Investigation of the degradation and dehalogenation properties of florfenicol by heterogeneous Fenton reaction activated with MIL-53(Al)-supported nano zero-valent iron

Abstract

The antibiotic florfenicol (FF) discharged into the aquatic environment may cause serious water pollution. Therefore, an effective way to eliminate FF antibiotics from the water bodies should be proposed. Herein, MIL-53(Al)-supported nano zero-valent iron (NZVI@MIL-53(Al)) was synthesized and applied to activate hydrogen peroxide (H2O2) to spark the Fenton reaction for FF antibiotics removal. The characterization results demonstrated the successful loading and good dispersion of NZVI onto MIL-53(Al). 100 % FF antibiotics degradation could be achieved under the optimal reaction conditions, including an initial FF antibiotics concentration of 20 mg L−1, initial solution pH of 3.0, NZVI@MIL-53(Al) dose of 25 mg L−1, and H2O2 concentration of 0.2 mM. And after four cycles, the FF antibiotic degradation efficiency was still 81.18 %. The lowest tolerance for HCO3− was observed while the degradation activity was maintained at the presence of Cl− and HA. EPR measurement and free radical quenching experiment showed that ·OH was the main reactive specie in the NZVI@MIL-53(Al)/H2O2 system. FF antibiotics degradation involved hydroxylation reactions (electrophilic substitution), dehalogenation, hydrolysis, and cleavage based on the UPLC-MS/MS analysis and DFT calculation. Noteworthy, 0.247 mg L−1 of F− and 1.2 mg L−1 of Cl− were detected in the solution after the reaction due to the breakage of the stable C–Cl bond and C–F bond. Finally, this work revealed that the NZVI@MIL-53(Al), with high stability and recyclability, could be a potential heterogeneous catalyst for treating antibiotic wastewater.