Ultrasound-assisted synthesis of a novel type-II Bi12O15Cl6/CTF-1 heterojunction for visible-light-driven photocatalytic degradation of levofloxacin: Reaction kinetics, degradation pathways, and toxicity assessment

Fluoroquinolones (FQL) are ubiquitous in aquatic environments due to their widespread use, posing a serious environmental threat. In this regard, a novel Bi₁₂O₁₅Cl₆/CTF-1 (BTF) photocatalyst was prepared by integrating a covalent triazine framework (CTF-1) with Bi₁₂O₁₅Cl₆ by a simple wet-impregnation method for removing levofloxacin (LFX), an FQL-based antibiotic, from an aqueous solution. Under optimal conditions, BTF (III) (comprising 20 % CTF-1) showed the highest photocatalytic activity, achieving approximately 94 % LFX (10 mg/L) degradation in 120 min under visible light with a pseudo-kinetic rate constant of 0.02072 min⁻¹. This can be attributed to the reduced recombination rate and efficient transfer and separation of photoinduced charge carriers. The photocatalyst demonstrated remarkable stability and reusability. The radical trapping experiment revealed $O_2^{•-}$ and h⁺ to be the primary active species facilitating the photocatalytic degradation of LFX. Furthermore, the seed germination test affirmed treated effluent to be non-phytotoxic and suitable for irrigation.