Degradation of quinolone antibiotic, norfloxacin, in aqueous solution using gamma-ray irradiation

This study reports the efficiency of gamma-ray irradiation to degrade quinolone antibiotic, norfloxacin, in aqueous solution. Laboratory batch experiments were conducted to determine the pseudo-first order degradation kinetics of norfloxacin in the concentration ranges of 3.4-16.1 mg L-1 by gamma-ray irradiation. The dose constant was found to be dependent on the initial concentration of norfloxacin and gammaray irradiation dose rate (D-r). The saturation of norfloxacin sample solutions with N-2, air or N2O, and the presence of tertbutanol and 2-propanol showed that (OH)-O-center dot played more crucial role in the degradation of norfloxacin. The second order rate constants of (OH)-O-center dot, c(aq)(-), and H-center dot with norfloxacin were calculated to be 8.81 x 10(9), 9.54x10(8), and 1.10 x 10(9) M-1 s(-1), respectively. The effects of various additives including CO32-, HCO3-, NO3-, NO2-, and thiourea and the pH of the medium on the degradation of norfloxacin were also investigated. Norfloxacin degradation was lower in surface water and wastewater than in ultrapure water. Several degradation byproducts of norfloxacin were identified from which the possible degradation pathway was proposed.