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Electrochemical oxidation of ammonia nitrogen in simulated wastewater by Bi-doped PbO₂ electrode

摘要：本实验采用钛网作为基体,利用电沉积方法制备了纯PbO₂电极和Bi-PbO₂电极,通过SEM、XRD、XPS对电极的表面形态进行了表征,利用循环伏安法对Bi-PbO₂电极电化学特性进行了研究.同时,以氨氮模拟废水作为研究对象,考察了Bi-PbO₂电极的电催化活性,探讨了氨氮电化学氧化降解机理.结果表明,Bi-PbO₂电极的形态表征、电催化活性明显高于纯PbO₂电极,氨氮的去除效率随电流密度的增加而提高,碱性条件下氨氮的去除效果明显好于酸性条件,适量浓度的Cl^-的引入在碱性条件下提高了氨氮的去除效果.当氨氮初始浓度为50 mg·L^-1、电流密度为40 mA·cm^-2、pH=12、Cl^-浓度为600 mg·L^-1时,电解120 min后,氨氮100%去除.氨氮的降解机理为:体系中无添加氯离子,酸性条件下氨氮主要是通过间接氧化去除,碱性条件下通过直接电氧化和间接氧化共同完成;体系中添加氯离子,氨氮的去除主要是通过溶液中生成的有效氯间接氧化去除.

Abstract：Bi-doped PbO₂ electrode and pure PbO₂ electrode were prepared by electrodeposition based on Ti substrate and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS) and cyclic voltammetry. The prepared electrodes for electro-oxidation degradation of ammonia nitrogen in simulated wastewater were systematically investigated. It was indicated that the Bi-doped PbO₂ electrode had excellent microstructure as well as excellent electrochemical properties than pure PbO₂ electrode. The removal efficiency of ammonia nitrogen was improved with increasing current density and the effect was better on the condition of alkaline than acid. Moreover, an appropriate concentration of chloride ion could favor removal of ammonia nitrogen under the condition of alkaline. The removal efficiency of ammonia nitrogen could reach up to 100% after electrolysis for 120 minutes at initial concentration of ammonia nitrogen of 50 mg·L^-1, the current density of 40 mA·cm^-2, pH of 12 and chloride ion concentration of 600 mg·L^-1. The electrochemical oxidation of ammonia nitrogen was removed through indirect oxidation under acidic condition and direct electro oxidation jointly with indirect oxidation under alkaline condition when chloride ion was absented, and mainly through indirect oxidation by active chlorine generated in the solution when chloride ion was present.