A simple and efficient method for selective recovery of copper from nitric acid leaching solution of printed circuit boards containing nickel, zinc, lead, aluminum, and iron

The Cu content in discarded printed circuit boards (PCBs) is a crucial aspect, and employing suitable methods for the recovery of Cu holds significance in resource recovery. However, the selective recovery of Cu from an acidic leaching solution containing multiple metals such as Ni, Zn, and Pb poses challenges. L-cys contains the thiol (-SH), the amino (-NH2) 2 ) and the carboxyl (-COOH) groups, which may complex with metal ions. In particular, the reaction between thiol groups and metal ions makes it possible to recover Cu. In this study, we propose an innovative method using L-cysteine (L-cys) to recover Cu from the acidic leaching solution of discarded PCBs. The effects of Ni2+, 2 + , Zn2+, 2 + , Pb2+, 2 + , Al3+, 3 + , and Fe3+ 3 + irons on the recovery of Cu were studied based on the concentration of these metal ions in PCBs. Adding 120 mL of 2 g/L solution of L-cys to 100 mL of 500 mg/L solution of Cu(NO3)2 3 ) 2 achieved the complete recovery of Cu by forming precipitates. The Ni2+, 2 + , Zn2+, 2 + , Pb2+, 2 + , and Al3+ 3 + ions did not affect the recovery of Cu within the studied metal concentration range in the acidic leaching solution. However, approximately 20% of the Fe3+ 3 + is coprecipitated during the recovery of Cu. This is mainly affected by the amount of colloid formed when copper precipitates in the solution. The interference of Fe3+ 3 + on copper recovery can be effectively reduced by controlling the volume of L-cys to reduce the formation of colloid. Fourier transform infrared and X-ray photoelectron spectroscopy analyses demonstrates the chemical action between the functional groups in L-cys and Cu2+. 2 + . Compared with nickel, zinc and lead ions, copper ions have the strongest binding ability with (-SH), amino (-NH2) 2 ) and carboxyl (-COOH) groups. This result explains why L-cys can selectively recover copper from leaching solution. This method offers advantages such as fast reaction rates, convenient operating conditions, and enhanced selectivity, which is a promising avenue for the clean and efficient recovery of Cu from discarded PCBs.