Superfine copper powders recycled from concentrated metal scraps of waste printed circuit boards by slurry electrolysis

Printed circuit board is an essential part of almost all electrical and electronic equipment (EEE). As the rapid increase of waste EEE (WEEE), caused by the shorter and shorter life span and the accelerated innovation of information communication technologies, waste printed circuit boards (WPCBs) is being a hot issue due to its characteristics of resource abundant but hazardous. In this research, the concentrated metal scraps, obtained by WPCBs mechanical separating, were directly recycled to superfine copper powders by slurry electrolysis. And the effect of polyvinyl pyrrolidone (PVP), oleic acid and H2SO4 concentration, current density and electrolysis time on the purity and particle size of copper powders were discussed in detail. Results showed that all these factors could intensively impact the obtained copper particle size, which became finer as the increase of current density and coarser with the extension of time. Copper powder purity first increased and then decreased as the increase of PVP, oleic acid and H2SO4 concentration. The purity of copper can reach to 99.3% with a particle size of 7.142 μm under the optimum conditions: 30 g/L CuSO4·5H2O, 60 g/L NaCl, 150 g/L H2SO4, 30 g/L PVP, 6 mL/L oleic acid, 80 mA/cm2 for 4 h. XRD analysis indicated that copper was the main phase; SEM and TEM analysis showed that the obtained copper powders were dendritic single crystal coated by a layer of PVP and oleic acid. Therefore, slurry electrolysis could be a perspective approach for WPCBs recycling.