Green solvents in recovery of aluminium and plastic from waste pharmaceutical blister packaging

Pharmaceutical blister packages usually comprise of aluminium and plastic layers. Due to their multi-material structure, the discarded packages are typically landfilled, although when separated, both metallic and polymeric fractions would be recyclable. In the present study, separation of aluminium and polymeric layers of waste pharmaceutical blisters was conducted by exploitation of deep eutectic solvent (DES, lactic acid - choline chloride) and pure lactic acid, both of which are considered green solvents. The separation of aluminium and plastic was investigated at different temperatures, solvent concentrations, solid-liquid ratios and agitation speeds. The complete separation was achieved with both studied solvents. The fastest separation was obtained when temperature was increased, more solvent with respect to solid was used and when agitation was introduced to the system. The effect of solvent concentration varied depending on the used solvent. Separation by lactic acid was the fastest with pure solvent (90 wt%), and separation by DES was the fastest with diluted solvent (50 wt%) due to strong dissolution of aluminium and formation of aluminium lactate precipitate. Polyvinyl chloride (PVC) and acrylic based adhesive were detected in all the investigated samples. After the separation by pure DES, the recovered aluminium fraction was corroded, containing 65 wt% of aluminium and 23 wt% of oxygen whereas after lactic acid treatment, aluminium surfaces contained at its best about 95% of aluminium (aluminium foil contains 96% of Al). The results showed that the DES used and lactic acid can offer viable green separation methodology for aluminium and plastic from blister packages.