Recovery of valuable metal concentrate from waste printed circuit boards by a physical beneficiation technology

It is greatly significant to separate precious metals from the waste printed circuit boards (PCBs) with appropriate methods for the resource recycling and environment protection. A combined physical beneficiation technology for the recovery of waste PCBs was investigated. Waste PCBs were disassembled into substrates and slots firstly. Waste PCB substrates were crushed to the size below 1 mm by a wet impact crushing approach. The double Rosin–Rammler functions were proposed to describe the particle size distribution characteristic of the substrates. The crushing products of the substrates were separated by a self-designed water-medium tapered column separation bed. The results indicate that the separation efficiency of 93.9 % and metal recovery rate of 93.7 % are obtained with a water discharge of 5.5 m³/h, feeding capacity of 250 g/min and inclination angle of 35°. Waste PCB slots were crushed to the size range of 0.5–5 mm by a dry impact crushing approach and separated by an active pulsing air classifier. The separation results show that a separation efficiency of 92.4 % and metal recovery rate of 96.2 % are obtained with the airflow velocity of 2.90 m/s and pulsing frequency of 2.33 Hz. The mismatching components in the metal concentrate are relatively less with suitable operating conditions. Precious metals could be obtained by the further separation and purification of metal concentrates. The technology has great potential to be applied in the field of waste PCB recycling.

Keywords
Waste printed circuit boards (PCBs); Wet impact crushing; Water-medium tapered column