Extracellular polymeric substances enhanced persulfate treatment of polychlorinated biphenyls in soil: Removal...

The strong adsorption of polychlorinated biphenyls (PCBs) in soil limits the treatment efficiency of persulfate (PS) based advanced oxidation technologies. Although traditional chemical surfactants can promote the desorption of PCBs in soil, their application poses a risk of secondary pollution. Given that extracellular polymeric substances (EPS) exhibit surfactant-like properties while remaining environmentally benign, an EPS enhanced PS (EPS-PS) system was constructed. Using PCB15 as the target contaminant, this study systematically evaluated its removal performance in soil and elucidated the underlying mechanisms of the process. The results showed that the EPS-PS system achieved a PCB15 removal efficiency of 92.5% in soil. EEM-PARAFAC analysis combined with molecular docking showed that EPS binds to PCB15 mainly through hydrophobic interactions of its protein components. DLS and cryo-TEM results further indicate that PS can disrupt the micellar structure of EPS, facilitating the release of PCB15 from the hydrophobic core and its subsequent oxidation. Reactive species identification and electrochemical analyses revealed that EPS can react with SO₄•^- to generate ¹O₂ and Q•⁻/SQ•⁻, while a non-radical oxidation pathway involving direct electron transfer also operates in the system. GC-MS analysis indicated that PCB15 underwent dechlorination, biphenyl cleavage, and ring opening processes, ultimately forming low toxicity products. In addition, the physicochemical properties of the treated soil were significantly improved. This study provides a new green and efficient strategy for the remediation of chlorinated organic pollutants (COPs) in soil.