Magnetically separable CeO₂/CoFe₂O₄ heterojunction photocatalysts for dye degradation: characterization and mechanism

ABSTRACT

This study developed magnetically separable CeO₂/CoFe₂O₄ heterojunction photocatalysts for dye degradation to reduce water pollution. The CeO₂/CoFe₂O₄ nanocomposites with different CeO₂ ratios (10, 20, and 30 wt%) were prepared by a precipitation method. The nanocrystalline 20%CeO₂/CoFe₂O₄ photocatalyst with a surface area of 117 m².g⁻¹, E_g 2.37 eV, and uniform distribution of quasi-spherical CeO₂ minor phase (cubic fluorite structure with particle size 3 ± 1 nm) throughout the distorted spherical CoFe₂O₄ major phase (cubic spinel structure with particle size 9 ± 3 nm) showed the best photocatalytic performance for methylene blue (MB) degradation under UV light irradiation at the efficiency of 88.7% and the apparent rate constant (k) of 0.0138 min⁻¹. The 20%CeO₂/CoFe₂O₄ photocatalyst had a good magnetic response and could be easily separated from the dye solution by applying an external magnetic field. The reusability test showed lower photodegradation efficiency due to the adsorption of residual MB dye on the photocatalyst surface. The formation of heterojunction at the interfaces of CeO₂/CoFe₂O₄ facilitated the photogenerated charge separation and increased availability of active species of holes (h⁺) and hydroxy radicals (^∙OH), which were the key factors in improving the photocatalytic activity.

GRAPHICAL ABSTRACT

HIGHLIGHTS

• Improved photocatalysis in CeO₂-coupled CoFe₂O₄ composites.

• Heterojunctions in CeO₂/CoFe₂O₄ increase the availability of active species.

• External magnetic field separates the photocatalyst from the dye solution.

KEYWORDS:

• Photocatalyst
• dye degradation
• heterojunction
• composite
• cobalt ferrite

Acknowledgments

This work was supported by the [School of Science, King Mongkut’s Institute of Technology Ladkrabang (KMITL)] under Grant [number 2565-02-05-019]. We thank the Scientific Instruments Center, Faculty of Science, King Mongkut’s Institute of Technology Ladkrabang.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the School of Science, King Mongkut’s Institute of Technology Ladkrabang (KMITL) [2565-02-05-019].