Abatement of Polychoro-1,3-butadienes in Aqueous Solution by Ozone, UV Photolysis, and Advanced Oxidation Processes (O₃/H₂O₂ and UV/H₂O₂)

The abatement of 9 polychloro-1,3-butadienes (CBDs) in aqueous solution by ozone, UV–C(254 nm) photolysis, and the corresponding advanced oxidation processes (AOPs) (i.e., O 3 /H 2 O 2 and UV/H 2 O 2 ) was investigated. The following parameters were determined for 9 CBDs: second-order rate constants for the reactions of CBDs with ozone ( k O 3 ) (<0.1–7.9 × 10 3 M –1 s –1 ) or with hydroxyl radicals ( k • OH ) (0.9 × 10 9 – 6.5 × 10 9 M –1 s –1 ), photon fluence-based rate constants ( k ′) (210–2730 m 2 einstein –1 ), and quantum yields (Φ) (0.03–0.95 mol einstein –1 ). During ozonation of CBDs in a natural groundwater, appreciable abatements (>50% at specific ozone doses of 0.5 gO 3 /gDOC to ∼100% at ≥1.0 gO 3 /gDOC) were achieved for tetra-CBDs followed by ( Z )-1,1,2,3,4-penta-CBD and hexa-CBD. This is consistent with the magnitude of the determined k O 3 and k • OH . The formation of bromate, a potentially carcinogenic ozonation byproduct, could be significantly reduced by addition of H 2 O 2 . For a typical UV disinfection dose (400 J/m 2 ), various extents of phototransformations (10–90%) could be achieved. However, the efficient formation of photoisomers from CBDs with E / Z configuration must be taken into account because of their potential residual toxicity. Under UV–C(254 nm) photolysis conditions, no significant effect of H 2 O 2 addition on CBDs abatement was observed due to an efficient direct phototransformation of CBDs.