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

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/HO and UV/HO) was investigated. The following parameters were determined for 9 CBDs: second-order rate constants for the reactions of CBDs with ozone (k) (<0.1-7.9 × 10 M s) or with hydroxyl radicals (k) (0.9 × 10 - 6.5 × 10 M s), photon fluence-based rate constants (k') (210-2730 m einstein), and quantum yields (Φ) (0.03-0.95 mol einstein). During ozonation of CBDs in a natural groundwater, appreciable abatements (>50% at specific ozone doses of 0.5 gO/gDOC to ∼100% at ≥1.0 gO/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 and k. The formation of bromate, a potentially carcinogenic ozonation byproduct, could be significantly reduced by addition of HO. For a typical UV disinfection dose (400 J/m), 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 HO addition on CBDs abatement was observed due to an efficient direct phototransformation of CBDs.