Within waste materials, technology critical metals such as Lithium (Li), Cobalt (Co), and rare earth elements are frequently embedded within intricate architectures composed of various components, including organics such as plastics and epoxy resins, inorganics like ceramics, and base metals such as aluminium and iron. The recycling of these technology critical metals presents a complex undertaking due to the necessity of effectively dismantling these multi-layered structures in order to access and recover the valuable elements. Additionally, the purification of these metals poses another significant challenge within the recycling processes.
In present recycling processes, the distinct layers within waste materials are typically treated indiscriminately. This involves procedures such as shredding the materials, subjecting metals to harsh chemical conditions to oxidise and dissolve them, or subjecting the waste to elevated temperatures. Unfortunately, this non-selective approach often results in the loss of technology critical metals. Moreover, these conventional processes contribute to the generation of harmful substances including hazardous gases, dust particles, and chemicals. The methods employed also incur substantial energy and chemical consumption, further exacerbating the environmental footprint of the recycling processes.
To enhance recycling efficiency and minimize the environmental impact of recycling, a toolbox of processes has been elaborated. Each of these tools is meticulously designed to target weaknesses at the interfaces between distinct layers, enabling the liberation, purification, and recovery of technology critical metals. This toolbox comprises a range of innovative tools. Ultrasounds are used to process brittle inorganic materials and facilitate the liberation of metals, while solvolysis is used to dissolve organics effectively. Hydrogen embrittlement and selective dissolution, using recyclable and sustainable oxidizing agents, are implemented to purify metals. By combining these tailored tools, we aim to improve the extraction efficiency and reduce the environmental impact of recycling technology critical metals from complex waste matrices.
These processes were successfully applied to diverse sources of wastes. Some examples include ultrasonic delamination of spent lithium-ion batteries (Li, Co, Ni, Mn), hydrogen processing of magnets (Nd, Dy), dissolution and purification of metals from solar cells (Ag, Al), recovery of semiconductor legs and copper from thermoelectric materials (Cu, Sb, Se, Te, Bi). Other waste investigated include various printed circuit-boards, X-ray protective garments, various catalysts, laminated films and various alloys.