A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4-Dichlorophenoxyacetic acid degradation

Abstract

• A new pulsed switching peroxi-coagulation (PSPC) system was developed.

• The EC_T for 2,4-D removal in the PSPC was lower than that in the EF.

• The iron consumption for 2,4-D removal in the PSPC was lower than that in the PC.

The aim of this study was to develop a new pulsed switching peroxi-coagulation system to control hydroxyl radical (∙OH) production and to enhance 2,4-Dichlorophenoxyacetic acid (2,4-D) degradation. The system was constructed with a sacrifice iron anode, a Pt anode, and a gas diffusion cathode. Production of H₂O₂ and Fe²⁺ was controlled separately by time delayers with different pulsed switching frequencies. Under current densities of 5.0 mA/cm² (H₂O₂) and 0.5 mA/cm² (Fe²⁺), the ∙OH production was optimized with the pulsed switching frequency of 1.0 s (H₂O₂):0.3 s (Fe²⁺) and the ratio of H₂O₂ to Fe²⁺ molar concentrations of 6.6. Under the optimal condition, 2,4-D with an initial concentration of 500 mg/L was completely removed in the system within 240 min. The energy consumption for the 2,4-D removal in the system was much lower than that in the electro-Fenton process (68±6 vs. 136±10 kWh/kg TOC). The iron consumption in the system was ~20 times as low as that in the peroxi-coagulation process (196±20 vs. 3940±400 mg/L) within 240 min. The system should be a promising peroxi-coagulation method for organic pollutants removal in wastewater.

Graphical abstract

Keywords

Pulsed switching peroxi-coagulation system / Energy consumption / Hydroxyl radical production / 2 / 4- Dichlorophenoxyacetic acid

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