Search Results (6,832)

Asbestos tailings represent a historical liability in many countries. Canada aims at transforming this industrial legacy into an opportunity to both mitigate the environmental footprint and recover critical (such as magnesium, nickel, chromium, and cobalt) and strategic metals, which represent significant economic development potential. This study aimed to investigate the recovery of critical and strategic metals (CSMs) from asbestos tailings using hydrochloric (HCl) acid leaching, with acid concentration (2–12 mol/L), leaching temperature (20–90 °C), and solid–liquid ratio (10–40%) as key process parameters. The tailing samples studied is composed mostly of chrysotile and lizardite. It contains about 40% magnesium (as its oxide MgO) and nickel and chromium showing contents 52 and 60 times higher than their respective average crustal abundances (Clarke values). Iron content is 8.7% (expressed as its ferric oxide Fe₂O₃). To optimize key factors influencing the leaching process, a statistical experimental design was employed. The designed leaching experiments were subsequently performed, and results were used to define leaching conditions aiming at maximizing Mg and Ni recoveries while minimizing iron contamination using response surface methodology (RSM) based on the central composite design (CCD). A quadratic polynomial model was developed to describe the relationship between the process parameters and metal recoveries. Among the tested effects of acid concentration, temperature, and pulp density on magnesium recovery, the modeling indicated that both hydrochloric acid concentration and leaching temperature significantly enhanced metal recovery, whereas increasing pulp density had a negative effect at low temperature. The empirical mathematical model derived from the experimental data, accounting for the uncertainties on chemical data, indicated that high magnesium recovery was achieved at 90 °C, with 10–12 N hydrochloric acid and a solid-to-liquid ratio of 33.6–40%. These findings reveal the potential for the recovery of critical and strategic metals, both in terms of efficiency and economic viability. Full article

This study aims to enhance fundamental research on the reaction behavior between ferric oxide and H₂–CO gas mixtures and to provide theoretical support for optimizing the injection of hydrogen-containing materials in the ironmaking process. In this study, the ultrafine ferric oxide powder was isothermally reduced with H₂–CO gas mixture at 1023 K–1373 K. The results indicated that when H₂ content is less than 30% at 1023 K, the ferric oxide sample reduced by the H₂–CO gas mixture exhibits a pronounced carbon deposition phenomenon during the reduction stage. The gas reactant composition had a relatively large influence on the reaction rate at the third stage of the reduction reaction (FeO → Fe). Assuming the single-step nucleation assumption theory together with kinetic experimental data, the relationship between the average reaction rate and the gas composition of the H₂–CO gas mixture was established for the FeO reduction stage. In addition, the apparent activation energy of the reduction reaction was generally in the range of 20–45 kJ/mol, indicating that the possible rate-controlling step was combined gas diffusion and interfacial gas–solid chemical reaction. 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

Thorium-rare earth-iron oxide deposits of the Lemhi Pass district, Idaho and Montana, are enriched in the middle rare earth elements (REE), and particularly neodymium (Nd). Overall, thorium (Th) and total rare earth oxide (TREO) grades of the deposits are sub equal at 0.4 wt. % but locally exceed 1 wt. % TREO. Nd-monazite, the major REE phase (35 wt. % Nd₂O₃) occurs in hydrothermal Th-REE mineralized quartz veins and biotite-rich shear zones of enigmatic origin. Hosted in Mesoproterozoic metasedimentary rocks, the deposits are modest in size but present over a large area with no obvious source pluton exposed. This paper documents the geochemistry of the monazite and provides the first geochronological data to constrain its origin. Elemental mapping and U-Th-total Pb EPMA dating of the monazite and thorite document a Paleozoic age for mineralization centered in the Late Devonian at approximately 355 Ma ± 20 Ma. A second period of volumetrically minor Th and REE remobilization is dated as Mesozoic (ca. 100 Ma). For context, a reactivated passive continental margin was present during the Devonian in eastern Idaho, while the Mesozoic was a time of major accretionary tectonics and arc magmatism further west. Nd and Pb isotopic data require a significant interaction of the fluids with an ancient crustal component represented by regional Mesoproterozoic metasedimentary rocks and granitoids. A source–transport–deposition model is hypothesized with metasomatic fractionation and enrichment of Nd during regional hydrothermal circulation. The aqueous fluids were hot, oxidizing, and likely saline, but the exact source of the Th and REEs and the mechanism of enrichment remains problematic. Additional analytical work and increased knowledge of the regional and district geology will improve this unconventional hypothesis for formation of Lemhi Pass’ unusual Nd-rich Th-REE-Fe mineralization. Full article

This study investigated the variation in precipitation in Fe-25Cr-5Al-Ti-RE ferritic stainless steel under different quenching heat treatment temperatures. Quenching heat treatments were performed at five temperatures, namely 600 °C, 700 °C, 800 °C, 900 °C, and 1000 °C. To analyze the alloy’s microstructure and precipitation behavior, comprehensive characterization techniques were employed, including X-ray Diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results demonstrated that after quenching at these temperatures, the main precipitation in the alloy was a chromium-rich phase (α′), aluminum oxide (Al₂O₃), titanium carbide (TiC), and titanium nitride (TiN). Specifically, Al₂O₃ was detected exclusively after heat treatments at 800 °C, 900 °C, and 1000 °C, with its particle size ranging from 10 nm to 100 nm. During high-temperature heat treatment, aluminum atoms and oxygen atoms in the matrix interacted with each other, and fine Al₂O₃ particles precipitated through a solid-state phase transition. Regarding titanium-containing precipitates, TiC precipitated after heat treatments at 700 °C, 800 °C, and 900 °C, whereas TiN was only observed after the quenching treatment at 1000 °C. The size of TiC particles fell within the range of 100 nm to 400 nm, while TiN particles exhibited a significantly larger size, spanning from 5 μm to 10 μm. Thermodynamic and kinetic analyses revealed that at elevated temperatures, nitrogen (N) exhibited a relatively high diffusion coefficient in the matrix; meanwhile, titanium (Ti) demonstrated an extremely strong chemical affinity for N. Consequently, even when the N content in the alloy was at a low level, N tended to preferentially react with Ti rather than with carbon (C) to form TiN. Full article

Over the next 5–10 years, the feedstock to lithium-ion battery recycling facilities will shift from Co- and Ni-rich chemistries to lower-value battery chemistries, such as lithium iron phosphate (LFP). Traditional recycling processes use toxic and corrosive inorganic acids for leaching, generating toxic waste streams. The low-value feedstocks will be LFP-rich with contamination from lithium cobalt oxide (LCO) and lithium–nickel–manganese–cobalt oxide (NMC) battery chemistries. Overall, the lower-value feedstock coupled with the need to reduce environmentally damaging waste streams requires the development of robust, green leaching processes capable of selectively targeting the LFP and LCO/NMC battery chemistries. This research concluded that a first-stage oxalic acid leach could selectively extract Al, Li, and P from the industrially sourced LFP-rich black mass. When operating at the optimal conditions (0.5 M oxalic acid, 5% solids, pH 0.8, and an agitation speed of 600 rpm), >99% of the Li and P and >97% of the Al were selectively extracted after 2 h, while Mn, Fe, Cu, Ni, and Co extractions were kept relatively low, namely, at 19%, <3%, <1%, 0%, and 0%. This research also explored a second-stage leach to treat the first-stage leach residue using ascorbic acid, citric acid, and glycine. It was concluded that when leaching with glycine (30 g/L glycine, a temperature of 40 °C, an agitation speed of 600 rpm, and 2% solids at pH 9.6), that >97% of the Co, >77% of the Ni, and 41% of the Mn were extracted, while the co-extraction percentages of Cu, Fe, and Al were <27%, <4%, and <2%. Full article

Background: Renal ischemia–reperfusion (I/R) injury represents a principal etiologic factor in acute kidney injury (AKI), in which ferroptosis plays a critical role. Mulberrin (Mul), a prenylated flavonoid with antioxidative properties, has an as-yet undefined role in renal I/R injury. Methods: We established a mouse renal IRI model and an HK-2 H/R system. Renal function, histological injury, oxidative stress, ferroptosis markers, and mitochondrial function were assessed. The role of Sirtuin 3 (Sirt3) in Mul-mediated effects was further examined using siRNA knockdown in HK-2 cells. Results: The administration of Mul led to a marked improvement in renal function, lessened tubular injury, and reduced apoptosis in IRI mice. Mul also restored GSH levels, decreased MDA and Fe²⁺ accumulation, and normalized expression of ferroptosis-related proteins, thereby suppressing ferroptosis. In H/R-injured HK-2 cells, Mul restored mitochondrial membrane potential, increased ATP production, and reduced ROS accumulation. Mechanistically, Mul markedly upregulated Sirt3 expression, and silencing Sirt3 abolished its antioxidant and anti-ferroptosis effects, confirming the essential role of Sirt3 in Mul-mediated protection. Conclusions: Our findings underscore Mul’s therapeutic promise in acute kidney injury and provide a mechanistic foundation for interventions directed at the Sirt3–ferroptosis pathway to safeguard renal function. Full article

Kratom (Mitragyna speciosa (Korth.) Havil.) is a medicinal plant containing bioactive alkaloids, notably mitragynine and 7-hydroxymitragynine, which are psychoactive compounds with analgesic and stimulant properties. Due to safety concerns, the use of Kratom leaves and mitragynine in oral pharmaceutical products is restricted. Therefore, their potential as topical cosmeceutical agents merits further exploration. This study aimed to investigate the antioxidant and anti-adipogenic activities of Kratom ethanolic (Et-MS) and alkaloid-rich (Alk-MS) extracts, as well as purified mitragynine, to determine whether mitragynine is the major bioactive compound responsible for lipid reduction in 3T3-L1 adipocytes. The antioxidant properties were assessed using DPPH, ABTS, and FRAP assays, yielding EC₅₀ values of 0.06 mg/mL, 0.29 mg/mL, and 55 g Fe²⁺/100 g for Et-MS, respectively. In comparison, ascorbic acid (positive control) showed a DPPH EC₅₀ value of 0.002 mg/mL. Both Alk-MS and mitragynine significantly inhibited lipid accumulation in 3T3-L1 adipocytes by up to 50–70% at non-cytotoxic concentrations (≤25 µg/mL), as determined by Oil Red O staining. These findings provide preliminary in vitro evidence that phenolic constituents contribute to antioxidant capacity, while mitragynine is the principal anti-adipogenic constituent in Kratom extracts. Collectively, the results support the potential for further development of Kratom-derived extracts and mitragynine as plant-based candidates for topical or cosmeceutical applications targeting subcutaneous fat and oxidative skin damage. 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

The thermal transformation mechanism of pyrite in coal, which governs sulfur emissions and ash deposition, remains highly controversial. There are significant discrepancies in reported activation energies (E_a) (60–310 kJ/mol) and conflicting reaction pathways. To resolve these long-standing controversies, this study proposes a competition-coupling mechanism: pyrolysis and oxidation compete under local O₂ and temperature gradients, while coupling through microstructural evolution. Specifically, pyrolysis generates a porous Fe_1−XS that facilitates oxidation, which in turn can form a passivating oxide/sulfate layer that promotes further pyrolysis. This mechanism reconciles longstanding kinetic controversies by showing that the apparent activation energy is not a fixed value but instead a dynamic parameter, shifting along a continuous curve that bridges pyrolysis and oxidation-dominated regimes. Furthermore, we construct a unified phase diagram by incorporating the competition-coupling mechanism into classical thermodynamic equilibria. This diagram uses the molar ratio FeS₂/(FeS₂ + O₂) and temperature to categorize the transformation process into four distinct regions—pyrolysis-dominated, competition-coupling, oxidation-dominated, and melt-dominated. The key contribution of this work lies in the diagram which offers a practical framework for optimizing combustion and roasting systems, allowing for improved control over sulfur emissions and ash-related issues such as slagging and fouling. Full article

In this study, insoluble CaSO₃ was applied to replace soluble sulfite/bisulfite salt in the Fe(II)-activated sulfite/bisulfite [S(IV)] process for the efficient 2,4,6-tribromophenol (TBP) degradation. CaSO₃ serves as a low-cost and slow-release source of S(IV), significantly improving S(IV) utilization compared to conventional soluble Na₂SO₃. The Fe(II)/CaSO₃ system generated SO₄^•− and HO^• through Fe(II)/Fe(III) redox cycling. Mechanistic studies confirmed SO₄^•− as the dominant reactive species, selectively attacking C-Br bonds and hydroxyl groups in TBP. Process optimization revealed effective performance under acidic conditions (pH 3.5–4.0) with minimal inhibition by common anions (Cl⁻, HCO₃⁻). The reactive sites of TBP were identified through Fukui function calculations, and the degradation pathway was elucidated based on LC-MS analysis. Toxicity evaluation indicated reduced ecological risk of degradation intermediates due to debromination and benzene ring cleavage. This work provides a sustainable strategy for efficient TBP removal and detoxification in wastewater treatment with benefiting S(IV) utilization. Full article

In this study, we investigate the effects of adding varying proportions of fulvic acid during the digestion of pyrite on the iron concentration in both dissolved and diluted sodium aluminate solutions. Based on the occurrence characteristics of iron in the solutions, oxygen was introduced into the diluted solution to examine its iron removal efficiency, and the influence of organic compounds in the solution on iron removal through oxidation was investigated. The results indicate that, during high-pressure digestion, organic compounds forms complexes with iron, disrupting the hydrophilic iron (or ferrous) hydroxide film formed on the pyrite surface, thereby accelerating its dissolution and leading to a sharp increase in sulfur and iron content in the leachate. After cooling and dilution (100 °C, Na₂O_k 170 g/L), the iron content in the sodium aluminate solution continued to be influenced by organic compounds, showing a significant positive correlation. Oxygenation experiments for iron removal were performed using the diluted solution. Under conditions of an oxygen flow rate of 60 mL/min and an oxidation duration of 2 h (95 °C, oxygen partial pressure was 0.05 Mpa), the iron content (calculated as Fe₂O₃) decreased from 0.078 g/L to 0.021 g/L. Characterization and analysis of the iron removal precipitates revealed that the iron-containing minerals were primarily trivalent iron phases, such as goethite and hematite, with minimal ferrous iron content. Additionally, organic carbon also precipitated together with iron, which confirms the synergistic removal of iron and organic compounds. These findings demonstrate that the oxidation of reducing sodium aluminate solutions containing organic compounds, sulfur, and iron with atmospheric oxygen during the Bayer process sedimentation stage can effectively oxidize predominantly ferrous iron into less soluble ferric iron, thereby achieving iron removal. Full article

Chlorinated benzoquinones, such as 2,6-dichlorobenzoquinone (DCBQ), are toxic disinfection byproducts of growing concern in aquatic environments. Advanced oxidation processes, particularly photo-Fenton treatment, provide sustainable alternatives for their degradation. However, optimization is required to ensure not only the removal of the parent compound but also the reduction in harmful intermediates. This study evaluated the degradation of DCBQ (1.0 mM H₂O₂, 150 W UV, pH 3.0, 25 °C) with ferrous ion between 0 and 1.0 mg/L. DCBQ removal followed a second-order kinetic model, reaching complete degradation. Aromaticity-loss and water color degradation adjusted to kinetics of second-order, reflecting the sequential reduction in chlorinated hydroquinones and chlorophenols type intermediates, with marked decreases after 120 min at 0.8 mg/L. Results showed that increasing iron dosage enhanced both the rate of DCBQ disappearance and the removal of aromaticity, with complete pollutant degradation. Importantly, optimal ferrous ion dosages (20 mol DCBQ: 70 mol H₂O₂: 1 mol Fe²⁺) effectively limited the persistence of intermediates, as evidenced by significant decreases in color and aromaticity, while avoiding excessive turbidity. These findings demonstrate that fine-tuning iron dosage in photo-Fenton systems can maximize contaminant elimination and minimize secondary byproducts, reinforcing their role as sustainable solutions for wastewater remediation. Full article

Soil contamination with petroleum-derived substances, including petrol, is one of the most serious environmental issues of the modern era. These products are characterised by their durability and stability in the environment, their capacity for bioaccumulation and their toxicity to many organisms, including plants. This study aimed to evaluate the impact of petrol contamination on trace element content in the above-ground parts of oats (Avena sativa L.) and to determine the effectiveness of in situ stabilisation methods using compost, bentonite and calcium oxide in reducing bioaccumulation of these elements. Petrol contamination of the soil significantly altered the biomass yield and the concentration of trace elements in the plants. It caused a decrease in the dry matter yield and an increase in the content of most trace elements in the above-ground parts of oats. The most pronounced effects were observed for Cd, Ni, Fe, Co, Cr and Mn, whose concentrations in the plants increased across the entire range of petrol doses. Petrol had a similar effect on Zn and Pb content in the above-ground parts of oats, but only up to a medium level of contamination (5 cm³ kg⁻¹). In contrast to the aforementioned elements, soil contamination with petrol contributed to a decrease in the copper content of the above-ground parts of oats. The materials applied to the soil had a beneficial effect on the biomass and the concentration of certain trace elements in plants. The compost and especially calcium oxide had a positive influence on plant yield. Compared to the series without their application to the soil, all materials reduced the content of Cr, Fe, Cd and, especially, Mn in the above-ground parts of plants. Compost also reduced the content of Pb, while bentonite and calcium oxide reduced the content of Co. Calcium oxide also reduced the content of Cu in the above-ground parts of oats. However, bentonite had a weaker effect than compost and calcium oxide. Changes in the content of other elements in plants after application of the aforementioned materials were often opposite (and dependent on the type of material), with the clearest effect being on nickel content. The materials used in the study produced good results in limiting the impact of minor soil contamination with petrol on the content of certain trace elements in plants. Full article

Superparamagnetic iron oxide nanoparticles (SPIONs) with sizes below 10 nm are biocompatible and non-toxic, making them promising for biomedical applications. To prevent their agglomeration and enhance their functionality, the nanoparticles were coated with citric acid (CA), which modifies the surface charge, improves dispersion stability, and facilitates biomedical use. In this work, a modular flow-through microreactor system was employed to synthesize and coat the nanoparticles in a single, continuous two-step process. The system enables precise control over temperature and mixing, ensuring uniform reaction conditions and minimizing hot spots. The synthesized Fe₃O₄ nanoparticles exhibited an average crystallite size of ~5 nm (XRD) and particle sizes of 4–6 nm (TEM). FTIR analysis confirmed the successful surface functionalization with CA, while TGA indicated a coating mass fraction of approximately 4–20 wt%, increasing with higher CA concentration. Zeta potential measurements revealed strong colloidal stability, with values around −35 mV at pH 6.5. Among the tested CA concentrations, the sample with a molar ratio of Fe₃O₄:CA = 1:0.25 exhibited the most favorable properties, including narrow size distribution and improved dispersion stability. These findings demonstrate that the continuous modular flow approach enables the reproducible synthesis of highly stable, sub-10 nm CA-coated SPIONs, offering promising potential for biomedical applications, particularly as magnetic resonance imaging (MRI) contrast agents. Full article