Silver recovery from chemical extract originating from End-of-Life photovoltaic panels using a Microbial Fuel Cell

Abstract

The solar energy sector has grown rapidly in the past decades, addressing the issues of energy security and climate change. Many photovoltaic panels that were installed during this technological revolution, have accumulated as waste and even more are nearing their End-of-Life (EoL). Based on circular economy, a new hydrometallurgical process has been proposed for the management of the EoL PVs. This results in a chemical extract containing 0.7 % w/w Ag, along with various other metals. This study investigates the cell power generation and the kinetics of the silver recovery, along with the parasitic removal of other heavy metals, both from synthetic and the real chemical extract in the cathode of a Microbial Fuel Cell (MFC). The results indicated that silver was completely recovered from the synthetic and the real chemical extract, with a rate of ~82 μmol/h and ~32 μmol/h, respectively. The difference is attributed to the simultaneous reduction of other heavy metals in amorphous compounds, hindering the silver reduction kinetics and leading to a gradual electrode passivation. Nevertheless, silver can be 100% retrieved from the chemical extract, with a purity of 68-96% w/w (average 86% w/w at the end of the batch cycle), in crystal (face center cube) structure, containing minor metal impurities.