Chapter 8 - Selective recovery of rare-earth elements from diluted aqueous streams using N- and O-coordination ligand–grafted organic–inorganic hybrid composites

Abstract

The dominance exerted by the rare-earth elements (REEs) on the significant technological advancements of the past decades has been unmitigated and unparalleled. With such an eminent role played by REEs, there exists a constant battle in striking a balance between the supply to demand ratio, especially due to the geographical constraints imposed by the natural distribution of these elements. With China, the major producer of REE (over 95%) imposing severe restrictions on exports coupled with the closure of several operating mines has led to the dire need of finding alternate means to fulfill the resource requirement through sustainable and self-sufficient means. Hence, alternate routes for primary REE production to acquire a steady and self-reliant supply of these elements are constantly explored. Furthermore, much emphasis has been laid on finding schemes that fit well within the scope of a circular economy. The utilization and reuse of waste resulting from a number of industrial processes hold the potential to function as secondary raw materials for REE procurement. However, the establishment of efficient schemes to accomplish this goal can be hugely challenging. One prominent example would be the recovery of low concentrated REEs effectively and selectively from diluted industrial streams, i.e., from massive amounts of wastewater. For this purpose, adsorption would be of great relevance in metal recovery from dilute aqueous solutions with the domain being constantly updated through the state-of-the-art methodologies and design of efficient adsorbents for a variety of applications.