Liberation of valuable materials in waste printed circuit boards by high-voltage electrical pulses

• Material morphology and chemical composition is analyzed by SEM.
• Inside discharge channel and compression wave mechanism are elucidated.
• Physical and chemical reactions of materials represent as a particular phenomenon.
• HV breakage can achieve both complete liberation and metal concentration.

Printed circuit boards (PCBs) are found in every electrical and electronic equipment. In this study, epoxy resin was employed as the model material to conduct high-voltage (HV) electrical pulse experiments. A complete liberation of PCBs was achieved using SELFRAG Lab, and the surface morphology and chemical composition of suspended particles were analyzed by SEM. The results show that the liberation and crushing mechanism of PCBs mainly include the formation and expansion of discharge channels, transformation of shock wave, reflection and refraction effects, and physical and chemical reactions under the high-pressure environment; among all of them, the physical and chemical reactions between metal and organics are specific phenomena, which only exist when using HV electrical pulses for the crushing process of waste PCBs. Furthermore, the results also show that HV electrical pulses can achieve a narrow-fraction metal concentration; this feature is conducive for the separation of metals from epoxy resin in the future. In particular, the crushing performance reaches its best level when the electrical pulse reaches 400, during which 97.92% copper was accumulated in −2 mm products.