Intrinsic linkage of double S-scheme heterojunctions based on Fe@Bi₂MoO₆@BiOI construction for photodegradation of tetracyclines: Enhanced antibiotic mineralization and detoxification

This paper presents the design and evaluation of a novel photocatalyst, Fe@Bi₂MoO₆@BiOI, featuring a double S-scheme-type heterojunction aimed at enhancing antibiotic removal and degradation. This innovative configuration promotes a high degree of dispersion of nano-zero-valent iron (NZVI), significantly improving the removal efficiency of antibiotics and the deep mineralization of tetracycline (TC). The optical properties of the NZVI passivation layer were confirmed through characterization techniques, demonstrating energy band structural alignment with Bi₂MoO₆ and BiOI, which facilitated the effective construction of the heterojunction. The phot catalytic efficiency of the Fe@Bi₂MoO₆@BiOI catalyst was measured to be 1.24, 3.93, and 4.61 times greater than that of pure Fe⁰, BiOI, and Bi₂MoO₆, respectively, achieving a mineralization rate of 75.02 %. This impressive catalytic performance is attributed to the reducing properties of Fe⁰ and the generation of key reactive species, including •O₂^-, •OH, and h⁺. Furthermore, through LC-MS analysis, three degradation pathways for TC were elucidated, revealing that the toxicity of the degraded TC solution was significantly reduced, as confirmed by toxicity assessments and biocultivation experiments. This study underscores the potential of NZVI-based dual S-scheme-type heterojunctions for addressing antibiotic contamination and creatively illustrates the heterogeneous photo-Fenton degradation capabilities of these structures. The results highlight the synergistic effect of dual heterojunctions and provide new ideas for future applications in environmental remediation.