Enhanced photodegradation of doxycycline (DOX) in the sustainable NiFe2O4/MWCNTs/BiOI system under UV light irradiation

In this study, a magnetic NiFe 2 O 4 /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 NiFe 2 O 4 /MWCNTs/BiOI loading of 1.5 g L −1 , the DOX degradation (at 45 mg L −1 ) efficiency could achieve 92.18% with the reaction rate constant k of 0.0072 min −1 . 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 NiFe 2 O 4 and MWCNTs reduces the band gap energy of the NiFe 2 O 4 /MWCNTs/BiOI. The quenching test illustrates that h + , OH and O 2 − all functioned in the developed photocatalytic system, where O 2 − 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 NiFe 2 O 4 /MWCNTs. The magnetic property of NiFe 2 O 4 /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. • Recyclable NiFe 2 O 4 /MWCNTs/BiOI photocatalyst was successfully prepared. • The NiFe 2 O 4 /MWCNTs/BiOI presented enhanced photocatalytic activity toward DOX degradation. • Photocatalytic mechanism in NiFe 2 O 4 /MWCNTs/BiOI system was studied. • Three possible pathways for DOX degradation were illustrated.