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In previous work, it was shown that CaSO4-induced corrosion can cause significant internal oxidation in single-crystal Ni-based superalloys similar to that observed in field-exposed components when subjected to a bi-thermal exposure (8 h at 1150 °C → 60 h at 871 °C) in air + 30% steam. In this work, the influence of (1) 1150 °C initiation stage temperature, (2) propagation stage temperature, and (3) CaSO4 deposit mass on the mechanism of CaSO4-induced corrosion were investigated further. The results of these experiments showed that subsurface depletion of Al and Cr caused by rapid Ca4Al6O16S, CaAl2O4, and CrS formation due to CaSO4 corrosion is required for internal oxidation to occur in N5 and N500, but that these alloys can "heal" when held for long durations at 1150 °C due to the enhanced diffusion of Al within the alloy at elevated temperatures. [ABSTRACT FROM AUTHOR]

Sulfated zero-valent iron (SZVI) has shown promising applications in wastewater treatment. However, the rapid decline in the reactivity of SZVI with time limits its real practice. To mediate this problem, partial aging was proposed to improve the reactive durability of SZVI. Taking Cr(VI) as the target contaminant, we found that the aged ZVI (AZVI) gradually lost reactivity as aging time increased from 0.5 to 2 d. Counter-intuitively, the partially aged SZVI (ASZVI) showed greater reactivity than SZVI when exposed to oxygenated water for a period ranging from 0.5 to 14 d. In addition, the ASZVI with 0.5 d of aging time (ASZVI-0.5) not only maintained reactivity in successive runs but also increased the Cr(VI) removal capacity from 9.1 mg/g by SZVI to 19.1 mg/g by ASZVI-0.5. Correlation analysis further revealed that the electron transfer from the Fe0 core to the shell was mediated by the conductive FeS and FeS2 in the subshell of ASZVI. Meanwhile, the lepidocrocite and magnetite on the surface of ASZVI facilitated Cr(VI) adsorption and subsequent electron transfer for Cr(VI) reduction. Moreover, the iron (hydr)oxide shell could retain the conductive FeS and FeS2 in the subshell, allowing ASZVI to reduce Cr(VI) efficiently and sustainably. In general, partial aging can enhance the reactive durability of ZVI when coupled with sulfidation and this synergistic effect will be beneficial to the application of SZVI-based technology for wastewater treatment. [ABSTRACT FROM AUTHOR]

Ultralong nanowires with ultrahigh aspect ratios exhibit high flexibility, and they are promising for applications in various fields. Herein, a cadmium oleate precursor hydrothermal method is developed for the synthesis of ultralong nanowires of cadmium phosphate hydroxide. In this method, water-soluble cadmium salt is used as the cadmium source, water-soluble phosphate is used as the phosphorus source, and sodium oleate is adopted as a reactant to form cadmium oleate precursor and as a structure-directing agent. By using this method, ultralong nanowires of cadmium phosphate hydroxide are successfully synthesized using CdCl2, sodium oleate, and NaH2PO4 as reactants in an aqueous solution by hydrothermal treatment at 180 °C for 24 h. In addition, a new type of flexible fire-resistant inorganic paper with good electrical insulation performance is fabricated using ultralong nanowires of cadmium phosphate hydroxide. As an example of the extended application of this synthetic method, ultralong nanowires of cadmium phosphate hydroxide can be converted to ultralong CdS nanowires through a convenient sulfidation reaction. In this way, ultralong CdS nanowires are successfully synthesized by simple sulfidation of ultralong nanowires of cadmium phosphate hydroxide under mild conditions. The as-prepared ultralong nanowires of cadmium phosphate hydroxide are promising for applications as the precursors and templates for synthesizing other inorganic ultralong nanowires and have wide applications in various fields. [ABSTRACT FROM AUTHOR]

The Prussian blue analogue Co 3 [Co(CN) 6 ] 2 (Co-CoPBA) nanoparticles with three-dimensional cubic structure and uniform size were prepared via precipitation method. Using Co-CoPBA as the precursor, the porous Co 9 S 8 /N-doped carbon (Co 9 S 8 –CN) nanostructure was formed after heat treatment and sulfidation processes. To further improve the electrocatalytic activity of the composite, Mo 2 C was introduced within the porous Co 9 S 8 –CN. The Mo 2 C/Co 9 S 8 –CN materials containing different contents of Mo 2 C were prepared via high-temperature calcination and subsequent sulfidation. Ultimately, for electrochemical hydrogen storage, the porous Co 9 S 8 –CN exhibited higher discharge capacity than conventional Co 9 S 8 prepared by hydrothermal method. The special porous structure and large specific surface area derived from Co-CoPBA provided more electrochemical active sites. The conductivity of Co 9 S 8 was enhanced due to the existence of N-doped carbon. Additionally, the electrochemical performance further enhanced owing to the excellent electrocatalytic activity of the embedded Mo 2 C species. The Mo 2 C/Co 9 S 8 –CN2 electrode showed an optimum discharge capacity of 647.4 mAh/g. Moreover, the high-rate dischargeability (HRD), corrosion resistance and kinetic properties were also improved after Mo 2 C loading. Consequently, Mo 2 C/Co 9 S 8 –CN can be used as a potential electrochemical hydrogen storage material. [Display omitted] • Porous Co 9 S 8 -CN was prepared by heat treatment and sulfidation of Co 3 [Co(CN) 6 ] 2. • Co 9 S 8 -CN exhibited preferable electrochemical and kinetic properties than Co 9 S 8. • The conductivity of Co 9 S 8 was enhanced due to the existence of N-doped carbon. • The electrocatalytic activity of Co 9 S 8 -CN was further improved after Mo 2 C loading. • The Mo 2 C/Co 9 S 8 -CN2 electrode displayed better HRD, lower R ct and higher I 0 , D. [ABSTRACT FROM AUTHOR]

This study examines In2S3 concentration to the photo‐induced current density of particulate In2O3–In2S3 composite heterostructures under visible light irradiation. A self‐templated approach involving hydrothermal sulfidation of In2O3 nanofibers with thioacetamide (TAA) in water produces the In2O3–In2S3 core–shell structure at a moderate temperature. The In2S3 fraction is readily tunable by adjusting the TAA concentration. Incorporating In2S3 (45–82 wt.%) leads to a decreased bandgap from 3.1 to ca. 2.3 eV, enabling the harvest of partial visible‐light energy to create charged carriers efficiently. The photocurrent is particularly pronounced when the In2O3–In2S3 composites consist of 45 wt.% In2S3, to which the photocurrent intensity is more significant than 0.1 mA⋅cm−2 at 0.8 V in 0.1 M Na2SO4 solution compared to less than 0.01 mA⋅cm−2 for the rest of the In2O3–In2S3 counterparts. This is attributable to the enhanced electron–hole separation at the semiconducting heterojunction and the more efficient use of the light spectrum due to the narrowing bandgap. [ABSTRACT FROM AUTHOR]

This study conducts low-vacuum sulfidation to form a sulfidation layer on the serpentinite-derived magnesium iron silicate, thereby enhancing its electrochemical properties. Results show (Mg,Fe)2SiO4 calcined at 900 °C has the best crystallinity, and the cubic FeS2 is synthesized on the surface of the orthorhombic magnesium iron silicate (MFS). Two distinct charge plateaus can be distinguished during the first charge process, and the discharge capacities increased significantly. This study confirms that the surface FeS2 layer provides extra ion pathways, allowing more lithium/magnesium ions to be extracted and inserted in the serpentinite-derived magnesium iron silicate. Accordingly, the serpentinite electrode boasts straightforward exploitation with low-cost advantages and potential. [ABSTRACT FROM AUTHOR]

Coal is the most widely used fossil fuel resource, and clean coal technologies allow an increase in the efficiency of clean energy production. Gasification-based combined cycle power generation systems, for example, aim to produce a mixture of CO and H 2 (syngas) formed from coal and biomass. However, H 2 S is an undesired gasification product of fossil fuels with their high sulfur content. Hot gas desulfurization (HGD) reduces the sulfur contents of the gasification products by eliminating thermal losses of endothermic syngas formation processes. This study aims to develop efficient sorbents to remove H 2 S from hot flue gas. Unsupported and SBA 15-supported Ca-based binary mixed metal oxides (CuO, FeO, MnO, ZnO) were synthesized as sulfur sorbents by the wet impregnation method. The crystal structure of the sorbents was determined by X-ray diffraction (XRD), while BET analysis was used to determine the surface area and pore size distribution of the sorbents. The results of the XRD and BET analyses revealed mixed metal oxide formation and a high surface area of SBA 15-supported sorbents, respectively. Mixed metal oxide formation was also confirmed by Fourier transform infrared radiation (FTIR) spectroscopy. The desulfurization performance of the sorbents was examined by a simulated gas mixture at 800 °C. A gas chromatography analyzer equipped with a flame photometric detector was used to follow the H 2 S concentration. SBA 15-supported CaO–MnO exhibited the best desulfurization performance at 800 °C with a breakthrough sulfur capacity (BSC) of 43.38 g S/100 g sorbent in the longest breakthrough time of 1077 min. • SBA 15 improves the sulfidation performance of CaO–CuO, CaO–FeO, and CaO–MnO at 800 °C. • A synergistic effect was observed between CaO–MnO in the presence of SBA 15 support material. • SBA 15-supported CaO–MnO gives the best sulfidation performance with a breakthrough sulfur capacity of 43.38 g S/100 g sorbent. • The highest breakthrough sulfur capacity of unsupported sorbent is 8.81 g S/100 g for CaO–CuO. [ABSTRACT FROM AUTHOR]

Ag and its alloys, when prepared by a selective laser melting (SLM) process, have a low density and poor overall performance due to their high reflectivity when the most commonly used laser (λ = 1060 nm) is used, and they have exorbitant thermal conductivity. These characteristics lead to the insufficient melting of the powders and severely limit the applications of additive manufactured silver alloys. To improve the absorption of the laser, as well as for better mechanical properties and higher resistance to sulfidation, Ag–Cu alloys with different La2O3 contents were prepared in this work using the SLM process, via the mechanical mixing of La2O3 nanoparticles with Ag–Cu alloy powders. A series of analyses and tests were conducted to study the effects of La2O3 in Ag–Cu alloys on their density, microstructure, mechanical properties, and corrosion resistance. The results revealed that the addition of La2O3 particles to Ag–Cu alloy powders improved the laser absorptivity and reduced defects during the SLM process, leading to a significant rise from 7.76 g/cm3 to 9.16 g/cm3 in the density of the Ag–Cu alloys. The phase composition of the Ag–Cu alloys prepared by SLM was Silver-3C. La2O3 addition had no influence on the phase composition, but refined the grains of the Ag–Cu alloys by inhibiting the growth of columnar grains during the SLM process. No remarkable preferred orientation existed in all the samples prepared with or without La2O3. An upwards trend was achieved in the hardness of the Ag–Cu alloy by increasing the contents of La2O3 from 0 to 1.2%, and the average hardness was enhanced significantly, from 0.97 GPa to 2.88 GPa when the alloy contained 1.2% La2O3 due to the reduced pore defects and the refined grains resulting from the effects of the La2O3. EIS and PD tests of the samples in 1% Na2S solution proved that La2O3 addition improved the corrosion resistance of the Ag–Cu alloys practically and efficaciously. The samples containing La2O3 exhibited higher impedance values and lower corrosion current densities. [ABSTRACT FROM AUTHOR]

In situ construction of polymetallic layered double hydroxide (LDH) @sulfide heterostructures (LDH@sulfides) is a promising strategy to achieve excellent electrochemical performance by providing more redox active sites and facilitating ion/electron pathways. Herein, nickel cobalt molybdenum based LDH@sulfide core–shell composites (NCM-LDH@NCMS) grown on Ni foam have been successfully prepared via a facile hydrothermal method, followed by controllable sulfidation methods. The effect of sulfidation time on the electrochemical performance of NCM-LDH@NCMS was investigated. The NCM-LDH nanosheets minimized the diffusion path of electrolyte ions and accelerated the kinetics of redox reactions, and the outer Ni–Co–Mo sulfides effectively improved the conductivity of LDHs and exposed more active sites. With sulfidation for 2 h, the obtained NCM-LDH@NCMS-2 exhibited excellent electrochemical performance, with a specific capacitance of ∼7.73 F cm−2 at 10 mA cm−2, and better capacitance rate performance of 56.7% at 50 mA cm−2. Furthermore, hybrid NCM-LDH@NCMS-2//activated carbon supercapacitors provided a high energy density of 0.25 mW h cm−2 at 40 mW cm−2 and excellent cycling stability of 89.82% after 8000 cycles at 8 mA−2. [ABSTRACT FROM AUTHOR]

Future technologies require structural materials resistant to environmental degradation in high-temperature CO2-rich environments. Herein, we exposed several commercially available Ni-based alloys (230, 263, 282, 617, 625, and 740H) to atmospheric pressure gases intended to simulate the compositions expected in future direct-fired supercritical CO2 power cycles. The alloys were exposed to 95% CO2 + 4% H2O + 1% O2 and the same gas containing 0.1% SO2 at temperatures of 600, 650, 700, 750, and 800 °C for 2500 h. With minor exceptions, chromia scales formed on all alloys at all temperatures in the SO2-free gas, yielding parabolic growth rates that followed an Arrhenius temperature dependence. Behavior in the SO2-containing gas was more complex. Generally, the alloys performed well at temperatures of 650, 750, and 800 °C. While some alloys further performed relatively well across the whole temperature range, several of the alloys experienced chromia failure resulting in non-protective duplex oxide scales and high oxidation rates, at temperatures of 600 and 700 °C. Deviation from protective behavior was associated with internal sulfide formation and, additionally for the case of 600 °C, external sulfate formation. Extensive carburization accompanied growth of the non-protective duplex oxide scales, which made it more difficult for the alloy to recover after initiation of the sulfur-induced accelerated corrosion process. The thermodynamic and kinetic factors influencing the accelerated corrosion in the presence of sulfur are discussed. The results suggest that caution is required when assessing compatibility of Ni-based alloys for CO2-based systems when sulfur-based impurities are expected. [ABSTRACT FROM AUTHOR]

Cawood et al. (this issue) critize our hypothesis of a pre-Klondikean weathering/oxidation event having affected the Aggeneys-Gamsberg ore district. Instead, they reinforce the long-held view that the sulfide deposits of the ore district with its pronounced metal zonation, its unusually high mineralogical variability and numerous geochemical anomalies are the product of amphibolite- to granulite-facies metamorphic overprint of originally syn-sedimentary exhalative deposits. Here we gladly use the opportunity to counter all issues raised and explain further our evidence of oxidation and subsequent re-sulfidation of the original synsedimentary deposits. [ABSTRACT FROM AUTHOR]

Höhn et al. (2021) proposed that the giant Gamsberg Zn deposit, South Africa, initially formed as a sedimentary exhalative (SEDEX) deposit during the Mesoproterozoic and was subsequently oxidized near surface. The oxidized ore was then supposedly sulfidized by sulfur-rich metamorphic fluids during and after upper amphibolite facies metamorphism. We view this model as untenable for various reasons and suggest that the Gamsberg deposit and others in the Aggeneys-Gamsberg district (Swartberg, Broken Hill-Deeps, Big Syncline) are metamorphosed clastic SEDEX deposits rather than having formed by synmetamorphic sulfidation processes. [ABSTRACT FROM AUTHOR]

The development of low cost, efficient and stable overall water splitting electrocatalysts is essential for green hydrogen production. In this work, we report a defect-rich MoS2/CoS2 heterostructure supported on in situ formed graphene layers (MoS2/CoS2/C) synthesized via gas-phase sulfidation, which enables bifunctionality towards electrocatalytic oxygen evolution and hydrogen evolution reactions (OER and HER). In alkaline medium, the catalyst exhibited overpotentials of 170 mV and 293 mV for HER and OER, respectively. In an alkaline electrolyzer using MoS2/CoS2/C as both cathode and anode, a cell voltage of 1.68 V was delivered at a current density of 10 mA cm−2, and remarkable stability maintained during 20 h of chronoamperometry test. Furthermore, the Faraday efficiencies of HER and OER in electrolytic water systems are as high as 97.3% and 94.7%, respectively. The good HER and OER catalytic activity over the MoS2/CoS2/C catalyst could be attributed to the abundance of defects, the strong interaction between MoS2 and CoS2, the large electrochemical surface area, and the excellent electron conductivity. Therefore, this work may provide an effective strategy for future development of overall water splitting catalysts. [ABSTRACT FROM AUTHOR]

We propose that the observed enrichment of sulfur at the surface of Mercury (up to 4 wt.%) is the product of silicate sulfidation reactions with a S‐rich reduced volcanogenic gas phase. Here, we present new experiments on the sulfidation behavior of olivine, diopside, and anorthite. We investigate these reaction products, and those of sulfidized glasses with Mercury compositions previously reported, by mid‐IR reflectance spectroscopy. We investigate both the reacted bulk materials as powders as well as cross‐sections of the reaction products by in situ micro‐IR spectroscopy. The mid‐IR spectra confirm the presence of predicted reaction products including quartz. The mid‐IR reflectance of sulfide reaction products, such as CaS (oldhamite) or MgS (niningerite), is insufficient to be observed in the complex run products. However, the ESA/JAXA BepiColombo mission to Mercury will be able to test our hypothesis by investigating the correlated abundances of sulfides with other reaction products such as quartz. Plain Language Summary: The surface of the planet Mercury is enriched in sulfur, with abundances of up to 4 wt.%. Sulfur on Mercury has previously been interpreted to occur in magmatic sulfide phases. We propose an alternative mechanism for the enrichment of S on Mercury, whereby reduced S‐rich gases react with silicate minerals to form sulfides and quartz. We carried out sulfidation experiments on silicate minerals and glasses and used mid‐infrared spectroscopy to characterize the products of these reactions. The upcoming ESA/JAXA BepiColombo mission to Mercury will allow us to test the sulfidation hypothesis and provide constraints on the origin of the S enrichment on the planet's surface. Key Points: S‐enrichment on the surface of Mercury by sulfidation of silicate mineralsMid‐IR spectroscopy allows the identification of quartz as a main reaction product in mineral and glass sulfidationBepiColombo's Mercury Radiometer and Thermal Infrared Spectrometer instrument will test the sulfidation hypothesis by mapping the surface of Mercury in the mid‐IR spectral range [ABSTRACT FROM AUTHOR]

Although transition metal sulfides have prodigious potential for use as electrode materials because of their low electronegativities, their large volume changes inhibit broad application. Moreover, there is only limited knowledge of the ageing processes of these materials at the nanoscale. Herein, nano-C/FeS2 materials were prepared via one-pot syntheses from green biodegradable carbon precursors, followed by activation and sulfidation. The increased activation/sulfidation time led to an increase in the size of the nanoparticles (7 to 17 nm) and their aggregation, as well as in an increase in the specific surface area. The materials were then used as electrodes in 2-electrode symmetric supercapacitors with 2 M KOH. The activation process resulted in improved capacitance (60 F g−1 at 0.1 A g−1) and rate capability (36%) depending on the composite porosity, conductivity, and size of the FeS2 particles. The ageing of the FeS2 nanoparticles was investigated under air, and a progressive transformation of the nano-FeS2 into hydrated iron hydroxy sulfate with a significant morphological modification was observed, resulting in drastic decreases in the capacitance (70%) and retention. In contrast, the ageing of nano-FeS2 during cycling led to the formation of a supplementary iron oxyhydroxide phase, which contributed to the enhanced capacitance (57%) and long-term cycling (132% up to 10,000 cycles) of the device. [ABSTRACT FROM AUTHOR]

Cerussite is an essential lead oxide mineral with increasing economic importance as lead sulfide resources deplete. This study utilizes density functional theory (DFT) to investigate the structural and electronic properties of the sulfurized cerussite (110) surface. The results show that when the cerussite crystal cleaves along the (110) plane, only the surface layer atoms undergo relaxation to reconstruct the surface, while the atoms located deeper have almost no impact on the reconstructed surface structure. The Pb atoms on the cerussite (110) surface react with the sulfurizing agent to form a PbS deposition layer with a structure similar to galena. This PbS deposition layer is tightly adsorbed onto the lead oxide layer through Pb-S bonds formed by S and subsurface lead oxide structure Pb atoms. The chemical reactivity of Pb atoms in the PbS layer on the sulfurized cerussite (110) surface is more potent than that of Pb atoms on the galena surface; additionally, the Pb atoms closer to the lead oxide layer exhibit slightly higher chemical reactivity than those farther away. This study provides insight into sulfurized cerussite surfaces’ structure and properties at an atomic level and assists in explaining the floating behavior of cerussite.

Aqueous zinc‐based batteries are a promising alternative to lithium batteries. These batteries, however, persistently suffer from uncontrollable dendrite growth and sustained water consumption at the Zn anodes, along with low and often fading capacity at the cathodes. Herein, Zn metal is simply encapsulated into a chitosan‐containing polymer gel that not only suppresses hydrogen evolution but also enables dendrite‐free Zn plating/stripping. A binder‐free cathode based on the electrochemically exfoliated and partially sulfidated Ni–Co–Fe layered double hydroxide‐reduced graphene oxide (SNS‐rGO) nanocomposite is also reported. The fabricated devices (based on either Zn or chitosan‐coated Zn) deliver near record‐high values of specific capacity (756 mA h g−1cathode at 1 A g−1) and specific energy (1284 W h kg−1cathode), along with an outstanding specific power (108 kW kg−1cathode), an excellent output voltage (up to 1.9 V), and prolonged cycling stability at 100% depth‐of‐discharge. This interface engineering strategy, supported by the density functional theory calculations, provides a solid basis for further practical applications of aqueous Zn batteries. [ABSTRACT FROM AUTHOR]

A facile and general strategy for preparing carbon supports with ideal sintering resistance using electrospinning and sulfidation treatment is reported in this paper. The strong interaction between PtCu and N,S-codoped electrospinning porous carbon nanofibers can stabilize PtCu nanoparticles (NPs) below 4 nm to 800 °C. The as-prepared PtCu-800/NS-PCNFs exhibit superior catalytic performances for oxygen reduction reaction (ORR). The PtCu-800/NS-PCNFs presents the mass activity (MA) and specific activity (SA) of 0.4785 A mg−1 and 0.6343 mA cm−2, which is 3.1 times and 2.4 times that of commercial Pt/C. More important, the electrochemical surface area (ECSA) of PtCu-800/NS-PCNFs is 1.3 times larger than that of commercial Pt/C. Therefore, the improved ORR activity can be ascribed to the synergistic interaction between Pt and Cu and the uniform distribution of catalyst nanoparticles. • NS-PCNFs with high specific surface area were prepared by electrospinning and sulfidation treatment. • The strong interaction between PtCu and NS-PCNFs can stabilize PtCu NPs during the high-temperature reduction process. • The PtCu nanoparticles were loaded on NS-PCNFs by the impregnation-reduction method. • The PtCu-800/NS-PCNFs showed an efficient activity in the ORR compared with the commercial Pt/C. [ABSTRACT FROM AUTHOR]

Nanoscale zero‐valent iron (nZVI) has demonstrated high potential for the remediation of contaminated groundwater. Its lifetime is directly related to the hydrophobicity of nZVI. A promising approach to enhance the lifetime of nZVI is through sulfidation. Herein, the density functional theory (DFT) is applied to understand the impact of sulfidation on the hydrophobicity of stepped Fe surfaces. Adsorption properties of sulfur (S) at different coverages on the flat Fe(110) and stepped Fe(210) and Fe(211) surfaces are investigated. Sulfur has the stronger adsorption at a low surface coverage due to limited S–S repulsion. At the highest coverage (⊖ = 1 ML) on Fe(210) and Fe(211), the atoms at the step edges catalyze the formation of iron sulfides. The DFT results show surface hydrophobicity is mainly determined by the S coverage. At the low S coverage, the surface may become more hydrophilic due to the enhanced adsorption strength of water on the surface. However, an increase in the S coverage can efficiently block water adsorption, which is further evidenced by ab initio molecular dynamics (AIMD) results. The findings show that controlling S coverages is essential to engineer the hydrophobicity of nZVI surfaces for practical water remediation applications. [ABSTRACT FROM AUTHOR]

Mid-wavelength InSb and HgCdTe photodiodes (PDs) passivated with polycrystalline CdTe films have been studied. Passivating layers were deposited at low temperatures by the hot-wall epitaxy (HWE) technique. The PDs were characterized by measurements of the dark current and minority carrier lifetime. It is shown that heterovalent and isovalent (CdTe/InSb and CdTe/HgCdTe) interfaces have different effects on the PD characteristics. Passivation of HgCdTe does not affect the lifetime of the carriers, but the stability of the dark current in passivated PDs is insufficient for long-term operation. In the InSb PDs, the processing steps, including successive etching in CP4A and HCl etchants, sulfidization in an aqueous solution of Na2S, followed by the deposition of a protective CdTe layer, led to the best result. It has been established that the electrical properties of the passivating layers of polycrystalline CdTe are determined by the space charge-limited current. Conclusions are drawn about the applicability of the HWE technique for the passivation of infrared photodetectors. [ABSTRACT FROM AUTHOR]

In this work, an innovative process involving directional sulfurization–vacuum distillation is proposed to effectively remove trace levels of mercury impurities from crude selenium. First, a reaction between sulfur and mercury is used to break the strong chemical Se-Hg bond to achieve the sulfide mineralization of mercury. Second, selenium and mercury are separated by vacuum distillation based on a difference in volatility. Thermodynamic analysis confirms the feasibility of this method. The experimental results show that the sulfidation reaction potential energy of different sulfidizing agents is in the order S > Na2S > FeS, and the optimum conditions are determined to be the following: a sulfidation temperature of 473 K and time of 30 min, and vacuum distillation experimental parameters of 503 K, 60 min, and 10–20 Pa system pressure. The overall experimental results show that the maximum removal of mercury is 97.49%. The content of mercury in the refined selenium was reduced from 0.32% to 0.0088% in the volatile matter. The results have practical value for the separation of selenium and mercury from hazardous wastes. [ABSTRACT FROM AUTHOR]

Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation. In this work, inductively coupled plasma optical emission spectrometer (ICP-OES) measurements, Visual MINTEQ calculation, X-ray photoelectron spectroscopy (XPS) analysis, time of flight secondary ion mass spectrometry (ToF-SIMS) analysis, and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate ((NH4)2SO4) on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation. The results showed that (NH4)2SO4 exhibited a positive influence on hemimorphite sulfidation flotation. It was ascribed to the number of zinc components in the form of Zn2+ and [Zn(NH3)i]2+ (i = 1–4) increased in the flotation system after hemimorphite treatment with (NH4)2SO4, which was beneficial to its interaction with sulfur species in solution, resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface. [Zn(NH3)i]2+ participated in the sulfidation reaction of hemimorphite as a transition state. In addition, the sulfidation reaction of hemimorphite was accelerated by (NH4)2SO4. Thus, (NH4)2SO4 presents a vital role in promoting the sulfidation of hemimorphite. [ABSTRACT FROM AUTHOR]

Active sites in Mo-based hydrotreating catalysts are produced by sulfidation. To achieve insights that may enable optimization of the catalysts, this process should be studied in situ. Herein we present a comparative XAFS study where the in situ sulfidation of Mo/δ-Al2O3 and Ni/δ-Al2O3 is compared to that of δ-Al2O3 supported NiMo catalysts with different NiMo ratios. The study also covers the comparison of sulfidation of Ni and Mo using different oxide supports as well as the sulfidation conditions applied in the reactor. The XAFS spectra confirms the oxide phase for all catalysts at the beginning of the sulfidation reaction and their conversion to a sulfidized phase is followed with in situ measurements. Furthermore, it is found that the monometallic catalysts are less readily sulfidized than bimetallic ones, indicating the importance of Ni-Mo interactions for catalyst activation. Mo K-edge XAFS spectra did not show any difference related to the support of the catalyst or the pressure applied during the reaction. Ni K-edge XAFS spectra, however, show a more complete sulfidation of the Ni species in the catalyst when SiO2 is used as a support as compared to the Al2O3. Nevertheless, it is believed that stronger interactions with Al2O3 support prevent sintering of the catalyst which leads to its stabilization. The results contribute to a better understanding of how different parameters affect the formation of the active phase of the NiMo catalysts used in the production of biofuel. [ABSTRACT FROM AUTHOR]

Oxygen fugacity (fO2) is a key intensity variable during the entire magmatic‐hydrothermal mineralization courses. The redox state and its variations between different stages of the ore‐forming fluids of intermediate sulfidation epithermal deposits are rarely deciphered due to the lack of appropriate approaches to determine fO2 of the fluids. Here, we reported the δ34S of the sulfides from three different stages (stage I, II, III) of Zhengguang, an Early Ordovician Au‐rich intermediate sulfidation (IS) epithermal deposit, to decipher the redox evolution of the ore‐forming fluids. The increasing δ34S values from stage I pyrite (py1, average –2.6‰) through py2 (average –1.9‰) to py3 (average –0.2‰) indicates a decrease of the oxygen fugacity of the ore‐forming fluids. A compilation of δ34S values of sulfides from two subtypes of IS deposits (Au‐rich and Ag‐rich) from NE China shows that the δ34S values of sulfides from Au‐rich IS deposits are systematically lighter than those of Ag‐rich IS Ag‐Pb‐Zn deposit, indicating the ore‐forming fluids of the former are more oxidized than the latter. We highlight that sulfur isotopic composition of hypogene sulfides is an efficacious proxy to fingerprint the oxygen fugacity fluctuations of epithermal deposits and could potentially be used to distinguish the subtypes of IS deposits. [ABSTRACT FROM AUTHOR]

This study proposed a sulfidation process as a practical approach for recovering Ni from the acidic spent catalyst. Ni can be obtained by a precipitate as NiS particle by adding Na2S in the acidic media (pH 3). In the presence of chelate agents, 2,2'-bipyridine (bpy), the percentage value of Ni recovery by a hydroxylation process was only 46%, and the recovery value improved to 88% by the sulfidation. XAFS analyses for the precipitates showed that more than 60% of NiS from chelate-free media was oxidized to NiSO4; while about 80% of Ni remained as NiS when it was generated in the bpy-containing condition. However, Ni was also bound with bpy in the NiS particle, revealed by FT-IR spectra. From these results,, in the spent catalyst, Ni would be precipitated as an S-Ni-bpy cluster by the sulfidation process. [ABSTRACT FROM AUTHOR]

Environmental context: Arsenic (As) contamination in agricultural soil threatens safe agricultural production. Therefore, an ex situ magnet-assisted soil washing, using different types of nanoscale zerovalent iron was tested as a remediation option in soil restoration. Uncoated nanoparticles was the best tested option, with As removal at 45.5% and the nanoparticles were reusable up to four times. Rationale: Arsenic (As) contamination in agricultural soil threatens safe food and medicinal herb production for millions of people. Methodology: Therefore, ex situ magnet-assisted soil washing of metal-contaminated soil using bare nanoscale zerovalent iron (NZVI) is proposed as a novel remediation alternative. Conceptually, metal-contaminated soil is mixed with water and bare NZVI, and metals in the soil are transferred to the bare NZVI. The metal-sorbed NZVI is then retrieved from the soil slurry through magnetic separation, leaving behind treated soil. This study evaluated if advanced surface modification can improve ex situ soil restoration efficacy including polymeric coating and sulfidation of NZVI, proven beneficial in situ NZVI application. Sulfur and carboxymethylcellulose (CMC) at various S/Fe and CMC/NZVI ratios were used to modify NZVI via sulfidation and physisorption. Result: Results revealed that sulfidised NZVI (S-NZVI) performed poorer (41.0%) than bare NZVI (45.5%) in As removal, even at the optimised S/Fe ratio of 0.31. This could be due to acid release via oxidative dissolution of FeS[sub 2] on the S-NZVI surface driven by O[sub 2]. The incidental acid-dissolved NZVI sorption sites decreased As removal efficacy. Similarly, CMC-modified NZVI failed to improve As removal efficacy (11.0%) because it reduced NZVI reactivity and blocked As accessibility to NZVI sorptive sites. Discussion: Nevertheless, S-NZVI and CMC-modified NZVI promoted non-phytoavailable As fractions in the treated soil. Overall, bare NZVI performed the best for As removal but moderately transformed As into more non-phytoavailable fractions. Bare NZVI can be reused for four cycles of soil washing. In every case, mobile As in treated soil was lower than the maximum contamination level. [ABSTRACT FROM AUTHOR]

Cu2O with a cubic structure was prepared by a water bath method, and then a Cu2O/Cu2S core–shell material was obtained by the redox reaction of Cu2O and Na2S with the prepared cubic Cu2O as a template and Na2S·9H2O solution as the reaction solution. At the same time, the effect of sulfidization time on the Cu2O/Cu2S structure and photohydrogen production performance was studied. The structure of the samples was further confirmed and characterized through SEM, HRTEM, XRD and XPS. The photohydrogen production properties of the Cu2O/Cu2S composites with different morphologies were tested. The flower-shaped hollow structure of Cu2O/Cu2S can be obtained by proper sulfidization, and the hydrogen production can reach 1076.95 μmol g−1 after 5 h of illumination. Then, through photocurrent response and impedance spectrum tests and DFT calculations, it is proved that the Cu2O/Cu2S heterostructure can effectively improve the photoresponse ability and carrier transport properties. It was confirmed that the interfacial charge transfer in Cu2O/Cu2S helped increase the photocatalytic hydrogen production performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile recycling of spent lithium battery is achieved based on selective sulfidation. • The process and mechanism of selective sulfidation of cathode materials are clarified. • The metals in spent lithium battery are effectively separated by the proposed process. • The regenerated cathode materials have excellent electrochemical performance. • The new regeneration strategy shows great environmental and economic benefits. The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNi x Co y Mn z O 2 (NCM) batteries. The spent NCM was converted into water-soluble Li 2 CO 3 , acid-dissolved MnO, and nickel–cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H 2 SO 4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li 2 CO 3 , MnSO 4 , and nickel–cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92 %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs. [ABSTRACT FROM AUTHOR]

The sulfidation kinetics of titanium and Ti-6Al-4V (Ti64) using elemental sulfur were studied by measuring the amount of metal consumed instead of the change in mass or scale thickness. This metal consumption approach combines the parabolic oxidation law, Arrhenius equation, and Pilling-Bedworth ratio to determine the apparent activation energy and the pre-exponential factor of consumption of Ti64 during sulfidation. The estimations of apparent activation energy and pre-exponential factor were 110.4 kJ·mol−1 and 1.3 × 10−9 m2s−1 for the titanium-sulfur, and 116.2 kJ·mol−1 and 1.2 × 10−9 m2s−1 for the Ti64-sulfur system. Finally, a material removal predictor was developed to predict the amount of Ti64 consumed for a given sulfidation temperature and time. [ABSTRACT FROM AUTHOR]

The concentrations of trace elements in pyrite and enargite-luzonite from target 185 of the copper-gold high sulphidation Chelopech deposit were determined by LA-ICP-MS. Their average contents in ppm based on 12 analyses of pyrite and 10 analyses of enargite-luzonite are respectively: Ti (6548) > Cu (3449) > V (580) > Mn (299) > Pb (173) > As (157) > Se (149) > Te (122) > Zn (80) > Co (79) > Bi (41) > Cr (29) > W (25) > Sn (22) > Ni (17) > Au, Ga (15) > Ag (14) > Mo (9) > Sb (5) > Tl (4) > Hg (1) > In (0.2) for the first one and Fe (26531) > Zn (22140) > Sb (11014) > Bi (7956) > Se (1730) > Sn (1016) > Pb (995) > Te (326) > Mn (205) > Mo (170) > Hg (100) > Ge (88) > Ag (46) > Ti (42) > W (25) > Cd (24) > V (19) > Au (16) > In (4) > Tl (3) > Ga (1) for the second. [ABSTRACT FROM AUTHOR]

This paper aims to characterize and test the stability of sulfuric natural water (SNW) from Sebau East Lombok as a sulfidation agent for several dissolved metals (Mn, Cu, Pb and Fe). The parameters used for SNW characterization are temperature, pH, DO, BOD, COD, TSS, and TDS. The sample was divided into two categories, namely the sample with preservation treatment and the sample without preservation, to study the stability of SNW. The SNW stability was determined by observing the SNW parameters in both samples at a storage time of 5, 10, 15 and 20 days and reacting them with dissolved metals. The SNW with preservation had reduced sulphide levels from day 1 to day 20, ranging from 59.24 mg/L to 17.70 mg/L, whereas the sample without preservation had decreased sulphide concentration from 52.46 mg/L to 9.56 mg/L. Furthermore, the SNW with preservation has a relatively superior metal reduction ratio than the sample without preservation. The maximum value of the deposition ratio for Mn metal was obtained on the fifth day with 57.60%, 83.45% for Cu, and 91.87% for Pb. This trend is not applicable for Fe, whereas the highest reduction (87.23%) was obtained on the the15th day's storage.

Thioethers are critical in the fields of pharmaceuticals and organic synthesis, but most of the methods for synthesis alkyl thioethers employ foul-smelling thiols as starting materials or generate them as by-products. Additionally, most thiols are air-sensitive and are easily oxidized to produce disulfides under atmospheric conditions; thus, a novel method for synthesizing thioethers is necessary. This paper reports a simple, effective, green method for synthesizing dialkyl or alkyl aryl thioether derivatives using odorless, stable, low-cost ROCS2K as a thiol surrogate. This transformation offers a broad substrate scope and good functional group tolerance with excellent selectivity. The reaction likely proceeds via xanthate intermediates, which can be readily generated via the nucleophilic substitution of alkyl halides or aryl halides with ROCS2K under transition-metal-free and base-free conditions.

Nanoscale zero‐valent iron (nZVI) has demonstrated high potential for the remediation of contaminated groundwater. Its lifetime is directly related to the hydrophobicity of nZVI. A promising approach to enhance the lifetime of nZVI is through sulfidation. Herein, the density functional theory (DFT) is applied to understand the impact of sulfidation on the hydrophobicity of stepped Fe surfaces. Adsorption properties of sulfur (S) at different coverages on the flat Fe(110) and stepped Fe(210) and Fe(211) surfaces are investigated. Sulfur has the stronger adsorption at a low surface coverage due to limited S–S repulsion. At the highest coverage (⊖ = 1 ML) on Fe(210) and Fe(211), the atoms at the step edges catalyze the formation of iron sulfides. The DFT results show surface hydrophobicity is mainly determined by the S coverage. At the low S coverage, the surface may become more hydrophilic due to the enhanced adsorption strength of water on the surface. However, an increase in the S coverage can efficiently block water adsorption, which is further evidenced by ab initio molecular dynamics (AIMD) results. The findings show that controlling S coverages is essential to engineer the hydrophobicity of nZVI surfaces for practical water remediation applications.

Among the physical and chemical properties of nanomaterials, hydrophobicity is considered to play a key role in their impact on the environment. Changes in hydrophobicity resulting from abiotic and biotic processes can be used to predict the behaviours of nanoparticles (NPs) in the environment (e.g., aggregation, toxicity, and bioaccumulation). Hydrophobicity changes induced by sulfidation and natural organic matter (NOM) corona formation were evaluated by monitoring the binding rate of silver (Ag) NPs on engineered surfaces using dark-field microscopy (DFM). It was found that this DFM-based method was more capable of distinguishing the hydrophobicity of environmentally relevant AgNPs than the dye adsorption method. Under the conditions tested in this study, sulfidation and adsorption of sulfidized NOM/“lipid-free” (LF-)NOM increased the hydrophobicity of AgNPs. Both methods demonstrate the tendency of AgNPs to become more hydrophobic after sulfidation. This study shows that DFM-based methods can effectively measure the hydrophobicity of environmentally relevant NPs and have the potential to be widely used as fate predictors in the future.

Sulfidated and bimetal modification can improve the reactivity and selectivity of zero-valent iron in contaminant removal. However, previous studies were focused on unilateral material approaches. In this article, a new hybrid composite Ag/S-ZVI was prepared by doping elemental silver on surface of sulfidated nanoscale zerovalent iron (S-nZVI). The results of X-Ray Diffraction (XRD), energy dispersive spectrometer (EDS) and X-ray Photoelectron Spectroscopy (XPS) indicated Ag was dispersed on the surface of S-nZVI. Scanning electron microscope (SEM) images displayed Ag/S-ZVI was irregular clusters with rough surfaces, small agglomeration, and quasi-spherical in shape. The removal of TCE by Ag/S-ZVI was 90.4% within 20 min. The reaction rate constant Kobs of Ag/S-ZVI was 2.59 times or 1.85 times of nZVI or S-nZVI, respectively. Cycling experiments showed that Ag/S-ZVI had good recycling ability, and the removal rate of TCE reached 72.6% at the third cycle. The addition of Ag+ makes S-nZVI as an abundant and efficient source of reducing electrons. The Fe0 core can break C-Cl bonds by releasing electrons and the surface layer of Ag favors the transfer efficiency of electrons. Such study provides an efficient and robust ternary system for the remediation of TCE in groundwater. [ABSTRACT FROM AUTHOR]

Fenton-like oxidation processes are widely used to degrade recalcitrant organic pollutants, but are limited by narrow application pH and low reaction efficiency. This study investigated the synchronous activation of H2O2 and persulfate (PDS) by sulfidated zero valent iron (S-nZVI) in ambient conditions for Fenton-like oxidation of bisphenol S (BPS), an estrogenic endocrine-disrupting chemical. The activation of S-nZVI induced H2O2 or PDS could be greatly enhanced with the assistance of PDS and H2O2, respectively, even across a wide range of pH value (3–11). The first-order rate constant of S-nZVI/H2O2/PDS, S-nZVI/PDS and S-nZVI/H2O2 systems was found to be 0.2766 min−1, 0.0436 min−1, and 0.0113 min−1, respectively. A significant synergy between H2O2 and PDS was achieved when the PDS-H2O2 molar ratio was above 1:1, and where sulfidation promoted iron corrosion and decreased solution pH were observed in the S-nZVI/H2O2/PDS system. Radical scavenging experiments and electron paramagnetic resonance (EPR) investigations suggest that both SO4•− and •OH were generated and that •OH played a crucial role in BPS removal. Furthermore, four BPS degradation intermediates were detected and three degradation pathways were proposed in line with the HPLC-Q-TOF–MS analysis. This study demonstrated that compared to the traditional Fenton-like system, the S-nZVI/H2O2/PDS system could be a more efficient, advanced oxidation technology capable of being used across a broad pH range for emerging pollutants' degradation. [ABSTRACT FROM AUTHOR]

Goethite and pyrite are common iron minerals in oxic or anoxic environments, respectively, both minerals being major reservoirs for Nickel, a bio-essential element. Mineral transformation between goethite and pyrite is frequent owing to the alternation of oxic and anoxic conditions in sulfate-rich environments. This mineral transformation has been amply studied, but the effect of Ni on this transformation and its fate along it remain poorly understood. Sulfidation of Ni-free and Ni-containing (through adsorption or isomorphic substitution) goethites was thus studied experimentally by reacting goethite with dissolved S(-II) (molar Fe:S≈1:1). X-ray diffraction and associated Rietveld refinement, thermogravimetric analysis, scanning/transmission electron microscopy, X-ray absorption spectroscopy, and wet chemistry were used to monitor mineralogical evolutions and unravel Ni association with reaction products. After 44 days of sulfidation, about half of initial goethite converted to iron sulfides: thermodynamically stable pyrite (67%–93%) with minor contents of mackinawite (2%–15%) and greigite (5%–25%). Although the overall content of iron sulfides formed was essentially independent of Ni presence, Ni hampered the conversion from metastable iron sulfides (i.e., mackinawite and greigite) to pyrite (67%–78% vs. 93%, in the presence and absence of Ni, respectively). Pyrite formation from metastable sulfide precursors yielded a uniform Ni distribution in newly formed pyrite, regardless of the initial Ni association with goethite. Although no Ni was released to solution during pyrite formation, Ni incorporation to pyrite results in an increased risk of release to the environment as iron sulfides will be oxidized when exposed to air and water in supergene environments, leading to highly acidic conditions favoring Ni solubility and mobility. [ABSTRACT FROM AUTHOR]

Gas turbine materials often feature precipitates containing refractory metals to enhance their mechanical strength. This can make them susceptible to alloy-induced acidic fluxing whereby refractory elements increase the acidity of salt deposits. It is not clear to what degree degradation around alloy precipitates is caused by alloy-induced hot corrosion mechanisms, or the inability to develop a protective scale where precipitates are located. The effect of alloy-induced hot corrosion was isolated from the disruption of the protective-scale formation by adding particles of molybdenum to the 80/20 (Na/K)2SO4 deposit for a 'deposit re-coat' style hot corrosion test. The resulting morphologies were compared to samples exposed without the addition of molybdenum. Morphology changes were investigated using scanning electron microscopy with energy-dispersive X-ray mapping. Results show a mix of sulphidation and pitting. The effects of molybdenum additions appear more severe for MarM 509 compared to PWA 1483. [ABSTRACT FROM AUTHOR]

The increasing production and utilization of nano-based commercial products have resulted in a significant release of engineered nanoparticles (ENPs) in the environment. Upon their release into the aquatic systems, ENPs interact with a wide range of natural constituents and undergo a multitude of diverse transformation processes. The majority of these transformations entail physical, chemical, and biological transformations. This review provides a comprehensive evaluation of the investigations that have scrutinized the fate and transformation behavior of ENPs such as TiO2, ZnO, CuO, Ag, Fe3O4, NiO, SiO2, CeO2, quantum dots, and carbon nanotubes. The physicochemical properties of ENPs and the prevailing environmental conditions constitute the pivotal parameters governing the environmental fate and transformation of ENPs. These transformations are intertwined with a range of environmental aspects which includes aggregation, agglomeration, sedimentation, dissolution, reduction, oxidation, sulfidation, and adsorption. Thus, the insights gleaned from these studies may help to comprehend the behavior of transformed ENPs, including their environmental fate, bioavailability, and mechanisms of toxicity. Overall, forthcoming nanomanufacturing processes should thoroughly prioritize the considerations of health, safety, and environmental consequences, all while ensuring that the functionality of consumer products remains uncompromised. [ABSTRACT FROM AUTHOR]

Iron-based heterogeneous catalysts due to the environmental friendliness have been widely studied for activation of peracetic acid (PAA) for abatement of organic contaminants in the water and wastewater treatment. However, the slow reduction from Fe(III) to Fe(II) of the iron-based catalysts as the rate-limiting step results in the low PAA activation efficiency. With regard to the excellent electron-donating capability of the reductive sulfur species, sulfidized nanoscale zerovalent iron is proposed for PAA activation (simplified as the S-nZVI/PAA process) and the tetracycline (TC) abatement efficacy and mechanism of this process are elucidated. The optimal sulfidation ratio (S/Fe) of S-nZVI is 0.07, which exhibits superior performance in PAA activation for TC abatement with the efficiency of 80–100% in the pH range of 4.0–10.0. The radical quenching experiments and oxygen release measurements confirm that acetyl(per)oxygen radicals (CH3C(O)OO•) are the main radical contributing to TC abatement. The influence of sulfidation on the crystalline structure, hydrophobicity, corrosion potential, and electron transfer resistance of S-nZVI is evaluated. The main sulfur species on the S-nZVI surface are identified as ferrous sulfide (FeS) and ferrous disulfide (FeS2). The analysis by X-ray photoelectron spectroscopy (XPS) and Fe(II) dissolution suggest that the reductive sulfur species can accelerate the conversion from Fe(III) to Fe(II). In summary, the S-nZVI/PAA process exhibits application prospects for the abatement of antibiotics in the aquatic environments. [ABSTRACT FROM AUTHOR]

The hot corrosion behavior of Co-9Al-9.5W-xSi (where x = 0%, 0.1%, 0.5%, at.%) alloys in a salt mixture at 900 °C was investigated. The effect of Si on hot corrosion resistance was examined using corrosion kinetics. The surface morphology of the corrosion products was explored via SEM with EDS and the phase constituents were examined using XRD. The results revealed that hot corrosion occurred as a combination of both sulfidation and oxidation behavior. With the increase in Si content, the hot corrosion resistance of the alloy was capable of remarkable advancement. Corrosion scales on the three Co-based alloys were mostly comprised of Co3O4, CoO, CoAl2O4, CoWO4, and Al2O3. The hot corrosion mechanism for the Co-based alloy in the presence of 75 wt.% Na2SO4 and 25 wt.% NaCl deposits were analyzed. [ABSTRACT FROM AUTHOR]

One of the main challenges in the copper oxide processing industry is the application of flotation to reduce operating costs. Sulfidation-flotation is a commonly employed approach for floating oxide minerals using sulfidizers in order to sulfide the mineral’s surface. In this research work, an oxidized sample from the Qaleh Zari copper mine was used which was a high grade with 5.4% of copper (malachite and azurite). The prepared sample was subjected to mineralogical studies, and the obtained results indicated that the sample was oxidized. Malachite and azurite were the predominant minerals of copper oxide, and the predominant waste minerals were quartz and iron oxides (hematite and magnetite). The addition of sodium sulfide and flotation in four consecutive steps was a successful approach to meet the proper recovery and grade. Sodium sulfide, amyl potassium xanthate, sodium sulfide preparation time, and pH were selected as operating parameters using a central composite design (CCD). Also, by measuring the zeta potential, the electric charge of malachite was determined in different conditions after adding chemicals. Finally, under optimal conditions, the consumptions of sodium sulfide and amyl potassium xanthate, sodium sulfide preparation time, and pH value were 6790 g/t, 736 g/t, 10 minutes, and 9, respectively. By applying the mentioned conditions, a concentrate with a grade of 22.13%Cu and 90.51% recovery was achieved.