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BACKGROUND: The objective of the present study was to analyse the kinetics of photodegradation of three antibiotics from the tetracycline group (tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC)), and the influence of the operational variables: (1) initial concentration; (2) initial solution pH; (3) addition of hydrogen peroxide; (4) effect of the aqueous matrix (ultrapure water (UW), surface water (SW), groundwater (GW) and waste‐water (WW) on these processes.

RESULTS: The results obtained show that the photodegradation of the three tetracyclines fits first‐order kinetics. The degradation rate depends on initial concentration and pH. Low concentrations of H₂O₂ markedly increased the efficacy of TC photolysis, with a linear relationship between degradation rate and H₂O₂ concentration for concentrations of 2 × 10⁻² to 2 × 10⁻¹ mmol L⁻¹. The photodegradation rate is higher in real waters than …