A preliminary study of a sequential leaching process to recover Ag, Au, Cu, and Sn from E-waste

Abstract

The rapid growth of electronic waste (e-waste) presents both environmental challenges and economic opportunities. This study investigates efficient methods for recovering valuable metals from printed circuit boards (PCBs) using hydrometallurgical processes. The PCB samples from various end-of-life electronic devices were subjected to a series of five leaching stages targeting the leaching of Ag, Au, Cu, and Sn. The first stage using 3 mol/L nitric acid achieved 97 % Cu leaching, reducing Cu content from an average of 20 % (w/w) to 0.74 % (w/w). This stage also affected other metals, leaching 53 % of Ag and 78 % of Sn. Subsequent leaching with thiourea in acidic media containing Fe(NO₃)₃ leached 75 % of Au. An iodine/iodide leach with H₂O₂ as an oxidizer proved highly effective for Ag, with 99 % leaching. This stage also leached an additional 62 % of Au. Two methods for Sn leaching were compared: HCl leaching achieved 98 % efficiency; H₂SO₄ with CuSO₄ also achieved 98 % leaching efficiency. Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) was used to analyze metal concentrations throughout the process. This sequential leaching approach demonstrates the potential for high-efficiency recovery of valuable metals from e-waste, contributing to both economic benefits and environmental sustainability in electronic waste management. The study highlights the complexity of metal interactions with leaching reagents and the importance of optimizing each stage for selective and efficient recovery of metals from e-waste.