Efficient leaching and recovery of metallic gold and copper from integrated circuits with the novel bromotrihalide ionic liquids based on the redox mechanism

Abstract

In order to develop a safe, closed-loop and eco-friendly process for high efficiency leaching and recovery Au and Cu from integrated circuits (ICs), bromotrihalide ionic liquids (ILs) were synthesized as the perfect substitutes for corrosive or toxic leaching agents. Notably, bromotrihalide ILs showed excellent satisfied thermostability, low viscosity and low water solubility traits in green recovery of metallic Au and Cu. The leaching behavior was explored by studying experimental factors, including solid-to-liquid ratio, temperature and leaching methods. In addition, the corresponding kinetics models were established. It was noteworthy that the maximum Au leaching efficiency of 94.6% and that of Cu 100% were reached in the optimal conditions (20 g/L, 45 °C). It suggested that the leaching process of Au was co-controlled by chemical reaction and diffusion, with a corresponding activation energy of 37.4 kJ/mol. For revealing the redox leaching mechanism, XPS, UV–Vis, SEM, EDS-mapping and ICP spectrometry were conducted, and the leaching pathways of Au were triumphantly investigated via DFT-computed transition state energy barrier and ADCH charge. At last, Au nanoparticles and Cu(II) solution were obtained by selective stripping of Au and Cu. And the recovery efficiencies of Au and Cu were 94.6% and 100%. This work suggests a promising approach to recover the Au and Cu from ICs.