Aqueous Sulfide Solutions Research Articles

Enhancing zero-valent iron (ZVI) pulverization during mechanical milling: FeSx as milling aids

A critical problem in the production of ultrafine zero-valent iron (ZVI) using mechanical milling is that the metallic iron (main component of ZVI) is ductile and can withstand severe plastic deformation, which leads to the slow pulverization of ZVI during its milling. In this work, we introduce non-ductile particle solids (FeSx) as milling aids to enhance the pulverization of the ductile ZVI, and find that the addition can improve the pulverization. The result is verified in three different ways through which the milling aids (FeSx) are introduced, namely, the addition of the FeSx solid directly, the use of the FeSx that is formed during the milling using aqueous sulfide solution as milling solvent with and without the addition of ferrous ion. The ZVI particles are pulverized to hundreds of nanometers using the milling aids, while the particles are deformed to flakes of a few microns without the milling aids. Such size difference is quantified using two sizing technologies independently and is verified by the study of the hydrodynamic performance at three flow conditions that are of practical interest for the environmental applications of ZVI. Mechanism of the FeSx as milling aids for the pulverization enhancement may relate to its wedge effects, its non-ductile texture that inhibits the cold welding and its fine bead function. The study provides a method to improve the efficiency of the production of ultrafine iron particles for environmental applications and it is also the 1st work reporting the enhancement of the pulverization of ductile ZVI.

AlxGa1–xAs(100) (x ∼ 0.3) surfaces treated with aqueous sodium sulfide solution: Chemistry and electronic structure

Chemical composition and electronic structure of the native-oxide-covered AlxGa1–xAs(100) (x ∼ 0.3) surfaces were investigated by x-ray photoelectron spectroscopy and photoluminescence before and after treatment at room temperature with a concentrated aqueous solution of sodium sulfide in order to get inside into mechanism of sulfide solution interaction with aluminum-containing III–V alloys. Even short treatment of the n-AlGaAs(100) surface leads to the removal of the most of the native oxide layer so that the surface is covered with a thin layer of residual aluminum and gallium oxides with a thickness of approximately 1 ML, which can be formed during air exposure after termination of the chemical treatment. Longer treatment of the n-AlGaAs(100) surface does not further reduce the amount of residual aluminum and gallium oxides. The etching of native oxide layer on the p-AlGaAs(100) surface proceeds slower and the lowest amount of residual aluminum and gallium oxides is achieved after etching for 12 min. At the same time sulfur is hardly adsorbed at the AlGaAs(100) surfaces after interaction with the solution. It is found that the lower the amount of residual aluminum and gallium oxides on n- and p-AlGaAs(100) surfaces, the higher is the photoluminescence intensity. The band bending on the native-oxide-covered n- and p-AlGaAs(100) surfaces is about 0.85 and 0.5 eV, respectively, while the ionization energy is nearly the same for both surfaces. Treatment of n- and p-AlGaAs(100) surfaces with an aqueous sodium sulfide solution causes simultaneous decrease in their ionization energy.

Effective Utilization of Sulfur Wastewater by Photocatalytic System Using B/CuO/ZnO

B-doped zinc oxide/copper oxide composites prepared using a simple method showed high photocatalytic hydrogen production activity in the presence of aqueous sulfide solutions. Co-modification of the CuO composite with B-doping caused an increase in the charge separation efficiency and light absorption capacity. The sacrificial effect was thermodynamically enhanced by manipulating the composition of the sulfide solution. A maximum hydrogen production activity of 224 μmol g−1 h−1 was achieved under 450 nm light irradiation in a photocatalytic system with optimized B doping, a CuO composite, and a sulfide sacrificial agent concentration.

Interface-coupled PbSO4 dissolution and PbS precipitation and its effect on sulfidization flotation of anglesite

Anglesite sulfidization mechanism was systematically investigated using flotation tests, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and ultraviolet− visible diffuse reflectance spectroscopy (UV−Vis DRS). The activation effect of sodium sulfide on anglesite flotation was demonstrated by the flotation tests; however, sodium sulfide concentration must be properly controlled to avoid excessive sulfide ions causing flotation depression. The results of XPS, Raman, and UV−Vis DRS revealed that PbSO4 was replaced by PbS during anglesite treatment with a sodium sulfide aqueous solution. FESEM imaging shows the dissolution of PbSO4 and the precipitation of PbS nanoparticles during sulfidization. Thus, it can be suggested that the reaction of anglesite with a sodium sulfide aqueous solutionproceeds via an interface-coupled dissolution–precipitation mechanism: upon contact with a sodium sulfide aqueous solution, anglesite dissolution releases Pb2+ and SO42– into the fluid boundary layer, which becomes oversaturated with respect to PbS phase; then the PbS nanoparticles nucleate and grow on the surface of anglesite. The PbS nanoparticles grown on anglesite can improve the floatability of anglesite.

Improving the Sulfurophobicity of the NiS-Doping CoS Electrocatalyst Boosts the Low-Energy-Consumption Sulfide Oxidation Reaction Process.

Producing sulfur from a sulfide oxidation reaction (SOR)-based technique using sulfide aqueous solution has attracted considerable attention due to its ecofriendliness. This study demonstrates that NiS-doped cobalt sulfide NiS-CoS-supported NiCo alloy foam can deliver the SOR with superior electrocatalytic activity and robust stability compared to reported non-noble metal-based catalysts. Only 0.34 V vs RHE is required to drive a current density of 100 mA cm-2 for the SOR. According to the experiment, the catalyst exhibits a unique sulfurophobicity feature because of the weak interaction between sulfur and the transition metal sulfide (low affinity for elemental sulfur), preventing electrode corrosion during the SOR process. More impressively, the chain-growth mechanism of the SOR from short- to long-chain polysulfides was revealed by combining electrochemical and spectroscopic in situ methods, such as in situ ultraviolet-visible and Raman. It is also demonstrated that electrons can transfer straight from the sulfion (S2-) to the active site on the anode surface during the low-energy-consumption SOR process. This work provides new insight into simultaneous energy-saving hydrogen production and high-value-added S recovery from sulfide-containing wastewater.

Hydrothermal Synthesis of Silver Sulfide

Silver sulfide powders with submicro- and micrometer particle sizes have been synthesized by the hydrothermal method at temperatures from 373 to 453 K in aqueous and alcoholic solutions of silver nitrate, sodium sulfide and citrate, sulfur, and thiocarbamide. The crystal structures of the synthesized powders, morphology, composition, and particle size of silver sulfide have been analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and gas adsorption. The powder particles have a similar morphology in the form of rectangular parallelepipeds and cubes with smoothed edges; the size of the powder particles depends on the synthesis conditions and ranges from ~500 to 2000 nm.

Thermal Stability of Nanocrystalline Zinc Sulfide ZnS

Nanocrystalline zinc sulfide (ZnS) powders are prepared via hydrothermal deposition from aqueous solutions of zinc nitrate and sodium sulfide in the presence of sodium citrate or Trilon B. The average particle sizes of the product ZnS nanopowders ranging from 2 to 9 nm are tuned via varying the batch concentrations of the reagents. Air-annealing of as-prepared ZnS nanopowders at temperatures of 280 to 530°C oxidizes cubic zinc sulfide to hexagonal zinc oxide. The oxidation of the finest-grained zinc sulfide nanopowders having a particle size of 2 nm starts at 280–330°C, while the coarsest-grained nanopowder having a particle size of 9 nm starts to oxidize at 530°C. In the coarsest-grained ZnS powder, the particle size increases as little as from 9 to 12 nm when temperature rises to 530°C, while the finest-grained nanopowders have their particle sizes increase from 2 to 9 nm in response to the same rise in temperature.

Stability of Colloidal Silver Sulfide Solutions

Stable colloidal solutions of silver sulfide Ag2S quantum dots of various sizes were prepared by hydrochemical bath deposition from low-concentration aqueous solutions of silver nitrate, sodium sulfide, and sodium citrate. The Ag2S quantum dot sizes determined by dynamic light scattering (DLS) were 2–3 to 28–30 nm. The great negative values of the measured ζ-potentials of the colloidal solutions and the small changes in ζ-potential and quantum dot sizes upon the long-term storage of the solutions indicate their stability across time.

Chemical modification of the GaP(0 0 1) surface electric field with sulfide solutions

The surface electric field in GaP(001) passivated with aqueous and alcoholic sulfide solutions is studied by reflectance anisotropy spectroscopy using data on the surface chemical and electronic structure obtained by synchrotron-radiation X-ray photoelectron spectroscopy. Treatment of n-GaP(001) surface with a sulfide solution decreases the surface electric field depending on sulfide solution composition. In particular, passivation with the solution of ammonium sulfide in 2-propyl alcohol turns the total surface electric field almost to zero, while passivation with the aqueous ammonium sulfide solution reduces the surface electric field in a lesser extent. On the other hand, sulfide treatment of p-GaP(001) surface enhances the surface electric field dramatically and this enhancement is nearly independent of the sulfide solution composition. Such changes in the surface electric field can be related to the modification of the dipole associated with chemical bonds in the passivating layer.

Synthesis of Zinc Sulfide Nanoparticles Using Pyridinium Ionic Liquids

Zinc sulfide nanoparticles (quantum dots) were synthesized from aqueous solutions of sodium sulfide and zinc sulfate using pyridinium ionic liquids. The average sizes of zinc sulfide nanoparticles were determined by UV spectroscopy, X-ray diffraction, probe and scanning electron microscopy. The influence of the structure and concentration of pyridinium ionic liquids with the tetrafluoroborate anion of the same name on the size of zinc sulfide nanoparticles has been studied. The effect of the precursor concentration on the size of the nanoparticles formed in the ash was established.

Sulfur Loading as a Manufacturing Key Factor of Additive-Free Cathodes for Lithium-Sulfur Batteries Prepared by Composite Electroforming

The promised prospects of Li–S technology, especially within the energy situation of the 21st century, have sparked a renewed interest from the scientific community in the 2000s. In this context, we present our new vision for the fabrication of novel cathodes for Li–S batteries that were synthesized using the first combination of composite plating and electroforming (composite electroforming). The latter consists of electroforming the current collector foil directly in a one-step process. Simultaneously, the active material is introduced into the metal matrix by means of composite plating. Reduced technological steps, better performance and resource-saving production, combined with a potentially easier and highly efficient way of recycling electrodes, are achievements of the current method. In the present work, novel cathodes for lithium–sulfur batteries were synthesized by composite electroforming of AlSi10Mg0.4@Ni foil from a nickel sulfamate-based electrolyte with AlSi10Mg0.4 particles used as dispersoids. The composite foil is subsequently etched in order to increase the specific surface area of the aluminum alloy particles. The last manufacturing and key step of the ready-to-use cathodes for Li–S batteries is the sulfur loading, which was conducted using two different ways: by spin coating in melted sulfur at 160 °C or electrochemically from a sodium sulfide aqueous solution (Na2S(aq)). Morphological and electrochemical characterization by SEM and galvanostatic cycling, respectively, exhibited a remarkable difference in terms of the sulfur distribution and the surface morphology as well as a considerable improvement of the rate capability and cyclability for the electrochemically loaded cathode as against the spin-coated one.

Continuous Flow Synthesis of Cd1-x Znx S and CdS/ZnS Core/Shell Semiconductor Nanoparticles by MicroJet Reactor Technology.

From aqueous precursor solutions of metal salts and sodium sulfide using MicroJet Reactor (MJR) technology Cd1-x Znx S and CdS/ZnS core/shell semiconductor nanoparticles were synthesized. The MJR approach represents an automated, continuous, flexible and scalable route for nanoparticle synthesis, providing a tight control over process parameters and thus simple size, shape and composition control. Since particle sizes below the excitonic Bohr radius were obtained by MJR, the nanoparticulate materials exhibit quantum confinement effects. By varying the precursor ratio the band gap of Cd1-x Znx S Quantum Dots (QDs) could be targeted from 3.1 to 3.6 eV. CdS/ZnS core/shell QDs were prepared by enclosing CdS particles from MJR with ZnS produced by thermal decomposition of a Zn-MPA complex. Adjustment of the shell thickness increased the photoluminescence intensity by 43 %. Synthesis of ternary sulfides in the form of core/shell particles broadens the spectrum of materials accessible by MJR and demonstrates the extraordinary flexibility of the technology.

Localized Environment Enriched with Hydrogen Sulfide for Inducing Sulfide Stress Cracking on Type-430 Stainless Steel

Exposure tests to hydrogen sulfide environments are frequently used to evaluate hydrogen sulfide stress corrosion cracking (SSC) in steel. However, there are many safety restrictions in handling hydrogen sulfide, and the maintenance of the facilities is very costly. To improve this situation, an electrochemical measurement method that can be used even in laboratories to simulate hydrogen sulfide stress corrosion tests easily. Specifically, a safe hydrogen sulfide corrosion test method was developed using a local hydrogen sulfide concentration environment near the steel surface.A local acidic environment of pH 3-4 was induced by constant potential anodic polarization of a platinum electrode below 2 VSHE in an aqueous sodium sulfide solution. Exposure of the carbon steel surface to a local acidic environment resulted in the formation of iron sulfides such as FeS and FeS2 on the surface, accompanied by a negative shift of the carbon steel electrode potential and an increase in the microelectrode current. Local acidification of a potentiostatically polarized type-430 steel surface confirmed the existence of a critical potential at which the steel surface begins to depassivate and actively dissolve. It was suggested that the substitution of iron oxide for iron sulfide in a hydrogen sulfide environment determines the sulfidation of the steel surface. Using this method, furthermore, the formation of cracks was successfully induced on the surface of type-430 steel under tensile stress loading.

The Effect of Different Preoperative Depilation Ways on the Healing of Wounded Skin in Mice.

Simple SummaryAn increasing number of animals, including pets, may undergo surgery due to diseases or cesarean section nowadays. To reduce surgical site infection, hair removal is a necessary step before the surgical procedure because of the dense hair layer on the skin. However, previous studies showed that inappropriate hair removal methods might even increase surgical site infection rates. Although there are many commonly used preoperative depilation methods, it still has no detailed, unified selection criteria for animal preoperative hair removal. Therefore, we intend to provide a scientific and practical reference for veterinarians. To explore more specific details on whether depilation affects the condition of a surgical site, we established a skin wound model after the depilation step and then compared four commonly used hair-removal methods through morphological assessment and histopathological analysis. Ultimately, we concluded that the electric shaving method is the best method for preoperative depilation, followed by the depilatory cream method, and the sodium sulfide aqueous solution depilation method is the worst. We hope that the results of this study can provide useful reference points for veterinarians and researchers and help refine surgical procedures and maintain animal welfare.Hair removal is necessary before operating on animals with dense hair layers. To provide an appropriate hair removal method and maintain animal welfare, we introduced four commonly used depilation methods—namely, scissors shearing, electric shaving, depilatory cream, and sodium sulfide, and made systematic comparisons, instead of only examining one or two methods, as reported in the past. To further assess convenience and possible effects on skin wound healing, we performed a skin trauma model after depilation in C57BL/6J mice and recorded wound healing time. Meanwhile, the skin tissues around the wound were stained with H&E and Masson. The results showed that the wound contraction rate of the sodium sulfide group was significantly lower than other groups at different points in time. Furthermore, depilatory cream and sodium sulfide methods could induce a topical inflammatory response on the third day after the operation and delay the regeneration of collagen fibers. We concluded that sodium sulfide depilatory has a significant negative effect on wound healing. Depilatory cream is gentler, with mild skin irritation and symptoms of inflammation. The electric shaving method is more convenient and safer, and thus could be the best choice for preoperative depilation.

Impact of GaAs(100) surface preparation on EQE of AZO/Al2O3/p-GaAs photovoltaic structures.

In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

Synthesis and Characterization of (Ag2S)x(ZnS) Heteronanostructures

(Ag2S)x(ZnS) heteronanostructures were synthesized by two-stage chemical codeposition of silver and zinc sulfides using aqueous solutions of zinc nitrate, silver nitrate, sodium sulfide, trisodium citrate and Trilon B. Prepared heteronanostructures were characterized for phase composition and nanoparticles size using X-ray diffraction and the high-resolution transmission electron microscopy. The size of Ag2S nanoparticles in the obtained heteronanostructures depends on the ratios of reagent concentrations and ranges from 9 to 30 nm, the size of ZnS nanoparticles is equal to 4-5 nm.

The solubility of cooperite PtS(cr) at 25 – 450 °C, Psat – 1000 bar and hydrosulfide complexing of platinum in hydrothermal fluids

The solubility of cooperite PtS(cr) was measured in aqueous sulfide solutions at 25 °C/1 bar, 75 °C/1 bar, and 450 °C/1000 bar. The concentration of Pt increases with an increase of temperature from 10–10.2 to 10–7.4m (mol⋅(kg H2O)−1) in solutions which contain 0.06–0.07 m of total reduced sulfur. The experimental solubility data are accurately described by the reactionsPtScr+H2S˚aq=PtHS2˚aqKs˚PtHS2.PtScr+2H2S˚aq=PtHS3−+H+Ks˚PtHS3−..The charged complex Pt(HS)3− dominates in low-temperature near-neutral solutions but was not detected at 450 °C where the only hydrosulfide complex was Pt(HS)2°(aq). The effect of NaCl on the PtS(cr) solubility is negligible which implies that mixed Pt-HS-Cl complexes can be neglected. The PtS(cr) solubility constant, Ks°(Pt(HS)2), was determined as log Ks° = −9.09 ± 0.17 (25 °C/1 bar), −9.50 ± 0.35 (75 °C/1 bar), and − 6.68 ± 0.10 (450 °C/1000 bar). The PtS(cr) solubility constant, Ks°(Pt(HS)3−), was determined as log Ks° = −14.43 ± 0.31 (25 °C/1 bar), and − 13.15 ± 0.23 (75 °C/1 bar). The PtS(cr) solubility constants together with the literature data were fitted to a simple density modellogKSoPtHS2o=−7.30−638.9∙TK−1−5.98∙logdwlogKSoPtHS3−=0.633−4522.6∙TK−1+43.03∙logdwwhere d(w) is the pure water density. The Ks°(Pt(HS)2) increases with an increase of temperature, but Ks°(Pt(HS)3−) has a maximum at ca. 200 °C. Accordingly, at higher temperatures the role of the latter complex decreases and its contribution to the dissolved Pt concentration becomes negligible at t > 300 °C. Thermodynamic calculations show that in natural hydrothermal fluids, which contain up to 0.1 m of total reduced sulfur, the concentration of Pt-HS complexes can reach a few ppb. Higher solubility of Pt-bearing minerals can be attained in chloride-bearing fluids due to the formation of PtCl42−, which plays the dominant role in high-temperature hydrothermal transport of Pt.

ZnS Nanopowders and ZnS/Ag2S Heteronanostructures: Synthesis and Properties

Zinc sulfide ZnS nanopowders were prepared by chemical deposition from aqueous solutions of zinc nitrate and sodium sulfide in the presence of sodium citrate or Trilon B. ZnS/Ag2S heteronanostructures were prepared by two-step chemical codeposition of zinc and silver sulfides. The prepared ZnS nanopowders had average particle sizes ranging from 2 to 10 nm depending on the reagent concentration ratio in the batch. The nanoparticle sizes in the thus-prepared heteronanostructures were 8–10 nm. The diffuse reflectance spectra of nanostructured ZnS and ZnS/Ag2S heteronanostructures were measured. The bandgap width Eg in the studied sulfide nanostructures was assessed based on an examination of the measured optical absorption spectra. As the nanoparticle size decreased from 10 to 2 nm, the Eg in ZnS nanopowders increased in the range 3.59–3.72 eV. The increasing Ag2S percentage in ZnS/Ag2S heteronanostructures leads to narrowing of the bandgap. Pulsed cathodoluminescence (PCL) spectra were recorded. The luminescence characteristics of ZnS and ZnS/Ag2S depend on the preparation method and nanoparticle morphology.

InP(1 0 0) surface passivation with aqueous sodium sulfide solution

Passivation of n-InP(100) surface with an aqueous sodium sulfide solution was investigated by photoluminescence and x-ray photoelectron spectroscopy techniques. It was found that even a brief treatment for 1 min turns out to be enough for an essential enhancement of the photoluminescence intensity, which comes amid etching off the surface indium phosphate layer and formation of In–S and In–OH surface chemical bonds. A longer sulfide treatment results in a smaller photoluminescence enhancement due to formation of indium oxide, in addition to In–S and In–OH bonds. Both native-oxide-covered and sulfide-treated n-InP(100) surfaces have almost no band bending. The enhancement of photoluminescence intensity after sulfide treatment can be explained by modification of the surface states spectrum due to the transformation of the surface chemical bonds.

Solution processed Cu2S/TiO2 heterojunction for visible-near infrared photodetector

A new method has been developed to grow copper (I) sulfide (Cu2S) nanoparticle (NP) inside a titanium dioxide (TiO2) thin film. This Cu2S NP growth process consists of two successive steps: ion-exchange and sulfurization process. In the beginning, Li4Ti5O12 thin film has been fabricated by a sol-gel process that contains mobile lithium-ion (Li+). This ion-conducting Li4Ti5O12 thin film has been deposited by spin coating and subsequent annealing method. In the following step, Li+ has been exchanged with Cu+ by the ion-exchange method that has been converted to Cu2S by subsequent sulfurization process. The ion-exchange has been done by immersing this Li4Ti5O12 thin film into a copper (I) chloride (CuCl) solution, whereas sulfurization has been done by dipping the Cu+ contain thin film within aqueous sodium sulfide (Na2S) solution. This process allows us to fabricate smooth and large area TiO2 thin film containing Cu2S NPs with an average particles of ∼10.5 nm. A lateral heterojunction photodetector has been fabricated based on this Cu2S-TiO2 thin film that shows a very good photoresponse in the visible-near infrared region with a highest detectivity of 1.7 × 1011jones at 830 nm.