Recovery of metallic concentrations from waste printed circuit boards via reverse floatation

Abstract

Efficient disposal of waste printed circuit boards (PCBs) is favorable toward recovering valuable components and reducing pollution. Reverse floatation was used to recover metallic concentrations from waste PCBs. Basic properties and mineralogical characteristics of raw PCBs were tested and analyzed. Results indicated that the grade of metallic concentrations declined as the size fraction of PCBs decreased. The major metallic elements found in PCBs were Cu, Pb, and Sn, as well as trace elements were also found in fine PCB particles. Kerosene and terpenic oil were used as the collector and frother in the floatation experiments. The effects of various operational factors, including the feeding concentration, aeration rate, and agitation speed of floatation machine, on the floatation performance of −0.25mm PCBs were experimentally studied to determine optimal range. The floatation results suggested that the yield of sinks and grade of metallic concentrations diminished significantly with the decrease of size fraction of PCBs. The maximum yields of sinks and highest grades of metallic concentrations were 48.72% and 16.86%, 47.96% and 14.61%, 44.36% and 8.81%, with the optimum recoveries of metallic concentrations of 94.69%, 90.06%, and 75.96% for size fractions of 0.125–0.25mm, 0.074–0.125mm, and −0.074mm PCBs, respectively. The recovery efficiency of metallic concentrations declined as the size fraction decreased. The efficient overall recovery performance of metallic concentrations from waste PCBs was obtained via reverse floatation. This study provides an alternative approach for disposing waste PCBs.