Electro-Fenton Degradation of Carbamazepine: H2O2 Production and Energy Demand Comparison with Fenton Oxidation

The electro-Fenton (EF) process is a promising advanced oxidation technology for the removal of micropollutants (MPs) from wastewater. This study aimed to identify energy-efficient operating conditions for H2O2 electro-production and EF degradation of the neutral micropollutant carbamazepine (CBZ). The effects of current density, residence time (RT), Reynolds number, pH, and temperature were evaluated, and non-EF removal pathways and flow-configuration effects were quantified. H2O2 production was maximized under conditions that sustained current efficiencies ≥ 50%, corresponding to specific energy consumption of 4.0–6.4 kWh/kg H2O2. Non-EF removal mechanisms intrinsic to the divided electrolytic cell accounted for approximately 35% of total CBZ removal at an RT of 5 min. Under energy-efficient EF conditions (25:1 H2O2:Fe2+ and 5 min RT), CBZ removal efficiency reached 95%. Asymmetric flow configurations reduced apparent removal through dilution. In contrast, directing the cathode effluent through the anode enhanced oxidation and reduced treated water volume without additional energy input. Total electrical energy per order of CBZ removal from secondary effluent for EF (73.8–94.4 kWh/m3) was comparable to that of Fenton oxidation (61.1–100.0 kWh/m3). In both processes, H2O2 production dominated the energy demand. The results highlight EF as a feasible, energy-competitive option for removing persistent MPs from wastewater effluents.