Near complete silver recovery from end-of-life PV solar cells by continuous froth flotation

Abstract

Building on our previous study, which demonstrated for the first time that froth flotation could selectively recover metallic silver from end-of-life photovoltaic cells, this work investigated the transitioning from batch mechanical flotation to an intensified continuous operation in a Reflux Flotation Cell. Approximately 22 kg of crystalline silicon solar cell material, equivalent to about 468 kg of original rooftop PV panels, was wet ground and fed directly to the single-stage flotation process. AEROPHINE 3418A and AEROFLOAT242 were used as collectors with methyl isobutyl carbinol (MIBC) as the frother. Following an initial transient period, the system reached a hydrodynamic steady state at approximately 42 min, after which the solids yield stabilised at around 1.25 ± 0.024 %. During this steady-state window, the concentrate contained an average silver grade of approximately 48.8 wt ± 1.16 %, corresponding to an 83-fold upgrade relative to the representative feed grade of 0.590 ± 0.006 wt% Ag. Silver was below the ICP-MS limit of reporting (0.001 g/tonne) in all steady-state tailings samples, corresponding to a calculated silver recovery of ∼100 %. These results demonstrate that the high silver recovery previously achieved in the bench flotation can be sustained under continuous operation, while achieving full silver recovery and substantially greater upgrading in a single stage. The findings demonstrated a continuous, highly selective separation route for recovering metallic silver from end-of-life photovoltaic cells.