Rapid degradation of tetracycline hydrochloride by heterogeneous photocatalysis coupling persulfate oxidation with MIL-53(Fe) under visible light irradiation

Abstract This work demonstrates a facile route to assemble MIL-53(Fe) by solvothermal method. Sulfate radical-based advanced oxidation processes (SR-AOPs) coupling with photocatalysis based on MIL-53(Fe) were investigated under visible light. The catalytic effect of MIL-53(Fe) for the degradation of tetracycline hydrochloride (TC-HCl) was systematically studied, as well as the reusability of the catalyst and the effect of operating parameters. The results indicated that 99.7% of TC (300 mg/L)could be degraded within 80 min in the SR-AOPs coupling with photocatalysis processes, as compared to 71.4% for the SR-AOPs and only 17.1% for the photocatalysis. The trapping experiments and electron spin-resonance spectroscopy (ESR) showed the photogenerated electrons of MIL-53(Fe) under visible light irritation were trapped by persulfate to generated sulfate radicals which effectively suppressed the recombination of photogenerated carriers. And also, the SO4-• could be formed by the conversion between Fe (Ⅲ) and Fe (Ⅱ) in MIL-53(Fe). Moreover, •OH and •O2- generated by the reaction increased significantly due to the increase of SO4-• which generated more •OH and reduced photogenerated carrier recombination respectively. Thus, the degradation efficiency of TC-HCl was improved. Furthermore, the degradation pathway for TC-HCl was proposed using the theoretical calculations and liquid chromatography coupled with mass spectrometry.