An innovative and eco-friendly approach to recover gold (and copper) from gold fingers of waste printed circuit boards

Recycling waste printed circuit boards (WPCBs) is a complex problem worldwide and sustainable technologies are required. So, this work aims to offer an innovative (an European patent was submitted, EP 20216239.2 1) and more sustainable solution to recover high-value materials (gold and copper) from WPCBs. The proposed process includes the following steps: (i) cutting the WPCBs´connecting terminals containing gold fingers using a mechanical tool (such as, a guillotine), (ii) swelling the cut WPCBs pieces (60 mm2) in an appropriate organic solvent inside a low-pressure reactor (with stirring and temperature control), (iii) recovering the gold fingers from a mixture of copper foils and fiberglass using a magnetic separation process followed by sieving. Subsequently, gold and copper were purified from the gold fingers using microwave-assisted acid leaching with nitric acid to leach copper. This process allowed recovering gold, as a solid, with high yield (99.9 wt%) and a purity grade of 74.0 wt%. Finally, leached copper was recovered by alkaline precipitation (pH around 8.8), as a solid of copper hydroxide, with high yield (99.9 wt%) and a purity grade of 85.7 wt%. The present method has the advantages to provide an innovative and smart solution that minimizes the generation of wastes (dusts and wastewaters), energy consumption and equipment´s.