Peptide-based biomagnetic separation for the recycling of critical raw materials from ultrafine particles in complex waste streams

In the global transition towards a low-carbon economy, the current dependence of fossil fuels is rapidly replaced by an increased demand in critical raw materials (CRMs). For example, rare-earth elements (REEs) play an essential role in the large-scale electrification, due to their requirement for the production of permanent magnets, lamp phosphors and rechargeable batteries [1]. However, the REEs’ supply chain is under a high pressure due to a combination of the rising demand, a monopolistic market structure and very low overall recycling rates [2]. The Helmholtz Institute Freiberg for Resource Technology (HIF) aims to promote the energy transition by developing innovative methods and technologies along entire material cycles, ranging from the exploration, to the recycling of CRMs. In this context, the application of biotechnological methods (such as biosorption, bioleaching and biocomplexation) could offer feasible and green solutions for the recycling of complex waste streams, resulting in increased recycling rates of CRMs [3].

At the HIF, the junior research group BioKollekt aims to develop a feasible and upscalable biomagnetic separation method for a novel recycling process of CRMs in the form of ultrafine particles. As a proof of concept, we are currently focussing on the recycling of REEs from fluorescent lamp phosphors. We have identified surface binding peptides, i.e. a type of biomolecules, that selectively bind to the green phosphor LaPO4:Ce,Tb [4]. Subsequently, we have functionalized various magnetic carriers, such as composite beads, core-shell magnetic nanoparticles and bacterial magnetosomes, with the identified peptides. The obtained bifunctional materials (due to their 1) highly selective binding to target particles and 2) high response to an external magnetic field) are ideal carriers to facilitate a separation in challenging waste streams. Finally, using the target materials, we have conducted lab-scale binding experiments, as well as, upscalable separation experiments in a high-gradient magnetic separator (HGMS) [5,6]. In the coming period, we will work to develop an integrated multistep separation process for REE phosphors and explore the possibilities to expand our method to other waste streams.