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Polyethylene terephthalate (PET) can be recovered as high-purity bis(2-hydroxyethyl terephthalate) (BHET) monomer by glycolysis in the presence of Fe3O4 nanoparticles (NPs). In this study, Fe3O4 NPs of various shapes, sizes, and surface areas were synthesized using different colloidal synthesis methods, and the conversion of PET glycolysis and BHET yield were compared. Spinel ferrite NPs, including Fe3O4, were synthesized using the coprecipitation (CP), thermal decomposition (TD), and the hydrothermal (H) methods. Among the NP catalysts, Fe3O4-CP exhibited the best glycolysis performance with a PET conversion of ∼100% and BHET yield of 93.5% at 195 °C for 2 h owing to its high surface area (146.6 m2 g−1). The larger the surface area and the better the dispersion, the higher the glycolysis activity. The glycolysis performance of the mixed spinel ferrite NPs was similar to that of the Fe3O4 NPs, indicating that replacing Fe2+ in the Fe3O4 NPs with other transition metals, M2+, did not significantly change the glycolysis performance. BHET monomers produced from commercial waste PET bottles in large quantities contained trace amounts of metal contaminants, because PET production uses various metal-based additives and catalysts. Amberlite IRC-120, a cation-exchange resin, effectively removed metal impurities from BHET. This study provides an effective strategy for producing recycled PET (r-PET) by waste PET glycolysis. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were produced from waste face masks and non-recyclable mixed plastic waste via pyrolysis-chemical vapor deposition (CVD). The yield and properties of the prepared CNTs depended on the feedstock and catalyst used. CoMo/MgO and FeMo/MgO were proven suitable catalysts for producing few-walled and multi-walled CNTs, respectively, regardless of the feedstock. Both mask waste and the FeMo/MgO catalyst led to excellent carbon yield (516.7 wt%) and CNT purity (97.9 wt%). The resulting CNTs were mixed with LiNi0.8Co0.1Mn0.1O2 (NCM811) active material and poly(vinylidene fluoride) binder to fabricate cathodes. Electrochemical measurements showed that CNTs grown on the FeMo/MgO catalyst outperformed commercial carbon black and CNTs. C1–C3 hydrocarbons and H2 present in the plastic pyrolysis gas can be directly used for CNT production without gas separation or purification, therefore, the proposed pyrolysis-CVD process is favorable for efficient plastic upcycling and advanced battery applications. [ABSTRACT FROM AUTHOR]