Aqueous Solutions Of Sodium Sulfide Research Articles

Air oxidation of aqueous sodium sulfide solutions with coal fly ash

The potential of coal fly ash was studied as a catalyst in the air oxidation of aqueous sodium sulfide (Na 2S) solutions in the temperature range of 303–333 K. The rate of oxidation was found to be independent of the initial concentration of Na 2S in the range of 5.80×10 −2–28.45×10 −2 kmol/m 3. The effects of fly ash loading, source of fly ash, speed of agitation, air flow rate, fly ash particle size were also studied. Experimental results suggested a film-diffusion controlled reaction mechanism and 4% fly ash loading intensified the reaction rate by a factor of 3.5 over that of without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 31% even after fifth repeated uses.

Dissolution kinetics of glassy and crystalline As 2S 3 in aqueous sodium sulfide and hydroxide

Dissolution kinetics of glassy and crystalline As 2S 3 in aqueous sodium sulfide and hydroxide solutions was investigated. Glass, produced by rapid quenching contains frozen products of arsenic trisulfide dissociation — As 4S 4 and S. A strong change in the chemical behavior of g- and c-As 2S 3 has been found in its interaction with hydroxide ions. A mechanism of dissolving has been suggested.

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

The potential of fly ash procured form coal-fired thermal power plants was studied as a heterogeneous catalyst in the oxidation of aqueous sodium sulfide solutions with hydrogen peroxide in the temperature range of 303–323 K. The effects of various parameters (source of fly ash, fly ash loading, initial concentrations of sodium sulfide and hydrogen peroxide, electrolyte and deactivation of catalytic effect of fly ash) were studied. For an initial sodium sulfide and hydrogen peroxide concentration of 26·98×10−2 kmol m−3 and 24·28×10−2 kmol m−3 respectively, only 4% (w/v) fly ash loading intensified the rate of oxidation by a factor of 4·52 over that without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 20% even after six repeated uses. The kinetics of aqueous phase decomposition of hydrogen peroxide was also studied in the presence of fly ash in alkaline medium. ©1997 SCI

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

NiPS3Intercalates as Catalysts for the Oxidation of Sulfide Ions: Synthesis, Catalytic Activity, and XPS Study

Several intercalates of layered NiPS3have been synthesized by reaction of this compound with aqueous solutions of sodium sulfide and subsequent cation exchange or polymer insertion. The catalytic efficiency of these intercalates for the oxydation of sulfide ions into elemental sulfur by dioxygen has been studied. Results show that these intercalates have a greater efficiency than pristine NiPS3(higher reaction rate, smaller activation energy, suppression of any induction period). The electronic structure of the intercalates has been studied mainly by XPS of the Ni, P, and S atoms. Although the chemistry accompanying the intercalation processes appears complex (small losses of phosphorus, appearance of phosphate, and thiophosphate PS43−species), the catalytic efficiency of the intercalates is correlated to their ability to be reduced in depth when brought in contact with aqueous sodium sulfide. Our results are consistent with a previously suggested catalytic mechanism based on sequences of intercalation/deintercalation processes of sodium ions associated to redox modifications of the host lattice.

Reactions of nitrochlorobenzenes with sodium sulfide: change in selectivity with phase-transfer catalysts

o-Nitro- and p-nitrochlorobenzene were reduced to the corresponding chloroanilines with aqueous solutions of sodium sulfide both in the presence and absence of a phase-transfer catalyst. The use of phase-transfer catalysts, with solid sodium sulfide, was found to change the course of the reaction completely to dinitrodiphenyl sulfide. The role of mass transfer in the system was assessed with m-nitrochlorobenzene as the organic substrate.

SYNTHESIS AND SOME REACTIONS OF ARYLPYRIDYLSULFIDE DERIVATIVES

Abstract The title compound (I) was prepared from the reaction of 2-chloro-3-cyano-4,6-dimethylpyridine and 4-bromonitrobenzene in aqueous sodium sulfide solution. Condensation of I with aromatic aldehydes, 2-methyl benzoxazin-4-one, azalactone and succinic anhydride afforded the expected products (IV, VI, VIII and XV). Coupling of diazotized I with active methylene compounds gave the corresponding hydrazones Xa,b. Cyclization of hydrazone Xa with AICl3 gave the cinnoline derivative XII, which condensed with phenylhydrazine to give the pyrazolocinnoline derivative XIII. Oxidation of some of the prepared sulfides with H2O2 in AcOH afforded the corresponding sulfones.

Cyanomethyl Esters: Useful Protection for Carboxylic Acids

Abstract The alkylation of carboxylate salts with chloroacetonitrile yields cyanomethyl esters. Deprotection of the carboxyl group is most readily performed by stirring with an aqueous solution of sodium sulfide.

PH and conductivity of concentrated aqueous sodium sulfide/sodium carbonate solutions undergoing carbonation

AbstractThe extent of conversion of Na2S to H2S in a concentrated aqueous solution of sodium sulfide and sodium carbonate undergoing carbonation can be monitored by measuring the pH and conductivity. A simple linear equation has been developed to correlate the percentage of Na as Na2S with the temperature, pH, and conductivity. The apparent hydrolysis constants for carbonate and sulfide were calculated at temperatures ranging between 25°C and 65°C, and the reaction enthalpies and entropies determined.

Résistance à la corrosion d’alliages cuivreux utilisés en connectique

For connectics applications, selection of an alloy takes into account the feasibility of protective coatings (such as gold, nickel, tin... etc), as well as their physical and mechanical properties.The hight cost of gold, for instance, has led to selective deposits, the thickness of which has been continuously decreasing ; thus, the influence of the substrate has become an important factor for the corrosion resistance of the connectors.The selection of a corrosion resistant alloy will improve the behaviour of the protected part.In this respect, some copper and/or nickel alloys have been tested for corrosion, by H2 S alone and by a mixture H2 S + SO2 .They also have been studied through electro-chemistry, in aqueous solutions of sodium sulfide, in order to compare their behaviour in this medium and in agressive atmosphere.The follow-up of corrosion, whatever the process, has been carried out through electro-chemical reduction curves, and completed using physico-chemical techniques such as X-ray diffraction, EDX, and XPS.

Effect of platinum loading on the photocatalytic activity and luminescence of cadmium sulfide powder

The effect of platinum loading on the efficiency of CdS-photocatalyzed hydrogen evolution from an aqueous solution of sodium sulfide and on the intensity of the green emission (510 nm) of CdS suspended in the same solution was studied. The Fermi level of the CdS photocatalyst at the working condition can be estimated from the intensity of the green emission of the platinum-loaded CdS powder and the luminescence-potential curve of a CdS electrode. When the amount of platinum deposited on CdS is increased, the Fermi level of CdS at the working stage is moved down toward more positive potential, leading to a stronger band bending, and the photocatalytic reaction is stimulated. Too much Pt loading, however, lowers the photocatalytic activity because of the enhanced rate of electron-hole recombination as well as light absorption by platinum. The temperature effect on the reactivity and the reason for the presence of an induction period of the reaction are also elucidated in relation with the band bending of the photocatalyst.

Detection of lead in human teeth by exposure to aqueous sulfide solutions.

A recent study has shown that the presence of lead (Pb) as well as other base metals in esthetic restorative materials, especially dental cements, is detectable by color shifts induced by exposure of hardened specimens to a 0.1% (w/v) aqueous solution of sodium sulfide, Na2S. The present study was initiated to determine the applicability of this simple exposure test to the detection of Pb in human teeth. Extracted whole teeth as well as sectioned, thin specimens were exposed first to either a 0.01% or a 0.001% (w/v) aqueous solution of lead nitrate, Pb (NO3)2, at 37 degrees C for 24 h. After rinsing with distilled H2O and a subsequent 24 h exposure to the 0.1% Na2S solution at 37 degrees C, the tooth specimens were examined visually and by a dental color analyzer for color changes. The latter color measurements were evaluated by the Lab system of Hunter, and the color difference, delta E, was determined. Neither control specimens exposed to distilled H2O only or to 0.1% Na2S only exhibited any significant change in appearance after 24 h of storage at 37 degrees C. However, specimens exposed first to the Pb (NO3)2 solutions showed discernible delta E values after exposure to the Na2S solution. Delta E was greatest for specimens exposed to the more concentrated Pb (NO3)2 solution. Most of the discoloration in both thin and intact tooth specimens was confined to the outermost layers of the tooth structure. For the intact specimens, the greatest degree of discoloration occurred in the cementum, the most permeable part of the tooth structure.

Oxidation of aqueous sodium sulfide solutions with activated carbon

Oxidation of aqueous sodium sulfide solutions with activated carbon

Raman Spectrum of Selenium Dissolved in an Aqueous Solution of Sodium Sulfide

The Raman spectrum of selenium dissolved in an aqueous solution of sodium sulfide was measured using an YAG laser and a multiple-reflection cell, and an intense broad band was observed at 264 cm-1. This frequency is higher than those of the corresponding symmetric bond-stretclaing modes in any solid form of selenium. This is explained by considering the decrease of the interference between inter- and intramolecular bondings in the solution.

Chemical pretreatment of silver wire containing copper for preparation of silver/silver sulfide ion-selective electrode

The silver/silver sulfide ion selective electrode (ISE) has been produced in a variety of forms. While the membrane type reportedly exhibits superior performance characteristics in comparison to the type derived from solid silver, the latter offers decided advantages in terms of cost and convenience. We wish to report that a microscale silver/silver sulfide ISE can be readily prepared from silver wire (0, 7 mm diameter) which contains 2, 5-6% Cu (w/w) by exposing the wire to a deaerated aqueous solution of sodium sulfide, ascorbic acid, and etbylenediaminetetraacetic acid (SAOB-H) for 2 days. Although this procedure is similar to one reported in the manufacturers' literature, it is significant that a successful ISE could not be prepared by this technique if pure silver (99.99%) was used or if the SAOB-II solution was not deaerated. Finally, the performance of electrodes obtained in this manner was basically indistinguishable from that of a commercially available electrode of the membrane type.

Absorption of oxygen in aqueous solutions of sodium sulfide in the presence of activated carbon as catalyst

Absorption of oxygen in aqueous solutions of sodium sulfide in the presence of activated carbon as catalyst

The spectral photoelectric sensitivity of silver sulphide and several other substances

Ag2S/Ag heteronanostructure has been produced by a simple one-stage chemical deposition from aqueous solutions of silver nitrate, sodium sulfide, and sodium citrate with the use of monochromatic light irradiation. The formation of Ag2S/Ag nanocomposite structures is confirmed by X-ray analysis, high-resolution electron microscopy, and energy dispersion analysis. It is established that in the contact layer between silver sulfide and silver, nonconductingα-Ag2S acanthite transforms into superionic β-Ag2S argentite under the action of external electric field. The scheme of the operation of a resistive switch based on an Ag2S/Ag heteronanostructure is proposed.