Kinetic characteristics and mechanism of copper leaching from waste printed circuit boards by environmental friendly leaching system

Abstract

Copper is one of the most important valuable elements in waste printed circuit boards (WPCBs), which can be finally recovered by hydrometallurgy. Environmentally-friendly copper leaching technology has become critical. In this study, two environmentally friendly leaching systems, namely ammonia-ammonium chloride leaching system and glycine-hydrogen peroxide leaching system, on copper leaching behavior was concerned, the influence of leaching time and leaching agent concentration on leaching rate of copper concentrate with different size was revealed. In addition, a simple but effective leaching kinetics model were proposed. The results show that with the extension of time, the leaching rate increases rapidly at first (0–10 min) and then slowly (10–25 min) until stable. The optimum leaching concentration of ammonia is 3 mol/L. For ammonia leaching system, the leaching rate increased from 76.92% to 90.05% with the decrease of particle size. Meanwhile, the leaching rate increased from 77.32% to 87.93% in the glycine leaching system. Finer particles have a larger contact area, resulting in higher leaching rates. The simple leaching kinetics model proposed in this study can accurately describe the leaching process of copper. These two environmentally friendly leaching systems can be used as substitutes for traditional inorganic acids.