Novel nitrogen-rich hydrogel adsorbent for selective extraction of rare earth elements from wastewater.

Efficient recovery of rare earth elements (REEs) from wastewater is crucial for advancing resource utilization and environmental protection. Herein, a novel nitrogen-rich hydrogel adsorbent (PEI-ALG@KLN) was synthesized by modifying coated kaolinite-alginate composite hydrogels with polyethylenimine through polyelectrolyte interactions and Schiff's base reaction. Various characterizations revealed that the high selective adsorption capacity of Ho (155 mg/g) and Nd (125 mg/g) on PEI-ALG@KLN is due to a combination of REEs (Lewis acids) via coordination interactions with nitrogen-containing functional groups (Lewis bases) and electrostatic interactions; its adsorption capacity remains more than 85 % after five adsorption-desorption cycles. In waste NdFeB magnet hydrometallurgical wastewater, the recovery rate of PEI-ALG@KLN for Nd and Dy can reach more than 93 %, whereas that of Fe is only 5.04 %. Machine learning prediction was used to evaluate adsorbent properties via different predictive models, with the random forest (RF) model showing superior predictive accuracy. The order of significance for adsorption capacity was pH > time > initial concentration > electronegativity > ion radius, as indicated by the RF model feature importance analysis and SHapley Additive exPlanations values. These results confirm that PEI-ALG@KLN has considerable potential in the selective extraction of REEs from wastewater.

Mitigating gadolinium toxicity in guar (Cyamopsis tetragonoloba L.) through the symbiotic associations with arbuscular mycorrhizal fungi: physiological and biochemical insights.

BACKGROUND: Gadolinium (Gd) is an increasingly found lanthanide element in soil; thus, understanding its impact on plant physiology, biochemistry, and molecular responses is crucial. Here, we aimed to provide a comprehensive understanding of Gd (150 mg kg- 1) impacts on guar (Cyamopsis tetragonoloba L.) plant yield and metabolism and whether the symbiotic relationship with arbuscular mycorrhizal fungi (AMF) can mitigate Gd toxicity of soil contamination. RESULTS: AMF treatment improved mineral nutrient uptake and seed yield by 38-41% under Gd stress compared to non-inoculated stressed plants. Metabolic analysis unveiled the defense mechanisms adopted by AMF-treated plants, revealing carbon and nitrogen metabolism adaptations to withstand Gd contamination. This included an increase in the synthesis of primary metabolites, such as total sugar (+ 39% compared to control), soluble sugars (+ 29%), starch (+ 30%), and some main amino acids like proline (+ 57%) and phenylalanine (+ 87%) in the seeds of AMF-treated plants grown under Gd contamination. Furthermore, fatty acid and organic acid profile changes were accompanied by the production of secondary metabolites, including tocopherols, polyamines, phenolic acids, flavones, and anthocyanins. CONCLUSIONS: Overall, the coordinated synthesis of these compounds underscores the intricate regulatory mechanisms underlying plant-AMF interactions and highlights the potential of AMF to modulate plant secondary metabolism for enhanced Gd stress tolerance.

The research progress of rare earth agricultural light conversion film.

The light-converting agricultural film is a new high-end functional film that can convert ultraviolet light and yellow-green light, which is harmful or useless to plant photosynthesis, into red-orange light or blue-violet light required for photosynthesis. The potential advantages of light-converting agricultural film in efficiently utilizing solar energy and improving crop yield have attracted more and more attention from researchers and agricultural enterprises.The light-converting function is realized by adding a light-converting agent to the agricultural film. Therefore, the preparation of light-converting agents with excellent performance is the core of the development and utilization of light-converting agricultural films. The paper firstly summarizes the key research and development in the field of agricultural light-converting films in china. Then this paper summarizes the classification of light-converting agents, research progress, and preparation methods. Finally, this paper predicts the future development trend of light-converting agricultural films, in order to provide a reference for the research and development of stable and efficient light-converting agricultural films.

Polypod Carboxylic Acid-Rare Earth Complex with High Cyclic Stability for Nitrobenzene Compound Detection.

The 5',5''-bis(4-carboxyphenyl)-[1,1':3',1'':3'',1'''-quaterphenyl]-4,4'''-dicarboxylic (H4L1) ligand has a large conjugated rigid planar structure and good absorption of ultraviolet radiation, which can provide effective "antenna effect". However, rare earth complexes using H4L1 as the sole ligand have not been reported. In this paper, rare earth Eu was combined with H4L1 ligand to produce organic rare earth composite L1-Eu by solvothermal synthesis method. It was found through fluorescence spectroscopy that the emission of L1-Eu complex has a linear response to nitrobenzene compounds. The L1-Eu composite material has a low detection limit for nitrobenzene compounds, with detection limits of 0.910, 8.401, 24.510, and 8.171 µM for nitrobenzene, o-nitrophenol, m-nitrophenol, and p-nitrophenol, respectively. Further more the L1-Eu complex can sensitively respond to nitrobenzene compounds while resisting interference from common metal ions and organic solvents. In particular, L1-Eu composite material has good stability and recyclability. Therefore, L1-Eu composite material can serve as a fluorescent probe for specific detection of nitrobenzene compounds. We believe that the L1-Eu complex provides a new method for fluorescence detection of nitrobenzene compounds.

Harnessing 4f Electron Itinerancy for Integrated Dual-Band Redox Systems Boosts Lithium-Oxygen Batteries Electrocatalysis.

In-depth comprehension and manipulation of band occupation at metal centers are crucial for facilitating effective adsorption and electron transfer in lithium-oxygen battery (LOB) reactions. Rare earth elements play a unique role in band hybridization due to their deep orbitals and strong localization of 4f electrons. Herein, we anchor single Ce atoms onto CoO, constructing a highly active and stable catalyst with d-f a dual-band redox center. It is discovered that the itinerant behavior of 4f electrons introduces an enhanced spin-orbit coupling effect, which facilitates ideal σ/π bonding and flexible adsorption between the Ce/Co active sites and *O. Simultaneously, the injection of localized Ce 4f electrons strengthens the orbital bonding capacity of Co-O, effectively inhibits the dissolution of Co sites and improves the structural stability of the cathode material. Bracingly, the Ce1/CoO-based LOB exhibits an ultra-low charge-discharge polarization (0.46 V) and stable cyclic performance (1088 hours). This work breaks through the traditional limitations in catalyst activity and stability, providing new strategies and theoretical insights for developing high-performance LOBs powered by rare-earth elements.

A self-isolated acid-tolerant Parachlorella kessleri with high efficiency in treating rare earth mining sewage.

Rare earth mining sewage is a significant environmental concern due to its high acidity and ammonia nitrogen levels. Finding a sustainable and cost-effective treatment method is essential. Parachlorella kessleri FM2, a green algae strain isolated in-house, has demonstrated remarkable abilities to grow and remove ammonia nitrogen (NH4+-N) from highly acidic rare earth wastewater without the need for alkaline additives. After optimizing conditions, P. kessleri FM2 achieved an impressive NH4+-N removal rate of 7.94 mg/L/d and a removal efficiency of 98.71% in a 1.5-L photobioreactor. In semi-continuous culture, the average NH4+-N removal rate remained high at 6.67 mg/L/d. When scaled up to continuous culture in a 5-L photobioreactor, P. kessleri FM2 maintained stability with an NH4+-N removal rate of 6.79 mg/L/d. Additionally, we conducted a preliminary analysis of P. kessleri FM2's acid resistance mechanism, further highlighting its potential as a candidate for treating acidic wastewater.

A detailed investigation of rare earth lanthanum substitution effects on the structural, morphological, vibrational, optical, dielectric and magnetic properties of Co-Zn spinel ferrites.

In this work, Co0.5Zn0.5LaxFe2-xO4 (0.00 ≤ x ≤ 0.10) spinel ferrites were synthesized using the sol-gel auto-combustion method. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the presence of a cubic spinel structure. The crystallite size was estimated to be between 17.5 nm and 26.5 nm using Scherrer's method and 31.27 nm-54.52 nm using the Williamson-Hall (W-H) method. Lattice constants determined from XRD and Rietveld refinement ranged from (8.440 to 8.433 Å and 8.442 to 8.431 Å), respectively. Scanning electron microscopy (SEM) revealed a non-uniform distribution of morphology with a decrease in particle size. The bandgap values decreased from 2.0 eV to 1.68 eV with increasing rare earth (La3+) doping concentration. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of functional groups and M-O vibrations. The dielectric constant and dielectric loss exhibited similar behavior across all samples. The maximum tan δ value obtained at lower frequencies. Regarding magnetic behavior, there was a decrease in magnetization from 55.84 emu/g to 22.08 emu/g and an increase in coercivity from 25.63 Oe to 33.88 Oe with higher doping concentrations. Based on these results, these materials exhibit promising properties for applications in microwave and energy storage devices.

(Y3+/Sm3+)-doped and co-doped CoFe2O4 for heterogeneous advanced oxidation process: structural, magneto-optical, and photocatalytic investigations.

The photocatalytic properties of CoFe2O4 nanoparticles were activated by the doping and co-doping of a low level of Y3+ and Sm3+ cations. After optimizing the annealing temperature, 900 °C was found to be the optimal temperature for the successful incorporation of Y3+ and Sm3+ into the spinel structure. The purity of our samples annealed at 900 °C was confirmed using several characterization methods, including PXRD, SEM, XPS, VSM, FTIR, and Raman spectroscopy. Thus, we were able to increase the photocatalytic degradation of orange G dye from 9.9 to 64.63% for the Sm3+-doped sample, 76.42% for the Y3+-doped sample, and even 85.81% for the co-doped sample under 60 min of UV-visible light irradiation. The beneficial effect of samarium and yttrium doping and co-doping is attributed to several factors: the first factor is doped and co-doped rare earth impurities induce distortion in the lattice, the larger the ionic radii of dopant element, the highest is the photocatalytic activity; second factor, upon doping and co-doping of rare earth impurities in the structure of CoFe2O4 leads to the creation of donor state level within the band gap, causing the Fermi energy to shift near the conduction band. Third factor, co-doping produced strong interactions, which accelerated photocarrier mobility and transport; lastly, longer electron-holes lifetime. We have provided a detailed study of the structural, vibrational, and optical properties to support our conclusions.

Rare Earth Er-Nd Dual Single-Atomic Catalysts for Efficient Visible-light Induced CO2 Reduction to CnH2n+1OH (n=1, 2).

Efficient synthesis of CnH2n+1OH (n=1, 2) via photochemical CO2 reduction holds promise for achieving carbon neutrality but remains challenging. Here, we present rare-earth dual single atoms (SAs) catalysts containing ErN6 and NdN6 moieties, fabricated via an atom-confinement and coordination method. The dual Er-Nd SAs catalysts  exhibit unprecedented generation rates of 1761.4 µmol g-1 h-1 and 987.7 µmol g-1 h-1 for CH3CH2OH and CH3OH, respectively. Through a combination of theoretical calculation, X-ray absorption near edge structural analysis, aberration-corrected transmission electron microscopy, and in-situ FT-IR spectroscopy, we demonstrate that the Er SAs facilitate charge transfer, serving as active centers for C-C bond formation, while Nd SAs provide the necessary *CO for C-C coupling in C2H5OH synthesis under visible light. Furthermore, the experiment and density functional theory calculation elucidate that the variety of electronic states induced by 4f orbitals of the Er SAs and the p-f orbital hybridization of Er-N moieties enable the formation of charge-transfer channel. Therefore, this study sheds light on the pivotal role of *CO adsorption in achieving efficient conversion from CO2 to CnH2n+1OH (n=1, 2) via a novel rare-earth-based dual SAs photocatalysis approach.

New Insights on Y, La, Nd, and Sm Extraction with Bifunctional Ionic Liquid Cyphos IL 104 Incorporated in a Polymer Inclusion Membrane.

In this study, an ionic liquid-based polymer inclusion membrane (IL-PIM) made of (50% polymer-50% CyphosIL104) was used to extract and separate the rare earth elements (REEs) Y, La, Nd, and Sm in chloride solutions. The effect of extraction time and pH was studied to optimize the extraction and separation conditions. The four REEs were effectively extracted at pH 4-5 from both single and mixed metals solutions. However, at pH 2, only Y was extracted. The recovery of the extracted REEs from the loaded PIM was achieved using HNO3 and H2SO4. In the case of La, it was quantitatively back-extracted with H2SO4 after a contact time of 1 h, while up to 4 h was necessary to recover 70% of the extracted Y, Sm, and Nd. Extraction isotherms were studied, and the Freundlich isotherm model was the most adequate to describe the interaction between the PIM and the REEs. Finally, the developed PIM was investigated for the extraction of REEs from mixtures containing other metals, which showed great selectivity for the REEs.

f-π* Back Bonding Orbital Induced by Lutetium-Based Conducting MOF Promotes Highly Selective CO 2 to CH 4 at Low Potential.

The research on electrocatalytic carbon dioxide reduction (ECR) catalysts using renewable energy is particularly crucial in energy conversion studies, especially for viable hydrocarbon production. This study employs density functional theory calculations to screen a series of non-radioactive lanthanide two-dimensional metal-organic frameworks (MOFs) for product selectivity in ECR. Based on theoretical screening, our focus is on a lutetium (Lu)-based conducting MOF (Lu-HHTP), which exhibits a Faradaic efficiency of approximately 77% for methane (CH4) production and maintains a stable current density of -280 mA/cm2 at -1.1 V vs. RHE. In situ electrochemical experiments and material characterization demonstrate that the Lu sites possess high coordination stability and structural recoverability during catalytic CO2 reduction, attributed to the overlap between Lu's f-orbitals and the π*-orbitals of the ligand O, and the formation of back bonding orbitals between the f-orbitals of Lu and the π* orbitals of CO contribute increasing CH4 selectivity and lowering the potential. This study leverages rare-earth MOF-type materials, offering a novel approach to addressing low conductivity and stabilizing rare-earth materials, thereby establishing a theoretical framework for the conversion of linearly adsorbed *CO into hydrocarbons.

Synergistic effects of rare-earth ions (Ho, Yb) doping on the photo-catalytic efficacy of V2O5 for removal of pollutants from industrial waste water.

The co-doping of vanadium pentoxide (V2O5) with rare-earth (RE) elements, namely 1.5 % holmium (Ho) and 1.5 % ytterbium (Yb) has been conducted using an eco-friendly, straightforward hydrothermal approach to assess the combined effects on structural, optical, and photocatalytic properties. The application of the density functional theory (DFT) approach effectively examined the impact of RE ions on the photocatalytic efficiency of co-doped V2O5. The stable orthorhombic crystal structure of co-doped V2O5 has been confirmed using DFT and X-ray diffraction without a secondary phase. It appears that homogeneous nucleation occurs while heterogeneous nucleation slows down in co-doped samples, as evidenced by the larger crystallite sizes in co-doped samples compared to doped ones. It means a result, the co-doped samples exhibit photodegrades more quickly and have a higher rate constant than the doped samples. This is because they have less dislocation density (4.26 × 10-3 nm-2) and internal micro-strain (4.93 × 10-3). The bandgap and degradation efficiency are determined by the UV-vis spectroscopy and found to be 2.33 eV and 95 %, respectively, at the optimal pH of 7 in the visible range. The co-doped sample has a rate constant of 24 × 10-3 min-1, which is the highest in the RE-doped V2O5 system. This is a good reason to think of co-doped V2O5 as a possible catalyst.

Exploiting Deep-Ultraviolet Nonlinear Optical Material Rb2ScB3O6F2 Originated from Congruously Oriented [B3O6] Groups.

The exploration and research for deep-ultraviolet (UV) nonlinear optical (NLO) crystals are of great significance for all-solid-state lasers. This work is based on the excellent structural [B3O6] units which manipulate the excellent performances of famous commercial NLO crystal ß-BaB2O4 (ß-BBO) to explore new alternatives of deep-UV NLO materials. A deep-UV rare-earth metal borate fluoride Rb2ScB3O6F2 (RSBF) is successfully designed by combining the heterovalent ions substitution strategy, and fluorination strategy. Expectedly, RSBF exhibits an extremely short cutoff edge below 175 nm (189 nm for ß-BBO), and a moderate birefringence of 0.088 at 1064 nm. The shortest phase-matching (PM) wavelength of RSBF (λPM = 182 nm) is shortened by 23 nm compared with ß-BBO (λPM = 205 nm) due to the improvements in the chromatic dispersion and cutoff edge, and an experimental frequency-doubling effect 1.4×KDP further suggests that RSBF can output a deep-UV harmonic laser. This work provides new sights from the original influencing factors for the rational and purposeful design of deep-UV NLO materials.

Rare earth europium recovery using selective metal-organic framework incorporated mixed-matrix membrane.

Rare-earth elements (REEs) play a crucial role in state-of-the-art technologies and sustainable energy generation. However, conventional production methods of REE often instigate detrimental impacts on environment. Hence, the development of efficient and sustainable hydrometallurgical methods for REE recovery from complex solution has become a crucial research focus. This study investigates a mixed-matrix membrane composed of a highly europium selective metal-organic framework-based adsorbent, Cr-MIL-PMIDA, embedded in sulfonated poly(ether ketone) (SPEK) polymer membrane matrix to preferentially concentrate europium (Eu3+) ions in the presence of other competing cations. The activated membrane notably reduced ionic conductivity for Eu3+ compared to other multivalent ions. Membrane extraction experiments further confirmed the selective behavior, demonstrating slower diffusion for Eu3+ compared to Mg2+ and Zn2+ cations. Especially, at pH 5, Mg2⁺ and Zn2⁺ recovery was greater than 30%, whereas Eu³âº recovery remained lower than 4%. We propose that the strong chemical affinity between the phosphate group and Eu3+ help partition of the Eu3+ ions in the membrane phase and inhibit the diffusion and further partitioning of the Eu3+ ion from bulk solution. Furthermore, we demonstrate the stability of the composite membrane and the embedded MOF particles in aqueous solution for up to 12 days without degradation, attributing it to the robust chemical stability of the MOF structure.

Selectively recovering rare earth elements with carboxyl immobilized metal-organic framework from ammonium-rich wastewater.

The material with high adsorption capacity and selectivity is essential for recovering rare earth elements (REES) from ammonium (NH4+-N)-rich wastewater. Although the emerging metal-organic framework (MOF) has gained intensive attention in REES recovery, there are scientific difficulties unsolved regarding restricted adsorption capacity and selectivity, hindering its extensive engineering applications. In this work, a diethylenetriamine pentaacetic (DTPA)-modified MOF material (MIL-101(Cr)-NH-DTPA) was prepared through an amidation reaction. The MIL-101(Cr)-NH-DTPA showed enhanced adsorption capacity for La(III) (69.78 mg g-1), Eu(III) (103.01 mg g-1) and Er(III) (83.41 mg g-1). The adsorption isotherm and physical chemistry of materials indicated that the adsorption of REEs with MIL-101(Cr)-NH-DTPA was achieved via complexation instead of electrostatic adsorption. Such complexation reaction was principally governed by -COOH instead of -NH2 or -NO2. Meanwhile, the resulting material remained in its superior activity even after five cycles. Such a constructed adsorbent also exhibited excellent selective adsorption activity for La(III), Eu(III), and Er(III), with removal efficiency reaching 70% in NH4+-N concentrations ranging from 100 to 1500 mg L-1. This work offers underlying guidelines for exploitation an adsorbent for REEs recovery from wastewater.

Enhanced rare earth element recovery with cross-linked glutaraldehyde-lanthanide binding peptides in foam-based separations.

HYPOTHESIS: Lanthanide Binding Tag (LBT) peptides that coordinate selectively with lanthanide ions can be used to replace the energy intensive processes used for the separation of rare earth elements (REEs). These surface-active biomolecules, once selectively complexed with the trivalent REE cations, can adsorb to air/aqueous interfaces of bubbles for foam-based REEs recovery. Glutaraldehyde, an organic compound that is a homobifunctional crosslinker for proteins and peptides, can be used to enhance the adsorption and interfacial stabilization of lanthanide-bound peptides films. EXPERIMENTS: The stability of the interfacial cross-linked films was tested by measuring their dilational and shear surface rheological properties. Surface activity of the adsorbed species was analyzed using pendant drop tensiometry, while surface density and molecular arrangement were determined using x-ray reflectivity and x-ray fluorescence near total reflection. FINDINGS: Glutaraldehyde cross-linked REE-peptide complexes enhance the adsorption of lanthanides to air-water interfaces, resulting in thicker interfacial structures. Subsequently, these thicker layers enhance the dilational and shear interfacial rheological properties. The interfacial film stabilization and REEs extraction promoted by the cross-linker presented in this work provides an approach to integrate glutaraldehyde as a substitute of common foam stabilizers such as polymers, surfactants, and particles to optimize the recovery of REEs when using biomolecules as extractants.

Trace rare earth elements analysis in atmospheric particulates and cigar smoke by ICP-MS after pretreatment with magnetic polymers.

BACKGROUND: Some heavy metals could be ingested into human body through breathing besides diet and drinking. Atmospheric particulates and smoke are main sources of this kind for the metals' exposure to human. Compared with environmental water, the methodologies for trace metals in particulates and smoke samples with more complex matrix are much less. Magnetic functional sorbents can be designed to remove complex matrix and enrich target analytes. The combination of magnetic solid phase extraction (MSPE) with highly sensitive inductively coupled plasma mass spectrometry (ICP-MS) detection is a good alternative for the analytical purpose. (92). RESULTS: Magnetic polymers were synthesized through free radical polymerization with Fe3O4 nanoparticles as the core and 2-methyl-2-hydroxyethyl 2-acrylate-2-hydroxyethyl ester phosphate as external modifier. The sorbent showed a high phosphorus content (2.7 wt%) and good selectivity to target REEs, along with good reusability (at least 45 times) and chemical stability. With the consumption of 150 mL aqueous solution, an enrichment factor of 300 was obtained by the proposed method, leading to low detection limits (0.001-0.2 ng L-1) for 15 REEs. The application potential of the method was further evaluated by analyzing local atmospheric particulate and cigar smoke samples. Recovery of 86.3-107 % in digested total suspended particulate (TSP) was obtained for 15 REEs, demonstrating a good anti-interference ability of the method. Target REEs in TSP, PM2.5 and PM10 samples were found to be 0.01-2.81, 0.006-1.09 and 0.009-2.46 ng m-3, respectively, and none of them were detected in the collected cigar smoke. (148) SIGNIFICANCE: The method of MSPE-ICP-MS was demonstrated with good potential for trace analysis in complex sample matrix, probably due to the good selectivity of the functionalized polymers. With the design and fabrication of specific functionalized magnetic sorbents, other heavy metals can be monitored in those samples which would be intake by human breathing. It provided an efficient strategy for the evaluation of metals' health risk in particulates and smoke samples. (69).

Interface-Triggered Spin-Magnetic Effect in Rare Earth Intra-particle Heterostructured Nanoalloys for Boosting Hydrogen Evolution.

Rare earth (RE) elements are attractive for spin-magnetic modulation due to their unique 4f electron configuration and strong orbital couplings. Alloying RE with conventional 3d transition-metal (TM) is promising for the fabrication of advanced spin catalysts yet remains much difficulties in preparation, which leads to the mysteries of spin-magnetic effect between RE and 3d TM on catalysis. Here we define a solid-phase synthetic protocol for creating RE-3d TM-noble metal integrated intraparticle heterostructured nanoalloys (IHAs) with distinct Gd and Co interface within the entire Rh framework, denoted as RhCo-RhGd IHAs. They exhibit interface-triggered antiferromagnetic interaction, which can induce electron redistribution and regulate spin polarization. Theoretical calculations further reveal that active sites around the heterointerface with weakened spin polarization optimize the adsorption and dissociation of H2O, thus promoting alkaline hydrogen evolution catalysis. The RhCo-RhGd IHAs show a small overpotential of 11.3 mV at 10 mA cm-2, as well as remarkable long-term stability, far superior to previously reported Rh-based catalysts.

Synthesis of Rare Earth Metal Complexes Stabilized by Amine Bridged Bis(phenolato) Ligands and Their Performance in the Polymerization of rac-ß-Butyrolactone.

A series of rare earth alkoxides bearing amine-bridged bis(phenolato) ligands were synthesized through sequential reactions of RE(C5H5)3(THF) (RE = Y, Lu) or Nd[N(SiMe3)2]3 with bis(phenols) LH2 and CF3CH2OH. Complexes REL(OCH2CF3)(THF)n (1-6) bearing different aryl-substituents were obtained in good yields of 59-70%. They were applied in the ring-opening polymerization (ROP) of rac-ß-butyrolactone (rac-BBL), which showed good activity (TOF up to 27,300 h-1), resulting in syndiotactically enriched poly(3-hydroxybutyrate) (PHB) (Pr up to 0.86) with narrow polydispersities (PDI ≤ 1.27). The yttrium complex 3 bearing bulky o-1,1-diphenylethyl substituents outperformed other complexes, suggesting that the smaller ionic radii of metal centers and bulky ortho substituents of ancillary ligands play crucial roles in controlling the activity and stereoselectivity in ROP of rac-BBL. Kinetics of the polymerization of rac-BBL initiated by complex 3 was investigated, which revealed first order dependences on the monomer and initiator concentrations, respectively.

Mobility and fractionation of rare earth elements during black shale weathering: Implications from acid rock drainage and sequential extraction study.

Black shale is a type of sedimentary rocks that are enriched in rare earth elements (REEs). It is of both economic importance and environmental significance to understand REE mobility during black shale weathering. The present study approaches to this by analysing REEs in acid rock drainage (ARD) from black shale weathering system, fresh and weathered black shales, soils derived from black shales, and sequential extractants from black shales at Dongping town in Hunan province (China). Results showed that REEs had variable high concentrations in ARD as shown by total REE + Y (∑REY) concentrations from 162 to 4074 (µg/L). REEs in ARD displayed hat-shape NASC-normalized patterns with significant enrichments of middle REEs (MREE) relative to light REEs (LREE) and heavy REEs (HREE), and had significant negative Ce (Ce/Ce⁎ = 0.6) and positive Y (Y/Y⁎ = 1.5) anomalies. MREE enrichment in ARD could be evaluated using MREE/MREE⁎ values, which varied from 1.43 to 1.81 with a mean of 1.65, distinctly higher than those of whole rocks (around 1.0). 1 M HCl extraction results suggested that REEs were integratedly mobilized during shale weathering, while six-step extraction studies identified that REEs in ARD resulted from exchangeable and Fe-oxide fractions with MREE and HREE enrichment in shales respectively. MREE in exchangeable and HREE in Fe-oxide fractions were preferentially released during weathering, as illustrated by plots of MREE/MREE⁎ against HREE/LREE ratios of ARD and six-step extractants. Therefore, geochemical processes for REE mobility during black shale weathering included integrated mobilization and preferential release. Integrated REE mobilization resulted from the dissolution of REE-bearing minerals and oxidation of sulfides. Preferential REE release resulted from acid fluids produced by sulfide oxidation during weathering. Thus, a new model was proposed for interpreting geochemical processes of REE mobility during black shale weathering, and for understanding REE distribution in ARD from natural and anthropogenic systems.