Sonocatalytic degradation of furazolidone using a heterogeneous triple ion synergy system of ZnFe₂O₄@ZIF-67 nanostructures: Physicochemical Characterization and degradation pathway

Heterogeneous sonocatalysis coupled with peroxydisulfate (PDS) activation is considered as a rapid advanced oxidation process for the degradation of emerging pharmaceutical pollutants. ZnFe₂O₄@ZIF-67 nanostructures (NSs) with commendable features including a high crystallinity, a narrow bandgap, and an outstanding specific surface, showed excellent sonocatalytic performance, PDS activation and stability. A novel triple ion synergistic system was used for the swift degradation of 60 mg/L furazolidone (FZD) from real contaminated water sources. A superior sonocatalytic degradation performance of FZD (94%) by ZnFe₂O₄@ZIF-67/PDS/Ultrasound system was achieved under the optimal conditions of 20 mmol/L PDS and 0.4 g/L of the nanocomposite within 60 min. The e^-/h⁺ pairs produced as a result of the sonoluminescence phenomenon in the ZnFe₂O₄@ZIF-67 NSs, with a bandgap of 1.86 eV, accelerated the redox reduction transform cycle of the Zn²⁺/Zn, Fe³⁺/ Fe²⁺ and Co³⁺/ Co²⁺ pairs by generating a large number of oxidative radicals, leading to the enhanced degradation efficiency. Quenching tests illustrated that SO₄^•-,¹O₂, ^•OH radicals and surface oxidation–reduction reactions played a crucial role during FZD degradation. FZD degradation by-products were put forward using the LC-MS technique, and a plausible degradation pathway was suggested. The mineralization tests and the toxicity of generated intermediates of FZD degradation were also examined. Also, the stability and reusability results underscored the substantial proficiency of the above system to remediate real-pharmaceutical-contaminated-water sources, providing a practical approach for its industrial applications.