Recycling of copper from waste printed circuit boards by modified supercritical carbon dioxide combined with supercritical water pre-treatment

Copper is one of the main elements used in printed circuit boards (PCBs) of electronic products. This study aims to find a way to make the supercritical CO2 extraction method more efficient for copper recovery from PCBs waste. For this purpose, supercritical water was applied to PCBs waste as a Pre-treatment process to increase the concentration of copper during the initial solid feed. To increase copper's solubility in CO2, the solvents methanol, ethanol, propanol solvents were used along with complexing agents of cyanide 301, 302 and tri-butyl phosphate. Investigations were carried out to determine the effects of static/dynamic times, as well as pressure and temperature on extraction efficiency. Consequently, cyanide 301 and methanol were selected as best ligand and co-solvent, respectively. The optimum condition, in which Copper Extraction Efficiency reached 97 % with high purity (98.7 %), was obtained at 60 degrees C temperature, 200 bar pressure, 30 min residence time, and 1 ml/min CO2 flow rate.