Influence of activated-carbon-supported transition metals on the decomposition of polychlorobiphenyls. Part I: Catalytic decomposition and kinetic analysis

• Up to 350 °C, all the catalysts could decompose PCB-153 with an efficiency >94%.
• Reactivities with respect to PCB decomposition of: Ni > Cu > Zn > Fe.
• PCBs decomposed by absorption-reaction-desorption using LaTM-C.
• PCBs decomposed by reaction-desorption using IRTM-C.
• For ion-exchange-type catalysts, the activation energy order was Ni < Cu < Zn < Fe.

In this study, the synergism between activated carbon (AC) as a catalyst support and transition metals (TMs) is used to destroy low concentrations of PCBs. AC-supported TM catalysts were prepared according to two different methods: impregnation and ion exchange. Thermal reactions between 2,2′,4,4′,5,5’-hexachlorobiphenyl (PCB-153) and catalysts generated using AC-supported Ni or Cu ion exchange were conducted under a N2 atmosphere and resulted in a decomposition efficiency > 99.0%. Decomposition efficiency of PCB-153, the residual PCB-153 distribution, and the fingerprint characteristics of the decomposition products are investigated. Important findings include: (i) establishing a ranking of TM reactivities with respect to PCB decomposition of: Ni > Cu > Zn > Fe, (ii) PCB degradation reactions proceed via adsorption, reaction, and desorption, (iii) for ion-exchange-type catalysts, the activation energy order was IRNi-C < IRCu-C < IRZn-C < IRFe-C, which matches the order of the catalytic effects of the catalyst.