A Critical Review of Leaching Pathways for Silver Recovery from EoL Photovoltaic Modules and Prospects for Flotation

Rising global demand for silver, driven by electrification, is prompting concerns over long-term supply. End of life (EoL) photovoltaic (PV) panels represent a promising secondary source of silver, containing 300 to 500 ppm, comparable to high-grade primary silver-bearing ore deposits. With more than 60 million tonnes of decommissioned PV panels expected globally by 2050, effective recycling presents both an environmental imperative and a valuable opportunity for silver recovery. This review critically evaluates current silver recovery methods, which predominantly rely on acid leaching. While leaching is proven and can achieve high recoveries, it is inherently chemically intensive and environmentally burdensome. To identify key limitations in prevailing approaches, we provide a systematic review of leaching studies focused on the influence of experimental parameters such as lixiviant composition and concentration, solid-to-liquid ratio, feed particle size, temperature, and agitation on silver recovery performance. While silver recovery is often mentioned in broader reviews of EoL PV recycling, no prior study has examined silver recovery in depth or explored alternative approaches inspired by conventional mineral processing. In response to these limitations, this paper considers for the first time the role of physical separation techniques, specifically froth flotation as a silver pre-concentration step grounded in conventional mineral processing and beneficiation. Although no studies have yet applied flotation to silver recovery from EoL PV, evidence from analogous secondary resources demonstrates its potential to upgrade silver-bearing fractions. By concentrating the feed, flotation could materially reduce reactor volume, acid consumption, and effluent generation while preserving overall recovery. Furthermore, we highlight emerging alternative methodologies such as the use of deep eutectic solvents, which offer promising improvements over aggressive acid-based leaching systems. Combined with flotation, such greener lixiviants offer opportunities for more sustainable recycling of silver from EoL PV.