Evaluation of the Efficiency of Metal Recovery from Printed Circuit Boards using Gravity Processes

This paper evaluates the efficiency of metal recovery from printed circuit boards (PCBs) using two gravity separation devices: a shaking table and a cyclofluid separator. The test results were compared with the results obtained from previous research, where an electrostatic separation process was used for an identically prepared feed. The feed for the separators consisted of PCBs shredded in a knife mill at cryogenic temperatures. The separation efficiency and purity of the products were evaluated based on microscopic analysis, ICP-AES, SEM-EDS, XRD, and specific density. The yield of concentrates (valuable metals) obtained from the shaking table and the cyclofluid separator amounted to 25.7% and 18.9%, respectively. However, the concentrate obtained from the cyclofluid separator was characterised by much higher purity, amounting to ~88% of valuable metals, compared to ~72% for the shaking table. In both cases, middlings formed a significant share, their yield amounting to ~25%, with the share of valuable metals of ~15%. The yield of waste obtained from the shaking table and the cyclofluid separator were 42.6% and 52.5%, respectively. In both cases, as a result of the applied process, the waste was divided into two homogeneous groups differing in grain size and shape. The recovery of metals through gravity separation is possible, in particular, by using a shaking table. These processes can also be applied to separate waste (plastics) into two groups to be selectively processed to produce new materials in line with a circular economy.