On the use of biotechnologically functionalized magnetic nanoparticles for the recycling of valuable ultrafine powders from electronic waste

Electronic waste contains high amounts of valuable metals in the form of ultrafine (<10 µm) inorganic powders [1]. Currently, only a minor fraction of these metals is recycled economically. Separation of the inorganic powders would strongly enhance the recyclability of these secondary resources. However, the most prominent particle separation (froth flotation, gravity, magnetic and electric separation) processes were developed by the mining industry for primary particles [2,3]. These processes are only partially suitable for secondary resources and face challenges with regards to the ultrafine particle sizes and the high complexity (typically, >60 elements are present in electronic waste). In a novel approach, we propose the use of magnetic carriers derived from various life science applications (such as magnetic drug delivery, purification, hyperthermia, imaging, etc. [4]) for the magnetic separation of critical raw materials from electronic waste. Magnetic nanoparticles (MNPs) exhibit excellent properties and can be synthesized cost-effectively. The small size and high specific surface area of ultrafine powders provide benefits for the attachment of MNPs, as opposed to their hindrance of conventional separation processes. Achieving attachment selectivity of MNPs to the desired target powders is crucial for the selectivity of the separation process. This draws inspiration from the common practice of MNP functionalization with biomolecules in the aforementioned fields of life science[5]. In this presentation, we discuss a case study involving biotechnologically functionalized MNPs for the carrier magnetic separation of rare-earth element-containing phosphors from fluorescent lamps Figure 1 [6,7]. We provide a comprehensive overview of MNP synthesis and functionalization, determination of their interaction affinity with various phosphors, application in magnetic separation, as well as post-separation detachment and MNP reuse. Special emphasis is placed on MNP colloid