Sc Content Research Articles

Defining the optimal conditions using FFNNs and NARX neural networks for modelling the extraction of Sc from aqueous solution by Cryptand-2.2.1 and Cryptand-2.1.1

The main aim of this study is to figure out how well cryptand-2.2.1 (C 2.2.1) and cryptand-2.1.1 (C 2.1.1) macrocyclic compounds (MCs) work as novel extractants for scandium (Sc) by using an artificial neural network (ANN) models in MATLAB software. Moreover, C2.2.1 and C2.1.1 have never been evaluated to recover Sc. The independent variables impacting the extraction process (concentration of MC, concentration of Sc, pH, and time), and a nonlinear autoregressive network with exogenous input (NARX) and feed-forward neural network (FFNN) models were used to estimate their optimum values. The greatest obstacle in the selective recovery process of the REEs is the similarity in their physicochemical properties, specifically their ionic radius. The recovery of Sc from the aqueous solution was experimentally evaluated, then the non-linear relationship between those parameters was predictively modeled using (NARX) and (FFNN). To confirm the extraction and stripping efficiency, an atomic absorption spectrophotometer (AAS) was employed. The results of the extraction investigations show that, for the best conditions of 0.008 mol/L MC concentration, 10 min of contact time, pH 2 of the aqueous solution, and 75 mg/L Sc initial concentration, respectively, the C 2.1.1 and C 2.2.1 extractants may reach 99 % of Sc extraction efficiency. Sc was recovered from a multi-element solution of scandium (Sc), yttrium (Y), and lanthanum (La) under these circumstances. Whereas, at a concentration of 0.3 mol/L of hydrochloric acid, the extraction of Sc was 99 %, as opposed to Y 10 % and La 7 %. The Levenberg-Marquardt training algorithm had the best training performance with an mean-squared-error, MSE, of 5.232x10−6 and 6.1387x10−5 for C 2.2.1 and C 2.1.1 respectively. The optimized FFNN architecture of 4-10-1 was constructed for modeling recovery of Sc. The extraction process was well modeled by the FFNN with an R2 of 0.999 for the two MC, indicating that the observed Sc recovery efficiency consistent with the predicted one.

Multiphysics Modeling and Analysis of Sc-Doped AlN Thin Film Based Piezoelectric Micromachined Ultrasonic Transducer by Finite Element Method.

This paper presents a Piezoelectric micromechanical ultrasonic transducer (PMUT) based on a Pt/ScAlN/Mo/SiO2/Si/SiO2/Si multilayer structure with a circular suspension film of scandium doped aluminum nitride (ScAlN). Multiphysics modeling using the finite element method and analysis of the effect of different Sc doping concentrations on the resonant frequency, the effective electromechanical coupling coefficient (keff2) and the station sensitivity of the PMUT cell are performed. The calculation results show that the resonant frequency of the ScAlN-based PMUT can be above 20 MHz and its keff2 monotonically rise with the increasing doping concentrations in ScAlN. In comparison to the pure AlN thin film-based PMUT, the static receiving sensitivity of the PMUT based on ScAlN thin film with 35% Sc doping concentration is up to 1.61 mV/kPa. Meanwhile, the static transmitting sensitivity of the PMUT is improved by 152.95 pm/V. Furthermore, the relative pulse-echo sensitivity level of the 2 × 2 PMUT array based on the Sc doping concentration of 35% AlN film is improved by 16 dB compared with that of the cell with the same Sc concentration. The investigation results demonstrate that the performance of PMUT on the proposed structure can be tunable and enhanced by a reasonable choice of the Sc doping concentration in ScAlN films and structure optimization, which provides important guidelines for the design of PMUT for practical applications.

Super-High-Frequency Bulk Acoustic Resonators Based on Aluminum Scandium Nitride for Wideband Applications.

Despite the dominance of bulk acoustic wave (BAW) filters in the high-frequency market due to their superior performance and compatible integration process, the advent of the 5G era brings up new challenges to meet the ever-growing demands on high-frequency and large bandwidth. Al1-xScxN piezoelectric films with high Sc concentration are particularly desirable to achieve an increased electromechanical coupling (Kt2) for BAW resonators and also a larger bandwidth for filters. In this paper, we designed and fabricated the Al1-xScxN-based BAW resonators with Sc concentrations as high as 30%. The symmetry of the resonance region, border frame structure and thickness ratio of the piezoelectric stack are thoroughly examined for lateral modes suppression and resonant performance optimization. Benefiting from the 30% Sc doping, the fabricated BAW resonators demonstrate a large effective electromechanical coupling (Keff2) of 17.8% at 4.75 GHz parallel resonant frequency. Moreover, the temperature coefficient of frequency (TCF) of the device is obtained as -22.9 ppm/°C, indicating reasonable temperature stability. Our results show that BAW resonators based on highly doped Al1-xScxN piezoelectric film have great potential for high-frequency and large bandwidth applications.

Effects of Sc3+ admixture on luminescence and scintillation properties of Ce3+-doped Lu2Y(Al5-xScx)O12 (x = 1, 1.5, 2) garnet single-crystalline films

Effects of Sc3+ admixture on luminescence and scintillation properties were studied in Ce3+ - doped Lu2Y(Al5-xScx)O12 (x = 1, 1.5, 2) garnet single-crystalline films grown by the isothermal liquid phase epitaxy technique. The Ce3+ photoluminescence (PL) was slightly blue shifted with increasing Sc content due to a decrease in crystal field splitting of the Ce3+ 5d levels. In addition, the thermal activation energy of PL quenching, estimated from the temperature dependence of PL decay times, decreased with increasing Sc content. Lu2YAl4ScO12:Ce exhibited the highest light yield (LY) value of 420 photons/MeV at 5.5 MeV α particles along with a fast scintillation decay time constant (τe) of 17.4 ns. At room temperature, the decrease of LY value with increasing Sc content could be attributed to the thermal ionization process.

Enhanced bioaccessibility of curcumin in Pickering emulsions stabilized by solid lipid particles

To investigate curcumin release behavior of Pickering emulsions (PEs) with controlled crystal polymorphism, solid lipid particles (SLPs) were fabricated using Tween 40 (T40-SLPs) or sodium caseinate (SC-SLPs) at 4 °C or 25 °C. T40-SLPs were characterized as β crystal (100%) at 25 °C, and co-crystallization of Tween 40 (2 % by weight (wt.%) vs. 4 wt%) induced formation of β crystals (24.86% vs. 52.88%) at 4 °C. SC-SLPs solely contained α crystals at 4 °C, and addition of sodium caseinate (2 wt% vs. 4 wt%) reduced content of β crystals (7.55% vs. 2.82%) at 25 °C. The indigestibility of β crystals differentiated interfacial digestive behavior of SLPs. PEs stabilized by SC-SLPs underwent more aggregation and released more curcumin upon exposure to pepsin and mucin. High content of β crystals in SC-SLPs enhanced curcumin bioaccessibility in simulated intestinal digestion, whereas high SC concentrations induced undigested SC self-assembled with β crystals, reducing the curcumin bioaccessibility. PEs stabilized by T40-SLPs showed better-targeted delivery, with higher FFA release and curcumin bioaccessibility during in vitro intestinal digestion. Co-crystallization of T40 enriched β crystals in T40-SLPs but reduced the release and bioaccessibility of curcumin. Hence, surface modification of fat crystals and crystal structure determines bioaccessibility of curcumin in PEs stabilized by SLPs.

Synthesis and phase transformations of hexagonal, orthorhombic, and cubic ScxLu1-xFeO3 (0 ≤ x ≤ 1) nanocrystals

Hexagonal, orthorhombic, and cubic ScxLu1-xFeO3 (0 ≤ x ≤ 1) nanocrystals were obtained through solution combustion synthesis with subsequent heat treatment. The structure and phase transformations of the nanocrystals were comprehensively characterized using EDX, PXRD, and 57Fe MS methods. It was observed that an increase in the Sc content within the ScxLu1-xFeO3 structure led to a phase transition from the orthorhombic phase to the hexagonal phase, and further to the bixbyite-type cubic phase. It was determined that the hexagonal phase was present throughout the entire doping range. Hexagonal substitutional solid solutions were stabilized with the content of scandium cations in range of 50–80 mol.%. The substitution limits of scandium for lutetium were determined for each phase. Based on the obtained results, the possibility of controlled synthesis of ScxLu1-xFeO3 nanoparticles with desired composition and crystal structure was successfully demonstrated, that open up the way to the design of novel advanced functional materials.

Effects of Artificial Restoration and Natural Recovery on Plant Communities and Soil Properties across Different Temporal Gradients after Landslides

Landslides cause significant disturbances to mountainous ecosystems and human activities. Due to climate change, the frequency of landslides as secondary disasters has notably increased compared to the past. Further exploration is needed to understand the effects of different restoration methods on post-landslide plant communities and soil properties over different periods of time. In this regard, we selected Lantian County in the northern foothills of the Qinling Mountains as our study area. We conducted surveys on artificially restored and naturally recovered plots at 1, 6, and 11 years after landslide events. Undamaged areas were chosen nearby as control plots. We identified vegetation types and species diversity after artificial and natural recovery and further analyzed the impact of different restoration strategies on vegetation patterns and soil properties. The research results indicate that, compared with natural recovery, artificial restoration can more quickly improve vegetation and soil. With the increasing time gradient, the average ground cover of the herbaceous layer in natural recovery decreased gradually from 47% at year one to 34% at year eleven. In contrast, in artificial restoration, the average ground cover of the herbaceous layer increased from 27% at year one to 44% at year eleven. For the shrub layer, in natural recovery, the average ground cover gradually increased to 39% over eleven years. While in artificial restoration, the average ground cover for the shrub layer gradually increased to 46% over the same period. In the artificial restoration plots, soil pH gradually increased (from 6.2 to 8.2), while TN content gradually decreased (from 1.7 g/kg to 0.9 g/kg). Similarly, TK content decreased (from 22.4 g/kg to 14.5 g/kg), and AP content showed a decreasing trend (from 20.7 mg/kg to 11.4 mg/kg). In the natural recovery plots, DNA content gradually increased (from 3.2 μg/g/d to 142.6 μg/g/d), and SC content gradually increased as well (from 2.4 mg/d/g to 23.1 mg/d/g). In contrast, on sites undergoing natural recovery, the short-term restoration rates of vegetation and soil are lower, but they show greater stability over a longer time. This study provides a new perspective on vegetation restoration strategies and is expected to offer insights for the optimization of post-landslide recovery in the future.

Theoretical investigation of magnetic and thermal properties in Dy1−x Sc x Ni2 series

We report on the thermal and magnetic properties of Dy1−xScxNi2 series compounds (x=0.1,0.3,0.5,and0.7), which were investigated through a model Hamiltonian including the exchange, Zeeman, and crystalline electric field interactions. We investigated the effect of Sc substitution on the Dy site on the magnetic and magnetocaloric properties of these compounds. Theoretical results were simulated for heat capacity, entropy, and the magnetocaloric effect quantities. Our model reproduced the decrease of the magnetic ordering temperature and of the isothermal entropy change peaks as Sc concentration increases. Our theoretical results were confronted with experimental data from the literature, showing good agreement.

Improving the strength and ductility of magnesium alloys by Sc alloying: An experimental and first-principles study

Mg–Sc alloys have great application potential due to the positive effect of Sc on improving corrosion resistance and mechanical properties. In this work, the effects of Sc content on the strength and ductility of Mg-xSc (x=0, 1, 2, 3 at.%) alloys were investigated by experiments and first-principles calculations. The results indicate that, with the increase of Sc content, the hardness, strength, and ductility of the alloys increase significantly. The improvement of strength is attributed to the solid solution strengthening and grain size refinement effect. The addition of Sc reduces the prismatic unstable stacking fault energy of the alloys, thereby promoting the activation of stacking faults and <c+a> dislocations, resulting in the significant improvement of ductility. The mechanism of the enhanced ductility of Mg-xSc solid solution alloys is revealed, which provides guidance for designing high-performance Mg alloys.

A deep insight into the mechanical properties of Mg-Sc alloys through DFT

Mg-Sc alloy is the lightest shape-memory alloy (SMA) discovered so far, offering a new material platform for lightweight SMAs. The main challenge for this system is to reveal its micro-mechanism and tune its performance for practical applications. In this work, we conducted the first-principles calculations to investigate the mechanical properties of Mg-Sc alloys. The effect of Sc content on the martensitic transformation behavior by combining dynamical stability, phonon dispersion and Fermi surfaces analyses were examined. We found that the Sc content should be neither below 15.625 at.% nor above 21.875 at.% to ensure the electronic structure and lattice dynamics stability. The effects of Sc content and rare-earth elements doping on the hardness of Mg-Sc alloys were also explored. We demonstrated that Gd doping can enhance the hardness of Mg-Sc alloys due to the strong interatomic interactions. Our results provide a solid basis for designing high-hardness Mg-Sc-based lightweight SMAs.

The microstructural features and strain recovery characteristics of Ti–V–Al shape memory alloy with minor Sc addition

In the present work, minor Sc addition was employed to control the microstructural features, further optimizing the mechanical/functional performances of Ti–V–Al based shape memory alloy. The results revealed that phase constituents of Ti–V–Al based shape memory alloys were dominated by single αˊˊ martensite phase, regardless of Sc content. Nevertheless, Sc addition caused the significant lattice distortion of Ti–V–Al based shape memory alloy. Meanwhile, the grain size of Ti–V–Al based shape memory alloys were reduced due to Sc addition. Besides, the martensite morphologies evolved from self-accommodation configuration to optimal orientation configuration, but the types of twins kept unchanged. All Ti–V–Al based shape memory alloys showed the reversible αˊˊ→β martensitic transformation in heating curves, irrespective of Sc content. With Sc content increasing, the martensitic transformation temperatures increased linearly due to the chemical composition effect and mechanical effect. Moderate Sc addition was favor to the improvement of thermal cycling stability of Ti–V–Al based shape memory alloys, which can enhance its functional stability. In proportion, the mechanical and functional properties of Ti–V–Al based shape memory alloys firstly increased and then decreased. Ti–V–Al based shape memory alloy with moderate Sc content of 0.025 at.% possess the higher fracture strength of 748.4 MPa, superior ductility of 18.7% and the larger shape memory effect strain of 4.31% under the 8% pre-strain condition. The higher performances in Ti–V–Al shape memory alloy with 0.025 at.% Sc can be attributed to the compressive effect of solution strengthening and grain refinement.

Study of removing radioactive thorium(IV) from high-purity scandium(III) products with di-(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP) in nitric acid solution

Scandium (Sc) is a critical rare earth element. Its compounds are of great concern due to their excellent properties. However, the application is limited by the presence of radioactive impurity thorium (Th). The study aims to remove the radioactive Th(IV) from high-purity Sc2O3 by DEHEHP. The extraction behavior of Sc(III) from HNO3 solution using DEHEHP was also investigated. The effects of HNO3, extractant and salting-out reagent (LiNO3) concentrations on the Sc(III) extraction were studied. The extraction mechanism and thermodynamic parameters were determined. Among the three extractants: Cyanex 923, TBP and DEHEHP, DEHEHP showed the greatest separation ability for Sc(III) and Th(IV) from HNO3 solution. The effects of HNO3, LiNO3, and initial Sc(III) concentrations as well as phase ratio on the separation factor βTh/Sc were investigated. It was indicated that βTh/Sc reached as high as 196 after separation by 30% (v/v) DEHEHP at 3.0 mol L−1 HNO3. The McCabe-Thiele diagram for Th(IV) was plotted. After the six-stage counter-current extraction experiment, the concentration of Th(IV) in the raffinate decreased to 20 mg L−1 from the solution containing 7.71 g L−1 Sc(III) and 692 mg L−1 Th(IV) without the co-extraction of Sc(III). Finally, Sc2O3 of purity >99.99% was obtained.

First-principles calculation of various phase transition in Al–Sc system

Sc as one of the most important microalloying elements in advanced Al alloys has gained tremendous attentions in recent years. The newly identified Sc-rich clusters demonstrate new strengthening effect in Al alloys and thus entail a comprehensive understanding on their phase relationship. In this work, various phase transitions of binary Al–Sc system are systematically investigated by first-principles calculation together with cluster expansion. The results show the phase transition from FCC Al to HCP Sc bypass a BCC structure as a function of Sc concentration. The ordered BCC lattice experiences BCC to FCC, BCC to HCP and BCC to ω phase transitions through the Bain, Burgers and ω phase transition paths, respectively. The possibility of those phase transitions is evaluated from the calculated energy landscape along the transition paths. BCC to FCC and BCC to ω phase transitions are energetically more favorable in Al–Sc system. The bonding electron density and effective cluster interaction suggests the Al–Sc interactions play a key role in individual phase transition at different Sc concentration.

Petrography and geochemistry of the Permian-Triassic boundary interval, Kangjiaping section, South China: Implication for the drastic marine environment change

The Permian-Triassic transitional interval exposed well at Kangjiaping section, northwestern Hunan, South China, contains microbialites, oolitic and oncolitic limestones intercalated with vermiculate micritic limestones in the Lower Triassic overlying the uppermost Permian bioclastic limestones, which provides an excellent opportunity to study the environmental changes after the end-Permian mass extinction (EPME) and the origins and environmental significance of these various anomalous sediments. In this paper, we describe in detail the petrographic and geochemical characteristics of these anomalous sediments, together with the reconstruction of the marine environment after the EPME. The continental margin weathering was significantly enhanced after the EPME, indicated by the higher concentrations of terrigenous minerals, Th, Sc, Sr, and rare earth elements in the Lower Triassic carbonates than in the uppermost Permian bioclastic limestones. Indicators such as V/(V + Ni) and Ni/Co ratios suggest that the oxygen content of shallow seawater significantly decreased after the EPME. While, most samples from the Kangjiaping section preserve a negative cerium anomaly, indicating the shallow seawater was still oxygenated both before and after the EPME. In addition, the abnormally rapid carbonate precipitation rate indicates a supersaturation state with respect to calcium carbonate in the shallow seawater after the EPME, but the depth and salinity of seawater and climate indicated by different microfacies are still different. Under the setting of a rapid transgression after the EPME, the microbialites first deposited on the platform with the exclusion of grazers at the beginning of the Early Triassic, followed by the oncolites formed when the climate turned humid with a relative sea-level rise. The oolites were primarily deposited in an arid climate with a relative sea-level fall, and the salinity and hydrodynamics of seawater controlled the ooids’ grain sizes. In contrast, the (vermiculate) micritic limestones were mainly formed in a humid climate with a relative sea-level rising and more terrigenous inputs. Therefore, the periodic relative sea-level fluctuation and arid-humid climate alternations play a vital role in the evolution and repeat stacking of various microfacies in the Kangjiaping section.

Effect Mechanism of Sc Addition and T6 Heat Treatment on Precipitated Phase and Mechanical Properties of Al‐Cu‐Mn Alloy

The microstructure and mechanical properties of cast Al‐Cu‐Mn alloy influenced by various Sc additions (viz. 0.1, 0.2, 0.3, 0.4, and 0.5 wt%) are investigated. It is found that the grain size of α‐Al and the area proportion of the second phase are decreased with the addition of Sc. In addition, the morphology of the precipitated phase in Al‐Cu‐Mn alloy also evolves at different stages, and the solidification temperature range and initial enthalpy change of the alloy are changed, resulting in the formation of a variety of second‐phase containing Sc. Owing to the grain refinement and precipitation strengthening effects, the hardness of as‐cast alloys is better than T6 alloys. Moreover, it is observed that when the Sc content is 0.3%, the mechanical properties of the as‐cast Al‐Cu‐Mn alloy are the minimum, and the Al‐Cu‐Mn alloys after T6 heat treatment are the maximum. These results confirm that the mechanical properties improvement effect of the as‐cast Al‐Cu‐Mn alloy is greater than that of the T6 heat treatment Al‐Cu‐Mn alloy with the addition of Sc. Meanwhile, the Orowan strengthening mechanism is found to have lost its dominant position.

Effect of Sc content on microstructure characteristics and evolution of W phase in Al–Cu–Li alloys under as-cast and homogenization conditions

In this study, the effect of Sc content on the microstructural characteristics and phase evolution of an Al–Cu–Li alloy under as-cast and homogenization conditions was investigated. The results show the grain refinement effect was distinct when the content of Sc was 0.16 wt%. However, further increased in Sc content resulted in a limited decrease in grain size. Besides, In the 0.16Sc alloy, the flocculent phase with primary Al3(Sc,Zr) phase coexisting with W (Al8-xCu4+xSc) phase appeared, and in the 0.32Sc alloy, the additional blocky primary Al3(Sc,Zr) phase was observed. With the increased of Sc content, the proportion of primary Al3(Sc,Zr) and W phases gradually increased, and the number and size of Al2Cu and Ag-containing Al2CuMg phases at grain boundaries gradually decreased. Two different morphologies of the primary W phase, flocculent and long strip shaped, were revealed within the Sc-containing alloy. The formation of the core-shell structure formed by Al3(Sc,Zr) particles and W phase was generated by the peritectic-eutectic reaction (Liquid + Al3(Sc,Zr)→α-Al + W) and the long strip of W phase was generated by the eutectic reaction (Liquid→α-Al + Al2Cu + W). During the homogenization process, the Al2Cu and Ag-containing Al2CuMg phases were completely re-dissolved after the two previous stages of homogenization, and only a small amount of the spheroidal residual W phase persisted. A subsequent low temperature treatment was employed to allow the Sc atoms that had diffused into the Al matrix to precipitate as Al3(Sc,Zr) dispersoids, resulting in a higher number density of Al3(Sc,Zr) particles for more efficiently utilizing the Sc elements.

Microelements in Dust in the Snow Cover: a Case Study of the Cities of Tyumen and Tobolsk

Received April 5, 2023; revised May 10, 2023; accepted June 27, 2023Inhomogeneities of trace elements content in dust of snow cover were studied in two industrial Siberian cities Tobolsk and Tyumen. The clustering method was used, for which standardized values of the content of trace elements in the snow dust of both cities were used. Eight clusters have been identified, which were divided into two classes by location: Tyumen and Tobolsk. The classes were divided into groups: non-specific and specific ones, of which the two subgroups were distinguished: technogenic and natural. The average values of trace elements in nominal terms were calculated for each cluster. Clusters C1, C2, C4, C7, C8 are characterized by a high content of heavy metals V, Cr, Ni, Cu, Co, Zn, Cd, W, Pb. Background clusters C5 and C6 have a low content of trace elements. Specific technogenic C4 contains more copper than other clusters, and C2 contains more lead. Sources of the formation of technogenic clusters are emissions into the atmosphere of enterprises of the fuel and energy complex, foundry and machine-building industries, and transport. The heterogeneity of the content of microelements in the snow dust under background conditions is demonstrated. The microelements are divided into natural background (cluster C5) and the background with anthropogenic pollution with higher content of Ag and Sn (cluster C6). In urban conditions, a solid phase of snow with a low and minimal content of trace elements in dust (cluster C3) is formed. Increased content of Ni and a reduced content of Pb and Sc is noted in the C3 cluster relative to C5 щту. Using the Mann-Whitne test, it was revealed that the content of trace elements in snow dust within the cities Tyumen and Tobolsk are different for the following elements: Li, V, Cr, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sb, Cs, Ba, Pb. Mean values in are higher than similar ones in Tyumen. The content of Zn, As, Rb, Sc elements in urban clusters differs by more than two times relative to the background ones. In the case of elements Sn, Cs, W, the content of them in the snow dust of Tyumen is higher than that of Tobolsk. The method of clustering makes possible to identify natural background values (C5) and to calculate more precise values of the coefficient Kc as well as to determine the index of the integral pollution. In Tobolsk, the index is indicative of high and dangerous level of pollution, especially in the zone of technogenic impact. The average level is typical for the city of Tyumen.

Cathode Nanophosphors

High-current cathodic pulses on an aluminum electrode in solutions containing sufficiently high concentrations of Mg, Ca, Sr, Al, Sc, Y, or La nitrates in a mixture with H3BO3, HF, H3PO4, or H4P2O7 are accompanied by an intense intrinsic luminescence of a number of heavy metals, the ions of which are captured by salt nanofilms and luminescence under the action of hot electrons when are in an environment characteristic of crystal phosphors. The effect of the cathode nanophosphor (CNP) was found in more than 100 systems; photographs are presented for most of the systems. Ga, In, Tl, Ge, Sn, Pb, Mn, Cu, Ag, Cd, Ce, Tb, and Zr ions were activators. The effect of matrix composition on the spectral and kinetic characteristics of the CNP was shown on several examples; a qualitative description of the phenomenon is given, and the prospects for its application to chemical analysis are considered.

Decoupling of scandium and rare earth elements in organic (nano)particle-rich boreal rivers draining the Fennoscandian Shield

Only few datasets on scandium (Sc) and rare earths and yttrium (REY) in rivers are available and the behaviour of Sc in the hydrosphere is poorly understood. We determined Sc and REY concentrations in the dissolved fraction of twelve boreal rivers in Sweden, which show low conductivity, circumneutral pH and elevated dissolved organic carbon (DOC). Scandium concentrations vary between 189 and 1170 pmol/l and are at the high end of the range reported for rivers worldwide. Unusually high Sc concentrations in the Dalsälven and Västerdalälven could be tracked to the Vanån, a tributary to the headwaters of the latter. Increasing Sc with increasing DOC and Yb concentrations suggest that organic ligands play a major role in the distribution of Sc. The REYSN patterns are similar for all rivers (except the Västerdalälven) and are slightly light REY-depleted with negative Ce and Eu anomalies, and positive Y anomalies. These patterns appear to be a general feature of freshwater draining the Fennoscandian Shield into the Baltic Sea for at least the past 28 years. Our results clearly demonstrate that Sc and REY are fractionated in river waters relative to their crustal source and that they should not be discussed jointly as “REE”.

Room-Temperature Growth of Morphoplastic Scandium Nanowires through Coordination-Induced Self-Assembly for White-Light-Driven Photocatalytic Degradation of Rhodamine

Photoactive nanowires play an important role on the photoelectric-related applications; however, the in situ large-scale growth of photoactive nanowires on the arbitrary substrate still faces a great challenge. Herein, for the first time, we develop a facile coordination-induced self-assembly strategy for preparing the nanowires with high photoactivity through keeping a high concentration of Sc(NO3)3 and tartaric acid (TA) aqueous solution at room temperature. Surprisingly, the nanowires can grow directionally along the direction of water flow on any substrate due to the growth mechanism driven by water molecules, showing that the proposed nanowires are morphoplastic depending on the direction of liquid flow. The formation of nanowires has been proved to be attributed to the synergistic effect of water molecule-involved hydrogen bonding between hydroxyl groups of TA ligands as well as the multi-coordination of Sc3+ ions. Meanwhile, the prepared nanowires are highly photoactive, showing a strong photooxidation ability toward rhodamine 6G dyes, with a degradation efficiency of about 95.8% within 40 min. This finding introduces a coordination growth mechanism of nanowires, which not only provides a great possibility for large-scale and low-cost synthesis of photoactive nanowires with morphoplastic features but also shows a good application prospect in water cleaning by the photocatalysis technique.