Fe3O4@CQDs/dielectric barrier discharge plasma coupled system for enrofloxacin degradation: efficiency, influencing factors, and synergistic mechanism

• Fe 3 O 4 @CQDs composite exhibits superior photocatalytic performance. • Fe 3 O 4 @CQDs/DBD coupled system shows a synergistic effect. • The coupled system has strong anti-interference against pH, ions, humic acid. • ENR degrades via e⁻, •OH, • O 2 − , 1 O 2 , ONOO⁻, H 2 O 2 , O 3 etc., through defluorination, with less toxic intermediates. The escalating residue of enrofloxacin (ENR) in aquatic environments exacerbates antibiotic resistance, necessitating efficient degradation technologies. Herein, a Fe 3 O 4 @CQDs/dielectric barrier discharge (DBD) plasma system was constructed to degrade ENR, with a focus on unraveling the synergistic mechanism. Fe 3 O 4 @CQDs are synthesized via the hydrothermal method and exhibit enhanced specific surface area, abundant surface functional groups (hydroxyl, carbonyl), and efficient Fe(III)/Fe(II) redox cycling performance. Optimal degradation of ENR was achieved at 20 kV discharge voltage, 0.3 g/L Fe 3 O 4 @CQDs dosage, with a 95% removal efficiency at 30 min and a synergistic factor of 2.66. The system showed robust anti-interference against pH fluctuation, Cl⁻, CO 3 2 − , and humic acid. Degradation intermediates and density functional theory analysis revealed degradation pathways (defluorination, decarboxylation, demethylation) with intermediates of reduced toxicity. •OH, • O 2 − , 1 O 2 , ONOO⁻, H 2 O 2 , and O 3 were confirmed key reactive species with e⁻ as the initiator. The primary synergistic mechanisms of Fe 3 O 4 @CQDs/DBD involve the plasma providing initial energy and active species, while Fe 3 O 4 @CQDs offers active sites. Additionally, Fe(III)/Fe(II) can drive the Fenton reaction for H 2 O 2 generation and the conversion of O 3 to •OH, inhibiting e⁻-h⁺ recombination and enhancing oxidation. Besides, Fe 3 O 4 @CQDs retained 77% activity after 4 cycles. This study highlights the Fe 3 O 4 @CQDs/DBD synergism, offering a sustainable strategy for antibiotic degradation in complex matrices.