Degradation of ciprofloxacin in water by advanced oxidation process: kinetics study, influencing parameters and degradation pathways

Gamma-radiation-induced degradation of ciprofloxacin (CIP) in aqueous solution and the factors affecting the degradation process have been investigated. The results showed that CIP (4.6 mg/L) was almost completely degraded at an absorbed dose of 870 Gy. The kinetic studies of aqueous solutions containing 4.6, 10, 15 and 17.9 mg/L indicated that the decomposition of CIP by gamma irradiation followed pseudo-first-order kinetics and the decay constant (k) decreased from 5.9 x 10(-3) to 1.6 x 10(-3) Gy(-1) with an increase in CIP initial concentration from 4.6 to 17.9 mg/L. The effect of saturation of CIP solution with N-2, N2O or air on radiation-induced degradation of CIP was also investigated. The effects of radical scavengers, such as t-BuOH and i-PrOH, showed the role of reactive radicals towards degradation of CIP in the order of [GRAPHICS] . The apparent second-order rate constant of [GRAPHICS] with CIP was calculated to be 2.64 x 10(9) M-1 s(-1). The effects of solution pH as well as natural water contaminants, such as [GRAPHICS] , [GRAPHICS] , [GRAPHICS] and [GRAPHICS] , on CIP degradation by gamma-irradiation were also investigated. Major degradation products, including organic acids, were identified using UPLC-MS/MS and IC, and degradation pathways have been proposed.