Complete decomposition of halogenated organic contaminants via electron beam irradiation

Electron beam (E-beam) irradiation is increasingly used in applications including sterilization, material modification, and wastewater treatment. In this study, the removal, dechlorination, mineralization, and detoxification of three model halogenated organic contaminants (HOCs), i.e., triclosan (TCS), chlorpyrifos (CPF) and PCB-28, under E-beam irradiation were systematically evaluated. We used 14 C labeling to quantify mineralization, track intermediate products, and verify carbon mass balances. At an initial concentration of 20 μg L −1 , 90% removal of TCS, CPF, and PCB-28 parent compounds was an achieved at absorbed doses of 2.20, 2.30, and 5.21 kGy, respectively. Complete disappearance occurred at 5 kGy for TCS and CPF and at 10 kGy for PCB-28, corresponding to less than 3 s of irradiation. Notably, E-beam irradiation induced the cleavage of aromatic rings, leading to mineralization to 14 CO 2 as unequivocal evidence for complete decomposition. Mineralization reached 94.40% for TCS, 75.43% for CPF, and 65.80% for PCB-28 at 200 kGy. Controlled atmosphere experiments revealed that ·OH was the primary species responsible for parent compound removal and ring cleavage, while e aq ⁻ and H· predominantly contributed to reductive dechlorination. Under O 2 -saturated conditions, mineralization of TCS and CPF was further enhanced to 99.2% and 94.1% at 200 kGy, respectively. The presence of dissolved organic matter exhibited a moderate promotional or inhibitory effect on HOC removal at low absorbed doses (< 2 kGy), while its influence became negligible at doses >5 kGy, suggesting broad applicability of E-beam irradiation technology. Toxicity assays indicated 8.5- and 4.1-fold reductions in the acute toxicity of TCS and CPF aqueous samples, respectively, after 2 kGy irradiation. The rapid mineralization and detoxification demonstrated E-beam irradiation as a highly effective and clean technology to remove persistent organic contaminants from water.