Recovery of high-grade copper from waste printed circuit boards by mechanical-grinding assisted flotation

Abstract

Mechanical grinding combined flotation technology with renewable collector has been proposed to recover high-grade copper from waste printed circuit boards (WPCBs). Surface morphology and element distribution of copper particle section were analyzed using scanning electron microscopy and energy dispersive spectrometry (SEM + EDS) technology. Results show that the copper particle is covered with a layer of micrometer-scale organic matter. Thermogravimetric analysis demonstrates the organic layer commonly existed on all of the particle surfaces, which prove that the pyrolysis method was not feasible for selectively removing the organic impurity. Mechanical grinding pretreatment was proposed to peel off the organic layer. Grinding experiment results show that impurity can be effectively separated from copper. Soap collector prepared from waste oil was used for flotation. The flotation results show that the copper grade of the concentrate first increased and then decreased with the increase of the grinding time, while the recovery gradually decreased from 78.7% to 21.7%. Concentrate with 79.1% copper grade and 71.5% recovery was obtained when the grinding time was 3 min. This study provides a physical approach to recover high-grade copper from WPCBs.