Keywords: 
• ciprofloxacin /
• UV/2O2 /
• kinetics /
• photodegradation

Abstract: The photodegradation of ciprofloxacin in UV/2O2 process was investigated with a low-pressure UV lamp system. The influence of initial pH values， 2O2 concentration and water quality was discussed； proposed photoproducts of ciprofloxacin were also analyzed. Results show that ciprofloxacin displays a pH-dependent degradation and the neutral condition is more favorable. Reaction rates increased with the increasing of 2O2 concentration， and the optimal 2O2/ciprofloxacin molar ratio at which the highest reaction rate constant is reached is 2 000. In UV direct photolysis， photodegradation rates of ciprofloxacin in natural water are higher than in ultrapure water； while in UV/2O2 process， the photodegradation rates in natural water are lower than those in ultrapure water. Moreover， several photoproducts such as propanedioic acid， glycerin， 1， 4-benzenedicarboxylic acid， and some aliphatic acids etc. forming in the photodegradation of ciprofloxacin in UV/2O2 process are identified by GC-MS.