Comparative Study of Tetracycline Hydrochloride Degradation in UV-Based Advanced Oxidation Processes

Tetracyclines represents a widely used class of antibiotics and are frequently detected in aquatic environments, where their persistence contributes to the development of antibiotic resistance and ecological risks. This study presents a kinetic investigation of tetracycline hydrochloride (TCH) photodegradation in homogeneous aqueous media using the following UV-based advanced oxidation processes (AOPs): UV, UV/H2O2, UV/S2O ₈^2 - , UV/Fe2+/H2O2 (photo-Fenton), and UV/Fe2+/ S2O ₈^2 - (Fe2+-activated persulfate). The effects of oxidant concentration, catalyst dosage, initial TCH concentration, pH, and temperature were evaluated, and the degradation kinetics were analyzed. Direct UV irradiation with the high-pressure mercury lamp DRT-1000 resulted in degradation efficiencies of 41.8–81.1% after 60 min, with apparent rate constants ranging from 0.0051 to 0.0272 min–1, described by the pseudo-first-order model. The addition of H2O2 increased the degradation efficiency to 98.04%, while the apparent rate constants increased to 0.0342–0.0744 min–1. In the UV/S2O ₈^2 - system, degradation efficiencies reached 99.66%, with apparent rate constants ranging from 0.0241 to 0.1383 min–1 demonstrating the high oxidative potential of sulfate radicals. The photo-Fenton process achieved nearly complete TCH degradation within a substantially shorter reaction time, exhibiting apparent rate constants of 0.0398–0.0814 min–1. The UV/Fe2+/S2O ₈^2 - system exhibited the fastest degradation kinetics owing to the catalytic activation of persulfate by Fe2+, which promoted the continuous generation of sulfate anion-radicals and hydroxyl radicals. The highest apparent first-order apparent rate constant (0.144 min–1) was obtained at pH 2.6, confirming that acidic conditions favor Fe2+-activated persulfate oxidation. Overall, the addition of Fe2+ significantly accelerated persulfate activation, resulting in higher reaction rates than those obtained in the UV/S2O ₈^2 - system. The results demonstrate that the UV/Fe2+/S2O ₈^2 - and photo-Fenton systems are the most effective UV-based advanced oxidation processes for the rapid degradation of tetracycline hydrochloride can be used for the treatment of TCH-contaminated water.