From Plastic Waste to Water Treatment: Floating Magnetic Poly(ethylene Terephthalate)–Fe3O4/TiO2 Photocatalysts for Antidepressant Removal

This study investigates the photocatalytic degradation of a mixture of three widely detected antidepressants, namely venlafaxine, bupropion, and sertraline, using a novel floating magnetic PET–Fe3O4/TiO2 composite photocatalyst. Magnetic Fe3O4/TiO2 nanoparticles were synthesized via co-precipitation/sol–gel and immobilized onto recycled poly(ethylene terephthalate) (PET) beads by non-solvent precipitation. The composites were characterized and evaluated for pharmaceutical removal under simulated solar irradiation, achieving high degradation efficiency and removing the antidepressants within 60–90 min depending on the compound. Performance was strongly influenced by inorganic loading, with the 50 wt% Fe3O4/TiO2 composite giving the highest degradation rates. Water matrix composition also significantly affected degradation kinetics, with lower efficiencies observed in complex environmental matrices due to radical scavenging and competitive adsorption. Although the parent compounds degraded rapidly, complete mineralization required prolonged irradiation, indicating the formation of intermediate transformation products. Scale-up experiments in a continuous-flow pilot reactor showed performance comparable to laboratory-scale results, confirming applicability under realistic operating conditions. The composite beads retained their photocatalytic activity over the two reuse cycles investigated, although some deformation and TiO2 loss were observed after reuse. Overall, the floating magnetic PET–Fe3O4/TiO2 photocatalyst offers a sustainable and efficient approach for removing pharmaceutical contaminants from water, combining photocatalytic efficiency with facile recovery, reusability, and valorization of recycled PET waste.