Leaching kinetics of waste pharmaceutical blister package aluminium in phosphoric acid media

Abstract

This study investigated the process of treating secondary aluminium recovered from waste pharmaceutical blister packages (WPBs) using phosphoric acid solutions as a potential strategy for recycling this currently non-recycled waste material. The findings indicate that, when recycling via the hydrometallurgical process, the aluminium passivated during leaching can be effectively counteracted by employing moderately concentrated phosphoric acid solutions (1.0 M), elevated temperatures (60–80 °C) and specifically the addition of H2O2 (1.25–2.5 vol.%). Under these conditions, complete extraction of aluminium was achieved within four hours. The estimated activation energy (∼82 kJ/mol) indicates that the leaching reaction is primarily limited by the chemical reaction rate rather than film diffusion. An aluminium phosphate solution could be obtained by leaching WPBs in a way that is suitable for subsequent aluminium phosphate crystallisation. This approach could provide a promising pathway for valorising aluminium from the currently under-utilised waste fraction of pharmaceutical blister packages.