A novel flowsheet for the recovery of metal values from waste printed circuit boards

Abstract

Recovery of metal values from waste printed circuit boards using physical beneficiation techniques was studied. A novel flowsheet using a combination of wet and dry unit operations was developed to achieve the separation of metals from non-metallic constituents. The wet concentration circuit consisted of flowing film concentration in tabling, flotation of plastics and enhanced gravity separation in multi-gravity separator. The dry purification circuit consisted of electrodynamic and electrostatic separation. Substantial enrichment of the ground powder with good recovery of metals was achieved using the flowsheet. The starting PCB powder, ground to −0.5 mm size, had about 23% total metal. Complete liberation of metals from plastics was achieved below 100 μm size. Metal values were found to be more abundant in the coarser sizes. A concentrate grade of over 93% total metal at a recovery of over 54% or a grade of 66% total metal at 95% recovery could be achieved using this flowsheet. Recovery of small and flat metal pieces was problematic in conventional gravity separation. Using gravity separation as a pre-concentration operation followed by flotation and enhanced gravity separation, these problems could be solved to a great extent and good recoveries could be achieved. The circuit has great potential to recover metal values from waste printed circuit boards in an industrial scale.