Co-production of peroxocarbonates and hydrogen peroxide: Towards process integration in the electrochemical production of oxidants

The simultaneous formation of peroxocarbonate and hydrogen peroxide in the same electrochemical reactor and using the same electric current was studied. To achieve this, a 3-D resin-printed electrolyzer was specially designed to induce a highly turbulent flow pattern and ensure efficient gas release. A PEM membrane separated the electrode compartments. In the cathodic compartment, a gas diffusion electrode was used to generate H2O2 while in the anodic compartment, a boron doped diamond anode was used to produce C2O62- . Sodium carbonate served as the salt and reactant in the electrolyte feed. The optimal production conditions for both oxidants were studied by varying the salt concentration in the electrolytes and the applied current density. Results indicated that the changes in the electrolyte salt concentration had negligible effect on H2O2 production, while higher Na2CO3 concentrations positively influenced C2O6 2-generation. The best performance in terms of current efficiency and energy consumption occurred at a current density of 6.25 mA cm- 2 with 97 % coulombic efficiency and 8.83 kWh kg- 1 for H2O2 and 37.2 % coulombic efficiency and 6.08 kWh kg- 1 for C2O62- . Additional tests were also carried out to comprehend scaling-up effects (scaling factor 4.7) and the influence of operation modes (from batch to continuous).