Synthesis and Characterization of CuFe2O4–ZnO Nanocomposite via Ultrasonication-Assisted Microwave Combustion for Photocatalytic Degradation of Crystal Violet Dye

Abstract

Water contamination from toxic industrial dyes poses a serious environmental threat due to their stable aromatic structures and resistance to conventional treatments. Hence, developing efficient, visible-light-active, and reusable photocatalysts is vital for sustainable wastewater purification. In this study, CuFe2O4 (CFO), ZnO nanoparticles, and a CuFe2O4–ZnO nanocomposite were synthesized, and their structural, surface, optical, and photocatalytic properties were systematically investigated. Zeta potential analysis confirmed high colloidal stability with values of − 38.5 mV (CFO), − 24.9 mV (ZnO), and − 46.7 mV (CF-ZnO NC). DLS revealed average hydrodynamic sizes of 125 nm, 869 nm, and 365 nm for CFO, ZnO, and CF-ZnO NC, respectively. XRD confirmed the cubic spinel structure of CFO (34.29 nm) and the wurtzite phase of ZnO (48.17 nm), while the CF-ZnO NC exhibited combined reflections with a crystallite size of 36.52 nm. HR-SEM with EDX and elemental mapping showed spherical morphology with agglomeration, accurate elemental identification, and homogeneous elemental distribution. BET analysis indicated surface areas of 27.19 m2/g (CFO), 24.82 m2/g (ZnO), and 29.32 m2/g (CF-ZnO NC), with the composite also exhibiting higher pore volume (0.14 cm3/g) and pore diameter (14.95 nm). FTIR and Raman spectra verified metal–oxygen bonding and phase stability, while XPS confirmed the oxidation states of Cu2+, Fe2+, and Zn2+. Optical studies revealed band gaps of 1.82 eV (CFO), 2.91 eV (ZnO), and 1.71 eV (CF-ZnO NC). PL spectra showed notable quenching in the composite, indicating reduced electron–hole recombination. Photocatalytic activity was evaluated through crystal violet (CV) dye degradation. Under optimized conditions (pH 9.0 ± 0.1 and 20 mg catalyst dosage), CF-ZnO NC achieved 98.19% degradation within 60 min with a rate constant of 0.0548 min−1. Effective mineralization was confirmed with COD (86.23%) and TOC (72.91%) removal. Reusability tests showed excellent stability, retaining ~ 91.27% efficiency after five cycles, while scavenger experiments identified hydroxyl radicals (·OH) as the dominant reactive species. Overall, CF-ZnO NC demonstrates high stability, reusability, and outstanding photocatalytic efficiency, making it a promising for wastewater treatment applications.