Sorption of rare-earth elements onto a ligand-associated media for pH-dependent extraction and recovery of critical materials

Abstract

Toward recovering rare-earth elements, we prepared a solid-phase media that binds and elutes metals for extraction and enrichment. We report the synthesis and methodology for a solid-phase media that exhibits pH-dependent binding of aqueous rare-earth elements. The media shows pH-dependent binding of NdIII and retains efficiency over at least six cycles of binding and elution. Mixed solutions of rare-earth elements demonstrated a preference for mid and heavy rare-earth elements based on thermodynamic binding preferences of the ligand, and selectivity for rare-earth elements over iron and aluminum were observed with coal fly ash leachate. We expect this new recovery method to be a significant step towards aqueous-based extraction and enrichment of critically important rare-earth elements.