Activation of peroxydisulfate (PDS) by Bi5O7I@MIL-100(Fe) for catalytic degradation of aqueous doxycycline (DOX) under UV light irradiation: Characteristic, performance and mechanism

A metal-organic framework encapsulated Bi5O7I particles (Bi5O7I@MIL-100(Fe)) was successfully synthesized for activation of peroxydisulfate (PDS) towards aqueous doxycycline (DOX) degradation. The constructed heterojunction between Bi5O7I and MIL-100(Fe) enhanced DOX decontamination via the synergistic coupling photocatalysis with PDS activation. The as-prepared composite BM-3 (B means Bi5O7I, M means MIL-100(Fe), 3 means the mass ratio of Bi5O7I to MIL-100(Fe)) exhibited more outstanding degradation performance for doxycycline (DOX) decomposition (kobs value of 0.0352 M−1 min−1) compared with the individual MIL-100(Fe) (kobs value of 0.0127 M−1 min−1) and Bi5O7I (kobs value of 0.0048 M−1 min−1). Different influencing factors including PDS dosage, initial pH, coexisting anions, organic matter (humic acid (HA)), and water matrixes on the DOX decomposition in the Bi5O7I@MIL-100(Fe)/PDS/UV light system were explored in details. The satisfactory recyclability of BM-3 composite was verified with the DOX removal efficiency maintained as high as 92.4% after five runs in the recycling experiment with the maximal iron leaching of 0.4101 mg/L, suggesting the satisfactory recyclability of the BM-3 composite and insignificant secondary contamination of the established catalytic system. The results of radical quenching test and electron paramagnetic resonance (EPR) analysis revealed active species of •SO4−, •OH, •O2−, h+, e−) were involved in DOX removal. This work was expected to facilitate the design and application for Fe-MOFs-based materials on PDS activation towards enhanced refractory organic pollutant removal.