Search Results (160)

This article is devoted to the development of a combined sulfation method (CSM) for processing low-grade copper-sulfide concentrates with a copper grade of 0.34–3.5%. The relevance of the study is driven by the depletion of Kazakhstan’s high-grade copper deposits and the need to incorporate off-balance sulfide raw materials into processing. CSM is based on the spatial separation of two thermally coupled zones in the filter bed of a shaft furnace: a zone of endothermic sulfation of sulfide minerals with ammonium hydrosulfate at 360–650 °C and a zone of exothermic oxidative roasting of residual sulfur at 640–660 °C. Excess oxidation heat compensates for the thermal losses of sulfation, ensuring an autogenous process without sintering of the charge. Flotation enrichment of off-balance ore from the Annenskoye deposit yielded a concentrate with a Cu grade of 7.59% and a copper recovery of 89.13–92.13%. Thermodynamic modeling was used to validate the temperature conditions for sulfation of individual minerals, and analytical relationships were developed for calculating reagent consumption and sulfur distribution. Laboratory tests confirmed the adequacy of the calculation model; the discrepancy between calculated and experimental data did not exceed 1.5%. The feasibility of regenerating ammonium hydrosulfate and extracting copper from the processed products was demonstrated. A basic flow chart for waste-free processing of low-grade copper-sulfide raw materials was proposed. Full article

In X-ray imaging, tissue scattering is an important factor that degrades image clarity, especially using a portable gridless X-ray imaging device. This study focuses on using Monte Carlo simulation to quantify the effect of scatter radiation on image resolution, by analyzing the point spread function (PSF) and the corresponding modulation transfer function (MTF). Lateral energy absorption profiles in tissue and a cesium iodide (CsI) scintillator were calculated at different X-ray tube voltages (70–90 kV) and filter configurations. Results showed that 85.7% of the total scattered radiation is concentrated at a distance of 4 cm from the central axis for the tissue and 67.37% for the CsI scintillator. The MTF remained high at low spatial frequencies (23% at 0.04 cycles/cm) but dropped at mid frequencies (0.015–0.025 at 0.3–0.6 cycles/cm) and was almost zero at high frequencies (0.004 at 0.8 cycles/cm), indicating loss of detail due to scattering. Increasing the thickness of the filter or adding a copper (Cu) filter reduced the contrast at low spatial frequencies (from 23% to 21%). The study quantitatively investigated the MTF degradation in portable X-ray imaging devices without grid, due to scatter. These results may aid in the development of scatter correction algorithms to improve image quality without the need for an anti-scatter grid. Full article

High-altitude mine wastelands in Southwest China present formidable challenges for ecological rehabilitation due to extreme climatic stressors and multi-element contamination. Ecological restoration is closely related to soil environment. However, the mechanism by which parent material-induced heterogeneity governs spontaneous vegetation succession is still poorly understood. We established 36 plots (216 quadrats) to investigate the soil physical and chemical properties and vegetation restoration of propylite, porphyry and siltstone in the Xifanping Copper Mine, Sichuan Province. Furthermore, fifteen metal/metalloid elements (Au, Ag, Mo, W, Cu, Pb, Zn, Hg, As, U, Se, Cr, Sn, Ti, Total Fe₂O₃), soil pollution and vegetation structure were evaluated. The study area exhibited severe composite pollution (mean Nemerow integrated pollution index = 8.09), primarily driven by Au, Ag, Mo, W, and Cu. Vegetation surveys identified 34 vascular plant species from 12 families. Propylite-derived substrates supported significantly higher species richness, Shannon–Wiener diversity, and soil organic matter than porphyry and siltstone. Redundancy analysis (RDA) identified soil organic matter (SOM) and bulk density (BD) as dominant environmental filters, with SOM explaining 14.03% of community variance (p < 0.01). Two native pioneers, Potentilla supina and Cynoglossum wallichii, were identified as specialized uranium (U) accumulators with bioconcentration factors of 13.39 and 4.49, respectively. Lithological inheritance dictates early successional trajectories by influencing edaphic structure and nutrient bioavailability. The identified U-accumulating species provide a valuable genetic resource for implementing Assisted Natural Regeneration (ANR) and developing sustainable phytoremediation strategies in contaminated alpine ecosystems. Full article

The geoelectrochemical extraction method is effective for locating deep concealed deposits, but research on the particle size distribution of its anomaly-causing substances remains limited. To address this, 20 sampling points were established along the No. 20 exploration profile at the Tongjiangling Copper Deposit in Jiangxi Province. Using consistent technical conditions, geoelectrochemical measurements were compared across filter membranes/papers with pore sizes of 0.22 μm, 0.45 μm, 1 μm, 3 μm, and qualitative medium-speed filter paper (approx. 20–30 μm). The results are as follows: (1) The 20–30 μm filter paper effectively detected anomalies corresponding to both shallow and deep concealed ore bodies, whereas smaller pore sizes only revealed shallow ore bodies. (2) Element content and anomaly contrast were significantly higher with the 20–30 μm filter paper compared to smaller pore sizes. (3) Geoelectrochemical anomalies originate from various surface soil substances, which may exist independently or be adsorbed onto particles of different sizes. The applied electric field mobilizes these charged particles, enabling their adsorption onto the collector and acquisition of deep mineralization anomalies. (4) For similar landscapes and deposit types, using filter paper with a pore size of approximately 20–30 μm is recommended to effectively capture deep ore body anomalies while reducing analytical complexity. Full article

The objective of this research was to optimize a technological package for the biosorption of heavy metals in water, using agricultural waste activated with lemon juice, as a sustainable development alternative. Heavy metals such as lead, cadmium, copper, and chromium were characterized in two stages (field and laboratory conditions) using the American Public Health Association (APHA) method, and morphological characterization was performed using electron scanning techniques. Cocoa pod husk (CPH) and banana stem (BS) waste was collected with the informed consent of the native communities to obtain charcoal activated with lemon juice (LJ). In addition, a portable filter was designed that could be adapted to the native communities. The efficiency and validation of the filter were also calculated in the field. Statistical analysis was performed using Student’s t-test and Pearson’s correlation. The results show a significant reduction in lead from 0.209 mg/L to 0.02 mg/L. With regard to morphological characterization, more compact structures were observed after activation with BS, favoring the absorption of heavy metals. The correlations were positive for copper and lead (1.000), evidently due to the alteration of anthropic factors. The efficiency of the cocoa filter reached 87.48% and that of the banana stem reached 88.77%. For the cadmium, copper, and chromium parameters, the values obtained were within the maximum permissible limit (LMP). The validation of the filters showed that 80% of the population agrees with using the filters and hopes for their large-scale implementation. These findings represent a new alternative for native communities and a solution to the problem of heavy metals in drinking water. Full article

This paper analyzes three forecasting methods for commodity spot prices and applies them to copper prices. The first method uses futures prices from either LME or COMEX. The second method uses analysts’ consensus expectations, reported by Bloomberg. The third method jointly uses futures and analysts’ expectations as inputs to a multifactor stochastic pricing model, with time-varying risk premiums that smooth its data using the Kalman filter. All three alternatives are compared with the well-known no-change forecast benchmark and with each other. The main finding is that analysts’ expectations are a valuable source of data for forecasting copper prices. Also, when futures prices are relatively higher than spot prices, the model presented is the best alternative for forecasting copper prices at any horizon up to 24 months, and when prices are relatively lower than spot prices, the model is the best alternative for long-term forecasts and for LME futures prices for 1 to 12 months. Full article

Industrial electric motors powered by variable frequency drives (VFDs) offer better controllability as compared to the conventional sinusoid-fed motors. However, the switching transients of VFDs induce shaft voltage in electric motors, which can lead to bearing failure. This may cause the machine to shut down and pose a serious threat to the system’s reliability. Several shaft voltage mitigation strategies are suggested in the literature, including insulated bearings, grounding brushes, copper shields, and filters. Although mitigation strategies have been extensively studied, shaft voltage signal processing remains relatively underexplored. This review introduces diffusion models (DMs), a new generative learning technique, as an effective solution for processing shaft voltage signals. These models are good at reducing noise, handling uncertainty, and capturing complex patterns over time. DMs offer robust performance under dynamic conditions as compared to traditional machine learning (ML) and deep learning (DL) techniques. In summary, the review outlines the sources and causes of shaft voltage, its existing mitigation strategies, and the theory behind DMs for shaft voltage analysis. Thus, by combining insights from electrical engineering and artificial intelligence (AI), this work addresses an important gap in the existing literature and provides a strong path forward for improving the reliability of industrial motor systems. Full article

Enhancement methods based on first-order derivatives are well established tools for gravity and magnetic data processing. Higher-resolution filters have been developed using high-order derivatives, but they are generally more sensitive to noise. Based on a transformation that sharpens the instantaneous phase of the complex analytic signal, which corresponds to the tilt angle map, we obtain an enhancement filter that improves the resolution of the total horizontal gradient (THG) without the need for additional derivative calculations. The steps of the proposed method are as follows: (1) compute the horizontal and vertical derivatives of the data; (2) compute the tilt angle and the analytic signal amplitude; (3) apply a sigmoidal-type transformation to the tilt angle; and (4) reconstruct the THG from the analytic signal amplitude and the transformed tilt angle. The reconstructed THG provides sharper boundary estimates than the true THG, as qualitatively shown with noise-corrupted synthetic data and aeromagnetic data from the Seival copper mining area in Caçapava do Sul, Brazil. Full article

Biofungicide products are a rapidly expanding sector of the plant protection market. Powdery mildew of tomato (Solanum lycopersicum), caused by Erysiphe neolycopersici, can result in significant yield loss in high tunnel (HT) tomato production. Copper-based fungicides are heavily used in HTs, especially those in certified organic production, to control powdery mildew and other fungal diseases. Reliance on copper can lead to its overuse, subsequent resistance development in pathogens, and accumulation of high amounts of copper in the soil. In this study, we evaluated two bio-product alternatives to copper for efficacy against powdery mildew in an organic HT tomato production system over three growing seasons. These alternatives were a commercial biofungicide containing Bacillus subtilis GB03 and a filtered and unfiltered microbial fermentation product (F-MFP and UF-MFP, respectively). UF-MFP was a proprietary blend of yeast cell walls and inactive fermentation media, whereas F-MFP was processed to remove any particles larger than 0.2 μm. The HT-grown tomato plants were inoculated with E. neolycopersici (10⁴ conidia/mL) and three to five foliar applications of biofungicide were made per season. Powdery mildew severity was lower with MFPs compared to the water-treated inoculated treatment and B. subtilis, although this was not always statistically significant (p = 0.05). At assessment dates where statistically significant difference among treatments were observed, the MFP treatments were generally equivalent to the cuprous oxide standard. These results suggest that MFP may be a suitable alternative or alternation partner to copper-based products currently in use in HT tomato systems affected by powdery mildew. Full article

In the application of ceramic dielectric filters, to achieve electromagnetic shielding of signals and subsequent integrated applications, it is necessary to carry out metallization treatment on their surfaces. The quality of metallization directly affects the performance of the filter. However, when in use, the filter may encounter harsh environmental conditions. Therefore, the surface-metallized film needs to have strong corrosion resistance to ensure its long-term stability during use. In this paper, Cu films and copper–chromium alloy films were fabricated on Si (100) substrates and BaTiO₃ ceramic substrates by HiPIMS technology. The effects of different added amounts of Cr on the microstructure, electrical conductivity, and corrosion resistance of the Cu films were studied. The results show that with an increase in Cr content, the preferred orientation of the (111) crystal plane gradually weakens, and the grains of the Cu-Cr alloy film gradually decrease. The particles on the film surface are relatively coarse, increasing the surface roughness of the film. However, after doping, the film still maintains a relatively low surface roughness. After doping with Cr, the resistivity of the film increases with the increase in Cr content. The film–substrate bonding force shows a trend of first increasing and then decreasing with the increase in Cr content. Among them, when the Cr content is 2 at.%, the film–substrate bonding force is the greatest. The Cu-Cr alloy film has good corrosion resistance in static corrosion. With the increase in Cr content, the Tafel slope of the cathode increases, and the polarization resistance R_p also increases with the increase in Cr content. After the addition of Cr, both the oxide film resistance and the charge transfer resistance of the electrode reaction of the Cu-Cr alloy film are greater than those of the Cu film. This indicates that the addition of Cr reduces the corrosion rate of the alloy film and enhances its corrosion resistance in a NaCl solution. 2 at.% Cr represents a balanced trade-off in composition. While ensuring the film is dense, uniform, and has good electrical conductivity, the adhesion between the film and the substrate is maximized, and the corrosion resistance of the Cu film is also improved. Full article

This study evaluates the use of seawater and continental water in tailings thickening and copper flotation at laboratory scale, focusing on water reuse in mining operations in arid regions. The tailings had a mean particle size of 10 µm, with 75% < 50 µm, and a specific weight of 2.64 g/cm³. Seawater contained significantly higher ion concentrations Na⁺ 10,741 ppm, Mg²⁺ 1245 ppm, and Ca²⁺ 556 ppm compared with continental water (187, 32, and 127 ppm, respectively), which negatively affected polymer performance. Sedimentation tests showed that the anionic polymer (A3) increased settling rates by 33 times with continental water at 40 g/t, while with seawater the increase was 31 times at 60 g/t. In column thickener tests, discharge solids reached 65% with continental water and 62% with seawater, representing an annual reduction of ~17,000 m³ of recovered water when seawater is used. Consistency tests indicated that achieving slump <20% required 75% solids with continental water and 77.5% with seawater. With dewatering polymers, doses of 200 g/t achieved ~70% solids and slump values near 50%, surpassing column thickener performance. Primary flotation results showed that recirculated and filtered seawater improved copper recovery by 3–5% compared with fresh seawater, due to partial removal of interfering ions. In contrast, recirculated and filtered continental water reduced recovery by 2–4%, likely because of residual polymer effects on mineral surfaces. These findings highlight the importance of polymer selection and dosage optimization to ensure efficient water recovery and sustainable flotation performance under varying water chemistries. Full article

Copper ions (Cu²⁺), indispensable in physiological processes yet toxic at elevated concentrations, require sensitive on-site monitoring. Here, a portable fluorescent sensing film (Y-CDs@BCM) was fabricated by anchoring yellow-emitting carbon dots (Y-CDs) into bacterial cellulose films, which enables rapid and sensitive detection of Cu²⁺ in complex real-world samples. The yellow fluorescent carbon dots (Y-CDs) were synthesized with the aid of o-phenylenediamine and 1-octyl-3-methylimidazolium tetrafluoroborate as precursors, exhibiting excellent fluorescence stability. The fluorescence of Y-CDs was selectively quenched by Cu²⁺ via the inner filter effect (IFE), allowing quantitative analysis with superior sensitivity compared to existing methods. By adding bacterial cellulose (BC) as a solid support, aggregation-induced fluorescence quenching was effectively reduced, and sensor robustness and portability were improved. Through smartphone-based colorimetric analysis, the Y-CDs@BCM sensor enabled rapid, visual interpretation of Cu²⁺ detection (within 1 min). Furthermore, cell viability and in vivo assays confirmed the biocompatibility of Y-CDs, indicating their suitability for biological imaging. This work presents an environmentally friendly, reliable, and practical method for on-site Cu²⁺ monitoring, emphasizing its broad application potential in food safety control and environmental analysis. Full article

This study introduces a MATrix LABoratory (MATLAB, version R2024b, update 1 (24.2.0.2740171))-based automated system for the detection and measurement of indication areas in coated surfaces, enhancing the accuracy and efficiency of quality control processes in metal, polymeric and thermoplastic coatings. The developed code identifies various indication characteristics in the image and provides numerical results, assesses the size and quantity of indications and evaluates conformity to ISO standards. A comprehensive testing method, involving non-destructive penetrant testing (PT) and radiographic testing (RT), allowed for an in-depth analysis of surface and internal porosity across different coating methods, including aluminum-, copper-, polytetrafluoroethylene (PTFE)- and polyether ether ketone (PEEK)-based materials. Initial findings had a major impact on indicating a non-homogeneous surface of obtained coatings, manufactured using different technologies and materials. Whereas researchers using non-destructive testing (NDT) methods typically rely on visual inspection and manual counting, the system under study automates this process. Each sample image is loaded into MATLAB and analyzed using the Image Processing Tool, Computer Vision Toolbox, Statistics and Machine Learning Toolbox. The custom code performs essential tasks such as image conversion, filtering, boundary detection, layering operations and calculations. These processes are integral to rendering images with developed indications according to NDT method requirements, providing a detailed visual and numerical representation of the analysis. RT also validated the observations made through surface indication detection, revealing either the absence of hidden defects or, conversely, internal porosity correlating with surface conditions. Matrix and graphical representations were used to facilitate the comparison of test results, highlighting more advanced methods and materials as the superior choice for achieving optimal mechanical and structural integrity. This research contributes to addressing challenges in surface quality assurance, advancing digital transformation in inspection processes and exploring more advanced alternatives to traditional coating technologies and materials. Full article

Effective arsenic removal is a challenge when smelting high-arsenic copper minerals (HACMs, As > 3.0 wt%). Current arsenic-removal methods for HACM smelting cannot effectively remove arsenic and do not satisfy environmental requirements. This study argues that two-stage filtration based on Fe-25Al porous material and oxygen-controlled roasting is an effective technique for HACM arsenic removal (As = 11.8 wt%). The use of two-stage filtration facilitated double interception: particles larger than 10 μm were mechanically intercepted by the pore channels, and submicron particles (0.1–10 μm) were intercepted by the filter cake. Specifically, in the second stage, the flue gas underwent gradient rapid cooling, and the arsenic in the flue gas rapidly condensed, resulting in efficient arsenic removal. The purity of the condensed product, As₂O_3, was greater than 99%. Moreover, adding sand to the roasted mineral increased the specific surface area from 0.484 m²/g to 0.590 m²/g, reducing the “bottleneck effect” of pores; the addition of carbon further increased the surface area to 2.457 m²/g, inhibiting the formation of arsenate. When the mineral feed rate increased from 50 kg/h to 80 kg/h, the oxygen partial pressure decreased; this effectively inhibited the formation of iron arsenate, and the arsenic removal efficiency increased from 70.20% to 95.61%. The optimized process achieved ≥94% arsenic removal efficiency and ≥76% sulfur-fixation efficiency, with low energy cost. Material balance analysis showed that after arsenic removal, the Cu/Si to Fe/Si ratio of the copper mineral reached 1.5, which is appropriate for immediate subsequent smelting. This study provides a new technological strategy for HACM arsenic removal. Full article

Quercetin, a natural polyphenolic flavonoid with antioxidant and anti-allergic properties, is extensively found in foods and holds significant importance for human health. In this study, a simple switch-off fluorescent sensor based on copper nanoclusters (Cu NCs) was proposed for the sensitive determination of quercetin. Glutathione acted as the reducing and protective agent in the synthesized process of Cu NCs via a facile, green one-pot method. As anticipated, the glutathione-capped Cu NCs (GSH-Cu NCs) exhibited favorable water solubility and ultrasmall size. The fluorescence property of GSH-Cu NCs was further enhanced with Al³⁺ ion through the aggregation-induced emission effect. When quercetin was present in the sample solution, the system exhibited effective fluorescence quenching, which was attributed to the internal filter effect. The GSH-Cu NCs/Al³⁺-based fluorescent sensor showed a good linear relationship to quercetin in the concentration range from 0.1 to 60 μM. A detection limit of 24 nM was obtained. Moreover, the constructed sensor was employed for the successful determination of quercetin in tea samples. Full article