Degradation of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) by dielectric barrier discharge (DBD) non-thermal plasma: Degradation mechanism and toxicity evaluation

Polychlorinated biphenyls (PCBs) are a kind of persistent organic pollutants (POPs) with stable chemical properties which can be enriched in a biological body for a long time. They are often carelessly released into natural environment and thus constantly posing a potential threat to human health. However, because of lack of effective ways of degrading PCBs, researchers are still striving to explore new approaches to remove them from the environment. In this work, we employed atmospheric-pressure non-thermal dielectric barrier discharge (DBD) plasma to treat 3,3',4,4'-tetrachlorobiphenyl (PCB77) in aqueous solution and investigated the removal efficiency under different DBD conditions using different discharging gases. As a result, we showed that He-DBD had the highest removal efficiency with hydroxyl radical playing the major role in the degradation, while O2-DBD also gave rise to relatively high efficiency with ozone making an important contribution. After 2 min of treatments by He-DBD and O2-DBD, over 75% of PCB77 was degraded with removal rate of 23.65 mg/L and 22.19 mg/L per minute, respectively. Besides, the toxicological evaluation for the DBD treatment was also provided, confirming that the PCB77 degradation products had negligible biotoxicity. This work therefore provides a new effective approach to treatment of persistent organic pollutants (POPs) in the environment.