Abstract 

The degradation of the antibiotic tetracycline (TC) onto the spinel MgAl₂O₄ through combined adsorption photocatalysis processes was conducted. The semiconductor MgAl₂O₄ was synthesized by the co-precipitation method and characterized by X‑ray diffraction (XRD), Scanning Electron Microscopy (SEM), and optical analysis. Capacitance potential (C⁻² – E) measurements conducted in Na₂SO₄ medium indicate that the oxide exhibits n‑type conduction, a result supported by a positive thermo-power. The TC degradation results show that under the optimal operating parameters of pH ~ 4.4, catalyst dose (0.75 g·L⁻¹), and initial TC concentration (20 mg·L⁻¹), a contact time of 30 min is sufficient to achieve 58% of the adsorption capacity. The kinetic study reveals that the TC on MgAl₂O₄ disappears almost completely (88%) under sunlight irradiation and follows the second-order model with a half photocatalytic lifetime of 33 min for a TC concentration of 20 mg·L⁻¹. This process can be described as a clean restoration alternative and is part of a sustainability perspective.