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

<p>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 (<i>k</i>) decreased from 5.9  ×  10<sup>−3</sup> to 1.6  ×  10<sup>−3</sup> Gy<sup>−1</sup> with an increase in CIP initial concentration from 4.6 to 17.9 mg/L. The effect of saturation of CIP solution with N<sub>2</sub>, N<sub>2</sub>O or air on radiation-induced degradation of CIP was also investigated. The effects of radical scavengers, such as <i>t</i>-BuOH and <i>i</i>-PrOH, showed the role of reactive radicals towards degradation of CIP in the order of . The apparent second-order rate constant of with CIP was calculated to be 2.64 × 10<sup>9</sup> M<sup>−1</sup> s<sup>−1</sup>. The effects of solution pH as well as natural water contaminants, such as , , and , 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.</p>