Synergistically piezocatalytic and Fenton-like activation of H2O2 by a ferroelectric Bi12(Bi0.5Fe0.5)O19.5 catalyst to boost degradation of polyethylene terephthalate microplastic (PET-MPs)

Pollution of microplastics (MPs) has been drastically threating human health, however, whose elimination from the environment by current approaches is inefficient due to their high molecular weight, stronghydrophobicity and stable covalent bonds. Herein, we report a novel and highly-efficient route to degrade MPs contaminants through synergistically piezocatalytic and Fenton-like activation of H₂O₂ by a ferroelectric Bi₁₂(Bi_0.5Fe_0.5)O_19.5 catalyst under ultrasound treatment. For 10 g/L polyethylene terephthalate microplastics (PET-MPs), the synergistic strategy reached a 28.9 % removal rate in 72 h, which is greatly enhanced in comparison to the individual piezocatalysis and Fenton (Fenton-like) activation. By optimizing the types of oxidants (H₂O₂, peroxymonosulfate and peroxydisulfate) and bismuth ferrite catalysts (non-piezoelectric Bi₂Fe₄O₉ and piezoelectric BiFeO₃/Bi₁₂(Bi_0.5Fe_0.5)O_19.5), it was revealed that H₂O₂ is the best oxidant, and the piezoelectric Bi₁₂(Bi_0.5Fe_0.5)O_19.5 with a high aspect-ratio morphology showed higher activity than the Bi₂Fe₄O₉ and BiFeO₃. The catalyst dosage and H₂O₂ concentration were further optimized, and the good durability of the catalyst was also demonstrated through multiple uses. Different characterization technologies demonstrated the occurrence of PET-MPs oxidation and fragmentation during the treatment process. The plausible mechanism of synergistically piezocatalytic and Fenton-like H₂O₂ activation was proposed based on measurements of band structure, piezoelectric property and reactive oxygen species generation. Finally, we detected the intermediates and determined a possible degradation route of PET-MPs. The toxicity assessment indicated that the produced intermediates have low toxicity and potential risks to the environment.