【作者】 秦振林；

【导师】 全燮；

【作者基本信息】 大连理工大学 ， 环境工程， 2008， 硕士

【摘要】 近年来,电还原法处理氯代有机物,因脱氯效率高、操作简便、环境友好等优点,引起了研究者的广泛重视。本论文制备了负载有金属钯催化剂的碳纳米管阵列作为电极用于电催化还原脱氯处理水中难降解的多氯联苯,以降低其生物毒性和提高可生化降解性。主要开展了以下几方面的工作:采用化学气相沉积法在金属钛基底上制备有序阵列碳纳米管电极并对其进行纯化,考察了沉积温度、催化剂前驱体(二茂铁)浓度和沉积时间对电极形貌的影响。通过扫描电镜(SEM)和透射电镜(TEM)分析表明,在沉积温度为800℃,二茂铁浓度为24mg/mL,沉积时间为5min的条件下制备的碳纳米管在钛基底上致密均匀生长,阵列性良好,长度适中,外径约为80nm,内径约为15nm。纯化后电极形貌未受到破坏,性能得到改善。采用恒电流电沉积法在有序阵列碳纳米管电极上负载钯催化剂,考察了电流密度和沉积时间对电极形貌和性能的影响,通过透射电镜观察发现在电流密度为1.0mA/cm~2、沉积时间为10min时,催化剂颗粒的数量适中,分散均匀,平均粒径约为10nm。对电极进行X-射线衍射(XRD)和能量分散X-射线(EDX)分析证实了钯在电极上的存在。循环伏安分析表明了载钯阵列碳纳米管(Pd/CNTs/Ti)电极优良的电化学性能。将用上述方法制备的Pd/CNTs/Ti电极用于对目标物2,4,5-三氯联苯(PCB29)进行电催化还原脱氯降解,考察了电极的制备条件,支持电解质的种类和浓度,工作电压和PCB29初始浓度对降解效果的影响。研究表明,在0.05mol/L硫酸作支持电解质、工作电压为-1.0V时,Pd/CNTs/Ti电极对初始浓度为20mg/L的PCB29电解6h的降解率能达到90%,优于载钯的石墨(Pd/Graphite)电极和钛(Pd/Ti)电极。对降解产物进行定性分析发现降解过程中有一氯联苯、二氯联苯和联苯生成,同时溶液中的氯离子浓度也随着降解的进行逐渐增大,证实了电还原脱氯反应的发生。总之,本研究用较简单的方法制备出了载钯阵列碳纳米管电极,优化了电极制备条件,考察了该电极在适宜条件下对多氯联苯的电还原脱氯降解效果,并对降解产物进行了定性分析,为电催化还原法处理水溶液中多氯联苯的实际应用提供了理论基础和实验依据。更多还原

【Abstract】 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.更多还原