• $ \mathrm{CO}_{2}^{·-}$ can universally degrade and dehalogenate halogenated antibiotics;

• The chlorine moiety of FF was more susceptible to the nucleophilic attack of $ \mathrm{CO}_{2}^{·-}$;

• pH, inorganic anions and humic acid exhibited neglectable effect on FF degradation.

高级氧化技术（advanced oxidation processes，AOPs）在水处理领域已被广泛用于降解各类新污染物，但由于含卤官能团在氧化环境中具有很强的反应惰性，限制了AOPs对卤代抗生素的脱卤和毒性削减效果。为克服上述缺陷，本研究以氟苯尼考（florfenicol，FF）为代表性污染物，利用二氧化碳自由基（carbon dioxide radical anions，CO₂^·-）为主导的高级还原技术（advanced reduction processes，ARPs），实现了卤代抗生素的同步降解、脱卤和毒性削减。结果表明：在CO₂^·-体系中FF实现了完全降解和高效脱卤，120 min内脱氯和脱氟效率分别达到了100%和46%；同时FF的毒性削减效果和脱卤效率呈线性负相关（R²=0.97，p<0.01）。与羟基自由基（hydroxyl radical，•OH）体系相比，无卤产物生成是CO₂^·-体系具有更好毒性削减效果的主要原因。产物鉴定和密度泛函理论（density functional theory，DFT）计算结果表明，FF的含氯官能团比其他官能团更容易受到CO₂^·-的亲核进攻，进而诱导后续脱卤过程。除FF外，CO₂^·-体系对包括氯霉素（CAP）、甲砜霉素（THA）、双氯芬酸（DLF）、三氯生（TCS）和环丙沙星（CIP）在内的多种卤代抗生素均表现出良好脱卤效果（>75%）。该体系不仅对天然水体组分和溶液pH具有良好的耐受性，而且在实际地下水中具有卓越的降解性能，证明CO₂^·-体系具有很强的应用潜力。本研究阐明了CO₂^·-用于卤代抗生素同步降解、脱卤和毒性削减的可行性。

Despite the extensive application of advanced oxidation processes (AOPs) in water treatment, the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors. Halogen moieties exhibit strong resistance to oxidative radicals, affecting the dehalogenation and detoxification efficiencies. To address these limitations of AOPs, advanced reduction processes (ARPs) have been proposed. Herein, a novel nucleophilic reductant—namely, the carbon dioxide radical anion ($\mathrm{CO}_{2}^{·-}$) —is introduced for the simultaneous degradation, dehalogenation, and detoxification of florfenicol (FF), a typical halogenated antibiotic. The results demonstrate that FF is completely eliminated by $ \mathrm{CO}_{2}^{·-}$, with approximately 100% of Cl⁻ and 46% of F⁻ released after 120 min of treatment. Simultaneous detoxification is observed, which exhibits a linear response to the release of free inorganic halogen ions (R² = 0.97, p < 0.01). The formation of halogen-free products is the primary reason for the superior detoxification performance of this method, in comparison with conventional hydroxyl-radical-based AOPs. Products identification and density functional theory (DFT) calculations reveal the underlying dehalogenation mechanism, in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by $ \mathrm{CO}_{2}^{·-}$. Moreover, $ \mathrm{CO}_{2}^{·-}$- based ARPs exhibit superior dehalogenation efficiencies (> 75%) in degrading a series of halogenated antibiotics, including chloramphenicol (CAP), thiamphenicol (THA), diclofenac (DLF), triclosan (TCS), and ciprofloxacin (CIP). The system shows high tolerance to the pH of the solution and the presence of natural water constituents, and demonstrates an excellent degradation performance in actual groundwater, indicating the strong application potential of $ \mathrm{CO}_{2}^{·-}$-based ARPs in real life. Overall, this study elucidates the feasibility of $ \mathrm{CO}_{2}^{·-}$ for the simultaneous degradation, dehalogenation, and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.