Recovery of rare earth elements by peptide-induced lanthanide ion precipitation

Electronic waste and wastewater from mining and industrial processes are valuable sources of strategic high-tech metals such as rare earth elements (REEs). Due to low concentrations of REEs in secondary resources, their recovery is challenging. Biomolecules, as renewable and environmentally friendly separation tools, offer promising alternatives, as metal-binding peptides can combine selectivity, stability and biodegradability. To screen for peptides with high affinity for REEs, we successfully utilized phage surface display (PSD). The selected peptide GC22 (CEPDLWIDRFWC), identified by PSD in combination with next-generation sequencing, revealed the ability to precipitate lanthanide and yttrium ions from aqueous solutions with high efficiency. It largely favored REE ions over other commonly occurring metal ions in wastewater. Precipitation assays yielded high recovery efficiencies of >80 % in real wastewater, with minimal co-precipitation of non-REE metals except for aluminum, lead and uranium. The amorphous REE-GC22 precipitate was characterized by curled and spherical structures. Reversibility of binding and thus regeneration of the peptide was demonstrated, enabling its potential use for multiple extraction cycles. GC22 thus offers a promising peptide-based strategy for future REE recovery from low-REE-concentration wastewaters and e-waste leachates.