Showing papers on "Sodium sulfide published in 2000"

Surface recombination and sulfide passivation of GaN

Abstract: The surface recombination velocity in n-type heteroepitaxial GaN(0001) is shown to decrease dramatically when the surface is chemically treated with aqueous and alcoholic solutions of inorganic sulfides, such as ammonium or sodium sulfide (NH4)2Sx and Na2S). The room-temperature excitonic photoluminescence (PL) intensity increases by a factor of four to six after treatment, and improvements persist for at least seven months in room air. Various other chemicals commonly used in device processing are investigated and shown to change the PL intensity by factors ranging from 0.7 to 2.5, buffered oxide etching being the most beneficial. Schottky barrier diodes using gold as the contact metal are fabricated using a sulfide treatment prior to evaporation. The barrier height from capacitance-voltage measurements is as high as 1.63 ± 0.07 V, the highest value ever achieved on n-GaN. This result is evidence that the effect of surface states on the Fermi level has been substantially reduced by the treatment.

Electrochemical Study of Chemically Modified and Screen-Printed Graphite Electrodes with [SbVO(CHL)2]Hex. Application for the Selective Determination of Sulfide

Abstract: The preparation and electrochemical characterization of graphite electrodes modified with hexadecylpyridinium−bis(chloranilato)−antimonyl(V), [SbVO(CHL)2]Hex, (CMEs) as well as their behavior as electrocatalysts toward the oxidation of sulfide are described. The self-exchange rate constant ko of immobilized [SbVO(CHL)2]Hex and the effect of the surface coverage were evaluated. [SbVO(CHL)2]Hex is a new compound. Synthesis protocol and some identification studies are given. The fabrication of screen-printed electrodes (SPEs) with a mixture of 5% (w/w) [SbVO(CHL)2]Hex/graphite powder in 1.5% (w/v) ethyl cellulose in 2-butoxyethyl acetate is also described. SPEs, poised at +0.08 mV versus Ag/AgCl, at pH 6.5 were utilized for the determination of sulfide in simulated wastewater samples. Interference of various compounds was also tested. The proposed method correlates well with a colorimetric method. Calibration graphs were linear over the range 0.01−0.7 mM sodium sulfide and the CV was 2.8% (n = 8) for 0.1 mM ...

Oxidation and photooxidation of sulfide and thiosulfate ions catalyzed by transition metal chalcogenides and phthalocyanine complexes

Abstract: The catalytic and photocatalytic activities of supported cobalt or zinc phthalocyanine complexes, bulk MoS2, MoS2 deposited on Al2O3, potassium intercalated MoS2 (K0.33 H2O0.66 MoS2), CdS and polycrystalline nickel phosphorus trisulfide (NiPS3) have been investigated in the oxidation of sodium sulfide and Na2S2O3. The phthalocyanine complexes and the metal chalcogenides do not catalyze, in the absence of light, the complete oxidation of the sulfide ion to sulfate ion. The final product of the catalytic oxidation is the formed thiosulfate. No oxidation of Na2S2O3 has been registered in the dark in the presence of any of the catalytic samples. Their activity was enhanced upon irradiation with visible light. Thiosulfate appears to be the final product also of the photooxidation of the sulfide ion catalyzed by metal chalcogenides. They do not catalyze the further photooxidation of Na2S2O3. The only photocatalysts which favour with their presence the oxidation of the sulfide and thiosulfate ions to sulfate ion, are the zinc phthalocyanine complexes. In this case, the photooxidation process involves singlet oxygen.

In vitro and in vivo corrosion evaluation of nickel-chromium- and copper-aluminum-based alloys.

Abstract: Statement of Problem. The low resistance to corrosion is the major problem related to the use of copper-aluminum alloys. Purpose. This in vitro and in vivo study evaluated the corrosion of 2 copper-aluminum alloys (Cu-Al and Cu-Al-Zn) compared with a nickel-chromium alloy. Material and Methods. For the in vitro test, specimens were immersed in the following 3 corrosion solutions: artificial saliva, 0.9% sodium chloride, and 1.0% sodium sulfide. For the in vivo test, specimens were embedded in complete dentures, so that one surface was left exposed. The 3 testing sites were (1) close to the oral mucosa (partial self-cleaning site), (2) surface exposed to the oral cavity (self-cleaning site), and (3) specimen bottom surface exposed to the saliva by means of a tunnel-shaped perforation (non-self-cleaning site). Results. Almost no corrosion occurred with the nickel-chromium alloy, for either the in vitro or in vivo test. On the other hand, the 2 copper-aluminum-based alloys exhibited high corrosion in the sulfide solution. These same alloys also underwent high corrosion in non-self-cleaning sites for the in vivo test, although minimal attack was observed in self-cleaning sites. Conclusion. The nickel-chromium alloy presented high resistance to corrosion. Both copper-aluminum alloys showed considerable corrosion in the sulfide solution and clinically in the non-self-cleaning site. However, in self-cleaning sites these 2 alloys did not show substantial corrosion. (J Prosthet Dent 2000;84:360-3.)

A Comparison of Sodium Hydroxide and Sodium Sulfide Digestion of Mouse Hair in the Recovery of Radioactivity Following Systemic Administration of [3H]-Nicotine and [3H]-Flunitrazepam

Abstract: Pigmented (C57BI) and nonpigmented (balb/c) mice, 25 days of age, were treated intraperitoneally with [3H]-nicotine (4 mg/kg, 555 dpm/ng) or [3H]-flunitrazepam (1 mg/kg, 2200 dpm/ng) daily for three days. After 21 days, shaved back hair was digested at 37 degrees C for 24 h with either 1 M sodium hydroxide or 1 M sodium sulfide. With both drugs, sodium sulfide extraction removed the same amount of radioactivity as sodium hydroxide from nonpigmented hair. However, sodium sulfide removed significantly more radioactivity from pigmented hair than did sodium hydroxide. In pigmented hair, sodium sulfide solubilized 35% and 74% of the flunitrazepam- and nicotine-associated radioactivity, respectively. Of this, 12% and 43%, respectively, could be partitioned into ethyl acetate. Microscopic examination of residual pellets after digestion demonstrated a more thorough dissolution of the hair shaft with sodium sulfide with only melanosomes remaining. The results demonstrate the significant interaction of flunitrazepam and nicotine with melanins and the utility of sodium sulfide in increasing drug recovery.

Characteristics of third phase for reaction of benzyl chloride with sodium sulfide in phase transfer catalytic system

Abstract: The purpose of this study is to investigate how the property of third phase affects the reaction rate in a phase transfer catalytic reaction system. Dibenzyl sulfide was produced by the reaction between sodium sulfide in an aqueous phase and benzyl chloride in an organic phase by using tetrahexylammonium bromide ((Hex) 4 NBr) as a phase transfer catalyst. As the concentration of sodium sulfide in the aqueous phase and the temperature increased, the third phase was more easily formed. Three types for temperature dependencies on the reaction rate were observed. The reaction rate in one type initially increased, suddenly decreased, and then increased again. The other reaction rates in two types increased with the increase in temperature but the difference between them was 20–50 times at the same temperature. These behaviors could be explained by the property of third phase, especially, the lipophilicity or the hydrophilicity.

Influence of Sulfate-Reducing Bacteria on Outdoor Hydrogen Production by Photosynthetic Bacterium with Seawater

Abstract: The application of seawater for bacterial fermentative production is a cost-effective technology. Hydrogen production by marine photosynthetic bacterium with seawater failed to continue after more than 10 days, and was accompanied by the formation of hydrogen sulfide and a change in culture color from red to black. However, substrate consumption in the blackish culture was comparable to that in a hydrogen-producing culture. A decrease in hydrogen production occurred upon the addition of sodium sulfide at concentrations of 1.5 mM or higher. PCR analysis targeted at the 16S rDNA sequence selective for sulfate-reducing bacteria revealed the existence of sulfate-reducing bacteria in inoculation cultures of the phototrophic bacterium and medium for hydrogen production. Hence, the high sulfate concentration of seawater, the low oxidation-reduction potential under hydrogen-producing conditions, and the presence of electron donors such as acetate might promote the metabolic activities of sulfate-reducing bacteria, resulting in the deterioration of hydrogen production with seawater.

Process for removing selenium and mercury from aqueous solutions

Abstract: The present invention relates to an apparatus for removing volatile impurities such as mercury and selenium from a weak acid solution resulting from scrubbing gases created in the production of sulfuric acid by roasting of sulfide concentrates. The apparatus comprises a calcine filtering unit for removing calcine from the weak acid solution, a sodium sulfide mixing unit for precipitating mercury from the weak acid solution, a sodium dithionite mixing unit for precipitating selenium from the weak acid solution, and a mercury-selenium filtering unit for filtering the precipitated mercury and selenium from the weak acid solution. The present invention further relates to a treatment plant utilizing such an apparatus, a process for removing volatile impurities from a weak acid solution, and a selenium cake obtained by utilizing the present invention.

Studies on large area (50 cm2) MoS2 thin films deposited using successive ionic layer adsorption and reaction (SILAR) method

Abstract: A simple method, successive ionic layer adsorption and reaction (SILAR) has been employed to deposit MoS 2 thin films onto various substrates using ammonium molybdate and sodium sulfide as cation and anion precursor solutions, respectively. Preparative conditions such as concentration, pH and temperature of precursor solutions and adsorption, reaction and rinsing time durations were optimized, The films were deposited onto microslide glass (∼50 cm 2 ), fluorine doped tin oxide (FTO) coated glass (∼6cm 2 ) and Si (111) wafer (2cm 2 ) substrates. X-ray diffraction, optical absorption, electrical resistivity and thermoemf measurement techniques were used for the characterization of the films.

Removal of zinc from rubber thread manufacturing industry wastewater using chemical precipitant/flocculant

Abstract: Wastewater from the rubber thread manufacturing industry is acidic in nature with PH in the range of 38 to 44 and containing high concentrations of COD, BOD, Total-N and zinc The high BOD and COD ratio of the wastewater (078 to 090) indicates that the rubber wastewater is biodegradable and can be treated effectively by an anaerobic digestion process commonly employed in this industry However, because the wastewater contained high concentrations of zinc, 250 to 310 mg/L, which could inhibit the digestion process, it was pretreated by chemical precipitation/flocculation A treatment process using a combination of sodium sulfide and polyelectrolyte LT 27 at concentrations of 800 and 5 mg/L, respectively, is the most cost-effective system for zinc removal from the wastewater Zinc removal by sodium sulfide is not affected by pH The optimum settling time was 60 min, whereas the optimum flocculation time was 20 min, and a speed of 20 rpm in a 110 mm diameter reactor gave the best res The estimated cost of zinc removal using this method was RM104/m(3) (US $026/m(3)) of wastewater discharged

Process for preparing high-purity active zinc oxide by immersing in ammonia water and ammonium carbonate solution and complexing

Abstract: A process for preparing high-purity active zinc oxide includes such steps as complex immersing of low-grade zinc oxide as raw material in mixture of ammonia water and ammonium dicarbonate, three-stepremoving impurities with sodium sulfide, zinc powder and activated carbon, analyzing, dewatering, baking and calcining. Said ammonia water can be cyclically used. Its advantages are simple process, basically no environmental pollution, low energy consumption, low cost and low content of harmful impurity in product.

Silver impregnated contact lens comprises body formed of matrix with silver with sulfide, halogenide and oxide, with silver precipitated and diffused

Abstract: The silver-impregnated contact lens comprises a lens body formed of a porous matrix in which the silver has at least a proportion of sulfide, halogenide, oxide and or is amorphous. The silver, especially in the form of silver nitrate, is diffused into the contact lens and finally is precipitated as silver sulfide, with a sulfur-content compound, especially sodium sulfide.

Production technology of yellow flaky sodium sulfide with low carbon and iron contents

Abstract: Raw materials of saltpeter and anthracite are mixed in the ratio of 3 to 1 and high-temperature calcined to produce stock sodium sulfide which is hot dissolved to obtain sodium sulfide solution as intermediate. Compounded barium sulfide and zinc sulfate solution is added to the intermediate to eliminate impurities, the precipitated and clarified sodium sulfide solution is evaporated for concentration, and the concentrate is tabletted and packaged as product. The said technological process has obvious iron eliminating effect, and through the application of special steel smelting technology, the ultimate product has an iron content not more than 80 ppm.

Polymerization characteristics and thermal degradation study of poly(phenylene sulfide ketone)

Abstract: Poly(phenylene sulfide ketone) (PPSK) was synthesized by the reaction of sodium sulfide with 4,4'-dichlorobenzophenone in N-methyl-2-pyrrolidinone through the Phillips process. The effect of water hydration of sodium sulfide in solution, polymerization temperature, polymerization time, and stoichiometric ratio of monomers on the polymerization behavior of PPSK were investigated with respect to inherent viscosity and yield. Thermal degradation parameters of PPSK synthesized were investigated by dynamic thermogravimetry. To determine thermal degradation energy, Kissinger, Ozawa, and Friedman methods were used and activation energies were 202.3, 233.6, and 232.2 kJ/mol, respectively.

Alkaline leaching of metal melting industry wastes and separation of zinc and lead in the leach solution

Abstract: In this work, a thorough examinations on the extractability of zinc and lead present in the steelmaking dusts using alkaline leaching process and the effectiveness of the zinc and lead separation in the resultant leaching solutions using sulfide precipitation method were made. It was found that only about 53% of zinc and over 70% of the lead could be leached out of the dusts, while the other 47% of zinc and 30% of lead were left in the leaching residues. The zinc and lead in the resultant leaching solution can be effectively and selectively separated. When the weight ratio of sodium sulfide (M.W.=222—240) to Pb was kept at 1.8, the lead in the solution could be precipitated out quantitatively while all the zinc was remained in the solution. The zinc left in the solution can be further recovered by the addition of extra sodium sulfide with a weight ratio of sodium sulfide to the zinc over 2.6. The resultant filtrate can be recycled to the leaching of dust in the next leaching process.

New compound, organic polymer, resin composition, non- linear optical part and non-linear optical device

Abstract: PROBLEM TO BE SOLVED: To obtain a new compound having a non-linear optical activity and useful for non-linear optical devices. SOLUTION: An aromatic compound of formula I [R1, R2 are each an alkyl or an aryl; R3 is H, an alkyl, an aryl or an electron-imparting functional group; R4 is H, an alkyl, an aryl or an electron-attracting functional group; R5 is H, an aryl or the like; X is H, a (connectable functional group) monovalent organic group; (p) is 1-3]. For example, a compound of formula II. The compound of formula I is obtained, for example, by selectively reducing a dinitro compound of formula III with a reducing agent such as lithium aluminum hydride, treating the obtained monoamine compound of formula IV with a reducing agent (for example, sodium sulfide) or an organic metal reagent (for example, methyl lithium) to obtain the compound of formula I (X is H), and subsequently introducing a proper monovalent functional group X to the obtained compound of formula I.

Process for the preparation of anhydrous sodium sulfide

Abstract: A process is disclosed for the preparation of anhydrous sodium sulfide by heating sodium sulfide having a water content of from 38 to 40% in a contact drier in vacuo, the temperature of the solid to be dried being increased from approximately 20° C. at the solid inlet to ≧180° C. at the solid outlet.

Process and equipment for preparing bittern mirabilite and separating anhydrous sodium sulfide

Abstract: A process and equipment for preparing bittern from mirabilite and separating out anhydrous sodium sulfate includes dissolving mirabilite, preparing mixed liquid, removing sand and water in drum sieve, and water washing

Synthesis of Dibenzyl Sulfide,Dibenzyl Sulfoxide and Dibenzyl Sulfone

Abstract: Effects of solvent, sodium sulfide dosage, reaction time and reaction temperature in syn thesis of dibenzyl sulfide from benzyl chloride with sodium sulfide without catalyst were studied Dibenzyl sulfoxide and dibenzyl sulfone were synthesized from dibenzyl sulfide oxidated with H 2O 2 without catalyst

Electrochemical oxidation of sodium sulfide on rotating ring-disc electrode

Abstract: A rotating ring (Pt) disc (Pt) electrode was employed to investigate the oxidation process of sodium sulfide (Na 2S) It was reported that the oxidation intermediates and product of HS - were formed on the disc electrode and then reduced on the ring electrode The results indicate that at a rotation rate of 20 Hz, when the disc electrode potential was -015 V (vs SHE) and higher, more extensive oxidation process took place via a series of electrochemical steps to produce sulfur (S) The products of oxidation intermediates (S 2- x , S 2- 2) and sulfur (S) reduced either on the ring electrode with a set potential of -08 V (vs SHE), or on disc electrode with negative going potential sweep at about -05～ 055 V (vs SHE) The experimental results of voltammogram of ring disc electrode at sodium sulfide solution demonstrated that the first step was the oxidation of HS - and produce S 2- x , and then the S 2- x adsorbed integrated itself and formed sulfur (S)

Etching liquid, etching method, and manufacture of semiconductor device

Abstract: PROBLEM TO BE SOLVED: To provide an etching liquid in which only Se or Se oxide film is liquated selectively and in a short time from the surface of ZnSe crystal at room temperature. SOLUTION: For an etching liquid wherein sodium sulfide (Na2S) is mixed with water (H2O), by setting the concentration of sodium sulfide (Na2S) to 0.1-50 wt.%, the etching amount of Se can be made 10-1,000 times as large with respect to that of ZnSe.