Zinc-doped ferrite nanoparticles as magnetic recyclable catalysts for scale-up glycolysis of poly(ethylene terephthalate) wastes

Abstract

Innovations of catalyst design are critical to industrial implementation of poly(ethylene terephthalate) (PET) upcycling by glycolysis. A primary challenge that affects the purity of products and increases the recycling cost is the difficulty in catalyst separation and reusability. Here, magnetically isolable zinc ferrite nanoparticles (Zn-MNPs) were prepared and fabricated for higher catalytic activity in PET glycolysis. Results reveal that the substitution of zinc into the spinel structure of Fe3O4 significantly enhances its catalytic selectivity in PET glycolysis. Besides, the Zn-rich surface and hollow internal structure of the prepared catalysts create more active sites for reactants, relative to pure Fe3O4. Under mild conditions, PET chains experienced a powerful nucleophilic attack from ethylene glycol when catalyzed by Zn-MNPs, achieving 79.82% monomer yield and 100% PET degradation in 2 h with low consumption of ethylene glycol. The recovered catalysts can be reused for five consecutive cycles with high PET conversion. It is anticipated that the synthesized low-cost and recoverable Zn-MNPs are promising alternatives for the industrial upcycling of PET wastes.