of S8 were obtained in the lower-frequency region.

Resource treatment of coking sulfur paste: Characterization analysis and composition of impurities

Coking sulfur paste (CSP) generated from coking oven gas desulfurization process is an extremely harmful pollutant. In this article, modern analytic methods, such as X‐ray fluorescence, X‐ray diffraction, Fourier transform infrared, thermo gravimetric‐differential scanning calorimetry and scanning electron microscope, were utilized to analyze CSP. Results showed that sulfur in CSP mainly existed in the form of elemental sulfur, which is presented mostly in the form of rhombic sulfur (Sα). The rest of sulfur existed in the form of NH4SCN, (NH4)2S2O3, FeSO4. There were also microelements in CSP, such as Fe, Br, Ca, P, Mo and Cl, whose contents were less than 2.50%. Impurities in CSP could be divided into three categories: water‐soluble impurities (WI), dichloromethane‐soluble impurities (DI) and other impurities (OI), accounting for 4.2%, 12.16% and 2.61%, respectively, among the whole CSP. WI is consisted of NH4SCN, (NH4)2S2O3, FeSO4, PDS and hydroquinone accounting for 58.39%, 9.05%, 24.67%, 3.70%, and 3.37%, respectively, of the total WI. DI mainly contained polycyclic aromatic hydrocarbons, including benzenes, naphthalenes, fluorenes, phenanthrenes, anthraquinones and pyrenes. Carbon in OI existed mainly in the form of C–C and C–H, oxygen in OI existed in the form of C=O and C–OH groups. A composite extraction process was proposed to deal with CSP in this paper, which separated sulfur from impurities in CSP at normal temperature efficiently, based on the existing conditions of coking enterprises. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13023, 2019

Comparison of Sulfur Curing Systems (Insoluble-Rhombic) on Physical and Thermal Properties of the Matrix Polymeric of Styrene-Butadiene Rubber and Natural Rubber

Vulcanization, by creating a three-dimensional cross-linked network, improves the physicalmechanical and thermal properties of elastomers. Sulfur is one of the most common vulcanization agents used in the rubber industry. Curing agents used in this research are polymeric sulfur (insoluble sulfur, IS) and rhombic sulfur (RS). These two allotropes of sulfur are compared with regard to their ability to vulcanize styrene- butadiene rubber (SBR) and natural rubber (NR). According to the results obtained on that about curing characterization, was seen, the optimal time for the cure of both intended rubbers gotten with RS, and about the compression set test, obtained similarly result. This while that is about tensile strength, Mooney viscometer and aging tests seen for both rubbers, insoluble sulfur was the best option for curing and about hardness and tear tests were observed, results for SBR were similar and for NR were founded, insoluble sulfur was the best option. About ozone chamber test, all results of the samples were similar. With all these interpretations due to lack of blooming in sulfur polymer, this option is preferred for industrial rubber.

Determination of the most efficient form of sulfur for use as a natural rubber curing agent by comparison of physical and thermal attributes of cured rubber

Vulcanization, by creating a three-dimensional cross-linked network, improves the physicalmechanical and thermal properties of elastomers. A popular agent for curing natural rubber (NR) is sulfur. Insoluble sulfur (IS) and rhombic sulfur (RS) are common allotropes of elemental sulfur. In this research, it was observed that the use of the two types of sulfur (IS and RS) gives different results. In terms of cure behavior, tear resistance and hardness, RS-vulcanized NR performed better, whereas in viscosity, tensile strength, aging and compression set, IS-vulcanized NR was better; because of the lack of blooming, IS could replace of rhombic sulfur as the curing agent in certain applications.

The effects of sulfur curing systems (insoluble-rhombic) on physical and thermal properties of the matrix polymeric of styrene butadiene rubber

Sulfur is one of the most common vulcanization agents used in the rubber industry to create a three-dimensional network between rubber molecules to improve the physical and even thermal properties of the rubber. Curing agents used in this research are polymeric sulfur (insoluble sulfur, IS) and rhombic sulfur (RS). These two allotropes of sulfur are compared with regard to their ability to vulcanize styrene-butadiene rubber (SBR). Similar results are obtained for both curing agents in term of rheological behavior, and physical and thermal properties. Mooney viscometer and aging tests give higher values for IS-vulcanized SBR, whereas RS-vulcanized SBR shows better cure behavior, hardness, tensile strength, tear and compression set, test results. Despite the similar results, insoluble sulfur does not exhibit blooming and may be able to replace rhombic sulfur as a curing agent in the rubber industry.

Моделирование активационного измельчения частиц ромбической серы в дезинтеграторе

Based on the theoretical studies, complete picture of a mechanical processing of sulfur in the disintegrator is given. Kinematic and dynamic characteristics of elastic and inelastic collisions of particles of processed rhombic sulfur with rows of disintegrator fingers are calculated. Based on the analysis of the obtained dependency of the rotation frequency of the rotors offers, advices on selecting optimal conditions for activation milling of α-sulfur in the disintegrator are given. These results can be partially used in the processing of sulfur and in other types of shock grinding devices, in particular, jet mills.

Physicochemical Properties of Rubber Compositions Vulcanized by Polymeric Sulfur

We study the physicochemical properties of rubbers vulcanized by polymeric and rhombic sulfur and determine the structural parameters of their cross-linking networks. It is shown that vulcanizates based on polymeric sulfur obtained as a result of plasma-chemical decomposition of hydrogen sulfide surpass rubbers vulcanized by rhombic sulfur by the main physicomechanical characteristics. It is shown that the migration of sulfur onto the surfaces of rubbers vulcanized by polymeric sulfur does not occur.

Thermodynamic and XRD analysis of arsenopyrite biooxidation and enhancement of oxidation efficiency of gold-bearing concentrates

Gold found in ores may be associated with sulfidic minerals (mainly arsenopyrite and pyrite). The biooxidation of sulfidic minerals is a method to recover gold from these ores. In this study, the biooxidation of arsenopyrite was investigated, and a method to increase the biooxidation of sulfidic concentrates was proposed. It was demonstrated that thin sections of single crystals of arsenopyrite were oxidized more efficiently when a microbially produced Fe3+ containing solution was used than when solutions of Fe2(SO4)3 ·9H2O were used. In the latter case, the crystal structure of the elemental sulfur was markedly different from rhombic sulfur. Studies on the biooxidation of pure arsenopyrite and sphalerite indicated that a layer of elemental sulfur was formed on its surface. This product of biooxidation was identified as elemental sulfur with a β-modification similar to that of selenium. The microorganisms used in this study were demonstrated to alter the crystal structure of sulfur prior to the oxidation thereof, independent of the type of mineral.During the initial stages of the biooxidation of sulfidic minerals, the ferric iron destroys the bonds on the surface of the crystal lattice. The disrupted surface structure of the sulfides promotes the solubilization of ferrous iron and trivalent arsenic (for arsenopyrite) and enhances the electron flow from the surface to the solution; microbial enzyme systems subsequently transfer these electrons to molecular oxygen.The separation of biooxidation of gold-containing pyrite/arsenopyrite concentrates into the component chemical and biological steps makes it possible to conduct each of the steps under optimal conditions. The two-step oxidation was demonstrated to be significantly more efficient under batch conditions than the standard one-step biooxidation. The oxidation level of arsenopyrite increased from 76.6 to 93.3%.

Sulfidization of lacustrine glacial clay upon Holocene marine transgression (Arkona Basin, Baltic Sea)

Towards the end of the last deglaciation more than 13,500years ago the southern Baltic Sea was a freshwater lake, the Baltic Ice Lake, for several thousand years during which iron-rich, organic-poor clay was deposited. The modern brackish-marine stage started about 8600years ago with the deposition of organic-rich mud, which is today characterized by high rates of sulfate reduction and high concentrations of free sulfide. We studied the iron–sulfur diagenesis in gravity cores from the Arkona Basin, SW Baltic Sea, to track the progressing sulfidization front in the buried Ice Lake sediment. The geochemical zonation was unusual as the sulfate concentration dropped steeply by two thirds below which it increased again due to a deep sulfate reservoir. The reservoir had been established during the early Holocene marine period as sulfate and other seawater ions diffused down into the lake sediment for several thousand years. Sulfur isotope analyses confirmed its origin as seawater sulfate, while its oxygen isotope composition indicated a microbially catalyzed equilibration with ambient interstitial water, decoupled from net sulfate reduction. Today, hydrogen sulfide diffuses from the marine mud down into the lake sediment where a black band with high magnetic susceptibility and high iron monosulfide, greigite and elemental sulfur content shows progressing sulfidization of the large pool of solid-phase reactive iron. Dissolved iron from the deep Ice Lake sediment diffuses up to the sulfide front and provides a small supplement to the solid Fe(III) pool as a sulfide sink. Pyrite formation at the sulfidization front may involve surface-bound zero-valent sulfur while, above the front, polysulfides are in equilibrium with the system hydrogen sulfide – polysulfide – rhombic sulfur and may not be important for further pyrite formation. The Holocene iron–sulfur diagenesis observed in the Arkona Basin represents an important transitional state for post-glacial transgressions with organic-rich marine sediment overlying lacustrine clay, such as in other areas of the Baltic Sea or in the Black Sea.

Potential Use of Petroleum-based Sulfur in Rubber Industry

Potential use of petroleum-based sulfur generally classified as a by-product from refinery process is investigated as vulcanizing agent in rubber, and compared with commercial rhombic sulfur. Styrene-butadiene rubber (SBR) and nitrile rubber (NBR) are used as rubber matrices. Results obtained show that, between 2 types of sulfurs, the SBR system reveals similarity in cure behaviors whereas the NBR system demonstrates faster cure behavior when vulcanized by petroleum-based sulfur. However, rheological properties, mechanical properties, and dynamic mechanical properties of both rubbers show comparable results regardless of sulfur type. The results suggest the strong potential utilization of petroleum-based sulfur as vulcanizing agent as an alternative to the commercial rhombic sulfur usually used in rubber vulcanization.

Effectiveness of By-product Sulfur from Petroleum Refining as a Rubber Vulcanizing Agent: A XANES Investigation

Sulfur plays an important role in the rubber industry as a vulcanizing agent, providing an enhancement in mechanical properties relative to unvulcanized rubber. The sulfur used in industry originates from natural and petroleum sources. Petroleum-based sulfur (PS), usually a by-product from a refinery process, was used as the vulcanizing sulfur in the present work. The chemical structure of PS was characterized and compared to that of a commercial rhombic sulfur (RS) using sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The results reveal that sulfur K-edge XANES spectroscopy has good sensitivity to the chemical structure of sulfur, and the chemical structures of sulfur in rubbers vulcanized with PS and RS are very similar. Furthermore, different types of rubbers vulcanized with PS or RS exhibit comparable mechanical properties. This work shows that PS can be used to replace RS as a vulcanizing agent for rubber.

Intermediate sulfur oxidation state compounds in the euxinic surface sediments of the Dvurechenskii mud volcano (Black Sea)

The deep Black Sea is known to be depleted in electron-acceptors for sulfide oxidation. This study on depth distributions of sulfur species (S(II), S(0), Sn2-, S2O32-, SO32-, SO42-) in the Dvurechenskii mud volcano, a cold seep situated in the permanently anoxic eastern Black Sea basin (Sorokin Trough, 2060m water depth), showed remarkable concentrations of sulfide oxidation products. Sulfite concentrations of up to 11μmolL−1, thiosulfate concentrations of up to 22μmolL−1, zero-valent sulfur concentrations of up to 150μmolL−1 and up to five polysulfide species were measured in the upper 20cm of the sediment. Electron-acceptors found to be available in the Dvurechenskii mud volcano (DMV) for the oxidation of hydrogen sulfide to sulfide oxidation intermediates are iron-minerals, and probably also reactive manganese phases. Up to 60μmolg−1 of reactive iron-minerals and up to 170μmolL−1 dissolved iron was present in the central summit with the highest fluid upflow and fresh mud outflow. Thus, the source for the oxidative power in the DMV are reactive iron phases extruded with the mud from an ancient source in the deeply buried sediments, leading to the formation of various sulfur intermediates in comparably high concentrations. Another possible source of sulfide oxidation intermediates in DMV sediments could be the formation of zero-valent sulfur by sulfate dependent anaerobic microbial oxidation of methane followed by disproportionation of zero-valent sulfur. Sulfide oxidation intermediates, which are produced by these processes, do not reach thermodynamic equilibrium with rhombic sulfur, especially close to the active center of the DMV due to a short equilibration time. Thus, mud volcano sediments, such as in the DMV, can provide oxidizing niches even in a highly reduced environment like the abyssal part of the Black Sea.

Geometric analysis of the models of sulfur (S8) x molecular nanoclusters in computer experiment

A version of a computer nanoscope is proposed for single crystals with the known atomic structure for a detailed analysis of surface coordination bonds forming on nanosized nuclei due to the intermolecular interaction. Different stages of the study of rhombic and monoclinic sulfur (from the atomic/molecular structure on the first stage to the model packing growth polyhedra on the final stage) are analyzed. The calculation results of the coordination numerical sequences revealed in the computer experiment when the coordination spheres are filled with S8 molecules with the formation of rather large molecular clusters with a size of about 10 nm or more are presented.

Formation and characterization of CuxS layers on polyethylene film using the solutions of sulfur in carbon disulfide

Abstract Results of the formation of copper sulfide layers using the solutions of elemental sulfur in carbon disulfide as precursor for sulfurization are presented. Low density polyethylene film can be effectively sulfurized in the solutions of rhombic (α) sulfur in carbon disulfide. The concentration of sulfur in polyethylene increases with the increase of the temperature and concentration of sulfur solution in carbon disulfide and it little depends on the duration of sulfurization. Electrically conductive copper sulfide layers on polyethylene film were formed when sulfurized polyethylene was treated with the solution of copper (II/I) salts. CuxS layer with the lowest sheet resistance (11.2 Ω cm−2) was formed when sulfurized polyethylene was treated with copper salts solution at 80°C. All samples with formed CuxS layers were characterized by X-ray photoelectron spectroscopy. XPS analysis of obtained layers showed that on the layer’s surface and in the etched surface various compounds of copper, sulfur and oxygen are present: Cu2S, CuS, CuO, S8, CuSO4, Cu(OH)2 and water. The biggest amounts of CuSO4 and Cu(OH)2 are present on the layer’s surface. Significantly more copper sulfides are found in the etched layers.

Dynamics of zero-valent sulfur species including polysulfides at seep sites on intertidal sand flats (Wadden Sea, North Sea)

Zero-valent sulfur species dynamics in tidal flat pools of Wadden Sea (North Sea) were studied. Concentrations of solid sulfur, colloidal sulfur of different particle sizes and distribution of inorganic polysulfide species were detected near the bottom of different pools as a function of time after detachment of the pool from sea. Concentrations of these species were detected also in the incubated sediment cores taken from the same site with the pumping of anoxic seawater, anoxic seawater spiked with sulfide and anoxic seawater spiked with lactate. Sulfide concentration in the pool increased during the first 2 h of pool detachment from the sea to a maximum of 273 µM. Polysulfides were present at the beginning of the detachment of the pool and higher concentrations of elemental sulfur and polysulfides lead to more rapid coagulation and precipitation of dispersed solid sulfur. The process of the formation of zero-valent sulfur began with the formation of polysulfides and colloidal sulfur with a particle size less than 5 μm. Further coagulation led to an increase in the amount of colloidal sulfur with the particle size more than 5 μm followed by crystallization of solid sulfur particles. Maximum concentration of colloidal sulfur detected in the pools was 73 µM and that of solid sulfur was 25 µM. Maximum concentration of the sum of all polysulfide species measured was 5.9 µM, which corresponded to 23.1 µM of detected polysulfide sulfur or to 27.7 µM of polysulfide sulfur taking into account the calculated concentrations of species with concentration under detection limit. Polythionates were not detected. Levels of total zero-valent sulfur usually reached the value of 40 µM, but can be even higher than 100 µM. This depended on the overall concentration of sulfide. In the tidal pools, polysulfide chain lengths were short and the polysulfide system was found not to be in equilibrium with solid or colloidal sulfur at any time of pool detachment from sea. Flow-through incubation experiments, however, exhibited polysulfide in equilibrium with respect to rhombic sulfur. No difference in the polysulfide speciation was observed in experiments where sulfide was artificially added and sulfide was produced through enhanced bacterial sulfate reduction. The differences were attributed to the kinetics and to competing oxidation processes present in the exposed Wadden Sea tidal pools as compared to the longer running and more restricted incubation experiments.

Solubility of cyclooctasulfur in pure water and sea water at different temperatures

The solubility of cyclooctasulfur in water and sea water at various temperatures in the range between 4 and 80 °C was determined. Cyclooctasulfur in equilibrium with rhombic sulfur reacted with hot acidic aqueous potassium cyanide to form thiocyanate anion which was measured by anion chromatography. Sulfur solubility in pure water was found to increase with temperature by more than 78 times: from 6.1 nM S 8 at 4 °C to 478 nM S 8 at 80 °C. The following thermodynamic values for solubilisation of S 8 in water were calculated from the experimental data: K° = 3.01 ± 1.04 × 10 −8, Δ G r° = 42.93 ± 0.73 kJ mol −1, Δ H r° = 47.4 ± 3.6 kJmol −1, Δ S r° = 15.0 ± 11.7 J mol −1 K −1). Solubility of cyclooctasulfur in sea water was found to be 61 ± 13% of the solubility in pure water regardless of the temperature.

Reduced sulfur species in a stratified seawater lake (Rogoznica Lake, Croatia); seasonal variations and argument for organic carriers of reactive sulfur

Over a period of a year, Hg 0-reactive, total reduced sulfur species (RSS T), as well as a non-volatile fraction that cannot be gas-stripped at pH ∼2 (RSS NV), have been measured by voltammetry in a stratified, saline lake. In the hypolimnion, RSS T is dominated by unusually high (up to 5 mM) dissolved divalent sulfur (S −II), present as H 2S + HS − and as inorganic polysulfides (H x S n x −2). Less abundant RSS NV is attributed to dissolved zero-valent sulfur (S 0) in inorganic polysulfides. Assuming negligible contribution of organic S 0 species in the hypolimnion, the equilibrium distribution of polysulfide ions is calculated; S 5 2− is found to predominate. In the epilimnion, all RSS T consists of RSS NV within analytical uncertainty. Through spring and summer, RSS T and RSS NV display little vertical or seasonal variation, but they increase dramatically when stratification breaks down in autumn. Based on decay rate, RSS during mixing events is attributed to dissolved S 8 from oxidation of sulfide and decomposition of inorganic polysulfides. This hypothesis quantitatively predicts precipitation of elemental sulfur in a year when colloidal sulfur was observed and predicts no precipitation in a year when it was not observed. Except during mixing events, the entire water column is undersaturated with respect to both rhombic sulfur and biologic sulfur, and the limited variations of RSS exclude hydrophobic and volatile aqueous S 8 as a major species. During such periods, RSS (typically 8 nM) may be associated with organic carbon, perhaps as adsorbed S 8 or as covalently bound polysulfanes or polysulfides. The hypolimnion is viewed as a zero-valent sulfur reactor that creates S 0-containing, dissolved organic macromolecules during stable stratification periods. Some are sufficiently degradation-resistant and hydrophilic to be dispersed throughout the lake during mixing events, subsequently giving rise to ∼10 −8 M RSS in the oxic water column. Voltammetrically determined RSS in oxic natural waters has often been described as “sulfide” or “metal complexed sulfide”, implying an oxidation state of S −II; we argue that RSS in oxic Rogoznica Lake waters is mainly S 0.

Zero-Valent Sulfur and Metal Speciation in Sediment Porewaters of Freshwater Lakes

We measured the aqueous solubility of rhombic sulfur and used this information to incorporate, in speciation codes, the thermodynamic constants reported in the literature for the formation of polysulfide complexes. Using the values of pH and total concentrations of dissolved zerovalent sulfur, sulfide, humic substances, trace metals (Ag, Cd, Cu, Hg, methylmercury, Pb, Zn) and major ions measured in anoxic porewaters of nine oligotrophic Canadian lakes as input to these speciation codes, we show that the porewaters of these lakes are undersaturated or close to saturation with respect to rhombic sulfur and that sulfide and polysulfide ligands play a dominant role in controlling metal speciation in freshwater anoxic environments when they are present at micromolar levels. The study also highlights the need for further research on the formation constants of metal complexes with sulfide and polysulfides.

Muoniated radical states in the group 16 elements: Computational studies

Recent experimental studies on positive muon implantation in silicon, selenium, and tellurium have been interpreted on the basis that the primary paramagnetic species observed is XMu ( X = S , Se, or Te), the muonium-substituted analog of the appropriate diatomic chalcogen monohydride radical. However, temperature-dependent signal visibility, broadening, and hyperfine shift effects remain puzzling. The interplay of degeneracy, spin–orbit coupling, and vibrational averaging in these species makes them computationally challenging despite their small size. In this work computational studies are carried out on all hydrogen isotopomers of the series OH, SH, SeH, and TeH. Several different methodological approaches are compared, and the effects of wavefunction symmetry, spin–orbit coupling, and zero-point vibrational corrections on the isotropic and anisotropic components of the hyperfine interaction are examined. Additionally, some models of the Mu site in rhombic sulfur are briefly considered.