Co(II)/peracetic acid process enables efficient dichlorophenol degradation with negligible regulated chlorinated disinfection byproducts formation

Abstract

As a refractory toxic and bioaccumulative emerging contaminant, there is an urgent need for environmentally friendly water treatment processes to destroy 2,6-dichlorophenol (2,6-DCP). The present study evaluated the degradation of 2,6-DCP and regulated chlorinated disinfection byproducts (DBPs) formation in the Co(II)/peracetic acid (PAA) process. The findings demonstrated that the neutral Co(II)/PAA process exhibited a remarkable 2,6-DCP degradation efficiency with a rate constant of 0.126 min⁻¹. Furthermore, an increase in the PAA or Co(II) dosage led to higher degradation efficiency. Scavenging experiments and electron spin resonance analysis identified that CH₃C(O)OO^• and derived Cl^• were responsible for 2,6-DCP degradation. Furthermore, H₂O₂, Cl⁻, HCO₃⁻, H₂PO₄⁻, and suwannee river natural organic matter (SRNOM) inhibited 2,6-DCP degradation. Satisfactory 2,6-DCP degradation performance (over 70.0 %) was obtained in three selected real water matrices. The degradation pathways, elucidated by liquid chromatograph mass spectrometer analysis and quantum chemical calculations, involved dechlorination, hydroxylation, and benzene ring cleavage. In addition, the ecological structure–activity relationships assessment showed that the overall toxicity was reduced. Finally, SRNOM had no substantial influence on CHCl₃ formation pattern, whereas elevated SRNOM concentrations were associated with diminished levels of CHCl₃. In summary, this study provided new insights into the 2,6-DCP degradation mechanisms and regulated chlorinated DBPs formation in the PAA based advanced oxidation process.