Leaching of Gold from the Waste Mobile P

The rapid growth in the use of electronic equipments, combined with early obsolescence, has contributed enormously to the generation of a large quantity of electronic (e) waste. One such e-waste, the mobile phone printed circuit boards (PCBs), contain various precious metals that can be extracted by different hydrometallurgical routes. This study investigates the recovery of gold using ammonium thiosulfate as a leaching agent from waste mobile PCBs containing Au, Ag, Cu, Ca, Al, Sn, Fe, Zn, and Pb. The cutting granules of 0.5 - 3.0 mm PCBs were used for leaching in a 500 mL glass beaker in open atmosphere. Various parameters such as ammonium thiosulfate concentration, copper sulfate concentration, pH, and pulp density were studied. An optimal leaching of 56.79% gold was achieved under conditions of 0.1M ammonium thiosulfate, 40 mM copper sulfate, a pH of 10-10.5, and a pulp density of 10 g/L at room temperature with a stirring speed of 250 rpm over 8 hours. The maximum leaching of gold was attributed to the stability of ammonium thiosulfate, with complete PCBs scrap yielding a maximum leaching of 78.8% gold under the same optimized conditions.