Showing papers on "Sodium sulfide published in 2020"

Efficient Hydrogen Generation from the NaBH4 Hydrolysis by Cobalt-Based Catalysts: Positive Roles of Sulfur-Containing Salts

Abstract: Development of a simple and efficient strategy for improving the catalytic activity of cobalt-based catalysts toward hydrogen evolution from sodium borohydride (NaBH4) is paramount but remains challenging. Here, we reported a facile and efficient approach to tune the catalytic performance for NaBH4 hydrolysis with Co-based catalysts prepared by using cobalt sulfate as a precursor or a mixture of sulfur-containing sodium salts/cobalt salts as a raw material. With the use of cobalt sulfate as the precursor, the CoSO4-doped Co3O4 sample was formed and it exhibited excellent activity with the generation of ∼500 mL of hydrogen gas from NaBH4 hydrolysis under mild conditions. In terms of sulfur-free cobalt salts (e.g., cobalt chloride, cobalt nitrate, and cobalt acetate) as precursors, the obtained Co-based samples were found to be entirely ineffective for hydrogen production. Interestingly, during the cobalt-based catalyst preparation, the introduction of sodium sulfate or sodium sulfide can considerably accelerate hydrogen production. On the contrary, adding sulfur-bearing salts did not inspire any activity improvement only during the hydrogen generation reaction. Control experiments indicate that during catalyst preparation, the presence of Na2SO4 and Na2S is beneficial for the in situ transformation of Co3O4 into catalytically active Co-B alloys, accompanying a positive change in surface morphology during the NaBH4 hydrolysis, thereby inducing an excellent hydrogen generation rate of up to 4425 mL·min-1·gcat-1.

Nickel Hollow Spheres Concatenated by Nitrogen-Doped Carbon Fibers for Enhancing Electrochemical Kinetics of Sodium-Sulfur Batteries.

Abstract: The high energy density of room temperature (RT) sodium-sulfur batteries (Na-S) usually rely on the efficient conversion of polysulfide to sodium sulfide during discharging and sulfur recovery during charging, which is the rate-determining step in the electrochemical reaction process of Na-S batteries. In this work, a 3D network (Ni-NCFs) host composed by nitrogen-doped carbon fibers (NCFs) and Ni hollow spheres is synthesized by electrospinning. In this novel design, each Ni hollow unit not only can buffer the volume fluctuation of S during cycling, but also can improve the conductivity of the cathode along the carbon fibers. Meanwhile, the result reveals that a small amount of Ni is polarized during the sulfur-loading process forming a polar Ni-S bond. Furthermore, combining with the nitrogen-doped carbon fibers, the Ni-NCFs composite can effectively adsorb soluble polysulfide intermediate, which further facilitates the catalysis of the Ni unit for the redox of sodium polysulfide. In addition, the in situ Raman is employed to supervise the variation of polysulfide during the charging and discharging process. As expected, the freestanding S@Ni-NCFs cathode exhibits outstanding rate capability and excellent cycle performance.

Anticancer and Antibacterial Activity of Cadmium Sulfide Nanoparticles by Aspergillus niger

Abstract: Cadmium-tolerant (6 mM) Aspergillus niger (RCMB 002002) biomass was challenged with aqueous cadmium chloride (1 mM) followed by sodium sulfide (9 mM) at 37°C for 96 h under shaking conditions (200 rpm), resulting in the formation of highly stable polydispersed cadmium sulfide nanoparticles (CdSNPs). Scanning electron microscopy revealed the presence of spherical particles measuring approximately 5 nm. A light scattering detector (LSD) showed that 100% of the CSNPs measure from 2.7 to 7.5 nm. Structural analyses by both powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed the presence of cubic CdS nanoparticles (CdSNPs) capped with fungal proteins. These CdSNPs showed emission spectra with a broad fluorescence peak at 420 nm and UV absorption onset at 430 nm that shifted to 445 nm after three months of incubation. The CdSNPs showed antimicrobial activity against E. coli, Pseudomonas vulgaris, Staphylococcus aureus, and Bacillus subtilis, and no antimicrobial activity was detected against Candida albicans. The biosynthesized CdSNPs have cytotoxic activity, with 50% inhibitory concentrations (IC50) of 190 μg mL-1 against MCF7, 246 μg mL-1 against PC3, and 149 μg mL-1 against A549 cell lines.

Tailoring binder–cathode interactions for long-life room-temperature sodium–sulfur batteries

Abstract: Room-temperature sodium–sulfur batteries (NaSBs) are well poised as candidates for next-generation battery applications. However, two important limitations must first be overcome: irreversible capacity loss from long-chain polysulfide dissolution and cathode pulverization from severe volume expansion. Although covalent-sulfur composites like sulfurized polyacrylonitrile (S-PAN) prevent polysulfide dissolution, they do not address the latter issue of sustaining the cathode structure during the sodiation reaction. In this work, we demonstrate that the unique interactions between polar binders and insoluble short-chain sulfur species can be exploited as a strategy to solve both challenges concurrently. Our hypothesis is that specific polar groups, like the carboxyl moiety, interact strongly with sodium sulfide and short-chain polysulfides, as compared to traditional fluoropolymer binders employed in most sulfur-based cathodes. Binder–cathode interactions were first predicted for sodium–sulfur batteries using theoretical calculations, and then confirmed experimentally using a polyacrylic acid (PAA) binder, in combination with a S-PAN cathode. This strategy can be further generalized to other carboxyl binder systems, as demonstrated using two additional binders derived from natural products. Compared to conventional polyvinylidene difluoride-based cathodes experiencing large initial capacity losses, the PAA-based S-PAN cathode delivered a long 1000 cycle lifetime with initial and final discharge capacities of 1195 and 1000 mA h g(S)−1 respectively, representing a low capacity loss of 0.016% per cycle. Rational design of NaSBs based on the synergistic interactions between insoluble sulfur species and carboxyl-binders allows us to overcome key challenges to their practical development.

Core-Shell Fe/FeS Nanoparticles with Controlled Shell Thickness for Enhanced Trichloroethylene Removal.

Abstract: Zero-valent iron nanoparticles (nZVI) treated by reduced sulfur compounds (i.e., sulfidated nZVI, S-nZVI) have attracted increased attention as promising materials for environmental remediation. While the preparation of S-nZVI and its reactions with various groundwater contaminants such as trichloroethylene (TCE) were already a subject of several studies, nanoparticle synthesis procedures investigated so far were suited mainly for laboratory-scale preparation with only a limited possibility of easy and cost-effective large-scale production and FeS shell property control. This study presents a novel approach for synthesizing S-nZVI using commercially available nZVI particles that are treated with sodium sulfide in a concentrated slurry. This leads to S-nZVI particles that do not contain hazardous boron residues and can be easily prepared off-site. The resulting S-nZVI exhibits a core-shell structure where zero-valent iron is the dominant phase in the core, while the shell contains mostly amorphous iron sulfides. The average FeS shell thickness can be controlled by the applied sulfide concentration. Up to a 12-fold increase in the TCE removal and a 7-fold increase in the electron efficiency were observed upon amending nZVI with sulfide. Although the FeS shell thickness correlated with surface-area-normalized TCE removal rates, sulfidation negatively impacted the particle surface area, resulting in an optimal FeS shell thickness of approximately 7.3 nm. This corresponded to a particle S/Fe mass ratio of 0.0195. At all sulfide doses, the TCE degradation products were only fully dechlorinated hydrocarbons. Moreover, a nearly 100% chlorine balance was found at the end of the experiments, further confirming complete TCE degradation and the absence of chlorinated transformation products. The newly synthesized S-nZVI particles thus represent a promising remedial agent applicable at sites contaminated with TCE.

New insights into the reagent-removal mechanism of sodium sulfide in chalcopyrite and galena bulk flotation: a combined experimental and computational study

Abstract: To remove the adsorbed reagent of copper–lead mixed concentrate in bulk flotation, this study investigates the removal effect of sodium sulfide (SS) through micro-flotation, adsorption tests, equilibrium speciation analysis, electrochemical analysis, and first-principle density functional theory (DFT) calculations. Micro-flotation tests demonstrate that chalcopyrite and galena recovery remarkably decline by 50% and 70%, respectively, because of SS addition in a mineral–butyl xanthate (BX) flotation system. Meanwhile, adsorption tests reveal that with the addition of SS, the adsorption density of BX onto the surfaces of chalcopyrite and galena decrease to 0.0008 and 0.001 mg/g, respectively. These findings indicate that BX on the mineral surface almost completely desorbs. Electrochemical tests further show that in the BX–mineral system, combined with the oxidation peak, BX and mineral react to form CuX2/PbX2. After adding sodium sulfide, the above peak does not appear, indicating that BX does not react with minerals because of the effect of SS. The first-principle calculations based on the DFT further reveals the competitive adsorption mechanism between SS and BX on chalcopyrite (001) and galena (100) surface, thereby demonstrating the significant performance of SS as a removing reagent.

Adsorption and desorption of butyl xanthate on chalcopyrite

Abstract: Reagent removal is an indispensable step to further separation of the copper sulfide ore flotation mixed concentrate, and xanthate is one of the most commercially used collectors for chalcopyrite flotation. In this work, the adsorption/desorption quantity of butyl xanthate was measured by the spectrophotometric method. Three adsorption models of Langmuir, Freundlich, and Temkin were used to fit the xanthate adsorption quantity dates. The results show that the adsorptions of sodium butyl xanthate on chalcopyrite match the Langmuir model best in the experimental conditions. Sodium sulfide dosage, pH value, ultrasonic wave, and temperature all show effects on butyl xanthate desorption. Butyl xanthate desorption can promote by increasing the dosage of sodium sulfide, ultrasonic wave intensity, temperature, and acidity or alkalinity of pulp. The order of the effectiveness of four conditions is sodium sulfide dosage, temperature, pH, and ultrasonic.

Operation performance and microbial community of sulfur-based autotrophic denitrification sludge with different sulfur sources

Abstract: Operation performance and bacterial community structure of sulfur-based autotrophic denitrification (SAD) based on different sulfur sources served as electron donor was first parallelly compared among three sequencing batch reactors. Sulfur and sodium thiosulfate systems achieved similar operation performance and were superior to that of sodium sulfide. When the influent NO3−–N concentration ranged from 50 to 150 mg/L, the effluent NO3−–N concentrations of the sulfur and sodium thiosulfate systems were 0–5.99 mg/L and 0–4.52 mg/L, respectively, without NO2−–N accumulation. However, when the effluent concentration of NO3−–N in the sodium sulfide system was 0–10.38 mg/L, that of NO2−–N in the effluent was 0–39.85 mg/L. In addition, participation of sulfur sources presented obvious pressure on the bacterial community structure based on the high-throughput sequencing. Microbial diversity results indicated that sludge with elemental sulfur as electron donor had the richest microbial diversity, followed by sodium thiosulfate and sodium sulfide. Moreover, sludge with elemental sulfur and sodium thiosulfate as electron donor demonstrated more similar community structure compared with the sludge that denitrified with sodium sulfide according to the microbial similarity analysis. The 9.34%, 24.3% and 29.6% of sequences could be assigned to potential SAD organisms from sludge denitrifying with elemental sulfur, sodium thiosulfate and sodium sulfide, respectively. Furthermore, all sludge denitrifying with different sulfur sources showed an enrichment of separate core functional microorganisms. This study could provide an insight into improving the understanding of SAD in engineering applications.

Facile one-step synthesis of quaternary AgInZnS quantum dots and their applications for causing bioeffects and detecting Cu2+

Abstract: Water-soluble AgInZnS quantum dots (AIZS QDs) were synthesized with glutathione (GSH) as a stabilizer by a facile one-step method based on a hydrothermal reaction between the nitrate salts of the corresponding metals and sodium sulfide as a sulfide precursor at 110 °C. The optimal reaction conditions (temperature, time, pH, and the molar ratios of the precursors) were studied. According to the data from TEM, XPS, and XRD, AIZS QDs were characterized with excellent optical properties. The results showed that the aqueous-dispersible AIZS QDs were quasi-spherical and their average diameter was 3.51 nm. Furthermore, the cytotoxicity of AIZS QDs was investigated by microcalorimetry and microscopy techniques (confocal microscopy and TEM). The data revealed that AIZS QDs exhibited low toxicity, biocompatibility, and good water stability, due to which they could be used as a fluorescent probe for bioimaging and labeling. In addition, AIZS QDs could be used as a sensor to detect Cu2+ because the fluorescence of AIZS QDs was quenched by Cu2+.

Chemical and Structural Variety in Sodium Thioarsenate Glasses Studied by Neutron Diffraction and Supported by First-Principles Simulations

Abstract: Sodium-conducting sulfide glasses are promising materials for the next generation of solid-state batteries. Deep insight into the glass structure is required to ensure a functional design and tailoring of vitreous alloys for energy applications. Using pulsed neutron diffraction supported by first-principles molecular dynamics, we show a structural diversity of Na2S-As2S3 sodium thioarsenate glasses, consisting of long corner-sharing (CS) pyramidal chains CS-(AsSS2/2)k, small AspSq rings (p + q ≤ 11), mixed corner- and edge-sharing oligomers, edge-sharing (ES) dimers ES-As2S4, and isolated (ISO) pyramids ISO-AsS3, entirely or partially connected by sodium species. Polysulfide S-S bridges and structural units with homopolar As-As bonds complete the glass structure, which is basically different from structural motifs predicted by the equilibrium phase diagram. In contrast to superionic silver and sodium sulfide glasses, characterized by a significant population of isolated sulfur species Siso (0.20 < Siso/Stot < 0.28), that is, sulfur connected to only mobile cations M+ with a usual M/Siso stoichiometry of 2, poorly conducting Na2S-As2S3 alloys exhibit a modest Siso fraction of 6.2%.

Chemical Treatment of Highly Toxic Acid Mine Drainage at A Gold Mining Site in Southwestern Siberia, Russia

Abstract: The critical environmental situation in the region of southwestern Siberia (Komsomolsk settlement, Kemerovo region) is the result of the intentional displacement of mine tailings with high sulfide concentrations. During storage, ponds of acidic water with incredibly high arsenic (up to 4 g/L) and metals formed on the tailings. The application of chemical methods to treat these extremely toxic waters is implemented: milk of lime Ca(OH)2, sodium sulfide Na2S, and sodium hydroxide NaOH. Field experiments were carried out by sequential adding pre-weighed reagents to the solutions with control of the physicochemical parameters and element concentrations for each solution/reagent ratio. In the experiment with Ca(OH)2, the pH increased to neutral values most slowly, which is contrary to the results from the experiment with NaOH. When neutralizing solutions with NaOH, arsenic-containing phases are formed most actively, arsenate chalcophyllite Cu18Al2(AsO4)4(SO4)3(OH)24·36H2O, a hydrated iron arsenate scorodite, kaatialaite FeAs3O9·8H2O and Mg(H2AsO4)2. A common specificity of the neutralization processes is the rapid precipitation of Fe hydroxides and gypsum, then the reverse release of pollutants under alkaline conditions. The chemistry of the processes is described using thermodynamic modeling. The main species of arsenic in the solutions are iron-arsenate complexes; at the end of the experiments with Ca(OH)2, Na2S, and NaOH, the main species of arsenic is CaAsO4−, the most toxic acid H3AsO3 and AsO43−, respectively. It is recommended that full-scale experiments should use NaOH in the first stages and then Ca(OH)2 for the subsequent neutralization.

Leaching Kinetics of Antimony from Refractory Gold Ore in Alkaline Sodium Sulfide under Ultrasound

Abstract: The leaching kinetics of antimony from refractory gold ore in alkaline sodium sulfide was investigated under ultrasound. The influence of factors such as stirring speed, temperature, the concentration of sodium hydroxide and sodium sulfide and particle size, was studied. The leaching kinetics has also been studied under convention and ultrasound. The experimental data are consistent with the shrinkage core model and the leaching rate is controlled by surface chemical reaction for both ultrasonic and the conventional method. Ultrasound increases the leaching rate of antimony from 81.2% to 93.1%. It can be seen that the rate constant kr of ultrasonic method at various temperatures is larger than that of the conventional method. The ultrasound reduces the apparent activation energy from 48.39 kJ/mol to 33.88 kJ/mol and reduces the apparent response series of sodium sulfide concentration from1.3 to 1.1. Comparing with conventional method, the ultrasound can greatly improve the antimony leaching rate, accelerate the leaching process and lower temperature and the concentration of sodium hydroxide and sodium sulfide. These advantages of ultrasonic method were also confirmed by the SEM analysis of the leached solid.

Domino Synthetic Strategy for Tetrahydrothiopyran Derivatives from Benzaldehydes, 2-Acetylfuran/2-Acetylthiophene, and Sodium Sulfide.

Abstract: A novel domino reaction from benzaldehydes and 2-acetylfuran/2-acetylthiophene with sodium sulfide was developed to synthesize a series of tetrahydrothiopyran (THTP) derivatives. The reaction proce...

Poly(acrylamide-co-acrylic acid) gel polymer electrolyte incorporating with water-soluble sodium sulfide salt for quasi-solid-state quantum dot-sensitized solar cell:

Abstract: Rapid decay of photoanode, leakage from sealant, and evaporation of electrolyte are always the major concerns of quantum dot-sensitized solar cells (QDSCs) based on liquid electrolyte. Subsequently...

Study on dissolution and recovery of waste wool by sodium sulfide system

Abstract: In this research, keratin was extracted from the waste wool fiber using sodium sulfite as dissolving agent. The reaction results showed that the optimum conditions were as follows: the dosage of so...

Protease immobilized nanoparticles: a cleaner and sustainable approach to dehairing of skin

Abstract: Leather industry has been undergoing a paradigm shift from chemical to enzyme-based processes for removal of hair and opening up of fibers from skin prior to its conversion into leather. This involves the use of protease for hair removal and amylase for opening the fibers in the place of sodium sulfide and calcium hydroxide, respectively. The enzymes are currently applied through various methods such as the use of salt, kaolin, and sawdust. Additionally, the robustness of the enzymatic approach under various environmental conditions needs to be ensured to enhance its popularity. With a view to this, the possibility of utilizing enzyme immobilized on zinc oxide nanoparticles was explored. Enzyme immobilized nanoparticles (nano-biocatalyst) at a concentration of 1.0% was optimized for hair removal, and compared to conventional sodium sulfide method. The decrease in the time required for matching efficiencies has been observed with the use of nano-biocatalyst. Histopathology results confirmed that there is no distortion of fibers with the usage of nano-biocatalyst. The study demonstrates the potential use of enzyme immobilized nanoparticles in leather processing and could ideally turn out to be a sustainable approach on account of reduction in emission loads from the process.

ZnS Nanopowders and ZnS/Ag 2 S Heteronanostructures: Synthesis and Properties

Abstract: 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.

Synthesis and single-crystal structure of sodium sulfide cationic cluster in the sodalite cavity of zeolite Y (FAU, Si/Al = 1.56)

Abstract: The extraframework sodium sulfide cationic cluster, Na4S2+, has been introduced into zeolite Y (FAU, Si/Al = 1.56). A single crystal of |Na73(Na4S2+)1.0|[Si117Al75O384]-FAU was prepared by allowing aqueous 0.1 M Na2S solution to flow past a |Na75|[Si117Al75O384]-FAU crystal, and followed by vacuum dehydration at 723 K. Its structure was determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd $$\overline{3}$$ m. The structure was refined using all intensities to the final error index R1/wR2 = 0.044/0.125. About 77 Na+ ions per unit cell are found at the crystallographically distinct positions, six. One Na+ ion per unit cell is at the center of double 6-ring. Two site-I′ positions are occupied by 26.5 and 4 Na+ ions, respectively, per unit cell. Thirty-two Na+ ions per unit cell are found at site II, in the supercage opposite single 6-rings. The remaining 4.5 and 9 Na+ ions per unit cell occupy two sites III′ near triple 4-rings in the supercage. Finally, one sulfide ion per unit cell, associated with Na+ ions, is found at the center of sodalite cavity. The 4 Na+ ions at site I′ coordinate to a sulfide ion at the center of sodalite cavity to give tetrahedral cationic cluster, Na4S2+. In |Na73(Na4S2+)1.0|[Si117Al75O384]-FAU, tetrahedral Na4S2+ ions center about 12.5% of the sodalite cavities.