Abstract
This paper proposes an optimized method for the determination of rare earth elements (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) from soils using ICP-MS technique. First, the soil samples were thermal treated at three different temperatures 550ºC, 700ºC and 8500C in order to eliminate organic matter interferences. Then, the residual samples remaining from the calcination process were extracted in acidic medium with two different digestion methods (method I - a mixture of nitric acid and hydrogen peroxide; method II - aqua regia mixture) in order to quantify rare earth elements content. The highest recovery percentages for the major rare earth elements analyzed (Sc, Y, La, Ce, Pr, Nd. Sm) were situated in the range 86.13% to 99.90%, in sample residues thermally treated at 700�C and extracted with nitric acid and hydrogen peroxide.
Highlights
The rare earth elements (REEs) represent a group of 17 elements, which contain 15 lanthanides (lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu)), scandium (Sc) and yttrium (Y)
The physical-chemical characterization of soil samples Some specific analysis were performed for the physical-chemical characterization of the soil samples in order to highlight the influence of these characteristics on the tested mixtures extraction capacity for REEs
In this sense, was observed higher conductivity, TOC and total nitrogen were determined at P1, P2 and P3, total nitrogen content being twice than in P4, P5 and P6 soil samples
Summary
The rare earth elements (REEs) represent a group of 17 elements, which contain 15 lanthanides (lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu)), scandium (Sc) and yttrium (Y). The lanthanides are very important in green-economy, because in modern technology these elements are used in different devices: permanent magnets, lamp phosphors, rechargeable nickel metal hydride batteries, catalysts, medical-devices and for other application [1,2,3,4,5,6,7,8,9, 10]. The European Commission and U.S Department of Energy mention the lanthanides as the most critical raw materials for all the industries, five critical rare earths being europium, terbium, dysprosium, neodymium and yttrium [15, 16]. The REEs are used in high-tech industry, electronics and medicine, so it was stimulated the geochemists interest on their environmental behaviour and potential toxicity [17, 18]
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