Degradation of tetracycline by solar photo‐Fenton: Optimization and application in pilot photoreactor

The objective of this study is to analyze the photodegradation of the antibiotic tetracycline by the solar photo‐Fenton process. The optimal conditions were obtained in a 2² (2 × 2) factorial design with the following input variables: reaction time and catalyst concentration (ferrous ion [Fe 2+ ]). After statistical analysis using the Statistica 7.0 software, the optimal conditions determined, time = 120 min and Fe 2+  = 166.81 mg/L, were applied in a pilot scale photoreactor, resulting in an 88.7% removal of the drug. In addition, in this stage we studied the reaction kinetics, biodegradability, and phytotoxicity of the products generated by the process. In the kinetic study, a constant of 1.82 × 10 −2 min −1 was obtained. For this constant, a reaction time of 38.16 min is required for the initial tetracycline concentration to be reduced by 50%. The biodegradability tests indicated a gradual increase in the five‐day biological oxygen demand/chemical oxygen demand ratio over time. The phytotoxicity tests showed an 18.5% decrease in the inhibition rate of the root growth of lettuce seedlings, indicating that the treatment applied reduces the toxicity of the substance.