Degradation of 2,4-dichlorophenoxyacetic acid by anodic oxidation and electro-Fenton using BDD anode: Influencing factors and mechanism

The degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was conducted by anodic oxidation (AO) with a boron-doped diamond (BDD) anode, and was greatly enhanced by combination with electro-Fenton (EF) using carbon black modified graphite felt (CB-GF) as cathode. A high current density, low initial pH and high concentration of Na2SO4 favored for the 2,4-D degradation by AO. In EF, 2,4-D degradation rate increased 8 times after using CB-GF cathode, obtaining a higher mineralization current efficiency (53%) and a lower energy consumption (71.8 kWh kg(-1) TOC) due to the higher generation of H2O2. It indicated that the mainly contributing radicals for 2,4-D degradation by AO was (OH)-O-center dot (57.5%), while the contribution improved to 92% by EF. Compared with AO, EF was more efficient and complete for 2,4-D degradation, confirmed by the detection of the main degradation intermediates and short-chain carboxylic acids. This work demonstrated that EF using BDD anode and high-performance CB-GF cathode was efficient for 2,4-D degradation, which would be a promising electrochemical advanced oxidation process for organic wastewater treatment.