Degradation of Ciprofloxacin by UV/PS and UV/PS/Fe ²⁺ Processes: Kinetics, Mechanism, and Toxicity Investigations

ABSTRACT The present study investigates the degradation of ciprofloxacin (CIP), an antibiotic, using UV‐based advanced oxidation processes, that is, UV photolysis, UV/persulfate (UV/PS), and UV/PS/ferrous ions (UV/PS/Fe 2+ ) processes. The degradation efficiencies were measured to be 15.8% and 86.5% at 60 min using sole UV and UV/PS, respectively, employing [CIP] 0 = 10 mg/L, pH = 6.0, and [PS] 0 = 0.5 mM (in the case of UV/PS system). The UV/PS/Fe 2+ system further improved efficiency, eliminating 92.6% of CIP within 45 min under optimal conditions of: [CIP] 0 = 10 mg/L, [PS] 0 = 0.5 mM, [Fe 2+ ] 0 = 0.5 mg/L, and pH = 3.0. The experiments were conducted under varying pH conditions. The UV/PS process was most effective at pH 6.0, as evident by the values of rate constants ( k o b s ), that is, 0.0313, 0.0366, and 0.0278 min −1 at pH 3.0, 6.0, and 11, respectively, at 300 min. However, UV/PS/Fe 2+ showed greater activity at pH 3.0. Furthermore, the removal of TOC was found to be 32.8% and 46.4% for UV/PS and UV/PS/Fe 2+ , respectively. The effects of inorganic anions, such as chloride, nitrate, bicarbonate, and carbonate, were found to inhibit CIP degradation. Gas chromatography–mass spectrometry (GC–MS) was used to identify the degradation products (DPs), and toxicity of CIP and its DPs was evaluated by Ecological Structure Activity Relationship (ECOSAR) program. This work provides a comprehensive understanding of degradation pathways, environmental factors affecting CIP removal by UV/PS and UV/PS/Fe 2+ , and toxicity evaluation, highlighting the novelty of this work.