Electrocatalytic Reductive Dechlorination Of Polychlorinated Biphenyls By Palladized Aligned Carbon Nanotubes Electrode

The electroreduction process has caused world-wide interest because of its high dechlorination efficicency,simple operation,and environmentally friendly property.In this dissertation,the palladized aligned carbon nanotubes(Pd/CNTs/Ti)electrode is fabricated for electrocatalytic dechlorination of polychlorinated biphenyls(PCBs).Well aligned carbon nanotubes are prepared by chemical vapor deposition on the Ti substrate and purified.The effects of deposited temperature,ferrocene concentration and deposited time on the morphology of CNTs are investigated.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)indicate that the well aligned CNTs have been successfully grow on the Ti surface,and the preparation conductions of deposited temperature,ferrocene concentration and deposited time are 800℃,24 mg/mL and 5 min,respectively.The external diameter of CNTs is about 80 nm while the inner is about 15 nm.After purification,the morphology of CNTs has not been destructed and the properties of the CNTs electrode could be improved.The constant current electrodeposition is used to load Pd onto the surface of the CNTs to synthesize the Pd/CNTs/Ti electrode.The effect of current density and depoited time on the morphology and property of the electrode are investigated.The TEM image indicates that Pd particles,whose average diameters are 10 nm,are dispersed uniformly on the surface of CNTs. The preparation conductions of current density and deposited time are 1.0 mA/cm² and 10 min,respectively.The X-ray diffraction(XRD)and energy-dispersive X-ray(EDX)have proven that the Pd has been loaded on the CNTs indeed.The excellent electrochemical property of the Pd/CNTs/Ti electrode is shown by the analysis of cyclic voltammetry.The electrocatalytic reductive dechlorination of the 2,4,5-trichlorobiphenyl is carried out using the palladized aligned carbon nanotubes.The effect of synthesized conditions of electrode,supporting electrolyte,working voltage and initial concentration of PCB29 on the dechlorinated degradation efficiencies are investigated.After 6 hours electrolysis with Pd/CNTs/Ti electrode,the degradation efficiency of PCB29 was up to 90%while the supporting electrolyte and working voltage were 0.05 mol/L H₂SO₄ and -1.0V,respectively. The performance of the Pd/CNTs/Ti electrode is better than the pallidum-loaded graphite and Ti electrodes.The monochlorobiphenyl,dichlorobiphenyl and biphenyl are detected by the qualitative analysis of the dechlorinated production.Meanwhile,the increasing of the concentration of chloride ion has confirmed in the process of electrocatalytic reductive dechlorination.In a word,the optimal conditions for the synthesis of Pd/CNTs/Ti electrode and electrocatalytic reductive dechlorination of PCB29 are investigated,and the dechlorinated productions are qualitatively analysis in this dissertation.The results will provide the theoretical and experimental basis for the application of electrocatalytic reduction using carbon electrodes in treatment of wastewater containing polychlorinated biphenyls.