Radiolytic dechlorination of polychlorinated biphenyls using alkaline 2-propanol solutions

Polychlorinated biphenyls (PCBs) were widely used as insulator fluids in electrical equipment, early in the 20th century, but were banned for use about 25 years ago due to their potential toxicity. However, they are still in storage, or present as equipment and soil contaminants, and their safe disposal remains a major challenge. On gamma irradiation in alkaline 2-propanol solutions, PCBs (Arochlor 1254 and 1016) dechlorinate stepwise, giving biphenyl as the ultimate product. Irradiation of alkaline 2-propanol solutions leads to the formation of acetone anion, which transfers electron to PCBs, and partially dechlorinated PCBs, dechlorinating them by one chlorine atom at a time and producing acetone and chloride anion. Acetone, biphenyl and oxygen inhibit the dechlorination of the PCBs. This method has the potential to be used on large scale for the dechlorination of PCBs and PCB-contaminated equipment (capacitors and transformers).