Copper recovery from waste printed circuit boards with small peptides enhanced by ultrasound

Waste printed circuit boards (WPCBs) are one of the most critical and valuable components in electronic equipment. WPCBs contain many metals (Cu accounts for more than 90%), which are a potential secondary resource to overcome metal scarcity. The recovery of metals from WPCBs is significant for environmental pro-tection and resource reuse. This investigation presents a simple and sustainable approach to leach Cu from WPCBs with small peptides enhanced by ultrasound. Various leaching parameters, including initial small pep-tides concentration, temperature and initial H2O2 volume fraction have a highly significant influence. The maximum Cu leaching were 95.4 +/- 0.1%, 92.5 +/- 0.1% and 87.4 +/- 0.1% by glutathione (GSH), glycylglycine (GG), and glycyl-L-glutamine (GLG), which caused by the differences of small peptides functional groups. The Cu leaching by ultrasound exhibited 2.1-3.9 folds higher than without ultrasound treatment. The kinetic analysis showed that the Cu leaching from WPCBs was mainly controlled by diffusion and chemical reactions. The co-ordination numbers of copper-chelating GSH (CC-GSH), copper-chelating GG (CC-GG), and copper-chelating GLG (CC-GLG) were measured by simulation experiments. The hydroxyl, carboxyl, amino and sulfhydryl groups are the main reasons for the complexation of small peptides and Cu2+, which was confirmed by the characterization of copper-chelating small peptides (CCPs) crystal. The Cu leaching with small peptides enhanced by ultrasound potentially represents an innovative technology with significant advantages in metals extraction and time effi-ciency. Furthermore, the results provide perspectives and new insights into the preparation of CCPs and the industrial application of modified leaching residues.