Green Synthesis and Characterization of ZnO/CoFe2O4 Nanocomposites for Photocatalytic Degradation of Tetracycline Under Visible Light

Antibiotic contamination of water, particularly by tetracycline (TC), requires effective and sustainable treatment strategies. In this study, CoFe2O4 nanoparticles were synthesized using lime juice as a natural stabilizing agent and combined with ZnO to obtain a ZnO/CoFe2O4 nanocomposite for visible-light-driven TC degradation. Complementary characterization confirmed the coexistence of ZnO and CoFe2O4 without detectable secondary phases, with predominantly spherical and irregular particles. The composite exhibited ferromagnetic behavior, suggesting potential magnetic recovery, and showed broader visible-light absorption and a reduced band gap of 3.05 eV compared with 3.23 eV for ZnO. Although its specific surface area and pore volume were lower than those of CoFe2O4, the nanocomposite displayed the highest photocatalytic performance. Under the optimized conditions of pH 6, 20 mg L−1 TC, and 1 g L−1 catalyst, 96.8% degradation was achieved after 120 min, with a pseudo-first-order rate constant of 0.029 min−1. The degradation efficiency remained 88.3% after five cycles. Scavenger experiments identified photogenerated holes (h+) and hydroxyl radicals (·OH) as the dominant reactive species. The improved photocatalytic activity may be associated with interfacial interactions between ZnO and CoFe2O4, suggesting that the green-synthesized nanocomposite has potential as a visible-light photocatalyst for TC degradation under the investigated conditions.