Chemical Recycling of Printed Circuit Board Waste by Depolymerization in Sub- and Supercritical Solvents

Disposal of waste printed circuit boards is regarded as a potential major environmental problem due to their heavy metal content. Therefore, recycling waste printed circuit boards represents an opportunity to recover the high value resin chemicals and the high value metals that are present. In this study, the solvo-thermal depolymerisation of waste printed circuit boards obtained from desktop computer monitors was carried out using water, ethanol and acetone between 300 and 400 °C. Alkalis (NaOH, KOH) were used as additives to promote the removal of the resin fraction of the printed circuit boards. At 400 °C, 94 % resin removal was achieved when water was used as the solvent, in the presence of NaOH. The liquid produced in the process was analysed by GC/MS and the results showed that it was mainly composed of phenol, and some phenolic compounds, with up to 62.5 wt% present as phenol in the liquid phase.