Photocatalytic degradation of ketamine using a reusable TiO2/SiO2@Fe3O4 magnetic 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 mu M, [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 center dot OH, h+ and center dot O2- in ketamine photocatalytic degradation, with center dot 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 (R) acute toxicity test), showing the promising potential of TiO2/SiO2@Fe3O4 for use in water purification.

Automated summary

This study developed a TiO2/SiO2@Fe3O4 core-shell magnetic photocatalyst for the degradation of ketamine. The photocatalyst exhibited high degradation efficiency and stable performance under simulated solar irradiation. The mechanistic investigation revealed the involvement of center dot OH, h+, and center dot O2- in ketamine degradation, with center dot O2- playing a dominant role.