Physical Processing in Waste Printed Circuit Boards Recycling: Current State of Research

The article presents and compares the results of metal separation from pulverized printed circuit board waste (PCBs) using physical and physicochemical processing methods. PCBs type FR4 were used for the research, which were ground at cryogenic temperatures using a knife mill. Separation processes for the same feed were carried out using electrostatic and gravitational separation, and flotation. Compared to the other PCB recycling methods, the ones presented in the paper have a lower environmental impact and allow the reuse of both metals and non-metallic parts. The highest efficiency was for electrostatic separation, as a result of which the following products were obtained: 26.2 wt% metal product, 2.8 wt% middlings and 71 wt% a product containing non-metallic parts. The products obtained in this way are easy to use in other processes. A product containing valuable metals can be processed in local metal processing plants, while shredded non-metallic parts can be a good filler for epoxy resin composites. Furthermore, electrostatic separation in comparison to other used methods has the lowest environmental impact because there was no need to use water and complications associated with it. Thus, the technology of PCB recycling proposed in the work is characterized by high efficiency and is environmentally friendly.