Recovery of precious metals from mobile phone waste: Studies on leaching and adsorption by functionalized activated carbon

In today's world, the utilization of electronic devices, particularly mobile phones, has seen a remarkable surge and they are a valuable source of recovery of precious metals. The current study reports on the physical and chemical processing of mobile phone waste into leachate, followed by recovery of precious metals, using ionic liquid functionalized activated carbon (ACF). The recovery process was explored both in batch and column study. The presence of base metals in the final leachate was minimized by employing multi-stage chemical leaching, leading to a more efficient purification process. Moreover, adjustment of HCl concentration in the leachate leads to decreased in other metals interference during adsorption. Following the batch adsorption results, a favorable interaction between IL and metal complexes leads to a quantitative adsorption of the precious metals. In addition, ACF also gave an excellent performance in the column adsorption process with the high bed depth and low flow rate of the leachate as the influential parameter. An increase in the bed depth and a decrease in leachate flow rate proportionally increases the values of k_Th (rate constant), q_e (adsorption capacity), and K_YN (rate constant) and positively increases the 50% breakthrough time (τ). Moreover, the final purification of the adsorbed metals was performed selectively through sequential desorption, employing Na₂S₂O₃, NH₄SCN, and HNO₃ solutions. Finally, the adsorption capability of ACF shown a negligible change after five repetitive adsorption-desorption cycles. Thus, the current study presents a method to process mobile phone waste and selectively recover the precious metals from the leachate.