Recycling of Waste Printed Circuit Boards by Microwave-Induced Pyrolysis and Featured Mechanical Processing

The combination of microwave-induced pyrolysis and mechanical processing is a promising way to recycle the waste printed circuit boards (WPCBs). In pyrolysis, WPCBs yield an average of 78.6 wt.% solid residues, 15.7 wt.% oil, and 5.7 wt.% gas. The solid residues are rich in metals; the oil is abundant with phenol and substituted phenols which can be reclaimed as chemicals or fuels; and the gas is combustible with a caloric value of 4504 kcal/m(3). Our featured mechanical processing, including crushing and specially designed sink-float separation, is very suitable for metal reclamation from the pyrolysis residues. Over 99 wt.% of metals can be dissociated by the crushing step; the final recycling rate and grade of metals in the separation step can amount to 95 wt.% and 96.5%, respectively. The economic assessment reveals that the combined treatment is amazingly profitable and very promising to tackle the challenges posed by the electronic scraps.