Search Results (353)

This study focuses on S32654 super austenitic stainless steel (SASS) and systematically characterizes the morphology of the sigma (σ) phase and the segregation behavior of alloying elements in its as-cast microstructure. High-temperature confocal scanning laser microscopy (HT-CSLM) was employed to investigate the effect of the rare earth element yttrium (Y) on the solidification microstructure and σ phase precipitation behavior of SASS. The results show that the microstructure of SASS consists of austenite dendrites and interdendritic eutectoid structures. The eutectoid structures mainly comprise the σ phase and the γ₂ phase, exhibiting lamellar or honeycomb-like morphologies. Regarding elemental distribution, molybdenum displays a “concave” distribution pattern within the dendrites, with lower concentrations at the center and higher concentrations at the sides; when Mo locally exceeds beyond a certain threshold, it easily induces the formation of eutectoid structures. Mo is the most significant segregating element, with a segregation ratio as high as 1.69. The formation mechanism of the σ phase is attributed to the solid-state phase transformation of austenite (γ → γ₂ + σ). In the late stages of solidification, the concentration of chromium and Mo in the residual liquid phase increases, and due to insufficient diffusion, there are significant compositional differences between the interdendritic regions and the matrix. The enriched Cr and Mo cause the interdendritic austenite to become supersaturated, leading to solid-state phase transformation during subsequent cooling, thereby promoting σ phase precipitation. The overall phase transformation process can be summarized as L → L + γ → γ → γ + γ₂ + σ. Y microalloying has a significant influence on the solidification process. The addition of Y increases the nucleation temperature of austenite, raises nucleation density, and refines the solidification microstructure. However, Y addition also leads to an increased amount of eutectoid structures. This is primarily because Y broadens the solidification temperature range of the alloy and prolongs grain growth perio, which aggravates the microsegregation of elements such as Cr and Mo. Moreover, Y raises the initial precipitation temperature of the σ phase and enhances atomic diffusion during solidification, further promoting σ phase precipitation during the subsequent eutectoid transformation. Full article

The mineral processing of a low-grade tungsten-molybdenum ore (LGTMO) was investigated to assess the potential of recovering molybdenum (Mo) and tungsten (W). Techniques such as Polarizing Microscope (PM), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), Mineral Liberation Analysis (MLA), and Advanced Mineral Identification and Characterization System (AMICS) were employed. The recoverable metals in the ore are Mo (0.158% ± 0.03%) and W (0.076% ± 0.02%). Mo exists in two forms: 63.30% as molybdenite and 36.7% as powellite (CaMo_xW_1−xO₄). W is present as 75.26% scheelite and 24.74% powellite. The complete dissociation rates of molybdenite and scheelite-powellite are 27.14% and 88.87%, respectively. Particles of scheelite-powellite with a diameter less than 10 µm account for 34.61%, while molybdenite particles with a diameter below 10 µm make up 72.73%. Scheelite-powellite is mainly associated with olivine and dolomite, while molybdenite is mainly associated with pyroxene, calcite, and hornblende. Based on the process mineralogy, the mineralogical factors influencing the flotation recovery of molybdenite and scheelite-powellite were analyzed. Finally, a complete hydrometallurgical leaching test was carried out. The optimal experimental conditions are as follows: liquid-solid ratio of 6 mL/g, KMnO₄ concentration of 0.015 mol/L, Na₂CO₃ concentration of 0.12 mol/L, NaHCO₃ concentration of 0.024 mol/L, leaching time of 4 h, and leaching temperature of 85 °C. Under these conditions, the leaching efficiencies of Mo and W reach 79.23% and 41.41%, respectively. This study presents a novel approach for the recovery of refractory W and Mo resources in LGTMO while simultaneously providing a theoretical basis for the high-efficiency utilization of these resources. Full article

Arsenic (As) contamination in groundwater represents a major global public health threat, particularly in alluvial aquifer systems where redox-sensitive geochemical processes facilitate the mobilization of naturally occurring trace elements. This study investigates groundwater quality, particularly focusing on the origin of arsenic contamination in shallow and deep alluvial aquifers of the Lower Sakarya River Basin, which are crucial for drinking, domestic, and agricultural uses. Groundwater samples were collected from 34 wells—7 tapping the shallow aquifer (<60 m) and 27 tapping the deep aquifer (>60 m)—during wet and dry seasons for the hydrogeochemical characterization of groundwater. Environmental isotope analysis (δ¹⁸O, δ²H, ³H) was conducted to characterize origin and groundwater residence times, and the possible hydraulic connection between shallow and deep alluvial aquifers. Mineralogical and geochemical characterization of the sediment core samples were carried out using X-ray diffraction and acid digestion analyses to identify mineralogical sources of As and other metals. Pearson correlation coefficient analyses were also applied to the results of the chemical analyses to determine the origin of metal enrichments observed in the groundwater, as well as related geochemical processes. The results reveal that 33–41% of deep groundwater samples contain arsenic concentrations exceeding the WHO and Turkish drinking water standard of 10 µg/L, with maximum values reaching 373 µg/L. Manganese concentrations exceeded the 50 µg/L limit in up to 44% of deep aquifer samples, reaching 1230 µg/L. On the other hand, iron concentrations were consistently low, remaining below the detection limit in nearly all samples. The co-occurrence of As and Mn above their maximum contaminant levels was observed in 30–33% of the wells, exhibiting extremely low sulfate concentrations (0.2–2 mg/L), notably low dissolved oxygen concentration (1.45–3.3 mg/L) alongside high bicarbonate concentrations (450–1429 mg/L), indicating localized varying reducing conditions in the deep alluvial aquifer. The correlations between molybdenum and As (rdry = 0.46, rwet = 0.64) also indicate reducing conditions, where Mo typically mobilizes with As. Arsenic concentrations also showed significant correlations with bicarbonate (HCO₃⁻) (rdry = 0.66, rwet = 0.80), indicating that alkaline or reducing conditions are promoting arsenic mobilization from aquifer materials. All these correlations between elements indicate that coexistence of As with Mn above their MCLs in deep alluvial aquifer groundwater result from reductive dissolution of Mn/Fe(?) oxides, which are primary arsenic hosts, thereby releasing arsenic into groundwater under reducing conditions. In contrast, the shallow aquifer system—although affected by elevated nitrate, sulfate, and chloride levels from agricultural and domestic sources—exhibited consistently low arsenic concentrations below the maximum contaminant level. Seasonal redox fluctuations in the shallow zone influence manganese concentrations, but the aquifer’s more dynamic recharge regime and oxic conditions suppress widespread As mobilization. Mineralogical analysis identified that serpentinite, schist, and other ophiolitic/metamorphic detritus transported by river processes into basin sediments were identified as the main natural sources of arsenic and manganese in groundwater of deep alluvium aquifer. Full article

This study evaluated the effect of soil and foliar fertilization with nitrogen (N), molybdenum (Mo), zinc (Zn), and their combination (Zn-Mo) on nutrition, enzymatic activity, photosynthetic pigments, and productive parameters in the Western Schley pecan tree. An orthogonal Taguchi L16 design was used with differentiated soil and foliar nitrate concentrations, reaching an average of 1557.7 mg kg⁻¹, and increasing up to 1907 mg kg⁻¹ depending on the fertilization dose. Nitrate reductase activity (NRNO₃⁻) significantly increased with N and Mo applications, reaching a maximum of 13.62 µmol. Among photosynthetic pigments, chlorophyll a was the only variable with a significant response, highlighting the role of Mo in its enhancement. Positive effects were also observed on pomological traits such as yield (up to 425 kg ha⁻¹), nut weight, and kernel percentage with increased doses of N and Mo. In conclusion, combined fertilization improved the nutritional status, physiological responses, and productivity of pecan trees, emphasizing the importance of balanced nutrient management to avoid nutritional antagonisms and to optimize both yield and fruit quality. Full article

The data on the volumetric radon activity of the Akchatau territory were systematized in the context of radioecological safety. Radon (Rn²²² and Rn²²⁰) and indoor radon (isotopes Po, Pb, and Bi) make a significant contribution to radon radiation in residential and industrial premises. Increased radon concentration in a number of areas is associated with the Akchatau tungsten–molybdenum mine. The source of radon in geological terms is acid leucocratic granites in the northwestern and southeastern parts of the studied territory. Seasonal assessment of radon radiation was carried out using modern devices “Alfarad Plus” and “Ramon-Radon”. Frequency analysis of the average annual equivalent equilibrium concentration (EEC) in 181 premises showed that only in 47.5% of the premises does the volumetric radon activity not exceed the current standards (200 Bq/m³). Differentiated values of radon concentration were obtained in cases where daily and seasonal observations were carried out. In 43.1% of premises, the effective dose varies from 6.6 mSv/year to 33 mSv/year, and for 9.4% of premises, from 33 mSv/year to 680 mSv/year. The increased radon concentration is caused by high exhalation from the soil surface, the radioactivity of building materials, and low air exchange in the surveyed premises. In the northwestern part of Akchatau, anomalous zones were found where the exposure dose rate of gamma radiation exceeds 0.6 mkSv/hour. An objective assessment of radon largely depends on a number of factors that take into account the geological, technical, atmospheric, and climatic conditions of the region. Therefore, when planning an optimal radon rehabilitation strategy, it is necessary to take the following factors into account: the design features of residential premises and socio-economic conditions. Practical recommendations are given for radiation-ecological and hygienic monitoring of radon safety levels in the environment to reduce effective doses on the population. Full article

Extreme conditions induced by shock exert unprecedented force on crystal lattice and push atoms away from their equilibrium positions. Nonequilibrium molecular dynamics (MD) simulations are one of the best ways to describe material behavior under shock but are limited by the availability and reliability of potential functions. In this work, a specific embedded atom (EAM) potential of molybdenum (Mo) is built for shock and tested by quasi-isentropic and piston-driven shock simulations. Comparisons of the equation of state, lattice constants, elastic constants, phase transitions under pressure, and phonon dispersion with those in the existing literature validate the reliability of our EAM potential. Quasi-isentropic shock simulations reveal that critical stresses for the beginning of plastic deformation follow a [111] > [110] > [100] loading direction for single crystals, and then polycrystal samples. Phase transitions from BCC to FCC and BCC to HCP promote plastic deformation for single crystals loading along [100] and [110], respectively. Along [111], void directly nucleates at the stress concentration area. For polycrystals, voids always nucleate on the grain boundary and lead to early crack generation and propagation. Piston-driven shock loading confirms the plastic mechanisms observed from quasi-isentropic shock simulation and provides further information on the spall strength and spallation process. Full article

Mineral imbalances in sheep can have significant health and economic consequences, yet regional assessments of trace mineral and toxic element status are limited. Oregon is an endemically selenium (Se)-deficient region, but a statewide evaluation has not been conducted. This study assessed whole blood concentrations of 18 elements in 370 clinically normal ewes from 56 farms across Oregon to determine the prevalence of deficiencies and potential toxic exposures. A deficiency threshold of <120 ng Se/mL whole blood was used. We found that 28% of animals were Se-deficient, and 27% of farms had an average whole blood Se below this threshold. No animals reportedly showed overt clinical signs of deficiency or toxicity, and no excessive exposure to toxic elements such as arsenic, lead, or cadmium was found. We also compared mineral concentrations in blood collected using standard EDTA tubes versus mineral-free EDTA tubes, and in whole blood versus plasma, to assess alternative sampling strategies. Strong correlations (r > 0.9) for Se, cobalt (Co), and molybdenum (Mo) between plasma and whole blood allowed for the derivation of conversion equations. These findings provide updated insights into the mineral status of Oregon sheep, contribute to whole blood reference data, and support practical alternatives to improve trace mineral testing in field conditions. Full article

Osteoporosis is a major public health concern, particularly among postmenopausal women. Environmental exposure to metals has been proposed as a potential contributor to osteoporosis, but human data remain limited and inconsistent. This study investigated changes in urinary concentrations of 20 metal(loid)s in patients with osteoporosis, as well as the association of these elements with bone mineral density (BMD), in a cohort of 380 postmenopausal women aged 50–70 years from Cascavel, Paraná, Brazil. Demographic, lifestyle, and clinical data were collected, and urinary concentrations of aluminum (Al), barium (Ba), cadmium (Cd), cobalt (Co), cesium (Cs), copper (Cu), mercury (Hg), lithium (Li), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), rubidium (Rb), antimony (Sb), selenium (Se), tin (Sn), strontium (Sr), thallium (Tl), uranium (U), and zinc (Zn) were measured by inductively coupled plasma mass spectrometry. BMD was assessed at the lumbar spine, femoral neck, and total hip using dual-energy X-ray absorptiometry. Osteoporosis was diagnosed in 73 participants (19.2%). Osteoporotic women had significantly higher urinary concentrations of Cd, Mn, Pb, Sb, Sn, and Zn (p < 0.05). Statistically significant negative correlations were observed between BMD and urinary concentrations of Al, Cd, Hg, Mn, Sb, and U. After adjustment for confounders, elevated urinary concentrations of Cd, Mn, Pb, and Sb remained independently and significantly associated with higher odds of osteoporosis, with Cd (aOR = 1.495; p = 0.026) and Sb (aOR = 2.059; p = 0.030) showing the strongest associations. In addition, women with urinary concentrations above the 90th percentile for both Cd and Sb had a significantly higher prevalence of osteoporosis compared to those with lower levels (44.4% vs. 18.0%; p = 0.011). Longitudinal studies are needed to confirm causality and inform prevention strategies. Full article

The aim of this study is to explore the feasibility of using flotation wastewater from copper–porphyry ore processing to synthesize a gel that serves as a precursor for a polymer nanocomposite used in supercapacitor electrode fabrication. These wastewaters—characterized by high acidity and elevated concentrations of metal cations (Cu, Ni, Zn, Fe), sulfates, and organic reagents such as xanthates, oil (20 g/t ore), flotation frother (methyl isobutyl carbinol), and pyrite depressant (CaO, 500–1000 g/t), along with residues from molybdenum flotation (sulfuric acid, sodium hydrosulfide, and kerosene)—are byproducts of copper–porphyry gold-bearing ore beneficiation. The reduction of Ni powder in the wastewater induces the degradation and formation of a gel that captures both residual metal ions and organic compounds—particularly xanthates—which play a crucial role in the subsequent steps. The resulting gel is incorporated during the oxidative polymerization of aniline, forming a nanocomposite with a polyaniline matrix and embedded xanthate-based compounds. An asymmetric supercapacitor was assembled using the synthesized material as the cathodic electrode. Electrochemical tests revealed remarkable capacitance and cycling stability, demonstrating the potential of this novel approach both for the valorization of industrial waste streams and for enhancing the performance of energy storage devices. Full article

The low availability of phosphorus (P) in soil has become a critical factor limiting crop growth and agricultural productivity. This study aimed to isolate and evaluate a bacterial strain with high phosphate-solubilizing capacity to improve soil phosphorus utilization and promote crop growth. A phosphate-solubilizing bacterium, designated as YS-13, was isolated from farmland soil in Henan Province, China, and identified as Brevibacillus laterosporus based on morphological characteristics, physiological and biochemical traits, and 16S rDNA sequence analysis. Qualitative assessment using plate assays showed that strain YS-13 formed a prominent phosphate solubilization zone on organic and inorganic phosphorus media containing lecithin and calcium phosphate, with D/d ratios of 2.28 and 1.57, respectively. Quantitative evaluation using the molybdenum–antimony colorimetric method revealed soluble phosphorus concentrations of 21.24, 6.67, 11.73, and 17.05 mg·L⁻¹ when lecithin, ferric phosphate, calcium phosphate, and calcium phytate were used as phosphorus sources, respectively. The fermentation conditions for YS-13 were optimized through single-factor experiments combined with response surface methodology, using viable cell count as the response variable. The optimal conditions were determined as 34 °C, 8% inoculum volume, initial pH of 7.55, 48 h incubation, 5 g L⁻¹ NaCl, 8.96 g L⁻¹ glucose, and 8.86 g L⁻¹ peptone, under which the viable cell count reached 6.29 × 10⁸ CFU mL⁻¹, consistent with the predicted value (98.33%, p < 0.05). The plant growth-promoting effect of YS-13 was further validated through a pot experiment using Triticum aestivum cv. Jinchun 6. Growth parameters, including plant height, fresh biomass, root length, root surface area, root volume, and phosphorus content in roots and stems, were measured. The results demonstrated that YS-13 significantly enhanced wheat growth, with a positive correlation between bacterial concentration and growth indicators, although the growth-promoting effect plateaued at higher concentrations. This study successfully identified a high-efficiency phosphate-solubilizing strain, YS-13, and established optimal culture conditions and bioassay validation, laying a foundation for its potential application as a microbial inoculant and providing theoretical and technical support for reducing phosphorus fertilizer inputs and advancing sustainable agriculture. Full article

Molybdenum nitrides are known to have a series of excellent physical properties owing to their unique bonding nature and electronic structure. However, the synthesized samples often exist in nonstoichiometric phases with structural defects (metal or non-metal vacancies), which may influence their performance. Based on the density functional theory, we theoretically studied the vacancy formation in δ-MoN. Various configurations that contained one single vacancy, divacancies, or trivacancies were constructed and systematically studied. It was found that Mo vacancy leads to significant electron loss at the vacant site while N vacancy results in excess electrons being trapped, forming a uniform electron gas region. Detailed analysis revealed that four types of binding clusters are encouraged to form in δ-MoN. The V_Mo–V_N or V_N–V_Mo–V_N (with a sandwich structure) binding is owing to the positive and negative interaction between Mo and N vacancies. The V_N–V_N or V_N–V_N–V_N binding is attributed to the overlap of electron density, but requires N vacancies to be distributed in a specific arrangement. Both Mo and N vacancies induce the anisotropic degradation of electronic conductivity in δ-MoN, with the extent of degradation governed by the vacancy type and concentration. Full article

Molybdenum (Mo) is a vital micronutrient for nearly all living organisms, serving as a cofactor for molybdoenzymes that catalyze essential redox reactions in nitrogen metabolism. Among these enzymes, nitrate reductase plays a crucial role in nitrate assimilation. Maintaining Mo homeostasis—including uptake, storage, and utilization—is critical to avoid both deficiency and toxicity. Our research focuses on uncovering novel molecular components involved in Mo homeostasis, particularly in connection with nitrate assimilation, using Chlamydomonas reinhardtii, a model green microalga. To achieve this, we generated more than 5000 Chlamydomonas transformants through insertional mutagenesis using a paromomycin resistance cassette (AphVIII) and screened them for altered growth on nitrate and under different Mo concentrations. We identified four strains showing altered growth patterns when using nitrate as a nitrogen source or exhibiting increased sensitivity or resistance to Mo. The genomic alterations in these strains were identified. Notably, both a Mo-resistant and a Mo-sensitive transformant had disruptions in the genes that encoded ABC-type transport proteins, indicating a potential role for these proteins in Mo transport. Additionally, two strains were unable to grow on nitrate. One of them had a mutation in the CNX7, a gene involved in Mo cofactor biosynthesis, while the other had a mutation in BAT1, an amino acid transporter. The BAT1 mutant represents an interesting case study, as this gene has not previously been associated with nitrate metabolism. These findings enhance our understanding of Mo and nitrate homeostasis mechanisms and open new paths for engineering microalgae with improved nitrogen assimilation. Full article

Refractory metal-based Mo-Si-B alloys have long been considered the most promising candidates for replacing nickel-based superalloys in the aerospace and energy sector due to their outstanding mechanical properties and good oxidation of the Mo-silicide phases. In general, the addition of vanadium to Mo-Si-B alloys leads to a significant density reduction, while small amounts of titanium provide additional strengthening without changing the phase evolution within the Mo_ss-Mo₃Si-Mo₅SiB₂ phase field. In this work, high-energy ball milling studies on Mo-40V-9Si-8B, substituting both molybdenum and vanadium with 2 and 5 at. % Ti in all constituents, were performed to evaluate the potential milling parameters and investigate the effects of Ti doping on the milling characteristics and phase formation of these multicomponent alloys. After different milling durations, the powders were analysed with regard to their microstructure, particle size, oxygen concentration and microhardness. After heat treatment, the silicide phases (Mo,V)₃Si and (Mo,V)₅SiB₂ precipitated homogeneously within a (Mo,V) solid solution matrix phase. Thermodynamic phase calculations using the CALPHAD method showed good agreement with the experimental phase compositions after annealing, confirming the stability of the observed microstructure. Full article

China is the world’s leading producer of molybdenum–copper concentrates, an industry noted for its high energy demand and considerable environmental burdens. This study applies a cradle-to-gate life cycle assessment to the production of molybdenum–copper concentrate in the Lesser Khingan Mountains, utilizing the ReCiPe 2016 midpoint method coupled with Monte Carlo uncertainty analysis. The results indicate that human carcinogenic toxicity represents the greatest environmental risk, followed by marine and freshwater ecotoxicity. Contribution analysis reveals that the grinding stage is the dominant impact driver—particularly due to hexavalent chromium emissions—affecting carcinogenic risk, climate change potential, and fossil resource depletion. Scenario testing demonstrates that upgrading grinding technology, enhancing electricity efficiency, and substituting conventional energy with renewable sources can markedly mitigate these impacts. However, because of implementation barriers, such as high capital costs, retrofit downtime, and uncertainties in the supply chain, a pilot phase is necessary before deployment at full scale. Quantitatively, the production of one tonne of molybdenum–copper concentrate corresponds to 0.05 DALYs of human health damage, 1.11 × 10⁻⁴ species.year of ecological loss, and USD 3488.82 of resource depletion. These results provide constructive references for the sustainable development of the mining industry and contribute to achieving China’s dual carbon targets through energy transformation and low-carbon technological innovation. Full article

Nanopowders of hydroxyapatite (HA) and Fe-substituted hydroxyapatite (HAFe) were synthesized by wet precipitation on either MCM-41 (a synthetic, mesoporous aluminosilicate material) or an aluminum-containing MCM-41 (AlMCM) support. According to X-ray diffraction data, all of the synthesized materials are composite powders consisting of amorphous silicate and an HA phase with low crystallinity. The presence of aluminum and iron in the structure of the powders resulted in further amorphization. The obtained samples showed high specific surface areas (SSAs), ranging from 162.3 to 186.6 m²/g for MCM-41-HA and from 112.6 to 127.2 m²/g for AlMCM-HA. The hysteresis loops were found to be of type H3, indicating the formation of slit-like pores in the intercrystalline space, as confirmed by transmission electron microscopy, which revealed the presence of lamellar and flake-like particles. Catalytic activity tests showed that the conversion of dibenzothiophene depended on the iron concentration in the material and the acidity of the support. To further improve the catalytic activity of the materials, they were impregnated with molybdenum compounds. Active molybdenum peroxo complexes formed under these conditions enabled 100% conversion of dibenzothiophene. To our knowledge, this is the first study on the influence of MCM-41-HA- or AlMCM-HA-based materials on dibenzothiophene conversion via oxidative desulfurization using hydrogen peroxide as an oxidant. Full article