Microwave absorbent enhancement of multi-thermal field effect: Pyrolysis of waste printed circuit boards

This study explores the use of silicon carbide (SiC) as a microwave absorbent to enhance the microwave pyrolysis efficiency of waste printed circuit boards (WPCBs) and improve copper (Cu) leaching rates. The results demonstrate that microwave pyrolysis promotes surface enrichment of Cu. By adding large SiC particles, the pyrolysis rate was increased by 40% and the leaching rate improved by 15% compared to conventional heating methods over the same time period. Additionally, microwave absorption by SiC particles of varying sizes generated different thermal effects. Small SiC particles increased the effective heat contact area but absorbed microwaves on the sample surface, suppressing microwave-metal discharge phenomena and reducing the temperature input from corona discharge. In contrast, large SiC particles absorbed microwave energy and formed hotspots, which enhanced pyrolysis efficiency. These large particles can be easily recovered and reused through simple physical sieving during subsequent hydrometallurgical leaching. The findings suggest that SiC, as a microwave absorbent, offers a novel approach for the efficient and sustainable recycling of WPCBs.