Concentration Of Sodium Sulfide Research Articles

Isolation and identification of the thermophilic alkaline desulphuricant strain

A desulfurization strain that belongs to the thermophilic alkaline desulphuricant is designated as strain GDJ-3 and isolated from Inner Mongolia, China. The colony of the strain shows tiny, yellow, or white-yellow, and it becomes henna with the protracting of cultivated time. The cells are bacilliform (0.3−0.6 × 1.0−1.2 μm), motive, and Gram negative. The strain GDJ-3 is able to utilize respectively the thiosulphate, sulfate, sulfite, or sulfide as sulfur source, utilize the carbon dioxide as the carbon source, and utilize the ammonium or nitrate as the nitrogen source. According to GenBank data, 16s RNA results of GDJ-3 are in good agreement with Alpha proteobacterrium sp. (97%) and Ochrobactrum sp. (98%). For GDJ-3, the optimum growth temperature is at 45°C, the optimum pH is at 8.5–8.8, and the optimum rocking speed of sorting table is at 150 r/min. Under the optimum culture condition, the cells of the strain can live for about 18 h. In the desulfurization solution, which is prepared according to the composition of DDS solution, the objectionable constituents of sodium thiosulphate and sodium sulfide were added factitiously, and the bacterial cell concentration was set at 107/mL. After the regeneration of the above desulfurization solution by the strain cells, the concentration of sodium thiosulphate was decreased by 14.75 g/L (percentage loss of content 13.21%), the concentration of sodium sulfide was decreased by 0.76 g/L (percentage loss of content 87.36%) in the desulfurization solution in 9.5 hours, and sulfur appeared. Maybe, this kind of strain can be used as the regeneration’s bacterial source of DDS solution.

A review of effects of silver, lead, sulfide and carbonaceous matter on gold cyanidation and mechanistic interpretation

Despite the wealth of published data on the beneficial or detrimental effects of silver, lead, sulfide, and carbonaceous matter on the rate of gold cyanidation at an anode or by dissolved oxygen, the lack of comparative studies on relative effects has hampered rationalisation of the role of these activators or passivators of gold. In the present study, the published rate data per unit surface area of gold, silver, and gold–silver alloys based on electrochemical or chemical dissolution of rotating discs or foils of constant surface area in aerated cyanide solutions at ambient temperatures are analysed on the basis of the Levich equation. The current status of the reaction mechanism is also reviewed and updated on the basis of species distribution and potential–pH diagrams, stoichiometric factors, and interim chemical species of gold(I), silver(I), and lead(II). The anodic peak potentials of reported voltammograms closely follow the potential–pH lines of Au(I)/Au(0) and Pb(II)/Pb(0) couples. Despite the formation of stable complexes between lead(II), nitrate, and hydroxide ions, the total calculated soluble lead(II) in alkaline solutions of pH range 10–11 saturated with lead hydroxide is shown to be < 0.1 g/m 3. A comparison of the reported diffusion coefficients of cyanide ions and dissolved oxygen with the values based on the Levich plots of reported rates reveals the rate-controlling stoichiometric M/CN or M/O 2 molar ratios. The difference between some of these ratios and the generally accepted ratios of M/CN = 1/2 and M/O 2 = 1/0.5 or 1/0.25 based on the formation of M(CN) 2 −, H 2O 2 or OH − in the overall cyanidation reaction is attributed to the oxidation of cyanide to cyanate and passivation due to the formation of gold hydroxides/oxides. The alloyed or dissolved silver and lead eliminate passivation due to the involvement of mixed hydroxo–cyano complexes of silver and lead ions in the surface reaction. Gold dissolution by oxygen in cyanide-rich solutions is limited by oxygen diffusion, but enhanced by the presence of a low concentration of sodium sulfide due to the involvement of hydrosulfide ion in the surface reaction. However, excess lead or sulfide retards gold cyanidation due to surface blockage by metallic lead, lead hydroxide, or due to passivation by Au 2S/S. Even low concentrations of hydrosulfide passivate gold–silver alloys due to the formation of Ag 2S. This can be eliminated by adding stoichiometric quantities of lead(II) to precipitate sulfide as PbS. Large stoichiometric ratios of O 2/M for the cyanidation of graphite coated gold appears to be a result of the enhanced oxidation of cyanide by oxygen or hydrogen peroxide, leading to a cyanide deficiency at the surface and passivation of gold by hydroxide/oxide. The presence of excess cyanide or lead(II) does not override this effect.

Optimization of acetic acid production from synthesis gas by chemolithotrophic bacterium – Clostridium aceticum using statistical approach

Efforts in optimizing reducing agents, cysteine-HCl · H 2O and sodium sulfide in order to attain satisfactory responses during acetic acid fermentation have been carried out in this study. Cysteine-HCl · H 2O each with five concentrations (0.00–0.50 g/L) was optimized one at a time and followed by sodium sulfide component (0.00–0.50 g/L). Response surface methodology (RSM) was used to determine the optimum concentrations of cysteine-HCl · H 2O and sodium sulfide. The statistical analysis showed that the amount of cells produced and efficiency in CO conversion were not affected by sodium sulfide concentration. However, sodium sulfide is required as it does influence the acetic acid production. The optimum reducing agents for acetic acid fermentation was at 0.30 g/L cysteine-HCl · H 2O and sodium sulfide respectively and when operated for 60 h cultivation time resulted in 1.28 g/L acetic acid production and 100% CO conversion.

Electrochemical noise analysis of corrosion of pure aluminium in alkaline solution in the presence of SO 42− ion, NO 3− ion and Na 2S additives

The electrochemical noises obtained from pure aluminium in an alkaline solution have been analysed as a function of sulphate, nitrate or sodium sulphide concentration. A stochastic theory has been applied to the experimentally obtained electrochemical noises based upon the Weibull distribution function. From the occurrence of two linear regions on one Weibull probability plot, the present analysis method permitted us to distinguish between the dissolution of Al and the stochastic process concerning the series of nucleation, growth and detachment of hydrogen bubbles in an engineering sense. Moreover, the conditional event generation rate and the average charge in each event were quantitatively determined for the stochastic process of hydrogen bubbles as well as the dissolution of Al. Effects of sulphate, nitrate and sodium sulphide additives on the corrosion of pure aluminium in an alkaline solution have been discussed in terms of the conditional event generation rate and the average charge in each event.

Spectral Monitoring of the Formation and Degradation of Polysulfide Ions in Alkaline Conditions

The recently developed protocol for the absolute determination of the various polysulfide species based by 1H NMR was applied to monitor the amount of such ions in alkaline media produced at different conditions. The thermal stability of each individual polysulfide species was also evaluated in temperature ranges representative of a typical alkaline pulping process. Overall, the species, S12-, S22-, S32-, S42-, S52-, and S62- were detected and quantified in all alkaline conditions evaluated. The concentration of sodium sulfide and the temperature were found to have a significant effect on the total amount of polysulfides detected. In summary, the di- and trisulfide anions were found to predominate over the other polysulfide species in all examined experimental conditions. Additionally, the experimental values of Ea for the thermal degradation of polysulfide species correlate with the observed stability of the individual species; i.e., S22- has the highest Ea, followed by S32-.

Adsorption studies of smithsonite flotation using dodecylamine and oleic acid

The interaction of various concentrations of sodium sulfide, dodecylamine (DDA) and oleic acid (OA) on smithsonite were investigated at different pH levels using zeta potential, contact angle, microflotation and diffuse-reflectance FT-IR studies. Flotation results show that the recovery and contact angle are enhanced to 94% and 115°, respectively, with a dodecylamine concentration of 1.6 × 10t−3 M and a pH of 11.5. The optimum sodium sulfide consumption was found to be 2.6 × 10−2 M. Zeta potential measurements showed less negative charge after DDA treatment on the surface of pure crystalline smithsonite. The recovery and contact angle for oleic acid flotation rises to 93% and 105°, respectively, with an oleic acid concentration of 1.1 × 10−3 M and a pH of 10. The zeta potential in the case of using oleic acid showed a more negative charge after oleic acid treatment on the smithsonite surface. The FT-IR spectra studies of smithsonite conditioned with DDA confirmed the adsorption of DDA on the smithsonite surface. The spectra show that the mineral surface is changed partially to a ZnS layer after sodium sulfide treatment. The spectra confirmed the formation of zinc oleate on the smithsonite surface after oleic acid treatment. A comparison of the results using cationic and anionic collectors showed that the different adsorption densities of the reagents in two cases conferred different degrees of hydrophobicity on the smithsonite surface.

Generating gas flows with a constant trace concentration of hydrogen sulfide

The dynamic gas extraction of hydrogen sulfide from aqueous solutions of sodium sulfide was studied theoretically and experimentally. The effects of the number of bubblers, the concentration of sodium sulfide, and the pH of solution on the concentration of hydrogen sulfide in the generated gas flow were found. The proposed method for generating gas flows with a constant trace concentration of hydrogen sulfide can be used for calibrating the verifying instruments for gas analysis.

Effects of sodium sulfide on burrowing activity of Capitella sp. I and bacterial respiratory activity in seawater soft-agar microcosms

We applied the seawater soft-agar microcosm approach in order to reveal the effects of sodium sulfide on burrowing activity of Capitella sp. I and on bacterial respiratory activity on mucus-lined burrow. The presence of sodium sulfide up to 7 mM in the soft-agar was not detrimental to the burrowing activity and the survival of the worms, but seemed to enhance the secretion of mucus from the worms. Addition of INT into overlying water (0.01% v/v) of the soft-agar microcosms containing the same concentrations of sodium sulfide caused intensive deposition of INT-formazan in the water, on the mucus over soft-agar surface and on the burrow lining. Both image analyses and spectrophotometric determination of the red-color INT-formazan showed a marked increase in the presence of 3.5 mM sulfide. From these results, we concluded that sulfide can promote burrowing activity of Capitella sp. I and thus enhance the bacterial respiratory activity on the burrow lining. These findings will help clarify the possible interaction between Capitella worms and sulfur-oxidizing bacteria in organically-enriched, sulfide rich sediment in natural environments.

Bacteriochlorophyll-c Homolog Composition in Green Sulfur Photosynthetic Bacterium Chlorobium vibrioformeDependent on the Concentration of Sodium Sulfide in Liquid Cultures

Green sulfur photosynthetic bacteria Chlorobium (Chl.) vibrioforme (DSM 263 strain and NCIB 8327 substrain possessing BChl-c) and Chl. tepidum (ATCC 49652) were photoautotrophically grown in liquid cultures containing different concentrations of sodium sulfide (Na2S). BChl-c homologs possessing a methyl group at the 12-position tended to increase in cells of the two strains of Chl. vibrioforme cultured under high Na2S concentrations. In contrast, the Na2S concentration in liquid cultures did not affect the relative composition of BChl-c homologs in Chl. tepidum. 8-Propyl-12-methyl([P,M])-BChl-c homolog, which has been little observed in usual cultivations, could be isolated by reverse-phase high-performance liquid chromatography from the cells of Chl. vibrioforme grown under high Na2S contents. The [P,M]-BChl-c homolog has the R-configuration at the 3(1)-position, which was determined by 1H-NMR analyses.

Anglesite flotation: a study for lead recovery from zinc leach residue

The recovery of lead from zinc leach residues (as PbSO 4) by flotation is of interest in the zinc plants. Therefore, at the first stage of the present study, anglesite flotation behavior and its surface characteristics have been investigated. The interaction of natural and sulfidized anglesite with potassium amyl xanthate (KAX), Aerofloat and Aerophine have been investigated as a function of concentrations of amyl xanthate, Aerofloat, Aerophine, and sodium sulphide as well as pH through micro-flotation studies. Flotation recovery is affected by pH, collector concentration, and sulfidization degree. Sulfidization reduced the collector consumption roughly 8 times for the collectors studied. At the second stage, the recovery of lead from a zinc leach residue of an oxidic ore was investigated through batch flotation studies. The residue was leached with water before sulfidization to eliminate its soluble compounds. The highest zinc elimination occurred at low pH. At the sulfidization-flotation stage, the effect of different parameters such as sodium sulfide, KAX, and sodium silicate concentration as well as pH were studied. The lead recovery was significantly affected by the sodium sulfide concentration. The sulfide consumption for the leach residue was 3 times more than that for the pure anglesite. De-sliming and cleaning increased the grade of lead in the concentrate.

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

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.

Electrochemical interaction between silver and sulfur in sodium sulfide solutions

Corrosion of silver and gold in sulfur-containing environments has been an industrial problem. The current study is concerned with the corrosion reaction behavior of silver in sodium sulfide solutions. An electrochemical investigation of silver corrosion has been carried out using a potentiostat, and the resulting corrosion products have been identified with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The effect of a concentration of sodium sulfide, pH, temperature, and electrical potential on the corrosion behavior of silver was investigated using Tafel plots and potentiodynamic polarization. The corrosion products under the conditions studied were found to be mainly silver sulfide and occasionally silver oxide. The corrosion rate was found to be positively influenced by both the pH of the solution and the concentration of sodium sulfide.

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

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) 4NBr) 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.

Spectrophotometric determination of nitrite and nitrate using phosphomolybdenum blue complex

A method for spectrophotometric determination of nitrite and nitrate is described. This method is based on the reduction of phosphomolybdic acid to phosphomolybdenum blue complex by sodium sulfide. The obtained phosphomolybdenum blue complex is oxidized by the addition of nitrite and this causes a reduction in intensity of the blue color. The absolute decrease in the absorbance of the blue color or the rate of its decrease is found to be directly proportional to the amount of nitrite added. The absorbance of the phosphomolybdenum blue complex is monitored spectrophotometrically at 814 nm and related to the concentration of nitrite present. The effect of different factors such as acidity, stability of the complex, time, temperature, phosphate concentration, molybdenum concentration, sodium sulfide concentration and the tolerance amount of other ions have been reported. Maximum absorbance is at 814 nm. The range of linearity using the conventional method is 0.5–2.0 ppm with molar absorptivity of 1.1×10 4 l mol −1 cm −1. and a relative standard deviation of 2.6% for five measurements. The range of linearity using the reaction rate method is 0.2–3.6 ppm with a relative standard deviation of 2.4% for five measurements. The method is applied for determination of nitrite and nitrate in water, meat products and vegetables.

Heavy metals removal by chemical coagulation and precipitation

Synthetic wastewater of pH 1.9, consisted of Zn, Cd, Mn and Mg at concentrations of 450, 150, 1,085 and 3,154 mg/l respectively. It was found that the optimum pH for chemical coagulation and precipitation by lime treatment was more than 9.5, which could decrease the concentration of heavy metals pertinent to the Wastewater Standard of the Ministry of Industry. Moreover, if 0.5 mg/l of polymer was added, it could decrease the concentration of heavy metals further. In addition when sodium sulphide solution was used in secondary treatment, it was also found that the optimum pH by lime in primary treatent was more than 9.5 and the optimum concentration of sodium sulphide was more than 250 mg/l.

Heavy metals removal by chemical coagulation and precipitation

Synthetic wastewater of pH 1.9, consisted of Zn, Cd, Mn and Mg at concentrations of 450, 150, 1,085 and 3,154 mg/1 respectively. It was found that the optimum pH for chemical coagulation and precipitation by lime treatment was more than 9.5, which could decrease the concentration of heavy metals pertinent to the Wastewater Standard of the Ministry of Industry. Moreover, if 0.5 mg/l of polymer was added, it could decrease the concentration of heavy metals further. In addition when sodium sulphide solution was used in secondary treatment, it was also found that the optimum pH by lime in primary treatment was more than 9.5 and the optimum concentration of sodium sulphide was more than 250 mg/l.

INHIBITION OF RESPIRATORY AND BIOENERGETIC MECHANISMS BY HYDROGEN SULFIDE IN MAMMALIAN BRAIN

The biochemical effects of hydrogen sulfide were investigated by treating enzyme homogenates and synaptosomes prepared from mammalian brain with sodium sulfide. Brain cytochrome c oxidase activity was highly sensitive to inhibition by sodium sulfide, as demonstrated by an IC50 of 0.13 muM. Sodium sulfide was also found to inhibit carbonic anhydrase activity in cerebellum, frontal cortex, and hippocampus. Synaptosomal oxygen consumption was significantly reduced as the concentration of sodium sulfide was increased from 20 to 100 muM; this was accompanied by a concentration-dependent depolarization of the synaptosomal mitochondrial membrane in situ and a reduction in synaptosomal ATP concentration. In other experiments using synaptosomes, sodium sulfide caused a significant calcium-independent increase in the extracellular accumulation of L-glutamate, inhibited Na+-dependent uptake of [3H]glutamate, but was unable to influence intrasynaptosomal free ionic Ca2+. Parallel studies conducted in vivo showed that rats exposed over a 5-d period to hydrogen sulfide (100 ppm for 3 h/d) had significantly higher concentrations of L-glutamate in the hippocampus compared to control animals. In summary, our results indicate that sulfide causes extensive disruption to respiratory and related mitochondrial functions in mammalian brain in vitro. The reduced capacity of nerve endings to take up L-glutamate may contribute to the raised L-glutamate levels observed in vivo.

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

Study of anthraquinone reaction with sodium sulphide

The reduction of anthraquinone (AQ) with sodium sulphide in alkaline medium has been studied by measuring conversion as a function of time at various temperatures, sodium sulphide concentrations, initial radii of anthraquinone particles and sodium hydroxide concentrations. The reduced product is the disodium salt of 9,10-dihydroxyanthracene. The kinetic data were fitted to the isothermal shrinking core model (SCM) for cylindrical particles without porous solid product layer formation. The results indicate that the surface chemical reaction is the controlling step of the overall process rate. AQ reduction is of first order with respect to sodium sulphide concentration. The activation energy was obtained from the Arrhenius law and was found to be 68.81 kJ mol −1 for the investigated temperature range.

Absorption of iron by dentin: its role in discoloration.

This study investigated the effect of iron-containing mordants on the discoloration of human dentin. Dentin wafers with intact enamel borders were treated with one of several acid solutions containing iron. After exposure to aqueous sodium sulfide, color change was evaluated colorimetrically. X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectrometry (EDS) were used to probe surfaces for the presence of iron. Changes in surface morphology were evaluated by scanning electron microscopy (SEM). The results indicated that dentin treated by iron-containing solutions always discolored when the sodium-sulfide concentration exceeded 9.7 mM; variability in discoloration occurred below this level. XPS detected iron in enamel but not in dentin, while EDS detected iron in both enamel and dentin. Since XPS probes the upper atomic layers, these results indicate that acid-demineralized dentin absorbs iron; however, a water wash removes iron from the uppermost dentin surface, suggesting that the iron is physically absorbed. When exposed to sodium sulfide, at least some of the iron remaining in the bulk region is able to migrate to the surface to form iron-sulfide compounds. Based on SEM findings, discoloration is associated with the formation of a surface film on dentin.