In situ photoreduction of structural Fe(III) in a metal–organic framework for peroxydisulfate activation and efficient removal of antibiotics in real wastewater

Abstract Structural Fe(III) is widely found in various coordination complexes and inorganic compounds. In this work, a typical Fe-based metal organic framework (MOF) (viz. MIL-100(Fe)) was chosen as an example in the activation of peroxydisulfate (PDS) for the removal of antibiotic pollutants. Interestingly, an auto-acceleration effect was observed in the process of MIL-100(Fe) activated of PDS aided by visible light irradiation. Compared to the processes with MIL-100(Fe)-activated PDS alone and with the photoactivated PDS alone, the degradation efficiency of sulfamethoxazole (SMX) obtained by visible light assisted PDS activation by MIL-100(Fe) was enhanced by 2.1 and 5.6 times, respectively. In this process, the photogenerated electrons from MIL-100(Fe) carried out an in situ reduction of the surface structural Fe(III) to form Fe(II), which in turn significantly improved the PDS activation efficiency in the generation of ·OH and O2−· radicals for the removal of SMX. The degradation pathways of SMX were deduced based on the experimental results and density functional theory calculations. Acute toxicity estimation indicated the formation of less toxic products after the treatment of SMX. Additionally, degradation of four other antibiotics and SMX degradation in the real wastewater were investigated to further confirm the advantages of such in situ photoreduced structural Fe(III) in MOFs for the used of the PDS activation process.