Recovery of valuable metals from WPCB fines by centrifugal gravity separation and froth flotation

This paper reports physical and physicochemical routes for the recycling of gold, silver, and copper from waste printed circuit boards (WPCBs). The results of optical micrographs indicated that the metals and waste matrix are substantially separated from the slot after the comminution process. The effects of various operational factors, including gravitational force and fluidization water, of centrifugal separators on the separation performance of WPCB fines were experimentally studied. A heavy fraction assaying 363 g/t Au, 381 g/t Ag, and 40.1% Cu was obtained with the recovery of 95.6%, 81.7%, and 96.0%, respectively, using the Knelson concentrator. Different operational factors, the pH value of pulp and the particle size, on the flotation performance of WPCBs powder were examined. The production of stable foams resulted from the natural hydrophobic response of plastics and a sunken product with 472 g/t Au, 537 g/t Ag, and 52.7% Cu was successfully produced with the recovery of 93.4% Au, 84.3% Ag, and 95.8% Cu at natural pH using 50 g/t methyl isobutyl carbinol (MIBC) as the frother. In general, the concentration of valuable metals from WPCB fines was provided using a simple and eco-friendly enrichment technique before the final chemical process.