Chemical conditioning for wet magnetic separation of printed circuit board dust using octyl phenol ethoxylate

•Printed circuit board dust generated during comminution for recycling.•Removal of ferromagnetic content by magnetic separation ineffective, wet or dry.•Chemical conditioning of the pulp made wet magnetic separation effective.•A clean physical processing step achieved for the dust.•Reagent addition now a factor in magnetic separation. Magnetic separation of ferromagnetic particles from fine dust recovered from airbag during printed circuit board (PCB) comminution appears quite rational, but under magnetic field, dust particle separation is problematic due to diverse particle morphology, electrostatics, induced magnetism and does not wet. These effects frustrate PCB dust magnetic separation, wet or dry. Chemical conditioning of the PCB dust pulp with octyl phenol ethoxylate (OPE) was conceived to combat these effects by altering the surface tension of water to wet and disperse the dust particles for efficient wet magnetic separation. At optimum OPE concentration used, which gave 56 dynes/cm solution, Fe and Ni recoveries in the 150–212 µm dust, were 97 and 94%, respectively, under wet high intensity magnet (3150 Gauss); these dropped to 92 and 85%, under low intensity magnet (1370 Gauss), but misplacement of paramagnetic elements such as gold, copper reduced from 22% to 5.4% Au and 5.7% to 2.2% Cu. The best Separation Efficiency, considering the major economic elements, is up to 83% in a single roughing step under the low intensity wet magnetic separation. With evolution in PCB dust complex material streams for beneficiation, chemical conditioning has appeared as a vital factor to make wet magnetic separation effective.