Low Temperature Pyrolysis and Exfoliation of Waste Printed Circuit Boards: Recovery of High Purity Copper Foils

Abstract

Although several techniques have been developed to extract copper from waste printed circuit boards (PCBs), there remain several challenges regarding energy consumption, local area contamination and environmental damage. A novel technique has been developed for extracting copper foils from waste PCBs based on low temperature pyrolysis followed by exfoliation to overcome these issues. The standard pretreatment steps of removing electronic components from PCBs and mechanical processing/size-reduction/powdering, etc., were minimized in this study. Several unsorted 'as received' PCBs were heat treated in the temperature range 750-850 degrees C for 5-20 min. in an argon atmosphere. Brittle dark chars and other residues on the heat-treated specimens were scrapped off to separate copper foils and other residuals. Most of the electronic components mounted on PCBs had dropped off during the heat treatment. Good-quality copper foils were recovered in all cases; the purity of copper was in excess of 85 wt.%. Key impurities present were Pb, Sn and Zn with typical concentrations less than 4 wt.%. Key features of the technique include minimizing energy intensive pre-treatment processes and waste handling, low pyrolysis temperatures and short heating times. This energy-efficient approach has the potential to enhance resource recovery while reducing the loss of materials, local area contamination and pollution near e-waste processing facilities.