Search Results (81)

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

Porphyrins play an extremely important role in both photodynamic (PDT) and sonodynamic therapy (SDT). These techniques, which have a lot in common, are largely based on the interaction between the sensitizer and light or ultrasounds (US), respectively, resulting in the formation of reactive oxygen species (ROS) that have the ability to destroy target cells. SDT requires the use of an appropriate frequency of US waves that are able to excite the chemical compound used. In this study, five porphyrin complexes were used: free-base meso-tetra(N-methyl-pyridinium-4-yl)porphyrin (TMPyP) and its transition metal complexes containing zinc(II), palladium(II), copper(II), and chloride-iron(II). The sonodynamic activity of these compounds was studied in vitro. The obtained results confirm the significant relationship between the chemical structure of the macrocycle and its stability and ability to generate ROS. The highest efficiency in ROS generation and high stability were demonstrated by non-metalated compound and its complex with zinc(II), while complex with copper(II), although less stable, were equally effective in terms of ROS production. Antibacterial activity tests showed the unique properties of the tested compounds, including a reduction in the number of both planktonic and biofilm antibiotic-resistant microorganisms above 5 log, which is rare among sonosensitizers. Full article

Synthetic non-metallic nanoparticles (NMNPs) such as carbon nanotubes (CNTs), carbon nanodots (CNDs), and cell-penetrating peptides (CPPs) have been explored to treat harmful algal blooms. However, their strain-specific algicidal activities have been rarely investigated. Here we determined their acute toxicity to nine freshwater cyanobacterial strains belonging to seven genera, including Microcystis aeruginosa UTEX 2386, M. aeruginosa UTEX 2385, M. aeruginosa LE3, Anabaena cylindrica PCC 7122, Aphanizomenon sp. NZ, Planktothrix agardhii SB 1810, Synechocystis sp. PCC 6803, Lyngbya sp. CCAP 1446/10, and Microcoleus autumnale CAWBG635 ATX. We prepared in-house three batches of CNDs using glucose (CND-G) or chloroform and methanol (CND-C/M) as the substrate and one batch of single-walled CNTs (SWCNTs). We also ordered a commercially synthesized CPP called γ-Zein-CADY. The axenic laboratory culture of each cyanobacterial strain was exposed to an NMNP at two dosage levels (high and low, with high = 2 × low) for 48 h, followed by measurement of five endpoints. The endpoints were optical density (OD) at 680 nm (OD₆₈₀) for chlorophyll-a estimation, OD at 750 nm (OD₇₅₀) for cell density, instantaneous pigment fluorescence emission (FE) after being excited with 450 nm blue light (FE₄₅₀) for chlorophyll-a or 620 nm red light (FE₆₂₀) for phycocyanin, and quantum yield (QY) for photosynthesis efficiency of photosystem II. The results indicate that the acute toxicity was strain-, NMNP type-, dosage-, and endpoint-dependent. The two benthic strains Microcoleus autumnale and Lyngbya sp. were more resistant to NMNP treatment than the other seven free-floating strains. SWCNTs and fraction A14 of CND-G were more toxic than CND-G and CND-C/M. The CPP was the least toxic. The high dose generally caused more severe impairment than the low dose. OD₇₅₀ and OD₆₈₀ were more sensitive than FE₄₅₀ and FE₆₂₀. QY was the least sensitive endpoint. The strain dependence of toxicity suggested the potential application of these NMNPs as a target-specific tool for mitigating harmful cyanobacterial blooms. Full article

Fe₂P (iron phosphide) alloys have garnered significant interest in recent years due to their potential applications in permanent magnet materials, particularly in the context of energy-efficient and environmentally friendly technologies. We have sought to tailor the magnetic properties, such as magnetization, coercivity, and Curie temperature, to meet the specific requirements of rare-earth-free permanent magnets for various industrial sectors. In this work, we review recent advancements in the exploration of substitutions (Si, Co, Mn, and Ni) within $\mathrm{F}{\mathrm{e}}_2\mathrm{P}$ alloys aimed at enhancing their magnetic performance as candidates for permanent magnets. The X-ray patterns of (Fe,Co)₂P show great crystallinity with a pure Fe₂P phase even with Mn and Ni substitutions. The Fe₂P structure crystallizes in the P-62m space group. It has been confirmed that the transition metals substitute the 3g Fe-site, sometimes with adverse effects regarding magnetic properties with Co vs. Ni substitution, and that Si substitutes the 2c P-site. The saturation magnetization increases ($M_S=87\mathrm{A}{\mathrm{m}}^2/\mathrm{k}\mathrm{g}$) with Mn substitution, while the Curie temperature decreases with these substitutions. The impact of various substitutional elements on the magnetic properties of $\mathrm{F}{\mathrm{e}}_2\mathrm{P}$ alloys is highlighted, and challenges encountered in this field are reported. Full article

Application of rare earths (RE) as grain refiners is well-known in the technology of aluminum alloys for the automotive industry. In the current study, Al-2.4%Cu-0.4%Mg alloy (coded 220) and Al-7.5%Si-0.35%Mg alloy (coded 356.1), were prepared by melting each alloy in a resistance furnace. Strontium (Sr) was used as a modifier, while titanium boride (TiB₂) was added as a grain refiner. Measured amounts of Ce and La were added to both alloys (max. 1 wt.%). The alloy melts were poured in a preheated metallic mold. The main part of the study was conducted on tensile testing at room temperature. The results show that although RE would cause grain refining to be about 30–40% through the constitutional undercooling mechanism, grain refining with TiB₂ would lead to approximately 90% refining (heterogenous nucleation mechanism). The addition of high purity Ce or La (99.9% purity) has no modification effect regardless of the alloy composition or the concentration of RE. Depending on the alloy ductility, the addition of 0.2 wt.%RE has a hardening effect that causes precipitation of RE in the form of dispersoids (300–700 nm). However, this increase vanishes with the decrease in alloy ductility, i.e., with T6 treatment, due to intensive precipitation of ultra-fine coherent Mg₂Si-phase particles. There is no definite distinction in the behavior of Ce or La in terms of their high affinity to interact with other transition elements in the matrix, particularly Ti, Fe, Cu, and Sr. When the melt was properly degassed using high-purity argon and filtered using a 20 ppi ceramic foam filter, prior to pouring the liquid metal into the mold sprue, no measurable number of RE oxides was observed. In conclusion, the application of RE to aluminum castings would only lead to formation of a significant volume fraction of brittle intermetallics. In Ti-free alloys, identification of Ce- or La-intermetallics is doubtful due to the fairly thin thickness of the precipitated platelets (about 1 µm) and the possibility that most of the reported Al, Si, and other elements make the reported values for RE rather ambiguous. Full article

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline medium that uses electrochemical impedance spectroscopy (EIS) and polarization curves (CPs) at different concentrations and in static mode. The results show that Erbium is the best corrosion inhibitor, containing 50 ppm and reaching an inhibition efficiency of about 89%, and similar result was shown by Sm with an IE~87.9%, while the other rare earths (Nd, Yb and Pr) showed a decrease in corrosion protection at the same concentration, since they were below an IE~80%. On the other hand, with the Langmuir model it was possible to describe that the adsorption process of the three rare earths follows a combined physisorption–chemisorption process to protect the metal’s surface. The observed adsorption free energy, ΔG°ads, reaches −38.7 kJ/mol for Er, −34.4 kJ/mol for Nd, and −33.6 kJ/mol for Pr; whereas Sm and Yb have adsorption free energies of −33.9 and −35.0 kJ/mol, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) further confirmed the formation of a protective film. Their characterization using density functional theory showed the transference of charge from the iron cluster towards the rare earth metal compounds. The adsorption process produced a slightly polarized region of interaction with the metal surface. Also, it was found that the adsorption of the rare earths affected the magnetic properties of the surface of the iron cluster. Quantum chemical descriptors, such as Pearson’s HSAB (Hard and Soft Acids and Bases) descriptors, were useful in predicting the behavior of the flow of electrons between the metal surface and the interacting rare earth ions. Full article

Metal amorphous nanocomposite (MANC) soft magnetic materials exhibit remarkably low iron loss and high saturation magnetization. However, they have not been widely used in electric motors largely due to a lack of demonstrated manufacturing processing methods and an absence of proven motor designs well suited for their use. Recent developments in these two areas have prompted the optimization study of flux-switching with permanent magnet motor topology using MANCs presented here. This study uses population-based optimization in conjunction with a simplified electromagnetics model to seek rare earth-free designs that attain or exceed the state of the art in power density and efficiency. To predict the maximum mechanically safe rotational speed for each design with minimal computational effort, a new method of quantifying the rotor assembly mechanical limit is presented. The resulting population of designs includes motor designs with a specific power of up to 6.1 kW/kg and efficiency of up to 99% without the use of rare earth permanent magnets. These designs, while exhibiting drawbacks of high electrical frequency and significant manufacturing complexity, exceed the typical power density of representative state-of-the-art EV motors while increasing efficiency and eliminating rare earth elements. Full article

In the Wadi Nugrus area, south Eastern Desert of Egypt, A-type granite is highly deformed in a prominent NW-SE trending shear zone, likely related to the Najd shear system. Deformation of this post-collisional leucogranite allows the propagation of hydrothermal alterations due to fluid circulation inside the so-called “Nugrus Shear Zone (NSZ)”. This results in the remarkable destabilization of the magmatic dissemination of rare-metal and U-Th minerals in the granite. Relict magmatic minerals that survived destabilization are represented by (1) ferrocolumbite with 14–63–16.39 wt% FeO^t, (2) fresh igneous zircon, and (3) thorite. The destabilized ore minerals (hydrothermal) dominate over the fresh magmatic relict minerals. The former comprises the following: (1) altered columbite in the form of three distinct phases of niobates (fergusonite–petscheckite–uranopyrochlore), (2) altered thorite (Ce-bearing and P-F-rich), (3) betafite, (4) altered uranothorite, and (5) sulfides (mainly pyrite). It is evident that the destabilization of magmatic thorite can be distinguished into three stages of hydrothermal alteration, namely low-Zr Ce-bearing thorite (stage I), moderate-Zr Ce-bearing thorite (stage II), and high-Zr U-Nb-Y-bearing thorite (stage III). The two varieties of Ce-bearing thorite are sodic with 1.33–2.28 wt% and 1.51–1.80 wt% Na₂O, respectively, whereas the U-Nb-Y-bearing thorite is Na₂O-poor (0.06–0.07 wt%). Similarly, thorite in stages I and II are Ca-, P-, F-, and S-rich. Considerable P₂O₅ content (up to ~17 wt%) is reported in stage II Ce-bearing thorite, whereas stage III thorite is Si-rich (14.56–18.79 wt% SiO₂). Upon hydrothermal destabilization, the three niobate minerals replacing the dissemination of magmatic ferrocolumbite become enriched in UO₂ (up to 15.24 wt%, 7.86 wt%, and 10.88 wt%, respectively), and similarly, ThO₂ (up to 7.13 wt%, 5.71 wt%, and 9.52 wt%, respectively). Hydrothermal destabilization results in the complete dissolution of magmatic fluorite and phosphate minerals at pH = 2–7. This furnishes a source of Ca, P, Ce, Y, F, and Cl in the hydrothermal solution to destabilize/collapse the structure of magmatic ore minerals, particularly ferrocolumbite and thorite. Free elements in the hydrothermal solution are responsible for the crystallization of P- and F-rich Ce-bearing thorite minerals in three stages, as well as abnormal Y₂O₃ enrichment in three resulting niobates that contain up to 6.03 wt%, 2.93 wt%, and 2.65 wt%, respectively. The fresh undeformed Nugrus leucogranite is sulfide-poor. In contrast, sulfides are enriched in the deformed leucogranite inside the NSZ. Also, the intimate relationship of sulfides with destabilized rare-element minerals indicates the destabilization of these minerals during the hydrothermal stage under reduced conditions. Finally, the proposed paragenetic sequence suggests that most ore minerals are magmatic or hydrothermal primarily. In contrast, supergene minerals such as goethite, Fe-oxyhydroxide, altered betafite, and altered uranothorite are the least abundant. Full article

Femtosecond laser pulses are currently regarded as an emerging and promising tool for processing wide bandgap dielectric materials across a variety of high-end applications, although the associated physical phenomena are not yet fully understood. To address these challenges, we propose an original, fully analytical model combined with Two Temperatures Model (TTM) formalism. The model is applied to describe the interaction of fs laser pulses with a typical dielectric target (e.g., Sapphire). It describes the heating of dielectrics, such as Sapphire, under irradiation by fs laser pulses in the range of (10¹²–10¹⁴) W/cm². The proposed formalism was implemented to calculate the free electron density, while numerical simulations of temperature field evolution within the dielectrics were conducted using the TTM. Mathematical models have rarely been used to solve the TTM in the context of laser–dielectric interactions. Unlike the TTM applied to metals, which requires solving two heat equations, for dielectrics the free electron density must first be determined. We propose an analytical model to solve the TTM equations using this parameter. A new simulation model was developed, combining the equations for non-equilibrium electron density determination with the TTM equations. Our analyses revealed the non-linear nature of the physical phenomena involved and the inapplicability of the Beer–Lambert law for fs laser pulse interactions with dielectric targets at incident laser fluences ranging from 6 to 20 J/cm². Full article

In this work, a series of thermosensitive ionic liquid functionalized polymers, PN_x(IL)_y, with controllable morphology and particle size were prepared by free radical polymerization. Then, using the polymer PN₆₄(IL)₈ with uniform morphology as a templating agent, the ZnO composite photocatalytic materials doped with rare earth metal Ce were prepared in combination with a microwave-assisted and templated hydrothermal reaction method. Series different Ce-doping amount photocatalytic materials ZnO-Ce-x‰ were characterized by XRD, SEM, TEM, XPS, and other methods. The results demonstrated that the templated materials PN₆₄(IL)₈ can prepare ZnO-Ce-2‰ with uniform petaloid ambulacra shape, good distribution of elements, and excellent photocatalytic performance. Photocatalytic degradation experiments of methyl orange (MO) showed that when the Ce-doping amount is only 2‰, the degradation rate of organic dyes can reach 96.5% by reacting the photocatalytic materials in water for 1 h. In addition, this kind of photocatalyst can be used for the degradation of high-concentration MO, as well as being easily recovered and effectively reused by simple filtration. Therefore, the structure of this kind of photocatalyst is controllable in the preparation process with an extremely low Ce-doping amount compared with current reports, and it has a good application prospect in the field of wastewater treatment technology. Full article

This study involved the preparation of natural rubber-based composites incorporating varying proportions of heavy metals and rare earth oxides (Sm₂O₃, Ta₂O₅, and Bi₂O₃). The investigation analyzed several parameters of the samples, including mass attenuation coefficients (general, photoelectric absorption, and scattering), linear attenuation coefficients (μ), half-value layers (HVLs), tenth-value layers (TVLs), mean free paths (MFPs), and radiation protection efficiencies (RPEs), utilizing the Monte Carlo simulation software Geant4 and the WinXCom database across a gamma-ray energy spectrum of 40–150 keV. The study also compared the computational discrepancies among these measurements. Compared to rubber composites doped with single-component fillers, multi-component mixed shielding materials significantly mitigate the shielding deficiencies observed with single-component materials, thereby broadening the γ-ray energy spectrum for which the composites provide effective shielding. Subsequently, the simulation outcomes were juxtaposed with experimental data derived from a ¹³³Ba (80 keV) γ-source. The findings reveal that the simulated results align closely with the experimental observations. When compared to the WinXCom database, the Geant4 software demonstrates superior accuracy in deriving radiation shielding parameters and notably enhances experimental efficiency. Full article

Rare earth bisphthalocyanines (MPc₂) are of particular interest because of their behavior as single-molecular magnets, which makes them suitable for applications in molecular spintronics, high-density data storage and quantum computation. Nevertheless, MPc₂ are not commercially available, and the synthesis routes are mainly focused on obtaining substituted phthalocyanines. Two preparation routes depend on the precursor: synthesis from phthalonitrile (PN) and the metalation of free or dilithium phthalocyanine (H₂Pc and Li₂Pc). In both options, byproducts such as free-base phthalocyanine and in the first route additional PN oligomers are generated, which influence the MPc₂ yield. There are three preparation methods for these routes: heating, microwave radiation and reflux. In this research, solvothermal synthesis was applied as a new approach to prepare yttrium, lanthanum, gadolinium and terbium unsubstituted bisphthalocyanines using Li₂Pc and the rare earth(III) acetylacetonates. Purification by sublimation gave high product yields compared to those reported, namely 68% for YPc₂, 43% for LaPc₂, 63% for GdPc₂ and 62% for TbPc₂, without any detectable presence of H₂Pc. Characterization by infrared, Raman, ultraviolet–visible and X-ray photoelectron spectroscopy as well as elemental analysis revealed the main featuresof the four bisphthalocyanines, indicating the success of the synthesis of the complexes. Full article

Background: Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders of heme biosynthesis characterized by severe cutaneous phototoxicity. Afamelanotide, an α-melanocyte-stimulating hormone analogue, is the only approved treatment for protoporphyria and leads to increased light tolerance and improved quality of life (QoL). However, published experience with afamelanotide in the US is limited. Methods: Here, we report on all adults who received at least one dose of afamelanotide at the Massachusetts General Hospital Porphyria Center from 2021 to 2022. Changes in the time to phototoxic symptom onset, QoL, and laboratory parameters were assessed before and during treatment with afamelanotide. Results: A total of 29 patients with protoporphyria were included, 26 of whom (72.2%) received ≥2 afamelanotide implants. Among the patients who received ≥2 implants, the median time to symptom onset following sunlight exposure was 12.5 min (IQR, 5–20) prior to the initiation of afamelanotide and 120 min (IQR, 60–240) after treatment (p < 0.001). Improvements in QoL during afamelanotide treatment were measured using two QoL tools, with good correlation observed between these two instruments. Finally, we found no improvements in the median levels of metal-free erythrocyte protoporphyrin, plasma protoporphyrin, or liver biochemistries during versus prior to the initiation of afamelanotide treatment. Conclusions: This study highlights a dramatic clinical benefit of afamelanotide in relation to light tolerance and QoL in protoporphyria, albeit without improvement in protoporphyrin levels or measures of liver function. Full article

Rare earth elements (REEs) have recently been classified as critical and strategic metals due to their importance in modern society. Research on the geochemical behaviors and mineralization of REEs not only provides essential guidance for mineral exploration but also holds great significance in enhancing our understanding of Earth’s origin and evolution. This paper reviews recent research on the occurrence characteristics, deposit types, and hydrothermal behaviors of REEs, with a particular focus on comparing the complexation and transport of REEs by F, Cl, S, C, P, OH, and organic ligands in fluids. Due to the very weak hydrolysis of REE ions, they predominantly exist as either hydrated ions or free ions in low-temperature and acidic to weakly basic fluids. As the ligand activity increases, the general order of transporting REEs is Cl⁻ ≈ ${\mathrm{S}\mathrm{O}}_4^{2-}$ > F⁻ ≈ ${\mathrm{P}\mathrm{O}}_4^{3-}$ > ${\mathrm{C}\mathrm{O}}_3^{2-}$ > OH⁻ under acidic conditions or OH⁻ > ${\mathrm{S}\mathrm{O}}_4^{2-}$ ≈ Cl⁻ > F⁻ under alkaline conditions. In acidic to neutral hydrothermal systems, the transport of REEs is primarily dominated by ${\mathrm{S}\mathrm{O}}_4^{2-}$ and Cl⁻ ions while the deposition of REEs could be influenced by F⁻, ${\mathrm{C}\mathrm{O}}_3^{2-}$, and ${\mathrm{P}\mathrm{O}}_4^{3-}$ ions. In neutral to alkaline hydrothermal systems, REEs mainly exist in fluids as hydroxyl complexes or other ligand-bearing hydroxyl complexes. Additionally suggested are further comprehensive investigations that will fill significant gaps in our understanding of mechanisms governing the transport and enrichment of REEs in hydrothermal fluids. Full article

In implantology, among the key choices, to obtain predictable results, it is essential to establish, using cone beam computed tomography (CBCT), the bone site and where to insert the implants; during the surgical phase, these sites must be identified on the oral mucosa. Surgical templates are a valid aid, especially in complex cases which require the insertion of more than three or four implants. In cases of a single implant, on the other hand, surgical guides are rarely used, and the implant is often inserted freehand; therefore, the identification of the implant site on the oral mucosa (after choosing the location on the CBCT) is more difficult. For this reason, the clinician uses the teeth in the arch as a reference. This study evaluates the ability of the human eye to identify, on the oral mucosa, where the implant collars will be positioned, the position of which has previously been chosen on the CBCT, in cases where the hands-free surgical technique (without surgical guides) is used. The verification of this precision is carried out using particular thermo-printed templates which contain radiopaque metal spheres. The results show that, in the freehand technique, it is difficult to precisely identify the implant sites (chosen via X-ray) on the mucosa, especially when they are far from natural teeth adjacent to the edentulous area. In case of monoedentulism, the freehand implant technique seems to be applicable by expert implantologists with a reduced risk of error; in fact, clinical experience helps to find the correct correspondence between the implant site chosen on the CBCT and its identification on the mucosa. The level of experience is fundamental in the clinician’s decision about whether or not to use surgical guides; in fact, doctors with little experience should use surgical guides even in the simplest cases to reduce the risk of error. Full article