Electrocatalytic Reductive Dehalogenation Of Polychlorinated Biphenyls And Polybrominated Diphenyl Ethers By Modified Carbon Nanotubes Electrode

With the development of industry,environmental pollution by polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers(PBDEs) has become a matter of concern due to their increasing levels in the environment however,few studies have been reported in China. Therefore,platinum-loaded carbonnanotubes electrode(Pt/CNTs/Ti) and pallidum-loaded carbon nanotubes electrodes(Pd/CNTs/Ti) are employed in this study for electrocatalytic dehalogenation of PCBs and PBDEs,respectively.The carbon nanotube(CNTs) grew directly on Ti substrate by chemical vapor deposition (CVD),and Pt nanoparticles and Pd nanoparticles were loaded on CNTs with electrochemical deposition.The microstructure of the resulting was characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD) and energy-dispersive X-ray spectroscopy(EDX).The excellent electrochemical property of the modified carbon nanotubes electrode is proved by the analysis of cyclic voltammetry.The Pt/CNTs/Ti electrode was employed for electrocatalytic hydrodechlorination of 4-chlorobiphenyl(4-MCB).As a result,under the conditions that potential=-0.8V,pH=1 and room temperature,the degrade efficiency of 4-MCB was 80.4%with the Pt/CNTs/Ti electrode,which is better than Pt/Graphite electrode.The electrocatalytic reductive debromination of the 2,2',4,4'-tetrabromo diphenyl ether (BDE47) is carded out using the Pd/CNTs/Ti electrode.The effect of synthesized conditions of electrode,supporting electrolyte and working voltage on the dechlorinated degradation efficiencies were investigated.After 6 hours electrolysis with Pd/CNTs/Ti electrode,the degradation efficiency of BDE47 was up to 94%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(Pd/Graphite) and Ti electrodes(Pd/Ti). The tribromodiphenyl ether dichlorobiphenyl,monobromodiphenyl eher and biphenyl ether were detected by the qualitative analysis of the debrominated production.This confirmed the process of electrocatalytic reductive debromination. In a word,the optimal conditions for the synthesis of noble metal modified carbon nanotube electrode and electrocatalytic reductive dehalogenation of PCBs and PBDEs were investigated and the dehalogenation productions were qualitative analyzed in this dissertation. Compared with other plate electrode,Carbon nanotube electrode obtains better results.The results will provide the theoretical and experimental basis for the application of electrocatalytic reduction using carbon electrodes in treatment of wastewater containing typical persistent organic PCBs and PBDEs.