Effect of dissociation size on flotation behavior of waste printed circuit boards

Flotation is an effective method for recovering metals from dissociated waste printed circuit boards (WPCBs). The difference in dissociation and flotation behaviors of various size particles are revealed in this study. The metal and impurity in 3–1 mm particles were first dissociated under the impact force. The particle morphology of each size particle in the grinding products was analyzed by scanning electron microscope (SEM). SEM results show that the metal particles presents flake shape, and the dissociated glass fiber shows rod shape. The size composition and element distribution appear bimodal distribution. Flotation results present that the distribution rate of particles in floats increases with the decrease of particle size, and increases with the increase of collector dosage. In addition, the removal rate of Si and Cu reveals the same trend. The finer particles are more sensitive to the change of collector dosage. The removal rates of Si in 1–0.25, 0.25–0.074 and −0.074 mm reaches 59.80%, 95.69% and 95.59% with 4 kg/t collector. Under the action of the collector, the floatability of Cu particles with organic matter adhered to the surface is enhanced, which results in the higher impurity removal and Cu loss.