Investigation on Direct and Indirect Electrochemical Oxidation of Ammonia over Ru-Ir/TiO2 Anode
Investigation on Direct and Indirect Electrochemical Oxidation of Ammonia over Ru-Ir/TiO2 Anode
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DOI：
10.1021/ie503832t
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发表时间：
2015-02-11
影响因子：
4.2
通讯作者：
Nie, Yulun
中科院分区：
文献类型：
--
作者：
He, Shilong;Huang, Qing;Nie, Yulun
以商品RuIr/TiO2为阳极，在连续电化学四边形反应器中进行了中性pH条件下氨的电化学氧化。在反应器中填充活性炭以防止短路和提高电效率，可以有效地强化直接电氧化。活性游离氯引起的间接氧化对氨氮去除的贡献随氯离子浓度的增加而增加。此外，还详细研究了进水流速、盐度和电流密度对氨氮去除率的影响。根据CV扫描和COD去除结果，直接和间接氧化都参与了氨的去除。结果表明，直接氧化法对氨氮的去除速率低于对COD的去除速率，而间接氧化法对氨氮的去除速率高于对COD的去除速率。氨既可以被（OH）-O-中心点自由基氧化，也可以被活性自由氯氧化，COD的去除仅来自于（OH）-O-中心点自由基的氧化。在最佳条件下（pH = 6.5，I = 0.9 A，Na_2SO_4浓度为2%，Cl-浓度为1500 mg/L，进水流速为0.8 L/h），PAC填料床反应器可去除80%的氨氮，并主要转化为N_2。因此，Ru-Ir/TiO2基PAC填料床反应器为高氯离子浓度氨氮废水的处理提供了一种新的选择。
Commercial RuIr/TiO2 was used as the anode for electrochemical oxidation of ammonia at neutral pH in a continuous electrochemical quadrangular reactor. The reactor was packed with PAC to avoid short circuit and enhance electric efficiency, which could efficiently enhance the direct eletrooxidation. The contribution of indirect oxidation caused by active free chlorine to ammonia removal increased with the increase of chloride concentration. Moreover, the effects of inlet velocity, salinity, and current density on ammonia removal were also investigated in detail. On the basis of the CV scan and COD removal results, both direct and indirect oxidations were involved in ammonia removal. The results indicated that ammonia removal by direct oxidation occurs at a slower rate than that of COD, while indirect oxidation prefers removal of ammonia than that of COD. Ammonia could be oxidized by either (OH)-O-center dot radicals or active free chlorine, and the removal of COD only comes from the oxidation by (OH)-O-center dot radicals. Eighty percent of ammonia could be removed and mainly transferred to N-2 in a PAC packed bed reactor under optimum conditions (pH = 6.5, I = 0.9 A, 2% Na2SO4, Cl- = 1500 mg/L, and inlet velocity = 0.8 L/h). Hence, the Ru-Ir/TiO2-based PAC packed bed reactor provides an alternative for treatment of ammonia wastewater with high chloride concentration.