Study of the effect of the pretreatment and the concentrations of iron (II) and chloride, on the electrochemical leaching of waste printed circuit boards using ANOVA analysis

• The electrochemical leaching of WPCBs has been statistically analyzed using ANOVA. • The effect of pretreatment, Fe 2+ and Cl − concentrations have been studied. • Cu, Ag and Au are selectively electro-leached using mild conditions. • A sequential and easily scalable green recycling process is proposed. • The proposed process would allow the valorization of spent pickling acids. The current rates of production and consumption of electronic devices have made the generation of electronic waste a global concern. Waste printed circuit boards (WPCBs) are the core component of electrical waste. A proper management of WPCBs is crucial from both, an environmental point of view (they contain toxic materials) and an economic point of view since they contain valuable materials such as precious metals (PMs). The heterogeneity in WPCBs composition hampers the effective recovery of the valuable metals contained in WPCBs, making it essential to adopt a combined approach such as the inclusion of a chemical pretreatment to recover the materials that they contain. This work studies the effect of the chemical pretreatment, Fe 2+ and Cl − concentrations on the recovery yield and the kinetics of the leaching of Cu, Au and Ag, during the electrochemical treatment of real WPCBs. This study aims to assess the viability of using waste spent pickling acids (SPAs) from surface treatment industries to recover valuable materials from WPCBs by electrochemical leaching. Two full 2 2 factorial designs were considered: the first design evaluated the effect of Cl − and Fe 2+ concentrations, while the second design studied the effect of the chemical pretreatment and Cl − concentration. A novel in-house leaching system was used. Operating at room temperature with a mildly acidic media (0.05 M H 2 SO 4 ), the system achieved leaching yields up to 99 %, 75 % and 99 % for Cu, Au, and Ag, respectively. These recoveries were reached in less than 150 min for Cu and Ag and less than 60 min for Au. Based on the results, a sequential and environmentally friendly recovery process was proposed to recover separately base and PMs from WPCBs.