Degradation of 2,4-dichlorophenoxyacetic acid by a novel photoelectrocatalysis/photoelectro-Fenton process using Blue-TiO2 nanotube arrays as the anode

2,4-dichlorophenoxyacetic acid (2,4-D)'s removal was studied in the photoelectrocatalysis/photoelectro-Fenton (PEC-PEF) process with Blue-TiO2 nanotube (Blue-TNTs) and modified carbon felt as the anode and cathode, respectively. Polytetrafluoroethylene and carbon black were used to modify the carbon felt to improve the efficiency of H2O2 production. The impact factors of 2,4-D degradation in the PEC-PEF process were investigated, including Fe2+ dose, bias potential, light intensity and the concentration of 2,4-D. It was found that the removal of 2,4-D increased firstly and then decreased with the increase of Fe2+ dose. Bias potential and light intensity played a positive role on 2,4-D removal, while the opposite was right for the impact of 2,4-D initial concentration. Compared with stainless steel, the modified carbon felt was found more efficient for 2,4-D removal as it could generate more H2O2. Reactive species for 2,4-D degradation was studied and it was proved that •OH radical rather than holes was mainly responsible for the removal. Such PEC-PEF process offered a promising alternative for herbicide-containing wastewater treatment.