UV-Based Degradation of Fluoroquinolone Antibiotic in Wastewater: Effects of Process Parameters, Identification of Degradation Products and Evaluation of Residual Toxicity

In the present work, the UV-H₂O₂ process was investigated to degrade a fluoroquinolone antibiotic, ciprofloxacin (CIP), one of India’s widely used antibiotics, from aqueous solutions using a batch-type UV reactor having photon flux of 1.9(± 0.1) × 10^–4 Einstein L⁻¹ min⁻¹. The effects of UV irradiation time on CIP degradation were investigated for both UV and UV-H₂O₂ processes. It was found that about 75% degradation of CIP was achieved within 60 s with initial CIP concentration and peroxide concentration of 10 mg L⁻¹ and 1 mol H₂O₂/mol CIP, respectively, at pH of 7(± 0.1) and fluence dose of 113 mJ cm⁻². The experimental data were analyzed using the first-order kinetics model to find the time- and fluence-based degradation rate constants. Under optimized experimental conditions (initial CIP concentration, pH, and H₂O₂ dose of 10 mg L⁻¹, 7(± 0.1) and 1.0 mol H₂O₂/mol CIP, respectively), the fluence-based pseudo-first-order rate constant for the UV and UV-H₂O₂ processes were determined to be 1.28(± 0.0) × 10^–4 and 1.20(± 0.04) × 10^–2 cm² mJ⁻¹ respectively. The quantum yields at various pH under direct UV were calculated. The impacts of different process parameters such as H₂O₂ concentration, solution pH, initial CIP concentration, and wastewater matrix on CIP degradation were also investigated in detail. CIP degradation was favorable in acidic conditions. Six degradation products of CIP were identified. Further, the bioassay of treated CIP effluent indicated lesser toxicity than the parent compound. Results clearly showed the potentiality of the UV-H₂O₂ process for the degradation of antibiotics in wastewater.