Bioleaching process is recommended for the recovery of metals from electronic waste (E-waste) due to its environment-friendly nature and a rich source of metals present in the E-waste. Each gram of cell phone printed circuit boards (PCBs) powder used in the study contained 275.5, 17.85 and 19.55 mg copper, zinc and nickel as major metal constituents respectively. The chemical leaching by mixture of ferric sulphate and ferrous sulphate (70:30) at 100 g L−1 pulp density was best for copper leaching among the studied systems in which after 4 d of reaction time, 2740 mg copper was solubilized from cell phone PCB powder, while ferric sulphate alone was best for zinc and nickel solubilisation, in which 88 mg zinc and 135 mg nickel were solubilised after 4 d and 7 d of reaction time, respectively. Bioleaching study showed that with acidophilic iron oxidizers, pH 1.8 and initial ferrous concentration 9 g L−1 were optimum for Cu–Zn–Ni extraction from discarded cell phone PCB powder. Cu–Zn–Ni extractions from 10 g L−1 cell phone PCB powder pulp density by the metabolites of iron-oxidizing consortium were 275, 5 and 11 mg, while at 50 and 100 g L−1 pulp density, extractions were 1350, 18 and 53 mg, and 2640, 25 and 100 mg, respectively. The process can be further scaled-up for higher pulp density.
Khatri, B. R., Sodha, A. B., Shah, M. B., Tipre, D. R., & Dave, S. R. (2018). Chemical and microbial leaching of base metals from obsolete cell-phone printed circuit boards. Sustainable Environment Research, 28(6), 333–339. https://doi.org/10.1016/j.serj.2018.10.002