New Chemistries for Silver and Lead Recovery from End-of-Life Silicon Solar Modules

Abstract

Two metals contained in silicon solar modules belong to the must-recover category: silver and lead. Silver is the main financial incentive for recyclers generating ~$5/module, while lead is toxic creating a potential environmental hazard when landfilled. The literature on silver recovery often employs nitric acid for leaching followed by precipitation, re-dissolution, and electrowinning to recover metallic silver, while lead recovery has been rarely attempted for silicon module recycling. In this talk we will report silver recovery with hydrofluoric acid. It involves two steps, leaching and electrowinning to recover over 95% of the silver as a pure metal. A two-step process of leaching and electrowinning for lead recovery with acetic acid will also be reported. A recovery rate of over 99% has been confirmed, with the lead content in the post-electrowinning leachate below 10 ppm and the recovered lead being a pure metal. However, the recovered lead tends to react with ambient and acetic acid to form surface oxide and/or acetate due to its dendritic morphology. A dense lead deposit is preferred.