Immobilized Pd/Fe Bimetallic Catalyst And Palladium Modified Foam Electrode For Dechloridation Of Chlorinated Organic Compounds

The method of Pd/Fe bimetal reductive dechlorination for the removal of chlorinated organic compounds in water has received increasing interest in recent years. However, due to the two limitations of Pd/Fe nanoparticles: 1)hard to recycle resulting in secondary pollution; 2) easily agglomerate leading to decreased reactivity. To overcome the drawbacks of Pd/Fe bimetallic catalyst powder for dechlorination, Ni foam- immobilized Pd/Fe bimetallic catalyst was prepared via two-step method, and then its behavior of dechlorination for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated. Under the conditions of the inlet 2,4-D concentration of 20 mg L-1, Pd/Fe ratio of 0.1%, residence time of 782.6 min, initial pH value of 4.2 and temperature of 288 K, the 2,4-D conversion was 92% at steady-state, which can be last for more than 3 hours. Based on the analysis of experimental results, it was concluded that Ni foam-immobilized Pd/Fe bimetallic catalyst could retard the corrosion of Fe and prevent aggregation to be formed, which enable it to dechlorinate 2,4-D efficiently for a long time.Electrocatalytic hydrogenation (ECH) operation in continuous mode is preferable from a practical point of view and represents a significant step towards industrial implementation. In addition, A kinetic model for the electrochemical dechlorination of polychlorinated biphenyls (PCBs) will be an important contribution to the design and optimization of a continuous reactor. Initially, the electrocatalytic hydrodechlorination of 2-chlorobiphenyl (2-C1BP) to biphenyl at a palladium-modified nickel foam (Pd/Ni) cathode in a batch reactor was used as a model reaction for a quantitative study of the influences of the operating parameters, including temperature, the initial concentrations of PCBs, current density and the amount of Pd loading, on the apparent reaction rate. The dechlorination was found to follow pseudo first-order kinetics with respect to the 2-C1BP concentration. It was also found that a simple global power law rate equation, with Arrhenius dependency, can be used to describe the correlation between the pseudo first-order reaction rate constants and the reaction conditions. Subsequently, a mathematical model for predicting the performance of reductive dechlorination of 2-C1BP on Pd/Ni electrodes in a continuous stirred tank reactor was constructed, based on the batch-reaction kinetics. The suitability of the model was validated by performing experiments in and out of the range of reaction conditions applied in the batch reactor. The results show that the calculated values are a good fit to the experimental data.