Showing papers on "Sodium sulfide published in 2004"

Uranium immobilization by sulfate-reducing biofilms.

Abstract: Hexavalent uranium [U(VI)] was immobilized using biofilms of the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans G20. The biofilms were grown in flat-plate continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. U(VI)was continuously fed into the reactor for 32 weeks at a concentration of 126 microM. During this time, the soluble U(VI) was removed (between 88 and 96% of feed) from solution and immobilized in the biofilms. The dynamics of U immobilization in the sulfate-reducing biofilms were quantified by estimating: (1) microbial activity in the SRB biofilm, defined as the hydrogen sulfide (H2S) production rate and estimated from the H2S concentration profiles measured using microelectrodes across the biofilms; (2) concentration of dissolved U in the solution; and (3) the mass of U precipitated in the biofilm. Results suggest that U was immobilized in the biofilms as a result of two processes: (1) enzymatically and (2) chemically, by reacting with microbially generated H2S. Visual inspection showed that the dissolved sulfide species reacted with U(VI) to produce a black precipitate. Synchrotron-based U L3-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of U precipitated abiotically by sodium sulfide indicated that U(VI) had been reduced to U(IV). Selected-area electron diffraction pattern and crystallographic analysis of transmission electron microscope lattice-fringe images confirmed the structure of precipitated U as being that of uraninite.

Optical and catalytic properties of Ag2S nanoparticles

Abstract: Optical properties of polymer-stabilized aqueous colloids of silver sulfide were studied. Nature and energies of optical transitions responsible for the absorption of visible light by silver sulfide nanoparticles were determined. Catalytic properties of Ag 2 S nanoparticles in methylviologen reduction by sodium sulfide were examined. It was shown that this reaction is reversible, the equilibrium caused by a reverse reaction between the product of direct catalytic process – sulfur (polysulfide anions) and cation-radical of methylviologen. It was found that Ag 2 S nanoparticles can catalyze reduction of Ag + ions by various reductants, in particular, hydroquinone or sodium sulfite, with the formation of silver particles having characteristic plasmon absorption bands in the visible spectral domain. Effect of the conditions of Ag + catalytic reduction on the shape and intensity of plasmon resonance bands of metallic silver were studied, schematic mechanism of this reaction was proposed. It was shown that at the irradiation of solutions containing Ag 2 S nanoparticles, Ag + cations and a reducing agent with the light corresponding to the fundamental absorption band of nanoparticulate silver sulfide, the rate of Ag + catalytic reduction increased whereas kinetic features of catalytic reaction and characteristics of plasmon resonance absorption bands of silver nanoparticles changed. A mechanism of photochemical activation of the catalytic reduction of silver ions with the participation of Ag 2 S nanoparticles was proposed.

Dimethylthioarsenicals as Arsenic Metabolites and Their Chemical Preparations

Abstract: Two unidentified arsenic metabolites were detected in the liver of rats on a gel filtration column by HPLC inductively coupled argon plasma mass spectrometry after an injection of dimethylarsinic (DMA(V)), dimethylarsinous (DMA(III)), monomethylarsonic (MMA(V)), or monomethylarsonous (MMA(III)) acid. The same arsenicals were also produced in vitro by incubation of DMA(III) in the liver supernatant but not by DMA(V). The two arsenic metabolites eluted at the same retention times as those of the two arsenicals prepared by reaction of DMA(V) with either thiosulfate plus disulfite or hydrogen sulfide or sodium sulfide plus sulfuric acid. The faster and slower eluting products on a gel filtration column were assigned as dimethyldithioarsinic acid (dimethylarsinodithioic acid) (DMTA(V)) and dimethylthioarsinous acid (DMTA(III)) from mass spectrometric data at m/z = 170 and 138 by electrospray ionization mass spectrometry with negative and positive ion modes, respectively. They were prepared selectively by reacting DMA(V) with hydrogen sulfide or sodium sulfide plus sulfuric acid under different reaction conditions. DMA(III) but not DMA(V) was transformed to DMTA(III) and DMTA(V) in the presence of sodium sulfide in vitro, suggesting that DMA(V) is reduced to DMA(III) with hydrogen sulfide, thiolated to DMTA(III), and then further thiolated oxidatively to DMTA(V). Metabolically, it is assumed that DMA(III) is transformed to DMTA(III) in the presence of sulfide ions, and then, DMTA(III) is oxidatively thiolated to DMTA(V). As the chemical species produced by reduction with the Reay and Asher method are DMTA(III) and DMTA(V), and different from DMA(III), the studies carried out with DMA(III) with the Reay and Asher method have to be reexamined.

UV photochemical oxidation of aqueous sodium sulfide to produce hydrogen and sulfur

Abstract: Sodium sulfide solutions were illuminated with ultraviolet light (λ=253.7 nm) to produce hydrogen and disulfide ion in equimolar amounts. The quantum efficiency for hydrogen production was as high as 27% for a 0.5 M Na2S solution in a batch reactor. While light intensity and sulfide concentration had a pronounced effect on reaction rate, the photochemical process was found to be pH independent within the range 8.5–13.3. A mechanism involving adsorption of bisulfide ion on the inner sleeve of the photoreactor is postulated. Elemental sulfur could be recovered from the disulfide solution via purging with H2S and then filtering. The resulting filtrate was also photoactive, suggesting the possibility of a continuous closed cycle photochemical operation for H2S decomposition into its constituent elements.

Catalytic activity of CuS nanoparticles in hydrosulfide ions air oxidation

Abstract: Photophysical characteristics of colloidal CuS nanoparticles synthesized in various conditions and stabilized in aqueous solutions with sodium polyphosphate (SPP) were studied. A correlation between the band gap of CuS nanoparticles and their average diameter was established. Catalytic activity of colloidal CuS nanoparticles in sodium sulfide air oxidation in aqueous solutions at atmospheric pressure and room temperatures was established and thoroughly investigated. Kinetics of HS − oxidation and the nature of principal products of this reaction (thiosulfate and sulfate ions) were elucidated. A scheme for the mechanism of hydrosulfide ions catalytic oxidation was proposed. Accordingly to the scheme, HS − oxidation is a chain-radical reaction initiated on the surface of CuS nanoparticles and propagating further in the bulk of a solution.

Green chemistry methods in sulfur dyeing: application of various reducing D-sugars and analysis of the importance of optimum redox potential.

Abstract: The importance of sulfur dyeing of cellulosic fibers, particularly cotton, is realized economically throughout the dyeing industry. At the present time, dyeing with sulfur dyes requires the use of various auxiliaries, many of which have adverse effects on the environment. The most damaging of these is the reducing agent sodium sulfide, required to reduce the dye molecules to a water-soluble leuco form to enable adsorption and diffusion into the fiber. In this study, attempts have been made to replace the sodium sulfide used within the sulfur dyeing process with a variety of environmentally friendly reducing sugars. The redox potential of various hexose and pentose monosaccharides and reducing disaccharides was recorded and compared. Subsequently, cotton was dyed with the world's most important sulfur dye, C. I. Sulfur Black 1, using the reducing sugars under alkaline conditions, and compared to dyeings secured by employing commercial sulfide reducing agents. It was observed that reducing sugars gave comparable, and in many cases superior, color strength and wash fastness results, with respect to the commercial sulfide-based reducing agents, which still account for the vast majority of sulfur dyeing processes and that pose significant environmental concern. Employment of reducing sugars in sulfur dyeing could provide a sustainable, nontoxic, biodegradable, cost-effective alternative to sodium polysulfide and sodium hydrogen sulfide. Comparison of the redox potential of reducing sugars against the color strength of the dyeings secured demonstrated that there was an optimum redox potential of around -650 mV for maximum color strength achieved. The same redox potential also conferred the lowest color loss upon washing. These observations were attributed to reduction of the polymeric dye molecules to an optimum size for fiber affinity and diffusion into the fiber, but which would also confer maximum wash fastness upon oxidation.

Treatment of Pulp and Paper Mill Wastes

Abstract: Pulp and paper mills are a major source of industrial pollution worldwide. The pulping and bleaching steps generate most of the liquid, solid, and gaseous wastes (Table 1) [1]. Pulping is a process in which the raw material is treated mechanically or chemically to remove lignin in order to facilitate cellulose and hemicellulose fiber separation and to improve the papermaking properties of fibers. Bleaching is a multistage process to whiten and brighten the pulp through removal of residual lignin. Pulping and bleaching operations are energy intensive and typically consume huge volumes of fresh water and large quantities of chemicals such as sodium hydroxide, sodium carbonate, sodium sulfide, bisulfites, elemental chlorine or chlorine dioxide, calcium oxide, hydrochloric acid, and so on. A partial list of the various types of compounds found in spent liquors generated from pulping and bleaching steps is shown in Table 2 [2–4]. The effluents generated by the mills are associated with the following major problems:

Effect of sodium sulfide on Ni-containing carbon monoxide dehydrogenases.

Abstract: The structure of the active-site C-cluster in CO dehydrogenase from Carboxydothermus hydrogenoformans includes a μ2-sulfide ion bridged to the Ni and unique Fe, whereas the same cluster in enzymes from Rhodospirillum rubrum (CODHRr) and Moorella thermoacetica (CODHMt) lack this ion. This difference was investigated by exploring the effects of sodium sulfide on activity and spectral properties. Sulfide partially inhibited the CO oxidation activity of CODHRr and generated a lag prior to steady-state. CODHMt was inhibited similarly but without a lag. Adding sulfide to CODHMt in the Cred1 state caused the gav = 1.82 EPR signal to decline and new features to appear, including one with g = 1.95, 1.85 and (1.70 or 1.62). Removing sulfide caused the gav = 1.82 signal to reappear and activity to recover. Sulfide did not affect the gav = 1.86 signal from the Cred2 state. A model was developed in which sulfide binds reversibly to Cred1, inhibiting catalysis. Reducing this adduct causes sulfide to dissociate, Cred2 t...

Chemoselective reduction of azides with sodium sulfide hydrate under solvent free conditions

Abstract: Sodium sulfide hydrate has been employed for an efficient reduction of a variety of azides to the primary amines in good-to-excellent yields under solvent-free system and without perturbing many active functionalities such as ether, carbonyl, sulfonyl, and nitro.

Synthesis, characterization, and mechanism of polymerization of poly(but-2-ene sulfide)

Abstract: The effect of structurat factors on polymer forma- whereas the latter gives cyclic and linear products. Interesttion versus cyclization is reported. The reaction of sodium ingly, trans/cis isomerization takes place during the polymer sulfide with either 1,4-dibomobut-2-ene 1 or 1,4-dibromo- formation from 1 and a plausible mechanism has also been butane 2 has been carried out in presence of a phase transfer discussed. catalyst and it was observed that the former yields polymer. compound 2 is discused here.

Highly sensitive spectrophotometric reaction rate method for the determination of selenium based on the catalytic reduction of sulfonazo by sulfide

Abstract: A sensitive and rapid kinetic spectrophotometric method was developed for the determination of ultratrace amounts of selenium [Se (VI), Se (IV), and total selenium]. The method is based on the catalytic effect of Se (IV) on the reduction of sulfonazo by sodium sulfide. The reaction was followed spectrophotometrically by measuring the decrease in absorbance at 570 nm for the reaction mixture or by measuring the increase in absorbance of the reaction mixture at 680 nm and at 25°C, by the fixed‐time method. Selenium could quantitatively be determined in the range of 0.5–180 and 50–2300 ng mL−1 at 680 and 570 nm, respectively. The limit of detection is 0.3 ng mL−1 Se (IV) at 680 nm. All of the variables that affect the sensitivity in the two wavelengths were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the...

Method for preparing nano bars of cadmiun sulfide

Abstract: A process for preparing the cadmium sulfide nanorods includes proportionally adding mercaptoacetic acid to the solution containing cadmium ions, stirring, proportionally adding sodium sulfide, reaction at 100-500 degC for 1-200 hr, centrifugal treating, and drying Its advantage is no environmental pollution

Phosphor and manufacturing method therefor

Abstract: PROBLEM TO BE SOLVED: To provide a phosphor wherein phosphor particulates such as semiconductor nanoparticles are stably and uniformly dispersed. SOLUTION: A dispersion of clay particulates such as smectite is added to an aqueous zinc nitrate solution. Then, an aqueous sodium sulfide solution is added to the solution to synthesize zinc sulfide nanoparticles. COPYRIGHT: (C)2005,JPO&NCIPI

Removing the cadmium, arsenic and sulfate ions from wet process phosphoric acid

Abstract: Commercially, phosphoric acid is manufactured using different processes. The wet-process is the process applied in Syria using phosphate mineral, and phosphoric acid produced by this process contains a variety of impurities. This paper studies the precipitation of Cd, As and sulfate ions. The results show that the yield of precipitation of sulfate ion increases by increasing the concentration of barium carbonate and temperature. The precipitation of arsenic increases by increasing the concentration of sodium sulfide and temperature. The precipitation of cadmium was better under ambient temperature by sodium sulfide.

Synthesis of anthrathiopyrantriones by heterocyclization of alkynoyl derivatives of chloroanthraquinones

Abstract: A procedure was developed for the synthesis of 2-substituted, including 2-alkenyl-substituted, 4H-anthra[1,2-b]thiopyran-4,7,12-triones and 4H-anthra[2,3-b]thiopyran-4,6,11-triones by cyclocondensation of vic-alkynoylchloroanthraquinones with Na2S.

Processing for granular sodium sulfide

Abstract: A process for producing particulate sodium sulfide, comprises selecting raw material-forging-heat melting-defecating and washing-removing impurities chemically-precipitating-evaporating and concentrating and so on Concentrated sodium sulfide is stored in a reactor or a blender, the content there of is equal to or higher than 60% Sodium sulfide is pumped, impurities are filtered by a filter, thesolution of sodium sulfide entering in a particle machine is at the temperature of 130-150degree C, the transmission pressure of 03-05Mpa After ejecting by a nozzle, the solution is cooling and molding in a steel-tape cooler Solidified particles are unloaded into a feed stock, and are hermetically packed by vacuum packing or plastic bags, then final product is obtained The process of producing particulate sodium sulfide is advanced and reasonably designed The invention provides conditions and devices of producing particles, and adopts the technology of vacuum packing, which prevents effectively deliquescence, oxidization of sodium sulfide, prolong the storage time the invention also adopts a system of automatically packing to reduce labor, improve working environment, save packing cost

Simultaneous and rapid determination of multiple component concentrations in a multi-component chemical process stream

Abstract: The present invention is a rapid method of determining the concentration of the major components in a chemical stream. The present invention is also a simple, low cost, device of determining the in-situ concentration of the major components in a chemical stream. In particular, the present invention provides a useful method for simultaneously determining the concentrations of sodium hydroxide, sodium sulfide and sodium carbonate in aqueous kraft pulping liquors through use of an attenuated total reflectance (ATR) tunnel flow cell or optical probe capable of producing a ultraviolet absorbency spectrum over a wavelength of 190 to 300 nm. In addition, the present invention eliminates the need for manual sampling and dilution previously required to generate analyzable samples. The inventive method can be used in Kraft pulping operations to control white liquor causticizing efficiency, sulfate reduction efficiency in green liquor, oxidation efficiency for oxidized white liquor and the active and effective alkali charge to kraft pulping operations.

Prepn of oil dispersed molybdenum disulfide

Abstract: The present invention is the preparation of oil dispersed molybdenum disulfide as lubricating material. The present invention prepares oleic acid modified and oil dispersed molybdenum disulfide grains with molybdate, molybdenum trioxide, sodium sulfide and hydrochloric acid as main material, CTAB as supplementary material and oleic acid and stearic acid as surface modifier. The present invention provides one new kind of surface modifier superior to available ones. The present invention has the advantages of simple technological process, less operation units, low cost, less material toxicity, short synthesis period and good dispersivity of the modified MoS2 product.

Corrosion Behavior of Copper–Nickel Alloys in Neutral Chloride and Sulfide Containing Solutions

Abstract: The corrosion behavior of Cu30Ni and МНЖМц 30-1-1 alloys in oxygen-containing chloride solutions (0.1–0.5 N NaCl) with and without Na2S additive (2–1000 mg/l) is studied with radiometric and electrochemical methods by taking into account the amount of oxygen sorbed in the course of corrosion. In blank solutions, a film of corrosion products is formed on the alloy surface; the thickness and copper content of the film increase with a decrease in chloride concentration. The corrosion rate in sulfide-containing solutions is higher than in sulfide-free ones. In the initial corrosion period, nickel compounds are accumulated in the film. With an increase in sodium sulfide concentration, corrosion accelerates. Additionally alloying the Cu30Ni alloy with manganese and iron reduces its rate by half.

The role of reductant oxidation state in the formation and function of gold nanoparticle aggregates for SERS applications

Abstract: Sodium sulfide used to produce gold nanoparticle aggregates has been shown to require aging, however, until this work, few studies have attempted to ascertain the nature of this aging effect. UV-vis spectroscopy and other experimental evidence suggest that chemical changes take place during the aging process. NEXAFS has helped determine that sodium sulfide is oxidized over time to form, at least partially, sodium thiosulfate. Experiments performed with sodium thiosulfate yield similar results spectroscopically, however, in SERS experiments it is apparent that the surface chemistry is substantially different. This is likely due to both a lack of sodium sulfide and an increase in thiosulfate concentration. It has also been found that thiosulfate can be utilized for the reduction of several other metal salts into metal and, in some cases, metal sulfide nanoparticles, including copper, platinum, palladium, and silver.

Arsenic removal method

Abstract: PROBLEM TO BE SOLVED: To provide an arsenic removal method which enables the efficient removal of arsenic from service water or wastewater containing a thin concentration of arsenic of ≤10 ppm. SOLUTION: When arsenic is removed from the service water or wastewater containing a thin concentration of arsenic (arsenic-containing water), a sulfidizing agent comprising one or more kinds among hydrogen sulfide, sodium sulfide, and sodium hydrosulfide is added to the arsenic-containing water, and then the mixture is brought into contact with a contact material to perform solid-liquid separation while converting arsenic to solid arsenic sulfide. The arsenic-containing water to which the sulfidizing agent has been added is brought into contact with the contact material in the presence of solid sulfide or sulfur, which can improve treatment efficiency. COPYRIGHT: (C)2005,JPO&NCIPI

Resistência à Corrosão de Ligas Odontológicas Submetidas à Desinfecção

Abstract: The aim of this study was to evaluate the effect of disinfection or sterelization on corrosion resistance of 5 kinds of dental alloys (Ag-Sn, Cu-Al, Cu-Zn, Co-Cr, Ni-Cr). 150 circular samples were obtained with 6 mm in diameter by 3 mm thick, casted, polished and subjected to one of the following treatments: 1% sodium hypochlorite - 30 minutes, alcohol 70 - 30 minutes, 2% glutaraldehyde - 30 minutes, 2% glutaraldehyde - 10 hours, Dry heat oven at 170 °C - 1 hour, Autoclave at 120 °C - 20 minutes. Six cicles of treatment were done, simulating 3 clinic/laboratorial stages. Finally the samples were stored in sodium sulfide 0,25% for 24 hours. The surface was visually examined by 2 examinators and organized according the criteria: 0. Absense of changes, 1. Lost of shinning, 2. slight color change, 3. intense color change, 4. generalized corrosion. The analysis showed that cooper alloys are most susceptible to corrosion and Ni-Cr and Co-Cr alloys are the most resistant, remaining Ag-Sn in an intermediary position. The less agressive disinfecting method was the oven procedure, followed by glutaraldehyde (30 min or 10 hours) and alcohol 70, while sodium hypochlorite and autoclave promoted largest changes.

Double-[3-( triethoxy)silicon propyl]tetrasulfide preparation method

Abstract: A process for preparing bis-(3-[triethoxy silyl propyl]-tetrasulfide by using waterless sodium sulfide, sulfur and chloropropyl triethoxysilane as raw material, sodium as catalyst, ethanol as reaction medium by the mole ratio of sodium sulfide : sulfur : chloropropyl triethoxysilane = 1:3:2:(0.10-0.30) through the steps of, synthesizing sodium polysulfide intermediate product from sodium sulfide and sulfur at the presence of sodium as catalyst and with anhydrous alcohol neutralization and nitrogen protection, dropping chloropropyl triethoxysilane into the reaction solution in the previous step, thus bis-(3-[triethoxy silyl propyl]-tetrasulfide is synthesized, and the finished product is obtained through post-treatment.

Method of removing hydrogen sulfide

Abstract: PROBLEM TO BE SOLVED: To provide a method of removing hydrogen sulfide from a hydrogen sulfide-containing gas with the use of a sodium hydroxide aqueous solution which has excellent effects such that the formation of a polymerized product by aldol condensation reaction caused in an absorption tower due to the presence of an aldehyde or a ketone in the hydrogen sulfide-containing gas is reduced and staining of the absorption tower can be reduced SOLUTION: The method of removing hydrogen sulfide comprises a step 1 of bringing a hydrogen sulfide-containing gas into contact with a sodium hydroxide aqueous solution in an absorption tower, converting hydrogen sulfide into sodium hydrogensulfide (NaSH), and obtaining an aqueous phase (2) containing the sodium hydrogensulfide; a step 2 of guiding the aqueous phase (2) containing the sodium hydrogensulfide out of the absorption tower in the step 1, bringing it into contact with a sodium hydroxide aqueous solution to convert the sodium hydrogensulfide into sodium sulfide (Na 2 S), and obtaining an aqueous phase (3) containing the sodium sulfide; and a step 3 of burning the aqueous phase (3) containing the sodium sulfide COPYRIGHT: (C)2005,JPO&NCIPI

2(2-chlorine-4-phenyl fluoride) bisulfide, preparation and aplication

Abstract: A novel bis (2-chloro-4-fluorophenyl) bisulfide is prepared from 3,4-dichloronitrobenzene, sodium sulfide, sulfur, H2O2, sodium nitrite, fluoroboric acid, hydrochloric acid, nitric acid and smoke sulfuric acid. Its application is also disclosed. Its advantages are high purity and selectivity.

Agar-immobilized Metal Sulfides and Their Sorption Power with Respect to Ag(I) Ions

Abstract: Thin-film systems based on sulfides of various p and d elements (MS) efficiently sorb noble and toxic metals from wastewater and spent process solutions by the ion-exchange mechanism. Previously such systems were prepared in most cases by chemical deposition of metal sulfides in the form of microcrystalline films on various supports (cellulose [1], cellulose triacetate [2], glass [3]). All these sorbents are characterized by micrometric particle size, which limits their performance in sorption of noble and toxic metals, if for no other reason than long sorption time. In [4] we suggested a procedure for preparing gelatin-immobilized metal sulfide matrix systems with quasimolecular level of MS dispersity. Sorption of metal ions, in particular, Ag(I), from wastewater and spent process solutions with such sorbents is fairly fast and complete. However, the gelatin layers exhibit relatively poor adhesion to the polyethylene terephthalate support and can exfoliate, which complicates further operation and utilization of the sorbent. Therefore, it is preferable to use polymer systems in which the nanometric particle size of the immobilized metal sulfides is preserved but no foreign support is required. One of polymeric materials suitable for this purpose is agarose, linear polysaccharide built from regularly alternating residues of 3-O-substituted -D-galactopyranose (occasionally, 6-O-methyl-D-galactopyranose) and 4-O-substituted 3,6-anhydro-L-galactopyranose. Agarose is the main component of agar natural polymer recovered from red algae [5]. Agarimmobilized metal sulfide matrices (MS AIM) are prepared in two steps. In the first step, agar is added into an aqueous solution containing an appropriate metal salt (nitrate, chloride, sulfate); the mixture is heated to 90 95 C and added with a buret or pipet into a vessel with water cooled to 10 15 C. The globules formed in the process are treated in the second step at room temperature with an aqueous solution of sodium sulfide to obtain the desired metal sulfide MS (M = Cu, Zn, Pb, etc.) by exchange reactions. These globules are fairly stable to aqueous solutions at widely varied pH (from 2 to 13) and temperature (up to 100 C) and to physicomechanical stresses. According to elemental analysis, the particle size of the sulfides implanted in MS-AIM is 10 15 nm on the average and does not exceed 20 nm.