Highly effective dehalogenation and detoxification of trihalophenols by activated peroxydisulfate with black carbon derived from coal tar

In this study, highly efficient dehalogenation and detoxification of trihalophenols was achieved by activated peroxydisulfate (PDS) with black carbon (BC) derived from coal tar. 93.8% of 2,4,6-tricholophenol (TCP), 97.6% of 2,4,6-tribromophenol (TBrP) and almost 100% of 2,4,6-triiodophenol (TIP) was respectively oxidized by PDS (500 μM) in the presence of 20 mg/L of BC. ¹O₂ and surface-bound radicals were proved to be dominant oxidizing species responsible for trihalophenols degradation. Alkaline condition was favorable for PDS/BC oxidation process to degrade trihalophenols. Chloride ion and natural organic matter (NOM) would suppress the oxidation of trihalophenols, while bicarbonate ion presented a promoting effect. Meanwhile, Cl‾, Br‾ and IO₃‾ was formed during the degradation of TCP, TBrP and TIP, respectively, with approximately 43.5% of TCP, 52.4% of TBrP and 61.8% of TIP dehalogenated. No detection of toxic byproduct ClO₃‾ and BrO₃‾ was observed in the PDS/BC system owing to the excellent reducing capacity of BC to rapidly convert reactive halogen intermediates (HOX) to X‾. Products analyses showed that trihalophenols were oxidatively transformed to dehalogenated-hydroxylated products by the PDS/BC system and these halogenated intermediates could be further degraded. Moreover, the toxicity of trihalophenols was confirmed to be effectively eliminated by the PDS/BC system through In-vitro toxicity assay based on luminescent bacteria test and in-silico toxicity prediction through ECOSAR program. Therefore, PDS/BC oxidation technology is a promising strategy for removing trihalophenols and their toxic by-products in treated water effluent.