Nanostructured organosilica hybrids as highly efficient and regenerable sorbents for rare earth extraction

Due to the rapidly growing energy demand and increasing production of high technology devices, the development of new sequestration materials for rare earth elements (REEs) has become critical. Nowadays, lanthanides (Ln) play a major role as supplies for the transition to cleaner energy and production of economically important modern devices, like wind turbines (Pr, Nd, Sm, Dy), batteries (La), fluorescent and luminescent phosphor lamps (La, Gd, Tb, Eu, Yb), car catalysts (Ce) or hybrid vehicles (Dy, La, Nd). However, for all these applications, only a high purity fraction of a single rare earth element can be used. Frequently, the presence of other REEs as contaminants in a pure single-element REE fraction alters the efficiency of electronic/optic devices. Although, several methods have been used for REEs extraction, such as liquid-liquid extraction (LLE) or liquid-solid extraction (supported liquid-liquid extraction, SLE, solid-phase extraction, SPE), the selective separation and purification of REEs still remain challenging. Mostly, the difficulties arise from the fact that these metals have very similar chemical properties. Among various extracting agents used for lanthanide separation, the diglycolamide (DGA)-based materials have attracted great attention as some of the most effective agents. In this contribution, we review our advances concerning the development of mesoporous hybrid sorbents for REEs. In particular, series of DGA-modified mesoporous silica (KIT-6) sorbents were synthesized and tested for the REEs separation. Moreover, it has been proposed that by tunning the ligand bite angle and/or its environment it becomes possible to tune the extraction selectivity.