Regulation of Electrochemically Generated H2O2 in Situ from a Novel CB-PTFE Cathode for Transformation of Chlorine Benzene in Groundwater

Fenton’s reagents (H₂O₂ and Fe²⁺ catalyst commonly) have been widely used in soil and groundwater remediation. But the excessive H₂O₂ decomposition and the pH modification (acidification) problem have been limitations for Fenton based remediation strategies. The Electro-Fenton (E- Fenton) processes has been recently developed to solve the problems, in which Fe²⁺ or H₂O₂are generated in situ as continuing source of Fenton's reagents.

In this study, a novel CB-PTFE cathode and a Fe cathode were employed to generate H₂O₂ and Fe²⁺ in situ simultaneously. The generated reactive oxidizing species, i.e., O₂,H₂O₂ and hydroxyl radical (HO•), oxidized bio-refractory organics to nontoxic matters in groundwater. Automatic pH adjustments are achieved by appropriately arraying the electrodes. Laboratory batch tests and column tests for the E-Fenton oxidation and hybrid electrolysis system were conducted to evaluate the transformation efficiency of chlorine benzene. Results from batch experiments suggested the CB-PTFE cathode was effective for reducing O₂ to H₂O_2. The H₂O₂ concentration reached 468 mg/L under the condition of pH 3.0 and 30mA/cm² in 60 minutes, which was 5 and 10 times of that with a graphite and C-felt cathode. The removal efficiency of chlorine benzene reached 80% in 20 minutes. Both chlorine benzene degradation and H₂O₂ production increased with decreasing solution pH and increasing current density. The results from the columns tests proved that the in situ E-Fenton system is a feasible method for groundwater remediation.