Advanced oxidation of phenol: A comparison between Fenton, electro-Fenton, sono-electro-Fenton and photo-electro-Fenton processes

► Performance of different AOP's on the degradation of phenol was compared. ► The effect of various operating parameters on the degradation was evaluated. ► Kinetics of the different methods was studied and analyzed. This study compares the performance of Fenton, electro-Fenton, sono-electro-Fenton and photo-electro-Fenton treatment methods on the degradation of phenol. The effect of operating parameters such as hydrogen peroxide concentration, Fe2+ concentration, current density, initial phenol concentration and solution pH was studied. The results showed better performance with simultaneous utilization of UV irradiation and electrolysis with Fenton's reagent. Degradation efficiency was observed in the order: photo-electro-Fenton>sono-electro-Fenton>electro-Fenton>Fenton. Even though complete degradation of phenol was observed with photo-electro-Fenton and sono-electro-Fenton processes, photo-electro-Fenton process showed complete removal of phenol and 64.19% of mineralization within 30min, whereas in the case of sono-electro-Fenton process, no phenol was detected after 40min and the mineralization observed at optimum conditions was 67.93%. Fenton and electro-Fenton processes required more time for phenol degradation and mineralization. The phenol degradation kinetics was studied and compared for all the processes. The results showed higher rate constant values for sono-electro-Fenton (kap=0.0683min−1) and photo-electro-Fenton (kap=0.0934min−1) processes.