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Resources and Sustainable Materials
Published in Stanley E. Manahan, Environmental Chemistry, 2022
In recent years, numerous uses have emerged for the rare earth elements metals consisting of the 15 lanthanides (elements with atomic numbers 58 through 71 in the periodic table) plus scandium and yttrium, transition elements with atomic numbers 21 and 39, respectively. The chemical properties of the lanthanides are generally quite similar to each other, making their separation difficult. The chemical properties of scandium and yttrium are similar to those of the lanthanides; hence, they are commonly classified as rare earths.
Borate Phosphor
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
Luminescent materials with lanthanides are found in fluorescent tubes, colour televisions, X-ray photography, lasers, infrared (IR) to visible light up conversion materials and fibre amplifiers [108–110]. Such applications depend on the luminescence properties of lanthanide ions (sharp lines and high efficiency). In fluorescent lamps, phosphors on the inside wall of the glass tube convert the ultraviolet (UV) radiation (mainly with a wavelength l of 254 nm) that is generated in the Hg discharge to blue, green and red light, yielding white light. The quantum efficiency of the lanthanide-based lamp phosphors is high (90%) (1): For every 100 UV photons that are absorbed, 90 photons in the visible spectral region are emitted.
Nanoprobes for Early Diagnosis of Cancer
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Given their high atomic numbers, lanthanide-based contrast agents as CT probes have also been explored. Free lanthanide ions are extremely toxic. So most lanthanide-based contrast agents are used in the form of chelate complexes. Many nanoparticle lanthanide CT agents are designed as multimodal imaging media. As an example, nanoprobes containing a rare-earth core (consisting of a mixture of lanthanides such as Gd, Yb, Er, Tm, and Yttrium) and conjugated with additional X-ray attenuating lanthanide materials were explored as multi-modal (CT/MRI/upconversion fluorescence) nanoparticu-late contrast media.73
Preparation, structure, and properties of a novel chain-like terbium–mercury complex
Published in Inorganic and Nano-Metal Chemistry, 2020
Lanthanide compounds have received more and more attention in recent years, because lanthanide compounds have many applications in different areas, such as fluorescent probes, electroluminescent devices, magnetic materials, sensors, catalysts, cell imaging, and so forth.[1,2] Up to date, a large number of lanthanide compounds have been explored about their structures and physical and chemical properties.[3,4] The physical and chemical behavior of lanthanide compounds closely relates to the 4f electrons of the lanthanide ions. For instance, lanthanide compounds can usually show photoluminescence if an effective transition of the 4f electrons between the orbitals can happen. However, due to low absorption coefficient of the lanthanide ions, an effective interorbital transition of the 4f electrons is hard to occur, which makes a lanthanide compound unable to show ideal photoluminescence. As a result, in order to improve the absorption coefficient and promote the transition of 4f electrons between the orbitals, a lot of scientists applies a so-called “antenna effect” strategy,[5,6] namely, using an organic molecule with a conjugating structure as a ligand. Heterocyclic molecules and aromatic carboxylic acids are such ligands and they can coordinate with lanthanide ions to obtained novel compounds. The “antenna effect” refers to the use of the conjugated structure of these organic molecules to absorb the excited light energy and transfer the energy to lanthanide ions, causing the lanthanide ions to exhibit photoluminescence.
Rare-earth metal based adsorbents for effective removal of arsenic from water: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2018
Yang Yu, Ling Yu, Kok Yuen Koh, Chenghong Wang, J. Paul Chen
The lanthanides, as a series of elements with atomic numbers of 57 to 71, are generally classified into two categories based on the electron configuration: (1) the light rare earth elements (LREEs), also termed as the cerium group, i.e., lanthanum to gadolinium (atomic numbers ranging from 57 to 64), and (2) the heavy rare earth elements (HREEs), e.g., terbium to lutetium (atomic numbers ranging from 65 to 71) (Gschneider, 1966).
Modeling the Extraction Rate Coefficient for the Extraction of Yttrium by DEHPA Using Organic-Phase Recycle
Published in Solvent Extraction and Ion Exchange, 2019
Dave DeSimone, Natasha Ghezawi, Thomas Gaetjens, Robert Counce, Jack Watson
Solvent extraction via mixer-settlers has been industrially effective in extracting lanthanides from leach solutions for many years.[1] Recently, many of these lanthanides (referred to as rare earth elements or REE’s) have been classified by the U.S. Department of Energy as critical materials for their technological importance, economic value, and potential supply limitations.[2] Because of this, there has been interest in improving solvent extraction techniques. One proposed method of improvement, recycling at least one of the exiting streams, has been shown to increase efficiency[3–5], reduce emulsions[6], and reduce entrainment[5,6] when employed correctly. It has been realized that, among other conditions, recycle is advantageous when there is insufficient turbulence in the mixer[7] and when the recycled phase is the phase favored by the REE at equilibrium.[3] This latter case indicates that recycle works best in systems with high distribution coefficients. As previous authors have suggested, when recycle is employed properly, the exiting extract is more concentrated compared to nonrecycled processes. This yields an equivalent efficiency at a lower solvent flow rate[4] and potentially provides for the operability of very low organic-to-aqueous flow rate ratios. The increased extraction rate observed when recycle is employed has been attributed to the increased dispersed-phase holdup and the increased interfacial area[4,8,9] that results. Although recycle models relating the mixer-settler extraction performance to the holdup have been proposed[10], they do not account for changes in the extractant concentration in tandem with changes in the fraction recycled. The purpose of this study was to determine the efficiency and model the extraction rate coefficient for solvent extraction processes that employ recycle over a range of extractant concentrations. Table 1 depicts the nomenclature with units for all symbols employed herein.