Microwave-Enhanced Decomposition of Polychlorinated Biphenyl in Simulative Capacitor Oil with the Presence of NaOH, Hydrogen Donor and Catalyst

The obsolete polychlorobiphenyls (PCBs)-containing capacitors could cause serious hazard to environment and human health. Microwave irradiation was adopted to decompose 2,2',5,6'-tetrachlorobiphenyl (PCB53) dissolved in cetane (to simulate capacitor oil) in alkaline environment, where cetane acted as both reaction medium and hydrogen donor. The effect of another hydrogen donor, sodium hypophosphite (NaH₂PO₂), was also investigated. Granular activated carbon (GAC) or copper/iron-loaded GAC was added as microwave absorbing material to raise the reaction temperature, and on the other hand as catalyst to promote the dechlorination process. The results indicated that PCB53 in cetane could be decomposed efficiently by microwave irradiation with the presence of NaOH, hydrogen donor, and catalyst. NaH₂PO₂ was shown to be a more effective hydrogen donor than cetane. The copper-loaded or iron-loaded GAC had better catalysis effect than fresh GAC, while these two catalysts had similar effects. Microwave output power was very important, and the treatment under the condition of a higher microwave power for a short time was more effective than that of a lower microwave power for a long time. Higher degradation efficiencies were obtained when NaOH was added in aqueous solution instead of as particles.