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

Highlights

• 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.

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.

Graphical abstract

Keywords

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

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Acknowledgements

This work was partly supported by grants from the National Key Scientific Instrument and Equipment Development Project (No. 2012YQ03011108), research fund program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (No. 2016K0013), the National Natural Science Foundation of China (Grant Nos. 51608547, 51278500 and 51308557) and the Fundamental Research Funds for the Central Universities (No. 16lgjc65).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-018-1070-7 and is accessible for authorized users.

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