Search Results (143)

Although the mineralogical form of occurrence of critical metals is widely recognised as a key factor controlling their recovery during beneficiation, this relationship has rarely been verified directly on freshly mined ore and its primary beneficiation products from Central Asian polymetallic deposits. This raises the research question of how the mineralogical mode of occurrence of Bi, In, Cd, Co, Se, Te and Re governs their distribution between gravity and flotation products. Accordingly, the aim of this study was to establish how the mineralogical form of occurrence of these critical metals determines their distribution among gravity-concentration and flotation products, using ores from the Zhuantobe and Strezhanskoe deposits (Kazakhstan) as a case study. To this end, the mineralogical features and distribution patterns of critical metals during gravity and flotation beneficiation of polymetallic ores from these deposits were investigated by optical microscopy, X-ray diffraction, and SEM-EDS, while metal distribution among beneficiation products was determined by chemical analysis. Sphalerite, galena, pyrrhotite, and silver tellurides were identified as the main carriers of the critical metals, with bismuth occurring as an isomorphic admixture in sphalerite (3.69 wt.%) and galena (1.85 wt.%). During flotation, distribution was governed by mineralogical affinity: cadmium and indium were preferentially concentrated in the zinc concentrate (56.31% and 15.44% recovery, respectively), bismuth in the copper–lead concentrate (23.03%), and selenium and rhenium in the copper-bearing products (23.60% and 37.05%). Correlation analysis of the gravity-concentration products confirmed a close association of cadmium with sphalerite (R² = 0.9998), bismuth with galena and sphalerite (R² = 0.9674), and cobalt with iron-bearing sulfides (R² = 0.9144). These results demonstrate that the distribution of critical metals is governed primarily by their mineralogical form of occurrence rather than by bulk ore content, providing a basis for technologies for the complex processing of polymetallic ores. Full article

Iron ore mining is often assumed to pose a low soil-contamination risk because magnetite is dense and metal-poor. We tested this assumption around the Sokolov–Sarbai magnetite–skarn complex (Kostanay Region, Kazakhstan) by sampling soils at four settlements and a nearby background site, analyzing sixteen elements in pseudo-total and exchangeable forms, and comparing classical pollution indices with disaggregated US EPA health risk metrics on the same dataset. The two frameworks diverge sharply. Integrated indices (PLI, PERI) classify the area as low-risk, yet the child hazard index (US EPA cobalt reference dose) exceeds one at all four settlements, driven almost entirely by cobalt—a single, highly mobile element released from the late-stage sulfide paragenesis of the host skarn against an already cobalt-rich regional background. This relative result—cobalt as the dominant contributor and Rudny City as the most affected settlement—is robust to exposure-parameter variation and, at Rudny City and Konstantinovka, to unfavorable bioaccessibility assumptions. Carcinogenic risk stays within the acceptable range and reflects regional-background nickel and chromium rather than a mining increment. For single-element, regionally elevated contaminants, integrated indices can therefore understate a genuine child health hazard; adequate assessment requires mobile-fraction characterization and bioaccessibility-explicit risk computation. Full article

Transition-metal sulfides are promising electrode materials for high-performance supercapacitors but are often limited by poor conductivity, particle agglomeration, and insufficient active sites. Herein, Co-doped NiS₂ with tunable sulfur vacancies was directly grown on flexible carbon cloth via a facile one-step solvothermal method by systematically controlling sulfur source ratio, Ni:Co ratio, temperature, and reaction time. Structural analyses reveal that the optimized conditions of S:(Ni + Co) = 3:1, Ni:Co = 2:1, 160 °C, and 15 h promote the formation of phase-pure Co-doped NiS₂ hierarchical microspheres with enhanced crystallinity and abundant active sites from the synergistic interaction between Ni and Co. Consequently, the optimized electrode delivers an impressive capacitance of 1296 F g⁻¹ at a current density of 1 A g⁻¹, along with excellent rate performance, retaining more than 88% of its capacitance after 1500 charge/discharge cycles at current densities ranging from 2 to 20 A g⁻¹. This work highlights the critical role of synthesis parameter engineering in regulating defect chemistry, structure, and electrochemical performance in advanced energy storage applications. Full article

Cobalt occupies an irreplaceable strategic position in renewable energy and high-end advanced industries. As high-grade mineral resources gradually deplete, associated sulfide minerals have attracted increasing attention as alternative sources of cobalt. This study investigated a selective extraction of cobalt from low-grade cobalt-bearing pyrite using oxygen-pressure acid leaching. The Gibbs free energy (ΔG) of key chemical reactions in the leaching system was calculated to verify the thermodynamic feasibility of the process. The effects of critical parameters, including oxygen pressure, initial acidity, stirring speed, leaching time, and temperature, on cobalt leaching efficiency and phase transformation characteristics were systematically investigated. Under optimal conditions of oxygen pressure 1.5 MPa, H₂SO₄ initial acidity 7.36 g·L⁻¹ (0.82 mol/L), stirring speed 300 rpm, leaching duration 120 min, and temperature 230 °C, the cobalt leaching rate reached 98.2%, whereas the leaching rates of iron and aluminum were only 19.79% and 28.11%, respectively. Combined with SEM-EDS, XRD, and XPS characterization results, oxygen pressure acid leaching effectively destroyed the lattice structure of cobalt-bearing pyrite and liberates lattice-hosted cobalt, thereby facilitating efficient cobalt leaching. At high-temperature and oxygen pressure conditions, Fe³⁺ underwent hydrolysis and precipitated as hematite (Fe₂O₃) or hydronium jarosite (H₃O)Fe₃(SO₄)₂(OH)₆, enabling the selective extraction of cobalt. Aluminum in cobalt-bearing pyrite primarily occurred as the stable boehmite (AlOOH) phase, exhibiting excellent acid resistance and low dissolution during leaching. This study broadens the utilization pathway of low-grade cobalt resources and provides valuable insights and a scientific theoretical basis for the efficient treatment of cobalt-containing sulfide concentrates and tailings. Full article

Copper cobalt sulfide (Cu-CoS₂) nanoparticles (NPs) were synthesized via the co-precipitation method in the present study. The synthesized nanoparticles were employed as photocatalysts for the degradation of two hazardous dyes, Eosin B (EB) and Rhodamine B (RB), under sunlight irradiation. The synthesized nanoparticles were characterized using Energy Dispersive X-ray spectroscopy, Scanning Electron Microscopy, UV-Visible spectroscopy, Fourier Transform Infrared spectroscopy, and X-ray Diffraction analysis. The calculated optical band gap of Cu-CoS₂ was 2.06 eV, while the point of zero charge (PZC) was determined to be 7. The XRD results confirmed the crystalline nature of the Cu-CoS₂ nanoparticles with an average crystallite size of 28.23 nm. The catalyst exhibited higher photocatalytic degradation efficiency for EB than for RB in single-dye solutions. In contrast, the presence of EB in the binary dye mixture did not significantly influence the degradation of RB. The effects of various operational parameters, including dye concentration, pH, temperature, and catalyst dosage, were systematically investigated. The photocatalytic degradation efficiency of both dyes decreased with increasing initial dye concentration. Optimum degradation conditions for both single and binary dye systems were obtained at dye concentrations of 40:20 μM, pH 5 for EB, pH 9 for RB, and a temperature of 50 °C. The maximum degradation efficiencies achieved in single-dye solutions were 97% for RB and 92% for EB, whereas degradation efficiencies of 98% for RB and 82% for EB were observed in binary dye systems. Furthermore, first-order and second-order kinetic models were applied to evaluate the photodegradation process, and the experimental data showed better agreement with the second-order kinetic model. Full article

Alkaline nickel zinc batteries feature high safety, low cost and eco-friendly characteristics, making them highly promising for large-scale energy storage deployment. However, their practical application is severely constrained by the cathode’s electrical conductivity, available active sites, and cycling stability. Herein, vertical 2D hierarchical flake-like NiCoS_x arrays were in situ grown on nickel foam (NF) via a facile alkali-free solvothermal and in situ sulfidation approach. This highly interconnected and open porous flaky structure significantly shortens the ion diffusion pathways, exposes abundant redox-active sites, and accelerates electron transport, imparting excellent rate performance and superior long-cycle stability to the material. The optimized NiCoS_x/NF electrode achieves a high specific capacity of 323 mAh g⁻¹ at 0.5 A g⁻¹, along with excellent capacity retention capability. Assembled with a commercial Zn anode, the NiCoS_x/NF//Zn full battery delivers 124 mAh g⁻¹ at 3 A g⁻¹, and maintains 112.5% of the initial capacity after 500 cyclic tests. Moreover, the assembled NiCoS_x/NF//Zn full cell possesses a high energy density of 615.2 Wh kg⁻¹ along with a power density of 38.6 kW kg⁻¹ (based on the mass of positive electrode active materials). This unique vertical 2D open hierarchical structure plays a crucial role in enhancing the electrochemical performance of cobalt sulfide cathodes and provides valuable insights for the design of high-performance alkaline zinc-based battery electrodes. Full article

Seawater zinc–air batteries (SZABs) stand out as promising candidates for marine and offshore energy supply. However, their practical implementation is greatly restricted by tardy oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics at the air cathode, severe chloride ion-induced catalyst corrosion, and structural deterioration of traditional binder-containing electrodes in seawater media. Herein, we design and fabricate a binder-free integrated electrode consisting of carbon-supported iron phthalocyanine- modified star-like cobalt sulfide arrays directly grown on nickel foam. The optimal catalyst (0.3FePc-C/CoS) integrates the respective advantages of Fe single atoms and cobalt sulfide, exhibiting excellent ORR and OER activity, delivering a prominent half-wave potential of 0.89 V versus RHE, and exhibiting a low OER overpotential of 160 mV at 50 mA cm⁻² and robust stability in seawater. As a self-supported air cathode, the 0.3FePc-C/CoS-based battery attains a favorable open-circuit voltage reaching 1.48 V, prominent peak power density (126.4 mW cm⁻²), small charge–discharge potential polarization (0.52 V), excellent energy efficiency (68.8%) and extraordinary long-term cycling durability (>360 h). This work not only discloses a feasible synergistic modulation strategy for constructing high-performance bifunctional electrocatalysts but also provides a valuable reference for developing corrosion-resistant integrated air electrodes toward practical marine energy storage applications. Full article

The catalytic removal of refractory VOCs in gas–solid reactions usually suffers from the formation of toxic byproducts and catalyst deactivation. The advanced oxidation process (AOP) wet scrubber has recently attracted interest in VOCs purification due to its high efficiency and inhibited gaseous byproducts emission. MOFs/metal sulfides (termed M50C50) were designed to activate peroxymonosulfate (PMS) for toluene removal in a wet scrubber. The heterojunction interface synergistically couples MIL-100(Fe) and CoS for dual functions, the M50C50 enabled the rapid transfer the toluene from the gas phase to the aqueous phase, where they were subsequently mineralized by SO₄^•− and •OH radicals. The primary active sites responsible for PMS activation were identified as reducing sulfur species, along with low-valence cobalt and iron species. Over 90% of toluene were removed with a wide pH range, while •OH and SO₄^•− were involved in the mineralization of intermediates. The process showed high mineralization efficiency (75% CO₂ evolution) and effectively reduced the formation of toxic byproducts, underscoring its potential for minimizing secondary pollution risks. This work provides a novel route to designing composite catalysts for deep VOC oxidation via AOP wet scrubbers, greatly facilitating their use in environmental remediation. Full article

Recent studies have demonstrated the relative stability of undercoordinated hexanuclear cobalt sulfide nanoclusters (NCs) with different charge states. Considering that these small metal NCs have atomically precise structures and high reactivity due to the open shell of the transition metals, and provide selectivity toward ligand loss, they are a vital model for catalysis. In this paper, the electronic structures of these NCs are investigated. These NCs are then used as the reference state to analyze the catalytic properties with respect to hydrogen evolution reaction (HER) and CO₂ reduction (CO₂R). Further, to understand the effect of heteroatom incorporation, the geometry and reactivity of ten different metal dopants are analyzed. This work shows that the type of metal incorporation greatly affects the electronic structure and formation energies for ligand binding and catalysis. Particularly, the d-orbital occupancy in the cobalt atoms remains largely unchanged, while the heteroatom greatly influences the reactivity of the undercoordinated NCs. Most notably, this work highlights that transition metals in [Co₅MS₈(PEt₃)₅]¹⁺ NCs would competitively prefer electrochemical adsorption of H over COOH, while the main group metals prefer COOH adsorption. Full article

Sulfate roasting is a critical pyrometallurgical pre-treatment for extracting Cu and Co from low-grade Cu–Co–Fe sulfide ores, yet conventional phase diagrams provide limited quantitative guidance for process control. To address this gap, a multicomponent/multiphase thermodynamic equilibrium model based on Gibbs free energy minimization was developed to systematically investigate the oxidative roasting behavior of single sulfides (Cu₂S, CoS₂, FeS₂) and their ternary mixture, with respect to air supply, temperature, and total pressure. The model reveals that each sulfide follows distinct, temperature-dependent phase transformation pathways: Cu₂S forms the acid-leachable product CuO·CuSO₄ at temperatures ≤ 588 °C with a stoichiometric air supply of 11.9 mol, transitioning to oxides at ≥800 °C; CoS₂ converts completely to CoSO₄ below 727 °C and to CoO at higher temperatures; FeS₂ yields sulfate phases at low temperatures and iron oxides above 654 °C. In the ternary Cu₂S–CoS₂–FeS₂ system, competitive oxidation reactions produce refractory mixed oxides (CuO·Fe₂O₃, CoO·Fe₂O₃) whose formation is governed by temperature, air supply, and sulfide molar ratios. The results demonstrate that low-temperature roasting (≤641 °C) with precisely controlled air supply maximizes the formation of water-soluble sulfates, providing a quantitative thermodynamic basis for process optimization and enhanced recovery of Cu and Co from complex sulfide ores. Full article

The NiCo₂O₄/nickel cobalt sulfide (NiCoS) electrode was constructed on a nickel foam (NF) substrate using a combination of hydrothermal synthesis and constant potential electrodeposition. The NiCo₂O₄ prepared via an in situ hydrothermal method followed by calcination served as an intermediate layer, providing structural support and abundant active sites for the subsequent electrodeposition of the NiCoS top layer. The NiCoS loading amount was optimized by adjusting the deposition time. The optimized NiCo₂O₄/NiCoS electrode delivered an areal specific capacitance (Cs) of 6.94 F cm⁻² at a discharge current density of 2 mA cm⁻² with a coulombic efficiency of 98.85%. It retained 64.52% of its initial capacitance as the current density increased from 2 to 80 mA cm⁻² and exhibited an equivalent series resistance (R_ESR) of 1.06 Ω cm⁻². Furthermore, the NiCo₂O₄/NiCoS electrode retained 88.24% of its initial capacitance after 700 charge/discharge cycles, eventually stabilizing at 81.25% within 4000 cycles. Full article

The oxygen evolution reaction (OER), a key half-reaction in electrochemical water splitting, is limited by sluggish multi-electron transfer kinetics, starting extensive research into efficient, low-cost nanoscale electrocatalysts, particularly those based on nickel, cobalt, and iron, as well as mixed-metal, hybrid, and heteroatom-doped carbon-based metal-free systems, as presented here. Ni- and Co-based electrocatalysts show high efficiency for alkaline OER due to optimized nanostructures, surface modifications, heterostructure design, and multi-metal doping, which enhance activity, stability, and electronic properties. Their performance relies on precise atomic-level control of structure and synergistic interactions, enabling them to approach or rival noble-metal catalysts. Iron-based electrocatalysts are also promising due to their abundance, low cost, and flexible redox chemistry, forming active iron oxyhydroxide species during operation; however, their low conductivity requires structural and electronic optimization. Beyond Fe, Ni, and Co, copper-based compounds, zeolitic imidazolate framework-derived structures, and manganese phosphide–cerium oxide composites offer enhanced oxygen vacancies, tunable structures, and strong interfacial synergy. Furthermore, heteroatom-doped carbon materials incorporating nitrogen, phosphorus, or sulfur improve catalytic activity by modifying electronic structure, creating active sites, and enhancing charge transfer. Overall, careful control of composition, structure, and electronic properties enables the development of efficient, durable, and scalable noble-metal-free catalysts for OER. Full article

Over the past two decades, organic semiconductors have attracted significant research interest due to their advantageous features, including low-cost fabrication, lightweight properties, and portability, for photonic device applications. In this study, nickel sulfide doped with cobalt $(\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o})$ nanocomposites were successfully synthesized via a wet-chemical processing technique and used as a dopant in the active layer of thin-film organic solar cells (TFOSCs). The poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) blend was used as the active layer in this investigation. The devices were fabricated with $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites at 1 wt%, 2 wt%, and 3 wt% in the active layer to determine the optimal dopant concentration. However, the experimental evidence clearly showed that the solar cell’s performance depends on the concentration of the $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites. As a result, the highest power conversion efficiency (PCE) recorded in this experimental work was 6.11% at a 1% doping concentration, compared with 2.48% for the pristine reference device under AM 1.5G illumination (100 mW/cm²) in ambient conditions. The optical and electrical properties of the active layers are found to be strongly influenced by the inclusion of $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites in the medium. However, the device doped with 1 wt% $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposite exhibits the highest absorption intensity, consistent with the better performance observed in this study, which can be attributed to the localized surface plasmon resonance (LSPR) effect. The optical and morphological characteristics of the synthesized $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites were comprehensively analyzed using high-resolution transmission electron microscopy (HRTEM), high-resolution scanning electron microscopy (HRSEM), and additional complementary techniques. Full article

Hydrothermal cobalt (Co) deposits are a significant source of Co; however, the sources of Co and hydrothermal fluids for such deposits remain poorly understood. This study addresses this issue through an investigation of the geology, mineralogy, and in situ sulfur isotopes of the Qibaoshan Co-Pb-Zn-Cu deposit, a typical hydrothermal Co deposit in South China, to constrain the occurrence of Co and the sources of Co and hydrothermal fluids. Detailed scanning electron microscopy (SEM), TESCAN Integrated Mineral Analyzer (TIMA), and electron microprobe (EPMA) mapping analyses reveal that Co in the Qibaoshan deposit occurs predominantly as Co-bearing minerals in veinlet mineralization, mainly including cobaltite, skutterudite, and smaltite. EPMA elemental mappings reveal that cobaltite grains commonly show a compositional evolution from Ni-S-rich and As-Fe-poor cores to As-Fe-rich and Ni-S-poor rims. This evolution indicates a decrease in fluid temperature and Ni content, coupled with an increase in the As/S ratio during ore-forming processes. In situ S isotope analyses of various sulfides (pyrite, chalcopyrite, sphalerite, galena, and arsenopyrite) yield a wide range of δ³⁴S_V-CDT values from 0.24‰ to 19.08‰, with two dominant clusters at 2–5‰ and 15–17‰. This suggests two end-member sources for sulfur and hydrothermal fluids in the Qibaoshan deposit: magmatic and sedimentary sources. Arsenopyrite, which is closely associated with Co minerals, yields δ³⁴S_V-CDT values ranging from 2.17‰ to 5.99‰, pointing to a magmatic origin for Co in the Qibaoshan deposit. The Pb-Zn and Cu mineralization of the deposit was also likely mainly derived from magmatic sources, with the incorporation of sedimentary sulfur and fluids during the ore-forming processes. This study demonstrates that magmatic–hydrothermal fluids derived from depth can serve as sources of Co, even in hydrothermal deposits where no magmatic rock is exposed, which provides crucial implications for the metallogenic models and mineral exploration of hydrothermal Co deposits. Full article

The crystal structures of the cobalt(II) metal–organic frameworks or coordination networks of [Co(pdb)(DMF)] and [Co₂(pdi)(DMF)₃]·2(DMF)·H₂O (H₂pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid; H₄pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid; DMF = N,N-dimethylformamide) were synthesized solvothermally from cobalt(II) nitrate and the free acid of the linker in DMF. Systematic solvothermal screening demonstrated strong metal- and counterion-dependent framework formation, as crystalline coordination polymers were obtained exclusively from cobalt(II) nitrate, whereas other metal salts and cobalt(II) chloride or sulfate produced no crystalline materials. In catena-[(N,N-dimethylformamide)-μ₄-3,3′-(phenazine-5,10-diyl)dibenzoate-cobalt(II)], [Co(pdb)(DMF)], the Co₂ units, acting as secondary building units, are coordinated by four carboxylate groups from four linkers in a paddle-wheel arrangement, giving a three-dimensional (3D) network with cds (or CdSO₄) topology, in which the wide openings are filled by two symmetry-related nets to form a threefold interpenetrated structure. In catena-[tris(N,N-dimethylformamide)-μ₈-5,5′-(phenazine-5,10-diyl)diisophthalate-dicobalt(II)] bis(N,N-dimethylformamide) hydrate, [Co₂(pdi)(DMF)₃]·2(DMF)·H₂O, there are two different Co atoms, of which only Co₂ is connected to each of the four carboxylate groups of the tetracarboxylate linker and, thus, is responsible for 3D network formation. The network topology in [Co₂(pdi)(DMF)₃] is pts (or platinum(II) sulfide) when taking the Co₂ atom as a tetrahedral node and the linker as a square-planar fourfold node; however, this arrangement is inverse to the common square-planar metal and tetrahedral linker nodes found in PtS and most pts topologies. Full article