Handbook of Rare Earth Elements

Analytics

Alfred Golloch

• Publisher: De Gruyter
• Year: 2017
• Print ISBN: 9783110365238
• eBook ISBN: 9783110391251
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Analytic Chemistry

The Handbook of Rare Earth Elements focuses on the essential role of modern instrumental analytics in the recycling, purification and analysis of rare earth elements. Due to their numerous applications, e.g. in novel magnetic materials for computer hardware, mobile phones and displays, rare earth elements have become a strategic and valuable resource. The detailed knowledge of rare earth element contents at every step of their life cycle is of great importance.

This reference work was compiled with contribution from an international team of expert authors from Academia and Industry to presend a comprehensive discussion on the state-of-the-art of rare earth element analysis for industrial and scientific purposes, recycling processes and purification of REEs from various sources.

Written with Analytical Chemists, Inorganic Chemists, Spectroscopists as well as Industry Practitioners in mind, the Handbook of Rare Earth Elements is an indispensable reference for everyone working with rare earth elements.

Alfred Golloch

1Introduction

Rare earth elements (REEs) are a group of chemical elements in the periodic table, including the 15 elements from lanthanum (La, 57) to lutetium (Lu, 71), scandium (Sc, 21) and yttrium (Y, 39). This grouping was agreed by the IUPAC [1]. The elements scandium and yttrium differ in their atomic structure from the lanthanides but their chemical and physical properties are very similar (Figure 1.1).

The abundance of the REEs in the earth’s crust follows a pattern in the periodic table. Lanthanides with even atomic numbers are more common in nature than lanthanides with odd atomic numbers.

Figure 1.2 shows the pattern of REE abundance in the earth’s crust and it can also be noted that the abundance of REEs with lower atomic numbers is higher than the abundance of REEs with higher atomic numbers. Regarding this scope the first group is called “light REEs (LREEs)” and the second one “heavy REEs (HREEs)” (see Table 1.1). Other attempts have been made to subdivide REEs into groups.

Figure 1.1: Periodic table of elements.

 

Figure 1.2: Abundance of the rare earth elements in the earth’s crust (Harkins rule) [2].

 

Figure 1.3: Main applications of rare earth elements (Source: Öko-Institut e.V.).

Table 1.1: List of light and heavy REEs.

In most deposits of REEs, the share in LREEs is higher than 90 % and the percentage of HREEs is 2–3 %.For “High-Tech” applications mainly HREEs are used and the demand for these elements is obvious.

Figure 1.3 presents the most important applications of REEs [3].

References

[1]International Union of Pure and Applied Chemistry (IUPAC): Nomenclature of Inorganic Chemistry, Definition Rules 1970. London, Butterworths, 1971.

[2]Riedel E, Janiak C. Anorganische Chemie. Berlin and New York, DeGruyter, 2011.

[3]Öko-Institut e.v. Hintergrundpapier Seltene Erden, Stand: Januar 2011, Seltene Erden-Daten und Fakten, S. 5

Alfred Golloch

2Analytics of Rare Earth Elements – Basics and Methods

Abstract: A short summary of the electronic configuration of the RE elements gives proof for the analytical properties of the lanthanoides ions. The chemical reactions of the Ln³⁺ ions and of RE elements with “unusual” oxidation states are compared. The introduction to the scientific contributions of the handbook is realized by the presentation of the historical development of REE analytics from 1940 to present.

2.1Electronic configurations of RE elements and analytical properties

The electronic configuration of the rare earth elements (REEs) is the key for understanding the analytical properties of the elements [1, 2]. Table 2.1 shows the electronic configurations of the ground state of REE atoms and of the ions.

The ground state configurations for the majority of lanthanoides can be summarized as 4^fn+1 6s², except the following elements:

Lanthanum	5d^16s^2
Gadolinium	4f^7 5d^1 6s^2
Lutetium	4f^14 5d^1 6s^2
Scandium	3d^1 4s^2
Yttrium	4d^1 5s^2

In general, the f-levels of the lanthanoid atoms are filled with electrons and the N shell is filled up to the maximum of 32 electrons. The energy of 6s, 5d and 4f levels are very similar and as a result there is an irregular fill of the energy levels. It can be noted that the half-filled (4f⁷) and the completely filled 4f subshell are preferred. The fill of the inlying 4f subshell with electrons slightly affects the chemical properties of the elements. The ground state configurations are not important for the analytical behaviour, but the trivalent ionic configurations are more important. The trivalent ions are formally generated when the valence electrons are removed. The radii of the Ln³⁺ ions are very similar to the radii of Sc³⁺ and Y³⁺ ions. This electronic similarity causes the chemical similarity and that is the reason for including elements of group 3 of the periodic table in considerations of the chemistry of lanthanoides.

Table 2.1: Electronic configuration of the rare earth elements [1].

2.1.1Chemistry of Ln³⁺ ions

The radii of the Ln³⁺ ions continuously decrease with the increasing atomic number of the elements (lanthanoid contraction) (Figure 2.1).

The lanthanoid contraction is the reason for the resemblance of 4d and 5d elements of the subgroups of the periodic table. The lanthanoid contraction is responsible for the regular amendment of some lanthanoid properties. The chemistry of the Ln³⁺ ions is similar to the ch...

Table of contents

• Cover
• Titelseite
• Impressum
• Preface
• Contents
• List of Contributing Authors
• 1 Introduction
• 2 Analytics of Rare Earth Elements – Basics and Methods
• 3 Separation/Preconcentration Techniques for Rare Earth Elements Analysis
• 4 Chromatographic Techniques for Rare Earth Elements Analysis
• 5 Analysis and Speciation of Lanthanoides by ICP-MS
• 6 Inductively Coupled Plasma Optical Emission Spectrometry for Rare Earth Elements Analysis
• 7 Application of Spark Atomic Emission Spectrometry for the Determination of Rare Earth Elements in Metals and Alloys
• 8 Use of X-ray Fluorescence Analysis for the Determination of Rare Earth Elements
• 9 Neutron Activation Analysis of the Rare Earth Elements (REE) – With Emphasis on Geological Materials
• 10 Automated Quantitative Rare Earth Elements Mineralogy by Scanning Electron Microscopy
• 11 Novel Applications of Lanthanoides as Analytical or Diagnostic Tools in the Life Sciences by ICP-MS-based Techniques
• 12 Lanthanoides in Glass and Glass Ceramics
• 13 Analysis of Rare Earth Elements in Rock and Mineral Samples by ICP-MS and LA-ICP-MS
• 14 Recycling of Rare Earth Elements
• Index