Multi-Metal Mining from Waste Cell Phone Printed Circuit Boards using Lixiviant Produced by a Consortium of Acidophilic Iron Oxidizers

Abstract

Recently electronic waste (e-waste) includes the fastest growing waste stream in the world. Nevertheless, it also contains about 40 different elements of the periodic table; hence it is a significant metal source. Generally, e-waste recycling is done by the pyrometallurgy and/or hydrometallurgy method. However, the use of microorganisms in hydrometallurgy called bioleaching is a good alternative for eco-friendly and cost-effective recycling of e-waste and recover metals. Leptospirillum-dominated consortium was used to generate ferric iron lixiviant by oxidizing ferrous iron. The resulting lixiviant was used for bioleaching of metals from waste cell phone printed circuit boards (WPCBs). The pretreatment of pulverized WPCB (p-WPCB) and unpulverized WPCB (up-WPCB) was done using 2 M NaOH to see the effect of pretreatment on metal extraction. Moreover, the effect of maintenance of pH of the system was also checked. The controlling of pH of the system to 2.0 ± 0.1 showed enhancement of Cu, Zn, and Ni solubilization. The highest solubilization of copper was 96.86%, which was achieved with pretreated up-WPCB; zinc was 90.69% with pretreated p-WPCB, whereas nickel was 93.65% with untreated up-WPCB. Ours is the first report for extraction of copper, zinc, and nickel from unpulverized mobile phone WPCBs at high pulp density. The solubilization of metals achieved with 100 g/L pulp density provides a promising indication to scale up the process.