Efficient Polymerization Removal of Phenolic Pollutants by In Situ-Formed Iron-Complexes in Thermally Activated Peroxydisulfate Systems

Polymerization-based abatement of phenolic pollutants triggered by thermally activated sodium peroxydisulfate (PDS) is an effective remediation approach characterized by low oxidant consumption but restricted by narrow reaction conditions and risk of overoxidation of the organics. In particular, the polymerization is ineffective for recalcitrant phenolics and at low temperature, low initial concentration of phenolics, and high PDS dosage. The present contribution demonstrates that adding ferric chloride significantly enhances the removal efficiency, polymerization ratio, and PDS utilization efficiency, especially under the unfavorable conditions mentioned above. In the FeCl3-enhanced heat/PDS system, polymerization is promoted by iron-phenolic complexes, which favor the generation of more stable radical monomers through ligand to metal charge transfer. The ferrous ions thereby formed can accelerate PDS activation, thus synergistically contributing to polymerization. In comparison to the conventional mineralization-based advanced oxidation technologies, this process exhibits significantly higher oxidant utilization efficiency under a broad range of conditions, reducing PDS consumption by 85% when used for the treatment of real coking wastewater. Results highlight the great potentiality of this technology for the removal of phenolic pollutants and bring fundamental insights for low-carbon emission and sustainable remediation of industrial wastewater.