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Photoluminescence Investigations of UV, Near UV, and Visible Light Excited CaS:Eu Nanophosphors
Published in V. R. Remya, H. Akhina, Oluwatobi Samuel Oluwafemi, Nandakumar Kalarikkal, Sabu Thomas, Nanostructured Smart Materials, 2022
Rare-earth ions, also known as lanthanides, comprise an interesting group of elements including Europium, Cerium, Terbium, and Samarium, whose optical properties are determined by the inner ‘f’ electrons. Europium is an important rare earth element whose optical properties are derived from the incompletely filled 4f shell electrons. These electrons are shielded by the 5s and 5p closed shells, and hence they do not participate directly in bonding and interact much less strongly with the environment. Europium ions have been explored due to their PL properties, which result in the emission of sharp atomic bands corresponding to f → f transitions in the central metal ion. Eu3+or Eu2+ ion incorporation into the host lattice can be identified from the characteristic PL they exhibit. Eu2+ emission arises from the lowest band of 4f65d1 configuration to 8S state of 4f7 configuration. Eu3+ 7/2 ions give unique narrow emission and absorption band, which arises due to the 5D0 → 7FJ (J = 0, 1, 2, 3,…) electronic transitions of Eu3+ ions.
Melting in the Moon
Published in Gilbert Fielder, Secrets of the Moon, 2021
Most of the rock samples that the Apollo 16 astronauts returned from the Cayley/Descartes region of the highlands were composed, largely, of the rock-forming mineral plagioclase which forms white, lath-shaped crystals, common in basic igneous rocks. Analyses of the lunar plagioclases show that they are enriched in the rare earth element europium. Following extensive early melting, plagioclase must have floated up from the mantle and cooled to form the Moon’s crust, enriched in europium.26 Other laboratory dating and analysis, this time of returned mare lavas, showed that they erupted later, between 3 × 109 and 4 × 109 years ago, probably as a result of partial melting of pockets of rock in the mantle. These basalts are depleted in europium, indicating that the plagioclase had acquired the europium from the parent magmas.
Heavy Metals
Published in Abhik Gupta, Heavy Metal and Metalloid Contamination of Surface and Underground Water, 2020
Evaluating all these arguments and counter-arguments over whether to continue use of the term “heavy metal” or to abandon it, this book adopts the criteria presented by Ali and Khan (2018), which are found to be scientifically consistent, precise, and logical, and follows these to enlist the metals fulfilling these conditions as “heavy metals.” Table 1.4 presents the list of “heavy metals” according to this classification along with their atomic numbers and densities. The atomic numbers range from 23 (vanadium) to 94 (plutonium) with the other heavy metals coming in between. However, only those elements are categorized as heavy metals which satisfy the three criteria laid down by Ali and Khan (2018). For example, though scandium, titanium, and yttrium are naturally occurring metals having atomic numbers of 21, 22, and 39, and thereby fulfill criteria (i) and (ii) of being metals having an atomic number greater than 20, these are excluded from the heavy metal category because their densities are less than 5 g cm–3 (scandium 2.99, titanium 4.54, and yttrium 4.47 g cm–3) and therefore fail to satisfy criterion (iii). On the other hand, technetium (atomic number 43, density 11.50 g cm–3) and promethium (atomic number 61; density 7.30 g cm–3) are not considered because they do not occur naturally and, therefore, do not meet criterion (i). The densities of the 51 elements categorized as heavy metals range from 5.24 g cm–3 (europium) to 22.6 g cm–3 (osmium).
Recent advances on hydrometallurgical recovery of critical and precious elements from end of life electronic wastes - a review
Published in Critical Reviews in Environmental Science and Technology, 2019
Manivannan Sethurajan, Eric D. van Hullebusch, Danilo Fontana, Ata Akcil, Haci Deveci, Bojan Batinic, João P. Leal, Teresa A. Gasche, Mehmet Ali Kucuker, Kerstin Kuchta, Isabel F. F. Neto, Helena M. V. M. Soares, Andrzej Chmielarz
While there is a gradual depletion of primary ores of these critical and precious elements, they are found in relatively high concentrations in electronic wastes. Waste printed circuit boards (PCBs), waste liquid crystal displays (LCDs), spent cathode ray tubes (CRTs), spent fluorescent lamps, waste hard disk drives (HDDs), spent light emitting diodes (LEDs) and spent batteries are the fastest growing WEEE and contain many critical and precious elements (Willner & Fornalczyk, 2013; Askari, Ghadimzadeh, Gomes, & Ishak, 2014; Natarajan, Tay, Yew, & Ting, 2015). For instance, Indium-tin oxide (ITO) forms the basis of LCDs and rise crucial demand for indium (In). European Commission (2014) reported that the total world consumption of yttrium is estimated 7,650 Mg and the main uses of yttrium are 79% and 21% for phosphors and ceramics, respectively. The yttrium demand has been increasing by around 8% per year and its supply is also expected to increase at a similar rate (European Commission, 2014). On the other hand, europium is a fundamental element for phosphors production, almost 96% of the global Eu consumption (425 Mg) is used for phosphors production (European Commission, 2014). Similarly, precious metals such as Au are essential to fabricate PCBs and chip-on-board LEDs. Significant concentration of gold (2 g·kg−1) is present in the spent chip-on-board LEDs (Murakami, Nishihama, & Yoshizuka, 2015). WEEEs are highly heterogeneous and practically it is not possible to have a generic recycling technologies.
Resonance analysis of 151,153Eu from neutron capture cross section measurements in the energy range from 1 to 20 eV
Published in Journal of Nuclear Science and Technology, 2018
Jaehong Lee, Jun-ichi Hori, Tadafumi Sano, Ken Nakajima
Europium has two stable isotopes, 151Eu and 153Eu. Since the effect of isotope impurity in the 153Eu enriched-sample on the capture yield is considerable, the accurate neutron capture cross sections of 151Eu are also necessary.
Sorption behavior of Eu(III) from an aqueous solution onto modified hydroxyapatite: kinetics, modeling and thermodynamics
Published in Environmental Technology, 2018
From aqueous solutions containing calcium and phosphates, the hydroxyapatite can be produced through precipitation, from solid state reactions at high temperature, from an aqueous solution combustion technique, and it can also be obtained naturally from calcinations of animal bones [5,6] or from hydrothermal synthesis. In the circumstance of the safety of repositories of nuclear waste, and also for assessing radionuclide mobility in industrial wastes or environment, the interaction between lanthanides and actinides with sorbents has become a main subject matter of many studies. Complex formation has been explained by several models (e.g. diffuse layer and non-electrostatic models). Europium belongs to the REE; only its trivalent oxidation states are stable in aqueous solutions. Its chemical behaviors have been considered typical of REE and of some trivalent actinides as well. In contrast, europium is used mainly in the manufacture of cathode ray tubes, fluorescent lamp and screen for X-rays; in the nuclear industry, europium is used as absorbent of neutrons for the extinction and control rods of the reactors. The isotopes of these elements are considered toxic for the human health [7]. Thus, the study of Eu(III) sorption on inorganic materials is essential for the control of these elements in the environment. In wastewater treatment, the study of sorption kinetics provides valuable insight into the mechanism of sorption reaction and into the reaction pathways. Indeed, europium sorption on several materials is now well understood [8–16]. However, as far as we know, not many studies about their sorption on hydroxyapatite have been done. The purpose of this study was to investigate the sorption behavior of Eu(III) ions from nitrate aqueous solution (as a representative of lanthanide and radioactive materials) onto thermally prepared nano-pore hydroxyapatite and to evaluate the potential of this material to adsorb these REE ions. These studies were dedicated to the preparation process and to the description of sorption process. The kinetics, equilibrium and thermodynamics parameters of the sorption onto prepared nano-pore hydroxyapatite have been analyzed and discussed in the light of current known models available in literature, and relevant parameters were determined.