Magnetic core–satellite Fe/Cu@Zeolite 13X nanocomposite as an efficient catalyst: performance in indigo carmine and tetracycline degradation

Abstract

To apply the Fenton process to remove organic pollutants from an aqueous solution, catalysts are needed that can decompose hydrogen peroxide (H₂O₂) into hydroxyl radicals and regenerate Fe²⁺ in the system. With this in mind, zeolite-based Fenton-type catalysts were prepared by incorporating Cu₂O and Fe₃O₄ particles into the zeolite X matrix. The core–satellite composite materials (Fe@Zeo13X-1, Fe@Zeo13X-2, Fe/Cu@Zeo13X-1, and Fe/Cu@Zeo13X-2) were synthesized using a hydrothermal-assisted precipitation/co-precipitation method and characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and mapping, electrochemical impedance spectroscopy (EIS), solid UV-visible and N₂ adsorption/desorption. The catalytic properties of the synthesized materials on indigo carmine degradation were evaluated. The results revealed that Fe/Cu@Zeo13X-2 exhibits the greatest catalytic activity, achieving a maximum elimination percentage of 99.96% under the following conditions: pH = 2, 0.2 g L⁻¹ of catalyst, 50 mg L⁻¹ pollutant, 5 mL of 0.05 M H₂O₂, 60 minutes, and daylight. Irradiating the system with UV radiation highlighted the photocatalytic properties of Fe/Cu@Zeo13X-2, justifying its use in optimizing the photo-Fenton degradation of tetracycline using response surface methodology. A maximum elimination percentage of 94.54% was obtained under the conditions (pH = 6; 1 g L⁻¹ of catalyst; 20.92 mg L⁻¹ pollutant; 5 mL of 0.5 M H₂O₂; 17.2 min). The first-order kinetics model seems appropriate to describe the degradation kinetics of IC by the Fe/Cu@Zeo13X-2 catalyst (R² > 0.9). The application of the Langmuir–Hinshelwood (LH) model confirms that the degradation process is limited by adsorption. The material showed good stability, allowing it use over several cycles.