Degradation of mefenamic acid from aqueous solutions by the ozonation and O3/UV processes

This study used batch ozonation and O3/UV (ultraviolet) processes to investigate factors such as pH, ultraviolet, alkalinity, and humic acid that might affect the degradation and mineralization of mefenamic acid (MEF). The results show that ozonation and O3/UV processes were efficient in degrading MEF. A decrease of pH could enhance MEF removal by both the ozonation and O3/UV processes. Results also show that the presence of humic acid decreased the removal of MEF. In addition, the degradation of MEF could be expressed in a parallel first-order kinetic model, i.e., rapid and slow kinetic regimes, of the ozonation reaction. The simulation results show that both the fraction and rate constant of the rapid reaction increased as the pH value decreased, which is in agreement with the trend of the removal efficiency of MEF. Besides, the O3/UV process usually exhibits a higher γ, the ratio of residual MEF concentration through the rapid reaction to the slow reaction, than ozonation within just 10 min, which suggests that the rapid reaction could enhance the efficiency and effectiveness of degradation in the O3/UV process.

► Humic acid could consume ozone and hydroxyl radicals so inhibited MEF degradation.
► MEF degradation can be illustrated through the parallel rapid and slow reactions.
► MEF removal efficiency agreed with the fraction and rate constant of rapid reaction.
► Most degradation was completed within reaction time 10 min through rapid reaction.
► After 10 min MEF degradation was controlled by slow reaction.