Enhanced photodegradation of doxycycline (DOX) in the sustainable NiFeO/MWCNTs/BiOI system under UV light irradiation.

In this study, a magnetic NiFeO/MWCNTs/BiOI composite were fabricated and applied for enhanced and sustainable photocatalytic degradation of doxycycline (DOX) under UV light irradiation. The as-synthesized material was characterized by a series of techniques and its photocatalytic property was assessed via a couple of batch tests. With the pH at 3.0 and NiFeO/MWCNTs/BiOI loading of 1.5 g L, the DOX degradation (at 45 mg L) efficiency could achieve 92.18% with the reaction rate constant k of 0.0072 min. The high mineralization of DOX suggests the strong oxidation of both the parent pollutant and the intermediary products in the ternary catalyst system. DRS spectra indicated that compared with BiOI, the introduction of NiFeO and MWCNTs reduces the band gap energy of the NiFeO/MWCNTs/BiOI. The quenching test illustrates that h, OH and O all functioned in the developed photocatalytic system, where O and h play the dominant roles in DOX degradation. The more efficient electron-h separation and more oxidizing species induced by UV light resulted in the significant improvement of DOX abatement in the developed coupling system compared with that on either BiOI or NiFeO/MWCNTs. The magnetic property of NiFeO/MWCNTs/BiOI enables its easy separation of the solid catalyst from the reaction solution and the sustainable application in the photocatalysis. Based on the intermediates of DOX decomposition identified by UPLC-MS, the possible degradation routes were proposed accordingly.