Radio frequency-enhanced remediation of PAHs-contaminated soils using peroxydisulfate: Performance and mechanistic...

Radio-frequency heating (RFH) coupled with peroxydisulfate (PDS) represents a promising approach for the remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soil, however, its performance and enhancement mechanisms remain unclear. Here, an RFH-PDS system was systematically evaluated using benz[a]anthracene (BaA) as a representative PAH, and its applicability was further assessed in field-contaminated soils. Under temperature-matched conditions, RFH outperformed conventional heating (CH) with increasing BaA degradation rate constant by 57% and reducing the apparent activation energy by 8.72 kJ mol^-1 at 50 W RF power. RFH accelerated PDS decomposition with a 1.80-fold higher rate constant and enhanced SO₄^•- and ^•OH generation, consistent with density functional theory (DFT) calculations showing RF-induced weakening of the O-O bond in PDS. The BaA desorption rate from soil was increased by 59% under RFH relative to CH, which was potentially promoted by RFH-induced dissolved organic matter release, whereas metal dissolution showed a negligible contribution. DFT and GC-MS analyses indicated that RF exposure could modify the electrostatic potential distribution of BaA and alter its degradation pathways. Overall, the temperature-matched kinetic comparison, enhanced PDS activation, and altered BaA degradation pathways suggest an RF-associated enhancement beyond bulk thermal activation. For field-contaminated soil containing eight PAHs at 402.88 mg kg^-1, RFH-PDS achieved 97.15% removal and reduced the total PAHs concentration to 11.49 mg kg^-1, with residual PAHs below regulatory limits. These findings demonstrate that the RFH-PDS system is an effective and potentially scalable technology for the remediation of PAHs-contaminated soils.