Kinetics for electro-oxidation of organic pollutants by using a packed-bed electrode reactor (PBER)

• A novel 3SRT was proposed to describe electro-oxidation of organic pollutants.
• Mixed-phase controlled (MPC) regime is a distinct characteristic of the bed electrode.
• Existence of the MPC is for difference of current density on metallic and particulate anode.
• Current utilization ratio (γ) is used to describe overall kinetics of anode materials.
• The 3SRT can accurately predict electro-treatment of synthetic and real industrial wastewaters.

According to the intrinsic kinetics of electro-oxidation, a novel three-stage reaction theory (3SRT) involved charge transfer controlled (CTC), mixed-phase controlled (MPC) and mass transport controlled (MTC) regimes is presented to describe the oxidation of organic pollutants by using a packed-bed electrode reactor (PBER). The proposed 3SRT could be universally used for overall oxidation due to the introduction of a parameter, current utilization ratio of γ (∼1.0) related to anode materials. The existence of MPC regime is due to the difference of the applied current density between metallic anode and bipolar activated carbon (AC) particulate anode caused by the difference of the electrode area of the two kinds of anodes. The proposed theory was employed for prediction of chemical oxygen demand (COD) during treatment of synthetic phenolic wastewater, thiophene-2,5-dicarboxylic acid manufacturing wastewater and pyridine wastewater by using IrO2 doped tantalum oxide (IrO2-Ta2O5/Ti) anode. The regression analysis and F-test results illustrate the 3SRT satisfactorily matches the experimental data obtained at different operation conditions such as current density, initial COD values and flow rate. These results confirm the proposed 3SRT could effectively predict the change of concentration of organic pollutants during electro-oxidation by using a PBER.

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