Search Results (5,777)

The presence of arsenic-bearing minerals in ores, notably enargite (Cu₃AsS₄), remains an unresolved issue for copper beneficiation processes, including those for porphyry copper deposits. In particular, several operational challenges remain for the selective flotation of enargite from copper–sulphide ores, as well as the selective leaching of arsenic from enargite in copper concentrates. This study addresses these challenges from the standpoint of mediator science, where structures with specific elemental compositions observed by several authors at the surface of enargite and chalcopyrite, under different conditions and analytical techniques, are compiled and analysed. Most probable surface species, observed using technologies measuring the outmost surface layer and occurring onto the mentioned minerals, are identified and compared to species predicted by classic thermodynamic calculations. The results indicate that for chalcopyrite the major species formed in acidic conditions is elemental sulphur, while copper oxide and iron oxides and oxy-hydroxides species predominate with increasing pH. For the case of enargite, a similar situation is observed at low pH values, although slightly acidic conditions appear as a less examined condition for this mineral. Some of the observed species were found to be consistent with thermodynamic predictions, while others are notably absent. Particularly, for the case of enargite researchers have reported the formation of arsenic (III) oxide at pH values as high as 13, and observation not predicted by Pourbaix diagrams. Thus As₂O₃ could be considered a metastable species at highly alkaline conditions, which opens an option to beneficiation from froth flotation. Interestingly, at the same pH condition, iron oxide and oxyhydroxides species predominate at the surface of chalcopyrite. Therefore, applying the mediator concept, the initial alkaline flotation of sulphide ores turns into an oxide flotation case. Full article

Phase and band gap engineering of (CdS)_x(CuInS₂)_1−x nanomaterials is critical for their potential applications in photovoltaics and photocatalysis, yet it remains a challenge. Here, we report a precursor-mediated colloidal method for phase-control synthesis of alloyed (CdS)_x(CuInS₂)_1−x nanocrystals with tunable band gap. When CuCl, InCl₃, and Cd(AC)₂·2H₂O are used as the respective cation sources, wurtzite-structured alloyed (CdS)_x(CuInS₂)_1−x nanocrystals can be synthesized with a tunable optical band gap ranging from 1.56 to 2.45 eV by directly controlling the molar ratio of the Cd precursor. Moreover, using Cu(S₂CNEt₂)₂, In(S₂CNEt₂)₃, and Cd(S₂CNEt₂)₂ as cation sources results in alloyed (CdS)_x(CuInS₂)_1−x nanocrystals with a zinc-blende structure, demonstrating that the optical band gap of these nanocrystals can be compositionally tuned from 1.50 to 1.84 eV through precisely adjusting the molar ratio of Cd precursor. The results were validated through a comprehensive characterization approach employing XRD, TEM, HRTEM, STEM-EDS, XPS, UV-vis-NIR absorption spectroscopy, and Mott–Schottky analysis. Full article

The photocatalytic degradation of Crystal Violet (CV) using ZnO-based nanomaterials presents a promising solution for addressing water pollution caused by synthetic dyes. This review highlights the exceptional efficiency of ZnO and its modified forms—such as doped, composite, and heterostructured variants—in degrading CV under both ultraviolet (UV) and solar irradiation. Key advancements include strategic bandgap engineering through doping (e.g., Cd, Mn, Co), innovative heterojunction designs (e.g., n-ZnO/p-Cu₂O, g-C₃N₄/ZnO), and composite formations with graphene oxide, which collectively enhance visible-light absorption and minimize charge recombination. The degradation mechanism, primarily driven by hydroxyl and superoxide radicals, leads to the complete mineralization of CV into non-toxic byproducts. Furthermore, this review emphasizes the emerging role of Artificial Neural Networks (ANNs) as superior tools for optimizing degradation parameters, demonstrating higher predictive accuracy and scalability compared to traditional methods like Response Surface Methodology (RSM). Potential operational challenges and future directions—including machine learning-driven optimization, real-effluent testing potential, and the development of solar-active catalysts—are further discussed. This work not only consolidates recent breakthroughs in ZnO-based photocatalysis but also provides a forward-looking perspective on sustainable wastewater treatment strategies. Full article

This study examined the effects of dielectric barrier discharge (DBD) plasma and copper oxide nanoparticles (CuO NPs) on rice seed quality, seedling growth, and fungal inhibition. Sanpatong 1 rice seeds were treated with DBD plasma at three exposure durations (0.4, 0.6, and 0.8 s/cm) and coated with CuO NP solutions at five concentrations (0, 0.02, 0.04, 0.06, and 0.08 M). The experiment followed a split-split-plot design within a randomized complete block design (RCBD), with storage time (0, 2, 4, and 6 months) as the main plot factor. Plasma etching improved seed surface wettability, while CuO NPs increased copper uptake and promoted growth at 0.04–0.06 M but caused toxicity at 0.08 M. Combined treatments suppressed Rhizopus sp. and Rhizoctonia solani, though Aspergillus spp. were less affected. Seed quality declined after six months of storage, likely due to oxidative stress. The best results were obtained with 0.6 s/cm plasma and 0.06 M CuO NPs, maximizing germination, vigor, and seedling growth without toxicity, demonstrating their potential as practical tools for improving rice seed quality and pathogen management. Full article

Anion exchange membrane fuel cells (AEMFCs) represent a promising class of clean energy devices, with their performance being critically dependent on the efficiency of the cathode oxygen reduction reaction (ORR) catalyst. Manganese-cobalt spinel (Mn_1.5Co_1.5O₄, MCS) has been demonstrated to be a highly active ORR catalyst. Herein, we report a strategy of incorporating Cu (MCCS) and Fe (MCFS) into MCS to form ternary spinel oxides for tuning ORR activity. Among them, MCS exhibits the best ORR performance, with a half-wave potential (E_1/2) of 0.736 V vs. RHE in 0.1 M KOH and a peak power density (PPD) of 248.3 mW·cm⁻² for the fuel cell test. In contrast, MCCS and MCFS show divergent behaviors in a rotating disk-ring electrode (RRDE) and fuel cell tests. X-ray diffraction (XRD) analyses and X-ray photoelectron spectroscopy (XPS) analyses reveal that the introduction of Cu²⁺ and Fe³⁺ induces a phase transformation in the spinel structure, leading to a reduction in oxygen vacancies and an increase in the valence state of Mn, thereby degrading catalytic activity. However, the incorporation of these elements also modulates the hydration capability of the catalysts, which is critical for the ion and charge transfer in the fuel cell environment and has been validated in the distribution of relaxation time (DRT) analysis of the fuel cell test. This study provides a valuable strategy for designing and synthesizing low-cost, highly efficient, and stable ternary spinel electrocatalysts for AEMFC applications, and bridges the gap between RRDE evaluation and fuel cell testing through DRT analysis. Full article

The truncated octagonal cuprous oxide photocatalysts were synthesized in the presence of polyvinylpyrrolidone. Zn-doped Cu₂O photocatalysts were successfully synthesized with different ZnSO₄/CuSO₄ ratios. The effects of Zn doping on the light absorption, morphology, separation of photogenerated charge carriers, and hydrogen production performance of the photocatalyst were investigated. The size and morphology of the Zn-doped Cu₂O-based nanomaterials change with increasing dosages of zinc sulfate dopant. Zn doping resulted in a reduction in crystallite size, a change in morphology, and a decrease in the size of the nanomaterial. The hydrogen production activity of the Zn-Cu₂O photocatalyst Zn-Cu₂O-2 with optimized dopant content can reach 9690 μmol h⁻¹g⁻¹. The enhanced photocatalytic activity of Zn-doped Cu₂O photocatalyst is achieved through significantly improved electron-hole separation, which is maximized at an optimal Zn dopant concentration. Full article

The high stability of chelated heavy metal complexes like Cu-EDTA renders their effective removal from industrial wastewater a persistent challenge for conventional treatment processes. This study developed a sustainable and high-performance CuO-modified biochar (CuO-BC) from corn straw waste for peroxydisulfate (PDS)-activated degradation of Cu-EDTA. Through systematic optimization, hydrothermal co-precipitation using copper acetate as the precursor followed by secondary pyrolysis at 350 °C was identified as the optimal synthesis strategy, yielding a dandelion-like structure with highly dispersed CuO on the BC surface. It achieved 93.8% decomplexation efficiency and 57.3% TOC removal within 120 min under optimized conditions, with an observed rate constant (K_obs) of 0.0220 min⁻¹—five times higher than BC. Comprehensive characterization revealed that CuO-BC possessed a specific surface area and pore volume of 4.36 and 15.5 times those of BC, along with abundant oxygen-containing functional groups and well-exposed Cu–O active sites. The enhanced performance is attributed to the synergistic effects of hierarchical porosity facilitating mass transfer, uniform dispersion of CuO preventing aggregation, and surface functional groups promoting PDS activation. This work presents a green and scalable approach to transform agricultural waste into an efficient metal oxide-BC composite catalyst, offering dual benefits of environmental remediation and resource valorization. Full article

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering of dense ceramic bodies in relatively low temperatures (up to 1100 °C) was possible with the usage of CuO-TiO₂-Nb₂O₅-based additive, together with an intense milling process. By using the XRD method, the formation of dominant α-Al₂O₃ and m-ZrO₂ phases with small concentrations of secondary ones in experimental samples was confirmed. SEM studies showed that uniform distribution of components in the composite was achieved in samples sintered from intensively milled powders. The significant increase in the values of Vickers hardness and biaxial flexural strength (by 2.6 times) in samples from intensively milled powders at a sintering temperature of 1050 °C was explained by reduced porosity, improved grain distribution, and the formation of the t-ZrO₂ phase in the alumina-reinforced composite. The study clearly showed high potential of the proposed low-temperature sintering method for zirconia-toughened aluminum oxide, which can be used in manufacturing of advanced ceramics. Full article

Rare-earth barium copper oxide (REBCO) high-temperature superconductors, owing to their ability to maintain high critical current density (J_c) under liquid-nitrogen-temperature and high-magnetic-field conditions, are widely regarded as one of the most promising material systems among all superconductors. This review systematically summarizes fabrication strategies for REBCO coated conductors, with a focus on pulsed laser deposition (PLD) for achieving high-quality epitaxial growth with precise composition control. To enhance in-field performance, strategies for introducing artificial pinning centers (APCs) are examined, including rare-earth element doping, substrate surface decoration, and nanoscale secondary phase incorporation. The mechanisms of vortex pinning from different dimensional defects and their synergistic effects are compared. Finally, we suggest potential future directions aimed at further enhancing the superconducting properties. Full article

Discarded NdFeB permanent magnets will become a significant source of rare earth elements (REEs) in the future. Electric vehicle (EV) motors utilize 2–5 kg of NdFeB magnets, and researchers are prioritizing the development of suitable extraction technologies. The objective of our research is to separate metal materials (Al, Cu, Fe and FEEs) from EV motors, based on their melting temperatures. REE magnets that pose the greatest challenge are melted together with the electrical steel of the motor, and the potential for extracting REEs in a selective manner from the molten steel was examined based on their significant oxidation potential using FeO–SiO₂ compounds, which act as an oxidizing slag-forming agent, to test the extraction method. Fayalite (2FeO·SiO₂) is the most easily created and ideal eutectic compound for carrying oxygen (FeO) and forming slag (${\mathrm{S}\mathrm{i}\mathrm{O}}_4^{4^{-}}$), typically generated during copper smelting. In this experiment, copper slag was used and the results were compared to a smelting test, which had previously used a synthesized fayalite flux as a model. The smelting test, utilizing synthesized fayalite flux, yielded a 91% Nd recovery rate. The Nd recovery rate in the smelting test with copper slag hit a high of 64.81%, influenced by the smelting’s holding time. The steel contained 0.08% Nd. Iron was recovered from the copper slag at a rate of 73%. During the smelting test, it was observed that the reaction between Nd₂O₃ and the Al₂O₃ crucible resulted in the formation of a layer on the surface of the crucible, diffusion into the crucible itself, and a subsequent reduction in the efficiency of Nd recovery. Full article

Low-temperature superconductivity has been known since 1957 to be described by BCS theory for effective single-band metals controlled by the density of states at the Fermi level, very far from band edges, the electron–phonon coupling constant l, and the energy of the boson in the pairing interaction w₀, but BCS has failed to predict high-temperature superconductivity in different materials above about 23 K. High-temperature superconductivity above 35 K, since 1986, has been a matter of materials science, where manipulating the lattice complexity of high-temperature superconducting ceramic oxides (HTSCs) has driven materials scientists to grow new HTSC quantum materials up to 138 K in HgBa₂Ca₂Cu₃O₈ (Hg1223) at ambient pressure and near room temperature in pressurized hydrides. This perspective covers the major results of materials scientists over the last 39 years in terms of investigating the role of lattice inhomogeneity detected in these new quantum complex materials. We highlight the nanoscale heterogeneity in these complex materials and elucidate their special role played in the physics of HTSCs. Especially, it is highlighted that the geometry of lattice and charge complex heterogeneity at the nanoscale is essential and intrinsic in the mechanism of rising quantum coherence at high temperatures. Full article

Soil toxicity resulting from either natural or anthropogenic heavy metal contamination was evaluated through a nitrifying bacteria bioassay focused on the inhibition of oxygen consumption. Every contaminated soil sample inhibited the nitrifying bacteria bioassay, with inhibition levels ranging from 71% to 100%. The optimal conditions for maximizing O₂ consumption during the test procedure were established as follows: a test culture volume of 1 mL, a soil sample weight of 1 g, a rotation rate of 100 revolutions per minute, and a reaction duration of 48 h. In low- or uncontaminated soils, oxygen consumption ranged from 3.2 mL to 3.0 mL from a headspace volume of 1 mL filled with O₂. In contrast, contaminated soils exhibited a lower range, with values between 0.1 mL and 1.0 mL. EC50 levels for NB O₂ consumption were: Cr⁶⁺ 1.21 mg/kg; Cu²⁺ 6.92 mg/kg; Ag⁺ 8.38 mg/kg; As³⁺ 8.99 mg/kg; Ni²⁺ 10.35 mg/kg; Hg²⁺ 11.01 mg/kg; Cd²⁺ 31.33 mg/kg; Pb²⁺ 129.62 mg/kg. Values for inherent test variability (CVi), variation resulting from the natural characteristics of soil (CVns), and minimal detectable difference (MDD) were found to range between 1.6% and 4.7%, 7.8% and 14.6%, and 2.9% and 5.9%, respectively. A 10% toxicity threshold was set as the maximal tolerable inhibition (MTI) for effective soil toxicity assessment. Nitrifying bacteria bioassays offer a fast, affordable, and user-friendly tool for real-time soil toxicity assessment, boosting soil health monitoring and ecosystem protection. Full article

Non-enzymatic glucose sensing has attracted considerable interest as a promising alternative to enzyme-based sensors, addressing limitations such as poor stability and high cost. To overcome the challenges of expensive noble metals and the inherent issues of pure copper oxide (CuO), including low conductivity and aggregation tendency, this study developed a composite sensing material based on two-dimensional CuO nanosheets decorated with gold nanoparticles (Au NPs). A series of Au/CuO nanocomposites with varying Au loadings were synthesized through a combined hydrothermal and in situ reduction approach. Systematic electrochemical characterization revealed that the composite with 7.41 wt% Au loading exhibited optimal sensing performance, achieving sensitivities of 394.29 and 257.14 μA·mM⁻¹·cm⁻² across dual linear ranges of 5–3550 μM and 4550–11,550 μM, respectively, with a detection limit of 10 μM and a rapid response time of 3 s. The sensor also demonstrated selectivity against common interferents as well as long-term stability. This work highlights the importance of precise noble metal loading control in optimizing sensor performance and offers a feasible material design strategy for developing high-performance non-enzymatic glucose sensors. Full article

Background: The increase in potentially toxic elements (PTEs) in the soil is worrying, especially in agricultural soils due to the bioaccumulation factor. Copper (Cu) and iron (Fe) are micronutrients, responsible for important functions in the plant body, but the high availability of these elements in the soil can cause soil contamination and toxicity in plants; consequently, they can be considered PTEs. Objectives: The focus of this study is to understand the physiological responses (pigments, gas exchange, growth, biomass, accumulation) of Canavalia ensiformis to high levels of Cu and Fe in the soil, in isolation, and to identify which PTE is most harmful to its development. Methods: Two experiments (Cu and Fe) were conducted simultaneously in a greenhouse. Treatments of 50, 150, 250, and 350 mg dm⁻³ of soil for each element (CuSO₄*5H₂O and FeSO₄*7H₂O) were incorporated into the soil (Oxisol) of each experimental unit (4 dm³ pot), in addition to the control. C. ensiformis seeds were sown directly in soil enriched with Cu and Fe, respectively, and after emergence they were cultivated for 90 days. Results: Changes in chlorophyll levels caused direct effects on gas exchange, shoot biomass, root development, nodulation, and total plant biomass. The tolerance of the species is dependent on chlorophyll levels and gas exchange. There was accumulation of both PTEs in the roots and low translocation to the shoot. Conclusions: The plants were tolerant to Fe treatments; however, they were not tolerant to Cu treatments (T150–T350). Excess Cu was more detrimental to plant development. Full article

During active brazing of alumina ceramics, active elements react with the ceramic to form a reaction layer, which has significant influence on the mechanical property of the brazed joint. However, the composition and formation mechanism of this layer remain unclear among researchers. To fill this gap, different brazing temperatures (900–1100 °C) and heating rates (2.5 °C/min and 10 °C/min) were used to braze 95% Al₂O₃ ceramics and a Kovar 4J34 alloy using a Ag-Cu-2Ti active brazing filler, and the microstructure and mechanical properties of the joints were investigated. The results show that the joint could be divided into five layers: Al₂O₃, ceramic-side reaction layer, filler layer, Kovar-side reaction layer, and Kovar. The ceramic-side reaction layer could be further divided into a Ti-O-rich layer and an intermetallics (IMC)-rich layer, and the Kovar-side reaction layer consists of TiFe₂ particles, Ag-Cu eutectic, and the remaining Kovar. A belt-like TiFe₂+TiNi₃ IMC could be found in the filler layer. Increasing the brazing temperature enlarged the belt-like TiFe₂+TiNi₃ IMC in the filler layer and increased the thickness of the IMC-rich layer in the ceramic-side reaction layer, but had no significant effect on the thickness of the Ti-O-rich layer in the ceramic-side reaction layer. A lower heating rate (2.5 °C/min) was found to suppress the formation of the IMC-rich layer and shift the fracture location in shear tests from the ceramic-side reaction layer to the filler layer, indicating that the strength of the ceramic-side reaction layer was enhanced by controlling the formation of the IMC-rich layer. A maximum shear strength of 170 ± 61 MPa was obtained at a heating rate of 2.5 °C/min and a brazing temperature of 940 °C. Full article