Recent chemical methods for metals recovery from printed circuit boards: A review

Abstract

As the volume of e-waste continues to rise, it is crucial to sustainably manage printed circuit boards (PCBs) and their valuable metal components. PCBs are ubiquitous in modern society, powering a variety of electronic devices. The metal resource crisis and the imperative for a low-carbon circular economy have accelerated the development of e-waste recycling technology. High-value discarded PCBs represent a vital component of e-waste. However, discarded PCBs are deemed hazardous to the ecosystem due to the presence of heavy metals and brominated organic polymers. Thus, recycling metals from discarded PCBs is not only a strategic necessity for fostering a green ecological civilisation but also a crucial guarantee for ensuring a safe supply of mineral resources. This comprehensive review gives the profound details of PCBs, and the performance of and advances in the latest chemical metal recovery methods. Reviewing the latest metal recovery processes, we explored the application of diverse leaching agents, including ionic liquids (ILs), deep eutectic solvents (DESs), organic acids and amino acids. These solvents were assessed in terms of their recovery efficiencies, and most of them demonstrated excellent leaching performance. The role of optimising leaching parameters such as concentration, oxidants, pH, particle size, solid-to-liquid ratios (S/L), temperature, and contact time is underscored, offering insights into achieving sustainable PCB recycling practices. Most of these recent leaching methods successfully extracted base metals (Cu, Fe, Zn, Sn, etc.), as well as precious metals (Au and Ag), achieving leaching efficiencies exceeding 90.0%. Interestingly, their effectiveness can compete with that of traditional hydrometallurgical methods.