Sulfide Solution Research Articles

Selective leaching of antimony from tetrahedrite rich concentrate using alkaline sulfide solution with experimental design: Optimization and kinetic studies

Antimony dissolution from tetrahedrite concentrate obtained from froth flotation experiments was investigated with Na2S-NaOH as lixiviant agent. Min. Run Res. V and CCD methods were applied for the first time, to identify and optimize the effects of Na2S concentration, NaOH concentration, stirring speed, leaching time, temperature and solid percent on antimony recovery. Temperature was identified as a key factor for antimony dissolution while stirring speed and Na2S concentration slightly affected it. Kinetic studies demonstrated that antimony dissolution data fit well to the chemically controlled shrinking core model ([1−(1−α)13]=7.95×105×exp(−61.94RT)×t) with Ea=61.94 kJ.mol.−1, A=7.95 × 105 min.−1 and R2=95.65%. Maximum antimony recovery was obtained 29.52% under optimal conditions as: stirring speed of 495.8 rpm, Na2S concentration of 151.52 g/l, leaching temperature of 89.92 ○C, solid percent of 0.3%, leaching time of 60 min and NaOH concentration of 60 g/l. Moreover, leaching residue observations proved the formation of insoluble covellite and chalcocite minerals during antimony dissolution.

Real-time humidity sensing by integration of copper sulfide nanocomposite with low-cost and wireless Arduino platform

In this study, the (copper sulfide)-carrageenan nanocomposite was grown from the interface of gel (Cu-complexed carrageenan) and liquid (sulfide solution). The thin film of the nanocomposite was coated on a platinum interdigitated electrode in order to be used as a relative humidity (RH) sensor. Data from the sensor was acquired by the low-cost, wireless and portable data acquisition hardware (DAQ) device built from the Arduino and 16-bit analog-to-digital converter. The LabVIEW VI was programmed to plot and save voltage output received from the prototype through Bluetooth communication. The sensor responses to RH variation were compared simultaneously with a reference sensor installed in the same prototype, which allows a real-time data acquisition of high accuracy. Importantly, the sensor exhibited a high reversibility as well as a linear response towards RH between 8% and 80 %.

Модификация электронных свойств поверхности n-InP(100) сульфидными растворами

Photoluminescence and Raman spectroscopy are used to study the electronic properties of n-InP(100) surfaces passivated with different sulfide solutions. Such a passivation results in the increase in photoluminescence intensity of the semiconductor evidencing for the reduction in the surface recombination velocity. The increase in the photoluminescence intensity is accompanied by the narrowing of the surface depletion layer, as well as by the increase of the electron density in the probed volume of InP. The efficiency of electronic passivation of the n-InP(100) surface depends on the composition of the sulfide solution.

Оптические и электронные свойства пассивированных поверхностей InP(001)

The effect of chemical passivation in solutions of ammonium sulfide (NH4)2S on the optical and electronic properties of the n-InP (001) surface has been studied. It has been shown that treatment in a 4% aqueous solution of (NH4)2S leads to a decrease of surface band bending and localized charges in near-surface region in the 2 times. Processing in a 4% alcoholic solution of (NH4)2S leads to a decrease in these parameters in 3 times, and moreover, the barrier photovoltage and also reduces in three times.

A facile photochemical strategy for the synthesis of high-performance amorphous MoS2 nanoparticles.

It is difficult to avoid the formation of polysulfides by traditional chemical methods, and the synthesis of high purity amorphous MoS2 nanomaterials under ambient conditions is still a challenging task. Here we present a new and facile photochemical strategy for the synthesis of amorphous MoS2 nanomaterials, which is achieved by irradiating a mixed solution containing ammonium molybdate, formic acid and sodium sulfide simply with a Xe lamp for 3 min. The mechanism study reveals that the key step in this synthesis is the photolysis of formic acid to produce free radicals which can rapidly reduce Mo6+ to Mo4+, which then combines with S2− to form MoS2 and inhibits the formation of S–S2− by preventing S2− from participating in the reduction reaction. In addition, the results of a series of experiments indicate that the as-prepared amorphous MoS2 features a small particle size, uniform morphology and relatively large specific surface area, and shows excellent performance in the removal of inorganic heavy metal ions (mercury, lead and cadmium ions) and organic pollutants (rhodamine B and tetracycline), catalase catalysis and a lithium battery anode, showing its great potential and broad application prospects in the fields of environmental remediation, clean energy and green catalysis.

Development of Technology of Arsenic Removal from Acidic Waste Solutions in the Form of Arsenic Trisulfide

During the laboratory tests the conditions of arsenic removal from acidic waste solutions of metallurgical enterprise in the form of arsenic trisulfide were determined. The technology based on the reduction of pentavalent arsenic to trivalent state with sodium pyrosulfite solution and following arsenic trisulfide precipitation from acidic solution after treatment with sodium sulfide solution was proposed. The arsenic removal proceeds with mechanical stirring, dosing the calculated amounts of reagents and collecting emissions of hydrogen sulfide. With such treatment, about 95% of arsenic, which was in the initial solution, passes into the precipitate. An enlarged laboratory experiment was carried out and the precipitate with 42.6% of arsenic and 46.9% of sulfur was obtained. The precipitate yield was ∼25.7 kg (dry weight) out of 1 m3 of the initial arsenic containing solution.
 Keywords: arsenic, arsenic trisulfide, acidic waste solutions, sodium sulfide, sodium pyrosulfite

Selective extraction and separation of Li, Co and Mn from leach liquor of discarded lithium ion batteries (LIBs)

Novel route has been developed to selectively extract lithium (Li), cobalt (Co) and manganese (Mn) from the leach liquor of discarded lithium ion batteries (LIBs) containing 1.4 g/L Cu, 1.1 g/L Ni, 11.9 g/L Co, 6.9 g/L Mn and 1.2 g/L Li. Initially, Cu and Ni were extracted by solvent extraction techniques using 10% LIX 84-IC at equilibrium (Eq.) pH 3 and 4.6, respectively. Subsequently, precipitation studies were carried out at different conditions such as pH, reaction time, precipitant concentration etc., to optimize the parameters for selective precipitation of Co from the leach liquor. Result showed that 99.2% Co was precipitated from the leach liquor (11.9 g/L Co, 6.9 g/L Mn and 1.2 g/L Li) after extraction of Cu and Ni in a range of pH 2.9 to 3.1 using un-diluted ammonium sulfide solution (10% v/v) as a precipitant at 30 °C, while only 0.89% Mn and 0.62% Li were co-precipitated. After Co precipitation, 98.9% Mn was extracted from the filtrate using 10% D2EHPA at equilibrium pH 4.5, and Li remained in raffinate. From the obtained purified solution, metals could be recovered either in a form of salt/metals by precipitation/ evaporation/ electrolysis method.

Copper Thiocyanate as an Anode Interfacial Layer for Efficient Near-Infrared Organic Photodetector

Interfacial modification between the electrode and the overlying organic layer has significant effects on the charge injection and collection and thus the device performance of organic photodetectors. Here, we used copper(I) thiocyanate (CuSCN) as the anode interfacial layer for organic photodetector, which was inserted between the anode and an organic light-sensitive layer. The CuSCN layer processed with ethyl sulfide solution presented similar optical properties to the extensively used anode interlayer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), while the relatively shallow conduction band of CuSCN resulted in a much higher electron-injection barrier from the anode and shunt resistance than those of PEDOT:PSS. Moreover, the CuSCN-based device also exhibited an increased depletion width for the PEDOT:PSS-based device, as indicated by the Mott-Schottky analysis. These features lead to the dramatically reduced dark current density of 2.7 × 10-10 A cm-2 and an impressively high specific detectivity of 4.4 × 1013 cm Hz1/2 W-1 under -0.1 V bias and a working wavelength of 870 nm. These findings demonstrated the great potential of using CuSCN as an anode interfacial layer for developing high-performance near-infrared organic photodetectors.

Synthesis and Characterization of (Ag2S)x(ZnS) Heteronanostructures

(Ag2S)x(ZnS) heteronanostructures were synthesized by two-stage chemical codeposition of silver and zinc sulfides using aqueous solutions of zinc nitrate, silver nitrate, sodium sulfide, trisodium citrate and Trilon B. Prepared heteronanostructures were characterized for phase composition and nanoparticles size using X-ray diffraction and the high-resolution transmission electron microscopy. The size of Ag2S nanoparticles in the obtained heteronanostructures depends on the ratios of reagent concentrations and ranges from 9 to 30 nm, the size of ZnS nanoparticles is equal to 4-5 nm.

Photoluminescence of n-InP (100) surface passivated with aqueous Na2S solution

Passivation of the n-InP(100) surface with an aqueous solution of sodium sulphide (Na2S) has been investigated by spectroscopic photoluminescence (PL). After sulphide treatment the PL signal intensity of InP increased significantly and this increase is dependent on duration of sulphide passivation. The correlation of the increase in the PL intensity after sulphide treatment with the variation of the solution pH in contact with InP(100) surface has been established, that expect the possibility for optimization of the passivation process by monitoring the change of the solution pH value in the course of sulphide treatment of the semiconductor.

Sulfide Passivation of InP(100) Surface

Passivation of the n-InP(100) surface with sodium sulfide (Na2S) aqueous solution is analyzed by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The room-temperature PL intensity increases essentially even after short treatment with sulfide solution for 1 min. The enhancement in the room-temperature PL intensity after passivation decreases with the increase in the bulk doping level of the semiconductor. Time-resolved PL studies performed at liquid-nitrogen temperature indicate reduction in the surface recombination velocity. This improvement of the PL intensity occurs just after transformation of the native oxide layer consisting mainly of indium phosphates to the passivating layer consisting of indium sulfides and oxides. The surface bands in n-InP(100) remained nearly flat both before and after sulfide passivation.

(Invited) Integrated Green Engineering Process for Simultaneous Hydrogen Production and Fertigation

The constant utilization of hydrocarbon-based fuels such as petroleum, coal, and natural Gas has resulted in the detection of high concentration levels of sulfur containing gases in the atmosphere of many countries, including Qatar. Among those potential air pollutants, the rising concentrations of H2S and SO2 are of serious concern. In this work, sulfur-based seed solutions (SBSSs) such as sulfite or sulfide solutions are made by purging sulfur-containing gases released from industry into alkaline solutions. These SBSS solutions are simultaneously utilized towards the production of renewable hydrogen energy via a photoelectrochemical (PEC) process, and are used as draw solutions (DS) to produce diluted fertilizer water by a forward osmosis (FO) desalination process for agricultural irrigation purposes. The continuous bench scale of the integrated PEC-FDFO system was successfully demonstrated for simultaneous hydrogen production and dilution of SBSS DS. The experimental results showed that the reduction potential of SBSS DS in the PEC cell changes with variation of SBSS DS concentration and pH. This resulted in the continuous oxidation of sulfite into sulfate and led to more hydrogen production. Moreover, FDFO process exhibited high percentage of water recovery and DS dilution up to 80% and 68% at high SBSS DS concentration, respectively. In binary mixture of SBSS DS, increasing the concentration of ammonium sulfate (NH4)2SO4 led to high water flux to about 42%. The outcomes of this experimental study showed a successful practical continuous integrated system toward hydrogen production and fertigation.

Carbonaceous Adsorbent Derived from Sulfur-Impregnated Heavy Oil Ash and Its Lead Removal Ability from Aqueous Solution

A novel carbonaceous adsorbent was prepared from sulfur-impregnated heavy oil ash via pyrolysis using potassium sulfide (K2S) solution, and its ability to remove lead (Pb2+) from aqueous solutions was examined. It was compared with an adsorbent synthesized by conventional pyrolysis using potassium hydroxide (KOH) solution. Specifically, the raw ash was immersed in 1 M K2S solution or 1 M KOH solution for 1 day and subsequently heated at 100–1000 °C in a nitrogen (N2) atmosphere. After heating for 1 h, the solid was naturally cooled in N2 atmosphere, and subsequently washed and dried to yield the product. Regardless of the pyrolysis temperature, the product generated using K2S (Product-K2S) has a higher sulfur content than that obtained using KOH (Product-KOH). Moreover, Product-K2S has a higher lead removal ability than Product-KOH, whereas the specific surface area of the former is smaller than that of the latter. Product-K2S obtained at 300 °C (Product-K2S-300) achieves the highest lead adsorption and a high selective lead removal from a ternary Pb2+–Cu2+–Zn2+ solution. The equilibrium capacity of Product-K2S-300 was found to fit the Langmuir model better than the Freundlich model, and its calculated maximum adsorption capacity is 0.54 mmol/g. From the ternary Pb2+–Cu2+–Zn2+ solution, the order of adsorption by Product-K2S-300 is Pb2+ > Cu2+ > Zn2+, and the removal of Pb2+ and Cu2+ increases as the pH of the solution increases.

The solubility of cooperite PtS(cr) at 25 – 450 °C, Psat – 1000 bar and hydrosulfide complexing of platinum in hydrothermal fluids

The solubility of cooperite PtS(cr) was measured in aqueous sulfide solutions at 25 °C/1 bar, 75 °C/1 bar, and 450 °C/1000 bar. The concentration of Pt increases with an increase of temperature from 10–10.2 to 10–7.4m (mol⋅(kg H2O)−1) in solutions which contain 0.06–0.07 m of total reduced sulfur. The experimental solubility data are accurately described by the reactionsPtScr+H2S˚aq=PtHS2˚aqKs˚PtHS2.PtScr+2H2S˚aq=PtHS3−+H+Ks˚PtHS3−..The charged complex Pt(HS)3− dominates in low-temperature near-neutral solutions but was not detected at 450 °C where the only hydrosulfide complex was Pt(HS)2°(aq). The effect of NaCl on the PtS(cr) solubility is negligible which implies that mixed Pt-HS-Cl complexes can be neglected. The PtS(cr) solubility constant, Ks°(Pt(HS)2), was determined as log Ks° = −9.09 ± 0.17 (25 °C/1 bar), −9.50 ± 0.35 (75 °C/1 bar), and − 6.68 ± 0.10 (450 °C/1000 bar). The PtS(cr) solubility constant, Ks°(Pt(HS)3−), was determined as log Ks° = −14.43 ± 0.31 (25 °C/1 bar), and − 13.15 ± 0.23 (75 °C/1 bar). The PtS(cr) solubility constants together with the literature data were fitted to a simple density modellogKSoPtHS2o=−7.30−638.9∙TK−1−5.98∙logdwlogKSoPtHS3−=0.633−4522.6∙TK−1+43.03∙logdwwhere d(w) is the pure water density. The Ks°(Pt(HS)2) increases with an increase of temperature, but Ks°(Pt(HS)3−) has a maximum at ca. 200 °C. Accordingly, at higher temperatures the role of the latter complex decreases and its contribution to the dissolved Pt concentration becomes negligible at t > 300 °C. Thermodynamic calculations show that in natural hydrothermal fluids, which contain up to 0.1 m of total reduced sulfur, the concentration of Pt-HS complexes can reach a few ppb. Higher solubility of Pt-bearing minerals can be attained in chloride-bearing fluids due to the formation of PtCl42−, which plays the dominant role in high-temperature hydrothermal transport of Pt.

Cross-linked chitosan into graphene oxide-iron(III) oxide hydroxide as nano-biosorbent for Pd(II) and Cd(II) removal

In this study, chitosan cross-linked into graphene oxide/iron(III) oxide hydroxide nanocomposites. For this purpose, to a mixture of graphene oxide in deionized water was added to iron(II) sulfide and hydrogen peroxide solution. The pH was then adjusted. Then, chitosan dissolved in acetic acid was added. This compound applied as nano-biosorbent for the removal of Pd(II) and Cd(II) ions from aqueous solution. Nanocomposites were characterized by FT-IR, XRD, SEM, and EDX analysis. The effects of valid parameters such as pH (2–9), sorbent mass (0.01–0.1 g), temperature (25–60 °C), and contact time (20–50 min) were investigated in adsorption of Pd(II) and Cd(II) ions. The results showed that oxygen-containing functional groups on the surface of graphene oxide, iron(III) oxide hydroxide nanoparticles, and the abundant amino and hydroxyl functional groups of chitosan chain were shown excellent potential for Pd(II) and Cd(II) adsorption. The removal percentage of Pd(II) and Cd(II) were 84 and 95%, respectively. The Freundlich and Langmuir adsorption isotherms were investigated for the description of adsorption onto nanocomposites. However, the Freundlich model showed a higher correlation coefficient (R2) than Langmuir isotherm. The pseudo-second-order equation was the best fitted kinetic model for this process.

Enhancement of Ammonia Gas Sensing Properties of GaAs-Based Schottky Diodes Using Ammonium Sulfide Surface Passivation

In this work, enhancement of gas sensing characteristics of GaAs-based Schottky diode sensors passivated by ammonium sulfide are studied and demonstrated. The GaAs surface is passivated by saturated ammonium sulfide solution to remove its native oxide and reduction of surface state densities. The measurements indicate a significant improvement in electrical characteristics of Pt-Pd(alloy)/GaAs diode where the Schottky barrier height increases from 0.688 to 0.758eV after surface passivation. The Schottky diode with passivated GaAs surface exhibits a response of 63% upon exposure to 600ppm ammonia gas at a working temperature of 150°C, which is about 2.5 times higher than that of the non-passivated sensor. This noteworthy improvement is attributed to the decrement of metal-semiconductor interface states, preventing the Fermi level pinning. Furthermore, the response (recovery) times of 29 (138)s is obtained upon exposure to 600ppm ammonia at 150°C, showing a value of around 2 times lower than that for the non-passivated sensor.

О кинетике извлечения примесей из железного концентрата, полученного в ходе гидрометаллургической переработки чернового медного концентрата

The purpose of the paper is to study the physical and chemical features of high-quality iron concentrate precipitation from nitric acid leaching solutions of low-grade copper-sulfide raw materials, and to obtain a highly profitable product which is suitable for direct processing at ferrous metallurgy enterprises. To conduct the experiments on obtaining impurity rich and depleted iron concentrate a hydrolytic precipitate containing 54.6% iron and numerous impurities obtained as a result of processing of nitric acid leaching solutions of rough copper sulfide concentrate from the Zhezkazgan deposit is used. Analytical studies of initial materials and resulting products of the processes under investigation are conducted using the modern certified methods including the x-ray spectral, x-ray phase, atomic absorption analysis, mass spectrometry method with inductively coupled plasma. We have obtained a high-quality iron concentrate containing minimal amounts of silicon, aluminum, phosphorus and sulfur as well as partial and generalized equations that give an idea of the influence of the studied factors on the indicators of the iron concentrate production process. The apparent activation energy of the process has been calculated - 46.77 kJ/mol. It probably indicates the presence of diffusion complications caused by the formation of solid products passivating the surface of the material being dissolved. The principal possibility of obtaining high-quality iron concentrate from processing poor copper-sulfide concentrate middlings of the Zhezkazgan deposit is shown. The mathematical processing of experimental data has resulted in the determination of equations that characterize the degree of influence of the studied factors on the process indicators. It is found out that the production process of the saleable iron concentrate proceeds in the mode of diffusion restrictions. It is the first time, when multivariate generalized dependencies are obtained for the process under consideration and their analytical transformations are performed. These methods can be used to study the analogous processing of similar metallurgical raw materials.

Synthesis of Silver Sulfide Colloidal Solutions in Heavy Water D2O

It is for the first time that silver sulfide colloidal solutions were prepared by chemical deposition from silver nitrate and sodium sulfide solutions in heavy water D2O. Sodium citrate served as the stabilizer. The sizes of Ag2S nanoparticles in colloidal solutions were assessed by dynamic light scattering (DLS) measurements and electron microscopy. The silver sulfide nanoparticles in heavy water colloidal solutions prepared from batches having various reagent concentrations had sizes in the range from 3 to 19–20 nm. The increasing silver nitrate concentration and decreasing sodium citrate concentration in the batch only slightly increased the sizes of Ag2S nanoparticles in the prepared colloidal solutions. The silver sulfide colloidal solutions prepared with heavy water D2O retained their stability and unchanged nanoparticle sizes when stored for more than 100 days.

Термодинамическая вероятность образования твердых растворов FexPb1−xS гидрохимическим осаждением

Analysis of the literature showed that narrow-gap lead sulfide PbS (0.4 eV at 300 K), due to its unique properties, has found wide application in such devices as photodetectors with a wide (from infrared to ultraviolet) radiation range, solar energy converters, chemical sensors, temperature sensors, flame detectors, etc. Doping of lead sulfide with various metal ions can affect the bandgap, and hence expand the scope of its application. Of particular interest is the preparation of thin film solid solutions in the PbS – FeS system, which can lead to the appearance of ferromagnetism in lead sulfide. To obtain doped films of lead sulfide and solid solutions based on it, the method of chemical deposition from aqueous media is considered promising, which, in addition to its cost-effectiveness and simplicity of the process, allows one to determine in advance the areas of formation of the semiconducting metal chalcogenides of interest. The analysis of ionic equilibria in the systems "PbAc2 – FeCl2 – Na3Cit – NH4OH – N2H4CS", "PbAc2 – FeCl2 – NaAc – NH4OH – N2H4CS "and " PbAc2 – FeCl2 – Na2С2О4 – NH4OH – N2H4CS "made it possible to reveal predominantly forms of metals in a given pH range. To assess the conditions for the deposition of the main and impurity phases by thermodynamic calculations taking into account the sizes of critical nuclei, the boundary conditions and regions of the formation of FeS, PbS, Fe(OH)2, Pb(OH)2 in the reaction systems under study were found. It is shown that the most promising for the preparation of the three-component PbFeS compound, which does not contain impurity phases of lead and iron hydroxides, is the reaction system "PbAc2 – FeCl2 – Na3Cit – NH4OH – N2H4CS". The possibility of obtaining PbS: Fe films with a uniform iron distribution of ~ 0.5 at.% and deviation from stoichiometry towards Pb deficiency (47.7 at.%) and S excess (50.7 at.%) was experimentally demonstrated.

Multiscale modeling and control of pulp digester under fiber-to-fiber heterogeneity

In kraft pulp digester, lignin in wood chips is removed through delignification by hydroxide and sodium sulfide solution. Since both macroscopic and microscopic properties of wood pulp significantly affect the attributes of paper products, several multiscale modeling frameworks have been developed. However, these models did not consider fiber-to-fiber (F2F) heterogeneity; it is an important challenge these days as the fibers are provided from multiple sources to meet the increasing demand. Therefore, we developed a multiscale modeling framework to describe the evolution of heterogeneous fibers in a digester by running multiple kinetic Monte Carlo simulations in parallel. Specifically, the F2F heterogeneity is incorporated by introducing variation in heat capacity and dissolution rate for each fiber. Based on the developed multiscale model, we also designed an offset-free model predictive control system to regulate the cell wall thickness distribution of fibers as well as Kappa number in a pulping process.