Interaction Of Rare Earth Elements Research Articles

Complex interactions of rare earth elements in aquatic systems: Comparing observed and predicted cellular responses on Mytilus galloprovincialis

Recent societal and technological developments have led to new sources of contamination, particularly from electronic waste (e-waste). The rapid increase in e-waste, combined with inadequate disposal and recycling practices has resulted in rising levels of hazardous substances in aquatic systems, including rare-earth elements (REEs). However, the effects of REEs on aquatic organisms remain poorly understood. This lack of understanding is concerning since REEs can simultaneously appear in aquatic systems. Thus, this study aimed to evaluate the impacts of Y, La, and Gd, individually and as mixtures on the mussel species Mytilus galloprovincialis. Biomarkers related to metabolism, energy reserves, defence enzymes, redox balance, cellular damage and neurotoxicity were analyzed. The results obtained showed that yttrium alone caused minimal stress, while gadolinium, lanthanum, and their mixtures induced moderate to severe stress, increased metabolic activity, and enzyme responses. This study highlights the ecological impacts of rare earth element (REE) mixtures on aquatic organisms. The complex interactions and additive effects, especially with gadolinium, underline the need for further research on contaminant mixtures.

Investigating the Influence of Impurity Defects on the Adsorption Behavior of Hydrated Sc3+ on the Kaolinite (001) Surface Using Density Functional Theory.

In natural kaolinite lattices, Al3+ can potentially be substituted by cations such as Mg2+, Ca2+, and Fe3+, thereby influencing its adsorption characteristics towards rare earth elements like Sc3+. Density functional theory (DFT) has emerged as a crucial tool in the study of adsorption phenomena, particularly for understanding the complex interactions of rare earth elements with clay minerals. This study employed DFT to investigate the impact of these three dopant elements on the adsorption of hydrated Sc3+ on the kaolinite (001) Al-OH surface. We discerned that the optimal adsorption configuration for hydrated Sc3+ is Sc(H2O)83+, with a preference for adsorption at the deprotonated Ou sites. Among the dopants, Mg doping exhibited superior stability with a binding energy of -4.311 eV and the most negative adsorption energy of -1104.16 kJ/mol. Both Mg and Ca doping enhanced the covalency of the Al-O bond, leading to a subtle shift in the overall density of states towards higher energies, thereby augmenting the reactivity of the O atoms. In contrast, Fe doping caused a pronounced shift in the density of states towards lower energies. Compared to the undoped kaolinite, Mg and Ca doping further diminished the adsorption energy of hydrated Sc3+ and increased its coordination number, while Fe doping elevated the adsorption energy. This study offers profound insights into understanding the role of dopant elements in the adsorption of hydrated Sc3+ on kaolinite.

AI assisted steel cleanness evaluation: Predicting the morphology of La-traced non-metallic inclusions using backscattered-electron images

This study shows how computer vision, a field of artificial intelligence (AI), can be used to gain access to morphological information for a better process understanding and furthermore, how it can be implemented in the evaluation of active tracing experiments. Non-metallic inclusions (NMIs) play a crucial role in determining the chemical and physical properties of the final steel product. The active tracing technique allows for tracking the formation and modification mechanisms of detrimental NMIs throughout the steelmaking process by adding rare earth elements (REEs) to the melt. The interaction of REEs with NMIs results in the formation of traced multiphase particles and, therefore, lead to challenges for accurate evaluation by automated scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). However, obtaining information about the REE distribution in traced NMIs without extensive, time-consuming human effort is not feasible using the existing method. A two-step classification process with AI was established, which included training and testing of two random forest classifiers (RFC). The first RFC achieved for the binary NMI/non-NMI classification an accuracy of 94.8 %. Four different morphology-based classes were considered in the second classification, whereas traced homogeneous NMIs and NMIs with a high La content got classified with a precision exceeding 90 %. However, caution is required in interpreting results for traced heterogeneous NMIs, as they have a higher prediction error of 37.2 %.

Dynamic interaction processes of rare earth metal mixtures in terrestrial organisms interpreted by toxicokinetic and toxicodynamic model

Despite the progress in explanation of mixture toxicity of rare earth elements (REEs), a large knowledge gap still exists in interpreting their mixed effects from a dynamic perspective. Here, we investigated the effects of La-Ce mixtures in Enchytraeus crypticus at different exposure times. The single and mixture toxicity of La and Ce increased with time, as reflected by the reduced LC50/MT50 values. With concentration addition as the reference model, the interactions between La and Ce were quantified by MIXTOX modelling tool, showing a time-dependent pattern with antagonistic effect after 1 and 2 d but additive effects afterwards. The dynamic accumulation and toxicity of La/Ce in organisms exposed to REE mixtures was fitted using a process-based toxicokinetic and toxicodynamic (TK-TD) model to unravel how the elements interacted. Generally, the estimated uptake, elimination, and damage rate constants of La/Ce declined with increasing level of each other, suggesting inhibited uptake and subsequently reduced toxicity of La/Ce due to competition effect. The interplay of La and Ce in TK and TD processes seemed responsible for the observed antagonism. Our study showed that mixture toxicity and interaction of REEs are time-dependent processes and application of TK-TD model may provide more insight into this dynamic effect.

Effects of Different Concentrations of Lanthanum on the Growth and Uptake of Pb by Maize Grown Under Moderate Lead Stress

A greenhouse pot experiment was conducted to investigate the effects of different concentrations of lanthanum (0 mg·kg-1, 50 mg·kg-1, 200 mg·kg-1 and 800 mg·kg-1) on growth, nutrient uptake, C:N:P stoichiometry, and La and Pb uptake by maize (Zea mays L.) under moderate lead stress (200 mg·kg-1) and evaluate the interaction of rare earth elements and heavy metals in the soil-plant system. The aim was to provide basic data and a theoretical basis for the remediation of rare earth element and heavy metal-co-contaminated soils in a rare earths mining area. The results indicate that the concentrations of CH3COONH4-EDTA-extractable La and Pb significantly increase and decrease, respectively, with increasing La concentrations of the soils. The shoot dry weights of maize significantly decreases by 17.90% to 81.17% and the root to shoot ratio of maize significantly increases by 21.74% to 86.96% with increasing La concentrations of the soils. With increasing La concentrations in soils, the root P contents of maize significantly decrease by 19.16% to 89.68%. The shoot P and N contents significantly decrease by 65.51% to 91.98% and 48.27% to 76.58%, respectively, when the exogenous application of La is 200 mg·kg-1 and 800 mg·kg-1, respectively. The increasing La concentrations in soils significantly increase the C:P and N:P ratios and shoot and root La concentrations of maize. The shoot and root Pb concentrations of maize significantly increase by 52.61% to 99.01% and 15.99% to 44.34%, respectively, with increasing La concentrations. Overall, the increasing La concentrations in soils significantly decrease the K, Ca, and Mg contents of maize. The results demonstrate that the presence of rare earth elements aggravates the phytotoxicity of heavy metals to plant and ecological risks. Further research should focus on the effects and mechanisms of rare earth elements on the heavy metal uptake by plants.

Phytotoxicity of individual and binary mixtures of rare earth elements (Y, La, and Ce) in relation to bioavailability

Rare earth elements (REEs) are typically present as mixtures in the environment, but a quantitative understanding of mixture toxicity and interactions of REEs is still lacking. Here, we examined the toxicity to wheat (Triticum aestivum L.) of Y, La, and Ce when applied individually and in combination. Both concentration addition (CA) and independent action (IA) reference models were used for mixture toxicity analysis because the toxicity mechanisms of REEs remain obscure. Upon single exposure, the EC50s of Y, La, and Ce, expressed as dissolved concentrations, were 1.73 ± 0.24 μM, 2.59 ± 0.23 μM, and 1.50 ± 0.22 μM, respectively. The toxicity measured with relative root elongation followed La < Y ≈ Ce, irrespective of the dose descriptors. The use of CA and IA provided similar estimates of REE mixture interactions and toxicity. When expressed as dissolved metal concentrations, nearly additive effects were observed in Y-La and La-Ce mixtures, while antagonistic interactions were seen in Y-Ce mixtures. When expressed as free metal activities, antagonistic interactions were found for all three binary mixtures. This can be explained by a competitive effect of REEs ions for binding to the active sites of plant roots. The application of a more elaborate MIXTOX model in conjunction with the free ion activities, which incorporates the non-additive interactions and bioavailability-modifying factors, well predicted the mixture toxicity (with >92% of toxicity variations explained). Our results highlighted the importance of considering mixture interactions and subsequent bioavailability in assessing the joint toxicity of REEs.

Atomic-level insights into the adsorption of rare earth Y(OH)3-nn+ (n = 1–3) ions on kaolinite surface

The interaction of rare earth elements (REEs) ions with clay minerals is crucial for understanding the processing of mineralization, extraction and recovery of ion-adsorption rare earth. Theoretical studies based on density functional theory (DFT) were performed to investigate the adsorption of rare earth Y(OH)3-nn+ (n = 1–3) ions on kaolinite surfaces of varying deprotonation degree depending on the solution pH. The Conductor-like Screening Model (COSMO) was used to simulate the water environment of adsorption. The calculated results showed that the surface electrostatic potential and frontier orbital are enhanced and increasingly localized around the exposed oxygen atoms with the increase of the deprotonation degree of kaolinite (0 0 1) surface hydroxyls. Y(OH)3-nn+ ions are adsorbed mainly via the Y atom and the surface O atoms, and located over the center of Al-hexagonal ring on kaolinite (0 0 1) surface, and the center of Si-hexagonal ring on kaolinite (0 0 −1) surface. The adsorption energies increase with the increase of deprotonation degree of kaolinite (0 0 1) surface, and decrease with the increase of the hydrolysis degree of Y3+. The results of Mulliken bond length and population, atomic charge, electron density and density of states (DOS) revealed that Y(OH)3-nn+ ions interact with kaolinite (0 0 1) surface through the combination of covalent and electrostatic bonding, while with (0 0 −1) surface mainly through electrostatic bonding. The above calculated results would provide some atomic-level insights for the interaction of rare earth ions with kaolintie surfaces in aqueous solution.

Characterization of the interaction of rare earth elements with P507 in a microfluidic extraction system using spectroscopic analysis

An attempt to characterize the interaction of rare earth elements with P507 in a microfluidic extraction system containing lactic acid as complexing agent is made using spectroscopic (FT-IR, UV–Vis, NMR and MS) analysis. The role of lactic acid in the extraction process is analyzed. The extraction mechanism confirmed that lactic acid does not involve in the extraction reaction. A comparative analysis of the composition of the extracts using FT-IR, UV–Vis, NMR and MS methods, indicates that the extracted complexes of rare earth ions located in the center is formed by the cation exchange process between POH and RE3+, and coordination process between PO and RE3+.

Effects of arbuscular mycorrhizal symbiosis on growth, nutrient and metal uptake by maize seedlings (Zea mays L.) grown in soils spiked with Lanthanum and Cadmium

Multiple contaminants can affect plant-microbial remediation processes because of their interactive effects on environmental behaviour, bioavailability and plant growth. Recent studies have suggested that arbuscular mycorrhizal fungi (AMF) can facilitate the revegetation of soils co-contaminated with rare earth elements (REEs) and heavy metals. However, little is known regarding the role of AMF in the interaction of REEs and heavy metals. A pot experiment was conducted to evaluate the effects of Claroideoglomus etunicatum on the biomass, nutrient uptake, metal uptake and translocation of maize grown in soils spiked with Lanthanum (La) and Cadmium (Cd). The results indicated that individual and combined applications of La (100 mg kg−1) and Cd (5 mg kg−1) significantly decreased root colonization rates by 22.0%–35.0%. With AMF inoculation, dual-metal treatment significantly increased maize biomass by 26.2% compared to single-metal treatment. Dual-metal treatment significantly increased N, P and K uptake by 20.1%–76.8% compared to single-metal treatment. Dual-metal treatment significantly decreased shoot La concentration by 52.9% compared to single La treatment, whereas AM symbiosis caused a greater decrease of 87.8%. Dual-metal treatment significantly increased shoot and root Cd concentrations by 65.5% and 58.7% compared to single Cd treatment and the La translocation rate by 142.0% compared to single La treatment, whereas no difference was observed between their corresponding treatments with AMF inoculation. Furthermore, AMF had differential effects on the interaction of La and Cd on metal uptake and translocation under the background concentrations of soil metals. Taken together, these results indicated that AMF significantly affected the interaction between La and Cd, depending on metal types and concentrations in soils. These findings promote a further understanding of the contributions of AMF to the phytoremediation of co-contaminated soil.

Interaction of rare earth elements and components of the Horonobe deep groundwater

To better understand the migration behavior of minor actinides in deep groundwater, the interactions between doped rare earth elements (REEs) and components of Horonobe deep groundwater were investigated. Approximately 10 ppb of the REEs, i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb were doped into a groundwater sample collected from a packed section in a borehole drilled at 140 m depth in the experiment drift of Horonobe Underground Research Laboratory in Hokkaido, Japan. The groundwater sample was sequentially filtered with a 0.2 μm pore filter, and 10 kDa, 3 kDa and 1 kDa nominal molecular weight limit (NMWL) ultrafilters with conditions kept inert. Next, the filtrate solutions were analyzed with inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of the REEs retained in solution at each filtration step, while the used filters were analyzed through neutron activation analysis (NAA) and TOF-SIMS element mapping to determine the amounts and chemical species of the trapped fractions of REEs on each filter. A strong relationship between the ratios of REEs retained in the filtrate solutions and the ionic radii of the associated REEs was observed; i.e. smaller REEs occur in larger proportions dissolved in the solution phase under the conditions of the Horonobe groundwater. The NAA and TOF-SIMS analyses revealed that portions of the REEs were trapped by the 0.2 μm pore filter as REE phosphates, which correspond to the species predicted to be predominant by chemical equilibrium calculations for the conditions of the Horonobe groundwater. Additionally, small portions of colloidal REEs were trapped by the 10 kDa and 3 kDa NMWL ultrafilters. These results suggest that phosphate anions play an important role in the chemical behavior of REEs in saline (seawater-based) groundwater, which may be useful for predicting the migration behavior of trivalent actinides released from radioactive waste repositories in the far future.

Interaction of rare earth elements with a brown marine alga in multi-component solutions

The present study elucidates the underlying mechanisms involved in the interaction of lanthanides (lanthanum, cerium, europium and ytterbium) with a brown marine alga, Turbinaria conoides in quaternary mixtures. Competition between the lanthanides in occupying the binding sites of T. conoides was clearly identified, which was due to competitive ion-exchange mechanism. This competition affected the affinity of T. conoides towards each lanthanide. In comparison to single-component lanthanide system, uptake capacities in quaternary systems decreased by 75.8, 72.5, 65.0 and 70.2% for La, Ce, Eu and Yb, respectively. Biosorption mechanism was confirmed through SEM/EDX and pH-edge data, which implies that when virgin T. conoides are exposed to lanthanide solutions, La 3+ cations may replace some of the alkali and alkaline earth metals naturally present in the cell wall through ion-exchange mechanism; and this phenomenon was favored at pH 5, under examined conditions. Quaternary biosorption isotherms were successfully modeled using the extended Langmuir model with a constant interaction factor. The model predictions agreed well with the experimental data. The magnitude of Eu competition over lanthanides was significant, yielding a lowest interaction factor ( η = 0.91) for Eu over other lanthanides. Biosorption kinetics revealed that more than 91% of sorption process was completed within 60 min for all lanthanides, followed by slow attainment of equilibrium in around 3 h. Desorption was successful with 0.05 M HCl and the algal biomass was reused for three cycles without significant loss in original lanthanide uptake capacity.

Interactions of rare earth elements with bacteria and organic ligands

We investigated the interactions of rare earth elements (REEs) Eu(III) and/or Ce(III, IV) with the common soil bacterium Pseudomonas fluorescens and organic ligands, such as malic acid, citric acid, a siderophore (DFO), cellulose, chitin, and chitosan. Malic acid formed complexes with Eu(III), but degradation of malic acid was observed when the ratio of malic acid to Eu(III) was higher than 100. Citric acid formed a stoichiometric complex with Eu(III) that was not degraded by P. fluorescens. Adsorption of Eu(III) from the DFO complex occurred as a free ion dissociated from DFO and not as the Eu(III)–DFO complex. Cerium(III) was oxidized to Ce(IV) during complexation with DFO to form the Ce(IV)–DFO complex. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) analysis showed that cellulose, chitin, and chitosan, respectively, formed a weak complex, an inner-spherical complex, and an outer-spherical complex with Eu(III). This method also demonstrated that the coordination environment of Eu(III) adsorbed on P. fluorescens possessed similar characteristics to that of chitin, and revealed that adsorption of Eu(III) on P. fluorescens was through a multidentate and predominantly inner-spherical coordination.

Isothermal Section of the Ce—Mn—Ge Ternary System at 670 K.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Isothermal section of the Ce–Mn–Ge ternary system at 670 K

The isothermal section of the phase diagram of the Ce–Mn–Ge ternary system was constructed at 670 K. Four ternary intermetallic compounds were found to exist. A critical assessment on the interaction of rare-earth elements (La–Lu) with manganese and germanium was made.

Extended X-ray absorption fine-structure study of the bound form of lanthane in chlorophyll-a from Dicranopteris dichotoma.

The in vivo coordination structure of lanthanum ions interacting with chlorophyll-a of the fern Dicranopteris dichotoma grown in a rare earth minefield in southern China was determined by the extended x-ray absorption fine structure (EXAFS). The results show that lanthanum includes two porphyrin rings in its coordination sphere. It is postulated that the La-chlorophyll-a complex may have a bilayer structure. The analytical method may serve as a new tool to gain insight in the in vivo interactions of rare earth elements.

Ternary Ce–Co–Ge system

Isothermal sections of the phase diagrams of the ternary system Ce–Co–Ge at 870 K (0–50 at.% Ce) and 670 K (50–100 at.% Ce) have been constructed. Eleven ternary compounds have been found to exist. A critical characterization of the interaction of rare earth elements (La–Gd) with cobalt and germanium has been made.

CeNiGe and NdNiGe phase diagrams: systematics of rare earth-nickel-germanium compounds

The ternary systems Ce(Nd)NiGe have been investigated and phase relations have been determined at 870 K, where respectively 20 and nine compounds were observed. A critical assessment on the interaction of rare earth elements with nickel and germanium has been made.

CeFeGe, NdFeGe and HoFeGe phase diagrams: systematics of rare earth-iron-germanium compounds

The ternary systems Ce(Nd,Ho)FeGe have been investigated and phase relations have been determined at 870 K, where respectively seven, eight and six compounds were observed. A critical assessment on the interaction of rare earth elements with iron and germanium has been made.

A method to investigate the interaction of rare earth elements in aqueous solution with metal oxides

A method is described which can be used to investigate the interaction of dissolved metals with particulate material. Low level concentrations (10−9M) of rare earth radiotracers were used to investigate their sorption onto synthetic mineral oxide surfaces. The preparation of rare earth radiotracers by neutron activation is discussed in detail. A kinetic approach was employed to investigate the interaction of dissolved metals and suspended mineral oxides. Amorphous iron oxyhyroxide, a phase commonly found in nature, was used in sorption experiments carried out in seawater at pH 7.8 and 2°C. Results of this study indicate a high affinity of the rare earth elements (REE) for the iron oxide surface (evidenced by fast uptake and high partition coefficients) and reveal a fraction between light and heavy REE.