Role of micro-size zero valence iron as particle electrodes in a three-dimensional heterogeneous electro-ozonation process for nitrobenzene degradation

A novel water treatment process (designated E-Fe-0-O-3 process) was constructed by combining electrolysis, micro-size zero valence iron (Fe-0) and ozone in this study. Compared with other control processes, the combined process demonstrated a remarkable synergy, and it could obtain 90.5% of NB removal within 20 min. As for the mineralization experiment, the TOC removal efficiency for NB within 120 min was higher in the E-Fe-0-O-3 process, while the energy consumption was lower than the traditional E-O-3 and E-Fe-0 process. Interestingly, hydroxyl radicals ((OH)-O-center dot) acted as a key role for NB removal, and the concentration of (OH)-O-center dot in different processes were compared. Further study indicated (OH)-O-center dot, direct anode oxidation, direct ozonation, and zero valence iron catalysis were all responsible for nitrobenzene removal. Besides, the durability of Fe-0 in the E-Fe-0-O-3 process was systematically evaluated by reusing Fe-0 10 times. Notably, the electric field could protect micro-size zero valence iron from passivation for catalytic ozonation after the long-term reaction. Finally, other ozone-refractory organics pollutants were also investigated in the E-Fe-0-O-3 process, and the influence of various water matrices on NB removal was discussed. All results demonstrated that the E-Fe-0-O-3 process was an efficient method to remove refractory organic pollutants in various natural waters. (C) 2021 Elsevier Ltd. All rights reserved.