Innovative closed-loop copper recovery strategy from waste printed circuit boards through efficient ionic liquid leaching

With the increasingly prominent contradiction between the demand of the metal market and the supply of mine resources, the recovery of the waste printed circuit board (WPCBs) with high-grade metal resources and significant environmental pollution characteristics is of great significance to alleviate the shortage of copper resources and reduce environmental pollution. This study proposes a green closed -loop process for selective regeneration of copper in WPCBs based on clean leaching of ionic liquids (ILs). The copper concentrate particles were first mildly leached using an environmentally friendly ILs-H2O2 leaching system, and the sulfuric acidhydrogen peroxide (H2SO4-H2O2) and glycine-hydrogen peroxide (Gly-H2O2) systems were used as a reference group to verify the high efficiency of the ILs-H2O2 system for leaching. Leaching kinetics was used to analyze the behavior of copper concentrate particles during leaching to clarify the leaching mechanism. The leaching results show that the ILs-H2O2 system achieves efficient leaching of copper, with a maximum leaching rate of 93.56 %, similar to the H2SO4-H2O2 system and slightly better than the Gly-H2O2 system. The internal diffusion control model was able to accurately describe the kinetic characteristics of copper concentrate particles in the ILs-H2O2 system with reaction activation energy of 11.84 kJ/mol. Subsequently, copper was recovered from the leach solution by combining oxalic acid precipitation and pyrolysis to prepare copper oxide nanoparticles, and the morphology and phases of the precipitates and pyrolysis products were analyzed by SEM and XRD. The results show that copper oxide particles of hundreds of nanometers can be successfully produced and the copper oxide nanoparticle aggregates still retain the architecture of the precursor copper oxalate particles. This study aims to reintroduce non-renewable metal resources into the supply chain and provide valuable insights for recycling metals from e -waste.