Recovery of high purity copper from waste printed circuit boards of mobile phones by slurry electrolysis with ammonia-ammonium system

Waste printed circuit boards (WPCBs) are identified to be the most complex recycling materials among waste electrical and electronic equipment (WEEE). Slurry electrolysis with acidic system can directly separate and recover copper from WPCBs while current efficiency and purity were generally reduced due to deposition of impurity metals and the hydrogen evolution during recovery process. In ammonia-based system, copper can be selectively extracted and copper (II) ammine complexes generally react with metallic copper to form copper (I) ammine complexes, promoting current efficiency and purity. Therefore, an efficient ammonia-ammonium carbonate slurry electrolysis system is proposed for high purity copper recycling from waste printed circuit boards of mobile phones (WPCB-MPs). The factors affecting copper current efficiency and recovery rate are systematically discussed. These results indicate that appropriate increasing NH3·H2O, (NH4)2CO3, Cu2+, NaCl concentration, solid-to-liquid ratio, current density and reaction time could effectively increase copper recovery rate and current efficiency. The current efficiency and recovery rate of copper are 95.2 and 90.4%, respectively under the optimum test conditions of 20 g/L Cu2+, 0.25 mol/L (NH4)2CO3, 4 mol/L NH3·H2O, 30 g/L solid-to-liquid ratio, 1 mol/L NaCl, 20 mA/cm2, 3 h. Moreover, copper could be recovered at the cathode with a purity of 99.97%. Compared with acidic system, this study provides an efficient approach to recover high purity copper from WPCB-MPs, showing a prospective future for WEEE resource recycling.