Effect of operational parameters on the leaching efficiency and recovery of heavy metals from computer printed circuit boards

BACKGROUND Electronic waste (e‐waste) is a recent environmental problem worldwide, because it is bulky in size causing solid waste disposal problems, especially due to the release of heavy metals into the environment. On the other hand, metal scarcity is another global issue with e‐waste, making it a prominent candidate for metal recovery. RESULTS Desktop computer printed circuit boards ( PCBs ) were evaluated as a potential source of Cu, Ni and Zn recovery using a bio‐hydrometallurgical method. The process parameters for metal leaching i.e. different particle sizes, leaching agents, contact time, liquid to solid (L/S) ratio, and agitation speed were evaluated in batch systems. At the following optimal conditions of 1 mol L −1 HNO 3 , L/S ratio of 20 with 200 rpm agitation speed using 0.5–1.0 mm particle size, the concentrations of Cu, Ni and Zn leached out from the PCBs were 450, 8 and 4 mg g −1 PCBs , respectively. Continuous leaching in an up‐flow leaching column using the optimized parameters, coupled to sulfide precipitation yielded > 90% Cu recovery (0.48 g g −1 PCBs ). CONCLUSION PCBs are a good candidate for metal recovery, especially Cu. This can be achieved by combining chemical leaching and biogenic sulfide precipitation techniques.