Degradation of aminoglycoside antibiotics in UV-advanced oxidation processes: Kinetics, mechanisms, transformation products and toxicity

Aminoglycoside antibiotics (AGs) are frequently detected in aquatic environments and have attracted increasing concern due to their persistence and potential ecological risks. However, their degradation behavior and transformation risks in UV-based advanced oxidation processes (AOPs), particularly in real water matrices, remain insufficiently understood. Herein, the degradation kinetics and mechanisms of AGs are investigated in two commonly used AOPs, namely UV/H₂O₂ and UV/peroxydisulfate systems in real water matrix. In these systems, AGs are rapidly degraded via reactions with hydroxyl radicals (HO^•) and sulfate radicals (SO₄^•−), respectively. The second-order rate constants for reactions with HO^• and SO₄^•− are in the ranges of (2.02 − 5.22) × 10⁹, and (1.24 − 6.49) × 10⁸ M⁻¹ s⁻¹, respectively. Water matrix constituents, such as chloride and bicarbonate, significantly inhibit AG degradation via radical scavenging. Meanwhile, secondary radicals, including dichloride radicals and carbonate radicals, formed from the reactions of HO^• and SO₄^•− with matrix components, also contribute to AG degradation. Mechanistic analysis reveal that AG degradation was mainly governed by electrophilic reactions. Streptomycin is selected as a representative AG to identify transformation products in both systems and to evaluate the associated toxicity. The results show that streptomycin is gradually transformed into smaller molecular byproducts, and the toxicity increases as the molecular weight of the products decreased. This study provides important kinetic parameters and mechanistic insights into AG degradation and highlights the potential risks associated with toxic transformation products, offering valuable guidance for the application of UV-based AOPs in water treatment.