Oxidation Of ZnS Research Articles

The Effects of Different Zn Forms on Sintering Basic Characteristics of Iron Ore.

The micro-sintering method was used to determine the sintering basic characteristics of iron ore with Zn contents from 0 to 4%, the influence mechanism of Zn on sintering basic characteristics of iron ore was clarified by means of thermodynamic analysis and first-principles calculations. The results showed that (1) increasing the ZnO and ZnFe2O4 content increased the lowest assimilation temperature (LAT) but decreased the index of liquid phase fluidity (ILF) of iron ore. The addition of ZnS had no obvious effect on LAT but increased the LIF of iron ore. (2) ZnO and ZnFe2O4 reacted with Fe2O3 and CaO, respectively, during sintering, which inhibited the formation of silico-ferrite of calcium and aluminum (SFCA). The addition of ZnS accelerated the decomposition of Fe2O3 in the N2 atmosphere; however, the high decomposition temperature limited the oxidation of ZnS, so the presence of ZnS had a slight inhibitory effect on the formation of SFCA. (3) The Zn concentrated in hematite or silicate and less distributed in SFCA and magnetite in the form of solid solution; meanwhile, the microhardness of the mineral phase decreased with the increase in Zn-containing solid solution content. As the adsorption of Zn on the SFCA crystal surface was more stable, the microhardness of SFCA decreased more. The decrease in microhardness and content of the SFCA bonding phase resulted in a decrease in the compressive strength of the sinter.

Advanced strategies for conversing and fixing sulfur during waste resins oxidation through Ca/Zn oxides enhanced Na2CO3-K2CO3 system

The effective reduction of sulfur pollutant emissions during the treatment of waste resins has always posed a challenge. This study put forward a solution to using the metallic oxide enhanced Na2CO3-K2CO3 system for the treatment of waste resins (CERs). Na2CO3-K2CO3 was used as a medium for heat transfer and desulfurization, while CaO or ZnO functioned as catalysts in the sulfur conversion process. The thermodynamic analysis substantiated the reliability of enhanced sulfur fixation by CaO and ZnO. H2S, SO2 and COS primarily generated during the destruction stage of -SO3H (280–500°C) and residues (∼700°C), which were largely absorbed through a vapor-liquid-solid reaction to generate CaCO3, ZnS and K2SO4. CaO improved the conversion of sulfur to sulfate and effectively mitigated the excessive emissions of CO2. SO2 generated by the oxidation of ZnS at about 800 °C could be further absorbed by molten Na2CO3-K2CO3 to form K2SO4. The proposed method exhibited in-situ desulfurization capability and effectively inhibited the sulfur migration to gaseous products. At 800°C, the sulfur retention rate, the formation rate of SO42- and the oxidation efficiency of CERs reached 91.39 %, 80.61 % and 99.99 %, respectively. The existence of CaO and ZnO facilitated the inorganic transformation of organic sulfur, and the efficient conversion of organic sulfur into inorganic compounds was achieved. This approach provides a new opportunity to improve the treatment efficiency of radioactive solid waste containing organic sulfur.

Excellent Charge Separation of NCQDs/ZnS Nanocomposites for the Promotion of Photocatalytic H2 Evolution.

Carbon Quantum dots (CQDs) are widely studied because of their good optical and electronic characteristics and because they can easily generate photocarriers. Nitrogen-doped CQDs (NCQDs) may exhibit improved hydrophilic, optical, and electron-transfer properties, which are conducive to photocatalytic hydrogen evolution. In this paper, NCQD-modified ZnS catalysts were successfully prepared. Under the irradiation of the full spectrum, the H2 evolution rate of the optimal catalyst 0.25 wt % NCQDs/ZnS achieves 5.70 mmol g-1 h-1, which is 11.88, 43.84, and 5.14 times the values of ZnS (0.48 mmol g-1 h-1), NCQDs (0.13 mmol g-1 h-1), and CQDs/ZnS (1.11 mmol g-1 h-1), respectively. Furthermore, it shows good stability, indicating that the modification of NCQDs prevents the photocorrosion and oxidation of ZnS. The enhanced performance is due to NCQD loading, which promotes the separation of photogenerated carriers, optimizes the structures, and increases the specific surface area. This work highlights the fact that NCQD-modified ZnS may afford a new strategy to synthesize ZnS-based photocatalysts with enhanced H2 production performance.

Facilitating the Electrochemical Oxidation of ZnS through Iodide Catalysis for Aqueous Zinc-Sulfur Batteries.

Aqueous zinc-sulfur (Zn-S) batteries show great potential for unlocking high energy and safety aqueous batteries. Yet, the sluggish kinetic and poor redox reversibility of the sulfur conversion reaction in aqueous solution challenge the development of Zn-S batteries. Here, we fabricate a high-performance Zn-S battery using highly water-soluble ZnI2 as an effective catalyst. In situ experimental characterizations and theoretical calculations reveal that the strong interaction between I- and the ZnS nanoparticles (discharge product) leads to the atomic rearrangement of ZnS, weakening the Zn-S bonding, and thus facilitating the electrochemical oxidation reaction of ZnS to S. The aqueous Zn-S battery exhibited a high energy density of 742 Wh kg(sulfur) -1 at the power density of 210.8 W kg(sulfur) -1 and good cycling stability over 550 cycles. Our findings provide new insights about the iodide catalytic effect for cathode conversion reaction in Zn-S batteries, which is conducive to promoting the future development of high-performance aqueous batteries.

Facilitating the Electrochemical Oxidation of ZnS through Iodide Catalysis for Aqueous Zinc‐Sulfur Batteries

AbstractAqueous zinc‐sulfur (Zn‐S) batteries show great potential for unlocking high energy and safety aqueous batteries. Yet, the sluggish kinetic and poor redox reversibility of the sulfur conversion reaction in aqueous solution challenge the development of Zn‐S batteries. Here, we fabricate a high‐performance Zn‐S battery using highly water‐soluble ZnI2 as an effective catalyst. In situ experimental characterizations and theoretical calculations reveal that the strong interaction between I− and the ZnS nanoparticles (discharge product) leads to the atomic rearrangement of ZnS, weakening the Zn‐S bonding, and thus facilitating the electrochemical oxidation reaction of ZnS to S. The aqueous Zn‐S battery exhibited a high energy density of 742 Wh kg(sulfur)−1 at the power density of 210.8 W kg(sulfur)−1 and good cycling stability over 550 cycles. Our findings provide new insights about the iodide catalytic effect for cathode conversion reaction in Zn‐S batteries, which is conducive to promoting the future development of high‐performance aqueous batteries.

Preparation and effective detection to H2S of PdO/ZnO/ZnS based sensor at low working temperature

To achieve rapid detection of hydrogen sulfide (H2S) gas at lower temperatures, We present a high-performance PdO/ZnO/ZnS-based H2S gas sensor, which was synthesized using a hydrothermal synthesis method in conjunction with an in situ sulfuration process and surface modification by PdO. Vacuum sintering to prevent high temperature oxidation of ZnS. The introduction of PdO not only makes the sheet ZnO/ZnS turn to spherical-like, but also increased the content of adsorbed oxygen. Compared with ZnO/ZnS sample, the PdO/ZnO/ZnS based sensor exhibited a higher response value of 212.4 to 10 ppm H2S at lower temperature of 100 °C, with response and recovery times of 2.9 and 1.7 min, respectively. In addition, excellent performance is demonstrated in terms of gas selectivity, repeatability and long-term stability during testing.

Effect of cobalt (nickel) oxide on the properties of zinc\u2013titanium sorbents for high temperature desulphurization of model coal gas

Zn–Ti–Co(Ni) sorbents for H2S removal from model hot coal were prepared and characterized. Effects of cobalt (Co) and nickel (Ni) on the sorbents texture, structure, H2S sorption capacity and regeneration properties were determined. TiO2 formed mixed metal oxides with CoO and NiO in the fresh sorbents, while TiO2 and nanocrystalline sulfides of Zn, Co, Ni were found in sulphided ones. The oxidative regeneration of sulphided sorbents re-formed mixed oxides. Sorption capacity of studied materials increased along with an increase of the amount of added Co (Ni) and also with the number of work cycles. Co-doped Zn–Ti materials adsorbed up to 244% more sulfur than these of Zn–Ti, while Ni-doped materials adsorbed ca. twice more H2S than the corresponding Co-doped sorbents. The addition of Co (Ni) decreased the temperature of ZnS oxidation. The catalytic effect of the Co (Ni) oxides on the oxidation of ZnS was suggested.

Thermal Evolution of ZnS Nanostructures: Effect of Oxidation Phenomena on Structural Features and Photocatalytical Performances.

ZnS nanosystems are being extensively studied for their possible use in a wide range of technological applications. Recently, the gradual oxidation of ZnS to ZnO was exploited to tune their structural, electronic, and functional properties. However, the inherent complexity and size dependence of the ZnS oxidation phenomena resulted in a very fragmented description of the process. In this work, different-sized nanosystems were obtained through two different low temperature wet chemistry routes, namely, hydrothermal and inverse miniemulsion approaches. These protocols were used to obtain ZnS samples consisting of 21 and 7 nm crystallites, respectively, to be used as reference material. The obtained samples were then calcinated at different temperatures, ranging from 400 to 800 °C toward the complete oxidation of ZnO, passing through the coexistence of the two phases (ZnS/ZnO). A thorough comparison of the effects of thermal handling on ZnS structural, chemical, and functional evolution was carried out by TEM, XRD, XAS, XPS, Raman, FT-IR, and UV-Vis. Finally, the photocatalytic activity in the H2 evolution reaction was also compared for selected ZnS and ZnS/ZnO samples. A correlation between size and the oxidation process was observed, as the smaller nanosystems showed the formation of ZnO at lower temperature, or in a larger amount in the case of the ZnS and ZnO co-presence. A difference in the underlying mechanism of the reaction was also evidenced. Despite the ZnS/ZnO mixed samples being characterized by an increased light absorption in the visible range, their photocatalytic activity was found to be much lower.

Ordered mesoporous Zn-based supported sorbent synthesized by a new method for high-efficiency desulfurization of hot coal gas

A new approach (microwave-hydrothermal plus oxidation) was proposed for the preparation of the Zn-based sorbents supported on the ordered mesoporous Si-based material. The hydrothermal synthesis and oxidation conditions of the sorbent precursor (ZnS/MCM41 mesophase) with Zn(AC)2 and thioacetamide (TAA) as the Zn and S sources, respectively, were optimized. The sorbents were evaluated in a fixed bed using the simulate gas of 2000 ppm H2S, 39% H2, 27% CO, 12% CO2, and N2 as balance gas. The structure of the sorbents was characterized by means of XRD, N2 adsoprtion, SEM, EDX, and TEM analysis. The results indicate that the optimal microwave-hydrothermal conditions are 400 W, 2.5 h, and 1:3 (the mole ratio of the Zn(AC)2 to TAA). The oxidation of ZnS in the sorbent precursor to ZnO is invalid at 550 °C due to unfavorable reaction kinetics. Both the fresh and used sorbents show ordered hexagonal mesoporous structure. It is confirmed that Zn2SiO4 present in the fresh and regenerated sorbents could be consumed during the desulfurization process via the reaction (Zn2SiO4 + 2H2S → 2ZnS + SiO2 + 2H2O), giving a positive effect on the desulfurization of the sorbents. The optimized Zn-based mesoporous sorbent (actual Zn content: 20.3%) exhibits superior (high breakthrough sulfur capacity: 5.4–5.7%) and stable desulfurization ability during five sulfidation/regeneration cycles. In addition, sulifidation reaction only leads to low-degree plugging of the pore structure of the regenerated sorbents, and the regeneration reaction could restore (at least mostly) the aforementioned changes in the pore properties.

Geochemistry, petrology and evolutionary computations in the service of archaeology: restoration of the historical smelting process at the Katowice\u2013Szopienice site

Activity at the smelting plant at Katowice–Szopienice dates back to the nineteenth century. Currently, the Museum of Zinc has been funded at the site. Unfortunately, as a result of unrest during both World Wars, all technological descriptions were lost. Three historically described samples were provided by Museum of Zinc and additional slag and lining samples were collected directly from the furnace. “Enriched ore” is dominated by ZnS (89.5%) as sphalerite and wurtzite accompanied by gangue minerals. “Roasted ore” is composed mainly of zincite (74%) resulting from the oxidation of ZnS. Study has proved that “roasted ore with coke” sample description is inappropriate. It is zinc depleted and enriched in Si (22.93 wt.%), Al (9.16 wt.%), C (9.66 wt.%) and its phase composition suggest that it contains recycled lining material and coke. Such characteristics place sample as additions used for smelting process. Advanced mathematical tool, the differential evolution algorithm, was used for restoration of smelting process at the site. Algorithm proved great usefulness by providing low dispersed results for calculated compositions of loss on smelting (mainly yield) with the fitting error reduced down to 1.19 wt.%. Loss on smelting composition was dominated by Zn (41.40 wt.%), Si (9.67 wt.%) and C (9.50 wt.%). Proportion of roasted ore to addition in smelting process was estimated as 1:1.27 and loss on smelting share from batch was 62%. Geochemistry and petrology have provided rich qualitative information about the samples and smelting process, but in combination with evolutionary computations, high-quality quantitative data were obtained.

Graded ZnS/ZnSxO1−x heterostructures produced by oxidative photolysis of zinc sulfide: Structure, optical properties and photocatalytic evolution of molecular hydrogen

Abstract The photolysis of microcrystalline and single crystal ZnS on the ambient air was found to result in the formation of metallic zinc clusters and radical sulfur species additionally to the elimination of sulfur in reactions with oxygen and generation of S vacancies. The latter process results in the formation of a graded alloyed ZnO x S 1−x layer with a continuously decreasing content of sulfur and increasing content of oxygen from the bulk to the surface of the crystals. These photolytic changes are observed within the surface layer with a thickness of 50–80 nm which is comparable to the depth of light penetration into the ZnS crystals. Coupling of ZnS to ZnO, both via pre-photolysis thermal oxidation of ZnS in the dark or by in situ formation of ZnO via the oxidative photocorrosion of ZnS accelerates the photolysis considerably, most probably, as a result of directed and opposite flow of the electrons and holes within the graded ZnO x S 1−x layer and suppression of the electron-hole recombination. The ZnS/ZnS x O 1−x heterostructures revealed a relatively high photocatalytic activity in hydrogen evolution from water/ethanol mixtures under illumination with the UV light with a quantum yield of up to 1.6% in the absence of any co-catalysts. The dependence between the rate of photocatalytic hydrogen formation and the duration of ZnS photolysis was found to be dome-shaped one as a result of the interplay of two factors—(i) an increase of the probability of the spatial separation of the electron and hole within the ZnO x S 1−x layer and (ii) a decrease of the probability of ethanol oxidation by the holes with an increase in the ZnS x O 1−x layer thickness (or photolysis duration as an equivalent). In the optimal conditions the rate of photocatalytic H 2 evolution was 30 times higher than that for original non-photolyzed ZnS owing to the unique graded structure of the alloyed zinc oxysulfide layer produced by the oxidative photolysis.

Sulfur–carbon yolk–shell particle based 3D interconnected nanostructures as cathodes for rechargeable lithium–sulfur batteries

A novel 3D interconnected S@C yolk–shell nanostructure from mild oxidation of ZnS@C accommodates S volume expansion upon lithiation in Li–S batteries, giving high capacity with good cycling performance.

Innovative low temperature regenerable zinc based mixed oxide sorbents for synthesis gas desulfurization

Zinc oxide-based materials are commonly used for the final desulfurization of synthesis gas in IGCC and Fischer–Tropsch based XTL processes. The formation of large amount of solid waste is the major issue of this process. In-situ oxidative regeneration is a promising way to reduce this waste formation and enhance desulfurization process efficiency and economics. However, previous studies showed that one of the major drawbacks of oxidative regeneration of sulfided oxides relies in the high operating temperature range required to overcome the formation of inhibitory sulfate phases. A preliminary work of the authors focused on single oxides identified that regeneration temperature of zinc oxide-based sorbent could be reduced through the addition of molybdenum oxide. Two composites oxides – a single oxides mixture (ZnO and MoO3) and a mixed oxide (ZnMoO4) – were synthesized and characterized. Their sulfidation and oxidative regeneration properties were investigated through thermogravimetry and in-situ characterizations. Sulfidation of the single oxides mixture was shown to be similar to the combination of the sulfidation of both independent single oxides. Mixed oxide sulfidation leads to ZnMoO4 phase demixing into ZnS, MoS2 and ZnMoO3. The oxidative regenerations of the sulfided single oxide mixtures and mixed oxide are initiated, respectively, at 350°C and 300°C. These temperatures are 250°C and 300°C lower than the regeneration temperature of a pure ZnS. For the sulfided mixed oxide regeneration is even complete at 500°C under isothermal conditions. Regeneration of sulfided oxides mixture and mixed oxide was thus shown to exhibit synergetic effects, resulting from exothermic oxidative reactions of molybdenum phases. Heat energy released during these reactions is assumed to enhance ZnS oxidation kinetics at a temperature lower than the previously measured one.

Response of a ZnO single crystal rod-based chemical sensor for hydrogen sulfide.

A zinc oxide single crystal rod was grown by a thermal evaporation method for application as a chemical gas-sensing material in this study. Zinc acetate (20 wt%) impregnated over activated carbon was used as the precursor for the epitaxial growth of ZnO single crystal rods. The response tests were carried out across a range of sensing temperatures (100, 150 and 200 °C) and the hydrogen sulfide content (10.2-51.0 ppmv) was balanced with nitrogen gas. The response of the ZnO single crystal rods grown on the gas sensors varied with the H2S content and the sensing temperature. A high response for H2S was obtained at 150 and 200 °C due to the high reactivity between H2S and ZnO at high temperature. Since H2S absorption rate and ZnS oxidation rate over ZnO single crystal rods at 100 °C lower than that at 150 and 200 °C, the changing rate of electric resistance decreased with the decrease of temperature. Meanwhile, a different response, which is the changing rate of electric resistance for H2S absorption and ZnS oxidation over ZnO single crystal rods at 100 °C, was observed with changing amount of H2S in feed gas. Therefore, it was concluded that the ZnO single crystal rods based gas sensor is operated above 200 °C for the shortly response time.

Time-resolved ultraviolet photoluminescence of ZnO/ZnGa2O4 composite layer

The ultraviolet photoluminescence of ZnO/ZnGa2O4 composite layer grown by the thermal oxidation of ZnS with gallium was investigated by the time-resolved photoluminescence as a function of measuring temperature and excitation power. With increase of excitation power, the D0X emission is easily saturated than the DAP emission from ZnO/ZnGa2O4 composite layer, and which is dramatically enhanced as compared with that from pure ZnO layer grown without gallium. The radiative recombination process with ultra-long lifetime controlled the carrier recombination of ZnO/ZnGa2O4 composite layer.

Features of ZnS-powder doping with a Mn impurity during synthesis and subsequent annealing

Luminescence, electron spin resonance, and X-ray diffraction (XRD) methods were used to investigate the features of ZnS-powder doped by Mn impurity during self-propagating high-temperature synthesis and subsequent annealing. The obtained powder consists of ZnS microcrystals with mainly hexagonal phase (80 ± 5)%. It was found, that after synthesis Mn presents not only in the form of non-uniformly distributed microscopic impurities in ZnS, but also in the form of Mn metal nanocrystals. Thermal annealing at 800°C leads to the additional doping of ZnS from metallic Mn, to the redistribution of the embedded Mn in the volume of microcrystals, and to the ZnS oxidation. At the same time, the ratio between the cubic and hexagonal phases does not change. It was shown that annealing causes a decrease in the concentration of the defects responsible for the luminescence-excitation bands, which correspond to transitions from the ground to the excited states of the Mn2+ ion. As a result of annealing, there is also a change in XRD coherent domain size. Simultaneously, the intensity of peaks in the luminescence-excitation spectrum with wavelengths of 375 and 395 nm was changed. The causes of these changes and the nature of the corresponding bands are discussed.

Structural transformations in ZnS:Cu in the course of thermal annealing

The influence of annealing at 800°C on the photoluminescence, electron spin resonance, and X-ray diffraction spectra of powder-like ZnS:Cu, obtained by the self-propagating high-temperature synthesis of a charge, consisting of Zn, S, and CuCl, is studied. It is shown that variation in the material’s heating rate up to the annealing temperature leads to a nonmonotonic variation in the spectral location and full-width at half-maximum of the photoluminescence band in the blue-green spectral region, as well as in the Mn2+ paramagnetic center concentration. It is established that the cubic and hexagonal ZnS phases, as well as the ZnO and CuZn phases, are present in the powder after synthesis. It is shown that annealing of the obtained powder at 800°C leads to three processes: the transformation of the hexagonal ZnS phase into the cubic phase, the oxidation of ZnS and CuZn, and the diffusion of Cu into the bulk of the ZnS microcrystals from the CuZn phase. A model attributing the observed variations in luminescence and electron spin resonance spectra to the diffusion of Cu and Mn impurities into the microcrystal bulk, particularly from the CuZn phase, and to their accumulation at extended defects is suggested.

Oxygen and sulfur isotope systematics of sulfate produced during abiotic and bacterial oxidation of sphalerite and elemental sulfur

Studies of metal sulfide oxidation in acid mine drainage (AMD) systems have primarily focused on pyrite oxidation, although acid soluble sulfides (e.g., ZnS) are predominantly responsible for the release of toxic metals. We conducted a series of biological and abiotic laboratory oxidation experiments with pure and Fe-bearing sphalerite (ZnS & Zn0.88Fe0.12S), respectively, in order to better understand the effects of sulfide mineralogy and associated biogeochemical controls of oxidation on the resultant δ34S and δ18O values of the sulfate produced. The minerals were incubated in the presence and absence of Acidithiobacillus ferrooxidans at an initial solution pH of 3 and with water of varying δ18O values to determine the relative contributions of H2O-derived and O2-derived oxygen in the newly formed sulfate. . Experiments were conducted under aerobic and anaerobic conditions using O2 and Fe(III)aq as the oxidants, respectively. Aerobic incubations with A. ferrooxidans, and So as the sole energy source were also conducted. The δ34SSO4 values from both the biological and abiotic oxidation of ZnS and ZnSFe by Fe(III)aq produced sulfur isotope fractionations (ε34SSO4-ZnS) of up to −2.6‰, suggesting the accumulation of sulfur intermediates during incomplete oxidation of the sulfide. No significant sulfur isotope fractionation was observed from any of the aerobic experiments. Negative sulfur isotope enrichment factors (ε34SSO4-ZnS) in AMD systems could reflect anaerobic, rather than aerobic pathways of oxidation. During the biological and abiotic oxidation of ZnS and ZnSFe by Fe(III)aq all of the sulfate oxygen was derived from water, with measured ε18OSO4-H2O values of 8.2±0.2‰ and 7.5±0.1‰, respectively. Also, during the aerobic oxidation of ZnSFe and So by A. ferrooxidans, all of the sulfate oxygen was derived from water with similar measured ε18OSO4-H2O values of 8.1±0.1‰ and 8.3±0.3‰, respectively. During biological oxidation of ZnS by O2, an estimated 8% of sulfate–oxygen was derived from O2, which is enriched in 18O relative to water, thus resulting in a larger apparent ε18OSO4-H2O value of 9.5‰. Based on the data presented we hypothesize that the similar ε18OSO4-H2O values of ∼8‰ from all of the aerobic and anaerobic experiments result from a common rate-limiting step that involves oxygen isotopic exchange between a sulfite (SO3-) intermediate and H2O. Our results indicate that the δ18OSO4 values cannot be used to distinguish biological and abiotic, nor aerobic versus anaerobic, pathways of sphalerite oxidation. However, the ε18OSO4-H2O values of ∼8‰ measured here are distinctly higher than ε18OSO4-H2O values of ∼4‰ previously reported for pyrite oxidation indicating the influence of sulfide mineralogy on measured δ18OSO4 values.

Imaging the Oxidation of ZnS Encapsulated in Carbon Nanotubes

Imaging the Oxidation of ZnS Encapsulated in Carbon Nanotubes

Characterization on thermal stability of ZnS:Mn 2+/MPS/SiO 2 nano-phosphor film

When the screen-printed ZnS:Mn 2+ nano-phosphor film is heated under ambient condition, the photoluminescence (PL) intensity due to the d–d transition of Mn 2+ decreases with increasing temperatures. The coating of 3-mercaptopropyl trimethoxysilane (MPS) and SiO 2 around ZnS:Mn 2+ nanoparticles is effective to suppress the decrease in the PL intensity by heating. This is explained by suppressing the oxidation of ZnS:Mn 2+ nanoparticles and the carbonization of propyl chain in MPS by SiO 2 coating.