Efficient recovery of valuable metals from waste printed circuit boards via ultrasound-enhanced flotation

Abstract

Due to the environmental hazard of waste printed circuit boards (WPCBs), there is an urgent need to develop efficient recycling technology of useful metal elements in WPCBs and to promote the efficient use of WPCBs. Therefore, we tried to intensify the efficient recovery of metal elements from WPCBs by introducing ultrasound into the flotation process. Scanning electron microscope (SEM) observation and laser particle size analysis confirmed that ultrasonic treatment was conducive to removing the epoxy resin and fine metal particles on the surface of glass fibers and promoting particle dispersion, which significantly improved metal recovery. In addition, wettability analysis demonstrated that the enhanced hydrophobicity of the non-metallic components caused by ultrasonic treatment improved the flotation performance of non-metallic components, thereby strengthening the reverse flotation separation efficiency of the metal components and the non-metallic components. Consequently, compared with traditional flotation, ultrasonic-enhanced flotation promoted the significant increase of total metal recovery and Cu, Al and Zn recovery from WPCBs, in which the total metal recovery and Cu, Al and Zn recovery from WPCBs increased by 7.20%, 4.82%, 15.41% and 5.58%, respectively. Based on this, our findings will provide an important guide for efficiently recovering valuable metal elements from WPCBs.