Synergism of ozonation and electrochemical filtration during advanced organic oxidation

Here, we investigated the synergistic effect towards phenol degradation and mineralization between ozonation (O₃) and electrochemical filtration (ECF) using perforated titanium as cathode and porous carbon nanotube (CNT) networks as anode. A flow rate of 1.6 mL min^-1, 10 mM of sodium sulfate electrolyte, 1.0 mM of phenol (model aromatic compound), and an ozone dose of 12 mgO₃ L^-1 were used. Insight into the synergistic mechanism was achieved via carbon anode morphology characterization and phenol degradation kinetics analysis. Improved kinetic performance was observed for the combined process (O₃-ECF) as compared to the sum of the individual processes, not only towards phenol degradation (3.2-fold increase), but also towards phenol mineralization (2.2-fold increase). Scanning electron microscopy revealed a significant decrease of polymer formation and deposition on CNT after the hybrid O₃-ECF process as compared to the ECF alone. Voltage-dependent (0-2.5 V) ozone CNT functionalization was investigated at pH 7-11 to assist in elucidation of the synergistic mechanism. X-Ray photoelectron spectroscopy indicated increases up to 26-fold in CNT oxygen content post-ozonation at pH 7 comparing to fresh CNT. Various potential O₃-ECF synergistic reaction mechanisms for organic aromatic oxidation and mineralization are discussed.