Tetracycline Degradation in an Aqueous Medium Using Metal Oxide Photocatalysts under UV-Light Irradiation

Abstract

The increased occurrence of commonly used antibiotics, such as tetracycline (TTC), in wastewater, along with their resistance to conventional treatment processes, intensifies the need for more efficient and sustainable treatment methods. The present work primarily aims to investigate the photocatalytic degradation of tetracycline using three metal oxide photocatalysts as individual, binary, and ternary systems. In particular, CeO2, ZnO, and CuO are synthesized by the precipitation-assisted sol–gel technique and characterized using various analytical methods, including XRD, FE-SEM, BET, FTIR, and UV-DRS to correlate the structure–property with photocatalytic performance. The effects of various parameters, including catalyst dosage, catalyst type, time factor, and binary/ternary photocatalyst mixtures, on the degradation efficiency and the rate kinetics are also studied. With a fixed initial tetracycline concentration of 30 mg/L, optimal catalyst dose of 750 mg/L, pH 8.1, reaction temperature of 25 °C, and reaction time of 6 h, the highest degradation efficiency of 77.77% was achieved using ZnO, followed by 76.7% for CeO2 and 60.39% for CuO. Further, the ternary system CeO2–ZnO–CuO provides an improved degradation efficiency of 81.8% under similar conditions, with the highest apparent first-order rate constant of 0.00332 min–1. Radical scavenging indicates the dominant reactive behavior of superoxide radicals, while COD and LC–MS analysis reveal substantial mineralization and a possible degradation pathway for TTC. The study compares different compositions and morphologies under similar operating conditions and demonstrates the possibility of improved performance by integrating complementary photocatalysts into a combined system. The findings also provide mechanistic insights for developing efficient photocatalysts for contaminated wastewater.