Synthesis of highly deficient nano SrCoOx for the purification of lanthanides from monazite concentrate

Redistribution and chemical speciation of rare earth elements in an ion-adsorption rare earth tailing, Southern China

Mining is an activity that will change the distribution and chemical speciation of rare earth elements (REEs), thus posing a serious threat to the natural environment. However, the distribution and chemical speciation of REEs in ion-adsorption rare earth tailings remain poorly understood. In this study, we investigated the contents and forms of REEs and associated geochemical behavior in rare earth tailings in southeast China. Total rare earth elements (TREEs) contents were lower while the ratios of light REEs (LREEs) to heavy REEs (HREEs) were higher in tailings than in an unmined area. In the unmined area, the distribution characteristics of TREEs and LREEs remained consistent, whereas HREEs differed with increasing depth. However, in the tailing area, the distribution characteristics of TREEs, LREEs and HREEs tended to be consistent, reflecting the outcomes of mining activities on vertical distribution characteristics of REEs. The REEs were dominated by residual and exchangeable forms in the unmined area, while residual and exchangeable REEs accounted for 80% and 20% of the TREEs, respectively, in the three tailings. Additionally, the exchangeable and carbonate-bound REEs increased but Fe/Mn oxide-bound and organic-bound REEs declined in the unmined area, whereas their distribution characteristics were irregular in the tailings. These results suggest that mining activity could curtail REEs contents and redistribute their chemical speciation, further altering geochemical behaviors in the tailings and posing serious risks to adjacent environments.

Sorption behavior of natural uranium from aqueous solutions using modified activated carbon with quinoline

The activated carbon (AC) was modified by molecules of quinoline (Q) and the new prepared AC impregnated by Q was characterized using Fourier transform infrared (FTIR), Raman spectroscopy, surface measurements, scanning electron microscope (SEM) and transmission electron microscope (TEM). These analytical techniques demonstrated a successful preparation of AC-Q as a new material which was examined for its sorption behavior for natural uranium. The sorption results by batch mode indicated the optimum conditions for 94.5% removal of U(VI) ions at pH 4.7 and an equilibrium contact time of 90 min. The analysis of sorption data revealed that the pseudo-second-order and Langmuir were more fitted than other estimated models. The sorption capacity of U(VI) was ∼63 mg/g onto AC-Q as adsorbent martial. The thermodynamic data demonstrated that the sorption of uranium is endothermic and spontaneous. New mechanism was supposed based on the role of the abrasive material quinoline on the mechanical removal of uranium from aqueous solution.

Sponge-like Ca-alginate/Lix-84 beads for selective separation of Mo(VI) from some rare earth elements

In this investigation, a novel alginate complex was developed for the selective separation of molybdenum (Mo(VI)) ions from some rare earth elements (REEs). In this regard, alginate as a natural polysaccharide was impregnated and modified with 2-hydroxy-5-nonylacetophenone oxime (Lix-84) and characterized using FT-IR, TGA/DTA and SEM-EDX. The relation between medium acidity, adsorption kinetics, sorbent dose, isotherm models, temperature and Mo(VI) recovery was investigated. It was concluded that the impregnation stage promoted the Mo(VI) separation. The kinetics and isotherm data were well-fitted and matched with the pseudo-first-order model and Langmuir isotherm model; respectively. The Langmuir maximum adsorption capacity of Mo(VI) reached 72.2 mg/g. The developed material showed excellent separation performance towards Mo ions over the investigated REEs. The desorption and recovery of the loaded Mo(VI) ions were achieved using 1.0 M HCl. Reutilization of Alg/Lix-84 was confirmed up to three adsorption-desorption cycles with no damage of the beads as proved with SEM analysis. The adsorption mechanism of molybdenum onto Alg/Lix-84 was elucidated through FTIR and XPS measurements and was found to be governed by both electrostatic interaction and ion exchange. Therefore, the developed material has a promising potential for the selective separation of molybdenum from REEs-containing solution.

Novel nano network trigonal prismatic Ba2CoO4-deficient BaCoO3 for high-affinity sorption of radiolanthanide elements of biomedical applications: synthesis and sorption studies

Nano trigonal prismatic Ba₂CoO₄ with hierarchical structure and deficient BaCoO₃ with columnar structure have been prepared at low temperatures (400 [BC4] and 500 [BC5]) °C/3h using green method. X-ray diffraction (XRD) results demonstrate the presence of enriched Ba₂CoO₄ phase at 400 °C and multiphase structures: BaCoO₃, BaCoO_3-δ, and Co₃O₄ with a decrease in the amount of Ba₂CoO₄ at 500 °C. The prepared powders are characterized by a high specific surface area (SSA) values which are reflected to the mode of synthesis that leads to produce materials with massive active sites. The SSA of BC4 is higher than that of BC5 which can be correlated to the difference in the microstructure analysis of BC4 and BC5 as given from scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) studies. Electron spin resonance (ESR) spectroscopy as an effective method for the characterization of vacancy-rich nanostructures indicates that the presence of oxygen vacancies is related mainly to BaCoO₃, BaCoO_3-δ, and Co₃O₄ phases while the effective oxygen vacancies is in BaCoO₃ and BaCoO_3-δ. The nanocrystalline structures of BC4 and BC5 as novel nano-adsorbents are the first time to be tested. Production of Gd radioisotopes through ^natGd(n,γ)^153,159,161Gd and carrier-free ¹⁶¹Tb through ¹⁶⁰Gd(n,γ,) ¹⁶¹Gd [Formula: see text] ¹⁶¹Tb are achieved at 2nd Egyptian nuclear research reactor (ETRR-2). Preliminary sorption study of Gd radioisotopes (represent the lanthanide elements) shows a promising material for the application in the separation and removal of lanthanide elements. The results demonstrated that the fast interaction and efficient sorption of lanthanides ions are based on the novel synthesized nanomaterial that can be considered for the upscale application in this field.