Photodechlorination of polychlorinated biphenyls (PCBs) dissolved in surfactant solutions

Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants. Being highly hydrophobic and stable, they are usually chemical and biological recalcitrant but more photodegradable. In this paper, 2,2',4,4'-tetrachlorobiphenyl (2,2',4,4'CB) has been selected as a typical congener of PCBs to study the photodechlorination of PCB dissolved in anionic surfactant (sodium dodecyl sulfate, SDS) solutions. Under UV irradiation at 254 nm, 2,2',4,4'CB was decomposed. The UV-VIS spectra of photolyzed samples showed that the K band of spectra shifted red as photolysis time increased. By further analysis, less chlorinated PCB congeners (2,4,4'-trichlorobiphenyl, 4,4'-dichlorobiphenyl, 4-chlorobiphenyl) as well as chloride were identified as the photoproducts of the tested PCB. Excellent mass balance existed between 2,2',4,4'CB and its products. These results indicated that stepwise photodechlorination of the PCB with preferential removal of ortho chlorine appeared to be the principal pathway of the PCB photodegradation. By serving as H-atom donor in dechlorination and providing a non-polar solvent environment for dechlorination inside the surfactant micelles, surfactant enhanced photolysis. Therefore, surfactant washing followed by photolysis appears to be a viable technology for remediation of PCB contaminated soils.