Photocatalytic degradation of ketamine using a reusable TiO2/SiO2@Fe3O4magnetic photocatalyst under simulated solar light

TiO2 heterogeneous photocatalytic processes can carry out efficient abatement of various organic pollutants; however, the difficult recyclability of catalysts largely hinders their application. This study aims to develop a TiO2/SiO2@Fe3O4 core-shell structure magnetic photocatalyst for the degradation of ketamine, a recalcitrant pharmaceutical pollutant commonly found in aquatic environments. The structure and morphology of the TiO2/SiO2@Fe3O4 photocatalyst were comprehensively characterized. Compared with commercial P25 TiO2, the fabricated TiO2/SiO2@Fe3O4 photocatalyst exhibited a higher ketamine degradation efficiency under simulated solar irradiation, with a pseudo-first-order rate constant of 0.1768 min-1 (conditions: [ketamine]0 = 0.3 μM, [TiO2/SiO2@Fe3O4] = 100 mg/L and pH = 7). Additionally, the magnetic TiO2/SiO2@Fe3O4 was easily recovered and showed stable performance, with the ketamine degradation rate only slightly decreasing from 100% to 91% within six cycles of use. The mechanistic investigation demonstrated the participation of •OH, h+ and •O2- in ketamine photocatalytic degradation, with •O2- playing the dominant role. During the photocatalytic pathways of ring opening, oxygen addition, N-demethylation and hydroxylation, ketamine was decomposed into byproducts and further achieved efficient mineralization and detoxification (performed by the Microtox® acute toxicity test), showing the promising potential of TiO2/SiO2@Fe3O4 for use in water purification.