Comparative analysis of I-2-KI and HNO3 leaching in a life cycle perspective: Towards sustainable recycling of end-of-life c-Si PV panel

Abstract

An iodine-iodide system was investigated as an alternative lixiviant for HNO3 for leaching precious metals from the end-of-life c-Si photovoltaic (PV) cell. A series of batch experiments were conducted for the optimization of leaching kinetics and thermodynamic equilibrium followed by a life cycle assessment (LCA) using data from the experiments. The results showed that more than 95% of Ag and Al leached out within the first 5 min. The optimum conditions for equilibrium leaching were as follows: solid to liquid ratio of 1:10 for Ag (1:9 ml for Al), and I-2 concentration of 0.35 M for Ag (0.3 M for Al), with I- concentration of 0.7 M. In addition, selective leaching of Ag could also be accomplished by adjusting the reaction pH to 9.6%, and 93% of reproducibility was achieved via the rejuvenation of the exhausted leaching solution, which can benefit the subsequent recovery process. The leaching efficiency of iodine-iodide system was nearly comparable to that of HNO3, and the environmental impacts of the two cycle of continuous process with rejuvenation of the iodine leaching solution can be effectively reduced especially in the acidification & eutrophication, respiratory effect, and mineral extraction categories with subsequent exclusion of the additional neutralization process.