Dual Fe³⁺/Fe²⁺ redox cycles boost H₂O₂ activation and enhance photooxidation behavior for degradation of tetracycline pollutants

In this study, novel Z-scheme α-Fe₂O₃/CoFe₂O₄ hybrids were used as heterogeneous photo-Fenton-like catalysts to degrade tetracycline (TC) in water through a facile ultrasonic-heating method. The prepared composition, morphology, structure, photoelectric property, and catalytic performance of the samples were investigated. α-Fe₂O₃/CoFe₂O₄/H₂O₂ system degraded 82% of TC within 7 min, which was approximately 1.24 and 1.17 times higher than those of α-Fe₂O₃/H₂O₂ and CoFe₂O₄/H₂O₂ systems, respectively. Scavenging experiments accompanied by ESR measurements revealed that ⋅O₂⁻, ⋅OH, and h⁺ are active species involved in the degradation of TC by α-Fe₂O₃/CoFe₂O₄/H₂O₂ system. In particular, ⋅OH and ⋅O₂⁻ played significant roles, with ⋅OH being the dominant active oxygen substance in the photo-Fenton-like catalytic process. Based on the experimental result, a possible synergetic effect mechanism comprising a Z-scheme heterostructure and dual Fe³⁺/Fe²⁺ in situ redox cycles for H₂O₂ activation was proposed. Hence, this work is an environmentally favorable photo-Fenton-like catalytic system, which will address the environmental issues arising from antibiotics and facilitate sustainable development.