Search Results (14,538)

Acid mine drainage (AMD) pollution from closed coal mines in karst regions represents a major environmental challenge in the global mining industry. The complexity of hydrogeological conditions in such regions leads to significant challenges in both predictability and controllability of pollution. Taking the Yudong River Basin in Guizhou Province, Southwest China, as the study area, and based on six years (2017–2023) of systematic remediation practices and monitoring data, this study systematically evaluates the effectiveness and applicable conditions of three types of treatment technologies: centralized treatment stations, source control combined with end-of-pipe treatment, and water-sealing ecological plugging. On this basis, governance models applicable to karst regions are distilled. The results show that after six years of remediation, the number of pollution points in the Yudong River Basin decreased from 27 to 12. At the outflow section, the total Fe reduction rate reached 88.3%, the total Mn reduction rate reached 62.3%, and the proportion of contaminated river length was reduced by 78.5%. Each of the three technologies has its own applicable conditions. Centralized treatment stations, characterized by mature technology but high operational costs, are suitable for emergency transition periods. Source control combined with end-of-pipe treatment addresses both symptoms and root causes, making it applicable to complex pollution points. Water-sealing ecological plugging, although cost-controllable, carries a risk of secondary pollution in karst-developed areas. The failure of water-sealing ecological plugging technology is mainly attributed to two mechanisms: bypass flow through karst conduits and overflow induced by water level rise. Based on the six-year remediation practice, this study proposes a source control model for karst conduits centered on the core concepts of “filling, isolating, plugging, intercepting, draining, and controlling”. The implementation process consists of four stages: detailed investigation, graded optimization, stepwise implementation, and long-term monitoring. The core innovation lies in the cross-disciplinary application of coal mine water control techniques to environmental remediation, achieving a shift from passive end-of-pipe treatment to active source control. This model can provide theoretical reference and practical guidance for karst mining areas in Southwest China and other regions with similar geological conditions. Full article

The sources of potentially toxic elements (PTEs) in the lower reaches of the Yellow River (LYR) remain poorly understood due to intensive human activities in this region. To elucidate the spatiotemporal distribution characteristics and sources of PTEs, water samples were collected from both mainstream and tributary sites during the dry season (DS) and flood season (FS). Concentrations of eight PTEs (Fe, Mn, Cu, Zn, Pb, As, Cr, and Hg) were determined. The single-factor pollution index, Nemerow comprehensive pollution index, statistical techniques, and the positive matrix factorization (PMF) receptor model were jointly employed to evaluate PTEs pollution levels and quantitatively apportion its sources. The results showed that PTEs concentrations in the mainstream were significantly higher than those in the tributaries, with Fe and Mn being the primary contaminants exceeding standards. During the DS, the mean concentrations of Fe and Mn were 1.33 mg/L and 0.34 mg/L, with exceedance rates of 100% and 84.2%, respectively. In contrast, both concentrations declined markedly in the FS (Fe: 0.27 mg/L; Mn: 0.112 mg/L). The PMF model identified three sources in the DS, with contribution rates of 42.1% (geogenic background and domestic sewage), 32.4% (industrial wastewater), and 25.5% (agricultural sources). In the FS, two sources were resolved, namely a mixture of non-point source pollution and domestic sewage (64.3%) and a mixture of geogenic background and industrial wastewater (35.7%). The pronounced increase in non-point source contribution during the FS highlights the role of rainfall runoff in driving pollutant input. This study provides a scientific basis for PTEs pollution control in the LYR. Full article

Perovskite manganites (AMnO₃) and perovskite-like manganites (A’_1−xA_xMnO₃) are complex oxide materials that have attracted significant attention from the scientific community in recent years due to their structural flexibility, mixed-valence state, tunable electronic configuration, and multifunctional properties. This review systematically analyzes the synthesis methods, structural classification, and physicochemical characterization of perovskite manganites, as well as their magnetic, optical, electrical, dielectric, and catalytic properties. The influence of solid-state reactions, sol–gel, Pechini, hydrothermal, co-precipitation, microwave, and other mild chemical approaches on phase purity, morphology, particle size, and oxygen stoichiometry was examined. The structural diversity of perovskite and perovskite-like manganites, including simple ABO₃, double perovskites, multilayer, and low-dimensional systems, was characterized in relation to their functional properties. The review discussed the capabilities of methods for synthesizing and analyzing morphological properties, demonstrating the role of doping, cation substitution, oxygen vacancies, and Jahn–Teller distortions in controlling material properties. Prospects for the application of perovskite manganites in spintronics, magnetocaloric cooling, photocatalysis, gas-sensing devices, and energy conversion and storage systems were analyzed. This review highlights the structure–property–application relationship in perovskite manganites. Full article

A new approach to 5,5-fused heterocyclic derivatives of cyclopentadienylmanganese tricarbonyl and pentamethylruthenocene is presented. 1,2-Dicarbophenoxycyclopentadienyl complexes of manganese and ruthenium were hydrolyzed to 1,2-dicarboxylic acids. Oxalyl chloride converted the acids to chlorocarbonyls, which reacted with bis(trimethylsilyl)sulfide to give the cyclopentadienyl-fused thioanhydrides. Alternatively, dehydration of the diacids with trifluoroacetic anhydride closed the diacids to cyclopentadienyl-fused anhydrides. Treatment of the anhydrides with p-toluidine followed by oxalyl chloride led to cyclopentadienyl-fused carboxylic imides. This approach enables direct comparison of electron-deficient Mn(CO)₃ and electron-rich Ru(Cp*) coordination environments on the 5,5-fused heterocycles. Spectroscopic data reveal systematic downfield NMR shifts and higher infrared carbonyl stretching frequencies for the manganese complexes, consistent with lower electron density in the Mn(CO)₃ compared to Ru(Cp*). Crystallographic analyses confirm that heterocycle fusion occurs without significant perturbation of the metal–cyclopentadienyl geometry. Comparative analysis across the series demonstrates that metal-dependent effects are primarily electronic rather than structural, with the Mn(CO)₃ and Ru(Cp*) fragments modulating electron distribution within the fused ligand framework. Full article

Metal oxide nanoparticles serve as crucial drivers in modern biomedical, catalytic, environmental, and energy technologies due to their high surface-to-volume ratios and quantum confinement properties. Traditional chemical and physical synthesis methods remain limited by significant energy footprints, high costs, and the use of hazardous reagents. To address these challenges, bioinspired (“green”) synthesis has emerged as a sustainable paradigm that employs biological systems as nature nanofactories. This critical review provides a provides a comprehensive and systematic analysis of the green synthesis of major metal oxide systems (ZnO, TiO₂, Fe₃O₄/Fe₂O₃, CuO, Co₃O₄, CeO_2, and MnO₂) using diverse biological templates, including plant extracts, bacteria, fungi, algae, and biopolymers. Moving beyond simple descriptive summaries, we critically evaluate the foundational electron-transfer and nucleation mechanism, systematically correlate processing parameters with physical outcomes, and offer a rigorous comparative analysis across different biological kingdoms. Finally, we directly address the underlying challenges facing the field: reproducibility bottlenecks, scalability limits, environmental safety variations, and regulatory hurdles necessary for industrial translation. Full article

Membranous nephropathy (MN) and minimal change disease (MCD) are the most common causes of nephrotic syndrome following hematopoietic stem cell transplantation (HSCT), a complication conventionally attributed to chronic graft-versus-host disease (GVHD). Paraneoplastic MCD is well described in lymphoid malignancies but is rarely reported in myeloid neoplasms. We report two cases of biopsy-confirmed MCD presenting as the initial manifestation of acute myeloid leukemia (AML) relapse following allogeneic HSCT. Both patients were White men in their sixties with relapsed/refractory AML who developed nephrotic-range proteinuria and acute kidney injury after matched unrelated donor HSCT without histologic evidence of GVHD. Renal biopsies confirmed MCD in both cases. Corticosteroid therapy was ineffective in halting renal deterioration; renal function improved only after initiation of leukemia-directed therapy, with one patient achieving dialysis independence. These cases highlight a rare paraneoplastic presentation of AML relapse. Nephrotic syndrome due to MCD may signal post-HSCT leukemia recurrence, and evaluation for AML relapse warrants consideration in steroid-refractory cases or those without concurrent GVHD. In such cases, control of the underlying malignancy, rather than escalation of immunosuppression, may be central to renal recovery. Full article

High-entropy alloys (HEAs) are a transformative class of materials with remarkable structural and functional properties. Solid-state processing techniques, such as high-energy ball milling, are being increasingly used for their production. In these processes, the use of a process control agent (PCA) seems to be essential to prevent excessive cold welding and agglomeration; however, the influence of different PCAs on alloy formation remains insufficiently understood. This study systematically examined the effects of the PCA type, milling configuration, and elemental substitution on HEAs mechanosynthesis. A non-equiatomic alloy, Al₁₀Cr₁₂Fe₃₅Mn₂₃Ni₂₀ (selected for its known single-phase Face Center Cubic (FCC) behavior), was used to explore the PCA and mill-type effects. The alloy was synthesized in a planetary mill (Fritsch Pulverisette 7) and a vibratory mill (SPEX 8000M) using diverse PCAs, including liquid (methanol, ethanol, isopropyl, and n-heptane) and solid (stearic acid and sodium chloride) agents. In addition, lightweight equiatomic alloys MgAlTiNi(Co,Cr,Fe) were used to explore the influence of different PCAs and the effect of elemental substitution under similar PCA conditions as those used with the equiatomic alloy. The products were characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential thermal analysis techniques. The results highlighted that the PCA selection, milling configuration, and alloy chemistry influenced the phase evolution, particle size distribution, and thermal behavior. The results provide insights into the mechanosynthesis of selected high-entropy alloys produced under different PCA and milling conditions. Full article

Sedimentary manganese deposits are an important mineral resource and also play a significant role in restoring the ancient marine environment. The redox environment of the ocean during the Mesoproterozoic era has long been a subject of controversy. This paper takes a large-scale sedimentary manganese deposit in northwest China as the research object, attempting to analyze the changes in the marine environment during the Mesoproterozoic era and their impact on the Mn mineralization processes. In recent years, an exploration breakthrough has been made in the manganese deposits in the Annanba region on the southern margin of the Dunhuang block, NW China. The Qingshagou Mn deposit is the largest and most representative in the region. Geochemical characteristics show that the ores have low average ratios of Fe/Mn (<0.19), V/Cr (<1.20), V/(V+Ni) (<0.54), and Al/(Al+Fe+Mn) (<0.30) but high average ratios of U/Th (~0.95), and Y/Ho (~28). The Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) patterns exhibit that middle rare earth elements are slightly enriched with weak positive anomalies for both Y (0.93~1.01) and Ce (0.97~1.15) and weak negative anomalies for Eu (0.87~0.99). The δ¹³C_PDB value of the ore ranges from −13.4‰ to −23.3‰, which is consistent with the δ¹³C_PDB value range of organic matter. Synthesizing these findings, it is concluded that the Qingshagou Mn deposit formed in a suboxic to oxic environment, the ore-forming materials were primarily derived from a submarine hydrothermal system, and the changes in redox conditions promoted the Mn precipitation. Full article

To investigate the effects of co-application of KMnO₄-modified biochar and organic fertilizer on the physicochemical properties, carbon and nitrogen content, and growth of Chinese cabbage in acidic red soil. Using typical acidic red soil from Yunnan as the test substrate, this study conducted a pot experiment with four treatment groups: control (CK), organic fertilizer alone (OF), biochar combined with organic fertilizer (BOF), and potassium permanganate KMnO₄-modified biochar combined with organic fertilizer (Mn-BOF), each at three application rates (1500, 3000, and 4500 kg/ha). The results indicated that KMnO₄ modification significantly improved the pore structure of biochar, increasing its specific surface area by 22.776%, and successfully loaded manganese onto the biochar surface. Compared with the CK, all treatments significantly increased soil pH, organic matter (SOM), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and available potassium (AK), with the effects gradually increasing as the application rate rose; the 4500 kg/ha treatment yielded the best results. The Mn-BOF treatment was most effective in increasing soil organic carbon (SOC), total nitrogen (TN), soluble organic carbon and nitrogen (DOC/DON), and microbial carbon and nitrogen (MBC/MBN); simultaneously, the Mn-BOF treatment significantly promoted the growth of Chinese cabbage, with yield under the 4500 kg/ha treatment increasing by 158.58% compared to CK (under pot-grown conditions), and soluble total sugars, chlorophyll, and vitamin C content also significantly increased. In summary, Mn-BOF can improve the fertility of acidic red soil, particularly demonstrating excellent performance in enhancing key carbon and nitrogen components such as SOC, TN, DOC, DON, MBC and MBN. This, in turn, promotes increased yield and improved quality of Chinese cabbage, providing feasible guidance for enhancing soil fertility in highland agricultural systems. Full article

Microsegregation in cast materials is important to their solidification, solid-state transformation, microstructure and material properties. This work studies quantitatively the microsegregation of Si, Mn, Cu, Sn, and P in graphitic cast irons using an electron microprobe with wavelength dispersive spectrometry. The alloys contain [mass%] C: 3.86, Si: 2.59, Mn: 0.64, P: 0.03, S: 0.01, Sn: 0.098, Cu: 0.84, Mg: 0.065, include graphite morphologies ranging from ductile iron to compacted graphite iron and solidified with a solidification time of 10 min. Concentration maps are presented, showing that microsegregation patterns provide detailed information about the solidification chronology of the metal matrix. Sequencing the measurements into concentration profiles showed that, despite large differences in microstructure and cooling curve characteristics, the severity of microsegregation was similar in the studied materials. Scheil simulation of concentration profiles provided decent prediction of concentration profiles, given appropriate thermodynamic data. Numerical simulation of isothermal diffusion suggested that, for about 10 min of solidification time, diffusion in austenite mainly affected the last 10% of the matrix to freeze. Effective partition coefficients extracted from the concentration profiles varied slightly through solidification. The estimated mean effective partition coefficients for the first 90% of the alloy to freeze are ${\overline{k}}_{Si}^{\gamma /L}=1.124\pm 0.006$, ${\overline{k}}_{Mn}^{\gamma /L}=0.696\pm 0.008$, ${\overline{k}}_P^{\gamma /L}=0.15\pm 0.03$, ${\overline{k}}_{Sn}^{\gamma /L}=0.50\pm 0.02$, ${\overline{k}}_{Cu}^{\gamma /L}=1.35\pm 0.01$, where $\pm$ indicates standard deviation. Full article

Metal oxide nanomaterials tailored at the nanoscale are opening new avenues for advanced electroanalytical sensing devices with enhanced properties, including improved electrocatalytic activity. In this work, a novel Mn₂Mo₃O₈/MnO-MWCNT nanocomposite was employed to modify a screen-printed carbon electrode, enabling the fabrication of an amperometric sensor for H₂O₂ operating at relatively low applied potential due to the catalytic activity of the nanocomposite. Further functionalization of this nanostructured surface with glucose oxidase allowed the construction of an electrochemical glucose biosensor, where the Mn₂Mo₃O₈/MnO-MWCNT material acted as an efficient electrocatalyst for hydrogen peroxide detection. The H₂O₂ sensor exhibited a linear response from 0.06 mM to 3.00 mM, with a sensitivity of (2.22 ± 0.02) µA mM⁻¹ and a detection limit of 22 µM. The glucose biosensor showed a linear response in the range from 0.10 mM to 18.9 mM glucose, with a sensitivity of (0.345 ± 0.005) µA mM⁻¹, and a detection limit of 29 µM. The biosensor displayed excellent selectivity and high stability and was successfully applied to the determination of glucose in lactose-free skimmed milk. Full article

The agricultural and environmental application of Miscanthus × giganteus biomass ash (MBA) as a soil amendment requires a thorough assessment of its properties, nutrient potential, and associated risks. This study characterizes the elemental composition, pH, cation exchange capacity (CEC), and polycyclic aromatic hydrocarbons (PAHs) content of MBA in comparison with other common biomass ashes (crops, wood, and sewage sludge) referred to the international regulatory standards. The ash exhibits a strong alkaline pH (11.03), suggesting potential to improve soil pH in acid soils, but requires careful controlled application to prevent excessive alkalization. The main nutrients detected include K (5.54%), Ca (2.07%), Mg (0.37%), and P (0.86%), indicating its potential as a soil amendment, though long-term use may cause nutrient imbalances. Micronutrients such as Zn (240.67 mg·kg⁻¹), Mn (297 mg·kg⁻¹), and Cu (33.5 mg·kg⁻¹) are found in concentrations suitable for agricultural use, while potentially toxic elements (PTEs), including Cd, Cr, Ni, and Pb, are below detection limits, thereby reducing the risk of pollution. As (8.3 mg·kg⁻¹) and ΣPAHs (1.63 mg·kg⁻¹) remain within safety thresholds, suggesting a low environmental toxicity of MBA. The low Na content (0.12%) indicates a minimal risk of salinity accumulation, distinguishing MBA from high-sodium biomass ashes. Soil alkalization, disruptions in nutrient balance, and element leaching are risks to be considered. Despite these concerns, its composition is in agreement with established safety guidelines, supporting its feasibility for valorization as a sustainable soil amendment and remediation material. To maximize agronomic benefits and mitigate environmental risks, it is important to utilize the ash, considering site conditions and carry out regular monitoring of the soil. Full article

This work investigates a novel GaCl₃·AlCl₃/H₂O catalytic system for the synthesis of low-molecular weight polyisobutylene (LPIB). Catalytic performance was improved by employing a dual Lewis acid system, which outperformed the conventional single component (GaCl₃/H₂O) catalyst in terms of both reaction rate and yield. In accordance with the optimized reaction conditions, the conversion of monomer was found to be 97%, thereby achieving low molecular weight polyisobutylene (LPIB) with a number average molecular weight (M_n) of 3900 g/mol. Density functional theory (DFT) calculations revealed a lower proton transfer barrier (5.8 kcal/mol) in the dual Lewis acid catalytic structure compared to its single component counterpart. Subsequent theoretical analyses, incorporating electrostatic potential (ESP), independent gradient model based on Hirshfeld partition (IGMH), and distortion/interaction analysis, attributed this observed kinetic advantage to a higher positive ESP extremum and enhanced interaction between the IB fragment and the Lewis-acidic active center. Together, these results establish the GaCl₃·AlCl₃/H₂O dual Lewis acid system as an enhanced catalytic platform over the conventional GaCl₃/H₂O system for efficient IB polymerization toward LPIB synthesis. Full article

The Baleysky gold deposit in Eastern Transbaikalia is a classic example of the long-term environmental legacy of gold mining. The cessation of industrial wastewater discharge in 1995 led to the accumulation of more than 3 million m³ of acidic water with high concentrations of heavy metals and metalloids. These waters contain concentrations many times higher than the maximum permissible levels for fishery waters (Mn up to 6594, Al—1473, Zn—486, and Cu—414), posing a significant threat to the ecosystem of the Unda River and the health of the local population. The aim of this study was to evaluate the effectiveness of the artificial geochemical barrier method for treating such waters under laboratory conditions. Column experiments were conducted using local soil and the commercial carbonate sorbent taurite at a sorbent-to-filtrate ratio of 1:5. Taurite demonstrated a significantly higher sorption capacity than soil, substantially reducing the concentrations of As, Cd, Pb, Al, Mn, Fe, Zn, and Cu and raising the pH from 2.90 to 7.96–8.03. Although health risks associated with both carcinogenic (CR) and non-carcinogenic effects (HI) decreased significantly after treatment with taurite, residual risk levels remained unacceptably high (CR ≈ 10⁻³, HI > 1). The results show that engineered geochemical barriers have great potential for reducing anthropogenic contamination at abandoned mining sites, although further optimization of this technology is necessary to achieve compliance with regulatory requirements. Full article

Phosphorites are a vital source of phosphorus for agricultural and industrial applications and are increasingly recognized for their potential as secondary repositories of critical raw materials (CRMs) such as rare earth elements plus yttrium (REYs). This study investigates deep-sea phosphorites from the Galicia Bank, Madeira, and Canary Seamounts, in the NE Atlantic Ocean, which are spatially associated with ferromanganese (Fe-Mn) mineralization. Through integrated petrographic, geochemical, and in situ isotopic analyses (O and Sr), we assess the timing, processes, and paleoenvironmental conditions of phosphogenesis and its implications for CRM enrichment. Rare earth element patterns in apatite reflect a predominant seawater-derived signature with variable Ce anomalies. Nevertheless, variable Y/Ho ratios point to evolving fluid sources including a hydrogenous component (directly derived from seawater), modified porewaters and, locally, volcanic or possibly hydrothermal inputs. Oxygen and strontium isotope compositions constrain phosphogenesis to several episodes ranging from the Upper Cretaceous to the Middle Miocene, with distinct isotopic shifts identifying both primary formation and later overprinting processes mostly linked to Fe-Mn oxyhydroxide growth or volcanic–hydrothermal activity. These findings highlight the dynamic and multiphase nature of phosphorite formation in deep-marine settings. The integration of high-resolution geochemical and isotopic tools proves essential for reconstructing genetic histories, defining metallogenic context and evaluating CRM prospectivity in complex submarine systems. Full article