Electrokinetic Remediation for Environmental Security and Sustainability

7Rare Earth Elements: Overview, General Concepts, and Recovery Techniques, Including Electrodialytic Extraction

Nazaré Couto^1,2, Ana Rita Ferreira^1,2, Vanda Lopes^1,2, Stephen Peters³, Sibel Pamukcu², and Alexandra B. Ribeiro¹

CENSE – Center for Environmental and Sustainability Research, Department of Environmental Sciences and Engineering, NOVA School of Science and Technology, NOVA University Lisbon, 2829‐516 Caparica, Portugal

Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA 18015, USA

Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, USA

7.1 Introduction

7.1.1 Rare Earth Elements: Characterization, Applications, and Geo‐Dependence

Rare earth elements (REEs) are a group of 17 chemically similar elements composed of 15 lanthanides plus scandium and yttrium [1] (Table 7.1). The concentration of lanthanides varies in nature, except for promethium, which is not normally found due to the very short half‐life of its isotopes [3, 4]. REEs can be divided into light rare earth elements (LREEs) and heavy rare earth elements (HREEs) according to their atomic number. In Europe, LREEs include elements between La and Sm, whereas in China, Sm is a HREE [3]. Although their electronic configurations are similar, with most of these elements partially occupying 4f electron orbitals, their distinct physical and chemical properties enable their use in a broad range of technologies [4]. Most REE become trivalent in a metallic ...