Search Results (436)

With the increasing emphasis on environmental protection and sustainable development, improving air pollution control technology has become imperative. In this study, Ce-based catalysts are used as research objects to explore the effects of hydrothermal aging on their performance in oxidizing PM. Different Mn, Na, Pt and Zr-doped Ce-based catalysts were prepared based on the impregnation method and the PM oxidation performance of Ce-based catalysts before and after hydrothermal aging was investigated using thermogravimetric experiments, and the catalytic activity change pattern of fresh/hydrothermal aging Ce-based catalysts was analyzed by comparing the comprehensive combustion index S and combustion stability index Rw, revealing the PM oxidation process. The conclusion showed that the cerium-based catalyst significantly enhanced the oxidation efficiency of PM compared with PU. By comparing the performance of different metal-modified catalysts, it was found that the order of activity was: Pt > Na > Mn > Zr. With the metal doping increased, only the comprehensive combustion index S and combustion stability index Rw of Na/CeO₂ catalysts decreased. After hydrothermal aging treatment, the Zr/CeO₂ catalysts showed the best hydrothermal aging resistance, and the comprehensive combustion index S and combustion stability index Rw remained stable (<5%). Ce-based catalysts have the strongest to weakest hydrothermal aging resistance in the following order: Zr > Mn > Pt > Na. This study not only provides an important scientific reference for the application of Ce-based catalysts in the field of environmental purification but also contributes new ideas and methods to promote the green and sustainable development of air pollution control technology. Full article

The appearance of spin-induced ferroelectric polarization in the so-called type-II multiferroic materials has received a lot of attention. The nature and mechanisms of such polarization were intensively studied using perovskite rare-earth manganites, RMnO₃, as model systems. Later, multiferroic properties were discovered in some RFeO₃ perovskites and possibly in some RCrO₃ perovskites. However, R₂NiMnO₆ double perovskites have ferromagnetic structures that do not break the inversion symmetry. It was found recently that more complex magnetic structures are realized in A-site-ordered quadruple perovskites, RMn₃Ni₂Mn₂O₁₂. Therefore, they have the potential to be multiferroics. In this work, dielectric properties in magnetic fields up to 9 T were investigated for such perovskites as RMn₃Ni₂Mn₂O₁₂ with R = Ce to Ho and for BiMn₃Ni₂Mn₂O₁₂. The samples with R = Bi, Ce, and Nd showed no dielectric anomalies at all magnetic fields, and the dielectric constant decreases with decreasing temperature. The samples with R = Sm to Ho showed qualitatively different behavior when the dielectric constant started increasing with decreasing temperature below certain temperatures close to the magnetic ordering temperatures, T_N. This difference could suggest different magnetic ground states. The samples with R = Eu, Dy, and Ho still showed no anomalies on the dielectric constant. On the other hand, peaks emerged at T_N on the dielectric constant in the R = Sm sample from about 2 T up to the maximum available field of 9 T. The Gd sample showed peaks on dielectric constant at T_N between about 1 T and 7 T. Transition temperatures increase with increasing magnetic fields for R = Sm and decrease for R = Gd. These findings suggest the presence of magnetic-field-induced multiferroic states in the R = Sm and Gd samples with intermediate ionic radii. Dielectric properties at different magnetic fields are also reported for Lu₂NiMnO₆ for comparison. Full article

Two copper-containing perovskites Ba_0.8Mn_0.7Cu_0.3O₃ and Cu(4 wt%)/Ba_0.7MnO₃ (selected from previous studies) were tested as catalysts for the CO oxidation reaction under conditions similar to the found in the exhaust of last-generation automotive internal combustion engines. The Cu(4 wt%)/Ba_0.7MnO₃ sample has been selected due to its higher tolerance to CO₂. In order to optimize the performance of this sample for the reaction under study, a Cu(2 wt%)Ce(2 wt%)/Ba_0.7MnO₃ formulation was synthesized, characterized and tested. The excellent catalytic performance of the bimetallic formulation, in terms of CO conversion at low temperatures and tolerance to CO₂, is because cerium improves the redox properties and increases the proportion of reduced copper species on the surface compared to the Cu(4 wt%)/Ba_0.7MnO₃ sample. Full article

Rare earth element (REE) mining exerts profound impacts on aquatic ecosystems, yet the microbial community responses and water quality under such stress remain underexplored. In this study, the surface (0.2 m) and subsurface (1.0 m) water along a spatial transect from proximal to distal points was investigated in a REE-mining area of Ganzhou, China. Physicochemical analyses revealed pronounced gradients of nitrogen (e.g., NH₄⁺−N, NO₃⁻−N), heavy metals (e.g., Mn, Zn, Pb), and REEs (e.g., La, Nd, Ce), with higher accumulation near mining sources and partial attenuation downstream. Dissolved oxygen and redox potential indicated mildly reducing conditions at contaminated points, potentially promoting denitrification and altering nitrogen cycling. Metagenomic sequencing showed significant shifts in microbial community composition, with enrichment of metal- and nitrogen-tolerant taxa, and key denitrifiers (e.g., Acidovorax, Bradyrhizobium, Rhodanobacter), particularly at upstream polluted points. KEGG-based gene annotation highlighted dynamic nitrogen transformations mediated by multiple pathways, including nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and nitrogen fixation. Notably, genes associated with nitrite and nitrate reduction (e.g., nir, nar, nrf) were enriched near mining sources, indicating enhanced nitrogen conversion potential, while downstream activation of nitrogen-fixing genes suggested partial ecosystem recovery. Meanwhile, some microbial such as Variovorax carried metal tolerant genes (e.g., ars, chr, cnr). These findings demonstrate that REE and heavy metal contamination restructure microbial networks, modulate nitrogen cycling, and create localized ecological stress gradients. This study provides a comprehensive assessment of mining-related water pollution, microbial responses, and ecological risks, offering valuable insights for monitoring, restoration, and sustainable management of REE-impacted aquatic environments. Full article

This study aims to develop an AB₂-type Ti-Mn-based alloy with low operating pressure and favorable activation performance for use in a compact hydrogen storage tank. The optimized alloy, Ti_0.75Zr_0.25Cr_0.75Mn_1.2 + 1.5 wt.% Ce, was produced at scale and exhibits a maximum hydrogen storage capacity of 1.87 wt.% and excellent hydrogen activation properties. Furthermore, compositing the mass-produced alloy with 5 wt.% aluminum foam increases the hydride tank’s hydrogen discharge rate by 50%. A prototype aluminum tank containing 57.8 g of hydrogen is demonstrated to stably supply hydrogen to a 220 W fuel cell, enabling continuous operation at rated power output. The work provides a material solution with potential industrial applicability for compact, low-pressure hydrogen storage systems. Full article

Waste glass recycling generates waste streams such as fine glass fraction, waste ceramics containing fine glass, and waste polyethylene plastics. All of the aforementioned streams contain contaminants of organic and inorganic origin that are difficult to remove. This research was conducted to determine technological processes aimed at achieving a circular economy (CE) in the recycling of waste glass. Foam glass was made from the fine-grained, multicolored fraction of contaminated glass, an effective method for recycling glass waste at a low cost. A frothing system based on manganese oxide (MnO₂) and silicon carbide (SiC) was proposed, and an optimum weight ratio of MnO₂/SiC equal to 1.0 was determined. The possibility of controlling the process to achieve the desired foam glass densities was demonstrated. Statistical analysis was used to determine the effect of the MnO₂/SiC ratio and MnO₂ content on the density of the resulting foam glass products. Waste ceramics contaminated with different-colored glass were transformed into ceramic–glass granules. The characteristic temperature curve of the technological process was determined. The metal content in water extracts from ceramic–glass granules and pH value indicate their potential use for alkalizing areas degraded by industry and agriculture. Waste polyethylene-based plastics were converted into polyethylene waxes by thermal treatment carried out in two temperature ranges: low temperature (155–175 °C) and high temperature (optimum in 395 °C). The melting temperature range of the obtained waxes (95–105 °C) and their FTIR spectral characteristics indicate the potential application of these materials in the plastics and rubber industries. The integrated management of all material streams generated in the glass recycling process allowed for the development of a CE model for the glass recycling plant. Full article

Background: Foods containing nutraceuticals from the mineral element group are being developed to compensate for the problem of deficiency in billions of people around the world. This research focuses on essential elements of patented cereal-based mixtures to complement the deficiencies of these elements and, at the same time, assesses their safety in terms of toxic elements in the human diet. Methods: The mineral and trace element contents in the mixtures were determined using the ICP-MS method with a subsequent evaluation of the contributions of the mixtures to the essential and toxic reference values based on dietary intakes and exposures for adults at 60, 80 and 100 kg of adult body weight and a portion size of 50 g. The potential health risk was evaluated using a metal pollution index. Results: The concentrations of minerals and trace elements in the cereal-based mixtures analyzed were as follows: K (up to 4150 µg/g) ≥ P > Mg > Ca > Na > Fe > Zn > Mn > Cu > Al > Ba (up to 4.40 µg/g) > Sr (up to 480 ng/g) ≥ Ti ≥ Ni > Ce ≥ Co > As ≥ Cs > Ag ≥ Li > Se > Be > Cr > Tl > Pb ≥ Hg > Ho > Cd > Sn (up to 1.12 ng/g). The mixtures contribute significantly to the reference values for Mn, Cu, Zn, Fe, and P for adults. Individual dietary exposure values of toxic elements for adults weighing 60 kg decrease in this order: Al (10.1 µg/kg bw/day) > Ni (362 ng/kg bw/day) > As ≥ Pb > Ag > Hg > Cd > and Sn (0.93 ng/kg bw/day). Conclusions: In terms of Regulation (EU) No 1924/2006 of the European Parliament and of the Council on nutrition and health claims made on foods, the cereal-based mixtures could be labelled “source of” Mn, Cu, Zn, Fe, and P when their contributions to the reference values exceeded 15%; in addition, “low sodium/salt” or “very low sodium/salt” can be applied. The mixtures contribute insignificantly to the toxic reference values of Al, Sn, Hg, Cd, Ni, and Ag, and the exposure values of Pb for developmental neurotoxicity, nephrotoxicity, and cardiovascular effects were considered safe. Regarding the metal pollution index of mixtures, there is no concern for potential health effects. Cereal-based mixtures are suitable for use in the food industry as a potential source of beneficial micronutrients for the human diet, although bioaccessible studies should not be neglected. Full article

The profound Phanerozoic destruction of the eastern North China Craton (NCC) is well documented, yet its mechanism remains debated due to limited constraints on thermal state and lithospheric thickness during the Early Cretaceous—the peak period of cratonic destruction. We address this gap through integrated geochemical analysis (major/trace elements, Sr-Nd-Pb isotopes, olivine chemistry) of Early Cretaceous (~125 Ma) Fangcheng basalts from Shandong. These basalts possess high MgO (8.14–11.31 wt%), Mg# (67.23–73.69), Ni (126–244 ppm), and Cr (342–526 ppm). Their trace elements show island arc basalt (IAB) affinities: enrichment in large-ion lithophile elements and depletion in high-field-strength elements, with negative Sr and Pb anomalies. Enriched Sr-Nd isotopic compositions [⁸⁷Sr/⁸⁶Sr(t) = 0.709426–0.709512; ε_Nd(t) = −12.60 to −13.10], unradiogenic ²⁰⁶Pb/²⁰⁴Pb(t) and ²⁰⁸Pb/²⁰⁴Pb(t) ratios (17.55–17.62 and 37.77–37.83, respectively), and slightly radiogenic ²⁰⁷Pb/²⁰⁴Pb(t) ratios (15.55–15.57) reflect an upper continental crustal signature. Covariations of major elements, Cr, Ni, and trace element ratios (Sr/Nd, Sc/La) with MgO indicate dominant olivine + pyroxene fractionation. High Ce/Pb ratios and lack of correlation between Ce/Pb or ε_Nd(t) and SiO₂ preclude significant crustal contamination. The combined isotopic signature and IAB-like trace element patterns support a lithospheric mantle source that was metasomatized by upper crustal material. Olivine phenocrysts exhibit variable Ni (1564–4786 ppm), Mn (903–2406 ppm), Fe/Mn (56.63–85.49), 10,000 × Zn/Fe (9.55–19.55), and Mn/Zn (7.07–14.79), defining fields indicative of melts from both peridotite and pyroxenite sources. High-MgO samples (>10 wt%) in the Grossular/Pyrope/Diopside/Enstatite diagram show a clinopyroxene, garnet, and olivine residue. Reconstructed primary melts yield formation pressures of 3.5–3.9 GPa (110–130 km depth) and temperatures of 1474–1526 °C, corresponding to ~60 mW/m² surface heat flow. This demonstrates retention of a ≥110–130 km thick lithosphere during peak destruction, arguing against delamination and supporting a thermo-mechanic erosion mechanism dominated by progressive convective thinning of the lithospheric base via asthenospheric flow. Our findings therefore provide crucial thermal and structural constraints essential for resolving the dynamics of cratonic lithosphere modification. Full article

Rare earth can modify inclusions in non-oriented silicon steel which is harmful to magnetic properties. This study focused on the 3.1% Si non-oriented silicon steel under industrial production conditions. Samples were taken during the stages before and after addition of rare earth ferrosilicon alloy in Ruhrstahl-Heraeus (RH) unit, different pouring time in tundish, and continuous casting slab. This study systematically examined the morphology, composition, and size distribution of inclusions throughout the smelting process of non-oriented silicon steel by scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), and thermodynamic analysis at liquid steel temperature and thermodynamic analysis of equilibrium solidification. The research results demonstrated that the rare earth treatment ultimately modifies the original Al₂O₃ inclusions in the non-oriented silicon steel into REAlO₃ and RE₂O₂S inclusions, while also aggregating AlN inclusions to form composite inclusions. After rare earth modification, the average size of the inclusions decreases. In the RH treatment process, the inclusions before the addition of rare earth ferrosilicon alloy are mainly AlN and Al₂O₃. After the addition of rare earth ferrosilicon alloy, the inclusions are mainly RES and REAlO₃. In the tundish and continuous casting, the rare earth content decreased, and the rare earth inclusions transform into RE₂O₂S and REAlO₃. For the size of inclusions, after adding rare earth ferrosilicon alloy, the average size of inclusions rapidly decreased from 16.15 μm to 2.65 μm and reach its minimum size 2.16 μm at the end of RH treatment. When the molten steel entered the tundish, the average size of inclusions increased slightly and gradually decreased with the progress of pouring. The average size of inclusions in the slab is 5.79 μm. Phase stability diagram calculation indicates the most stable rare earth inclusion is Ce₂O₂S in molten steel. Thermodynamic calculations indicated that Al₂O₃, Ce₂O₂S, Ce₂S₃, AlN, and MnS precipitate sequentially during the equilibrium solidification process of molten steel. Full article

Plugs of lignite coal from multiple formations were subjected to a series of tests to determine the amount of rare-earth elements (REEs) to be extracted from coal in an in situ mining operation. These tests were used to determine if extraction of REEs and other critical minerals in an in situ environment would be possible for future attempts as an alternative to extraction mining. The tests involved subjecting whole lignite coal plugs from the Twin Butte coal seams in North Dakota to flow-through tests of water, and concentrations of 1.0 M ammonium nitrate, 1.0 M and 1.5 M sulfuric acid, and 1.0 M and 1.5 M hydrochloric acid (HCl) solvents at different concentrations and combinations. The flow-through testing was conducted by alternating the solvent and water flow-through to simulate an in situ mining scenario. The samples were analyzed for their concentrations of REEs (lanthanum [La], cerium [Ce], praseodymium [Pr], neodymium [Nd], samarium [Sm], europium [Eu], gadolinium [Gd], terbium [Tb], dysprosium [Dy], holmium [Ho], erbium [Er], thulium [Tm], ytterbium [Yb], lutetium [Lu], yttrium [Y], and scandium [Sc], as well as germanium [Ge] and cobalt [Co], manganese [Mn], nickel [Ni], and barium [Ba]). Results from the testing showed that REEs were extracted in concentrations that were on average higher using sulfuric acid (8.9%) than with HCl (5.8%), which had a higher recovery than ammonium nitrate. Tests were performed over a standard time interval for comparison between solvents, while a second set of testing was done to determine recovery rates of REEs and critical minerals under certain static and constant flow-through times to determine extraction in relation to time. Critical minerals had a higher recovery rate than the REEs across all tests, with a slightly higher recovery of light REEs over heavy REEs. Full article

In this study, cerium with different ratios (x = 0 (zero), 0.1, 0.15, 0.5) was added to the PrMn structure as an A-site material to evaluate characteristic behavior as a potential cathode material for solid oxide fuel cells. The Pr_xCe_1−xMnO_3−δ electrocatalysts were synthesized using the sol–gel combustion method and were assessed for their electrochemical, phase, and structural properties, as well as desorption and reducibility capabilities. Phase changes, from orthorhombic to cubic structures observed upon cerium additions, were evaluated via the X-Ray diffraction method. X-Ray photoelectron spectroscopy (XPS) showed the valence states of the surface between the Ce⁴⁺/Ce³⁺ and Pr⁴⁺/Pr³⁺ redox pairs, while oxygen temperature programmed desorption (O₂-TPD) analysis was used to evaluate the oxygen adsorption and desorption behavior of the electrocatalysts. Redox characterization, evaluated via hydrogen atmosphere temperature-programmed reduction (H₂-TPR), revealed that a higher cerium ratio in the structure lowered the reduction temperature, suggesting a better dynamic oxygen exchange capability at a lower temperature for the Pr_0.5Ce_0.5MnO_3−δ catalyst compared to the electrochemical behavior analysis by the electrochemical impedance spectroscopy method. Moreover, the symmetrical cell tests with Pr_0.5Ce_0.5MnO_3−δ electrodes showed that, when combined with scandia-stabilized zirconia (ScSZ) electrolyte, the overall polarization resistance was reduced by approximately 28% at 800 °C compared to cells with yttria-stabilized zirconia (YSZ) electrolyte. Full article

Microwave-assisted processing has shown tremendous promise in accelerating chemical reactions and reducing energy consumption through targeted dielectric heating. This study develops MOF-derived Mn-Co and Ce-Co oxide catalysts for energy-efficient benzene oxidation via microwave catalysis. The MnCo spinel oxides (particularly MnCo11-400) exhibit superior microwave absorption and catalytic activity due to enhanced oxygen mobility and tailored dielectric properties. Microwave irradiation enables rapid benzene mineralization over the MnCo11-400 catalyst, achieving 78% conversion at 30 W and complete conversion at 50 W, demonstrating exceptional energy efficiency at low power inputs. Microwaves significantly lower the reaction temperature compared to conventional thermal catalysis (ΔT = 100–250 °C). Stability tests confirm robustness over repeated power cycling (80% conversion retained after 3 × 1 h on/off cycles). Furthermore, an adsorption–microwave oxidation synergistic strategy is demonstrated: pre-adsorbed low-concentration benzene (1.15 mmol) at ambient temperature undergoes complete mineralization within 20 min under 30 W microwave irradiation. The intermittent microwave operation achieves equivalent benzene removal to continuous thermal processing while significantly reducing energy demand. This work establishes MOF-derived spinel oxides as high-performance microwave catalysts for low-temperature VOC abatement. Full article

A series of Ce-doped α-MnO₂ catalysts (Ce_XMn_1−XO₂, x = 0.04, 0.07, 0.10) were synthesized by a simple in situ hydrothermal method. It was confirmed by characterization methods such as XRD, Raman, N₂ adsorption–desorption and SEM confirmed that the introduction of Ce significantly regulated the microstructure of α-MnO₂, specifically manifested as the reduction in grain size, the increase in defect sites, the increase in Mn-O bond length and altered morphological structure. H₂-TPR, O₂-TPD and XPS analyses further revealed the strong interaction between Mn and Ce, accompanied by significant electron transfer (Ce³⁺ + Mn⁴⁺ → Ce⁴⁺ + Mn³⁺), thereby promoting the formation of Mn³⁺ species. In the test of toluene catalytic oxidation performance, C_e0.07Mn_0.93O₂ exhibited the most excellent catalytic activity (T₁₀₀ = 280 °C), while also having good thermal stability and water resistance. Furthermore, the degradation pathways of toluene were analyzed by TD-GC-MS technology: Toluene → Benzene → Benzaldehyde → Maleic anhydride → CO₂ and H₂O. Full article

Shape memory alloys (SMAs) are known for their exceptional mechanical properties, particularly their superior wear resistance compared to conventional alloys with similar surface hardness. Rare earth oxides are often used as additives to further improve these characteristics. This study investigates the effects of different CeO₂ (cerium dioxide) concentrations (0.01 wt.%, 0.1 wt.%, 0.5 wt.%, and 1.0 wt.%) on the properties of CuAlMnFe alloys produced via powder metallurgy (PM). Various analyses were performed, including scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), as well as hardness, wear, and corrosion tests. The increase in wear rate is closely related to the formation of precipitates from CeO₂ addition. Improvements in wear resistance and hardness are attributed to the effects of grain refinement and solid solution strengthening due to CeO₂. Specifically, the wear rate increased from 1.5 × 10⁻³ mm³/(Nm) to 3.4 × 10⁻³ mm³/(Nm) with higher CeO₂ content. Additionally, the friction coefficient of the CuAlMnFe alloy was reduced with CeO₂ addition, indicating enhanced frictional properties. The optimal CeO₂ concentration of 0.5% was found to improve grain uniformity, resulting in better wear resistance. Incorporating CeO₂ particles into CuAlMnFe alloy enhances hardness and reduces wear rate when used in appropriate amounts. Additionally, it exhibits superior corrosion resistance, as evidenced by a positive shift in corrosion potential in Tafel measurements in solutions and a decrease in corrosion current density. The C0.5 specimen showed the highest corrosion potential (E_corr, −588 V) and the lowest corrosion current density (i_corr, 6.17 μA/cm²) during electrochemical corrosion in 3.5 wt.% NaCl solution. Full article

The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical analyses on three drill cores (ZK5101, ZK0301, and ZK1205) spanning the Mn ore body. X-ray diffraction and backscatter electron imaging reveal that the ores are dominated by kutnohorite, with subordinate quartz, calcite, dolomite, and minor sulfides. The low enrichment of U/Al, V/Al, and Mo/Al, as well as positive Ce anomalies, consistently suggest that Mn, in the form of oxides, was deposited in an oxic water column. Carbon isotope compositions of Mn carbonate ores (δ¹³C_VPDB: −2.3 to −6.1‰) and their negative correlation with MnO suggest that Mn carbonate, predominantly kutnohorite, show a diagenetic reduction in pre-existing Mn oxides via organic-matter oxidation in anoxic sediments pore waters. Elemental discrimination diagramms (Mn-Fe-(Co+Ni+Cu) × 10 and Co/Zn vs. Co+Cu+Ni) uniformly point to a hydrothermal Mn source. We therefore propose that hydrothermal fluids supplied dissolved Mn²⁺ to an oxic slope-basin setting, precipitating initially as Mn oxides, which were subsequently transformed to Mn carbonates during early diagenesis. This model reconciles both the hydrothermal and sedimentary-diagenetic processes of the Dongping Mn deposit. Full article