Low-temperature decomposition of Aroclor 1254 over AC-supported Ni-Fe bimetallic catalysts: Kinetic and thermodynamic study

Abstract

Polychlorinated biphenyls (PCBs) cause serious impacts on the environment and organisms, due to their hypertoxicity, thermal stability and persistence. This study investigated the effects of temperature, reaction time and total flow rate on the low-temperature catalytic decomposition of Aroclor 1254. A modified iron-exchange method was adopted because it allows higher metal loading rates than the traditional impregnation method. We used this method to prepare three active carbon supported Fe/Ni bimetallic catalysts with different Fe/Ni molar ratios. The results indicated that the Fe/Ni bimetallic catalysts showed great potential in Aroclor 1254 decomposition. Among Fe/Ni molar ratios, Fe/Ni-1/3-C demonstrated the strongest performance with a decomposition efficiency greater than 90% even at the relatively low temperature of 200 °C. Thermodynamic analysis confirmed that the dechlorination of Aroclor 1254 over Fe/Ni-1/3-C obtained the minimum activation energy of 8.0 kJ/mol. Aroclor 1254 was decomposed rapidly over Fe/Ni-1/3-C, with a total decomposition efficiency of 83.4% at 10 min and 93.8% at 30 min. The kinetics analysis indicated a stepwise dechlorination of Aroclor 1254 over Fe/Ni-1/3-C. In addition, the total flow rate indicated a negative effect on the decomposition of Aroclor 1254 due to the decreased retention time.