Waste Moringa oleifera Pod Husk-Supported Mixed-Metal Spinel Ferrite Composite for Adsorption-Assisted Tetracycline Photodegradation Under Ultraviolet and Solar Irradiation

In this study, waste Moringa oleifera pod husk (MPH) was valorised as a low-cost biomass support for Cd0.5Cu0.5Fe2O4 mixed-metal spinel ferrite to develop an adsorption-assisted sustainable photocatalytic system for tetracycline (TC) removal. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM). The effects of reaction time, initial TC concentration, catalyst dosage, solution pH, H2O2 concentration, and temperature were systematically investigated. Under the selected optimum conditions of 60 mg L−1 catalyst, 400 mg L−1 H2O2, pH 7.2, and 26 °C, the Cd0.5Cu0.5Fe2O4/MPH/UV/H2O2 system achieved approximately 96% TC removal and 87% COD removal within 60 min, demonstrating substantial degradation and mineralization at near-neutral pH and ambient temperature. Moreover, the kinetics of TC oxidation is studied and the results showed the reaction is following the pseudo-first-order kinetics. Radical-scavenging experiments identified •OH as the predominant oxidative species, while •O2− and h+ also contributed to the degradation pathway, supporting a synergistic mechanism involving MPH-assisted adsorption, photoinduced charge generation, and H2O2-assisted reactive oxygen species formation. Further, the composite retained approximately 79% TC removal after six successive reuse cycles, demonstrating substantial operational reusability under the investigated conditions. The composite also exhibited effective activity under natural solar irradiation, achieving approximately 93% TC removal within 120 min, demonstrating its potential for solar-driven wastewater treatment. Hence, the developed Cd0.5Cu0.5Fe2O4/MPH composite provides a promising route for coupling agricultural-waste valorisation with efficient adsorption–photocatalytic treatment of antibiotic-contaminated water.