Search Results (700)

Cobalt, a rare element in the Earth’s crust, is widely used in industries due to its hardness and antioxidant properties. It also plays a vital role in physiological functions, being a key component of vitamin B₁₂. However, excessive cobalt intake can cause health issues. Detecting cobalt ions, especially Co²⁺, in food is crucial due to potential contamination from various sources. Fluorescent probes offer high sensitivity, selectivity, a rapid response, and ease of use, making them ideal for the accurate and efficient recognition of Co²⁺ in complex samples. In this context, a highly selective fluorescent probe, 2,2′-((3-(1H-benzo[d]imidazol-2-yl)-1,2-phenylene) bis(oxy)) bis(N-(quinolin-8-yl) acetamide) (DQBM-B), was synthesized using chloroacetyl chloride, 8-aminoquinoline, 2,3-dihydroxybenzaldehyde, and benzidine as raw materials for the recognition of Co²⁺. Probe DQBM-B can exhibit fluorescence alone in DMF. However, as the concentration of Co²⁺ increased, Photoinduced Electron Transfer (PET) occurred, which quenched the original fluorescence of the probe. Probe DQBM-B shows better selectivity for Co²⁺ than other ions with high sensitivity (detection limit: 3.56 μmol L⁻¹), and the reaction reaches equilibrium within 30 min. Full article

This work investigated the ion exchange technique for selective separation of rare earth elements (REE) from acid mine drainage (AMD), using different column systems, pH values, and eluent concentrations. Systematic analysis of pH and eluent concentration showed that an initial pH of 6.0 and 0.02 mol L⁻¹ NH₄EDTA are the optimal conditions, achieving 98.4% heavy REE purity in the initial stage (0 to 10 bed volumes). This represents a 32-fold increase compared to the original AMD (6.7% heavy REE). The speciation of REE and impurities was determined by Visual Minteq 4.0 software using pH 2.0, which corresponds to the pH at the inlet of the fractionation column. Under this condition, La and Nd and the impurities (Ca, Mg, and Mn) remained in the fractionation column, while Al was partially retained. In addition, the heavy REE (Y and Dy) were mainly in the form of REE-EDTA complexes and not as free cations, which made fractionation more feasible. The fractionation column minimized impurities, retaining 100% of Ca and 67% of Al, generating a liquor concentrated in heavy REE. This sustainable approach adopted herein meets the critical needs for scalable recovery of REE from diluted effluents, representing a circular economy strategy for critical metals. Full article

Lanthanide rare earth elements possess significant promise for material applications owing to their distinctive optical and magnetic characteristics, as well as their versatile coordination capabilities. This study introduced a lanthanide-functionalized magnetic nanocellulose composite (NNC@Fe₃O₄@La(OH)₃) for effective phosphorus/nitrogen (P/N) ligand separation. The hybrid material employs the adaptable coordination geometry and strong affinity for oxygen of La³⁺ ions to show enhanced DNA-binding capacity via multi-site coordination with phosphate backbones and bases. This study utilized cellulose as a carrier, which was modified through carboxylation and amination processes employing deep eutectic solvents (DES) and polyethyleneimine. Magnetic nanoparticles and La(OH)₃ were subsequently incorporated into the cellulose via in situ growth. NNC@Fe₃O₄@La(OH)₃ showed a specific surface area of 36.2 m²·g⁻¹ and a magnetic saturation intensity of 37 emu/g, facilitating the formation of ligands with accessible La³⁺ active sites, hence creating mesoporous interfaces that allow for fast separation. NNC@Fe₃O₄@La(OH)₃ showed a significant affinity for DNA, with adsorption capacities reaching 243 mg/g, mostly due to the multistage coordination binding of La³⁺ to the phosphate groups and bases of DNA. Simultaneously, kinetic experiments indicated that the binding process adhered to a pseudo-secondary kinetic model, predominantly dependent on chemisorption. This study developed a unique rare-earth coordination-driven functional hybrid material, which is highly significant for constructing selective separation platforms for P/N-containing ligands. Full article

To develop high-performance electrode materials for supercapacitors, in this paper, a heterostructured composite material of cerium sulfide and zinc sulfide quantum dots (CeS₂/ZnS QD) was successfully prepared by hydrothermal method. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) showed that ZnS QD nanoparticles were uniformly composited with CeS₂, effectively increasing the active sites surface area and shortening the ion diffusion path. Electrochemical tests show that the specific capacitance of this composite material reaches 2054 F/g at a current density of 1 A/g (specific capacity of about 256 mAh/g), significantly outperforming the specific capacitance of pure CeS₂ 787 F/g at 1 A/g (specific capacity 98 mAh/g). The asymmetric supercapacitor (ASC) assembled with CeS₂/ZnS QD and activated carbon (AC) retained 84% capacitance after 10,000 charge–discharge cycles. Benefited from the synergistic effect between CeS₂ and ZnS QDs, the significantly improved electrochemical performance of the composite material suggests a promising strategy for designing rare-earth and QD-based advanced energy storage materials. Full article

Spin transport behaviors in heavy metal/ferromagnetic insulator (HM/FI) bilayers have attracted considerable attention due to various novel phenomena and applications in spintronic devices. Herein, we investigate the planar Hall effect (PHE) in Pt/Tm₃Fe₅O₁₂ (Pt/TmIG) heterostructures at low temperatures; moment switching in the ferrimagnetic insulator TmIG is detected by using electrical measurements. Double switching hysteresis PHE curves are found in Pt/TmIG bilayers, closely related to the magnetic moment of Tm³⁺ ions, which makes a key contribution to the total magnetic moment of TmIG film at low temperature. More importantly, a magnetoresistance (MR) curve with double switching is found, which has not been reported in this simple HM/FI bilayer, and the sign of this MR effect is sensitive to the angle between the magnetic field and current directions. Our findings of these effects in this HM/rare earth iron garnet (HM/REIG) bilayer provide insights into tuning the spin transport properties of HM/REIG by changing the rare earth. Full article

The mining sequence of ionic rare earth mineral mining districts is related to the effective utilization of rare earth mineral resources and the protection of ecological environment. This study establishes an optimization model for the mining sequence of ion-adsorption rare earth mining districts that incorporates environmental costs, using the net present value (NPV) of the mining district and the net present value of environmental costs (C_E) as objective functions. The model is applied to optimize the mining sequence of Mining District L. The results demonstrate that (1) Four algorithms, namely NSGA-II, NSGA-III, IBEA, and MOEA/D, were selected for comparison. The analysis based on the distribution of solutions, hypervolume values (HV), and computational time revealed that the IBEA exhibited superior performance. (2) The IBEA was employed to solve the multi-objective optimization problem, yielding a set of 30 optimal solutions. Different NPVs corresponded to different C_E values, with the C_E value increasing correspondingly as the NPV increased. (3) The weighted method was employed to transform the multi-objective optimization problem into a single-objective formulation. Using a genetic algorithm (GA), the optimal solution yielded a decision variable sequence for mining order as [2, 5, 8, 4, 1, 9, 6, 7, 3, 10, 11], with the net present value (NPV) of mining district profits reaching CNY 76,640.65 million and the environmental cost NPV amounting to CNY 19,469.18 million. Compared with the mining sequence optimization scheme that did not consider C_E, although the NPV decreased by CNY 3.3266 million, the C_E was reduced by CNY 10.6993 million. The mining sequence optimization model with environmental costs constructed in this paper provides a scientific decision-making basis for mining enterprises to consider the mining sequence in mining districts, minimize the damage to the ecological environment, and promote the coordinated progress of resource development and sustainable development. Full article

Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr³⁺ in aqueous solutions. Experimental results demonstrated that under optimized conditions (pH = 5, adsorbent dosage = 2.0 g/L, initial Pr³⁺ concentration = 100 mg/L, and adsorption time = 60 min), the removal efficiency of Pr³⁺ reached 79.0%. FT-IR and XPS characterization confirmed the participation of various functional groups on the Spirulina surface in the adsorption process. When 0.1 mol/L HNO₃ was used as the desorption agent, the desorption rate of Pr³⁺ from Spirulina reached 91.7%, demonstrating excellent regeneration performance. At different temperatures (298–318 K), the adsorption data were fitted using Langmuir, Freundlich, Dubinin–Radushkevich, and Redlich–Peterson models. Among them, the Langmuir model (R² ranged from 0.993 to 0.999) provided the best fit, and the adsorption capacity of Spirulina for Pr³⁺ was in the range of 51.10 to 55.31 mg/g. Kinetic studies revealed that the pseudo-second-order model (R² = 0.999) best described the adsorption process, with a rate constant of 0.054 g/(mg·min) (R² was 0.999) at an initial Pr³⁺ concentration of 300 mg/L, indicating chemisorption-controlled behavior. Thermodynamic parameter analysis showed that within the experimental temperature range, ΔG⁰ < 0 and ΔS⁰ > 0, confirming that the adsorption process was spontaneous and endothermic. This study provides a novel technical approach for the green recovery of rare earth elements and highlights the potential of Spirulina biomass in rare earth resource recycling. Full article

Bis(2-ethylhexyl) phosphate (P204) is widely used in extraction processes in the nuclear and rare earth industries. However, its high solubility in water results in high levels of total organic carbon and phosphorus in aqueous environments, and may also lead to radioactive contamination when it is used to combine with radionuclides. In this paper, we characterized a coconut shell activated carbon (CSAC) and a coal-based activated carbon (CBAC) for the adsorption of P204 and then evaluated their adsorption performance through batch and column experiments. The results found that, except for the main carbon matrix, CSAC and CBAC carried rich oxygen-containing functional groups and a small amount of inorganic substances. Both adsorbents had porous structures with pore diameters less than 4 nm. CSAC and CBAC showed good removal performance for P204 under low pH conditions, with removal efficiencies significantly higher than those of commonly used adsorption resins (XAD-4 and IRA900). The adsorption kinetics of P204 conformed to the pseudo-second-order kinetic model, and the adsorption isotherms conformed to the Langmuir model, indicating a monolayer chemical reaction mechanism. Both adsorbents exhibited strong anti-interference capabilities; their adsorption performance for P204 did not change greatly with the ambient temperature or the concentrations of common interfering ions. Column experiments demonstrated that CSAC could effectively fix dissolved P204 with a removal efficiency exceeding 90%. The fixed P204 could be desorbed with acetone. The findings provide an effective method for the recovery of P204 and the regeneration of spent activated carbon, which shows promise for practical applications in the future. Full article

Co_0.95R_0.05Fe₂O₄ nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic Fd-3m structure. XPS shows the presence of Gd³⁺ and Ho³⁺ ions. The spin–orbit splitting of about 15.4 eV observed in Co 2p core-level spectra is an indication that Co is predominantly present as Co³⁺ state, while the satellite structures located at about 6 eV higher energies than the main lines confirm the existence of divalent Co in Co_0.95R_0.05Fe₂O₄. The positions of the Co 3s and Fe 3s main peaks obtained by curve fitting and the exchange splitting obtained values for Co 3s and Fe 3s levels point to the high Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ ratios in both samples. The saturation magnetizations are smaller for the doped samples compared to the pristine ones. For theoretical magnetization calculation, we have considered that the heavy rare earths are in octahedral sites and their magnetic moments are aligned antiparallelly with 3d transition magnetic moments. ZFC-FC curves shows that some nanoparticles remain superparamagnetic, while the rest are ferrimagnetic, ordered at room temperature, and showing interparticle interactions. The M_S/Ms ratio at room temperature is below 0.5, indicating the predominance of magnetostatic interactions. Full article

Co_0.95R_0.05Fe₂O₄ nanoparticles with R = La, Pr, Nd, Sm, and Eu were synthesized via an environmentally friendly sol–gel method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and magnetic measurements. All compounds were found to be single phases adopting a cubic Fd-3m structure. EDS analysis confirmed the presence of Co, Fe, R, and oxygen in all cases. The XPS measurements reveal that the Co 2p core-level spectra are characteristic for Co³⁺ ions, as indicated by the 2p_3/2 and 2p_1/2 binding energies and spin–orbit splitting values. The analysis of the Fe 2p core-level spectra reveals the presence of both Fe³⁺ and Fe²⁺ ions in the investigated samples. The doped samples exhibit lower saturation magnetizations than the pristine sample. Very good agreement with the saturation magnetization values was obtained if we assumed that the light rare-earth ions occupy octahedral sites and their magnetic moments align parallel to those of the 3d transition metal ions. The ZFC-FC curves indicate that some nanoparticles remain superparamagnetic, while others exhibit ferrimagnetic ordering at room temperature, suggesting the presence of interparticle interactions. The M_r/M_s ratio at room temperature reflects the dominance of magnetostatic interactions. Full article

A series of Er³⁺–Tm³⁺–Yb³⁺ tri-doped fluorophosphate glasses with different molar compositions were synthesized using the conventional melt-quenching technique, and their optical properties were measured and analyzed. Under laser excitation at 980 nm, blue, green and red upconverted emissions were observed at around 475, 545 and 660 nm, respectively. Based on the results and the energy level diagrams, energy transfer processes were proposed to explain the population mechanisms of the emitting levels. A final characterization was developed within the framework of the CIE 1931 chromaticity coordinate diagram. Varying the doping concentrations of the optically active rare-earth ions, as well as the laser pumping power, enabled modulation of the three primary colors, resulting in blue, green and relatively close to white light emissions. This tunability of the upconverted emissions highlights the potential of these fluorophosphate glasses as tunable optical devices, laser systems and visual show effects. Full article

A novel type of multifunctional hybrid membranes combining modified chitosan, functionalized multi-walled carbon nanotubes (MWCNTs), and rare earth element ion-imprinted polymers (REEIIPs) were designed and characterized. The synthesized materials were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), X-ray micro-tomography, and Fourier transform infrared spectroscopy (FTIR). The hybrid membranes were also studied in terms of their mechanical and rheological properties. The key element of the proper preparation of hybrid membranes using the casting method in an external magnetic field was to synthesize membrane components with appropriate magnetic properties. It was found that they showed tunable weak ferromagnetic properties, and the increase in modified nanotube addition caused the rise in the membrane’s saturation magnetization, which for Nd-selective hybrid membranes reached 0.44 emu/g. Also, the increase in thermooxidative stability was noted after introducing functionalized nanotubes into polymer matrices, which, in the case of Gd-selective membranes, were stable even up to 730 °C. The rise in the modified MWCNT addition and selection of appropriate REE ion-imprinted polymers improved mechanical (Rm and E values increase even twice) and rheological parameters (almost double growth of E′ and E″ values) of the tested membranes. Synthesized hybrid membranes showed a high rejection of matrix components and an increase in retention ratio with rising MWCNT-REEIIP addition, ultimately reaching 94.35%, 92.12%, and 90.11% for Nd, Pr, and Gd, respectively. The performed analysis confirmed homogeneous dispersion, phase compatibility, network integration, formation of a complex 3D microstructure, and improved operational stability of created hybrid membranes, which is significant for their future applications in Nd, Pr, and Gd recovery from coal fly ash extracts. Full article

Using the s-d model and Green’s function theory, we investigated for the first time the electron and hole doping effects on the magnetic and optical properties of the double perovskites ${\mathrm{Ba}}_2{\mathrm{FeMoO}}_6$ (BFMO) and ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ (SFMO). Our aim was to find the doping ions that lead to an increase in Curie temperature $T_C$. On the basis of a competition mechanism between spin exchange and s-d interactions, we explain at a microscopic level the decrease in magnetization M and band gap energy $E_g$, as well as the increase in $T_C$ of BFMO and SFMO through substitution with rare earth ions at the Ba(Sr) sites. The influence of doping with K at the Ba(Sr) and Co at the Fe sites on the magnetic properties and the band gap is also discussed. A very good qualitative coincidence with the existing experimental data was observed. Moreover, we found that both M and $T_C$ decrease with decreasing the size of BFMO and SFMO nanoparticles. Full article

Rare earth metals (REMs) are vital for high-tech industries, but their extraction from secondary sources is challenging due to environmental and technical constraints. This study investigates the ion-exchange extraction of light REMs (neodymium, praseodymium, and samarium) from sulfuric and phosphoric acid solutions, modeling industrial leachates from apatite concentrates and phosphogypsum. The study considers the use of anion- and cation-exchange resins with different functional groups for efficient and environmentally safe REM separation. Experimental sorption isotherms were obtained under static conditions at 298 K and analyzed using a thermodynamic model based on the linearization of the mass action equation. Equilibrium constants and Gibbs energy were calculated, which reveals the spontaneity of the processes. Cation-exchange resins demonstrated high selectivity towards individual REMs, while anion-exchange resins were suitable for group extraction. Infrared spectral analysis confirmed the presence of sulfate and phosphate complexes in the resin matrix, clarifying the ion-exchange mechanisms. Thermal effect measurements indicated exothermic sorption on anion-exchange resins with negative entropy and endothermic sorption on cation-exchange resins with positive entropy. The findings highlight the potential of ion-exchange resins for selective and sustainable REM recovery, offering a safer alternative to liquid extraction and enabling the valorization of industrial wastes like phosphogypsum for resource recovery. Full article

The El Bola mafic–ultramafic intrusion (EBMU) in Egypt’s Northern Eastern Desert represents an example of Neoproterozoic post-collisional layered mafic–ultramafic magmatism in the Arabian–Nubian Shield (ANS). The intrusion is composed of pyroxenite, olivine gabbro, pyroxene gabbro, pyroxene–hornblende gabbro, and hornblende-gabbro, exhibiting adcumulate to heter-adcumulate textures. Mineralogical and geochemical analyses reveal a coherent trend of fractional crystallization. Compositions of whole rock and minerals indicate a parental magma of ferropicritic affinity, derived from partial melting of a hydrous, metasomatized spinel-bearing mantle source, likely modified by subduction-related fluids. Geothermobarometric calculations yield crystallization temperatures from ~1120 °C to ~800 °C and pressures from ~5.2 to ~3.1 kbar, while oxygen fugacity estimates suggest progressive oxidation (log fO₂ from −17.3 to −15.7) during differentiation. The EBMU displays Light Rare Earth element (LREE) enrichment, trace element patterns marked by Large Ion Lithophile Element (LILE) enrichment, Nb-Ta depletion and high LILE/HFSE (High Field Strength Elements) ratios, suggesting a mantle-derived source that remained largely unaffected by crustal contribution and was metasomatized by slab-derived fluids. Tectonic discrimination modeling suggests that EBMU magmatism was triggered by asthenospheric upwelling and slab break-off. Considering these findings alongside regional geologic features, we propose that the mafic–ultramafic intrusion from the ANS originated in a tectonic transition between subduction and collision (slab break-off) following the assembly of Gondwana. Full article