Green disposal of waste smartphone protective film: Efficiency, mechanism, bench-scale test and secondary waste reutilization

The manufacture and obsolescence of smartphones produce numerous waste plastic accessories (e.g., waste smartphone protective film (WSPF)), possessing immense potential for recycling. However, available recycling technologies have limitations such as substrate damage and secondary pollutant generation. The present study aimed to develop a green disposal method that not only recycled polyethylene terephthalate (PET) from WSPF, but also reused the stripped polyacrylate (PAA) adhesive as an adsorbent to reduce solid waste generation. When the WSPF was treated in 1 mol/L NaOH solution at 90 °C, the PAA hydrolyzed to two main by-products of 1-butanol and 2-ethylhexanol, weakening the binding strength between PAA and PET and then efficient separation of them. Further bench-scale test revealed that over 97.2% of detachment efficiency toward PAA was achieved during continuous treatment of 17 batches of WSPF (200 g for each) without supplement of NaOH and generation of wastewater. Meanwhile, the economic evaluation indicated that the recycling method would generate a net profit margin of 647% for the second year without considering the incurrence of new cost and input. Additionally, the pyrolysis of waste PAA enabled its conversion into potential adsorbent, which showed 2 to 4 times enhanced adsorption capacity toward styrene and ethyl acetate after modification with NaOH solution. This study provides a green method for recycling waste plastics and inspires a referable solution for solid waste treatment in the smartphone industry.