Radiolytic decomposition of ciprofloxacin using γ irradiation in aqueous solution.

Gamma irradiation-induced decomposition of ciprofloxacin (CIP) was elucidated with different additives, such as CO3 (2-), NO3 (-), NO2 (-), humic acid, methanol, 2-propanol, and tert-butanol. The results show that low initial concentration and acidic condition were favorable for CIP removal during γ irradiation. By contrast, radiolytic decomposition of CIP was inhibited with the addition of anions and organic additives. As a strong carcinogen, Cr(6+) was especially mixed with CIP to produce combined pollution. It is noteworthy that the removal of the mixture of CIP and Cr(6+) presented a synergistic effect; the degradation efficiency of the two pollutants was markedly improved compared to that of the single pollutant during γ irradiation. Based on the results of quantum chemical calculations and LC-MS analysis, we determined seven kinds of degradation intermediates and presented the CIP degradation pathways, which were mainly attributed to the oxidation process of hydroxyl radicals OH· and the direct decomposition of CIP molecules.