Perchlorate formation during the electro-peroxone treatment of chloride-containing water: Effects of operational parameters and control strategies

- ClO4− formation can be prevented by using Pt/Ti anodes in the E-peroxone process.
- E-peroxone process with Pt/Ti anodes can achieve comparable pollutant degradation rates as with BDD anodes.
- ClO4− is primarily generated at the surface of BDD anode in the E-peroxone process.
- Electro-generation of H2O2 from O2 at carbon-based cathodes can decrease ClO4− formation.

This study investigated the degradation of clofibric acid and formation of perchlorate during the electro-peroxone (E-peroxone) treatment of chloride-containing (26.1-100 mg L−1) water (Na2SO4 electrolytes and secondary effluents). The E-peroxone process involves sparging O2 and O3 gas mixture into an electrolysis reactor where a carbon-based cathode is used to electrochemically convert the sparged O2 to H2O2. The electro-generated H2O2 then reacts with sparged O3 to produce OH, which can rapidly oxidize pollutants in the bulk solution. When boron-doped diamond (BDD) electrodes were used as the anode, perchlorate concentrations increased significantly from undetectable levels to ∼15-174 mg L−1 in the different water samples as the applied current density was increased from 4 to 32 mA cm−2. In contrast, no ClO4− was detected when Pt/Ti anodes were used in the E-peroxone process operated under similar reaction conditions. In addition, when sufficient O3 was sparged to maximize OH production from its peroxone reaction with electro-generated H2O2, the E-peroxone process with Pt/Ti anodes achieved comparable clofibric acid degradation and total organic carbon (TOC) removal yields as that with BDD anodes, but did not generate detectable ClO4−. These results indicate that by optimizing operational parameters and using Pt/Ti anodes, the E-peroxone process can achieve the goal of both fast pollutant degradation and ClO4− prevention during the treatment of chloride-containing wastewater.

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