An ultrasonic-assisted process for copper recovery in a des solvent: Leaching and re-deposition

The continuous growth of the electronic equipment market has led to an increased amount of scraping that it bedomes necessary to recover. A hydrometallurgical method for copper and precious metal recovery from e-waste must consist of a number of steps: leaching, ion separation and subsequent electrochemical re-deposition of the target metal. Although this task is achievable in aqueous solutions, it requires strong acid or cyanide solutions. The aim of the study is to develop a new environmentally benign process by using a Deep Eutectic Solvent (DES), a form of cheap and safe ionic liquid, as an electrolyte for both leaching and electrodeposition. The experiments were conducted in a mixture of choline chloride and ethylene glycol, under 20 kHz ultrasonic agitation. In optimized temperature and sonication conditions, the leaching rate of copper attains 65 mg/h cm(2). An interesting feature is that, in this media, copper dissolves into the form of Cu(I) complex instead of Cu(II) complex, so that subsequent electroreduction of copper ions is energetically more favorable. Copper deposits obtained from Cut-DES solution present a sand-rose cluster morphology inducing a large developed surface. Application of ultrasound during electrodeposition allows for grain size reduction and crystallographic texture modifications, compared to silent conditions.