Magnetic-field-assisted photocatalytic activity of CoFe₂O₄/graphene oxide nanocomposite for dye degradation

Abstract Efficient removal of persistent organic dyes from wastewater remains a significant environmental challenge. This study presents the hydrothermal synthesis of a CoFe 2 O 4 /graphene oxide (CF/GO) nanocomposite and evaluates its photocatalytic performance under magnetic-field assistance for the degradation of methylene blue (MB) and Congo red (CR) under visible-light irradiation. Comprehensive characterization was conducted using SEM, EDX, TEM, XRD, FTIR, Raman, UV-Vis DRS, and VSM techniques. The incorporation of GO reduced the band gap from 2.4 eV to 1.9 eV, enhancing visible-light absorption, while the nanocomposite maintained strong ferromagnetic properties (Ms = 53.29 emu/g, Hc = 949 Oe), facilitating magnetic recovery. Under visible-light irradiation, the CF/GO nanocomposite achieved degradation efficiencies of 84% for MB and 74% for CR within 90 min. Applying an external magnetic field (0.5 T) further increased the efficiencies to 98% and 86%, respectively. This enhancement is attributed to Lorentz-force-induced charge-carrier separation, which suppresses recombination and increases the generation of reactive oxygen species, primarily • O₂⁻ and h⁺. The photocatalyst exhibited excellent reusability, retaining over 93% efficiency after five cycles. These findings demonstrate that the CF/GO nanocomposite is a highly efficient, magnetically separable photocatalyst for wastewater treatment and underscore the synergistic effect of magnetic-field assistance in ferrite-graphene systems.