Leaching and sequential electrowinning of Cu and Sn from silicon solar modules

Metal separation and recovery are a key aspect of silicon solar module recycling. This paper provides a fundamental understanding of the leaching and electrowinning in hydrochloric acid of two critical metals in silicon solar cells: copper and tin. A leaching model for solder-coated copper wires was developed to reveal rate orders with respect to concentrations of leaching agents and stirring. Kinetic parameters for electrowinning of copper and tin were determined through Tafel and electrochemical impedance spectroscopy analysis. Cyclic voltammetry was used to determine redox potentials of copper and tin allowing their electrochemical separation. Finally high recovery rates and high metal purity, both over 99 %, were achieved for copper and tin through sequential electrowinning. Hydrochloric acid leaching and sequential electrowinning provide a simple and effective option for the recovery of copper and tin from silicon solar modules. • Soldered wire leaching model reveals rate order of 1 for [HCl] and 1.33 for [H 2 O 2 ]. • Copper and tin completely separated with purity and recovery >99 %. • EIS and Tafel analysis reveal I o of 4.7 and 26.6 mA/cm 2 for Cu and Sn respectively.