Removal of phenol from wastewater by electrochemical bromination in a flow reactor

Electrochemical methods have been widely applied in the treatment of phenol wastewater for the past few years. However, conventional electrochemical advanced oxidation processes (EAOPs) generally encounter the problem of electrode passivation and the energy consumption required for mineralization is high. In this work, we reported the treatment of phenol wastewater by electrochemical bromination method in a flow electrolysis cell. The Ti/Sb-SnO₂/PbO₂ electrode was prepared and used as anode. The experiments were carried out under different initial pH, KBr concentrations, current densities, and volumetric flow rates. The generated 2,4,6-tribromophenol (TBP) could be easily separated from the electrode surface and electrolyte. The brominated intermediates were identified by GC/MS. The removal efficiencies for phenol and COD were 100% and 82.7%, respectively, under the best operational conditions (current density of 40 mA cm^-2, KBr concentration of 0.074 mol L^-1, initial pH of 1.0, and volumetric flow rate of 114 mL min^-1). Furthermore, our electrochemical bromination method offered a high apparent current efficiency (ACE) of 276.6% and a low energy consumption (EC) of 4.54 × 10^-3 kWh gCOD^-1 after 40 min of electrolysis time, indicating that this process was suitable for phenol wastewater treatment.