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

Abstract

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.