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

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 30 min, whereas in the case of sono-electro-Fenton process, no phenol was detected after 40 min 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 = 0.0683 min−1) and photo-electro-Fenton (kap = 0.0934 min−1) processes.