Treatment and management of the effluents generated by hydrometallurgical processes applied to End-of-Life Photovoltaic Panels

Abstract

Photovoltaic (PV) technology is a low-carbon and efficient option to produce electricity with an expected growing market. In the next years, end-of-life PV panels (EoL PV) will generate a new type of waste whose management implies environmental concerns but also opportunities to recover secondary raw materials. As part of a European project, a 1,500 panels/year capacity pilot plant to recover valuable resources from EoL PV panels using hydrometallurgical processes was operated in real environment. It represents the first time that a hydrometallurgical treatment was applied, at industrial scale, to EoL PV panels. This study focuses on the specific topic of treating the wastewater generated by the end of the hydrometallurgical process. Different chemical and physical tests were tried in laboratory on such streams loaded with metal species. The experimental results indicated that induced precipitation by adding strong acid or alkaline solutions allows obtaining high metal removal rates (greater than 95%). The optimal pH was around neutrality. Results suggested testing whether mixing the two wastewater at different rates could result in similar decontamination effects. pH neutrality was again the optimal condition. A further test at industrial scale was carried out by using a treatment plant specially assembled for the purpose. The study showed as the approach allowed to: 1) achieve a final supernatant to be reused within the recycling panel process; 2) avoid the use of lab-made high-grade solutions to modify pH; 3) minimize the production of waste (less than 60%) avoiding costs for the final out-side treatment and disposal.