Gold Metal Recovery from Electronic Waste through Laser Generation of Micro and Nanoparticles

Electronic waste (E-waste) is the fastest-growing waste stream globally, reaching 74.7 tonnes by 2030, containing significant amounts of valuable metals such as gold, silver, platinum, and copper. Mechanical, hydrometallurgical, pyrometallurgical, electrochemical, and biotechnological methods for recovering these metals from E-waste are often inefficient, costly, and environmentally harmful. This study presents the first demonstrations of laser ablation in recovering gold in the form of micro and higher-valued nanoparticles from E-waste. The ablation threshold is identified using modeling performed using the two-temperature model (TTM). Printed Circuit Boards (PCBs) with gold-plated electrodes were used as the target material. The laser ablation process was conducted using a picosecond UV-355 nm laser at maximum average laser power (18 W). The analysis, using UV-visible spectroscopy, shows the surface plasmon resonance peak at 523 nm for gold nanoparticles-(Au NPs), and SEM-EDX mapping confirmed the successful creation of high-purity (90 wt %) Au NPs with an average size of 100 nm. Laser-Induced Breakdown Spectroscopy (LIBS) was used to monitor the elemental composition of the E-waste sample during the ablation process to demonstrate real-time processing monitoring. The ability to recover gold in nanoparticle form further enhances the economic viability of this technique giving a wide range of applications for gold nanoparticles in various fields. The findings underscore the potential of laser ablation as a sustainable solution for E-waste recycling, addressing critical global challenges related to the recovery of valuable materials.