Investigation of the charging process for non-conductive particles using a novel triboelectric charger

The triboelectric charging of non-conductive particles poses a substantial challenge for the development of electrostatic separation technologies with applications to waste plastics recycling. The present study aims at evaluating the effectiveness of a novel multi-spiral-type triboelectric charger for processing plastic particles derived from waste electrical and electronic equipment (WEEE). The experiments were conducted with 10 g granular samples of high-density polyethylene (HDPE), polycarbonate (PC), and polystyrene (PS), in sizes ranging from 2 mm to 4 mm. The global charge acquired by each sample was measured by collecting the granules in a Faraday pail at the exit of the tribocharger, operated at different frequencies of the electromagnetic vibratory device to which it is associated. In a distinct set of experiments, the tribocharged granules were transferred in the electric field of a free-fall electrostatic separator and collected in 9 distinct compartments. The charge and the mass of the granules collected in each compartment were then measured. Charge per mass ratios exceeding −6 nC/g were achieved for PS and HDPE particles, while a ratio of 5.5 nC/g was obtained for PC. The obtained results not only assess the efficiency of the new charger but also provide a deeper understanding of the tribocharging process, thus contributing to advancing electrostatic separation technology for plastic waste recycling.