Showing papers on "Sodium sulfide published in 2022"

Role of ammonium sulfate in sulfurization flotation of azurite: Inhibiting the formation of copper sulfide colloid and its mechanism

Abstract: In this study, the role of (NH 4 ) 2 SO 4 during the sulfurization of azurite and its response to flotation were investigated. The flotation results showed that adding (NH 4 ) 2 SO 4 prior to sulfurization decreased the formation of colloid in flotation pulp, and the floatability of the suppressed azurite caused by excess sodium sulfide was restored. After adding (NH 4 ) 2 SO 4 prior to sulfurization, the formation of Cu(NH 3 ) n 2+ intermediate products changed the path of the sulfurization reaction, which slowed the direct impact of HS − on the azurite surface. The nucleation rate was reduced, and the growth of copper sulfide crystal was improved. Covellite (syn, CuS) with larger crystal grains was formed on the azurite surface, thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface. Therefore, the generated copper sulfide colloid significantly reduced, ultimately promoting the effective adsorption of xanthate on the azurite surface.

Recovery of copper, zinc and lead from photovoltaic panel residue

Abstract: The increase in photovoltaic panel installations in Europe will generate vast amounts of waste in the near future. Therefore, it is important to develop new technologies that allow the recycling of end-of-life photovoltaic panels. This material can serve as a secondary resource, not only for precious metals (e.g. silver), but also for base metals. In this work, the extraction and recovery of the base metals copper, zinc and lead from a copper-rich photovoltaic panel residue was investigated. The material was first leached at 80 °C under microwave irradiation with a mixture of hydrochloric acid, sodium chloride and hydrogen peroxide solutions. Based on the Box–Behnken factorial design optimization, it was possible to extract 81.2% of Cu, 96.4% of Zn and 77.6% of Pb, under the following leaching conditions: [HCl] = 0.5 mol L−1, [NaCl] = 200 g L−1, [H2O2] = 7.5 wt% and t = 60 min. Cementation with iron powder at a 1.2 iron-to-copper stoichiometric ratio allowed the recovery of copper nearly quantitatively (99.8%) as a copper–iron sediment. The gas–liquid separation technique of ion flotation was employed to separate lead and zinc from the dilute copper-free leachate. Cetyltrimethylammonium bromide (CTAB), a cationic surfactant, selectively recovered lead (99.4%) over zinc as lead(ii) tetrachloro cetyltrimethylammonium colloid, after eight ion flotation stages and [CTAB]total = 7.2 mmol L−1. The zinc that remained in the solution after the ion flotation step was recovered by precipitation and by adding sodium sulfide at 110% of the stoichiometric amount after removing iron as ferric hydroxide by slowly raising the pH to 3.7.

Application of Biogenic Thiosulfate Produced by Methylophaga sulfidovorans for Sustainable Gold Extraction

Abstract: Thiosulfate is an alternative lixiviant that eliminates many environmental and social drawbacks of cyanide leaching used by most gold operations. Biogenic thiosulfate (Bio-TS) was produced by the bacterium Methylophaga sulfidovorans with sodium sulfide as a substrate and used to leach gold powder and gold from an oxide ore. Growth curve studies were used to determine the growth conditions of the bacteria in batch flask conditions regarding pH and inoculum load. The effect of sulfide dosage and addition time on Bio-TS concentration was studied. The optimal conditions for the growth and generation of Bio-TS were determined to be pH 7–8, 30 °C, and in the environment of a sealed flask rotating in a high salinity medium. Production of Bio-TS from sodium sulfide was confirmed by iodometric titration and IC/UV–vis methods. Gold was leached with a maximum extraction efficiency of 61.9% from ore after 24 h at a 10% pulp density, 0.1 L/min air, and 50 °C. Sustainable indicators and green metrics were combined for multicriteria analysis to quantify the sustainability of this novel proposed method relative to cyanidation and thiosulfate gold leaching processes.

Exploration of Sulfur-Containing Nanoparticles: Synthesis, Microstructure Analysis, and Sensing Potential.

Abstract: In this work, three different sulfur sources such as sulfur powder, sodium sulfide, and sodium thiosulfate are selected to prepare sulfur-derived quantum dots (S-QDs), Na2S-derived nanoparticles (NS-NPs), and Na2S2O3--derived QDs (NSO-QDs) in the presence of NaOH or assisted by hydrogen peroxide etching. The low sulfur percentage in the above three samples and the synthesis experiments in the presence of nitrogen/oxygen all support that poly(ethylene glycol) (PEG) plays an important role during the assembly process and the definition of sulfur dots is not accurate. For photophysical features, remarkable green quantum dots (S-QDs) possess an excitation-independent emission peak at 500 nm. But NS-NPs and NSO-QDs demonstrate observable shift tendency, and the evolution of emission profiles varies from 480 to 586 nm. NSO-QDs can be used as a fluorescent probe for highly selective and quantitative detection of Ni2+ in an aqueous solution in the presence of potential interfering ions with a low detection limit (0.18 μM) and a wide linear range (8-380 μM). Their reusability performance has also been demonstrated by employing dimethylglyoxime as the restoration reagent.

Flotation behavior of a complex lead-zinc ore using individual collectors and its blends for lead sulfide

Abstract: Abstract The effect of the collector and its blends on sequential flotation of a complex lead-zinc ore has been investigated. Lead-zinc ore collected from Rajasthan, India showed the presence of PbS-2.21%, ZnS-5.92%, FeS2-8.03%, SiO2-20.21%, Al2O3-5.25%, MgO-10.53%, SO3-6.48% and CaO-22.16%. The copper and silver were also traced as minor fractions. Xanthates of different alkyl chain lengths as a collector (individual or mixture in various proportions) were used in the lead circuit to evaluate valuables’ performance in the mineralized pulp. The study could enhance the lead and zinc grade up to 27.95% and 22.6% using PEX (potassium ethyl xanthate) and SIPX (sodium isopropyl xanthate) as a blend. The best overall performance in the recovery of lead and zinc was 74.39% and 82.23%, respectively. However, the studies carried out with individual collectors, PEX and SIPX, showed their best result: 22.06% lead and 20.99% zinc grade, 60.54% lead, and 78.73% zinc recovery. The study confirms the synergies between the two alkyl chain length xanthates in the blend. GRAPHICAL ABSTRACT

Homocouplings of Sodium Arenesulfinates: Selective Access to Symmetric Diaryl Sulfides and Diaryl Disulfides

Abstract: Symmetrical diaryl sulfides and diaryl disulfides have been efficiently and selectively constructed via the homocoupling of sodium arenesulfinates. The selectivity of products relied on the different reaction systems: symmetrical diaryl sulfides were predominately obtained under the Pd(OAc)2 catalysis, whereas symmetrical diaryl sulfides were exclusively yielded in the presence of the reductive Fe/HCl system.

Biogenic Production of Thiosulfate from Organic and Inorganic Sulfur Substrates for Application to Gold Leaching

Abstract: Gold mining and processing is an activity with large environmental impact due to the low concentration of gold in ore deposits and chemical resistance to most chemicals. Over 75% of gold is leached from ores using cyanide, however less toxic lixiviants have been proposed in the literature. Thiosulfate is one of these alternative reagents, but high reagent consumption has slowed acceptance in mining operations. Reducing the cost and impact of thiosulfate production is a way to reduce the cost of reagent consumption during leaching. The objective of this study was to evaluate the feasibility of leaching gold from ore with biogenic thiosulfate. Biogenic thiosulfate was produced using a marine methylotroph bacterium from three substrates: sodium sulfide, elemental sulfur, and dimethyl sulfide for application in bioleaching. The different substrates were evaluated to determine conversion efficiency from the sulfur source to biogenic thiosulfate and verified by titration and ion chromatography. Optimal conditions for conversion to thiosulfate were determined to be in the range of pH = 7–8, 25–30 °C, with sodium sulfide as a substrate in a sealed system to prevent sulfide from escaping as hydrogen sulfide gas. An oxide gold ore with a grade of 4.02 g/t was selected as a gold source for leaching experiments. The leaching of gold using the biogenic thiosulfate was compared with chemical thiosulfate solutions under experimental conditions of pH = 9.5, 50 mg/L copper, 500 RPM mixing, and 0.1 L/min air. The efficiency of gold bioleaching was measured using flame atomic absorption spectroscopy and fire assay. Gold extraction efficiencies ranging from 20–60% were achieved using the biogenic thiosulfate, and 27–77% with sodium thiosulfate solutions, respectively. It was concluded that the sodium sulfide substrate was best for producing higher biogenic thiosulfate concentrations and leaching efficiency.

Statistical Study of Extract Keratin Protein from Waste Chicken Feather Based on Response Surface Methodology

Abstract: The feathers contain a significant amount of keratin protein, which is used in cosmetics, shampoos, hair treatment creams, and skin creams. Dissolving chicken feathers with reducing agent and then separating the protein from chemicals are the key steps involved. However, in order to enhance the amount of recovered keratin as much as possible, the best conditions for extracting keratin from chicken feathers are required. In this study, Response Surface Methodology (RSM) was used in order to simulate and optimize the operating parameters for extracting keratin from waste chicken feathers in order to increase the amount of keratin protein compared to previous studies. Dissolving chicken feathers using sodium sulphide as a reducing agent at various periods, temperatures, and concentrations is the first step in the fundamental technique. After the feathers have been dissolved with a reducing agent, the fluid is treated with an ammonium sulfate solution to precipitate the protein. As determined by a biuret test and UV-Vis analysis, the keratin protein had a maximum wavelength of 290 nm. Finally, the statistical optimization of the extraction conditions provided a better understanding of the reaction parameters. The optimum yield of keratin was achieved at 3.7 hours at 30.07°C with 0.05 M sodium sulfide.

Sodium sulfide-promoted reaction of 2-aminobenzamide and benzyl alcohols with elemental sulfur: a novel approach with 2-aryl-quinazolin-4(3h)

Abstract: Six derivatives containing benzoxazole were synthesized from phydroxybenzaldehyde via four step-route in high yields. The benzoxazole cyclization step was promoted with microwave irradiation for 10 to 30 min. Free oaminophenol derivative A3 reacted with aldehydes to form benzoxazole A4a-f, but A3.HCl couldn’t due to the presence of iron (II). Their structures were elucidated with spectroscopic methods: IR, 1D, 2D NMR, and MS.

Effect of Ammonium Sulfide on Sulfidization Flotation of Malachite

Abstract: Recently, several studies have shown the positive effect of sulfidization flotation on malachite surfaces and its enhancing methods. Therefore, this paper was focused on the effect of ammonium sulfide and sodium sulfide on the sulfidization of malachite, respectively; this was investigated using different devices such as the micro-flotation tests, Zeta potential measurements, ToF–SIMS, XPS analysis, and FTIR. Thus, Fourier transform infrared spectroscopy results demonstrated that a new characteristic peak of Cu-S bonds was formed and adsorbed on malachite surfaces at 1694 cm−1, as confirmed by XPS analysis. Notably, malachite with ammonium sulfide ions had a significantly higher flotation recovery than malachite with an excess of sodium sulfide ions, as concerns of sulfidization types. Conclusively, all the experiments in this study confirmed that additional copper sulfide products were formed on the malachite surface, increasing the hydrophobicity of the malachite.

Sodium sulfide-promoted reaction of 2-aminobenzamide and benzyl alcohols with elemental sulfur: a novel approach with 2-aryl-quinazolin-4(3h)

Abstract: A simple metal- and solvent-free method for the synthesis of 2-aryl- 4(3H)-quinazolinone derivatives from 2-aminobenzamide and benzyl alcohols in the presence of S8\DMSO as an oxidizing agent and promoted by Na2S.5H2O has been reported. Five 2-aryl-4(3H)-quinazolinone derivatives were synthesized with yields from 23% to 86%.

l -Proline-Catalyzed Three-Component Reaction of 4-Chloro-3-formylcoumarin, Sodium Sulfide, and α-Halo Ketones: A Direct Approach to Thieno[3,2- c ]coumarins

Abstract: A new protocol for the synthesis of thieno[3,2-c]coumarins is disclosed herein. Following this method, 3-formyl-2-oxo-2H-chromene-4-thiolate is in-situ generated by the combination of 4-chloro-3-formylcoumarin and sodium sulfide. This chromene-4-thiolate undergoes L-proline catalyzed substitution/Knoevenagel cascade with α-haloketone to afford the desired thieno coumarins in moderate to good isolated yields. The described protocol eliminates the need for stoichiometric amounts of inorganic bases and the use of foul smelling thiols. The reaction conditions tolerate a variety of α-haloketone.

Flotation studies of the middling product of lead-zinc ores with preliminary sulfidizing roasting of oxidized lead and zinc compounds

Abstract: The development of combined enrichment technologies becomes more significant due to the decreasing of the processed ores quality and involvement in the processing of poor, refractory ores. The difficulty in the flotation enrichment of mixed and oxidized polymetallic ores and intermediate products lies in the effective sulfidization of the surface of oxidized minerals. The sodium sulfide reagent used in flotation does not always provide complete sulfidization of the mineral surface. On the intermediate product of lead-zinc ores related to the phase composition of mixed ores, flotation studies were carried out on the original product and after preliminary sulfidization by the pyro-metallurgical method. It was found that in the pre-sulfidizied product, the extraction of zinc increased to 17.23 %, and lead to 10.07 %, compared with the original product without pre-treatment.

Surfactant-assisted preparation of Mo-Co-K sulfide catalysts for the synthesis of low-carbon alcohols via CO2 hydrogenation

Abstract: A series of Mo-Co-K sulfide catalysts were prepared with the assistance of different surfactants, and these catalysts were used in CO2 hydrogenation. It was found that the surfactant type had a significant impact on the properties and catalytic performance of these catalysts. When cetyl trimethyl ammonium bromide (CTAB, a cationic surfactant) was used in the synthesis, the steric hindrance effect of micelles and the electrostatic interaction between micelles and ions in the solution would reduce the number and length of MoS2-based layers in the catalyst, thus exposing more “edges” related to the active site. Moreover, CTAB, being a carbon source, was able to promote the generation of carbon species in the catalysts, beneficial for the adsorption of CO2 on the catalyst surface. Under the optimal conditions (320°C, 5.0 MPa, V(H2)/V(CO2) = 3, GHSV = 3000 ml•gcat−1•h−1), the catalyst showed a CO2 conversion of 26.9%, a total alcohol selectivity of 83.7% (excluding CO), and a C2+ alcohol selectivity of 17.7% (excluding CO). Sodium dodecyl benzene sulfonate (SDBS, an anionic surfactant) and polyvinyl pyrrolidone (PVP, a non-ionic surfactant) were also attempted for the preparation of Mo-Co-K sulfide catalysts for comparison.