Identification of yttrium oxide-specific peptides for future recycling of rare earth elements from electronic scrap

Yttrium is a heavy rare earth element (REE) that acquires remarkable characteristics when it is in oxide form and doped with other REEs. Owing to these characteristics Y₂ O₃ can be used in the manufacture of several products. However, a supply deficit of this mineral is expected in the coming years, contributing to its price fluctuation. Thus, developing an efficient, cost-effective, and eco-friendly process to recover Y₂ O₃ from secondary sources has become necessary. In this study, we used phage surface display to screen peptides with high specificity for Y₂ O₃ particles. After three rounds of enrichment, a phage expressing the peptide TRTGCHVPRCNTLS (DM39) from the random pVIII phage peptide library Cys4 was found to bind specifically to Y₂ O₃ , being 531.6-fold more efficient than the wild-type phage. The phage DM39 contains two arginines in the polar side chains, which may have contributed to the interaction between the mineral targets. Immunofluorescence assays identified that the peptide's affinity was strong for Y₂ O₃ and negligible to LaPO₄ :Ce³⁺ ,Tb³⁺ . The identification of a peptide with high specificity and affinity for Y₂ O₃ provides a potentially new strategic approach to recycle this type of material from secondary sources, especially from electronic scrap.