Showing papers on "Sodium sulfide published in 2002"

Synthesis and characterization of gold sulfide nanoparticles

Abstract: We report a new synthesis of colloidal gold(I) sulfide nanoparticles by reacting aqueous solutions of sodium sulfide and sodium gold sulfite. Optical absorption spectra and pH were measured during the reaction. The pH changes from 10.3 to 8.8 immediately after mixing the reactants and very slowly decreases during particle growth. The nanoparticles exhibit a continuous increase in absorption as the photon energy increases from 1 to 5 eV. The optical band gap of the nanoparticles has been estimated from the onset of absorption to be 1.8 ± 0.2 eV. X-ray photoelectron and energy-dispersive X-ray spectroscopy indicate that the composition of the particles is Au2S. The measured S(2p3/2) and Au(4f7/2) binding energies suggest that Au2S has mixed covalent/ionic bonding. Transmission electron microscopy shows that the particles are roughly spherical with an average diameter of 4 nm.

Use of Hydrochloric Acid for Determining Solid-Phase Arsenic Partitioning in Sulfidic Sediments

Abstract: We examined the use of room-temperature hydrochloric acid (1-6 M) and salt solutions of magnesium chloride, sodium carbonate, and sodium sulfide for the removal of arsenic from synthetic iron monosulfides and contaminated sediments containing acid-volatile sulfides (AVS). Results indicate that acid-soluble arsenic reacts with H2S released from AVS phases and precipitates at low pH as disordered orpiment or alacranite. Arsenic sulfide precipitation is consistent with geochemical modeling in that conditions during acid extraction are predicted to be oversaturated with respect to orpiment, realgar, or both. Binding of arsenic with sulfide at low pH is sufficiently strong that 6 M HCl will not keep spiked arsenic in the dissolved fraction. Over a wide range of AVS concentrations and molar [As]/[AVS] ratios, acid extraction of arsenic from sulfide-bearing sediments will give biased results that overestimate the stability or underestimate the bioavailability of sediment-bound arsenic. Alkaline solutions of sodium sulfide and sodium carbonate are efficient in removing arsenic from arsenic sulfides and mixed iron-arsenic sulfides because of the high solubility of arsenic at alkaline pH, the formation of stable arsenic complexes with sulfide or carbonate, or both.

Use of sulfide-containing liquors for removing mercury from flue gases

Abstract: A method and apparatus for reducing and removing mercury in industrial gases, such as a flue gas, produced by the combustion of fossil fuels, such as coal, adds sulfide ions to the flue gas as it passes through a scrubber. Ideally, the source of these sulfide ions may include at least one of: sulfidic waste water, kraft caustic liquor, kraft carbonate liquor, potassium sulfide, sodium sulfide, and thioacetamide. The sulfide ion source is introduced into the scrubbing liquor as an aqueous sulfide species. The scrubber may be either a wet or dry scrubber for flue gas desulfurization systems.

A reagentless renewable N,N′-diphenyl-p-phenylenediamine loaded sensor for hydrogen sulfide

Abstract: The electrochemically induced reaction of sodium sulfide with N,N′-diphenyl-p-phenylenediamine (DPPD) has been studied in aqueous solutions (pH 1–7) at glassy carbon (GC) electrodes. The DPPD indicator has been shown to form a thin film on the electrode surface capable of sensing sulfide at the triple phase boundary (DPPD/electrolyte/electrode) in the range 20–200 μM with a limit of detection of 18 μM. The low solubility of DPPD has been exploited further by incorporating the species in the design of a modified renewable carbon-epoxy electrode whereby the detection process can occur in an inexpensively constructed device suitable for single shot determinations.

Synthesis and characterization of metal sulfide clusters for toxicological studies.

Abstract: Zinc sulfide clusters were synthesized and characterized at low micromolar concentrations to assess the effect of metal-sulfide ligands on metal toxicity to aquatic organisms in oxic environments. Recommended preparation times are greater than 2 h initial reaction of equimolar sodium sulfide and zinc nitrate, followed by oxic aeration for 3 d. Ionic strength, pH, and anoxic stabilization time were found to be relatively unimportant in controlling the final yield. Adsorptive losses of zinc sulfide (ZnS) clusters to surfaces, however, were significant for a variety of vessel materials and membrane filters. Ionic strength and pH were found to be important factors controlling the extent of adsorptive losses with minimal loss for pHs greater than 9 and for soft waters. The Ag(I), Cu(II), and Hg(II) as metal sulfides completely suppress the analysis of sulfide, whereas Pb(II), Mn(II), and Co(II) partially suppress the analysis of sulfide by the methylene blue technique. Ultraviolet and fluorescence spectra are shown for synthesized ZnS clusters.

Photoreduction of bicarbonate catalyzed by supported cadmium sulfide

Abstract: Cadmium sulfide supported on silica (CdS-x/SiO2, x = 4, 11, 17, 25%) and zinc sulfide (CdS-x/ZnS, x = 5, 10, 20, 30%) was prepared by impregnation with cadmium sulfate and subsequent addition of sodium sulfide. The specific surface areas of the silica and zinc sulfide supported powders are in the range of 188–280 and 95–104 m2 g−1, respectively. After sonication of an aqueous suspension of CdS-17/SiO2 the particle size distribution exhibited two maxima at 22 and 57 µm. In the presence of sodium sulfite the supported cadmium sulfides photocatalyze the reduction of bicarbonate to formate, formaldehyde, and oxalate. Upon polychromatic irradiation (λ ≥ 290 nm) the C1-products formate and formaldehyde were obtained in concentrations of 30–130 µM whereas the C2-product oxalate reached only 1–8 µM. Formaldehyde is not formed through reduction of intermediate formate whereas oxalate is produced via oxidation of the latter. The linear increase of oxalate concentration with coverage can be rationalized by the assumption that dimerization of the intermediate carbon dioxide radical anion does not occur on the cadmium sulfide but in solution or on the silica surface. For zinc sulfide supported samples the coverages of 10, 20, and 30% do not change the photocatalytic activity significantly whereas a loading of 5% induces a 40-fold and 16-fold increase as compared to unmodified cadmium and zinc sulfide, respectively. This strong enhancement suggests that in CdS-05/ZnS the efficiency of charge separation is strongly improved through interparticle electron transfer. The results demonstrate that both silica and zinc sulfide supports increase the photocatalytic activity of cadmium sulfide through the presence of a recently found electronic semiconductor-support interaction (SEMSI effect). Additionally, the low coverage sample CdS-05/ZnS combines this novel effect with the higher charge separation efficiency of a coupled semiconductor system.

Carbon Tetrachloride Reduction by Fe 2¿ ,S 2¿ , and FeS with vitamin B 12 as Organic Amendment

Abstract: The reductive dechlorination of carbon tetrachloride ~CT! was examined in the presence of free iron ions (Fe 21 ), sulfide ions (S 22 ), and freshly precipitated ferrous sulfide ~FeS! as reducing agents, and vitamin B12 as organic amendment. The reductive dechlori- nation of CT by the reducing ions Fe 21 and S 22 in homogeneous phase resulted in the formation of variable amounts of the mono- and di-dechlorination products chloroform ~CF! and dichloromethane ~DCM!. In the ferrous chloride (FeCl2) solutions ~200 mM! where Fe 21 was the only electron source, 76% of the original CT was depleted within 1/2 h and about 28% and 8% went to CF and DCM, respectively, at a pH of 3.1 and with no buffer present. These same dechlorination products were observed in unbuffered sodium sulfide (Na2S) solutions ~110 and 200 mM! with S 22 as the electron source at pH 13.4. Dechlorination products were also observed in heterogeneous systems where FeS ~75-200 mM! acted as the bulk reductant and the addition of vitamin B12 ~0-4 mM! resulted in an enhancement of the dechlorination reaction. When 4 mM of vitamin B12 were added to 200 mM FeS, CT was removed continuously and the amount of CF and DCM formed increased significantly over time, yielding a mass recovery of 40% and higher afte r 1 h and a pseudofirst-order rate constant of 1.91 h 21 . The reductive dechlorination of CT in the absence of vitamin B12, resulted in a slower disappearance of CT and the formation of smaller amounts of CF and DCM accounting for only 1% of the mass loss in the 75 mM FeS suspensions to 15% in the 200 mM FeS suspensions after 2 h.

MoS2 textured films grown on glass substrates through sodium sulfide based compounds

Abstract: In this paper, we show that highly crystallized and (00l)-textured MoS2 thin films can be achieved on glass substrates with NaF additive. The thin films have a direct optical bandgap of 1.77 eV and a p-type electrical conductivity of σ4.5×10-2 S cm-1 at room temperature, which are near those of the MoS2 single crystals. These properties are required for the application of the MoS2 in thin film solar cells. The influence of the sodium on the crystallization and texturization process has been interpreted as due to the formation of an intermediate sodium thiomolybdate phase. The decomposition of this compound when T>723 K leads to the achievement of the MoS2 thin films having large crystallites oriented with their c axis perpendicular to the plane of the substrates. This process of texturization has then been generalized to the case of MX2 (M: Mo,W; X: S, Se) thin films with Ni and K additives. These results constitute a new step towards the achievement of efficient MoS2 based solar cells.

Essentially insoluble heavy metal sulfide slurry for wastewater treatment

Abstract: A product and method for the removal of pollutant heavy metals from aqueous solutions which precludes the end user from storing, handling, feeding and controlling hazardous soluble sulfide materials. The product is a slurry which includes a mixture of a liquid medium and an essentially insoluble salt wherein the salt is the reaction product of heavy metal ions, preferably selected from Mn ++ ions, Fe ++ ions, and Fe +++ ions, and sulfide ions derived from soluble sulfide sources such as sodium sulfide, hydrogen sulfide, and sodium hydrosulfide. Addition of the subject slurry to a wastewater stream will effect the precipitation of heavy metals with lesser equilibrium sulfide ion concentrations than that of the essentially insoluble salt. Solids collected by this method may be returned to subsequent wastewater streams for additional removal of heavy metals by any excess heavy metal sulfide salt.

Multifractal Properties of Copper Sulfide Film Formed in Self-Organizing Chemical System

Abstract: The growth of fractal films of copper sulfide formed during the oxidation of ascorbic acid by aerial oxygen in the presence of a copper coordination compound and sodium sulfide has been studied. The process of growth of the film can be divided into three parts: 1) generation of CuS centers of growth; 2) growth of CuS according to the diffusion limitation of aggregation mechanism; and 3) in the final stage the structure of the film does not change. A method is developed to obtain films with uniform fractal dimensions, but different values of fractal divergence.

Chemical synthesis and characterization of Cu doped ZnS nano-powder

Abstract: In the past few years, II–VI compounds semiconductor nanocrystal have received much interest because their optical properties are different from the corresponding bulk crystals [1, 2]. Among II–VI compounds, ZnS is one of the most promising host materials for the production of commercial thin film phosphors for electroluminescent (EL) device application [3–7]. Since its absorption and emission lie in the ultraviolet regime, the studies of its small size particles did not evoke much interest until the 1980s. In 1994, Bhargava and Gallagher first synthesized ZnS semiconductor microcrystallites doped with Mn2+ ions; they found that the photoluminescence of Mn2+doped in ZnS nanoparticles had much higher quantum efficiency than bulk crystals [8]. Hereafter, the metal doped ZnS nanoparticles have received increasing interest. Recently, many methods have been developed in preparation of Cu doped ZnS nanopowder [9, 10]. In this paper, we report a new chemical synthesis method for preparation of Cu doped ZnS nanopowder as shown in Fig. 1. This process concluded two steps: First, selection to synthesize different lengths of the zinc methacrylate polymer by adjusting the molar ratio of mercaptoacetic acid to monomer of the methacrylic acid; second, the polymer reaction with sodium sulfide and cupric sulfate, giving the Cu doped ZnS nanopowder. During formation of the nanoparticles, the nanoparticles were capped by the methacrylic polymer, which passivated the surface atoms, eliminated the energy levels inside of gap, and increased the luminescence intensity. The size of nanoparticles can be well controlled from 1.8 nm to 3 nm by adjusting the molar ratio of mercaptoacetic acid to monomer of methacrylic acid. The production of Cu doped ZnS nanopowder was also characterized by TEM, XRD and PL. Methacrylic acid (99%) monomers were purified by distillation under reduced pressure prior to use. The cupric sulfate (99%), zinc acetate dihydrate (99%), sodium sulfide (99%), potassium persulfate (99.5%) and mercaptoacetic acid (HSCH2COOH) (85%) were used without further purification. All of the chemicals were purchased from Beijing chemical reagent corporation. To synthesize Cu doped ZnS nanopowder, 40 × 10−6 m3 of water, 0.03 mol of zinc acetate, and 5.5 × 10−6 m3 (6.49 × 10−4 molar) of methacrylic acid were added to a three-neck flask equipped with condenser, then heated and stirred. When the temperature increased about 60 ◦C, 40 × 10−6 m3 of 0.005 M potassium persulfate aqueous solution and 10−5 m3 of 0.032 M (3.2 × 10−6 molar) mercaptoacetic acid aqueous solution were added, respectively. The temperature was kept at 80 ◦C for 1 h. 20 × 10−6 m3 of 0.008 M CuSO4 aqueous solution was added into reactor vessel and stirred for 5 min. 40 × 10−6 m3 of 0.8 M sodium sulfide aqueous solution was dropped into the reactor at a constant rate. When the Na2S aqueous solution was complete, the reaction was continued for an additional 30 min at 80 ◦C. The powder was well separated from the solution by centrifuging, rinsed with methanol and dried in vacuum. The Cu doped ZnS nano-powder was obtained. The PL spectra of Cu doped ZnS nanopowder were recorded with a Hitachi F-4500 fluorescence spectrophotometer. The spectra were obtained by exciting the sample with 368 nm wavelength at room temperature. X-ray powder diffraction was performed on the Cu doped ZnS powder on a Rigaku RU-200B rotaflex diffractometer using Cu Kα λ = 0.15406 nm. TEM

Recycling kraft pulping chemicals: cyclic voltammetry of molten salt mixtures containing Na2CO3, Na2SO4, Na2S/Na2Sx and Na2O/Na2O2

Abstract: Cyclic voltammetry (CV) has been used to investigate molten salt mixtures in the temperature range of 820–840 °C between the initial and anticipated final compositions for the proposed electrolytic recausticizing process of inorganic pulping chemicals. A mixture simulating the initial conditions for the proposed process (sodium carbonate, sodium sulfide/polysulfide and sodium sulfate) exhibited carbonate oxidation and sulfate reduction at the limits of the potential window. Additional oxidation of sulfide to sulfur occurs at potentials inside the positive limit of the potential window with subsequent chemical reaction to form polysulfide. To simulate the final composition sodium oxide and peroxide were added to the mixtures; the resulting CVs had an additional oxidation peak attributed to oxide and peroxide oxidation. We conclude the electrolytic recycle process is feasible, producing sulfide and oxide from carbonate and sulfate of sodium in the molten state, yet separation is necessary between the anolyte and catholyte so the reduction products are not consumed by oxidation.

Effect of sulfide ions on the stress corrosion behaviour of Al-brass and Cu10Ni alloys in salt water

Abstract: The stress corrosion cracking (SCC) behavior of Al-brass and Cu10Ni alloys was investigated in 3.5% NaCl solution in absence and in presence of different concentrations of Na2S under open-circuit potentials using the constant slow strain rate technique. The results indicated that the Cu10Ni alloy is more susceptible to stress corrosion cracking than as-received Al-brass at strain rate of 3.5 × 10−6 s−1 in 3.5% NaCl in presence of high concentration of sulfide ions (1000 ppm). The sulfide ions (up to 500 ppm) has no effect on the stress corrosion cracking of the annealed Al-brass in 3.5% NaCl at two strain rates of 7.4 × 10−6 and 3.5 × 10−6 s−1. The results support film rupture for Al-brass and sulfide stress corrosion cracking assisted with pitting corrosion for Cu10Ni at slip steps as the operating mechanisms.

Synthesis and Characterization of 2,5-Bis(2-pyridyl)thiophene

Abstract: 2-[2-(Trimethylsilyl)ethynyl] pyridine ( 6 ) was prepared in 95% yield by reaction of 2-bromopyridine with trimethylsilylacetylene in triethylamine in the presence of bis(triphenylphosphine)Palladium(II) chloride and Copper(I) iodide. Desilylation of ( 6 ) by refluxing with sodium hydroxide in methanol (yield 95%) of 2-ethynylpyridine ( 5 ). Oxidative coupling of ( 5 ) in pyridine by oxygen in the presence of Copper(I) chloride gives 70% yield of 1,4-bis(2-pyridyl)1,3-butadiyne ( 4 ). Reaction of 4 with sodium sulfide affords 100% of 2,5-bis(2-pyridyl) thiophene ( 1 ).

Reduction of Recycled Barium Sulfate

Abstract: Barium sulfate, which is recycled according to a new flowsheet of sodium sulfide production, was reduced by various carbon-containing materials (oil and furnace coke and Zh-grade coal). The reduction process was studied in comparison with the reduction of natural barite concentrate.

Dechlorination treatment agent

Abstract: PROBLEM TO BE SOLVED: To obtain a dechlorination treatment agent for removing free chlorine in water, improved so as to treat a large amount of water in a short time without leaving the dechlorination treatment agent itself or a component originating from the dechlorination treatment agent in water after treatment. SOLUTION: This dechlorination treatment agent contains sulfur such as simple sulfur or a metal sulfide such as iron sulfide, copper sulfide or calcium sulfide as an effective component. A molded object of simple sulfur, a molded object of a metal sulfide obtained as a precipitate by adding water containing metal ions to water containing a sulfide such as hydrogen sulfide, a metal sulfide supported on an inorganic porous carrier obtained by supporting metal ions on the inorganic porous carrier and sulfatizing the metal ions with sodium sulfide or sodium hydrosulfide, or the like, are used. COPYRIGHT: (C)2003,JPO

Testing of Sulphide Loaded Activated Carbon for Uptake of HgII from Aqueous Solution

Abstract: Activated carbon was prepared from coconut shells by chemical treatment, which was followed by thermal activation. It was mixed with 0.5 % of a sodium sulfide solution for different time intervals and the sulfide loading was observed maximum after one hour of equilibration. The carbons with and without sulfide treatment were used for uptake of mercuric ions from wastewater and the sulfide-loaded carbon was found to be more effective. The equilibrium data for mercury adsorption obeyed a Freundlich-type isotherm. Quantitative desorption of mercury was achieved using alkaline solutions of sodium sulfide.

Selective oxidation of kraft cooking liquors

Abstract: Provided is a process for the preparation of polysulfides which comprises reaching sodium sulfide with oxygen in the presence of a transition metal oxide, preferably MnO2, and with the consuption rate of O2 being at least 1.5x10-4 moles/1/sec. The process of the present invention is preferably conducted in a self-recirculated reactor, which has been found to allow easy control of the O?2? consumption rate.

Recycling Kraft Pulping Chemicals with Molten Salt Electrolysis

Abstract: Molten salt mixtures containing sodium carbonate, sodium sulfide, and sodium sulfate have been electrolyzed to generate sodium oxide and sodium sulfide while removing carbon from the system in the form of gas and maintaining a sulfur balance in the melt. This investigation leads toward the development of an electrolysis-based recycle process for pulping chemicals. The molten salts are presently found in the chemical recovery process of kraft pulping. Electrolysis was performed in a divided melt/undivided atmosphere and divided melt/divided atmosphere to avoid consumption of the oxide and sulfide products. The anodic reaction was carbonate oxidation to carbon dioxide and oxygen while sullide oxidation to palysulfides occurred to a lesser extent at less positive potentials; sulfate oxidation was not observed to occur. The cathodic reaction was sulfate reduction to sulfide and oxide, the desired molten precursors for recycled pulping liquors.

Preparation and Structure of 3,4,8,9-Tetrachloro-2,5,7,10-tetrahydro[1,6]dithiecine

Abstract: The reaction of Z-1,4-dibromo-2,3-dichlorobut-2-ene (1) with sodium sulfide leads to 3,4,8,9-tetrachloro-2,5,7,10-tetrahydro[1,6]dithiecine (2) as the principal product, rather than the anticipated 3,4-dichloro-2,5-dihydrothiophene (3). Compound (2) was characterized spectroscopically and its structure determined by X-Ray crystallography.